Axial crush of composite tube is a benchmark problem for the crashworthiness prediction capability for composite structures. This paper discusses the challenging issues in constitutive modeling specific to braided composite tube crash simulations and compares composite tube crash simulations using LS-DYNA with an existing composite damage material model MAT58 and with an improved user defined composite damage material model CODAM. Axial crush of composite tube is a benchmark problem for the crashworthiness prediction capability for composite structures. This paper discusses the challenging issues in constitutive modeling specific to braided composite tube crash simulations and compares composite tube crash simulations using LS-DYNA with an existing composite damage material model MAT58 and with an improved user defined composite damage material model CODAM. Braided composite tubes form continuous fronds in axial impact testing. The material in fronds experience unloading when moving out of the crush front. It is important to correctly represent the unloading response of the damaged material. Our previous work revealed that MAT58, an existing composite damage model in LS-DYNA, did not correctly represent the subsequent unloading response of the compressively damaged composite braids. To address the issue, an analog model was developed at the University of British Columbia and implemented in CODAM, a user defined composite damage model for LS-DYNA. This paper compares the braided composite tube crush simulations using LS-DYNA with MAT58 and the improved CODAM model. Simulations with CODAM generated realistic crush morphologies and good agreements with the experimental force-displacement responses and Specific Energy Absorption (SEA) values.
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