Evaluation of Microfracture Due to Stress Corrosion of Particulate Glass Composite by Acousitc Emission

Abstract

Acoustic emission method is useful for the characterization of the mechanical reliability of the materials controlled microfracture. We can detect the microcrack occurred in the brittle materials by using acoustic emission method. In our study, we tried to evaluate the change of microfracture due to stress corrosion of alumina particulate glass composite. Stress corrosion of glass causes a decrease in strength and fracture toughness. Alumina particulate glass composite is also subject to the influence of stress corrosion. The strengthening by the precipitation in addition to the particle has been tried, but the effect of precipitation is not clear. We measured AE signals of alumina particulate glass composite during the four point bending test in air, vacuum and water.

In the case of the non-precipitated material, we observed concentrated AE just before the break point in air. We observed dispersed AE in vacuum. However, we also observed dispersed AE in air in the case of the precipitated material and these microfracture processes were almost same in vacuum. It can be explained that the precipitation at the interface between alumina particle and glass matrix changed the unstable crack extension due to stress corrosion, which corresponds to concentrated AE, to the stable crack extension, which corresponds to dispersed AE. As a result, the precipitated material has also the higher strength and fracture toughness than the non-precipitated. Therefore we could clearly find the change of microfracture due to stress corrosion by acoustic emission method. Acoustic emission method is a good technique for the evaluation of the mechanical reliability against humidity in particulate and precipitated glass composite.