Acoustic emission characterization of the fracture mechanism of a high compliant, glass-matrix composite

Abstract

Reinforcing brittle glass-matrix with discontinuous carbon fibers provides a high compliant, high failure strain glass-matrix composite with a unique non-linear stress-strain behavior for both uniaxial tensile and flexural testings due to the extensive matrix cracking. The tensile strength of this material was less than that of the flexural test. The difference could be attributed to the shift of the neutral axis of the beam during flexural loading due to the matrix cracking. An analytical model was established to describe the mechanical response of the composite. Acoustic emission (AE) analyses were performed on this material during both tensile and flexural testings to study the damage initiation and progression. Data recorded included cumulative AE events, counts, and count rates as a function of load, and amplitude distribution histograms of events at different load levels. It was shown that the acoustic emission signal patterns were very different during tensile and flexural loading conditions, indicating different fracture patterns. The examination of amplitude distributions at various loads revealed that the method was sensitive enough to distinguish various fracture processes.