Gradual failure in high-performance unidirectional thin-ply carbon/glass hybrid composites under bending

Abstract

This paper introduces new composite architectures using carbon and glass fibre-reinforced epoxy prepregs to achieve gradual failure under bending. The concept is based on a technique developed by the authors to design hybrid composites with gradual failure in tension combined with beam theory to identify and control the failure sequence of the plies in the layups. Two layups are designed based on standard ply thickness S-Glass and hybrid sub-laminates made out of intermediate and high modulus thin-ply carbon prepregs. The layups are tested under 4-point bending loading where a gradual failure alongside high values of flexural displacement are achieved. No catastrophic failure is observed throughout the whole loading process. The gradual layer-by-layer failure of the surface layers on the tensile side produces a brush-like appearance. Microscopy observations from interrupted tests verified fragmentation of the high-modulus carbon layer followed by gradual failure of the intermediate modulus carbon layer and delamination on the tensile side, as well as stable shear cracks of the high-modulus carbon layer on the compression side.