Bending mode fracture toughness of geometrically nonlinear thin-ply composite shells

Abstract

This paper presents a method to determine the bending mode fracture toughness of thin-ply composite laminates. Single-edge notch samples are tested using a recently developed compression–bending fixture in the geometrically nonlinear regime until failure. The fixtures impose large bending curvatures at the notch tip and the corresponding moment vs. curvature response is obtained. Post-mortem micro-CT images show the details of the quasi-brittle fracture process zone. The experimental results and micro-CT images of the process zone are combined with the numerical virtual crack extension method to measure the critical energy release rate of the laminate structure, based on a detailed representation of the fracture process zone. The results are presented for a specific cross-ply laminate, but the procedure can be extended to other material systems under large curvature loads.