Ultrasonic signal analysis for defect characterization in composite materials

Abstract

A carbon-fibre composite panel with purposely introduced artificial disbonds using foreign inclusions like Teflon,paper, non-metallic wire mesh, organic liquids, etc during fabrication, was tested with the help of an ultrasonic immersion technique and an ultrasonic dry-couplant technique. In order to characterise the defects, and thus enable evaluation of the plate for fitness-for-purpose, a detailed analysis of the signals obtained during immersion and dry-couplant techniques was also attempted using a signal analyser. Signal analysis techniques like auto-power spectrum analysis and demodulated auto-correlogram pattern analysis* were adopted. The characteristic patterns obtained by a demodulated auto-correlation function method from good regions and disbond regions are discussed. Signal analysis approaches have been found to be successful in detecting and characterising foreign inclusions and disbonds.