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A study of the manufacturing method and related mechanical properties of SiC reinforced aluminum Wiskel, J. Barry 1986

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A STUDY OF THE MANUFACTURING  METHOD AND RELATED MECHANICAL  PROPERTIES OF S i C REINFORCED ALUMINUM By J.Barry B.Sc.  The U n i v e r s i t y o f A l b e r t a , 1984  A Thesis of  Wiskel  Submitted  in Partial  the Requirements  Fulfillment  f o r t h e Degree of  Masters of A p p l i e d  Science  in The  F a c u l t y of Graduate  (Department  We a c c e p t  of M e t a l l u r g i c a l  this  thesis  as  Studies Engineering)  conforming  to ^he/irequ/ired standard  The  U n i v e r s i t y of B r i t i s h September (c)  Columbia  1986  J . BARRY WISKEL, 1986  In p r e s e n t i n g  this  requirements  f o r an  of  British  it  freely  agree for  available  that  in partial  Library  shall  for reference  and  study.  I  for extensive  that  financial  h i s or  her  copying or  gain  be  shall  copying of  g r a n t e d by  the  not  be  of  make  further this  thesis  head o f  representatives. publication  the  University  the  s c h o l a r l y p u r p o s e s may  understood  the  I agree that  permission  by  f u l f i l m e n t of  advanced degree a t  Columbia,  department or  for  thesis  It is  this  thesis  a l l o w e d w i t h o u t my  written  permission.  Department o f  \  ^ C Z ^ ' ° < U ^ ^ c ^ i r.ra_\  The U n i v e r s i t y o f B r i t i s h 1956 Main Mall V a n c o u v e r , Canada V6T  DE-6  (3/81)  1Y3  Columbia  my  £no^^ep^  11  ABSTRACT  A study conducted  manufacturing  to elucidate  reinforced failure  involving  the mechanical  aluminum. A r e a s  mechanisms,  A well  analyzed  tensile  dispersed fibre  behaviour  intermingling  of f i b r e s  increase  can lead  composite  to incomplete  expected  from  incurred  during manufacturing on t h e f i b r e  anomaly. A l s o , lead  of m i x t u r e s  fibre/(matrix  of f i b r e s  was o b s e r v e d .  formation  fibre  tensile  (ROM) v a l u e . F i b r e  that  damage  and by t h e f o r m a t i o n o f aluminum  plastic failure  causes  for this  deformation) especially  good b o n d i n g  i n t e r a c t i o n can  a t t h e low volume  This adhesion  between  the f i b r e and  was a t t r i b u t e d  s t r e n g t h e n i n g of the matrix samples.  distribution  behaviour.  were below  o f aluminum c a r b i d e a t t h e f i b r e / m a t r i x  Synergistic several  tested  being analyzed.  On a m i c r o s c o p i c l e v e l matrix  u t i l i z a t i o n and  t o d e l a m i n a t i o n damage.  surface are possible  t o premature composite  fractions  composite  the h i g h degree of  fibre  The s t r e n g t h o f t h e c o m p o s i t e s  carbide  bonding.  i n t h e a s - r e c e i v e d t o w s . The p o o r  susceptibility  a rule  p r o d u c t i o n methods,  i n the as c a s t  from  was  of a S i C f i b r e  and i n t e r f a c i a l  distribution  to obtain. This arises  testing  properties  included  was d i f f i c u l t  distribution  and t e n s i l e  to the interface.  was o b s e r v e d f o r  T h i s phenomena may be a t t r i b u t e d t o  altering  t h e aluminum m a t r i x  deformation  •  •  1X1  TABLE OF CONTENTS PAGE ABSTRACT  i i  TABLE OF CONTENTS  i i i  L I S T OF FIGURES  v  L I S T OF TABLES  viii  ACKNOWLEDGEMENTS  ix  CHAPTER  1.0  INTRODUCTION: METAL MATRIX COMPOSITES  . ..  1  CHAPTER 2.0 LITERATURE REVIEW  9  2.1 Nicalon SiC Fibres 2.2 S i C R e i n f o r c e d Aluminum C o m p o s i t e s 2.2.1 M a n u f a c t u r i n g Methods 2.2.2 Mechanical Properties 2.2.3 Interfacial Properties  9 14 14 17 23  CHAPTER 3.0 COMPOSITE PRODUCTION 3.1 3.2 3.3 3.4  29  D i e d e s i g n and M a n u f a c t u r i n g Temperature C o n t r o l L a y Up P r e p a r a t i o n Manufacturing D i f f i c u l t i e s  ....  29 39 44 48  CHAPTER 4.0 EXPERIMENTAL APPARATUS AND TECHNIQUE 4.1 4.2 4.3 4.4 4.5  Tensile Testing Volume F r a c t i o n D e t e r m i n a t i o n Microstructural Analysis D i f f r a c t i o n A n a l y s i s of F i b r e - M a t r i x Interface Heat T r e a t m e n t s  49 49 58 59 59 64  CHAPTER 5.0 EXPERIMENTAL RESULTS 5.1  T e n s i l e Test  65 Data  65  t  iv  5.1.1  As C a s t and Heat T r e a t e d Aluminum R e f e r e n c e Samples 5.1.2 Composite T e n s i l e P r o p e r t i e s 5.1.3 Ultimate Tensile Strength 5.1.4 R u l e o f M i x t u r e s (ROM) S t r e n g t h 5.1.5 Fibres Contributing 5.1.6 Fibre Strength 5.1.7 T e n s i l e Sample A n o m a l i e s 5.2 Microstructural Analysis 5.3 Interfacial Analysis  CHAPTER  65 68 69 69 72 80 81 85 88  6.0  DISCUSSION  97  6.1 Manufacturing Technique 6.1.1 Fibre Distribution 6.1.2 Volume F r a c t i o n 6.2 F a i l u r e Mechanisms 6.3 Tensile Results 6.4 I n t r i n s i c Strengthening 6.5 Fibre Strength 6.6 Interfacial Properties  97 97 100 101 105 107 112 112  CONCLUSIONS  114  RECOMMENDATIONS  115  REFERENCES  116  APPENDIX A  THERMODYNAMIC CALCULATIONS FOR THE FORMATION OF ALUMINUM CARBIDE IN SOLID ALUMINUM  119  APPENDIX B  DRUMWINDING PARAMETERS  121  APPENDIX C  T E N S I L E DATA  123  APPENDIX D  ELECTRON DIFFRACTION PATTERNS  128  V  L I S T OF Figure  2.1  Probabilistic ( r e f . 8)  FIGURES  Strength  of  SiC  Fibres 11  Figure  2.2  S i C / A l Composite T e n s i l e Data  Figure  2.3  F r e e E n e r g y of Aluminum C a r b i d e F o r m a t i o n i n L i q u i d Aluminum f o r V a r i o u s A c t i v i t i e s of S i l i c o n ( r e f . 21 )  25  F r e e E n e r g y of Aluminum C a r b i d e F o r m a t i o n i n S o l i d Aluminum f o r V a r i o u s A c t i v i t i e s of S i l i c o n  26  W e t t i n g of S i C C r y s t a l s by L i q u i d Aluminum a s a F u n c t i o n of T e m p e r a t u r e ( r e f . 7)  30  Figure  Figure  Figure  2.4  3.1  3.2  Schematic  Cross-Section  of  ( r e f . 10)  20  Pressing  System  33  Figure  3.3  Lower D i e  Plunger  34  Figure  3.4  Upper D i e  Plunger  35  Figure  3.5  Outer Die  Ring  Figure  3.6  Time-Temperature P r o f i l e Run  and  F i b r e f r a x Tube of  37  Manufacturing  43  41  Figure  3.7  Melting  and  Figure  3.8  Figure  4.1  R e t e n t i o n Time of Aluminum Through T h i c k n e s s Tensile  Solidification  Sample "Dog  Fibres  Temperatures  42  i n Molten 43  Reduced Cross  Section  ( r e f . 1.0)  50  Figure  4.2  Curved  Bone" T e n s i l e Sample  50  Figure  4.3  T e n s i l e Sample L a b e l l i n g  52  Figure  4.4  Grinding  53  Figure  4.5  Specialty Vise  Wheel For  Holding  Tensile  Sample W h i l e M a k i n g R e d u c e d C r o s s  Section  Figure  4.6  Wheatstone B r i d g e  Configuration  Figure Figure  5.1 4.7  C o m p a r i s o n of R e f e r e n c e Aluminum (43A) T e n s i l e D a t a A c q u i s i t i o n System and F i b r e R e i n f o r c e d Aluminum (46A)  54 56 57 66  vi  Figure Figure Figure Figure Figure Figure  5.2 5.3 5.4 5.5 5.6 5.7  Composite S t r e n g t h v s F i b r e Fraction  Volume 73  UTS/ROM R a t i o v s F i b r e Volume F r a c t i o n f o r As C a s t S p e c i m e n s  75  UTS/ROM R a t i o v s F i b r e Volume F r a c t i o n f o r A n n e a l e d and Tempered Specimen  76  UTS/ROM R a t i o v s F r a c t i o n o f F i b r e s Contributing  79  Apparent F i b r e Strength vs F i b r e Fraction  82  Comparison of S t r e s s - S t r a i n  Volume  Curve f o r  Sample 45A a n d 44D  83  Figure  5.8  F a i l u r e Modes o f S a m p l e 45A a n d 38C  86  Figure  5.9  As C a s t M i c r o s t r u c t u r e o f S a m p l e 42  87  Figure  5.10  A s C a s t M i c r o s t r u c t u r e o f S a m p l e 47  87  Figure  5.11  Grain  89  Figure  5.12  F r a c t u r e S u r f a c e o f S p e c i m e n 31E  90  Figure  5.13  F r a c t u r e S u r f a c e o f S p e c i m e n 44D  90  Figure  5.14  Diffraction  91  Figure  5.15  F i b r e S u r f a c e o f Sample B  Figure  5.16  S t e p p e d F r a c t u r e S u r f a c e o f 44b a n d 38C . 96  Figure  5.17  F r a c t u r e S u r f a c e o f 45A  Figure  6.1  T r a n s v e r s e C r o s s S e c t i o n o f S a m p l e 46A .. 98  Figure  6.2  Figure  6.3  Transverse Composite Cross (ref.16) Transverse Composite Cross  S t r u c t u r e o f Sample 47  P a t t e r n o f Sample B  95  96  Section 99 Section  (ref.10)  99  Figure  6.4  T r a n s v e r s e C r o s s S e c t i o n o f S a m p l e 44B ..102  Figure  6.5  Schematic  Figure Figure  6.6 6.7  H y p o t h e t i c a l Shear Loading Diagram 104 T r a n s v e r s e C r o s s S e c t i o n o f S a m p l e 45A ..106  o f Sample 44B C r o s s S e c t i o n  ...102  vii  F i g u r e 6.8  Schematic  o f Sample 45A C r o s s S e c t i o n  ...106  viii  L I S T OF  TABLES  Table  1.1  Properties  Table  1.2  Specific  Material  Properties  4  Table  1.3  Material  Fracture  Toughness  5  Table  2.1  Mechanical Properties Composites  Table  2.2  SiC/Al  of R e i n f o r c i n g  Composite  Specialty  of  Fibres  2  SiC/Al 18  Properties  - Avco  Products  22  Table  3.1  Pre-Composite  Table  4.1  Volume F r a c t i o n  Comparison  60  Table  4.2  Microstructural  Etchants  61  Table  4.3  Selected  Table  5.1  As  Cast  S t a c k i n g Sequence  Area D i f f r a c t i o n and  Heat  Treated  Conditions  46  ...  Aluminum  R e f e r e n c e Samples Cast  63  67  Table  5.2  As  Composite T e n s i l e  Table  5.3  Annealed Composite T e n s i l e  Table  5.4  72  Table  5.5  Quenched and Tempered C o m p o s i t e T e n s i l e Properties Y i e l d S t r a i n s of Aluminum M a t r i x Material  84  Table  5.6  Fibre  Surface D i f f r a c t i o n  Table  B.1  Drumwinding  Table  C.1  Aluminum R e f e r e n c e  Properties Properties  Patterns  Parameters Sample  ...  70  ..  71  92 122  Tensile  Properties  124  Table  C.2  Composite T e n s i l e  Table  C.3  Apparent  Table  D.1  Diffraction  Fibre  Properties  Strength  Patterns  125 127 129  ix  ACKNOWLEDGEMENTS  I wish A. the  t o thank D r . J . Nadeau, D r . E . T e g h t s o o n i a n  Poursartip past  fortheir  two y e a r s .  respective  Also,  sincere  contributions thanks  members o f t h e C o m p o s i t e G r o u p f o r t h e i r A personal  n o t e o f t h a n k s t o my f a m i l y  Bruno) f o r t h e i r enduring the  great  the various  office.  support  (Stan,  a n d t o my p e e r s  thesis paraphernalia  rendered  i s extended patience  and D r . over  toa l l  and a s s i s t a n c e .  Sandy B r u c e and i n room 406 f o r  collected  i n and a r o u n d  1  CHAPTER  1.0  INTRODUCTION; METAL MATRIX  COMPOSITES  T h r o u g h o u t h i s t o r y a s man a n d h i s w o r l d increasingly with  higher  s o p h i s t i c a t e d , t h e need f o r more a d v a n c e d strength,  concurrently.  s t i f f n e s s and d u r a b i l i t y  A specific  still  maintaining  meet t h i s c h a l l e n g e  o r more c o n s t i t u e n t s  properties  acceptable  s t i f f n e s s and s t r e n g t h .  To  as a combination of  s y n t h e t i c a l l y assembled r e f l e c t i n g the  c o n s i s t of a polymer  composite m a t e r i a l s  matrix  f i b r e s such as g l a s s , g r a p h i t e  1 . 1 ) . Due t o t h e p r e s e n c e o f t h e s e f i b r e s , e x h i b i t high  specific  strength  1.2). S p e c i f i c p r o p e r t i e s a r e d e f i n e d  strength  weight  o f t h e i n d i v i d u a l c o m p o n e n t s a d v a n t a g e o u s l y . Common  r e i n f o r c e d by s t r o n g  (Table  i s t o minimize  are best described  types of composite m a t e r i a l s  (Table  has r i s e n  a c o m p o s i t e m a t e r i a l was p r o d u c e d .  Composite m a t e r i a l s two  materials  example c o n c e r n s t h e a i r c r a f t / a e r o s p a c e  i n d u s t r y where t h e o b j e c t i v e o f d e s i g n e r s while  h a v e become  or kevlar  polymer and s t i f f n e s s  as the observed  a n d s t i f f n e s s d i v i d e d by t h e m a t e r i a l s  density.  Thus,  c o m p o s i t e s a r e s u i t a b l e i n a p p l i c a t i o n s where o v e r a l l component weight  i s a p r i m a r y c o n c e r n w h e t h e r i t be an a i r c r a f t  tennis  racquet or automobile e x t e r i o r .  part,  2  TABLE Properties  FIBRE  MODULUS (GPA)  of  1.1  Reinforcing  UTS (MPA)  Fibres  DENSITY (g/cm )  (ref.l)  E/P  UTS/P  3  85. 5  2100  2.54  28.5  Graphite  390. 0  2100  1.90  205.0  1100  Kevlar  130. 0  2800  1.50  87.0  1870  Boron  385. 0  2800  2.63  146.0  1100  SiC(Nip.)  200. 0  2000  2.6  76.9  770  SiC(Avco)  427. 0  3447  3.0  142.3  1149  S-Glass  830  3 To  emphasis the  advantages of  composites,  comparison  with comparable m a t e r i a l s  summarizes  the  steel,  titanium,  it  i s obvious  or  exceed An  that  specific  aluminum and  that  the  those c i t e d important  they are  properties  f o r the  feature  orthotropic  advantageous p r o p e r t i e s specific  properties in a  laminate  are  on  use  under m u l t i  the  The  other  which t h e i r  hand  It  was  possessing exhibits use  of  itself.  composites  composite m a t e r i a l s  are  directionality specific  cited  implies  predominant  of  the  fibre  o r i e n t a t i o n s of  to the  loading). thus are  each  Metals  of  more  conditions.  a p p l i c a t i o n s . However, t h e r e  are  conditions  i s l i m i t e d . In  use that  at  above 200  toughness values  respectable  i n composite  be  used  in a in  p a r t i c u l a r , high  polymer matrix m a t e r i a l s  even w i t h  the  mechanical  can  the  is  in  1.2  of  meet  that  in Table  their  stated  (ref.  °c.  i n d i v i d u a l components  (Table  1.3)  fracture resistance.  a tougher matrix m a t e r i a l  increase  the  table  listed.  d i r e c t i o n a l loading  observed low  of  i s o t r o p i c i n n a t u r e and  usefulness  precludes  From t h i s  (eg.0,90,+-45 d e g r e e s  temperature degradation 1,2)  materials.  a composite  composite m a t e r i a l s  wide v a r i e t y of  composites,  properties  the  1.2  laminated  in nature. Orthotropic  r e s u l t s from the  ply  of  metals  of  of  d i r e c t i o n s . The  i s needed. T a b l e  polymer  specific  a direct  (eg.  In  composite light  aluminum) may  f r a c t u r e t o u g h n e s s above t h a t  of  materials this  fact,  result in of  the  an  metal  4  TABLE SPECIFIC  Material  MATERIAL  Volume Fraction  1.2  PROPERTIES ( r e f .  E (Gpa)  uts (Mpa)  density (g/cm )  1,  2)  E/p  Uts/p  3  Glass/epoxy (0/90/+-45)  60%  17.2  330  1.85  9.3  178  Kevlar/epoxy (0/90)  60%  40.0  650  1.4  29  460  Carbon/epoxy (0/90)  58%  83.0  380  1.54  53.5  240  Titanium (6-AL 4-V)  -  115.8  992  4.54  25.5  218  Steel (4320)  -  210.0  800  7.8  26.9  103  Aluminum (6061-T6)  -  70.0  310  2.7  25.9  115  Derakane (polyester)  -  3.4  79  1.2  2.8  66  Epoxy  -  3.4  102  1.2  2.8  85  5  TABLE MATERIAL  Material  FRACTURE  1.3  TOUGHNESS  (ref .  2)  KIC MPA(m*.5)  ALUMINUM(2024-T6) TITANIUM(6A1-4V)  80.2 215  B-SiC  3.38  EP0XY(F185-Hexcel)  3.69  GRAPHITE-EPOXY (0/+-45/90)  24.2  s  6  Polymer  c o m p o s i t e m a t e r i a l s h a v e been o b s e r v e d t o f o l l o w a  r u l e o f m i x t u r e s (ROM) that  tensile  b e h a v i o r . The  ROM  behavior  the i n d i v i d u a l composite components c o n t r i b u t e  stiffness  i n proportion to their  states  strength  volume f r a c t i o n p r e s e n t i n the  m a t e r i a l . As t h e m a t r i x c o m p r i s e s up t o 50% o f t h e c o m p o s i t e mechanical shortcomings of i t r e l a t i v e are  quite One  (Table  1.2)  method o f i m p r o v i n g t h e m e c h a n i c a l p r o p e r t i e s o f a i s t o improve  the m a t r i x m a t e r i a l .  matrix with a metallic  alternative.  The  advantages  material  2) e n h a n c e d m a t e r i a l 3) i m p r o v e d matrix advantages  comparison  feasible include  properties  of  1.2)  o f a l u m i n u m and  t o polymer  t i t a n i u m at high temperature i n  matrix m a t e r i a l s are t h e i r  resistance  the  toughness  o p p o s e m a t e r i a l d e g r a d a t i o n a b o v e 200 temperature  is a  mechanical properties  (Table  Substituting  of a m e t a l m a t r i x  1) i m p r o v e d h i g h t e m p e r a t u r e  The  to the f i b r e  the  pronounced.  composite polymer  and  is attributed  °c.  The  ability  to  improved  t o the p r o t e c t i v e  oxide  layer both these metals possess. The  d i s a d v a n t a g e s of u t i l i z i n g a m e t a l as a m a t r i x m a t e r i a l  include: 1) i n c r e a s e d w e i g h t 2) d i f f i c u l t i e s In  comparison  cited  i n manufacturing  t o a polymer  have a s u b s t a n t i a l l y  T h i s would  :  material  ( d e n s i t y = 1.2)  greater specific  tend to minimize the weight  gravity  the  metals  (Table  s a v i n g advantage  1.2).  which i s  7  critical  i n the  importantly,  utilization  the  limiting  factor  widespread  fibre  processing  required during manufacturing.  Of has  matrix  i n the  continuous  discussed  metal  of a c o m p o s i t e m a t e r i a l . More  i n subsequent  the  many r e a s o n s  The  for this  as  2)  low  melting point  3)  economically  4)  excellent corrosion resistance  (2.7  is utilized.  The thesis  kg.)  material be  in  The  ($1.50 p e r  reinforcing  an  1.1).  below:  SiC  fibre  mechanical  aluminum m a t r i x  degradation  of  fibres  k e v l a r and  metal  material  d e a l t with  in  f o r the  SiC  utility  matrix  a d v a n t a g e s of  p r o p e r t i e s of fibres  this  an  a l u m i n u m as a  Thus, the  (epoxy  favourable.  (Nicalon) r e i n f o r c i n g  ceramic  Deterrents  2) h i g h c o s t of b o r o n  to a polymer  for choosing  cited.  f o r a more  i f a molten  composite  SiC  are  commercially  u s a g e of  other  fibres  include:  1) g r a p h i t e s e v e r e l y d e g r a d e d by  3)  are  kg.)  especially  matrix  to that for other (Table  listed  i s more e c o n o m i c a l l y  reasons  c o n s i d e r e d . The  available  m a t e r i a l . There  °c)  In c o m p a r i s o n  have been b r i e f l y  comparable  (660  design  metal  i s a continuous  aluminum  3  aluminum  particular  aluminum m a t r i x .  Steel),  m e l t i n g p o i n t of aluminum a l l o w s  technique  will  g/cm )  viable  manufacturing  = $9.00 p e r  This aspect  a p o s s i b l e matrix  density  low  complicated  ( A l , T i and  some of w h i c h a r e  practical  will  a l l u d e d to  1) low  relatively  i s the  of  chapters.  three metals  t h e most p o t e n t i a l  composites  use  m o l t e n aluminum  (ref.5)  (ref.6) g l a s s above 200  °c  (ref.l)  8  Two  types of S i C f i b r e s are l i s t e d  fibre  employed i n t h i s  Nicalon  SiC produced  thesis  i n Table  i s the commercially  by t h e N i p p o n  this  results  fibre  over  polymer  reinforced with a  i n i t s i n f a n c y . One  reason f o r  from the p r o p r i e t a r y  n a t u r e of c o m p o s i t e  material  matrix composites Metallurgical  are r e l a t i v e l y  new  by  i n d u s t r y . As  metal  t o the Department of  E n g i n e e r i n g a t U.B.C. t h e e x t e n t o f r e s e a r c h on  continuous SiC  (Nicalon) fibre  nature..The  r e i n f o r c e d a l u m i n u m was  areas studied  included:  1) m a n u f a c t u r i n g 2)  Japan.  is still  ( i n c l u d i n g metal matrix) research conducted  exploratory  t y p e of  available  advantages  r e s e a r c h and d e v e l o p m e n t o f a m e t a l  continuous ceramic  The  C o r p o r a t i o n of  Though m e t a l m a t r i c e s h a v e a p p a r e n t matrices,  1.1.  testing  3) c o m p o s i t e  mechanical  properties  of  an  9  CHAPTER 2.0 LITERATURE REVIEW  The dealing  literature  search  i s divided  i n t o two d i s t i n c t  parts  with:  1) N i c a l o n 2) S i C / A l Each s e c t i o n  SiC Fibres composites  includes  recent  d e v e l o p m e n t s on m a n u f a c t u r i n g a n d  related mechanical properties p e r t a i n i n g to e i t h e r the f i b r e s or fibre  r e i n f o r c e d aluminum r e s p e c t i v e l y .  2.1 N i c a l o n  SiC Fibres  Nicalon an  organic  multifilament  polymer  S i C tows a r e p r o d u c e d by p y r o l y s i s o f  i n t o an i n o r g a n i c  B-SiC f i b r e .  developed t o c a r r y out t h i s conversion  involves the  d e c h l o r i n a t i o n of d i c h l o r o m e t h y s i l a n e dimethylpolysilane.  This  produce p o l y c a r b o s i l a n e . distilled  t o produce  i s h e a t e d a t 470 °C f o r 8 h o u r s t o The p o l y c a r b o s i l a n e  i s t h e n vacuum  i n t o a s e r i e s o f p o l y m e r m o l e c u l e s . The m o l e c u l e s a r e  m e l t spun i n t o c o n t i n u o u s f i b r e s a n d a r e c u r e d crosslink 850  the organic  °C i n n i t r o g e n  crystallized  i n ozone t o  m o l e c u l e s . These f i b r e s a r e h e a t e d a t  t o f o r m amorphous S i C w h i c h i s t h e n  a t 1200 °C. A s - f a b r i c a t e d  b e t w e e n 10 t o 20 m i c r o n s i n d i a m e t e r length  The p r o c e s s  f i b r e s range i n s i z e  (ref.7) with a variable  ( f i b r e s u s e d i n t h e s i s were r e c e i v e d  m e t r e s ) . The d e n s i t y  of the i n d i v i d u a l f i b r e  comparison t o the d e n s i t y  from  of pure B-SiC  i n lengths  o f 500  i s 2.6 g/cm  3  in  ( 3 . 1 9 g / c m ) . The l o w e r 3  10 density  i s a result  composition  into  having  (2.0 g/cm ) a n d t h e r e m a i n d e r 3  The i n d i v i d u a l  fibres  As w i t h  other  brittle  materials  stresses corresponding  to a probability  Mpa  sensitivity Prewo for  strength  fibre  probability  the  diameter  of f a i l u r e .  do n o t failure  Figure  with  observed  failure  strength  the greater  equation  possessing  strength  corresponds  t o a 50%  in strength  with  increasing  of a l a r g e r flaw  size  the s t r e n g t h  was e m p e r i c a l l y  of N i c a l o n  lengths.  f i b r e s (11.9  From t h e s e  t e s t s the  derived:  = s t r e s s a t 50% p r o b a b i l i t y length  on  et a l (ref.9)  l n S ( 5 0 ) = 8.12 - 0.128 x l n ( L )  = fibre  a  o f 2.0  t e s t e d a l s o has a s u b s t a n t i a l e f f e c t  s t r e s s . Andersson  determined  s t r e s s o f 1600 Mpa  diameter.  m i c r o n mean d i a m e t e r ) f o r v a r i o u s  L  follows  l e n g t h and  fibre  i s p o s s i b l y the r e s u l t  failure  experimentally  S(50)  2.1  f r o m 300  stress  o f 40 m i c r o n s . F o r f i b r e s  The d e c r e a s e  l e n g t h of f i b r e  following  in failure  of 12.5 m i c r o n s an a v e r a g e  diameter  The  each.  can range  d e p e n d e n c e on d i a m e t e r ,  Gpa was o b s e r v e d . A v e r a g e  associated  combined  to flaws.  mean d i a m e t e r  fibre  B-SiC  of s u r v i v a l .  of the f i b r e  ( r e f . 8 ) r e p o r t s an a v e r a g e  a mean  crystalline  but r a t h e r , a range of  t o 3800 Mpa. The l a r g e d i s t r i b u t i o n  from a f i b r e s  10%  the SiC f i b r e s  strength;  the strength  3  500 f i b r e s  possess a well defined  shows t h a t  (2.19 g / c m ) ,  produced are subsequently  tows c o n s i s t i n g o f a p p r o x i m a t e l y  (ref.8)  a multicomponent  c o n s i s t i n g o f 30% amorphous s i l i c a  amorphous c a r b o n (ref.7).  of the f i b r e s  in millimetres  ...2.1 of f a i l u r e  (Mpa)  11  4-  5 — n — i 1 2  5 10 20  i iiii i — r ~ i — n — 40  60  80 90 95 98 99  CUMULATIVE FAILURE PROBABILITY  FIG.  99 8  (%)  2.1 - P R O B A B I L I S T I C S T R E N G T H OF S I C F I B R E S  ( R E F . 8)  12 This equation proportional The  i s evidence that to  v a l u e s of  carefully  o c c u r due  strength  single  fibres.  Test r e s u l t s  f i b r e m i s h a n d l i n g . The  unknown, t h u s , i t can  o n l y be  incurred during handling w i l l Discussing  the  generalized  that  s t r e n g t h of  a  a tow  a l u m i n u m i s b e i n g a n a l y z e d and  not  an  f a c t o r s which would i n h i b i t a d i r e c t  fibre  d a t a p r e s e n t e d and  the  a aluminum m a t r i x are  1)  probabilistic  2)  effects  3)  fibre  In  l o a d i n g an  n a t u r e of  fibre  damage i n c u r r e d d u r i n g  breakage c o r r e s p o n d i n g to  relatively  low  s t r e s s can  be  stress as  low  l e v e l . As as  by  these broken f i b r e s  to  adjacent  would r e s u l t  fibres.  The  300 will  to  comparison between  the  t h e n be  fibre  SiC  follows: strength in  tow  manufacturing  weakest f i b r e  shown e a r l i e r The  by The  s t r e n g t h of  a  SiC/Al  fibre.  original  in Fig.  t h i s domino e f f e c t  occur at 2.1  l o a d once  transferred via  f a i l u r e and  individual  will  cumulative stress s h i f t e d  in additional  e x p e c t e d t h a t due  Mpa.  in a  encompassed  SiC/Al composite, the  SiC  p r o p e r t i e s of  individual  fibre  interaction  unidirectional  fibres  actual  as  single  anomaly e x i s t s  of  is  damage  ultimate tensile  of  Mpa  mishandling  fibre  the  al  550  degradation.  failure  of  to  in strength  w i t h i n a c o m p o s i t e m a t e r i a l . The  reinforcing  up  result  fibre  fibre  for  Andersson et  e x t e n t of  i s somewhat t r i v i a l when c o n s i d e r i n g  single  by  s t r e s s of  fibre  composite t h a t the  inversely  s t r e n g t h were d e t e r m i n e d  that a decrease in f a i l u r e to  is  length.  average f i b r e  handled  (ref.7) reveal can  fibre  fibre  so  on.  to  the  this carried aluminum  these It  a multifilament  a  fibres  is SiC  tow  13 will  have a s e e m i n g l y l o w e r a v e r a g e  measured f o r a comparable The  effect  intertwined It  f a i l u r e s t r e s s than  number o f i n d i v i d u a l  on f a i l u r e s t r e s s a s a r e s u l t  i n a tow h a v i n g a 0.1 mm^  that  fibres. o f 500  cross section  fibres i s unknown.  c a n o n l y be p r e s u m e d t h a t a b r a s i o n b e t w e e n f i b r e s w o u l d  s u f f i c i e n t damage t o d e c r e a s e t h e a v e r a g e  fibre  induce  s t r e n g t h i n each  tow. The  tensile  for c a r e f u l l y  tests, c i t e d  handled s i n g l e  r e d u c t i o n was o b s e r v e d of  by r e s e a r c h e r s i n t h e l i t e r a t u r e a r e f i b r e s . As s u b s t a n t i a l  f o r mishandled  fibres  (ref.7),  f i b r e damage i n c u r r e d d u r i n g t h e f a b r i c a t i o n  r e i n f o r c e d aluminum i s something  strength the extent  p r o c e s s o f an S i C  t o be c o n s i d e r e d . I t i s l i k e l y  t h a t d u r i n g a h o t p r e s s i n g o p e r a t i o n some f o r m o f f i b r e damage will  be i n d u c e d r e s u l t i n g  i n a strength  reduction.  F i b r e m o d u l u s was f o u n d t o h a v e a f a i r l y 200 (ref  +-  10 Gpa t e s t e d o v e r an a v e r a g e  c o n s i s t e n t value of  d i a m e t e r o f 12.0 m i c r o n s  9 ) . An a n o m a l y was r e p o r t e d i n t h e l i t e r a t u r e f o r f i b r e s  h a v i n g a diameter of 5 m i c r o n s . A modulus f o r t h e s e f i b r e s Gpa  was o b t a i n e d ( r e f . 7 ) .  attributed SiC)  agreed  T h e s e e x c e p t i o n a l l y h i g h v a l u e s c a n be  to a higher purity  and e r r o r s  o f 500  in testing  f i b r e being produced  such a f i n e  t h a t a m o d u l u s o f 200 +-  10  specimen.  ( i n terms of  I t i s generally  Gpa i s c o n s i d e r e d c o r r e c t  (ref.7,8,10,11). U n l i k e glass or kevlar  t h e N i c a l o n S i C was f o u n d t o p o s s e s s  e x c e l l e n t h i g h temperature p r o p e r t i e s . Kohara  (ref.12) observed  that the fibres maintained a r e l a t i v e l y consistent  s t i f f n e s s and  s t r e n g t h up t o 1200 °C. I t s h o u l d be n o t e d t h a t t h e s e h i g h  14 temperature  t e s t s were c a r r i e d o u t i n a r g o n  g a s . I t c o u l d be  p o s t u l a t e d t h a t t h e f o r m a t i o n of a p r o t e c t i v e o x i d e ) would m a i n t a i n f i b r e at  similar  2.2  integrity  Of more c o n c e r n the mechanical  of oxygen  Composites  t o t h e work c a r r i e d o u t i n t h i s t h e s i s a r e  properties cited  Discussed i n this  techniques employed, observed  for a unidirectional  section will mechanical  a s p e c t s of t h e S i C f i b r e aluminum 2.2.1  i n the presence  (silicon  temperatures.  S i C R e i n f o r c e d Aluminum  composite.  oxide f i l m  Manufacturing  SiC/Al  be t h e m a n u f a c t u r i n g p r o p e r t i e s and  certain  interface.  Methods  The p r e f e r r e d method o f m a n u f a c t u r i n g a l u m i n u m i s by a m o l t e n  Nicalon SiC reinforced  a l u m i n u m h o t p r e s s i n g t e c h n i q u e . The  r e a s o n i n g f o r the hot p r e s s i n g w i l l on d i e d e s i g n . T h e r e e x i s t  be d i s c u s s e d i n t h e c h a p t e r  s e v e r a l v a r i a t i o n s of the molten  hot  p r e s s i n g t e c h n i q u e t h a t have been a p p l i e d t o p r o d u c e a S i C / A l composite.  T h e s e methods w i l l  be d e s c r i b e d a s p r e c i s e l y  p o s s i b l e and t h e d i s a d v a n t a g e s / a d v a n t a g e s noted  that specific  manufacturing papers  details pertaining  stated.  as  I t s h o u l d be  to the various  t e c h n i q u e d e s c r i b e d were not p r e s e n t e d  i n the  referenced.  Tanaka e t a l ( r e f . 1 0 ) produced following  a S i C / A l composite  by t h e  method:  1) The S i C t o w s were drum wound i n t o s h e e t s u s i n g a vinlyester  binder.  2) L a y e r s o f S i C s h e e t s a n d 6061 a l u m i n u m d i s c s were  then  15 alternately 3) The  vessel  vessel  stacked was  was  pressed The  advantage  SiC/Al  at  19.6  Mpa  l a y up  Nakata  t o 720  temperature  i s the  simplicity  disadvantages  i s heated  placed poured.  i n a metal  The  the p r o c e d u r e . the  steel  500  °C  mould  with  and  them  forced  up  49.0  Mpa  this  i s then  detail  longitudinal  the the of  the  the  problems  associated  tows i n t h e c e n t r e p o r t i o n  external  s h e e t s . The then  steel steel  horizontally  aluminum  from  (800  °C) i s  applied. not  As given.  the c o m p l e x i t y  with winding  of  t h e tows  on  encountered.  t h e S i C tows o n t o  d i e . Molten  of t h e aluminum  inadequate  pressing  on mould d e s i g n was  the d i e a r e a . T h i s p r e s s i n g  Fukunga e t a l o b s e r v e d  an  and  mould d e s i g n would be  infiltration  a hot  immediately  method stem  i s p l a c e d i n t o a metal  into  into  i n t o which molten  Fukunaga e t a l ( r e f . 1 1 ) p o s i t i o n frame w h i c h  immediately  the temperature  d e s i g n and  f o r 30 m i n u t e s  Difficulties  frame and  of  although employing  et a l , s p e c i f i c  disadvantages  was  minutes.  available.  A p r e s s u r e of  w i t h Tanaka  The  f o r 10  recorded throughout  t o drum w i n d i n g at  °C.  are that  t e c h n i q u e m e c h a n i c a l l y wrap the S i C tows on  frame  vessel  minutes.  on v e s s e l  e t a l ( r e f 13)  frame as o p p o s e d  steel  furnace the v e s s e l  i s a p p a r e n t l y not  were not  heated  i s non-reusable  Further d e t a i l s  encountered  stainless  and  f o r 15  method  vessel  a  at t h i s  the  t e c h n i q u e . The  steel  procedure.  held  from  of t h i s  manufacturing stainless  evacuated  then  5) Upon r e m o v a l  inside  aluminum  a  support  i s then  a l l o w s f o r the i n t o the  fibre  tows.  aluminum p e n e t r a t i o n of  of the d i e . Other  disadvantages  the  16 i n c l u d e the e l a b o r a t e p r e s s i n g equipment  required,  p r o d u c e d a s a c y l i n d e r and p r o d u c t i o n i s l i m i t e d unidirectional  composites  to  reinforcement only.  G i g e r e n z e r e t a l ( r e f . 14) m a n u f a c t u r e d  unidirectional  r e i n f o r c e d a l u m i n u m by a h o t d r a w i n g p r o c e s s . A r o l l e r s y s t e m was  utilized  a l u m i n u m and into a  to p u l l  cylindrical  infiltration  d i e forms  b a r s t o c k c o m p o s i t e . The  t h i s p r o c e s s a r e 100 m i c r o n s with  fibre  utilized  i n diameter, therefore,  in  problems  o f a l u m i n u m i n b e t w e e n f i b r e s were n o t  u n d e r s t a n d a b l e t h a t aluminum p e n e t r a t i o n a problem with t h i s p r o c e s s . Composites drawing process are l i m i t e d  tows,  it is  i n t o the f i b r e s would produced  to unidirectional  A m o d i f i e d h o t p r e s s i n g m e t h o d was  be  by t h e h o t  configurations.  employed  by K o h a r a  et a l  t o the a c t u a l p r e s s i n g p r o c e d u r e a p r e f o r m of S i C  and a l u m i n u m powder was p r o d u c e d by i m m e r s i n g powder and s o d i u m  p r e p a r e d . The  i m p r e g n a t e d tow  the SiC f i l a m e n t s  in a slurry  a l g i n a t e s o l u t i o n . The  was  of aluminum  p r e p r e g g e d S i C was  i n t o s t r i p s and p l a c e d i n a g r a p h i t e d i e f o r s u b s e q u e n t h o t p r e s s i n g . The infiltration  molten  t h e drawn  fibres  e n c o u n t e r e d . As N i c a l o n S i C comes i n c o m p a c t e d  (ref.15). Prior  drive  t h e f i b r e s t h r o u g h a b a t h of  t h e n a c a s t i n g d i e . The  SiC  slurry  technique allows  i n t o the f i b r e  f i b r e s must s t i l l  t o w s . The  f o r improved  e l i m i n a t e v o i d s and c r e v i c e s to a s s e s s the q u a l i t y  liquid aluminum  disadvantage i s that  be h o t p r e s s e d i n t h e m o l t e n  state  i n t h e c o m p o s i t e . I t was  cut  the  i n order to difficult  o f c o m p o s i t e p r o d u c e d by K o h a r a e t a l as  m e c h a n i c a l p r o p e r t i e s were n o t p r o v i d e d . A d d i t i o n a l on t h e p r e s s i n g t e c h n i q u e was  not  available.  information  1 7  The varied  methods of m a n u f a c t u r i n g  i n n a t u r e . Each t e c h n i q u e ,  composite it.  One  adequately,  has  several  p r e d o m i n a n t drawback  required  with  t h i s method  process control  ( m o n i t o r i n g of  al  Kohara  ( r e f . 1 0 ) and  above a l s o  lack  the  a unidirectional i n most  2.2.2  a s s o c i a t e d with of  apparatus  exception The  temperature).  flexibility  d i e and  This factor  would  lack  of  E x c l u d i n g Tanaka  t h e methods  in producing  i s the  inherent  i s the non-reusable  et a l ( r e f . 1 5 ) ,  composite.  presented  anything tend  et  other  than  to l i m i t  their  applications.  tensile  determined  by  tensile  according  p r o p e r t i e s of u n i d i r e c t i o n a l  t o the matrix  strengths  of  90 Mpa  of  composites The range  1050  125  1100  specimens  t o g e t h e r . The  Mpa)  (annealed  were g r o u p e d s t r e n g t h of  aluminum a r e  respectively), 6061  i n the mechanical  aluminum. The  2.1  matrix  the type  .  