Mixed mode dynamic delamination in fiber reinforced composites

An investigation on dynamic delamination problems under steady-state crack growth is proposed. Through the thickness delamination phenomena in unidirectional composite laminates are analyzed in the context of the interface methodology, based on the combination of shear deformable beams and interface elements. Analytical solutions of the relevant governing equations are proposed and closed-form expressions for simple cases, involving pure mode I and mode II components, are provided. Moreover, analytical expressions for mixed mode loading conditions regarding the energy release rate modal components are given in terms of beam stress resultant discontinuities, emphasizing the presence of new terms, absent in the static case, which arise from the inertial description of the composite structure. Comparisons between analytical and numerical results show the accuracy of the proposed formulation. Some applications are developed to point out the influence of the crack front speed, the shear deformability, the inertial contributions on the energy release rate and the corresponding mode partition. Special attention is devoted to analyze the maximum speeds of the moving crack. In particular, a parametric study in terms of the main characteristic geometric parameters of the laminate is proposed to show the main features of the crack tip behavior.