Fracture toughness and bridging law of 3D woven composites

In the paper, the methodology of measuring G(1c) by using DCB specimens in the presence of large-scale bridging is adapted for investigating the delamination in 3D woven composites. The main novelties introduced in the DCB testing concern a) the loading device, b) the specimen geometry, c) the measurement scheme, and d) the determination of G(1c) and the bridging law from experimental data. The geometry-independent material characteristic G(1c) as a function of the initial crack opening displacement (ICOD) is introduced. Typical values of the delamination fracture toughness of 3D glass and carbon composites are presented.