Research on Characterization of Damage States in Continuous Fiber Composites Using Ultrasonic Nondestructive Evaluation

摘要

It is well know that composite materials suffer complex damage when they are subjected to either monotonic or fatigue loading. This damage affects both the velocity and attenuation of ultrasonic waves. The primary objective of this research is to correlate the damage states with the changes in the velocity and attenuation. Once this has been accomplished the pair of ultrasonic parameters becomes a measure of the damage. A particular damage mode, namely, transverse cracking has been examined in detail. The Through-the-thickness attenuation was found to be a very sensitive measure of transverse cracking. In order to study the influence of damage axial stiffness, we have studied the propagation of Leaky-Lamb waves. As expected the transverse cracking significantly reduces the axial stiffness. Finally, a new experimental technique for measuring speed and attenuation of ultrasonic waves in laminates of very small thickness has been developed. Key Words: Ultrasonic nondestructive testing, Lamb waves.