Acoustic emission based method to characterise the damage modes in UD thin carbon/glass hybrid laminates

The aim of this paper is to investigate the relationship between the features of acoustic emission (AE) signals and the corresponding damage modes in S-Glass/carbon UD hybrid laminates subjected to tensile loading. The investigated laminates were fabricated by sandwiching thin carbon plies between translucent standard thickness glass plies to produce pseudo-ductility. The gradual damage mechanisms identified included fragmentation of the carbon fibre and delamination of the glass/carbon interface, which were observable due to the translucent glass layers. Since the damage modes were observable, it was possible to establish qualitative and quantitative correlations between these observed failure modes and the features of the AE signals. Based on our observations, two significant failure modes occurred during the tests: i) fibre failure, which was associated with the high energy and amplitude range of the AE signals and ii) delamination, which was related to the low energy and amplitude range. These results demonstrate that AE signals provide potentially useful information to characterise damage modes in hybrid laminates, which could be especially useful when the laminate is thick or opaque, or when the damage is too small to be visible. Further, these results could be developed into a method or protocol for assessing damage in hybrid laminates.