6 - Multi-scale modelling of cracking in cross-ply laminates

Abstract

Publisher Summary Cross-ply laminates demonstrate a broad variety of failure mechanisms at different scales. Several of these mechanisms are not linked to an instantaneous fracture event of the entire component/structure but result in deterioration of the load-bearing capacity of composite materials. Application of tensile fatigue to cross-ply composites results in matrix-crack initiation at very early stages of their service and, in many cases, at stress levels below the one necessary for the first-crack formation under static loading conditions. With an increase in the number of cycles, the density of matrix cracks grows up to a certain saturation level, known as the characteristic damage state. Matrix cracking in cross-ply laminates under fatigue conditions was extensively studied experimentally using mainly the edge replication technique, X-ray radiography or direct observations of cracking in transparent glass-epoxy laminates. It was found that matrix cracking in cross-ply laminates is not the immediate cause of the global failure of a laminate. It affects the longitudinal stiffness of composites, to a greater extent—glass/epoxy laminates as compared to carbon/epoxy ones; which has been explained by the higher transverse ply stiffness of the former group.