A phase–field model for fracture of unidirectional fiber–reinforced polymer matrix composites

This study presents a crack phase-field approach for anisotropic continua to model, in particular, fracture of fiber-reinforced matrix composites. Starting with the variational formulation of the multi-field problem of fracture in terms of the deformation and the crack phase fields, the governing equations feature the evolution of the anisotropic crack phase-field and the balance of linear momentum, presented for finite and small strains. A recently proposed energy-based anisotropic failure criterion is incorporated into the model with a constitutive threshold function regulating the crack initiation in regard to the matrix and the fibers in a superposed framework. Representative numerical examples are shown for the crack initiation and propagation in unidirectional fiber-reinforced polymer composites under Mode-I, Mode-II and mixed-mode bending. Model parameters are obtained by fitting to sets of experimental data. The associated finite element results are able to capture anisotropic crack initiation and growth in unidirectional fiber-reinforced composite laminates.