On microscopic analysis of fracture in unidirectional composite material using phase field modelling

The demand for composite materials is higher than ever before. Effective and reliable modelling techniques allowing for better understanding of their failure are critical for designing future optimised light-weight structures. However, failure of composite at the microscopic level is a complex phenomenon and it has often been analysed using empirical approaches. A promising alternative, that instead takes a physics-based approach, is the phase-field model (PFM). This approach has been applied comprehensively to homogeneous materials and has briefly been extended to composite laminae, as modelled by Kanninen's local heterogeneous region (LHR). Despite this progress, a systematic investigation of the implications and requirements of using PFM for studying fracture in composite materials seems incomplete and missing links between the physical and the numerical aspects. This work aims to fill that gap and discusses in detail the role of the critical parameters in a PFM analysis of fracture, including length-scale interactions and concerns on convergence. The present analysis is framed around the problem of toughening of composites by weakening the matrix/fibre interface. Here, the PFM proves very efficient tool allowing recognition of multiple failure modes.