Application of ultrasonic spectroscopy for hydrolytic damage detection in GRFC: Correlations with mechanical tests and microscopic observations

This study concerns the ability of ultrasonic waves to detect the damage ca used to polymer composites during water immersion. The acoustical parameter s such as velocity and attenuation are linked to the viscoelasticity and mi crostructure of the propagation medium. For ultrasonic propagation, composi te materials are dispersive, so their acoustical parameters are measured by means of pulsed ultrasonic spectroscopy. Model samples with certain properties are chosen in order to isolate the di fferent damage mechanisms. In these conditions, the results of ultrasonic t ests during hydrolytic aging allowed us to correlate the evolution of acous tical parameters to the damage level and nature. The ultrasonic results have been validated by complementary mechanical test s and microscopic observations carried out on the same samples. From these results, it is possible to implement a practical procedure allow ing the damage quantitative evaluation from ultrasonic velocity and attenua tion measurements. The damage mechanism is identified through a detailed an alysis of the velocity and attenuation dispersion laws.