Predicting the relative magnitude of interlaminar stresses due to edge effects in thin angle-ply laminates using macroscopic finite element modeling

Carbon-epoxy and other composite materials are widely used in the design of aircraft and other structural components, but can be susceptible to delamination at free edges due to the presence of out-of-plane stresses. Finite element (FE) modeling can be used to predict the magnitude and location of these edge stresses, but the often used macroscopic approach to representing laminates can result in predictions that vary considerably due to the numerical singularities that are created. In this study, two macroscopic FE approaches are tested for thin angle-ply laminates in tension, and recommendations are made for the most effective method for evaluating the edge-effect phenomenon early in the design process. It has been determined that perfect interface models cannot be used for predicting maximum interlaminar stresses at free edges. Perfect interface models can effectively predict the relative magnitude of the interlaminar shear stress, τxz but resin interface models must be used for the interlaminar normal stress, σz.