Revisiting multi-phase field model for FRCs using Puck theory

This article aims to revisit the multi-phase field model using the Puck failure criteria for Fiber-Reinforced Composites (FRCs). Specifically, this work proposes a robust multi-phase field formulation relying on the Puck failure criteria for triggering the fracture in fiber and the inter-fiber (matrix-dominated) separately, using two independent phase-field damage variables in a thermodynamically consistent framework. Furthermore, the formulation encompasses two distinct characteristic length scales, and a structural tensor is employed to penalize the gradient of the phase field, enhancing the accuracy of qualitative and quantitative predictions. Seven benchmark examples of unidirectional reinforced composites are utilized to demonstrate the model's predictive capabilities. The first four examples compare the proposed model with experimental results stemming from the related literature. In particular, the crack propagation with different fiber orientations, including the extreme cases involving fiber orientated parallel to the loading direction leading to debonding along the matrix and fiber interface are presented for each case. Furthermore, the last three examples serve as benchmarks to further validate the model's predictive capability. The unnotched tension specimens are examined to evaluate the effects of defects/voids on crack propagation in the FRCs in various ply orientations.