UBC Theses and Dissertations
Simulation of progressive damage development in braided composite tubes under axial compression McGregor, Carla Jane
Composite materials have recently been investigated as an attractive alternative to traditional materials used as energy absorbers in the automotive industry. One of the factors inhibiting the implementation of these lightweight energy absorbers is the lack of accurate, robust, and physically meaningful material models capable of simulating damage growth in composite materials under a variety of applied loads. A plane-stress continuum damage mechanics based model for composite materials, CODAM (COmposite DAMage), recently developed at the University of British Columbia (Williams, 1998; Williams et al., 2003; Floyd, 2004) has proved to be capable of predicting the complete tensile behaviour of composites from initiation of damage to complete failure. The current study focuses on extending the model to capture the complete compressive response of composite materials as well as their behaviour under load reversals. Refinements to the model are based on the experimentally observed compressive failure mechanisms presented in the literature. In particular, the mechanical consequences of kinking and kink band broadening, in conjunction with matrix cracking and delamination, are represented in the model. The model parameters defining the compressive response are related to experimentally observed behaviour, thus maintaining the physical basis of CODAM. These improvements contribute to the development of CODAM as a predictive tool in the analysis of gross damage growth in composite materials. To demonstrate the capability of the model, the predicted response of braided composite panels under tensile loads, compressive loads and load reversals are compared to experimentally observed behaviours. The model is also evaluated on its ability to predict the damage propagation and energy absorption in axial crushing of braided composite tubes. Model predictions for both panel and tube specimens correlate well with the experimental results. The successful tube crushing predictions suggests that CODAM could offer an attractive design aid for the future incorporation of lightweight composite energy absorbers into crashworthiness structures.
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