Dynamic Mode I and Mode II crack propagation in fiber reinforced composites

Dynamic crack phenomena in unidirectional composite laminates are investigated. The proposed formulation is based on the combination of beam and interface methodologies, which are utilized to predict crack behavior in the context of the steady state fracture mechanics. The relevant quantities related to delamination phenomena are discussed with reference to Lagrange and penalty methods utilized to simulate the connection between the sublaminates adjoining the delamination plane. Analytical solutions of the governing equations are proposed and closed form expressions for simple cases, involving pure mode I and mode II components, are provided. The accuracy of the proposed approach is validated through comparisons with results arising from continuum analysis obtained by finite element procedures. Some applications are developed to point out the influence of the crack front speed, the shear deformability and the inertial contributions on the energy release rate. The main features of the proposed model are investigated in the context of an energy balance approach based on the J-integral formulation and thus providing results useful to model delamination growth for simple cases involving pure mode I and mode II loading conditions. Special attention is devoted to analyzing the allowable 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.