A nondestructive evaluation and structural health monitoring framework for X-COR sandwich composites

A combination of nondestructive evaluation (NDE) and structural health monitoring technique has been used to detect and localize in situ damage in X-COR sandwich composites. The NDE techniques, flash thermography and ultrasonic C-Scan, were used, and the inspection results showed promising capabilities as well as their inherent limitations. Subsequently, a guided wave based active interrogation technique was used to enable real-time damage detection and localization capabilities. Macro fiber composite and piezoelectric wafers were used for actuation and sensing, and the interaction of guided waves with the primary damage modes, delaminations and foam core separations, were studied. The results showed that delaminations lead to the guided wave mode conversion phenomenon within the material discontinuity area. A multidimensional signal processing technique, which was developed with a real-time and reference-free perspective, was used to analyze the converted wave modes in the time-space domain for damage localization. The results indicate that the converted wave mode is an effective indicator of in situ damage, especially when the received signal contains wave modes transmitted from multiple source locations.