CONTINUOUS HEALTH MONITORING OF GRAPHITE EPOXY MOTORCASES (GEM)

摘要

Following the explosion of Delta 241 (IIR-1) on January 17th, 1997, the failure investigation board concluded that the Graphite Epoxy Motorcases (GEM's) should be inspected for damage throughout their life and just prior to launch. Subsequent investigations and feedback from to launch. Subsequent investigations and feedback from industry led to an Aerospace Corporation recommendation to instrument the entire fleet of GEM's with a health monitoring system. The period of monitoring would extend from the initial acceptance resting through final erection on the launch pad. There is an increasing use of composite materials in aircraft, automobiles, military hardware, and aerospace components and there is a sizable need for composite health assessment measures particularly for the detection of damage from impacts and other sources of high mechanical and thermal stresses. Even low-momentum impacts can lead to "barely visible impact damage" (BVID), corresponding to a significant weakening of the composite. This damage, undetectable by visual inspection, can in turn lead to sudden and catastrophic failure when the material is subjected to a normal operating load. The results presented here contributed significantly to the understanding of the acoustic properties of the GEM casing, and make a substantial advancement in the theoretical phase of the source location algorithm development.