Effects of loading rate on crack growth behavior in carbon fiber reinforced polymer composites using digital image correlation technique

The aim of this work is to investigate the effect of the loading rate on the crack growth behavior in carbon fiber reinforced polymer composites, under mode I monotonic tensile loading. For such objective, inter-laminar fracture toughness tests were performed on double cantilever beam (DCB) specimens, according to the ASTM-D5528 standard. The initial crack tip opening displacement (CTOD) was obtained by employing the digital image correlation (DIC) technique. Then, the strain energy release rate and the R-curve were obtained from the force-displacement curve, based on the modified beam theory (MBT), the compliance calibration method (CC) and the modified compliance calibration method (MCC). No significant variation was observed between results of these methods. Obtained results also indicated no considerable changes in the maximum force, by increasing the loading rate. The relation between the initial CTOD and the crack length was nonlinear, due to fiber bridging during testing. In addition, increasing the loading rate caused extended steady state fiber bridging zones.