Composite materials exhibit complex failure behavior under impact loading especially such as that for composite landing gear structure. Possible failure modes in composites may include matrix cracking, fiber breakage, kinking, fiber-matrix debonding or delamination between composite plies. In order to better understand the damage mechanisms and non-linear response of composite structures under impact, complex geometries, materials, ply orientations and stacking sequence need to be considered. However, general drop test analysis for composite structures usually takes a lot of computational efforts, and it may be even more expensive for failure analysis and optimization when various structural geometries and design configurations are taken into account. This paper proposes a new methodology for evaluation and optimization of failure behavior of composite structures subjected to impact loading, whereby drop test analysis of composite structures is modeled by explicitly dynamics analysis of two-dimensional structures and implicit analysis of three-dimensional solid structures to predict delamination or out-of-plane failure. The above-mentioned modeling strategy helps speed up the optimization process and considerably save computational time and efforts. The proposed methodology together with reliable optimization algorithms and failure theory criteria are integrated and coded into a FE optimization tool by Python script. It is shown that the optimization tool effectively helps engineers and researchers perform optimization of general composite structures and fully take into account of various geometries, materials, loading configurations, composite stack-up and sequences and individual ply's orientation. (C) 2013 The Authors. Published by Elsevier Ltd.
