A normalization procedure and determination of axisymmetric defect characters of composite panels

In Pulse Thermographic Nondestructive Evaluation (TNDE), the thermographic signals are heavily influenced by material directionalities, therefore comparison of thermographic results are challenging. In this study a normalization procedure is introduced which simplifies the analysis and requires only break time, equilibrium temperature, and diffusivity ratios of transverse to lateral diffusivity. The normalization for the composite panels was proved to be effective for quasi-isotropic carbon epoxy composite panels used in the study. A correlation method was utilized to estimate the defect diameter and depth of a composite panel. The correlation method utilizes several numerical models to estimate the correct defect parameter of the experimental specimen. Thermographic Signal Reconstruction (TSR) second derivatives found to be effective in differentiating the defect parameters.