Thermal image analysis for the in-situ NDE of composites

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