Quantitative non-destructive evaluation method for impact damage using eddy current pulsed thermography

Carbon fibre reinforced plastic (CFRP) has been widely used in industry. In order to detect and evaluate impact damage defects within this material, a non-destructive testing and evaluation (NDT&E) method of eddy current pulsed thermography (ECPT) is proposed. The idea of divergence characterisation of the expansion (or contraction) rate of the object and fluid volume can be extended to the thermal pattern characterisation of ECPT. This paper enables the extraction of this value of divergence at an appropriate time period to yield several desirable properties unique to NDT&E problems. The relationship between divergence and transient thermal patterns, as well as divergence and impact energy, are provided and analysed. The positive and negative values of the divergence and their relationship between composite structures and material state are investigated. Quantitative non-destructive evaluation (QNDE) of impact damage with ECPT from divergence patterns and image areas is derived. The results of this proposed method illustrate that defect areas are highly affected by impact energies. This proposed work can be applied for impact damage detection and quantitative evaluation in CFRP, which can be further used in life-cycle assessment and condition based maintenance.