Infrared radiation properties of the carbon–carbon composite and their application to nondestructive detection of its defects

Abstract

Infrared radiation properties and surface characteristics of C/C composites and graphites were examined at temperatures in the range of 293–373 K from the viewpoint of the nondestructive detection of defects in these materials. The radiation temperature of specimen surface and its variation were quantitatively evaluated on the basis of true specimen temperature, ambient temperature, emissivity and radiosity coefficient to obtain data applicable to the thermographic detection of defects. It was found that the larger the pore size and roughness of specimen, the larger the variation of data points. Graphite specimens with different artificial flaws 1–10 mm in diameter and 1–8 mm in depth were examined by thermography, and the minimum difference in radiation temperature at a defect to be detected was obtained with regard to the flaw size.