A numerical and experimental investigation of delamination behaviour in the DCB specimen

An extensive numerical and experimental investigation has been carried out on the fracture mechanical properties of DCB specimens. Static and cyclic properties were studied for different interfaces (0°/0°, 45°/45° and 90°/90°) and for several materials, IM7/ 8552, HTA7/6376 and T300/914. Different data-analysis methods have been compared and two beam models have been compared to a FE solution. Basic studies undertaken include modelling and experimental observation of delamination growth in DCB specimens. State of the art FE analyses are described and the energy release rate of the specimens is calculated. Two beam models are compared with the FE results and it is found that the more advanced beam model is more accurate. Experimental results are interpreted in terms of usefulness for applications to real structures. Toughness measurements on DCB specimens show that non-zero interfaces have a plateau value roughly four times higher than the onset value, which is almost the same as for the zero interface. Higher toughness values are probably due to the fact that the initial crack deviates from the original symmetrical crack plane. The experimental data collection methods corrected beam theory and Berry's method give similar results. Numerically predicted curved crack front for zero-interface could be verified experimentally. The delamination growth rate during fatigue increased rapidly with increasing applied energy release rate and the 0°/0° interface had the highest growth rate. The specimen with a 90°/90° interface has the flattest energy release rate distribution and the specimen with a 45°/45° interface the most uneven one. The material systems IM7/8552 and HTA7/6376 have higher critical energy release rates than T300/914.