Ply-Blocking Phenomenon and Hole Size Effects in Modeling Progressive Damage in FRP Laminates

This work presents a 3D progressive damage model based on Puck's failure theory and linear damage evolution in FRP laminates. It includes shear non-linearity, in-situ strengths, equivalent stress-strain, and mixed-mode fracture energy and implemented in Abaqus/explicit through VUMAT subroutine. Various test cases were performed to validate the model and demonstrate its applications. The shear non-linearity test shows that transverse compression retards matrix micro-cracking while transverse tension accelerates it. The open hole tension (OHT) test of laminates shows that delamination initiates around the holes and free edges, spreads the most, and propagates in different directions at different interfaces. Later, inter-fiber damage in 45' or -45' plies initiates and spreads at a slight inclination to the tip of the hole. Lastly, fiber damage in 0' plies initiates at the tip of the hole, spreads the least, and propagates perpendicular to the loading direction. The ply-blocked laminates show around 30% higher strength and fracture strain than non-ply-blocked laminate due to delay in damage propagation, and are less sensitive to hole size. Accordingly, their OHT strength reduces by 14.3% as opposed to 21.14% in the non-ply-blocked laminates, when the hole size increases from 6 to 9 mm. The damage location, magnitude and propagation modes were corroborated with experimental findings in literature.