Progressive damage and failure strength of notched woven fabric composites under axial loading with varying strain rates

This study investigated the failure of notched and un-notched plain weave composite specimens subjected to varying strain rate loading. Different strain rate axial loads were applied to observe the rate effect on the failure. Both uniform and non-uniform strain rate loads were applied to the notched and un-notched composite specimens, respectively. Notched specimens showed initial cracks at the edge of the hole before final fracture. The initial crack under tensile loading became smaller as the strain rate increased. The initial crack length was predicted using the finite element analysis of the non-homogeneous, micromechanics-based model. The predicted length agreed well with the experimental measurement. Application of the initial crack size for the characteristic distance of the Average Stress failure criterion yielded acceptable tensile notch strengths. The compressive notch strength was less sensitive to the tensile notch strength. The non-constant, varying strain rate loading showed that the failure strength and stiffness depend on the history of the applied loading rates. The effects of the varying strain rates on both notched and un-notched specimens were different qualitatively. However, the strength ratios of the notched to un-notched specimens under varying rates were greater than those under constant rates regardless of tensile or compressive loading.