Monitoring multiple damage mechanisms in crack-patched structures using optical infrared thermography

Abstract

The ability to understand the overall long-term damage behaviour of crack patched components is essential to improve methods for the performance prediction. The method of passive infrared thermography comprises great opportunities to support the comprehension of the subsurface damage progress of crack-patched structures. Quasi-static and cyclic coupon tests are performed with patched metallic specimens and monitored with qualitative and comparative passive infrared thermography. Different test set-ups help to differentiate between pure metallic crack growth and adhesive damage on thermal images. Results show that metallic crack growth can be monitored from the patched side, also in combination with local delamination at the patch/metal interface overlaying the crack. Thus, it is possible to evaluate position and size of the different damage types at the same time with a rather simple test set-up. The information on the degradation progress of the crack patched component under loading conditions can help identify the driving damage mechanism of the particular repair configuration. This knowledge can in return be used in the patch design process.