A phase field approach for ductile fracture of short fibre reinforced composites

Fracture events in short fibre reinforced polymer (SFRP) composites are one of the most limiting phenomena for their widespread use in many engineering applications, especially involving lightweight structures. In this investigation, a novel phase field model that accounts for the anisotropic response of SFRPs is outlined from the theoretical and numerical standpoints. The regularized crack surface functional, which characterizes phase field methods, allows overcoming operative difficulties for complex crack topologies in engineering structures. In particular, we exploit an invariant-based phenomenological elasto-plastic material model for the macroscopic response of SFRPs with pressure-dependent behaviour that is consistently coupled with the phase field approach for ductile fracture. The anisotropic character of SFRPs is incorporated into the elasto-plastic and the fracture response. In contrast to previous investigations on the matter, one novel ingredient of the proposed formulation is the use of non-associative anisotropic plastic evolution. The current variational formulation also exploits a modular format with a consistent generalization of the crack driving function for SFRPs. The performance of the current modelling approach is examined by means of representative applications, showing its robustness and reliability.