Comparative evaluation of delamination in carbon fiber reinforced composites (CFRPs) utilizing various common non-destructive inspection techniques

Abstract

Non-destructive Inspection (NDI) is routinely used to diagnose and monitor defects in composite parts, which could impact composite lifespan and performance. There are a variety of methods to conduct NDT in composites, the most popular being ultrasonic c-scan, shearography (thermal and vacuum excitation), and pulsed thermography testing. This study evaluates these NDT methods by testing on a set of CFRP laminates fabricated through a vacuum infusion process with artificially programmed defects. Firstly, these methods are evaluated based upon their detection capability- i.e., can each find the programmed defect in a standard inspection procedure. Secondly, how well do the scans predict the defect area? This is done utilizing a computed tomography scanning (CT-Scan) of the same laminates to create a benchmark to reference for the other three NDT methods. Finally, these methods are compared and contrasted. This study finds that ultrasonic c-scans and pulsed thermography share near-identical detection capabilities in the range of depths analyzed. Shearography, utilizing thermal excitation, could not detect any of the programmed delaminations, while partial vacuum shearography was only able to detect a limited selection of the largest sized defects. Under CT scans, the programmed defects were found to have inconsistencies, error correction was performed and relationships for ultrasonic scanning and thermography were able to be ascertained. Ultrasonic scans show consistent levels of error past near surface defects and thermography sees increased error in area detection as defect depth increases.