Experimental Study on Model Fracture Toughness of Unidirectional Composite Laminates Using Digital Image Correlation (DIC) Technique

The mode I interlaminar fracture toughness, G IC , of unidirectional fiber-reinforced polymer matrix composite laminates was determined using the double cantilever beam (DCB) specimens. To ensure real-time correspondence with the growing crack length, load and displacement, the Digital Image Correlation (DIC) technology, a non-contact optical measurement technique, was selected for the fracture toughness tests in this paper. In addition, fracture toughness calculation programs were used to accelerate data processing.The results indicated that the DIC technology was reliable compared with the traditional technology (magnifying glass). The G I C values obtained from all the three calculation methods (CC, MBT and MCC method) differed by no more than 3%. The SEM analysis showed that the crack propagation occurred along the fiber-matrix interface, resulting in plastic cracking and microcracks in the matrix. The observed intact fiber bundles indicated the matrix-dominated cracking in crack propagation, with localized fiber fracture at high stress and a small amount of fiber bridging during separation.