Kaiser Effects in Thermo-Acoustic Emissions from Carbon Fiber/Epoxy Laminates

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Kaiser Effects in Thermo-Acoustic Emissions from Carbon Fiber/Epoxy Laminates

Mr Jung-Heun Kim
Hanyang University
Department Of Mechanical Design
1271, Sa-1dong Ansan-Si
KYUNGGI-DO
425-791 KOREA.
email: nschoi@email.hanyang.ac.kr
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An investigation on nondestructive evaluation of thermal stress-induced damage in the composite laminates (3mm thick with various lay-up angles) has been preformed using thermo-acoustic emission technique. The analysis of Kaiser effect resulted in determination of the stress free temperature of composite laminates. The maximum temperature during the thermal cycles affected thermo-AE activities. Reduction of thermo-AE events during repetitive thermal load cycles was obviously shown. Failure occurrence and damage zone were observed using the optical microscopy, scanning electron microscopy and ultrasonic C-scan. The failure results agreed qualitatively with those obtained by three-dimensional finite-element thermal stress analysis. Short-Time Fourier Transform of thermo-AE signals offered the time-frequency characteristics which classified sources of thermo-AE and estimated the damage mechanisms of the composites.