Environment assisted cyclic fatigue crack growth testing of polymer/inorganic laminates under strain energy release rate control

We focus on the development and implementation of an environmental (hot-dry or hot-humid air) testing methodology for adhesively bonded laminates under maximum strain energy release rate (SERR) control. The technique overcomes disadvantages displacement- force-controlled fatigue crack growth testing. Fracture mechanics based double cantilever beam (DCB) specimens comprising steel/epoxy- glass/polyolefin-laminates were investigated using electrodynamic test system with automated software Crack length was evaluated in-situ a compliance calibration approach. User-defined SERR values set control channel. changed every 200,000 cycles after exceeding milestones. For steel/epoxy-laminates adhesive thickness approximately 5 µm good agreement rates obtained by displacement Moreover, negative effect humidity (50% vs. 10% rh) delamination resistance confirmed at 60 °C. In contrast, significant deviations deduced 250 hot-dry (60 °C, 1% conditions. attributed to differences in damage zone size soft polymeric adhesive. Under 80% conditions reasonable controlled data observed less pronounced failure interfacial manner.