of  tensile similar hence,  samples  (76  Mpa  their  (annealed  s e p a r a t e l y as were t h e 198  as  were c a t e g o r i z e d  5052  Mpa).  strengths reported in Table  of v a r i a b i l i t y  in Table  m a t e r i a l s s t r e n g t h because  aluminum and  f o r annealed  tensile  reinforced  composite  as t h e m a t r i x m a t e r i a l v a r i e d . The  v a l u e s are grouped strength  SiC composites,  various researchers, are presented  s t r e n g t h s of each  aluminum u s e d  and  p r o c e s s . An  a  Mechanical P r o p e r t i e s The  The  disadvantages  e m p l o y e d by T a n a k a e t a l ( r e f . 1 0 ) .  difficulties  use  though a b l e t o produce  i s the c o m p l e x i t y  f o r the m a n u f a c t u r i n g  technique  a s p r e s e n t e d above a r e q u i t e  2.1  indicate  p r o p e r t i e s of  highest f a i l u r e  stress  was  a wide  SiC cited  for a  18  TABLE 2.1 Mechanical  Volume Fraction (%)  Matrix Material  Properties  of S i C / A l  Composites  UTS (Mpa)  Tensile Specimen Thickness (mm)  Tempered UTS (Mpa)  Ref  34  1050  630  NA  -  16  35  pure A l  440  1.0  -  17  35  1100  861  1.2  40  pure A l  420  NA  -  11  41  1050 (wire)  673  NA  -  16  25  6061  690  1.2  25  6061  635  1.5  -  18  30  6061  630  1.5  -  18  35  6061  800  1.5  -  18  40  6061  700  1.5  -  18  42  6061  313  NA  -  16  50  6061  760  1.5  -  19  31  5052  251  NA  -  16  40  5052  781  1.2  836-0  680-O  784-0  10  10  10  19 35%  volume f r a c t i o n  Surprizingly, possessing lower  1100  aluminum m a t r i x  sample ( r e f . 1 0 ) .  specimens w i t h volume f r a c t i o n s e x c e e d i n g  a stronger matrix  ultimate tensile  the manufacturing  i n t o the  f r a c t i o n s of  fibres  o r 5052) e x h i b i t e d n o t a b l y  c u r r e n t l y i n use  fibre  tows d o e s n o t  adequate aluminum  occur  for high  encountered  in manufacturing  s t r e n g t h of t h e 42%-6061 and  manufacturing  processes results  were e m p l o y e d . The  for references  s u r p r i s i n g as the a u t h o u r s A major concern tensile  tests cited  the aluminum m a t r i x inconsistencies  10,  identical c o n s i s t e n c y of  18 and  of each paper a r e  inhibiting i s the  19  i s hot  t h e a b s o l u t e c o m p a r i s o n of  strengthening  from t e n s i l e  the  interconnected. the  c o n t r i b u t i o n provided  to the composites s t r e n g t h .  resulting  The  31%-5052 s p e c i m e n s a r e w e l l b e l o w  f o r a 34%~1050 s a m p l e t h o u g h  test  the  a S i C / A l composite.  that observed  tensile  volume  .  Kohyama e t a l ( r e f . 1 6 ) i s an e x c e l l e n t e x a m p l e o f variability  and  s t r e n g t h s . T h i s would i n d i c a t e t h a t f o r  techniques  infiltration  ( e g . 6061  35%  by  Secondly,  specimen c o n f i g u r a t i o n are  ignored. The  l a c k of  information provided  s t r e n g t h e n i n g a f f e c t of  i n the  the aluminum m a t r i x  t e n s i l e p r o p e r t i e s d e t r a c t s f r o m t h e UTS 2.1.  literature  the  towards composite  values  A v a r i e t y of c a l c u l a t i o n s c a r r i e d out  on  on  listed  tensile  in  Table  data  s u p p l i e d by T a n a k a e t a l ( r e f . 1 0 ) i n d i c a t e s y n e r g i s t i c strengthening and  of t h e c o m p o s i t e o c c u r s . The  accompanying data  i n F i g u r e 2.2  stress - strain  ( r e f . 1 0 ) was  used  to  curve  20  800  1000  600  400 h  200  0  0.5  1.0  Strain ( t ) Stress-strain b e h a v i o r o f SiC/606l composite Stress-strain b e h a v i o r o f SiC/5052 composite  SiC/1100 As-Fab. H.T.  v (*)  35  f  Tensile Strength ( MPa ) Elastic Modulus ( GPa )  FIG.  SiC/5052 As-Fab. H.T.  SiC/6061 As-Fab. H.T.  40  25  ( 0°)  861 (930*)  (90°)  15  ( E,)  89  92  121  130  100  119  ( E)  73  81  105  111  77  86  2  836  781 (1060*)  784  10  690 (710*)  680  140  2.2 - SIC/ALUMINUM COMPOSITE TENSILE DATA (REF.10)  21  determine strength  t h e aluminums c o n t r i b u t i o n through  E2  = VF  E2  = slope  VFp  value  cast  The  aluminum  from  mm  affect  h a r d e n i n g term  ( d s / d e ) was  calculated.  t o be  i s that  A possible  mm  T h i s would  after  be d i s c u s s e d  a reduction  indicate  important  that  The  f o r the asspecimen  yielding,  of  48  modulus of  for this  sample u s e d  an  the  in later chapters.  in tensile  about  Gpa  annealed  the e l a s t i c  of t h e t e n s i l e  brought  The  explanation  s t r e n g t h s i s an  that  1.0  37.3  hardening rate,  exists  68 Gpa.  factor. sample  increase  tensile  in obtaining It  was  thickness  in failure  stress  sample t h i c k n e s s  may  t h e s t r e n g t h e n i n g b e h a v i o u r o f t h e aluminum m a t r i x .  For comparative unidirectional  purposes  the mechanical p r o p e r t i e s  of  SiC reinforced  aluminum p r e p a r e d by Avco  Specialty  Products are l i s t e d produced The  o f 200  configuration  125 Mpa.  hardening  Gpa.  tensile  Gpa)  a stiffness  strengthening will  to  strain  calculated  i s only  (78  (0.25)  aluminum m a t r i x  ( r e f . 17)  of  fibres  yielding  h a r d e n i n g of t h e 6061  observed 1.8  curve a f t e r  contribute  anomaly which  ultimate  (ds/de)  of aluminum m a t r i x  a matrix s t r a i n  phenomenal The  fraction  strain  sample was  Gpa.  the  of s t r e s s - s t r a i n  strain  exhibited  x  F  a l l fibres  f o r the  apparent  (200Gpa) + ( 1 - V F )  = rate  that  composite  the f o l l o w i n g e q u a t i o n :  = volume  ds/de Assuming  x  F  to o v e r a l l  by v a p o u r  i n T a b l e 2.2. deposition  2.2.  from  sales  The  properties  literature  fibre  of B - S i C  m e c h a n i c a l p r o p e r t i e s of the  Table  The  fibre  summarized  p r o v i d e d by  utilized  by Avco i s  onto a carbon  substrate.  are also presented in  i n T a b l e 2.2  Avco.  an  were o b t a i n e d  22  TABLE  SiC/Al  SiC  Composite  Properties  2.2  -  Avco  Fibre:  SiC/Al  diameter  =  140  modulus  = 427  strength  = 3474  density  = 3.0  microns Gpa Mpa g/cm  3  Composite: volume failure  fraction stress  =  42%  = 1.41  Gpa  Specialty Products  23 E x a c t d e t a i l s on m a n u f a c t u r i n g a n d t e s t i n g were n o t g i v e n of  proprietary  2.2.3  important  Properties  i n t e r f a c e between a f i b r e  and a m e t a l m a t r i x  concern i s expressed over the type of i n t e r a c t i o n  occurs at the f i b r e - m a t r i x i n t e r f a c e since  the q u a l i t y of  the  bonding c o n t r o l s the load t r a n s f e r c a p a b i l i t i e s .  the  p r e s e n c e o f a weak bond w i l l  fibre  inhibit  p r o p e r t i e s due t o t h e p o o r  f i b r e and m a t r i x  full  load t r a n s f e r a b i l i t y  m a t e r i a l . Other  temperature  strength.  interfacial  increase into  cracking  by c o n v e r t i n g  t e m p e r a t u r e s bond s t r e n g t h  composite  energy  i s important f o r  of t h e aluminum  i n composite surface  the larger  (aluminum  = 23.6  result in possible fibre-matrix  decohesion. Yajima et a l (ref.20) observed a  fracture  elastic  i n t e g r i t y . During heating,  S i C = 5.8 X 1 0 ~ 6 ) w o u l d  reduction  damage.  which o c c u r s a t the i n t e r f a c e would  thermal expansion c o e f f i c i e n t X10~^,  and h i g h  energy.  At e l e v a t e d maintaining  between t h e  f o r p r e f e r e n t i a l composite  the composites toughness  surface  of the  o f a c o m p o s i t e m a t e r i a l , a weak  bond c a n be a s i t e  premature  example,  f a c t o r s t h a t a r e a f f e c t e d by t h e  bond q u a l i t y a r e f r a c t u r e t o u g h n e s s  During the loading  For  utilization  interfacial  The  has a v e r y  i n f l u e n c e on t h e m e c h a n i c a l p r o p e r t i e s o f a c o m p o s i t e .  In g e n e r a l , that  reasons.  Interfacial The  because  strength  a t 500 °C. A p h o t o o f t h e  indicated extensive  aluminum i n t e r f a c e . I f a s t r o n g  significant  debonding  at the SiC f i b r e  i n t e r f a c e e x i s t s the e f f e c t s of  24  interfacial transfer  capabilities  The metal  debonding  1) p h y s i c a l  bonding  2)  bonding  reaction  roughness  temperatures  can e x i s t  bonding,  (mechanical  as i m p l i e d ,  between a f i b r e  and f i b r e - m a t r i x  phase  be s u p p r e s s e d .  between a f i b r e  and a  ( a t an a t o m i c  With liquid  wettability  the i n t r o d u c t i o n  which  would  The  thermodynamics  for  SiC fibres  exist  in this  into  from t h e of the r e a c t i o n  bonding.  aluminum  postulated  system.  ( A L 4 C 3 ) would  form  + 4A1(1) = A L C ( s ) 4  f o r t h e above  in liquid  Gibbs  energy  v i aa  on t h e t y p e o f  It i s possible  that  (ref.21) according to  + 3Si(s)  reaction  have been  calculated  aluminum. F i g u r e s 2 . 3 (as  (calculation  i n appendix  A) show t h e  f o r t h e f o r m a t i o n of aluminum c a r b i d e f o r b o t h  respectively.  of temperatures i s assumed  3  and s o l i d  by r e f . 2 1 a n d 2.4  silicon  results  t h e S i C a n d aluminum  of S i C f i b r e s  calculated  conditions  the s t r e n g t h of  The c o h e r e n c y  with both  fibre  equation:  3SiC(s)  Free  bonding  t e c h n i q u e much h a s been  i n t e r m e d i a t e phase following  determine  p r o v i d e s t h e means f o r f i b r e - m a t r i x  pressing  interface  level)  on t h e p h y s i c a l  and m a t r i x . F a c t o r s s u c h a s  o f an i n t e r m e d i a t e p h a s e .  respectively,  range  may  cohesion)  relies  a bond. C o n v e r s e l y , r e a c t i o n  formation  the  that  d e g r a d a t i o n of the l o a d  matrix material are:  interaction  an  at elevated  types of bonding  Mechanical  such  and subsequent  The f r e e  energy  and a c t i v i t i e s  was d e t e r m i n e d  of s i l i c o n .  t o be e q u a l t o i t s w e i g h t  fora  The a c t i v i t y o f  percentage i n  25  FIG.  2.3  -  F R E E E N E R G Y OF ALUMINUM C A R B I D E  FORMATION  ALUMINUM F O R V A R I O U S  OF S I L I C O N  ACTIVITIES  IN  LIQUID  (REF.21)  26  FIG.  2.4  -  F R E E E N E R G Y O F ALUMINUM C A R B I D E IN  S O L I D A L U M I N U M FOR V A R I O U S  OF  SILICON  FORMATION ACTIVITIES  ( c a l c u l a t i o n s in Appendix  A)  27 s o l u t i o n which f o r the u t i l i t y  a l u m i n u m i s b e t w e e n 0.4 a n d 0.6  percent S i . The  f r e e energy v a l u e s  tend  negative  f o r both scenarios  (Figs.  formation  of t h e aluminum c a r b i d e  possibility solid  only  slightly  2.3 a n d 2 . 4 ) ; t h e r e f o r e , i s questionable.  The  of t h e r e a c t i o n o c c u r r i n g i n e i t h e r t h e l i q u i d or  s t a t e i s t h e n d e p e n d e n t on t h e r a t e o f r e a c t i o n .  Intuitively, greater  the k i n e t i c s  f o r the r e a c t i o n are considerably  i n t h e l i q u i d aluminum as opposed t o t h e s o l i d  Assuming t h i s the  t o be a t b e s t  statement  i s c o r r e c t , the p e r i o d of time i n which  f i b r e s are i n contact  considered aluminum The  critical  with  w i t h t h e m o l t e n a l u m i n u m c a n be regards  thermodynamics present  aluminum c a r b i d e w i l l  the  literature.  Iseki  Conversely,  had formed a t t h e i n t e r f a c e  o f p r e s s u r e l e s s s i n t e r e d S i C . The  w i t h t h e a l u m i n u m f o r one h o u r a t 1000 °C.  under i d e n t i c a l  was n o t d e t e c t e d  c o n d i t i o n s t h e p r e s e n c e of aluminum  on t h e s u r f a c e o f a r e a c t i o n s i n t e r e d  S i C b l o c k . The d i s c r e p a n c y free S i present  p i c t u r e of whether or  e t a l ( r e f . 2 1 ) , by means o f TEM a n a l y s i s ,  b e t w e e n a l u m i n u m and a b l o c k S i C was i n c o n t a c t  an u n c l e a r  form. T h i s u n c e r t a i n t y c a r r i e s over t o  d e t e r m i n e d t h a t aluminum c a r b i d e  reaction  t o the p o s s i b l e formation of  carbide.  not  carbide  state.  was r e l a t e d t o t h e l a r g e amount o f  i n the r e a c t i o n s i n t e r e d SiC i n h i b i t i n g the  (activity  o f S i a p p r o a c h e s o n e ) . Kohyama e t a l ( r e f . 1 6 )  d e t e r m i n e d from the e l e c t r o n d i f f r a c t i o n p a t t e r n of a sufficiently  thinned  S i C / A l sample t h e p r e s e n c e of aluminum  carbide at the f i b r e - m a t r i x i n t e r f a c e . Yajima e t a l (ref.19)  28  extracted detailed  fibres X-ray  detected.  f r o m an aluminum  a n a l y s i s . The p r e s e n c e  I t should  be n o t e  al  (ref.16)  and Y a j i m a  of  aluminum  carbide  fibres  bonding,  Nicalon  The d e c r e a s e  Owing  initiating  effect  contradiction strength,  the pre composite  (ref.19)  d i d not d e t e c t  may  occur.  strength  not  by t h e  given.  improve  Kohara  (ref.12)  (up t o 50%)  aluminum  on t h e f i b r e  of the f i b r e s  from  fibre  spent  was  fibre  f o r 30  surface  the flaws strength.  found  that  of f i b r e  of (ref.5).  have a In fibre  was c o m p a r a b l e  s t r e n g t h . However, Y a j i m a  the presence  after  minutes.  individual  t h e aluminum m a t r i x ,  not  formation  a t t r i b u t e d to the formation  the u l t i m a t e  removal  time  and S i C c a n  to molten  et a l ( r e f . 1 9 )  Yajima  after  aluminum  flaws  nature  on  as the exact  was  Rohyama e t  p e r t a i n i n g to the  in fibre  was  them t o  carbide  between  f o r each p r o c e s s  SiC fibres  to the b r i t t l e  comparisons  degradation  drop  in strength  carbide  substantial  to  fibre  a considerable  subjecting  aluminum  aluminum  and s u b j e c t e d  of aluminum  et a l (ref.19)  a r e a c t i o n between  interfacial observed  that  is difficult  i n the molten  Though  matrix  et a l  degrading  aluminum  carbide. The  literature  presenting properties.  reviewed  inconclusive in  a c o n s i s t e n t d e s c r i p t i o n of a S i C / A l The a m b i g u i t y  manufacturing  methods  is  this  hoped t h a t  pertaining  i s somewhat  used  may  result  i n producing  thesis will  t o t h e many  in part  provide  faceted aspects  composites  from  the  various  the S i C / A l composite. I t more c o n c l u s i v e of t h i s  results  material.  29  CHAPTER COMPOSITE  3.0  PRODUCTION  3.1 D i e D e s i g n a n d M a n u f a c t u r i n g In t r y i n g  to develop a manufacturing process f o r the  p r o d u c t i o n of a S i C / A l composite s e v e r a l problems overcome. These d i f f i c u l t i e s itself,  are not only  inherent  n e e d e d t o be to the SiC  b u t a r e a l s o d e p e n d e n t on t h e f o r m i n w h i c h t h e f i b r e s  a r e r e c e i v e d . F o r t h e N i c a l o n S i C f i b r e s on w h i c h t h i s r e s e a r c h project  i s b a s e d , a c o m b i n a t i o n o f two f a c t o r s make m a n u f a c t u r i n g  a composite with t h i s m a t e r i a l a challenge: 1) p o o r w e t t a b i l i t y 2) i n f i l t r a t i o n Wettability  o f S i C by a l u m i n u m  of aluminum  i s a measure  i n t o S i C tows  of t h e a n g l e which a molten  m a t e r i a l a s s u m e s when i n c o n t a c t w i t h a s o l i d definition solid  s u b s t r a t e . By  a c o n t a c t a n g l e o f l e s s t h a n 90° i s i n d i c a t i v e o f good  s u r f a c e c o v e r a g e by t h e m o l t e n m a t e r i a l  Conversely, n a t u r a l w e t t i n g of the s o l i d i s not p o s s i b l e  (ref.30).  by t h e m o l t e n  f o r contact angles greater  material  t h a n 90°. F i g u r e  ( r e f . 7 ) d e p i c t s t h e c o n t a c t a n g l e s between v a r i o u s  3.1  molten  aluminum a l l o y s and S i C f o r a range of t e m p e r a t u r e s . C o n t a c t a n g l e s o f a p p r o x i m a t e l y 135° f o r t e m p e r a t u r e s u n d e r 900 °C v e r i f y t h a t n a t u r a l w e t t i n g o f t h e S i C by m o l t e n a l u m i n u m To e n s u r e s u i t a b l e wettability  i s unlikely.  f i b r e aluminum m a t r i x c o n t a c t , t h e poor  i s overcome by h o t p r e s s i n g t h e a l u m i n u m  solidification.  during  30  —i 800  1 900  i  i  1000  1100  Temperature (°C)  FIG.  3.1  -  W E T T I N G OF S I C OF TEMPERATURE  C R Y S T A L BY ALUMINUM (REF.7)  AS  A FUNCTION  31 Coupled w i t h the  i n h e r e n t p r o b l e m of poor f i b r e  wettability  by m o l t e n a l u m i n u m i s t h e c o m p a c t e d f o r m i n w h i c h t h e  Nicalon  f i b r e s are  are  available density  r e c e i v e d . As m e n t i o n e d e a r l i e r , t h e i n tows c o n s i s t i n g  of the S i C f i b r e s  wettability  As  pressing results  i n h i b i t s adequate aluminum i n f i l t r a t i o n  into  this difficulty i n the  SiC  can  be  techniques. a number of  factors  preclude  The this  their  system employed i s  m a t r i x and  hot  satisfactory  These i n c l u d e :  non-reusable unidirectional  the problems mentioned above, w h i l e  s y s t e m was  and  infiltration,  still a  new  designed.  o b j e c t i v e of t h e m a n u f a c t u r i n g  thesis  use.  of  designs  overcoming poor f i b r e w e t t a b i l i t y manufacturing  have m a n u f a c t u r e d  methods have g i v e n  some m e t h o d s a b l e t o p r o d u c e o n l y composites  circumvent  the  o v e r c o m e t o some e x t e n t .  