Nondestructive Evaluation of Graphite/Epoxy Composite Damage

Abstract

<p>Ultrasonic and acoustic emission techniques were used to monitor and evaluate material damage in a graphite/epoxy laminate containing a machined hole as an initial flaw and subjected to fully reversed spectrum fatigue loading at room temperature. It was found that the flaw growth progressed radially around the initial hole at a uniform rate during cycling at the lower stress levels. At the higher levels, material damage accelerated dramatically, progressing faster in the transverse direction toward the free edges. By close examination of the A-scan and RF spectrum photographs, it was determined that damage modes could be defined as to their extent and relative location within the specimen. These conclusions were supported by photographs of the failed specimen.</p>