3D Modelling of Impact Failure in Sandwich Structures

Abstract

Cohesive theories of fracture are applied to simulate the complex failure modes in sandwich structures subjected to low-speed impact. The particular configuration contemplated in this study refers to the experiments performed by Xu and Rosakis [1], where the model specimens involving a compliant polymer core sandwiched between two metal layers, were adopted to simulate failure evolution mechanisms in real sandwich structures. Fracture has been modeled by recourse to an irreversible cohesive law embedded into three-dimensional cohesive elements. These cohesive elements govern all aspects of the separation of the incipient cracks. The cohesive behavior of the material is assumed to be rate independent and, consequently, all rate effects predicted by the calculations are due to inertia. The fidelity of the model has been validated by several previous simulations [2,3]. The numerical simulations have proved highly predictive of a number of observed features, including: the complex sequences of the failure mode, shear-dominated inter-sonic (a speed that is greater than shear wave speed but less than the longitudinal wave speed of the material) inter-layer cracks, the transition from inter-layer crack growth to intra-layer crack formation and the core branching later on.