Numerical study of interfiber ligament failure of composites wth ductile bulk matrices

Debonding of fiber/matrix interfaces, kinking on debonded matrix surfaces, and tearing of interfiber ligaments are three major failure modes in micro-scales often observed in the failure experiments of Fiber Reinforced Composites (FRC) under extreme transverse tensile loadings. Numerical simulations on these complex failure processes at micro-scales are critical for designing new FRC materials. However, it is difficult to simultaneously simulate all these failure modes especially for cases where bulk matrix materials are ductile and undergo large plastic deformation. To overcome this difficulty, we adopt an innovative DG-based interface-oriented finite element technique that is able to handle all three failure modes. In this paper, using this numerical technique, we successfully simulate a complete failure process characterized by all three fracture modes for a composite structure containing two fibers embedded in a ductile bulk matrix. Furthermore, the kinking of debonded matrix surfaces predicted from simulations agrees well with the experimental results. Finally, we have studied the impact of variation in the thickness of interfiber ligaments on the failure behaviors of FRC materials. By running four cases with varied ligament thicknesses, we have identified a beam-like mixed bending/shearing failure mode for the tearing of interfiber ligaments and the shearing influence on the failure may increase following the increase in ligament thickness.