Abstract

Acoustic emissions (AE) generated by a structure under stressed condition provide a passive method to understand the flaw growth phenomenon. In complex structures, such as composites, characterisation of AE signals generated by various failure mechanisms enhances such understanding. Sample level tests have been carried out on carbon epoxy unidirectional laminate in longitudinal direction of fiber to study the AE characteristics of different failure mechanisms, namely,  fiber breakage and inter layer de-lamination. The AE parameters such as amplitude, energy, duration, rise time and signal strength have been acquired and analysed using various correlation plots. The fiber breakage is represented by high energy and longer duration hits with an amplitude of above 90 dB. The de-lamination mechanism is producing AE hits of medium energy of about 1000 units and long duration up to 106 µs. The duration per unit energy and the rise time per unit energy graphs portray a vivid picture of the occurrence of fibre breakage and delamination.

Key words: Carbon-epoxy composites, failure modes, acoustic emission (AE).