Acoustic Emission Characterisation of Failure Modes in Hemp/Epoxy and Glass/Epoxy Composite Laminates

Acoustic emission (AE) can be used for online monitoring of composite structures. One of the main issues of using composite structures in various applications is to understand and characterize their failure mechanisms. In this paper, advanced signal processing technique is used to discriminate the failure mechanisms in hemp/epoxy and glass/epoxy composite laminates. Hemp/Epoxy laminates are made from 4 layers of chopped non-woven fiber mats and glass/epoxy cross ply laminates [ 0/90/90/0](3s) are made from 12 layers of unidirectional glass fiber mats. ASTM standard specimens of size 100x20x4 mm were cut from the laminates. These specimens are subjected to flexural loading with AE monitoring. The choice of the AE signals for failure mode characterisation were obtained using parametric analysis of AE data such as counts rate and cumulative counts at different levels of loading. Wavelet decomposition was performed on the chosen AE signals to identify the percentage of energy and frequency content of each level which correlate the different failure modes. The studies reveal that wavelet decomposition of AE signals plays a significant role in discriminating the dominance of the different failure modes with respect to the different stages of loading.