QUANTITATIVE ASSESSMENT OF DAMAGE GROWTH IN GRAPHITE EPOXY LAMINATES BY ACOUSTO-ULTRASONIC MEASUREMENTS.
Additional Document Info
Composite materials fail by a complex development of many different damage modes, including matrix cracking, fiber-matrix debonds, delamination and fiber breakage. Nondestructive testing of composite materials must therefore concern itself with something other than the detection and geometrical location, sizing and orienting of single cracks. The acousto-ultrasonic techniques, developed by Vary, et al. , has the potential to respond to the development of damage states and to provide a quantitative parameter which monitors this damage development. This paper presents some preliminary data taken during quasi-static loading and fatigue of graphite epoxy laminates which indicate the plausibility of this statement. The ultrasonic signals received from transducers were amplified, digitized and stored in computer for later spectral analysis. A Fast Fourier Transform algorithm was used to perform spectral analysis. It is shown that the acousto-ultrasonic test is capable of sensitively monitoring the development of damage in graphite epoxy laminates.