l i t e r a t u r e , researchers  Though t h e s e  packing  during  f i b r e r e i n f o r c e d a l u m i n u m by a v a r i e t y  2) m a n u f a c t u r i n g  To  t o the m o l t e n aluminum  only  high poor  1) c o m p l e x d i e  3)  e a c h . The  with their  cited  continuous  fibres  i n combination  t o w s . By a p p l y i n g p r e s s u r e fabrication  of 500  fibres  procedure developed  i s t o i n c r e a s e the s o l i d phase c o n t a c t f i b r e . Thus , a s u b s t a n t i a l  for  between  amount of p r e s s u r e  the is  a p p l i e d o n l y a t t h e p o i n t of a l u m i n u m s o l i d i f i c a t i o n . The a d v a n t a g e w i t h t h i s m e t h o d i s t h a t a much s i m p l e r d i e d e s i g n be  u t i l i z e d . F i b r e - m a t r i x bonding i s a c h i e v e d  sufficiently  by a p p l y i n g a  h i g h s t r e s s to p l a s t i c a l l y deform the  aluminum  can  32 into the  contact high  with  the  temperature  extrapolation  of  e x c e s s of  this  researchers) in  the  of  questionable. obtained  molten  useful  to d e s c r i b e  procedure  specific  will  be  Figure used  of  lower plunger  understanding  hot  pressing  manufacturing on  by  other  plastic  created solid  by  phase  i s obtained fibre  be  by  tows i s  discussed to  later,  the  cooling. of  the  technique  process  die  design  i t would  be  e m p l o y e d . From  d i e c o n f i g u r a t i o n and  schematic  hot  cross  pressing  to the  this  material  the  die  procedure. B a s i c a l l y ,  hot  ( F i g . 3.3)  pressing  but  p r o d u c e d c o m p o s i t e ) and  t o which p r e s s u r e  lower p l u n g e r s  s e c t i o n of  lower plunger  i s immobile d u r i n g  ( F i g . 3.4)  u p p e r and  will  the  semi-stationary  easy a c c e s s  plunger  initial  details  is a  quasi a  as  the  stress  process.  the  to  contact  A  deformation  a m i n i m a l amount of p r e s s u r e  quasi the  used  plastic  liquid  into  °C.  discussed.  3.2  f o r the  consists  allow  the  was  contact,  the  of aluminum  facilitate  with  560  eliminate voids  infiltration,  applying  better  associated  setup  by  reasonable  manufacturing  matrix  investigated  aluminum  at  46 Mpa  induce  Though e x c e l l e n t f i b r e  aluminum d u r i n g  To  i n the  fibre  10 Mpa of  to  (%6.0) d u r i n g  Aluminum  a  i n d i c a t e that pure  aluminum w i l l  method, p e n e t r a t i o n  (ref.23)  aluminum, and  (a p r e s s u r e  intimate  the  transformation.  is  of  approximately  value  aluminum c o n t r a c t i o n  this  of  aluminum u s e d  ensuring  deformation  strength  Weinberg  i s deemed s u f f i c i e n t  utility  Besides  fibre.  his results  possesses a strength in  SiC  system  the  die  (the  i s removable a mobile  upper  i s a p p l i e d . Encompassing  is a stainless  steel  to  the  UPPER  CAVITY  FOR  r  PLUNGER  SIC/AL  F I BREFRAX  TUBE  COMPOSITE  A OUTER  RING  CHROMEL LOWER  - ALUMEL  THERMOCOUPLE  PLUNGER  CO  FIG. 3.2  -  SCHEMATIC  C R O S S - S E C T I O N OF  PRESSING  SYSTEM  2.8  FIG.  3.3  - LOWER DIE  PLUNGER  (dimensions  i n nun)  FIG.  3 . 4 - UPPER DIE PLUNGER  (dimensions  i n mm)  LO  cn  36 ring  ( F i g . 3.5)  tube.  The  l i n e d on  u p p e r and  lower  movement w i t h i n t h e suitable  static  the  inner circumference  plungers  fibrefrax  are tapered  with a  to allow  tubing while s t i l l  s e a l a g a i n s t aluminum leakage  fibrefrax easy  maintaining  from the  a  composite  cavity. The  procedure used t o produce a SiC r e i n f o r c e d aluminum  composite 1)  i s as f o l l o w s :  Circular sheets  2) The  d i s c s of u t i l i t y  of S i C a r e a l t e r n a t e l y  stacked  e n t i r e d i e system i s placed  furnace 3) A t  a l u m i n u m and  until  the  unidirectional in die  i n t o a 815  °C  S i C / A l l a y u p r e a c h e s 733  °C  t h i s t e m p e r a t u r e t h e d i e i s removed f r o m t h e  and  placed  i n a h y d r a u l i c p r e s s . A water  copper j a c k e t i s then 4) A s l i g h t still  pressure  placed around d i e  46 Mpa 6) The  state.  i s held t i l l  plunger  subjected  made c o n s i s t e n t w i t h t o 815  must be a b l e t o w i t h s t a n d  r e q u i r e d s p e c i f i c a t i o n s a 316  ( r e f . 2 2 ) i t was  f o u n d t h a t 316  the  Furthermore, a s t r e s s of  stainless  chosen as the d i e m a t e r i a l . R e f e r r i n g t o the  specifications  °C.  °C.  To meet t h e was  composite reaches a  c h o i c e o f d i e m a t e r i a l was  lower  a t 600  of  °C  t h a t the d i e i s r e p e a t e d l y  46 Mpa  a pressure  i s a p p l i e d t o the d i e .  t e m p e r a t u r e o f 250  t h e t o p and  cooled  i s a p p l i e d w h i l e the aluminum i s  i n the molten  pressure  The  oven  perimeter.  5) A t t h e p o i n t o f a l u m i n u m s o l i d i f i c a t i o n  fact  cavity.  steel  ASM  stainless  steel  FIG.  3.5 - OUTER DIE RING AND FIBREFRAX TUBE (dimensions  i n mm)  to  38 has  a short  term y i e l d  maximum a l l o w a b l e A unique for  alumina,  intermittent surface  hot p r e s s i n g  a t 600 °C and a  temperature  system  which  and t h e r e m a i n i n g  lines  the outer  o f 870 ° C . and d i e d e s i g n  i s t h e i n c o r p o r a t i o n of a  t u b e . F i b r e f r a x i s a f i b r o u s mat 50% s i l i c a  fibrefrax  of 150 Mpa  feature p e r t a i n i n g to manufacturing  the quasi  fibrefrax  strength  c o n s i s t i n g of 45%  5% o f v a r i o u s  die ring  serves  oxides.  The  a v a r i e t y of  purposes i n c l u d i n g : 1) P r e v e n t s  welding  plungers  and o u t e r  2) In c o m b i n a t i o n fibrefrax molten 3) The  together  with  provides  aluminum  ring  of t h e s t a i n l e s s  during  the heating  the t a p e r e d  plungers  an e x c e l l e n t s t a t i c  leakage during  steel  heating  operation.  the  seal  against  operation.  low t h e r m a l c o n d u c t i v i t y of t h e f i b r e f r a x  heat  flow  away f r o m c o m p o s i t e  i n the  limits  radial  di rect ion. The together use  fibrefrax  tubing,  o f d i e components d u r i n g  of the d i e . B a s i c a l l y ,  component after  by e l i m i n a t i n g p o s s i b l e manufacturing,enables  the t u b i n g  a c t s as the  o f t h e h o t p r e s s i n g d i e s y s t e m and must  fusing multiple  sacrificial be  replaced  each r u n . Another  excellent tapered  static  prior  a fibrefrax  s e a l c a n be a c h i e v e d  plungers.  integrity static  advantage of u s i n g  This  feature  die lining  in combination  i s important  with  i n maintaining  t o h o t p r e s s i n g . Though t h e f i b r e f r a x  seal against  aluminum leakage,  c a u s e s aluminum t o flow  liquid  i s t h a t an  pressing  f r o m t h e d i e c a v i t y . As e x c e s s  the SiC/Al  provides molten aluminum  a  39 is  present  i n the i n i t i a l  aluminum a l l o w s Controlled fibre  (0.0052 w/m  flow  from  prematurely  important  was o b s e r v e d  especially  requirement  tensile  the  fibrefrax  to crack  requirement,  onto  the circumference  steel  k)  from copper  the f i b r e f r a x  ring  on  i s that a very  and t u b e  i s needed. I t  by t h e t o p p l u n g e r  would  fitting cause  l e a k . In c o n j u n c t i o n  to attach a cooling  of the outer  steel  steel  tube  i f t h e t u b i n g was l o o s e  i t was n e c e s s a r y  the s t a i n l e s s  the f i b r e f r a x  ring  and s u b s e q u e n t l y  f u r n a c e . The o b j e c t i v e f o r t h i s  ring  procedure  upon r e m o v a l  with  jacket from t h e  was t o s u f f i c i e n t l y  so a s t o t h e r m a l l y c o n t r a c t i t  t u b i n g and p r o v i d e a c l o s e r f i t .  Temperature C o n t r o l The  temperature  a chromel-alumel  of  (21.5 w/m  the water c o o l e d  of the s t a i n l e s s  hoop s t r e s s e s i n d u c e d  this  the  when  in placing  during pressing that  the  3.2  steel  tubing  the i n t e r i o r of the d i e . T h i s i s  f i t between t h e s t a i n l e s s  around  a closer  c o n d u c t i v i t y of the f i b r e f r a x  the edges of the composite  inner circumference  cool  enables  i s attached.  An  tight  aluminum a l s o  t o 316 s t a i n l e s s  in preventing  solidifying jacket  k) compared heat  of t h i s  achieved.  low t h e r m a l  radial  important  t o be  the flow  t h i c k n e s s t o be a d j u s t e d .  p r e s s i n g of the molten  The  the  f o r the composite  p l y spacing  inhibits  l a y up, c o n t r o l l i n g  lower  plunger  of t h e m a n u f a c t u r i n g  thermocouple p l a c e d  just  process  i s e v a l u a t e d by  below t h e s u r f a c e o f  ( F i g . 3.2). Because of the l a r g e thermal  the d i e r e l a t i v e  t o t h a t of the  aluminum, measurement  mass of the  40 die  temperature  typical in  i s a good measure o f t h e s y s t e m  temperature  - time p l o t  of a manufacturing  F i g u r e 3.6. The m e l t i n g and s o l i d i f i c a t i o n  aluminum c o r r e s p o n d t o t h e i n f l e c t i o n inflections heat  a r e due t o t h e r e l e a s e  d u r i n g the s o l i d / l i q u i d  3.7 d i s p l a y s  The  temperatures  standards  temperatures  (643 ° C ) .  be a t t r i b u t e d  stainless The exact  steel  A and B. T h e s e  and a b s o r p t i o n of the l a t e n t  m e l t i n g and  f o r the d i f f e r e n t  manufacturing  composite  are well  The l a r g e  molten  factor  incurred  - time p l o t  connected  inflection  each manufacturing  i s important  Appendix  A.  points.  procedure  during  cooling  i s not t o o b t a i n  with the composite  i n which the f i b r e s  i s measured a s t h e t i m e  solidification  i n the  and aluminum.  between  to  exposure  t o molten  t h e m e l t i n g and  The m o l t e n  a r e shown  a r e exposed  with regard to possible  aluminum c a r b i d e f o r m a t i o n . D u r a t i o n o f f i b r e aluminum  cited  as t o s t a n d a r d i z e the m a n u f a c t u r i n g  i s the time p e r i o d  aluminum. T h i s  to the  g r a d i e n t s b e i n g s e t up i n t h e  of the temperature  p r o c e s s . An i m p o r t a n t p a r a m e t e r temperature  below t h a t  deviations  to temperature  temperatures  well  runs.  o f 660 °C , b u t , t h e o b s e r v e d  between t h e t h e r m o c o u p l e  purpose  of the  t r a n s f o r m a t i o n f o r aluminum. F i g u r e  m e l t i n g temperature  solidification  A  r u n i s shown  temperatures  experimental melting values correspond quite  theoretical  can  points  the e x p e r i m e n t a l l y determined  solidification  temperature.  retention  times f o r  i n F i g u r e 3.8 and g i v e n i n  0.0  tim* (Bins.)  FIG.  3.6  -  «0.0  TIME  TEMPERATURE  PROFILE  (A,B  are  and  po i n t s)  melting  OF MANUFACTURING  solidification  RUN  inflection  43  740 720  -  700  -  680  -  cn 3 10  660  10 rH 0) U  640  w  620  31 •  36 •  38  •  39 -O-  • i-i  EH  2  600  W  580  JlSL  46  47 -B—  E-  + 38  H  + 39  + 36  560  -  540  -  520  -  500  42 -O—  43  •  + 44  + 45  + 46  + 47  X  w  37 •  + 31  ~r  i 4  2  ,  6  + 42 + 37  T" 8  SAMPLE  FIG.  3.7 -  MELTING  AND S O L I D I F I C A T I O N  + 43  TEMPERATURES  10  12  I FIG.  3.8  -  RETENTION  TIME  OF  FIBRES  IN  MOLTEN  ALUMINUM  44  A maximum t h e r m o c o u p l e  r e a d i n g o f 733  °C was  used as a  reference point  i n t h e m a n u f a c t u r i n g p r o c e s s . When t h i s  t e m p e r a t u r e was  r e a c h e d t h e d i e was  inserted  i n t h e p r e s s i n g d e v i c e . I t was  that a r e f e r e n c e thermocouple  p r e s e n t . The  o x i d e was  dissolution  t h a n 710  °C  was  of t h e aluminum o x i d e  i n t r o d u c e d through the aluminum d i s c s i n  o r i g i n a l composite  thermocouple  e x p e r i m e n t a l l y observed  t e m p e r a t u r e of l e s s  inadequate to achieve complete  the  removed f r o m t h e f u r n a c e and  l a y up. C o n v e r s e l y , h e a t i n g a b o v e a  temperature  o f 733  °C  i s n o t recommended.  The  i n c r e a s e d t i m e of f i b r e / m o l t e n aluminum c o n t a c t a s s o c i a t e d w i t h a higher  r e f e r e n c e t e m p e r a t u r e may  result  in extensive fibre  degradat ion. One  problem  a s s o c i a t e d with measuring  method i s t h a t a t any temperature  temperature  p a r t i c u l a r time the exact  i s not a v a i l a b l e .  desirable  and c o m p o s i t e . As m e n t i o n e d  3.3  pressing procedure L a y Up The  the  s t e e l between  i n the procedure  the  i t is  f o r delays i n temperature  r e a d out d u r i n g  r e q u i r e s o p e r a t o r e x p e r i e n c e and  judgment.  Preparation  S i C and a l u m i n u m a r e i n t r o d u c e d i n t o t h e d i e c a v i t y  alternating run  composite  t o a p p l y p r e s s u r e t o the aluminum a t i t s s o l i d i f i c a t i o n  temperature. Correcting the  this  T h i s d i s c r e p a n c y i s a r e s u l t of  t e m p e r a t u r e / t i m e d e l a y i n d u c e d by t h e s t a i n l e s s thermocouple  by  l a y e r s of each of t h e s e c o n s t i t u e n t s . F o r  36 h a s an  initial  precomposite  3Al/(SiC/Al)  example,  layup of:  4  By v a r y i n g t h e number o f S i C l a y e r s  i n t r o d u c e d , t h e volume  f r a c t i o n o f t h e a s c a s t c o m p o s i t e c a n be c o n t r o l l e d  by  t o some  45 extent. A l l manufacturing up a s f o r r u n 36. T a b l e and  procedures 3.1 l i s t s  have b a s i c a l l y  t h e number o f S i C p l i e s  used  the p a t t e r n i n which they a r e s t a c k e d . Each aluminum l a y e r c o n s i s t s of a c i r c u l a r  a l u m i n u m c u t f r o m a 0.83 m i l l i m e t r e t h i c k aluminum has t h e f o l l o w i n g c o m p o s i t i o n : 0.6% S i , 0.1% Zn a n d 0.1% C u . the d i s c s are cleaned w i t h  Prior  an i m p o r t a n t  factor  t o drum w i n d t h e f i b r e s  t o w s a r e bound t o g e t h e r  rolled  of  sheet.  utility Utility  1.0 -1.5% Mn, 0.7% F e ,  to being  stacked  i n the d i e ,  i s n o t o n l y more c o m p l e x b u t  i n the manufacturing  the h a n d l i n g of t h e S i C tows p r i o r necessary  disc  ethanol.  P r e p a r a t i o n of the S i C prepregg is  t h e same l a y  by a v i n y l  C i r c u l a r d i s c s of the S i C a r e then  p r o c e s s . To  simplify  t o s t a c k i n g i n t h e d i e i t was into unidirectional ester resin  strips.  (Derakane 411).  c u t and s t a c k e d w i t h t h e  aluminum i n the d i e c a v i t y . To e n s u r e a d e q u a t e S i C p r e p r e g g  p r e p a r a t i o n a v a r i e t y of  f a c t o r s n e e d e d t o be c o n t r o l l e d d u r i n g t h e drum o p e r a t i o n . These i n c l u d e d :  winding  The  46  TABLE Pre-composite  3. 1  Stackinq  Sequence  Run  Number of SiC layers  Stacking Sequence  31  4  3Al/(SiC/Al)  4  36  4  3Al/(SiC/Al)  4  38  4  3Al/(SiC/Al)  4  39  6  3Al/(SiC/Al)  6  41  6  3Al/(SiC/Al)  6  44  6  3Al/(SiC/Al)  6  45  6  3Al/(SiC/Al)  6  46  12  3Al/(2SiC/Al)  6  47  1 2  3Al/(2SiC/Al)  6  47 1) c o n t r o l  o f tow  spacing i n prepregg  2) amount o f r e s i n u s e d  t o b i n d tows  3) s p r e a d i n g o u t o f t h e i n d i v i d u a l F i b r e s p a c i n g i n t h e drum wound s t r i p o v e r l a p p i n g would i n h i b i t e x c e s s i v e tow obtained of  from  i s used  t o b i n d the tows,  prepregg  becomes d i f f i c u l t .  i n a tow  would  infiltration  improve  i n the manufactured  initial  poor  s p a c i n g and made and  early  amounts  Conversely, i f  h a n d l i n g of the individual  and  SiC  fibres  aluminum  composite.  drum p r e p r e g g i n g was  i n R i c h m o n d . The  fibres  t h e q u a n t i t y of  out the  fibre distribution  Products  and  Spreading  of  substantial  t o b i n d t h e tows s h o u l d be m i n i m i z e d .  n o t enough r e s i n  p r e p r e g was  i t s combustion,  tow  Conversely,  the volume f r a c t i o n  i n t h e f i n i s h e d p r o d u c t . To p r e v e n t  r e s i n used  tow  i s i m p o r t a n t because  aluminum i n f i l t r a t i o n .  spacing reduces  unwanted b y - p r o d u c t s  The  tows  done a t C a n a d i a n  runs r e s u l t e d  i n a prepreg  excessive resin. Later, a better successfully  Aircraft with  quality  i n c o r p o r a t e d i n t o samples  #31  #36. S u b s e q u e n t p r e p r e g g i n g was  d e p a r t m e n t f a c i l i t y . The several  Composites  i n n o v a t i v e f e a t u r e s which  c o n t r o l and fibres,  c a r r i e d o u t on a n e w l y  tow  s p a c i n g . Due  a l l o w s f o r improved  t o the s t r o n g c o h e s i o n  s p r e a d i n g of t h e i n d i v i d u a l  c a r r i e d out  f o r any  found to g i v e the  G r o u p drum w i n d e r  tows was  not  p r e p r e g g i n g o p e r a t i o n . The  i n appendix  possesses resin  between  successfully  drum c o n d i t i o n s  best  r e s u l t s a r e s u m m a r i z e d i n T a b l e B.1  installed  B.  48 3.4  Manufacturing A major  molten was with  problem  aluminum  alleviated carbon  adhered  appear  to  mix  by  in  the  sheet rolling  pressing  of  form  the  The  initial  leakage  some  extent  into  more  its  torch. the  was  the  Though  practical  and this  observed  that  difficulty  plunger  surfaces that  the  did  not  and  resulted  As  the  inner  to  leakage extent  effectively  solution  is  to  seal  from by  required.  