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 caused to polymer composites during water immersion. The acoustical parameters such as velocity and attenuation are linked to the viscoelasticity and microstructure of the propagation medium. For ultrasonic propagation, composite 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 different damage mechanisms. In these conditions, the results of ultrasonic tests during hydrolytic aging allowed us to correlate the evolution of acoustical parameters to the damage level and nature. The ultrasonic results have been validated by complementary mechanical tests and microscopic observations carried out on the same samples. From these results, it is possible to implement a practical procedure allowing the damage quantitative evaluation from ultrasonic velocity and attenuation measurements. The damage mechanism is identified through a detailed analysis of the velocity and attenuation dispersion laws.