High strain rate behaviour of 5-harness-satin weave fabric carbon–epoxy composite under compression and combined compression–shear loading

The strain rate dependent mechanical behaviour was studied for the common out-of-autoclave aerospace textile composite 5-harness-satin carbon–epoxy. End-loaded 15°,30°15°,30° and 45°45° off-axis and 90°90° compression tests were carried out at three different strain rate levels (4×10-4s-1,200s-1 and 1000s-1) to determine the effect of strain rate for transverse compression and combined transverse compression/in-plane shear loading. The dynamic tests were carried out on a split-Hopkinson pressure bar, where high speed photography and digital image correlation allowed a detailed study of the specimen deformation and failure process. Quasi-static reference tests were carried out on an electro-mechanical test machine using the same specimen type and a static DIC system. Pronounced strain rate effects on the axial stress–strain response were observed for all specimen types. Failure envelopes for the combined σ22c-τ12 stress state were derived from the experimental data and compared with the maximum stress criterion, which appears well suited to approximate the experimental failure envelope at all strain rate levels. It was observed that the failure envelope was simply scaled up with increasing strain rate, while the overall shape was found to be strain rate independent.