is  rolled  this  hole  the  of  During gap  allowing  the  alleviates  a  initiation  circumference.  some  method  from  fibrefrax  corresponding  excessive  rectified  solidify  was  This  surfaces  correct  gap  aluminum  die  aluminum.  a  on  was  plunger  to  a  lower  It  tubing.  tube,  steel  surfaces.  and  fibrefrax  liquid  pressing.  to  molten  exists  problem  a  the  to  stainless  upper  difficult  the  to  the  well  with  a  adhere  acetylene  process  occurs.  continuing  an  more in  to  using  coating  quite  A problem discontinuity  with  tends  from  carbon  from  Difficulties  the  before  problem  to  49  CHAPTER  4.0  EXPERIMENTAL APPARATUS AND  The SiC/Al its  purpose  of t h e t e s t i n g p r o c e d u r e s p e r f o r m e d  composite  was  to provide  mechanical p r o p e r t i e s .  tensile  TECHNIQUE  properties,  a more c o m p l e t e  Parameters  microstructure  t o be  and  on  the  u n d e r s t a n d i n g of  examined  include  fibre-matrix  interfacial  analysis.  4.1  Tensile The  Testing  most d i f f i c u l t  preparation  aspect  of t e n s i l e  of s u i t a b l e s a m p l e s .  The  adequate  number o f r e p r e s e n t a t i v e  diameter  as c a s t  problems  with machining  Tanaka having  the f o l l o w i n g 80 mm  The  tensile  the specimens  in  implement,  wide  1.0  mm  t h i c k at curved reduced  of v a r i o u s  shaped  tensile  composite  reduced c r o s s  inch  determined,  tensile  specimens  bone s t y l e t e n s i l e i t was  section  samples  ( r e f . 1 7 ) . The  was  r e s u l t s were a  bone" shape specimen  adopted  sample  was  f o r use  tested  tensile  s e c t i o n as u s e d by T a n a k a  and a c u r v e d "dog  hence,  from a 3  an  were e n c o u n t e r e d .  mm  t h e most c o n s i s t e n t  dog  to obtain  length  deemed t o g i v e  curved  i n the  dimensions  SiC/Al  4.1)  was  samples  successfully tested  unidirectional  (Fig.  step  s i z e was  8.0  validity  thickness  first  c o m p o s i t e . Once sample  e t a l ( r e f . 10)  t e s t i n g was  samples  through et a l  (ref.10)  ( F i g . 4.2).  deemed  in this  for a  easier research.  to  The  50  co 60  FIG.  4.1  -  THROUGH T H I C K N E S S SAMPLE  1  TI  30  REDUCED  (dimensions  in  *|  50"  sL.21  CROSS-SECTION  TENSILE  mm R E F . 1 0 )  SEE NOTE A  7.6  3.3  64.0  FIG.  4.2 -  CURVED "DOG NOTE 46  A -  a n d 47  BONE"  TENSILE  reduced length for  which  is  SAMPLE  (dimensions  19 mm e x c e p t  reduced length  is  for  25 mm  in  mm)  samples  51 To  facilitate  preparation cast  /  a concise  composite,  direction  the  was  a 64  cut.  was  then cut  section  failure  i n the  solid  wheel  sided  grinding,  the  radius  curvature  was  divided  a  slowcut  mm.  of  50  grinding  to  section, wheel  a  strip  of  #80  by  the  as-  the  fibre parts  tensile  diamond  saw  circular  bonded  sample  and  dog  strain  bone  gauge).  grinding  consists  i s fastened  a  a of  The  press.  specially fabricated  of  layer  p o l i s h i n g paper. drill  hand  composite  a special  ( F i g . 4.4)  SiC  to  facilitate  with a conventional  i s held  Each  The  (underneath  cross  From t h e  into 5 equal  (Fig.4.3).  by  sample  parallel  t o whose c i r c u m f e r e n c e  sample  55  concentration  rectangle  necessary  location  f o r use  During chuck  4.5.  curvature  of  mm  rectangle  reduced  t a p e and  in Figure The  38  to p o s i t i o n  d e s i g n e d . The  i s adapted  shown  by  desired  aluminum c o r e  double  described.  ( F i g . 4 . 2 ) was  p r o d u c e the  wheel was  be  s p e c i f i c a t i o n s i n F i g . 4.2.  reduced  To  procedure w i l l  rectangle  from t h e  the  tensile  The  l a b e l l e d according  to  of  mm  and  ground  understanding  of  This mm  the  grinding  w h e e l was  designed  i s i n a c c o r d a n c e w i t h the  found n e c e s s a r y  effects associated  a  minimum r a d i u s  t o a l l e v i a t e any  with a curved  with  of  stress  reduced  section  (ref.17). The obtained of  strain  from bonded  a metallic  resistance by  measurements r e c o r d e d resistance  during  strain  t e n s i l e t e s t i n g were  g a u g e s . The  c o n d u c t o r w h i c h u n d e r g o e s a change  when s t r a i n e d . Gauge r e s i s t a n c e  a Wheatstone B r i d g e c o n f i g u r a t i o n  in  gauges  consist  electrical  ( s t r a i n ) i s measured  where t h e  strain  gauge  is ,  FIG.  4.3  -  TENSILE  SAMPLE L A B E L L I N G  53  ATTACHES  TO D R I L L  PRESS  I  20.0  110.0 NOTE  dia. B  9.0  FIG.  4.4  -  dia.  GRINDING  WHEEL  (dimensions  NOTE  outer  circumference  sided  B -  tape  a n d 80  SIC  i n mm) consists  polishing  paper  of  double  54  16.9  4.5  [::  13.0 J  L  2.0  2.47.8 59.5  74.0  FIG.  4.5  -  SPECIALTY MAKING  V I S E FOR H O L D I N G  SAMPLE  REDUCED C R O S S - S E C T I O N  WHILE  (dimensions  in  mm)  55  of  the f u l l  voltage  bridge.  across  calibrated type  of s t r a i n  into true  gauge  used  of  the s t r a i n  bone" It  gauge  in cross  A special  e m p l o y e d . The d a t a  on compact further All  recording  gauge  tensile  drop  strain tensile  i n area  operation,  grid  length  f o r the  unnecessary. a t t h e gauge  induced  reading. test  an O r i o n  internal  data  A loading  logger  Wheatstone  by t h e s t r a i n  gauge a n d  voltage  machine a l l o w e d f o r  of s t r e s s and s t r a i n .  This  data  was s t o r e d  t r a n s f e r r e d t o an IBM - PC f o r  (Fig.4.7).  t e s t s were  carried  o u t on an I n s t r o n  M a c h i n e a t a c r o s s h e a d s p e e d o f 0.51 mm/min. T e n s i l e dimensions are given  i s used t o  (due t o t h e c u r v e d "dog  s p a n s was deemed  (possesses  t a p e and s u b s e q u e n t l y  manipulation  to the short  a c o r r e c t i o n t o account  logger  i t into a true  simultaneous  o f 3 mm  2%.  the voltage  p r o d u c e d by t h e I n s t r o n  epoxy a d h e s i v e  t h e maximum c h a n g e  was a t most  measured  a length  sample a t t h e p o i n t o f  s e c t i o n a l area  To s i m p l i f y t h e s t r a i n  converted  possesses  on t h e t e n s i l e  (3 mm),  was c a l c u l a t e d t h a t  Bridge)  a s s u c h . The  s e c t i o n h a s been m a c h i n e d , t h e  shape) o v e r w h i c h t h e gauge  extremities  was  and r e c o r d e d  t o t h e c o m p o s i t e . Owing  change  4.6) w h i c h i s  i s a LY-61-3/120 m a n u f a c t u r e d by Omega  s e c t i o n a l area.  t h e gauge  continual  strain  reduced  i s centered  minimum c r o s s bind  (Figure  mm.  Once t h e "dogbone" gauge  r e s i s t a n c e produces a  Bridge  I n c . The r e s i s t a n c e g r i d  a w i d t h o f 1.4  strain  i n t h e gauge  t h e Wheatstone  directly  Engineering and  A change  i n A p p e n d i x C.  Testing sample  56  IG.  4.6 -  WHEATSTONE B R I D G E  CONFIGURATION  5 7  INPUT  INSTRON  FROM  STRAIN  GAUGE  LOAD DATA  INPUT  IBM  LOGGER  DATA H.P.  FIG.  4.7  -  PLOTTER  TENSILE  DATA A C Q U I S I T I O N  SYSTEM  P.C,  ANALYSIS  58  4.2  Volume F r a c t i o n The  Determination  volume f r a c t i o n  of S i C f i b r e s  present  were o b t a i n e d by a m a t r i x  dissolution  exact  involves cutting  from  dissolution  an a r e a a d j a c e n t  s a m p l e . The  Samples  °C  f o r 2 hours  48  hours. volume  following VF  t  =  above  while  fraction  observed.  instead  12.5  i s then  on  fibres  i s decanted  was  then  18).  long  the  tensile paper  are  of  is dissolved.  and  10% The  subsequently  were f u r n a c e d r i e d 47  The  sample  p l a c e d i n 80 m l .  a l l t h e aluminum  fibres  mm  mesh f i l t e r  at  were a i r d r i e d  calculated  using  60 for  the  of  weight  test  (Wt /2.6 + W t / 2 . 7 2 ) ) f  fibres  A 1  i n sample  of aluminum  for f i l t e r was  i n sample  paper  carried  (grams)  weight  out. Three  changes d u r i n g d r y i n g  filter  were s u b j e c t e d t o c o n d i t i o n s s i m i l a r  on a v e r a g e  To  of  f  (including  volume  a  s p e c i m e n s 44,45,46 and  (Wt /2.60) /  correct  reference weights  until  ( r e f s . 5 and  section  31,36,38,39,41,and 45  = weight  Al  To  sample  composite  equation: =  f  Wtf w  a t 55 °C  c o n t a i n i n g the  filtered.  reduced  a c o r r e s p o n d i n g #4  w e i g h e d . The  NaOH s o l u t i o n solution  t o the  sample and  individually  The  process  method  in a  filtering  a decrease  and  was  paper  applied  weight  of  to those  furnace d r y i n g ) .  in f i l t e r  This correction  papers  of  I t was 0.100  a  known mentioned found grams  during calculation  that was  of  fraction. eliminate of  this  correction  furnace drying  were, as m e n t i o n e d  was  earlier,  factor  attempted.  a i r dried  an  a i r drying  procedure  Sample 44,45,46 and  f o r 48  hours.  Three  47  59 reference  filter  conditions. to  account  the  water For  p a p e r s were a l s o  A correction for f i l t e r  paper  introduced during  dried.  corrections similarity  The  volume  weight  gain  filtering  was  samples  fraction  similar  f o u n d t o be  needed  a i r drying  as a l l  after  not e v a p o r a t e d .  45(A,B,D) were a i r and  of  fibres  f o r b o t h methods a r e summarized between  to  of -0.100 grams was  comparative purposes  furnace  subjected  the v a l u e s v e r i f i e s  determined  after  i n T a b l e 4.1.  that  either  The  procedure i s  acceptable.  4.3  Microstructure Polishing  presence  this the  was  minimize  aluminum by  composite  SiC f i b r e .  a transverse fibre  w i t h 600  Electron interface  patterns,  and  The  grit  paper  the f i b r e  the p r e s e n c e of A l C 3 4  using would  I t was  hoped  scoring  by  5.0  and  and  of a 1.0  grain  4.2.  Interface  to study the  SiC/Al  t o examine minute  electron be  as  steps included  followed  of F i b r e - M a t r i x  surface  direction  for precipitate  o f t h e methods a b i l i t y  to the  difficulty,  the subsequent  polishing  used  due  this  section.  in Table  beam m i c r o s c o p y was  because  analyzing  Analysis  cross  e t c h a n t s used  enhancement a r e l i s t e d  Diffraction  To overcome t o the f i b r e  breakage  these p a r t i c l e s .  diamond p a s t e . The  boundary  p r e s e n t s a problem  out p a r a l l e l  rough p o l i s h i n g  micron  By  carried  to p o l i s h i n g  would  final  4.4  a SiC/Al  of the a b r a s i v e  polishing opposed  Analysis  diffraction  verified.  areas.  TABLE Volume F r a c t i o n  Sample  Air Dry  (%)  4.1 Comparisons  Furnace Dry  (%)  4 5A  9.2  8.6  45B  6.9  8.4  4 5D  9.8  9.4  TABLE  4.2  Microstructural  Precipitate  Enhancement  ''  1 ml HF 200 ml  Grain  Boundary  Etchants  Etchant: (48%)  water  Etchant: 50 ml P o u l t o n s 25 ml HN0  Solution  3  12 grams C h r o m i c 40 ml w a t e r  Acid  62  Kohyama e t a l ( r e f . 1 6 ) technique Al C3  on t h i n  was d e t e c t e d .  4  produce  a chemical  thinning  circumvent  alternative  argon  on t h i s  fibre  using  this  specimen  however, t h e  t h i n n i n g an  was c a r r i e d o u t .  c r y s t a l s on t h e s u r f a c e  4  diffraction  technique  from a carbon/aluminum  substantiates  that  of a  (SAD).  composite procedure  NaOH i n low was a d o p t e d i n  obtained  f r o m t h e volume  31A were i n d i v i d u a l l y  fraction  analyzed  procedure of  i n both  t h e STEM and TEM.  used  i n t h e SAD a n a l y s i s a r e shown i n  term  r e l a t e s p h y s i c a l measurements  4.3. The  camera c o n s t a n t  the d i f f r a c t i o n  Angstrom  pattern  to c r y s t a l l o g r a p h i c plane  u n i t s . I t i s obtained  diffraction 4.3.  Ideally  i t s use.  would n o t d i s s o l v e AI4C3; and t h u s ,  following conditions  Table  on  procedure  work. Fibres  The  This  i n a 10% NaOH s o l u t i o n . T h i s  by K o h a r a e t a l ( r e f . 5 )  concentrations  physically  cracking.  examination  Al C3  were removed  were made t o  r e l a t e d t o specimen  a s e l e c t e d area  d i s s o l v i n g t h e aluminum  used  by f i r s t  be p r e f e r r e d ;  surface  carbon  by  attempts  ion milling.  would  the problems  method of f i b r e  fibres  example,  method p r e c l u d e d  et a l (ref.5) detected  carbon  this  procedure  diffraction  By t h i s method t h e e x i s t e n c e o f  S i C / A l TEM f o i l s  Kohara  The  an e l e c t r o n  s u c c e s s f u l due t o c o m p o s i t e  of information To  thin  (Dimpler) and then  not prove very  lack  foils.  Following  the required  polishing did  SiC/Al  employed  pattern  As t h e p l a n e  physically  using  spacings  measuring  spacing i n  from a m u l t i c r y s t a l l i n e g o l d  conditions f o r gold  the r a d i i  taken  identical are well  of the gold  t o those  i n Table  documented,  diffraction  rings  TABLE Selected  Stem  Area D i f f r a c t i o n  Conditions  Analysis: accelerating camera  length  camera  TEM  4.3  voltage = 1.2  = 200  KeV  metre  constant:  Run  A = 1.403  in.  Run  B = 1.456  in.  Run  C = 1.456  in.  Analysis: accelerating camera l e n g t h camera Run  voltage = 0.8  =  100  metre  constant: D = 2.040  in.  KeV  64 g i v e s a camera following  constant  w h i c h c a n be c a l c u l a t e d  equation: CC  = R x D  CC  = camera  constant  R = diffraction  ring  D = crystallographic  4.5  Heat The  radius  p r o c e d u r e s t o which the S i C / A l  aluminum. However,  supplied The  was  not t h e 6061  i t was  ordered  t h e s p e c i m e n s a t 415  s a m p l e s were t h e n c o o l e d 260  standard  °C was  reference  r e a c h e d . To samples  °C  discovered  for u t i l i t y  30 °C p e r hour u n t i l  (43A and  43B)  that  tempers material  grade  aluminum. involved  10 m i n u t e s .  The  a temperature of  t h e aluminum  underwent  the  aluminum)  f o r 2 h o u r s and  standardize  composites  a n n e a l and T6  but an u t i l i t y  annealing procedure ( s u i t a b l e  soaking  i n angstroms  Treatments  heat t r e a t i n g  6061  in inches  plane spacing  were s u b j e c t e d c o r r e s p o n d t o ASM for  from the  properties,  similar  two  heat  treatments. The temper the  T6 tempers  used, though not c o r r e c t ,  u s e d on s a m p l e s  s a m p l e s a t 525  immediately  and  T6B  involved  for  1 h o u r and  37D.  T6A  tempered  at  solutionizing  temper  42A  and  42B  involved  °C f o r 50 m i n u t e s . The 175  °C  samples  35 m i n u t e s . A f t e r  were s o a k e d a t 175 °C the  41D,  42B  and  samples  were  quenched  30 m i n u t e s .  44,  42C  47,  37D  T6A  solutionizing  f o r 7 h o u r s and and  water q u e n c h i n g , t h e  f o r 7 h o u r s and  a r e 42A,  a r e as f o l l o w s .  a t 525  °C  specimens  30 m i n u t e s . S t a n d a r d s f o r  f o r a T6B  temper  specimens  42C,  65  CHAPTER 5 Experimental  5.1  Tensile The  Test  composite mixtures  just  samples.  The  will  tensile  Due  be  data p r e s e n t e d , which s t r e n g t h and  used  testing the  procedure  SiC/Al  includes  apparent  t o enhance the  rule  number o f  understanding  of  fibres of  metal  behaviour.  to the d i f f i c u l t y  tensile  samples  for  one  individual  the t e n s i l e  the u l t i m a t e s t r e n g t h of  strength, fibre  contributing,  any  Data  i n f o r m a t i o n o b t a i n e d from  r e v e a l s more t h a n  matrix  Results  i t was  specimen. sample and  in producing a large  not p o s s i b l e The  tensile  not an  t o have  q u a n t i t y of  repetitive  data presented are  average  value  taken  testing  f o r each  from a number  of  spec imens. 5.1.1  As  Cast  Testing performed  hardening,  results strain  a s - c a s t and  strain,  will  be  stress-strain indicates  (ds/de)  curve  the behaviour  material. Table  r e f e r e n c e samples  following  the p o r t i o n  0.2%  of s t r e s s - s t r a i n  of t h e  of  yield  behaviour  The  A  the  rate  s l o p e of the Region  aluminum  strain  summarizes  tested.  was  including  tensile  5.1  to the  strain.  test, rate  t o the m a t r i x  corresponds  Samples  r e f e r e n c e samples  f e a t u r e s of each  correlated  t h e aluminum  hardening  treated  u l t i m a t e s t r e n g t h and  i n the composite of  heat  for describing  characteristic  and  observed  Heat T r e a t e d Aluminum R e f e r e n c e  as a b a s i s  m a t r i x . The strength  on  and  of  aluminum  in Figure  c u r v e where ds/de i s  5.1  66  o d co  L E G E N D  x  SAMPLE 43A SAMPLE 46'A  o d  CN'  <  B  Q_ CO CO CJ QL  f— CO  o d.  q d 0.0  1000.0  2000.0  3000.0  4000.0  MICRO STRAIN  FIG.  5.1 -  COMPARISON FIBRE  OF R E F E R E N C E ALUMINUM  REINFORCED  ALUMINUM  R E P R E S E N T A R E A S WHERE  (46A).  (ds/de)  IS  (43A)  5000.0  AND  R E G I O N S A AND B CALCULATED  6 7  TABLE AS  CAST  Sample  AND H E A T  Heat Treatment  TREATED  5.1  ALUMINUM  REFERENCE  UTS (Mpa)  Yield Stress (.2%) (Mpa)  SAMPLES  Rate of Strain Harden ing (Gpa)  37A  AS  CAST  118.5  49.4  3.1  37B  AS  CAST  118.2  43.0  3.4  42A  T6A  120.7  51 . 0  2.8  42B  T6A  120.0  52.3  2.7  37D  T6B  127.7  51 . 0  3.0  42C  T6B  122.6  52.4  3.2  43A  ANNEAL  116.7  50.6  2.5  43B  ANNEAL  112.7  50. 