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UBC Theses and Dissertations

Efficient methods for non-linear thermochemical analysis of composite structures undergoing autoclave processing Rasekh, Ali


Composite structures are increasingly being used in different industries. Their manufacturing imparts some challenges for the industry: most importantly prediction and control of the process to specification. The usual numerical solutions typically based on the use of the finite element analysis are not very suitable for large parts, especially when there is a need for quick estimation of the results for preliminary design and optimization. Therefore, there is a need both to have enhanced solutions that reduce the modeling effort for computer simulation of large and complex structures and also to simplify the solution and provide easy to use methodologies for quick estimations based on tables and charts. In the present work, a simple methodology is developed to estimate the temperature distribution in a thermoset polymer matrix composite slab placed on a tool and subjected to cycles of temperature ramp and hold leading to the curing of the composite and generation of heat due to the internal chemical reactions. Supplementary diagrams are also generated to set limits on the method. A modified finite element solution for heat transfer is also introduced that reduces the mesh generation and computational effort. This "higher order shell element" uses enhanced shape functions and efficient methods for spatial and temporal integrations in order to reduce the computational run times. The developed methods provide the design engineer with efficient analysis tools for predicting the temperature in a composite part. The simple diagrams and tables can be used for preliminary estimation of the temperature distribution in the part at each stage of the material development. The enhanced finite element methodology developed here can be used to reduce the amount of effort necessary in mesh generation and refinements necessary to achieve accurate solutions for thermochemical modelling of complex composite structures during processing.

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