Thermal Image Analysis for the In-Situ NDE of Composites

Thermal image analysis is an emerging nondestructive evaluation (NDE) technique that shows promise as a potential on-line monitoring and inspection method for composites. The method is rapid, user-friendly, and can determine two-dimensional material property distributions as well as quantitatively characterize delaminations. In this paper, the theoretical background of the method and fundamental apparatus are described. Results of the analysis applied to defect-free and delaminated carbon-carbon composite plates are discussed. Two-dimensional distributions of thermal diffusivity were obtained and verified with values obtained by the ASTM standard laser flash diffusivity method. Global specific heat and thermal conductivities were also found and compared to baseline values. In all cases the thermal image analysis results were found to provide reasonable engineering accuracy. Additionally, delaminated plates were tested in order to quantitatively characterize defect location and size. The thermal image analysis results for the delaminated plates were comparable, if not more precise, than observations using ultrasonic C-scan.