Acoustic emission from the tension fatigue of glass fibre reinforced plastics

Abstract

This work investigates acoustic emission (AE) generated during tension fatigue tests carried out on a glass fibre reinforced plastic (GFRP) composite specimen. Continuous acquisition of AE events during measurements enables mapping of AE events with fatigue cycle time. The results allow analysis of the event rate obtained during parts of the fatigue cycle so that crack propagation events, at the peak of each load cycle, and crack closure events, on the unloading stage of each cycle, can be identified. The event rate in each of these parts of the cycles is also examined with respect to various test parameters, and qualitative results are shown that suggest some distinct correlations between event rate and crack length. The results can be applied as a diagnostic technique for modelling cumulative composite damage in critical composite structures such as pressure vessels and machine structures. The crack closure event rate is strongly correlated to crack length. The results can be used without the need to consider more sophisticated AE parameters in the design of a composite damage monitoring system.