Fatigue threshold-stress determination in AFP laminates containing gaps using IR thermography

Based on the thermal observations of surface temperature of gapped specimen under fatigue loading with different maximum stress levels, a relation between the thermal response and the applied stress was observed. From this relation, the threshold stress value can be evaluated using a small number of specimens and in a short time. To investigate the applicability of this technique to different stacking sequences, fatigue tests were conducted on unidirectional, four-angle and cross-ply laminates containing defects (gaps). In addition, stress/life curves were developed for reference and defected specimens in order to get the threshold value using the traditional (Wohler) method. The results of threshold stress using IR thermography are in very good agreement with the results obtained using the traditional way.