Acoustic emission characterization of damage accumulation during early creep stage in E glass fiber fabric/epoxy laminates
Uenoya Toshiyuki
Abstract:In this paper, the residual life and the creep damage for glass fiber reinforced plastics are studied experimentally. For this purpose, emphasis is placed upon introducing a new damage parameter defined by acoustic emission (AE) intensity in order to evaluate the micro-damage accumulation generated before macro-crack initiation in a composite. Short term creep experiments were carried out on three types of specimens, consisting of glass fiber fabric reinforced epoxy laminated composites with different weaves, counts, densities and thickness. The single-edge notched specimens were subjected to a series of stepwise loadings with increasing peak loads, in edgewise four point bending so that tensile stress arose at the front end of the notch. AE activity was monitored with measuring mechanical displacement during a test using various AE intensities, which were analyzed in detail. The new damage parameter showed a good correlation with a conventional damage parameter defined by non-elastic deformation caused during cyclic load holdings. The correlation depended on test conditions and materials but was presumed to stand up under tensile deformation. Key Words:creep damage, short-term creep, residual life, damage parameter, acoustic emission, glass fiber reinforced plastics