UBC Theses and Dissertations
Acoustic emission and mechanical properties of particle reinforced composites Godoy, Ana Esmeralda
Fracture and acoustic emission (AE) tests were performed on alumina particle-filled epoxy and alumina particle-filled martensitic steel composites. The ring-down counting method was used to measure AE. Three-point bending tests were carried out for the martensitic steel composites and AE was recorded during the fracture test. The alumina appeared to have little effect on the AE from martensitic steel. The elastic modulus and AE attenuation of the alumina particle-filled epoxy composites were analyzed. The elastic modulus and AE attenuation of the epoxy composites were independent of the average alumina particle size. The elastic modulus increased with increasing alumina volume fraction and the AE attenuation decreased slightly with increasing alumina volume fraction. Double torsion, wedge-loading and three-point bending fracture tests were carried out for the alumina-reinforced epoxy composites. AE was recorded during each fracture test. The fracture energy and toughness values-increased with increasing volume fraction and were independent of the particle size. The increase in fracture surface due to the presence of particles accounted for about 60% of the increase in fracture energy. Crazing seemed to be the major source of AE in pure epoxy. During failure of the composites the AE increased with increasing particle size. A cut-off value in particle size at about 40 μm appears to exist, below which no increase in AE occurs with the addition of particles. For intermediate alumina volume fractions a maximum was observed in AE versus volume fraction curves. The pinning and release of the crack front due to the presence of hard particles appeared to be the major contributing factor to the AE of the epoxy composites.
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