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A full-field thermoelastic stress analysis infrared (TSA-IR) method is used to investigate the possibility of inspecting for out of plane fiber waviness in composite structures. Two different waviness profiles are generated and compared to control specimen having no anomalies. Tension and compression loading schemes are investigated and the TSA-IR emissions are compared to cross-sectional investigations. A subset of the specimens is also notched to investigate the thermal emissions from holes when compared to the waviness. The interaction of the hole and waviness shows the errors that can be introduced when using TSA-IR for quantitative analysis.

A B S T R A C T Quantitative damage detection in composite single lap joints during fatigue is difficultand not practical with many traditional experimental methods. The objective of this study is to combine a new experimental analysis method with existing stochastic models that is capable of taking the scatter inherent in composite fatigue data into account for better representation of damage evolution in single-lap joints. This study presents a new quantitative approach where thermoelastic stress analysis (TSA), a remote sensing and non-destructive evaluation technique, is used for in situ continuous monitoring for fatigue damage detection of Fibre Reinfoced Polymeric (FRP) S2-glass/E733FR singlelap joints. Image analysis algorithms are developed to capture the debonding fronts, and Markov Chain models (MCMs) are developed to capture the fatigue damage evolution in composite lap-joints based on the experimental analysis. The TSA damage index at the last fatigue cycle is used to calibrate the MCMs, and damage predictions using the MCMs are then examined at different fatigue cycles. Methods to construct a predictive stochastic S-N curve utilizing the MCMs are discussed. The proposed IR-TSA with MCMs is shown to be very effective in predicting the damage evolution and allowed constructing S-N curves that take the variability into account for damage in composite single-lap joints.