a b s t r a c tOne-sided thermal non-destructive testing (TNDT) is of vital importance in aerospace composites to monitor structural degradation, as well as to detect subsurface defects. The objective of this study is to evaluate simultaneously the thermal diffusivity and to characterize the defects within carbon fiber reinforced polymer (CFRP) composites. In this paper, a novel one sided TNDT technique is presented which relies on creating an artificial inflection point by multiplying front-surface temperature evolution by n th power of time, where 0 < n < 0.5, followed by optimization of n. An analytical solution of the diffusivity calculation and defect characterization in the case of CFRP composite plate is discussed. The characterization of low velocity impact damage is also investigated with the help of theoretical and experimental results. Some key research points which need further exploration are also discussed.

In this paper we demonstrate through-the-thickness imaging of barely visible impact damage in a two-dimensional woven, carbon fiber epoxy laminate using pulsed phase thermography (PPT). Specifically we calibrate the defect depth with blind frequency for the particular material system using a specimen with simulated defects in the form of polymer foam inclusions. The calibrated depth versus blind frequency relation is then applied to specimens with barely visible impact damage due to low-velocity impacts. The polymer foam reproduces the irregular boundaries and thin nature of the delaminations, but does not reproduce through-the-thickness variations. The extent of delamination at different depths was reconstructed as a function of depth for varying levels of impact energy. The extent of damage imaged using PPT corresponded well with visual observations and microscopy images.

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