7. Non Metallic NDE, Acoustic Microscopy
Ultrasonic and acoustic emission techniques were used to monitor flaw growth in graphite/epoxy laminates containing four types of initial flaws and subjected to fully reversed spectrum fatigue loading, including temperature and moisture variations. In general, it was found that flaw growth was much more pronounced in the specimens exposed to environmental fluctuations in addition to the load spectrum, than in those tested in an ambient environmenc. Flaw growth was also greater in specimens of [(0/+45/90)s)2 layup than in those of [02/+45]2s layup. No significant reduction in residual tensile strength (in general less than ten percent) was observed for any of these groups of specimens.
Daniel, I. M.; Schramm, S. W.; and Liber, T., "Nondestructive Monitoring of Flaw Growth in Graphite/Epoxy Laminates Under Spectrum Fatigue Loading" (1980). Proceedings of the DARPA/AFML Review of Progress in Quantitative NDE, July 1978–September 1979. 35.