A strain-rate dependent micro-mechanical model with progressive post-failure behavior for predicting impact response of unidirectional composite laminates

A new micro-mechanical model is developed to predict the behavior of unidirectional polymer matrix composite laminates under impact loading conditions and implemented in the non-linear finite element software LS-DYNA. This model accounts for the progressive post-failure behavior and strain-rate dependency of polymer matrix composites making it suitable for impact simulations. A continuum damage mechanics (CDM) based failure model is used to incorporate the progressive post-failure behavior. A set of Weibull distribution functions are used to quantify damage evolution and corresponding reduction in stiffness in different modes in the fibers. Similar functions based on strains are used for the resin. Fiber breakage is assumed as the only ultimate failure mode. In addition to these micro-failure modes, delamination, which is a macro-level failure, is also incorporated using an approach developed earlier for a ply-level progressive failure model. Strain-rate dependent behavior is incorporated by assuming viscoplastic constitutive relations for the resin. Additionally, the in-plane shear modulus of the fiber is also assumed to be rate dependent. Experimental results available in the literature are used to validate the model’s predictions.