Experimental non-contact evaluation of delamination in CFRP composite plates by laser generation/air-coupled detection ultrasonic system

摘要

The objective of this research is to develop non-contact and real time inspection technique based on laser generated ultrasound for evaluating near-surface delamination in Carbon/Epoxy composite fabricated from automated fiber placement system. In this study, A hybrid laser generation/aircoupled detection ultrasonic system for detection and visualization of delamination in composite plates with simulated delamination of the area of 20 mm x 20 mm between the first and the second layer. Optical fiberized Nd: YAG pulse laser (532 nm, 32 mJ) with linear slit array is used to generate ultrasonic guided wave in unidirectional CFRP specimen (24 plies, 2.85 mm thickness). The characteristic of time domain waveform and frequency spectrum of guided wave is discussed. Two-dimensional images are obtained from these characteristics. The convergence of received signal using the pitch-catch and the scattering-reflection technique is discussed.