Development of Crack Detection System Using DIC Method and Evaluation of Fatigue Crack Growth in CFRP Laminates

Abstract

A digital image correlation (DIC)-based crack detection system was developed for composite materials. To avoid incorrect displacement determination, subsets for DIC analysis around cracks were rearranged from their original positions according to their correlation coefficients. The system validity was evaluated through in situ cyclic loading test observations, in which fatigue crack growth in carbon fiber reinforced polymer (CFRP) was captured using a trigger system synchronized with cyclic loading. DIC analysis was carried out in the 90° ply of a cross-ply CFRP laminate. The cross-sections of carbon fibers were utilized as a random speckle pattern for the analysis. The results showed that the correlation coefficients remained higher over the inspected area with subset rearrangements but became lower without rearrangements around transverse cracks. The proposed method successfully evaluated the locations of cracks and crack opening displacements. Consequently, the propagation behavior of the transverse cracks was clearly captured under cyclic loading.