1  2.4  ASTM  ANNEAL  110.0  41.0  68 obtained. Additional is  available The  i n T a b l e C.1  improper  comparisons these  tensile  i n appendix  ultimate strengths observed  s a m p l e s compare the  i n f o r m a t i o n on  heat with  treatment  f o r the annealed  applied  t o samples  I t was an  observed  inclined  15° t o 40°)  that  be  42  reference  a result  A,B,C  carried  and  ( e g . low  37D,  out f o r  surface.  The  sloped  i s r e p r e s e n t a t i v e of a s h e a r  aluminum u s e d  of  a l l t h e aluminum r e f e r e n c e  fracture  mode. T h i s o b s e r v a t i o n i s c o n s i s t e n t the u t i l i t y  C.  known s t a n d a r d s c o u l d not  samples e x h i b i t e d (from  dimensions  f a v o u r a b l y t o t h e ASTM s t a n d a r d . As  specimens.  surface  specimen  with  the d u c t i l e  resistance  to  failure nature  of  shear  deformat i o n ) . 5.1.2  Composite T e n s i l e Figure  reinforced composite I of the matrix 400  46A  and  composite matrix  well  failure.  with the y i e l d  of  supported  by  failure.  fraction  state  test.  the matrix  of  At  matrix  fibres. the  Composite  load  which  at t h i s  Stage  aluminum  approximately This value  f o r the r e f e r e n c e yielding  i n which the failure.  non-  annealed  to both  observed  After  The  an  begins y i e l d i n g .  to composite  the t e n s i l e  fibre  and  strained.  strain  shown i n F i g u r e 5.1.  up  c u r v e s of a  curve corresponds  being e l a s t i c a l l y  hardens  (43A)  volume  t h e aluminum m a t r i x  throughout  the onset  entirely  13.9%  enters a quasi-elastic  strain  elastic  stress-strain  r e f e r e n c e sample  possessing  fibres  (43A)  the  stress-strain  microstrain  sample  compares  aluminum (46A)  correlates  at  5.1  Properties  The  aluminum fibres  failure point  is rapidly  the  remain  i s defined becomes  strained  to  69 The  majority  composite, displayed tested  (26)  strain  and  to  5.4.  each  Tensile  fibres  increased  are  observed  composite  strength  volume f r a c t i o n  specimens a l s o possess  the  explanation  the  regarding  in  provided  the Tables  such  as  in Table  C.2  of  strengths  the  with  fibres.  Though a  trend  samples possess  In a d d i t i o n ,  anomaly w i l l  volume  i n c r e a s i n g volume  strongest  weakest m a t r i x  this  5.2.  versus  (annealed be  a  these condition).  discussed  in  sections.  R u l e s of M i x t u r e determine a ROM  theoretical  assumptions  the  (ROM)  Strength  predictability  strength  was  strength  of  of  S i C / A l composites  c a l c u l a t e d . The the  composite  ROM  based  value on  tensile  predicts  the  that:  1) A l l f i b r e s mechanical of  listed  information  in Figure  low  behaviour  test  specimens  shown. I n s t e a d ,  sample a r e  tensile  presented  relative  To  those  Strength  i s d i s c e r n i b l e , some of  5.1.4  be  SiC/Al  C.  of  subsequent  to  or  l a r g e number of  t e s t s cannot  fraction  An  similar  sample d i m e n s i o n s a r e  experimentally  fraction showing  Owing t o t h e  tensile  and  either reference  curves  Additional tensile  Ultimate The  samples,  p r o p e r t i e s of  failure  in Appendix 5.1.3  5.1.  a l l the  tensile  5.3  tensile  display stress-strain in Figure  important 5.2,  of  200  Gpa.  present  contribute  p r o p e r t i e s and  to the  e x h i b i t an  composites elastic  modulus  TABLE AS  5.2  CAST  COMPOSITE  TENSILE  PROPERTIES  Sample  UTS (Mpa)  ROM (Mpa)  31A  112.0  104.2  7.0  1.07  0.90  31B  115.8  100.0  7.6  1.16  0.78  31C  112.0  77.0  10.2  1.45  31D  115.7  77.9  6.6  1.48  31E  106.4  118.7  8.0  0.89  0.98  36B  111.2  117.7  8.7  0.95  0.79  36C  107.5  117.1  9.9  0.92  0.79  36D  103.7  174.8  10.4  0.58  0.55  38A  116.7  170.0  11.5  0.69  0.62  38B  113.0  147.6  9.8  0.77  0.84  38C  106.0  128.3  9.6  0.83  0.59  38D  133.0  125.6  9.1  1.06  1.03  Volume Fraction (%)  UTS/ROM Ratio  FFC (%)  TABLE  5.3  ANNEALED COMPOSITE T E N S I L E  ROM (Mpa)  PROPERTIES  Sample  UTS (Mpa)  39A  130.4  158.0  11.3  0.83  0.88  39E  150.0  143.2  11.2  0.95  1.13  45A  150.0  91.3  8.6  1.64  45B  153.0  110.9  8.5  1.38  45D  156.3  95.5  9.4  1.64  46A  149.0  156.8  13.9  0.95  0.95  46B  138.5  158.7  13.2  0.87  0.81  46C  144.0  154.6  15.0  0.93  46D  156.0  127.5  13.9  1.22  Volume Fraction (%)  UTS/ROM  FFC (%)  TABLE QUENCHED AND T E M P E R E D  5.4  COMPOSITE T E N S I L E  PROPERTIES  Sample  UTS (Mpa)  ROM (Mpa)  41D (T6A)  130.0  173.0  12.1  0.75  0.82  44B  121.0  109.2  7.7  1.10  1.12  44C  138.0  123.9  7.4  1.11  1.14  44D  133.0  134.7  8.4  0.98  1.14  47B  1  134.  47.0  1  Volume Fract ion (%)  11.9  UTS/ROM Rat i o  1.10  FFC (%)  1  .23  LEGEND • = AS CAST x = T6 TEMPER •= ANNEALED  X  X  •  X *  X  A1-T6 X  Al-as  cast  u  •  u  u  n  u  Al-annealed  • •  1  i  0.0  4.0  • •  u  •  i  8.0  i  12.0  VOLUME FRACTION (PERCENT)  FIG.  5.2 - COMPOSITE STRENGTH VERSUS FIBRE VOLUME FRACTION  r  16.  74  2)  The m a t r i x observed  ROM  strengths  calculated  m a t e r i a l behaves  i n the reference  values  as l i s t e d  by t h e f o l l o w i n g  = volume  e  = failure  C F  Al  C  strain  composite  should  plots  o f t h e UTS/ROM r a t i o  be u n i t y  5.4) f o r a s - c a s t deviations solid  synergistic  matrix  F  x  (l-VF ) f  (Table  i s compared  versus  volume  these  will  of matrix  value  greater  high  matrix  in following  As t h e t h e o r e t i c a l  present  than  strengthening.  relative  a UTS/ROM r a t i o  ( r e p r e s e n t e d by  to either than  1) o r poor  than o n e ) .  synergistic  be d e a l t w i t h  ( F i g . 5.3 a n d  indicate large  (UTS/ROM g r e a t e r  of l e s s  of poor composite q u a l i t y  utilization.  t o the experimentally  one ( e g . Sample  >1.2) a r e  45A,B,D,  UTS/ROM v a l u e s . I n  specimens a l s o d i s p l a y t e n s i l e  Conversely,  C)  a t e^-p ( T a b l e C.2)  fraction  t r e a t e d samples  substantially  the result  C.2 a p p e n d i x  ( U T S ) . T h e o r e t i c a l l y , t h e UTS/ROM  (UTS/ROM l e s s  t o be a s s o c i a t e d w i t h  indication  C  by aluminum m a t r i x  strengthening  46D a n d 31C,D a l l e x h i b i t addition,  Al  +  The v a r i a t i o n s c a n be a t t r i b u t e d  UTS/ROM v a l u e s  fibres  )  i f t h e s t a t e d a s s u m p t i o n s a r e c o r r e c t . The  and heat  composite q u a l i t y  considered  5.2, 5.3, and 5.4 a r e  o f UTS/ROM from t h e t h e o r e t i c a l  line).  subject  C F  of composite  strength  ratio  sample.  i n Tables  p r e d i c t e d ROM s t r e n g t h  observed  to that  of f i b r e s  = stress carried  F  The  fraction  similar  equation:  ROM = ( V F f x 200 Gpa x e VFf  in a fashion  anomalies  strengthening.  thought This  chapters. than  0.85 i s a s t r o n g  i n terms of f i b r e  ROM s t r e n g t h assumes t h a t a l l  c o n t r i b u t e t o the composites  tensile  properties, a  75  6.0  F I G .  7.0  5.3  -  8.0  10.0  9.0  VOLUME FRACTION (PERCENT)  U T S / R O M A S - C A S T  R A T I O  VERSUS  SAMPLES  F I B R E  VOLUME  i  11.0  F R A C T I O N  12.0  F O R  LEGEND • = T6 TEMPER x = ANNEALED  X X  X X  X  I  6.0  G.  I  7.0  5.4  -  8.0  I  9.0  I  10.0  I  I  11.0  I  12.0  13.0  VOLUME FRACTION (PERCENT)  UTS/ROM RATIO  VERSUS  A N N E A L E D AND T E M P E R E D  FIBRE  I 14.0  I 15.0  VOLUME F R A C T I O N  SPECIMENS  FOR  1 16.  77 decrease in  i n the actual  a UTS/ROM r a t i o below u n i t y .  utilized  fibre  The a c t u a l  c a n be d i r e c t l y r e l a t e d  capabilities  of the composite.  I f aluminum  f o r proper transfer  a decrease  reinforcing, The (expect  paradox  arises  that,  ensure  that  fibres contributing Fibres The  contributing  used  of t h i s term  are calculated  5 . 1 ) . The e q u a t i o n u s e d i s as  from  (region  B Fig.  the apparent quantity  of f i b r e s  follows:  = ( 2 0 0 Gpa x FC/100) + ( d s / d e x  E  2  = slope  of composite  o f aluminum  forvariables  (1-FC/100))  s t r e s s - s t r a i n curve  = p e r c e n t a g e of f i b r e s  ds/de = s l o p e  fibres  of the q u a s i - e l a s t i c  s t r e s s - s t r a i n curves to obtain  on t h e same  However,  the slope  2  Values  quantity  i s a measure of t h e  i s based  E  FC  To  i n strengthening a  f o r t h e ROM p r e d i c t i o n .  of the composite  contributing  the apparent  versa.  i s calculated.  of f i b r e s involved  Calculation  assumptions  and v i c e  may  Contributing  apparent quantity  portion  i s not p r e v a l e n t ,  percentage of f i b r e s c o n t r i b u t i n g  composite.  i s poor  matrix strengthening unity  result  strength.  although f i b r e u t i l i z a t i o n  i n an a p p a r e n t UTS/ROM r a t i o n e a r t h i s scenario  would  i n matrix  i n composite  intrinsic  into the  contact  i s not a v a i l a b l e . This  a reduction  low UTS/ROM r a t i o ) ,  5.1.5  infiltration  fibre/matrix  result  of  transfer  i n t h e number o f f i b r e s i n v o l v e d therefore,  result  number o f f i b r e s  to the load  tows i s i n a d e q u a t e t h e i n t i m a t e  necessary in  number o f f i b r e s p a r t i c i p a t i n g w i l l  are given  contributing reference  s t r e s s - s t r a i n curve  i n T a b l e C.2 a p p e n d i x  C.  78  The the  percentage  actual  of f i b r e s  measured volume  s p e c i m e n . The r a t i o listed  i n Tables  contributing  contributing  fraction  of f i b r e s  of f i b r e s  compared t o  present  contributing/volume  5.2, 5.3 and 5.4 under  (FFC). A value  i s then  fraction  i n the  fraction i s of f i b r e s  o f FFC c o u l d n o t be c a l c u l a t e d f o r  samples  31C,D, 45A,B,D a n d 46D. The p a r a b o l i c s h a p e o f t h e s e  samples  stress-strain  curves  inhibit  o b t a i n i n g an a c c u r a t e  value  for E . 2  It  c a n be p o s t u l a t e d t h a t a low FFC r a t i o  suggests  poor  inadequate between  fibre/matrix contact  that a l l f i b r e s  contributing  additional  matrix  plot  than  This scenario follows inhibiting  proper  A FFC v a l u e  present  to the t e n s i l e  Though a r r i v e d FFC  utilization.  t h e aluminum a n d f i b r e s .  indicates  that  fibre  (less  load  of u n i t y  from transfer (+- 0.1)  i n the composite a r e  properties. This analysis  strengthening  at independently  are equivalent i n their  0.85)  assumes  i s not o c c u r r i n g . t h e v a l u e s o f UTS/ROM and  description  of S i C / A l composites.  A  o f UTS/ROM v s FFC ( F i g . 5.5) d i s p l a y s t h e c o r r e l a t i o n  between  these  two v a l u e s . The s o l i d  a one t o one c o r r e s p o n d e n c e . ratios  correspond  exhibiting  I t i s observed  with  near  each o t h e r ,  UTS/ROM a n d FFC p r o v i d e a v a l i d composites Low composite  tensile  i n F i g u r e 5.6 r e p r e s e n t s t h a t low UTS/ROM  t o e q u a l l y low F F C . A l s o , t e n s i l e  a UTS/ROM r a t i o  In c o m b i n a t i o n  line  one have c o m p a r a b l e i t i s felt description  FFC v a l u e s .  t h a t the v a l u e s of of a metal  matrix  behaviour.  v a l u e o f UTS/ROM a n d F F C , i n d i c a t i v e quality,  samples  a r e observed  of  substandard  t o be c o n s i s t e n t w i t h a s e t o f  79  FRACTION OF FIBRES CONTRIBUTING  FIG. 5.5  - UTS/ROM RATIO CONTRIBUTING  VERSUS FRACTION OF FIBRES  80  particular exhibit 5.2). this the  s a m p l e s . F o r example,  a low UTS/ROM r a t i o  s p e c i m e n s 38  (excluding  and c o r r e s p o n d i n g  low FFC  I t c a n be p o s t u l a t e d t h a t t h e m a n u f a c t u r i n g sample d i d n o t p r o v i d e  fibre  tows. C o n v e r s e l y ,  suggesting should  that the q u a l i t y  be n o t e d  inconclusive  (Table  procedure f o r  a d e q u a t e aluminum  infiltration  sample  ratios  44 p o s s e s s  of these  that metallography  in supporting  38D)  specimens  of samples  the v a r i a t i o n s  into  near u n i t y ,  i s adequate. I t 44C and 38A  observed  proved  i n composite  quali ty. The nature. do  a n a l y s i s presented The c o m p o s i t e  provide  tensile  a general  behaviour.  intrinsic  matrix  negligible 5.1.6  except  Fibre  anomaly e x i s t s  understanding  strengthening f o r samples  p e r t a i n i n g t o metal  sample  strain  matrix  i t i s p o s s i b l e that  31C,D,  45A,B,D a n d 46D.  s e c t i o n i t was o b s e r v e d  t o a ROM  expectation  that  up u n t i l  that the composites are f a i l i n g  and a s t i f f n e s s  0.5%.  samples a n a l y z e d  The f a i l u r e  in this  composites  the f a i l u r e .  observed  fibre  failure are  strength for  work t h e f o l l o w i n g c a l c u l a t i o n  c a r r i e d out: Fibre UTS_  Strength o m D  = ( UTS  c o m p  - Al  = s t r e n g t h of composite  c  f  )/ VF (Tables  The  a s t r e n g t h of  loading a  strains  To d e t e r m i n e c o m p o s i t e  some  at strains f a r  possessing  o f 200 Gpa. In a ROM  o f 1.0% i s e x p e c t e d .  approximately  but t h e y  i s o c c u r r i n g and c a n be c o n s i d e r e d  that predicted f o r a SiC f i b r e  2000 Mpa  qualitative in  Strength  behaved a c c o r d i n g  the  is basically  d e s c r i p t i o n s a r e by no means e x a c t  F o r any g i v e n  In t h e p r e v i o u s  below  above  f  5.2, 5.3,  5.4)  was  81 Al £  = stress carried  c  VFj Fibre  = volume  strengths Because  obtain  5.6  fraction  i s a plot  samples  that  observed  of  fibre  meet  this  fibre  strength,  only  o f 1.0 +-0.1 w i l l  strength  versus  criteria.  produced, t o  those  be a n a l y z e d .  volume  The maximum f i b r e lower  than  line  in Figure  the decreasing  5.6 ( l i n e a r  fibre  strength  with  volume  with  i n c r e a s i n g volume  inconsistent  tensile  contributing  to fibre  45A,  strengths strength  fraction observed loss will  strengthening  UTS/ROM r a t i o ) .  effect  A comparison  of samples  with  the other  5.1. F a c t o r s  o f t h e aluminum m a t r i x  was made between  45A a n d p o s s e s s e s a p r e d i c t a b l e s t r e s s - s t r a i n  of  UTS/ROM a n d F F C ) . 45A o v e r  - strain  increase  44D i s a p p a r e n t  curve  (high  the s t r e s s  45A and 44A. 44A has a s i m i l a r  An o b v i o u s  s a m p l e s 31D,  s p e c i m e n s due t o t h e  to  stress  t o the  be d i s c u s s e d i n  was n o t p o s s i b l e t o c h a r a c t e r i z e t e n s i l e  specimen  fraction  in fibre  contributes in Figure  of p o i n t s )  Anomalies  45B, 45D, a n d 46D a l o n g  curves  i n the  chapters.  T e n s i l e Sample  synergistic  cited  regression  strength  It  f o r the  strength  that  f o r t h e c o m p o s i t e s p l o t t e d . The r e d u c t i o n  5.1.7  which  Figure  fraction  observed  subsequent  samples  (2000 Mpa).  solid  represents  strain  C.3 a p p e n d i x C.  q u a l i t y of composites  (1102 Mpa) i s c o n s i d e r a b l y  literature The  i n Table  of the v a r y i n g  a UTS/ROM r a t i o  at failure  of f i b r e s  are l i s t e d  a representative  displayed  by aluminum m a t r i x  volume curve  strain fraction  ( i n terms  i n t h e s t r e n g t h e n i n g of  a s shown i n F i g u r e  5.7. The  f o r 45A does n o t e x h i b i t a s d i s t i n c t i v e  82  d LEGEND q  • = AS CAST  o o-  X  X  = T6 TEMPER  1  1000.0 900.0  X  • 800.0  FIBRE STRENGTH (MPA)  = ANNEALED  X  q d o -  •  o  d u>  1 6.0  FIG.  1  1  1  8.0  10.0  12.0  VOLUME FRACTION  5.6  -  APPARENT FRACTION  FIBRE  (PERCENT)  STRENGTH VERSUS F I B R E  1— 14.0  VOLUME  83  q d oo  FIG.  5.7  -  COMPARISON OF S T R E S S - S T R A I N 4 5 A AND 44D  CURVE  FOR S A M P L E S  TABLE YIELD  indicates  matrix  STRAINS  5.5  OF ALUMINUM M A T R I X M A T E R I A L  Sample  Yield Strain (u)  45A*  723  45B*  883  45D*  923  46D*  866  46A  402  43A  (ref)  519  43B  (ref)  281  44B  422  44C  381  44D  361  37D  (ref)  307  42C  (ref)  321  31A  554  31B  617  31C*  946  31D*  760  31E  258  37A  (ref)  500  37B  (ref)  743  strengthened  samples  85  a matrix 44A.  yield  point  The a p p a r e n t  Stage  break  I behaviour  increased  matrix  A unique  i n comparison f o r samples  occurs  with  these  samples  D) i s t h a t  the f r a c t u r e surfaces  the  horizontal  ( F i g . 5.8 l e f t ) . h o r i z o n t a l stepped  evidence  of shear  specimen  ( F i g . 5.8 r i g h t ) .  composite aspects  failure  are inclined  sections surface  due t o s h e a r i n g  Metallography  s a m p l e s 31C  a t above  30% t o  samples e x h i b i t a  fracture surface  The i n c l i n e d  i n the f o l l o w i n g  Microstructural  as-cast  (excluding  A l l other  in isolated  occurred  from  strains indicating  with  some  of the t e n s i l e indicates  forces.  that  Various  p e r t a i n i n g to the a d d i t i o n a l strengthening  discussed  5.2  failure  i n specimen  (Table 5.5).  and  predominantly  observed  31C,D, 45A,B,D and 46D  a t a much h i g h e r  strengthening  feature  to that  effect  will  be  chapter.  Analysis  was p e r f o r m e d  microstructure  on sample  42 and 47 t o d e t e r m i n e  and t h e e f f e c t s o f f i b r e  presence  on  this  microstructure. It  was o b s e r v e d  consisted confirms with  of a l i g n e d  the as-cast  aluminum r e f e r e n c e  Mn, Fe and A L . T h i s  the expected p r e c i p i t a t e composition  The  sample  p r e c i p i t a t e s ( F i g . 5 . 