ACOUSTIC EMISSION CHARACTERIZATION OF A GLASS-MATRIX COMPOSITE

Abstract Acoustic emission (AE) analyses have been performed on a high compliance, high failure strain randomly oriented carbon reinforced glass matrix composite. The composite exhibits a unique nonlinear stress-strain behavior with high failure strain during both uniaxial tensile and flexural testing. The extensive matrix cracking of this material during loading provides an excellent opportunity to study the fracture mechanism. In this study, two types of composites using similar constituents but different processing procedures resulting in different mechanical behavior, were studied. One composite showed a very pronounced non-linear stress-strain behavior during tensile testing. The curve consists of an initial linear portion, followed by a deviation from linearity and a large amount of longitudinal strain is produced with very little increase in the stress. The second composite did not show similar behavior with the slope of the stress-strain decreases continuously. The apparent different mechanical behavior of the two composites provided an excellent opportunity to use the AE characterization to distinguish two different fracture processes. This study concentrates on monitoring damage initiation and damage progression during tensile and flexural testing using acoustic emission sensors. Detailed examination of AE characterization, including cumulative AE events, event occurrence and its rate as a function of load, and amplitude distribution histograms of events at different load levels, reveals a different emission activities during tensile and flexural loading conditions, indicating different fracture patterns. The examination of amplitude distributions at various loads revealed that the method is sensitive enough to distinguish various fracture processes.