Detection of Failure Progression in Cross-Ply Graphite/Epoxy during Fatigue through Acoustic Emission. Volume 1.

摘要

The applicability of the acoustic emission (AE) technique to detect and locate damage initiation, monitor its progression and accumulation and to identify the major modes of damage associated with the failure process in cross-ply AS4/3502 graphite/epoxy laminates has been investigated. Six pairs of different laminate configurations were studied, having different stacking sequences and containing different ratios of ply thickness. Each pair included one laminate with external 90 deg plies and one with external 0 deg plies, e.g. (902/02/90)s, and (02/902/0)s, respectively. The testing program included determination of mechanical properties and monitoring of failure mechanisms and processes using optical observations, X-radiography, deplying, and scanning electron microscopy. Special efforts were directed toward establishing a correlation between the failure process and the AE results. Acoustic emission was monitored during quasi-static loading to failure in all cross-ply laminates. Results indicate that stacking sequence strongly affects the events intensities, e. g. amplitude energy, duration, and counts per event. Also, stacking sequence has a significant effect on damage initiation load and on rate of damage accumulation. Composite Materials, Acoustic Emission, Acousto-Ultrasonics, Fatigue, Damage Mechanics, Damage Accumulation.