LASER-INDUCED FLUORESCENCE IMAGING OF THERMAL-DAMAGE IN POLYMER MATRIX COMPOSITES

A simple, fluorescence based imaging system has been developed that is capable of identifying regions of thermal damage in polymer matrix co mposites (PMCs). These materials are playing an increasingly important role in the production of high performance vehicles and air-craft, wh ere their low weight and high mechanical strength, combined with advan cements in manufacturing technology ensure increased use for a variety of applications. Of particular concern in the aerospace industry is t he tendency of some PMC materials to become irreversibly damaged when exposed to elevated temperatures. Traditional nondestructive testing ( NDT) techniques are capable of defecting physical anomalies such as cr acks and delaminations but cannot detect initial heat damage, which oc curs on a molecular scale. Spectroscopic techniques such as laser indu ced fluorescence provide an attractive means for detecting this type o f damage and are amenable to imaging large, irregularly shaped surface s. In this report we describe instrumentation capable of rapidly detec ting thermal damage in graphite epoxy components and suggest improveme nts which will enable this technology to make quantitative judgments c oncerning the mechanical strength properties of heat damaged specimens .