Novel NDT methods for composite materials in aerospace structures

In this article, two novel NDT methods for composite structures are presented. First, the laser ultrasonic method for visualization of impact damage is introduced. A laser ultrasonic scanning system was developed, and the anomalous incident wave (AIW) energy was obtained from the wave-field data to image the artificial and impact damages. Next, a mid-frequency ECT (eddy current testing) system with the working frequency up to 250 kHz developed by the authors' lab for CFRP inspection is presented. The main features of the system include the weak-signal extraction method using the lock-in amplifier and the C-scan imaging techniques. The location and size of different damages were visualized in the scan image. With the developed system, the direction of different fiber plies could also be successfully detected.