Challenges in Predicting the Energy Absorption of Composite Materials under Axial Crush Loading

The development of robust numerical approaches, which are capable of capturing the damage and failure mechanisms of materials and structures that are subjected to crash and impact loading, is crucial to support the design and certification of lightweight crash-worthy aircraft components. The significant increase in computational power over the last few years has enabled the use of numerical tools to investigate design optimizations for safety-critical structural applications. In particular, the prediction of the progressive damage and energy absorption of composite materials is a key issue for crash-worthiness of aircraft structures. In this study, we compare and investigate the limitations of three different material models that are based on the general framework of Continuum Damage Mechanics theory and implemented within the two commercial finite element software packages, ABAQUS and LS-DYNA. Starting with single element simulations and moving up the structured building block approach for calibration and validation purposes, the material models are applied to simulation of flat coupon and tube crush tests, which are representative configurations for the two major failure modes during axial crushing of fibre-reinforced polymer composites; namely, splaying and fragmentation. Fundamental modelling concepts such as mesh orientation and mesh size sensitivities as part of the simulation strategy are also considered in this study as they have an impact on the quality and reliability of the simulation results. Finally, modelling guidelines are provided for computationally robust and efficient simulation of axial crushing of composite structures.