9 ) . An EDX a n a l y s i s  p r e c i p i t a t e s contain  elements present  the  that  i n the u t i l i t y  presence of f i b r e s  observed microstructure  i s consistent  i n regards  to the  aluminum.  ( F i g . 5.10) does n o t a p p e a r when compared  to Figure  to affect  5.9. A l s o ,  FIG.  5.8 - FAILURE MODES OF SAMPLE 45A (right)  (9x)  (left)  AND 38C  FIG.  5.10  -  AS CAST MICROSTRUCTURE (DARKER A R E A S  ARE  OF  FIBRES)  SAMPLE  47  (792  x)  88  excessive not  nucleation  of p r e c i p i t a t e s on t h e f i b r e  5.11  s t r u c t u r e o f sample 47  c o n s i s t s of r e l a t i v e l y  consistent dendritic  5.3  with cell  the f a s t  Interfacial  qualitatively  uniform  between  determined  the f r a c t u r e s u r f a c e s  The  l a c k of f i b r e  cooling rate  surface  by SEM  o f s a m p l e s 31E  i f the bonding  p e r f o r m e d . The  pattern  5.7  f o r Sample  5.13  f o r these  i s only mechanical adhesion  carbide,  are presented  diffraction from  four  and F i g u r e  silicon  i n Table  D.1  5.14  carbide  diffraction  i s present  and b e t a  patterns,  silicon  or  fibre diffraction  shows t h e  f o r the a c t u a l  carbide,  graphite,  plane  aluminum  (Appendix D).  patterns  of Table  i n A p p e n d i x D s a m p l e s B, C and D g i v e  aluminum c a r b i d e  of t h e separate  B. The v a l u e s  In c o m p a r i n g t h e d i f f r a c t i o n  aluminum  and  o f a good bond between t h e  results  i n Table  o f aluminum  carbon  values  5.12  was  and 44D r e s p e c t i v e l y .  p u l l o u t at the f r a c t u r e s u r f a c e  are l i s t e d  diffraction spacings  and aluminum m a t r i x  analysis. Figures  bonding, a s e l e c t e d area was  patterns  extensive  aluminum.  To d e t e r m i n e reaction  grains. This i s  inhibiting  the S i C f i b r e s  samples e s t a b l i s h e s the e x i s t e n c e and  equiaxed  shown i n F i g u r e  Analysis  are  fibre  (as-cast)  formation.  The b o n d i n g  that  was  observed. The g r a i n  and  surfaces  at the f i b r e carbide  5.6 w i t h  the  strong i n d i c a t i o n s surface.  have v e r y  the d i f f e r e n c e e x i s t s i n that  Though  similar aluminum  FIG.  5.11  -  GRAIN STRUCTURE  OF  SAMPLE  47  (530  FIG.  5.13  - FRACTURE  S U R F A C E OF  SPECIMEN  44D  (792 x)  91  1  •  •  V  F I G . 5.14  - DIFFRACTION  PATTERN  OF SAMPLE B  (1.6 x)  TABLE FIBRE  Sample  Sample  SURFACE  5.6  DIFFRACTION  PATTERNS  A: Ring #  Relat ive Intensity  Radius (in.)  1  3  0 . 57  2.46  2  1  0.67  2.09  3  faint  0.77  1.81  4  faint  0.94  1 .48  5  2  1.10  1 .27  6  faint  1 .29  1 .08  1  2  0.54  2.70  2  1  0.64  2.28  3  faint  0.77  1 .89  4  3  0.89  1 .64  5  faint  1 .09  1 .34  6  faint  1 .28  1.13  Plane Spac i n g (A)  B:  93  TABLE 5.6 CONT.  Sample  Sample  Note:  C: 1  3  0.55  2.65  2  1.  0.65  2.24  3  faint  0.75  1 .87  4  2  0.91  1 .60  5  faint  1.11  1.31  6  faint  1 .28  1.13  1  2  0.75  2.72  2  3  0.91  2.25  3  1  1 .28  1 .59  4  faint  1 .50  1 .36  D:  1 = brightest  pattern  2 = 2nd b r i g h t e s t  pattern  3 = 3rd brightest  pattern  94  c a r b i d e has a d i f f r a c t i n g electron  diffraction  plane  from t h i s  with plane  a spacing i s very  s a m p l e s B, C and D. A p h o t o o f t h e f i b r e corresponding  predominant i n  surface  t o sample B r e v e a l s t h e p r e s e n c e  reaction  product.  presence  o f aluminum c a r b i d e was n o t d e t e c t e d .  5.5  Fracture The  5.16  fracture  i s extensive  mode  that  tested exhibit  surfaces. Associated with delamination  shows t h e s t e p p e d  failure  exists  ( F i g . 5.15)  of a p o s s i b l e f o r sample A t h e  Surface  m a j o r i t y of composites  horizontal samples  The a b n o r m a l i t y  o f 2.23 A. The  fracture  f o r samples  relatively each of these  at the p o i n t of f a i l u r e .  surface resulting  from  Figure  this  38C and 44C. The i r r e g u l a r i t i e s a r e  s a m p l e s 45A,B,D and 46D w h i c h d i s p l a y s l a n t e d f r a c t u r e s w i t h o u t the  presence  of any e x t e n s i v e amount o f d e l a m i n a t i o n  ( F i g . 5.17).  FIG.  5.15  -  FIBRE SURFACE OF SAMPLE B (292000 (DARKER AREA IS  FIBRE)  x)  FIG.  5.17  - FRACTURE SURFACE OF 45A  (13  x)  97  CHAPTER  6.0  DISCUSSION  6.1  Manufacturing Technique The  hot p r e s s i n g  production this  processing  literature for  of S i C / A l  will  Fibre  (Fig.  46A  6.2.)  subtle prior  ( F i g . 6.1)  SiC f i b r e  composite  a l (ref.10)  are  view  of an u n i d i r e c t i o n a l  non-uniform  individual  cross  of  fibres.  fibre  composite  indicate  distribution,  P h o t o m i c r o g r a p h s of a by  show e x t r e m e l y p o o r  fibre distribution  and  fraction.  As  infiltration fibre  these photos  that  ( F i g . 6.3)  distribution  Tanaka  volume i s observed are  limited  to a s s e s s i f they  composite.  regardless  used d i f f i c u l t i e s  a t 40%  distribution  of a r e a a n a l y z e d i t i s d i f f i c u l t of the e n t i r e  only  a r e t r a c e s of  (Fig.6.3) provided  i s apparent  technique  sectional  section  representative  fibre  and  i n a d e q u a t e aluminum  35% volume  It  i n the  be s u g g e s t i o n s  with each composite  f i b r e . However, a b e t t e r  the scope  will  by Kohyama e t a l ( r e f . 16)  lamination  transverse  in  included  cross  with that  Associated  g r o u p i n g of  for  m e r i t s of  to the t e c h n i q u e s c i t e d  of t h e t r a n s v e r s e  manufactured  subsequently  The  Distribution  differences.  fraction  relative  suitable.  to the manufacturing procedure.  especially  et  i n t h i s work f o r t h e  i s deemed  be d i s c u s s e d . A l s o  Comparison specimen  composites  method  improvements  6.1.1  t e c h n i q u e employed  of t h e m a n u f a c t u r i n g  in obtaining  adequate  are encountered. T h i s problem  individual stems from  the  98  2 - TRANSVERSE (50  COMPOSITE  CROSS  SECTION ( R E F . 16)  x)  .3 - T R A N S V E R S E  COMPOSITE  CROSS  SECTION  (REF.10)  100 form a  i n which  tow  significant  metal matrix lead  thus, it  Nicalon  c o n s i s t i n g of  t o any  may  the  by  to  500  a hot  are  produced.  fibres  d i s p e r s i o n when  pressing  technique.  fibre  necessary  or  devise  monofilament by  SiC  utilization.  to a l t e r  a new  fibre  A v c o , may  the  form  production  possessing  lend  itself  incorporated  into a  Poor  To  Understandably  d o e s not  i n a d e q u a t e aluminum p e n e t r a t i o n  w o u l d be  produced  fibres  intertwinned  amount of  below a v e r a g e  obtained  SiC  fibre  distribution  i n t o the  SiC  alleviate  tows  this  i n which the  problem  fibres  method. I n c o r p o r a t i n g  a  large diameter  minimize problems a s s o c i a t e d  are  a  s u c h as with  and  that  fibre  tow  dispersion. 6.1.2  Volume F r a c t i o n A major drawback a s s o c i a t e d  method u s e d  i s the  relative  to other  would  to  the  be  could of  with  be  the  the  layup.  fraction  hot  40%). SiC  The  example, an  3A1  /  appears  manufacturing  15%)  introduced  initial  (3SiC/Al)  in  stacking  6  l a y e r would tow  induce  the  by  t o be  state. This u s e d by  p r o c e d u r e . The  of  the  the  excess  composite  method of m a n i p u l a t i n g  Tanaka e t a l  thin  problems  infiltration.  controlled pressing  liquid  incorporation  further  a l t e r n a t i v e solution involves minimizing  i n the  (maximum  obvious s o l u t i o n  prepreggs  For  pressing  sequence:  to aluminum/fibre  aluminum p r e s e n t still  (over  number of  a d d i t i o n a l prepregg  An  quasi  u s e d . However, i t i s a n t i c i p a t e d t h a t  pertaining  is  the  composite  the  volume f r a c t i o n s o b t a i n e d  researchers  increase  initial  pattern  low  with  ( r e f . 10)  s a m p l e s t e s t e d by  in  while  it  volume their  Tanaka e t  al  101 (1.2  mm)  indicate  necessary were  1.2  to mm  obtain thick  approximately of  SiC  i n the  composite  suitable  instead  quantity  pressed  3.5  mm  i t s volume  used  is sufficient  other  laminate  Figure  dependent  grouping  observed  shown  in Figure  Each  aluminum a r e a  layer  or  a  over-simplifies  interface  between  dispersed  than  of  macroscopic  6.4  i n the  the  by  mixtures  c o m p o s i t e modulus and of  to  the  if  be  number  obtain  i n the  suitable  better as  cast  of  matrix  layers  be  high  SiC  solid  The  into non  modeled  uniform  of the  either  fibre concentration.  fibre rich  the  line),  actual  affect  the  of  i n t e r f a c e . Consider  the  i s more  but,  on  the  two  overall  problem a r i s e s  an  This  composite.  separation  as  (the  layer  p l a s t i c deformation a f f e c t i n g  fibre/matrix  fibre  schematically  represents  dividing  most  distinct  fibre distribution  would not  strength.  The  schematic  loading  fails  f i b r e d i s t r i b u t i o n . For  can  micro  the  composite  f i b r e tows  i s representative  into d i s t i n c t  initiation  the  aluminum and  indicated  scale  rule  the  on  ( F i g . 6.4).  region  schematic  a  of  was  6.5.  macroscopic  46A  out.  partially  layers  distribution  specimen  that  researchers)  aluminum p r e s e n t  thickness  f r a c t i o n would  calculation justifies  of  to a  volume f r a c t i o n . I f  c i r c u m s t a n c e s under w h i c h a S i C / A l  specimens t e s t e d ,  In  was  Mechanisms  a p p e a r s t o be  phases  of  ( r e l a t i v e to  is carried  Failure The  all  a  composite  40.5%. T h i s  fractions  control  in  the  prepreggs c u r r e n t l y  volume  6.2  that  from  the  the  simplified  a  FIG.  6.4  /  /  /  / /  / /  / /  — 7x  /7  /7  //  /  /  /  / '  / /  /  FIG.  -  TRANSVERSE CROSS SECTION OF SAMPLE 44B  /  /  /  /  ~7~ ~7~ 7 / / S  / /  6.5  /  /  -  //  /  / /  /  /  m  x)  .  7  /  /7  /  /  (15  /7 —  / /  / •»  /  /  SCHEMATIC OF SAMPLE 44B  SIC CONCENTRATED REGION  CROSS  SECTION  103 ( F i g . 6.6) i n w h i c h a d i s t i n c t  loading  diagram  subject  t o a shear  layers.  The s o l i d  The  stress line  resistant  fibres  this  The all  layer.  inhibits  fibre  samples  tested  o c c u r r e d was m i n i m a l . distinctly  that  the shear  packing strain  layered  basis  Thus,  b u i l d u p which can the i n t e r f a c e .  composites  for this  t h e maximum s h e a r  mechanism  strain  c a n be c o n s i d e r e d a s t h i n  to i t s surface.  plates  stress  criteria,  Relating  this  aluminum  thin acting  t o Mohrs c i r c l e ,  surface results  F o r our s c e n a r i o t h i s  maximum s h e a r p l a n e p e r p e n d i c u l a r t o t h e f i b r e 6.6.  a  s t r e s s d o e s n o t have a f o r c e  i n the plane c o n t a i n i n g both  minimum s t r e s s d i r e c t i o n s .  on t h e  and t h u s c a n be e x p e c t e d  s t r e s s p e r p e n d i c u l a r t o t h e aluminum stress  i s dependent  results.  i n F i g u r e 6.5 t h e i n t e r v e n i n g  subjected to a tensile  maximum s h e a r  by o b s e r v e d  i s p e r p e n d i c u l a r t o the f i b r e  t o behave a s s u c h . A c c o r d i n g t o p l a n e  perpendicular  mechanism p r e d i c t e d f o r  i s supported  failure  f o r specimens  of d e l a m i n a t i o n t h a t had  the f a i l u r e  layers  Figure  shear  t o be t r a n s m i t t e d  in a stress  t h e amount  ( F i g . 6 . 6 ) . As shown  zero  of the h i g h l y  ( F i g . 5.16) e x c e p t  layers  plate  shearing plane.  of the s h e a r i n g  breakage or d e l a m i n a t i o n along  45A,B,D and 46D i n w h i c h  fact  The c l o s e  aluminum  t y p e o f d e l a m i n a t i o n d e s c r i b e d above was o b s e r v e d f o r  tensile  The  the adjacent  i s the i n t e r s e c t i o n  area. This results  cause e i t h e r  from  represent the h y p o t h e t i c a l  a r e a of importance  p l a n e and t h e f i b r e  through  originating  SiC layer i s  a  in a  t h e maximum and corresponds  layer  to a  a s shown i n  104  P A R A L L E L  F I B R E  SHEAR  D I R E C T I O N  D I R E C T I O N  S I D E  S I C  F I G .  6.6  -  CONCENTRATED  H Y P O T H E T I C A L  V I E W  R E G I O N  SHEAR  L O A D I N G  D I A G R A M  105 Samples delamination the  45A,B,D and 46D e x h i b i t o n l y a n d p o s s e s s an i n c l i n e d  S i C l a y e r s . As t h e a p p a r e n t  parallel  to the f i b r e  perpendicular  to the SiC r i c h  d i r e c t i o n o f maximum  can  be r e l a t e d t o f i b r e the other  (Fig.  failure  maximum  surface  shear  samples,  layer  shear  parallel to  direction i s  l a y e r s t h e o b s e r v e d amount o f  the  With  a m i n i m a l amount o f  delamination  i s n e g l i g i b l e . The change i n  stress  f o r samples  d i s t r i b u t i o n within  these  t h e S i C l a y e r s were w e l l  6.4) and t h e aluminum was p r e s e n t  45A,B,D and 46A specimens. spaced  a s a number  of d i s t i n c t  l a y e r s . However, s p e c i m e n s 45A,B,D a n d 46D e x h i b i t a fibre as  packing  such  one d i s t i n c t  stacking this  that  the m u l t i p l e  macroscopic  sequence  concentrated  layer  shown s c h e m a t i c a l l y fibre  stacking,  i n Figure  aluminum  l a y e r s behave a s t h i n p l a t e s  (instead  of 5 or 6 d i s t i n c t  becomes  regions).  T h u s , due t o t h e p o s s i b l e  stress  criteria,  t h e maximum  any  specimens  45A,B,D and 46D p a r a l l e l  that the  i s divided  into 2  breakdown o f t h e p l a n e  i s not expected  p a r t i c u l a r d i r e c t i o n . From t h i s ,  r e s u l t s i n the  questionable,  l a y e r s t h e aluminum  larger  considered  6.8. I n l i g h t o f  the approximation  shear  concentrated  S i C l a y e r s c a n be  ( F i g . 6.7). T h i s  apart  the shear  to the f i b r e  t o occur i n  f a i l u r e of layers  i s not  surprising. 6.3  Tensile The  tensile  indicative be  Results test results cited  of the range of S i C / A l  encountered. Deviations  i n Table  composite  5.2, 5.3 a n d 5.4 a r e properties  that can  i n the mechanical p r o p e r t i e s can  FIG.  6.7  -  T R A N S V E R S E CROSS  FIBRE  S E C T I O N OF S A M P L E 4 5 A  (20  x)  DIRECTION  SIC  CONCENTRATED REGION  FIG.  6.8 -  S C H E M T A I C O F S A M P L E 4 5 A CROSS  SECTION  1 07  be  a t t r i b u t e d to the v a r i a b i l i t y  u s e d . Due t o c o n t i n u a l the  i n the manufacturing  improvements  composites produced  near  i n the p r o d u c t i o n  t h e end o f t h e  (44,45,46,47) a r e i n t e r m s o f s t r e n g t h , UTS/ROM r a t i o 6.4  of h i g h e r  Intrinsic  strength this  the t e n s i l e  aluminum m a t e r i a l  be c o n s i d e r e d  value.  literature up  until  review  research  volume  earlier  fraction  properties  not o n l y  extent  of a S i C f i b r e  should  the ultimate  are negligent  i n addressing  Of s p e c i a l n o t e  i n which the a u t h o r s  behaved  a l l authors c i t e d  i s the paper  fail  materials  contribution to overall  presented  i n the l i t e r a t u r e  to discuss composite  review,  tensile  up t o 52 Gpa. C o n s i d e r i n g  only  70 Gpa t h e o b s e r v e d  the e l a s t i c  strain  i n reaching  i n the  composite  behaviour  by T a n a k a e t a l the  matrix  strength. data  T a n a k a e t a l ( r e f . 10) i n d i c a t e s aluminum s t r a i n of  and  samples.  b u t how t h e c o m p o s i t e  To a v a r y i n g  failure.  (ref.10)  q u a l i t y than  technique  Strengthening  In a n a l y z i n g reinforced  process  As  s u p p l i e d by hardening  rates  modulus o f aluminum i s  hardening  rates are quite  phenomenal. Further  c a l c u l a t i o n s on t h e d a t a  were c a r r i e d o u t . A s s u m i n g a ROM contribution overall Figure  composite  strength  2.2. The 6061 m a t r i x  373 Mpa stressed for  of the annealed  at a strain t o 233 Mpa  annealed  s u p p l i e d by T a n a k a e t a l  loading,  the r e l a t i v e  6061 and 5052 m a t r i x  materials  was c a l c u l a t e d from d a t a contributed  presented  o f 0.6%. The u l t i m a t e  6061 and 5052 a r e 124 Mpa  in  a c a l c u l a t e d s t r e n g t h of  o f 0.82%. S i m i l a r l y , t h e 5052 m a t r i x at a strain  to  and 199 Mpa  was  strengths  respectively.  108 For  the  lows s t r a i n s at which the  were c a l c u l a t e d  a comparison  with  the  yield  s t r e n g t h s of  more p e r t i n e n t . The  yield  s t r e n g t h of  matrices  w o u l d be  55.2  Mpa  and  The  e x t r a o r d i n a r y amount of  90.0  Mpa  aluminum m a t r i c e s  above  i s not  strengthened  by  be  hypothesized  interact  can  s t r e n g t h s up  t h a t the N i c a l o n  the  aluminum  phase p a r t i c l e s .  By  samples observed  in this  the  in a  examining  45A,B,D, 46A  UTS/ROM r a t i o s to e x h i b i t influence  and  matrix the  comparison  The  tensile  of  failure  inclined It  until  fracture can  be  strengthening dislocation  strains  s u r f a c e and  be  and  barriers.  T h i s type  that  virtue  matrix  t o t h a t of  second  strengthened  factors  affecting  of  their curves  high are  samples with is carried  5.7),  f o r sample  additional SiC  a  non  out. strengthened parabolic rates  45A,B,D and  l a c k of  deemed  factors  mechanisms o b s e r v e d  (Table  to the of  i t can  i n the  intrinsically  distinct  attributed  present  d e t e r m i n e what  to these  to  Al-Zn-Mg-  From t h i s ,  stress-strain  p o s t u l a t e d that the can  by  To  f e a t u r e s unique yield  up  31C,D  known  determined.  