Investigation of thermal fatigue effects on crack propagation and mode I delamination of multilayer laminated composites using digital image correlation

In this research, the influence of thermal cycling on the fracture toughness and maximum load in mode I delamination of polymer matrix composites (PMCs) is investigated experimentally and analytically. To eliminate the effect of the remote ply orientation on the fracture toughness during delamination initiation and propagation, double cantilever beam (DCB) specimens with a stacking sequence of [0]16 using uni-directional glass fibers and epoxy resin were considered. The specimens were thermal-cycled between 15°C and 65°C for 50-150 cycles. One group of uncycled specimens were tested at the commencement of the investigation as a control group. During the DCB test and receiving universal tensile machine results, the specimens were inspected by 2 real-time cameras to record the delamination length and initial crack tip opening displacement (ICTOD). The strain energy release rate (SERR) approach was used for obtaining the critical fracture toughness (GIC) from the experimental data. By employing the digital image correlation (DIC) method, the initial crack tip separation profile was obtained. The measured bridging laws were used with cohesive elements in ABAQUS commercial software to accurately model the delamination propagation in DCB specimens. Investigation of load variations revealed that critical fracture toughness in mode I of delamination is firmly affected by the thermal fatigue process.