Acoustic Emission Monitoring of Interlaminar Delamination Onset in Carbon Fibre Composites

This article presents the development of an experimental methodology based on acoustic emission wave detection for determining delamination onset and propagation in carbon fibre composite materials under quasi-static and fatigue loading. Delamination was investigated in quasi-static interlaminar fracture testing over a wide range of mixed-mode ratios (GII/GT = 0, 0.3, 0.5 and 1) for unidirectional and woven samples. An acoustic emission wave detection method was developed to detect delamination onset, and the corresponding fracture toughness was computed. Interlaminar fracture toughness was also calculated by beam theory and from finite element analysis with the virtual crack closure technique. The mechanical testing results, acoustic emission monitoring and numerical model’s interlaminar fracture toughness were used to define delamination initiation criteria by drawing two-dimensional envelopes corresponding to GC = f(GII/GT). The acoustic emission wave detection method showed damage accumulation before ...