specimens  specimens a r e : higher hardening  be  strengthening  strengthened  Mpa.  fibres  i t i s hoped  strengthening.  f e a t u r e s unique  synergistically  670  the  highly  example, an  synergistically  characteristic  additional  of  and  For  in  A well  t o be  fashion similar  the  work,  to  SiC  s t r e n g t h e n i n g mechanisms can Samples  6061-O i s  observed  is its ability  second phase p a r t i c l e s .  exhibit  with  strengthening  overly surprising.  f e a t u r e of aluminum  alloys  these  f o r 5052-O.  advantageous  Cu  strengthening contributions  46A,  the  delamination. matrix  fibres  strengthening  acting  as  i s analogous  to  109 that  obtained  observed  f r o m s e c o n d p h a s e p r e c i p i t a t e s . The  in y i e l d  strengthening strength the  s t r a i n may  mechanism  of a p a r t i c u l a t e r e i n f o r c e d m a t e r i a l  particles  ( r e f . 2 4 ) . In  shear s t r e s s r e q u i r e d following  G = matrix  shear  equation  calculated according  between  two  additional  to  the  modulus  separation  i s b a s e d on  only For  to  spherical particle  introduce  a constant  The  d e p e n d e n t on  particle the  the  spacing  (analogous to f i b r e  these f a c t s w i l l  s i z e of  the  be c o n s i d e r e d  and  is  yield  burgers vector  inversely proportional  v o l u m e f r a c t i o n and  i m p o r t a n c e of  reinforcement  f a c t o r s that would a f f e c t  s h e a r m o d u l u s and  stress i s considered  spacing.  The  be  form the  by  vector  1 = particle  strength.  can  yield  i s determined  t o move a d i s l o c a t i o n l i n e  i t s most s i m p l i s t i c  the  1  b = burgers  intended  Orowan  equation:  T = G x b /  yield  a t t r i b u t e d t o an  ( r e f . 2 4 ) . Orowan p r o p o s e d t h a t  shear s t r e s s r e q u i r e d  This  be  increase  the  to p a r t i c u l a t e spacing) i s second in a  phase.  later  section. On  the  initiation  material enters strengthening  of p l a s t i c  a region  flow a second phase hardened  exhibiting a parabolic  ( r e f . 2 8 ) . A f t e r the  parabolic  s t r e s s - s t r a i n curve follows a l i n e a r  rate  hardening region,  work h a r d e n i n g  s t r e s s - s t r a i n c u r v e s f o r s a m p l e s 31C,D, 45A,B,D and exhibit exists  distinct  parabolic  of  rate.  the  The  46D a l l  t r a n s i t i o n a f t e r y i e l d i n g . The  that composite f a i l u r e occurs before  the  o n s e t of  anomaly linear  1 10  work h a r d e n i n g . T h i s inducing  premature  The  increase  unreinforced loops  may  be  fibre  due  to  rate  is possibly  the  i n t e r a c t i n g with g l i s s i l e loops  passing  second phase p a r t i c l e s .  hardening volume  by  f r a c t i o n and  2 8 , 3 2 ) . Though the particles  for  the  a spherical In an  to high  al  of  rate  by  by  Arsenault  a discontinuous and  SiC/Al a  quenched greater  the  aluminum and  Several  samples t e s t e d .  amount of  the  SiC  that  by  strain to  spacing  i s for  aligned  f a c t o r of  (ref.  spherical needle  2 above  samples amount of  the  that  synergistic  composite  i n the  (21.6  x  attributed  size. by  10~  and  6  The  low  volume  f r a c t i o n of  lend  itself  and  T6B)  w o u l d be  t h e r m a l work h a r d e n i n g . As  samples were e i t h e r a n n e a l e d  or  the as  contraction 5.0  x  of  this  fibres  t o any  expected  The  aluminum  thermal  i n d u c e d work h a r d e n i n g . More  (T6A  was  concepts d i s p e l strengthening  aluminum w o u l d not  thermally  strengthened  of  fibre  t o have been p r o d u c e d  of  to  to  The  dislocations  proportional  small, s u b g r a i n  coefficient  relative  a  (ref.25)  r e s u l t i n g from d i f f e r e n c e s  the  (ref.28,32).  mechanism  proposed  deformation  in  fibre dislocation  increment  t o be  the  to a u n i d i r e c t i o n a l f i b r e ) would  hardening  were p r o p o s e d  respectively).  of  glissile  The  proposed  ( r e f . 28)  dislocation density  dislocations  present  particle.  article  strengthening  previous  strengthening  (analogous  strain  r e s u l t of  inversely proportional above  Tanaka et  shaped p a r t i c l e increase  f o r m e d by  t h i s method was  above t h a t  dislocations  dislocation the  are  stresses  failure.  in hardening  matrix  shear  10~  type  present  substantial  importantly, to  6  exhibit  the  a  intrinsically cast  the  effect  111  of  thermally  for  induced  strengthening  t h e volume f r a c t i o n s In a q u a l i t a t i v e  to matrix  discussed  associated with  these  that the m a j o r i t y  synergistic  strengthening  areas  additional  (samples  an e v e n l y  separated  exhibiting  a close packing  of f i b r e s i n  may be a t t r i b u t e d  distribution  w o u l d be r e q u i r e d t o p r o v i d e  S i C tow. As m e n t i o n e d  monofilament  SiC fibre  for similar  such  The  to these  as produced  fibre  size  of s m a l l  matrix  fibre  diameter  hardening.  distribution  The  from a  by i n c o r p o r a t i n g a by A v c o ,  The drawback o f s u c h  the d i s t r i b u t i o n a solution i s  the increase i n fibre  spacing  would d e t r a c t from the s t r e n g t h e n i n g  proposed.  extent  an i m p o r t a n t  considered.  of m a t r i x factor  strengthening  when h i g h  If a substantial  t o matrix  activated  earlier,  volume f r a c t i o n s  t o the larger  mechanisms  maximum  in obtaining a suitable  p r o b l e m would be m i n i m i z e d .  due  size.  further analysis.  Nicalon  is  is particle  spacing.  i s s e m i - q u a l i t a t i v e i n nature and  arises  due  and p a r t i c l e  of composites  observed  problem  that  factors  important  45A,B,D a n d 46D) ( F i g . 6.7) t h e  strengthening  Ideally fibres  fraction  possessed  parameters. This observation deserves  here.  a r e volume  Considering  specific  negligible  s e n s e t h e p a r a m e t e r s deemed most  strengthening  Inherently  c a n be c o n s i d e r e d  strengthening  matrix  aluminum m a t r i x  creep  o c c u r r i n g i n a composite  temperature  p o r t i o n of a composites than  difficulties  w o u l d be e n c o u n t e r e d .  would r e s u l t  p r o p e r t i e s are being  in additional  with  strength i s  thermally  Creep i n the load being  p l a c e d on  1 12 the  fibres  Further 6.5  and  study  Fibre The  value  the  possibility  in this  area  fibre  would be  strength  i s f a r below t h a t  dramatic  decrease  possible  f a c t o r s . In  cited  in fibre  would  degradation  by  the  the  the  literature can  be  previous  fibres  apparent  aluminum c a r b i d e  due  fibre  formation  strength  r e d u c t i o n . The  relative  c o n t r i b u t i o n of  speculated  formation  6.6  Interfacial The  indicate This  w o u l d have t h e  results the  strongest  of  the  presence  the  of  the  f o r the  bonding  cohesion  in maintaining deformation.  damage to a  these  i s unknown, b u t ,  aluminum  it  carbide  effects.  aluminum c a r b i d e l a c k of  between t h e  between  composite  fibre  (Figure  a d e q u a t e . However, c o n s i d e r i n g observed  and  and  Also,  e a c h of  S e l e c t e d Area D i f f r a c t i o n  fracture surfaces  microscale  shearing  Properties  would a c c o u n t  composite  shearing  three  would c o n t r i b u t e  strength degradation  that matrix  and  The  the  strength.  operation  be  This  2000 MPa.  to matrix  pressing  fibre  of  analysis  hot  towards  Mpa.  a t t r i b u t e d to  during  can  the  of  on  reduce  i n the  1102  incurred  parameters  failure.  required.  c a l c u l a t e d was  strength  light  stress placed  delamination fibre  premature composite  Strength  maximum  additional  of  the the  integrity  at  the  pattern fibre  p u l l o u t observed  5.12  and  5 . 1 3 ) . On  fibre  and  matrix  macroscopic distinct at  the  surface.  plies onset  on  the  a  i s deemed  delamination is of  insufficient matrix  1 13 Though the  t h e a l u m i n u m c a r b i d e may  f i b r e and m a t r i x  fibre  s t r e n g t h may  were e x p o s e d  t o molten aluminum  any c h a n g e i n a p p a r e n t  forming  the bonding  between  some o f t h e r e d u c t i o n o b s e r v e d i n a p p a r e n t  be a t t r i b u t e d  c a n n o t be a t t r i b u t e d  improve  fibre  to i t s formation. for equivalent  periods  ( F i g . 3.8)  s t r e n g t h from sample t o sample  to differing  during manufacturing.  As a l l s a m p l e s  amounts  of aluminum  carbide  1 14  CONCLUSIONS  1)  The m a n u f a c t u r i n g  process  used  c o m p o s i t e p l a y s an i m p o r t a n t mechanical time  i n producing  role  a SiC/Al  i n a composites  p r o p e r t i e s . Such p a r a m e t e r s a s m o l t e n r e t e n t i o n  (aluminum c a r b i d e  formation), pressing  pressure  ( m a t r i x v o i d c o n t r o l a n d p o s s i b l e f i b r e damage) a n d interlaminar  s p a c i n g must be more c a r e f u l l y  ensure the q u a l i t y 2)  of the composites being  The c o n d i t i o n l i m i t i n g reinforcing  obtained  scenario results  property  utilization  deformation  produced.  t h e u s e o f N i c a l o n S i C tows f o r  a m e t a l l i c m a t e r i a l i s t h e poor  distribution This  controlled to  individual  fibre  i n c o m p o s i t e s made f r o m t h i s m a t e r i a l . i n inadequate  fibre  and i n c o m b i n a t i o n  mechanical  with  matrix  may l e a d t o p r e m a t u r e c o m p o s i t e f a i l u r e due t o  delamination. 3)  The f o r m a t i o n  of aluminum c a r b i d e a t t h e S i C / A l i n t e r f a c e i s  t h o u g h t t o c o n t r i b u t e t o t h e good f i b r e - m a t r i x b o n d i n g observed.  The e x t e n t  aluminum c a r b i d e 4)  o f f i b r e damage i n c u r r e d due t o  formation  i s unkown.  An a d v a n t a g e o f u s i n g a m e t a l l i c m a t e r i a l i n c o m b i n a t i o n with a reinforcing strengthening interaction.  fibre  i s the s y n e r g i s t i c  t h a t may be o b t a i n e d  matrix  through m a t r i x - f i b r e  115  RECOMMENDATIONS  1)  An i m p o r t a n t further  aspect  analysis  incompatability. remaining  of metal  concerns This  elastic  using  a high y i e l d  plastic  s t r e n g t h must  As c o n t i n u o u s in  very  fibre  specialized  work on m e t a l  matrix  l o a d c a n be  on c o m p o s i t e  requires  the f i b r e s  loading procedure  s t r e n g t h aluminum m a t r i x  However, t h e e f f e c t  2)  from  deforms p r i o r  f o r a given  that  deformation  results  the entire  plastically  deformation  temperature  composites  the fibre-matrix  irregularity  through  t h e aluminum m a t r i x  matrix  fracture  while  t o f a i l u r e . By  t h e amount o f minimized.  toughnes and h i g h  be c o n s i d e r e d .  reinforced  metal  applications composites  d i s c o n t i n u o u s and p a r t i c u l a t e  m a t r i c e s a r e used  i t i s suggested be i m p l i m e n t e d  strengthened  that  on  aluminum.  only futher  116  REFERENCES  1)  H u l l , D e r e k . An Cambridge  2)  Introduction  University  A g a r w a l , B . D . and Fibre  Press,  t o Composite 1981.  Broutman,L.J.  C o m p o s i t e s . New  A n a l y s i s and  York: Wiley,  3)  Aluminum V o l . I . e d i t e d  4)  Broek,David. Elementary Engineering  5)  ASM,  1985,  pp.  Andersson,C.H. pp.  1981.  personal  correspondence,  and Warren,R. C o m p o s i t e s ,  San  Diego,  1985. ( 1 ) , v o l . 15,  1984,  16-24. T e c h n o l o g y Review,  v o l . 5,  (2),  1983,  69-71.  Andersson,C.H. 2,  1967.  631-637.  Prewo,K.M. C o m p o s i t e s pp.  of  F r a c t u r e Mechanics. 3rd  and Muto,N. P r o c e e d i n g s o f ICCM 4,  7)  1980,  pp.  Tanaka,J.,  and Warren,R. P r o c e e d i n g s ICCM 3, P a r i s , v o l . 1129-1139.  Ichikawa,H.,  ICCM 4, Tokyo,  1982,  pp.  Okamura,K. and Matsuzawa,T.  Fukunga,H. and Ohde,T. i b i d ,  12)  Kohara,S.  pp.1443-1450.  P r o c s . J a p a n - U . S . C o n f e r e n c e on 1981,  Materials,  Tokyo,  Nakata,E.,  Kagawa,Y., T e r a o , H .  pp.  Composite  224-231.  2 6 t h J a p a n C o n g r e s s on M a t e r i a l 19-23.  Procs.  1407-1413.  11)  13)  Horn,  Kohara,S  Melvin Mettick.  10)  Van  Martinus N i j h o f f ,  6)  9)  R.  Performance  1980.  edition,  Calif.,  8)  Kent  Materials.  and Komori,M. P r o c s . Research, Kyoto,  of the  1983,  pp.  11 7 14)  Gigerenzer,H., 1978,  15)  pp.  P e p p e r , R . T . and  Lachman,W.L. P r o c s .  ICCM  2,  175-188.  K o h a r a , S . and  Muto,N. P r o c s .  ICCM 4,  Tokyo,  1982,  pp.1451-  1 455. 16)  Kohyama,A. and  Igata,N.  Procs.  ICCM 5,  San  Diego,  1985,  pp.  609-621 . 17)  J o h n Nadeau, p e r s o n a l c o r r e s p o n d e n c e ,  18)  Y a j i m a , S . , K i y o h i t o , 0 . , T a n a k a , J . and Material  19)  pp.  22)  1981,  pp.  Science  Letters,  15,  Hayase,T. J o u r n a l  of  3033-3038.  1980,  Hayase,T. J o u r n a l  of  pp.2130-2131.  Y a j i m a , S . , Okamura,K., Matzuzawa,T., T a n a k a , J . and Procs.  21)  16,  Y a j i m a , S . , K i y o h i t o , 0 . , T a n a k a , J . and Material  20)  Science,  1985.  Hayase,T.  Composites M a t e r i a l s Japan-U.S. Conf., Tokyo,  1981,  232-238.  I s e k i , T . Kameda,T. and  M a r u y a n , T . J o u r n a l of M a t e r i a l  Science,  1692-1698.  19,  1984,  S o u r c e Book on  pp.  Stainless  Steels.  ASM,  Metals  Park,  Ohio,  1976. 23)  Weinberg,F. Procs. Metals  of C o n f e r e n c e  on  Applied Metallurgy  T e c h n o l o g y , Warwick, C o n v e n t r y ,  England,  1980,  and pp.  131-136. 24)  Dieter,George Hill  25)  2nd  Edition.  McGraw-  M a t e r i a l Science  and  Engineering,  64,  1984,  171-181.  Arsenault,R.J. 1983,  Metallurgy  1976.  Arsenault,R.J. pp.  26)  Inc.,  E. M e c h a n i c a l  pp.67-71.  and  Fisher,R.M. S c r i p t a  M e t a l l u r g i c a , 17,  118 27)  Ashby,M.F.  Philisophical  M a g a z i n e , 14,  1966, p p .  28)  Tanaka,K. and M o r i , T . A c t a M e t a l l u r g i c a ,  18,  1157-1177.  1970, pp. 931-  941 . 29)  ASM  Handbook.  volume 8, 8 t h 30)  Warren,R.  Metallography,  S t r u c t u r e s and P h a s e D i a g r a m s ,  edition.  and A n d e r s s o n , C . H . C o m p o s i t e s ,  15,  ( 2 ) , 1984,  pp.101-111. 31)  Tom  Alden,  32)  Physics  personal  correspondence,  of S t r e n g t h and P l a s t i c i t y ,  H i r s c h , P . B . and H u m p h r e y s , F . J . pp.  1986. edited 189-216.  A l i S.  Argow,  119  APPENDIX  THERMODYNAMIC  C A L C U L A T I O N S FOR IN  THE  SOLID  A  FORMATION  ALUMINUM  OF  ALUMINUM  CARBIDE  120  Equations: 4 A 1 ( ) + 3C = A 1 C  -63330 + 22.72 x T  (cal/mol)  4A1( ) = 4A1( )  10320 - 11.04 x T  (cal/mol)  3 S i C = 3 S i + 3C  52380 - 5.49 x T  1  4  S  3  X  3SiC + 4 A 1 ( ) = A l C S  4  3  + 3Si  (cal/mol)  -630 + 6.19 x T  (cal/mol)  Non - S t a n d a r d C o n d i t i o n s : G = G° + RT x I n Keq K ***  e g  G  *** e q u a t i o n  = In  (aSi)  3  = -630 + (6.19 x T) + (5.961 x T x I n ( a S i ) )  used f o r c a l c u l a t i o n s  i n Figure  2.4  cal/mol  121  APPENDIX  DRUMWINDING  B  PARAMETERS  TABLE B.1  DRUMWINDING PARAMETERS  R e s i n B i n d e r : D e r a k a n e 411 Drum S p e e d : 325 rpm Comb S e t t i n g :  14.0  C r o s s Head S p e e d : 0.0 ( o n d i a l ) Roller  Pressure:  10.0 p s i .  1 23  APPENDIX C  TENSILE TEST DATA  124  TABLE  REFERENCE  SAMPLE  C.1  ALUMINUM T E N S I L E  THICKNESS  (mm)  WIDTH  (mm)  DIMENSIONS  AREA  (mm ) 2  37A  5.71  3.37  19.3  37B  5.97  3.88  23.1  43A  6.60  3.09  20.4  43B  6.18  3.07  19.0  42A  6.45  3.20  20.6  42B  6.55  3.15  20.6  42C  6.35  3.54  22.5  37D  6.35  3.54  22.5  TABLE  COMPOSITE  SAMPLE  C.2  TENSILE  e p (%)  Al p (Mpa)  31A  .37  55.8  6.3  23.8  15.8  31B  .33  54.1  5.9  23.7  14.7  31C  .17  47.1  -  26.3  31D  .23  50.3  -  25.4  31E  .42  56.9  7.8  25.0  18.4  36B  .38  55.8  6.9  21.9  16.7  36C  .34  54,7  7.8  24.8  18.5  36D  .58  60.4  5.7  24.6  14.5  38A  .51  59.0  7.1  19.1  17.0  38B  .49  57.7  8.2  18.2  19.2  38C  .41  55.8  5.7  22.9  14.2  38D  .41  55.8  9.4  22.1  21.9  39A  .46  62.0  9.9  20.7  23.8  39E  .4  60.0  12.6  20.6  28.9  C  C  FC (%)  DATA  AREA (mm ) 2  ds/de (Gpa)  126  TABLE C.2 c o n t . . .  45A  .25  53.0  17.0  45B  .35  54.8  16.6  45D  .25  53.0  17.9  46A  .38  58.9  13.2  20.7  28.5  46B  .41  59.6  10.7  21.5  23.8  46C  .36  58.7  19.6  46D  .29  55.4  20.8  41D  .49  61.8  9.9  19.8  22.5  44B  .37  57.3  8.1  19.8  20.1  44C  .46  60.9  8.4  19.4  19.6  44D  .47  61.2  9.6  19.0  21.9  47B  .35  57.0  14.2  20.5  32.0  TABLE  APPARENT  SAMPLE  C.3  FIBRE  VOLUME FRACTION (%)  STRENGTH  STRENGTH (Mpa)  31A  7.0  866  36B  8.7  692  38D  9. 1  904  39E  11.2  864  44B  7.7  885  44C  7.4  1 1 02  44D  8.4  913  46A  13.9  707  47B  11.9  81 1  APPENDIX ELECTRON  D  DIFFRACTION  PATTERNS  1 29  TABLE DIFFRACTION  PATTERNS  OF  Al C^, 4  D.1 SILICON,  GRAPHITE  CARBON  SAMPLE  RELATIVE INTENSITY  PLANE SPACING (A)  A1 C  100 62 62  1 .66 2.80 2.23  SiC  100 63 50  2.51 1 .53 1.31  Graphite  100 80 60  3.35 1 .68 1 .54  Carbon  100 27 16  2.06 1 .26 1 .08  100 60 35  3.14 1 .93 1 .64  4  Beta  3  Silicon  ,  B-SiC  and  

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