Elasto-Plastic Analysis of the Iosipescu Shear Test

It has been shown in this research that the effect of non-linear material behavior has a large effect on the mechanical response of 00 unidirectional graphite/epoxy Iosipescu shear test specimens. The Iosipescu specimens with and without axial splits at the roots of the notches have been numerically investigated. Using a non-linear finite element analysis and an anisotropic plasticity model, numerical load-displacement and shear stress-strain diagrams that closely match the experimentally obtained curves have been obtained. In addition, stress distributions have been numerically determined for the Iosipescu specimens assuming the presence of three different non-linearities, namely material non-linearity, geometric non-linearity, and boundary contact non-linearity (specimen sliding within the fixture). It has been found that the material non-linearity is primarily responsible for the non-linear behavior of the specimens subjected to shear. Both the geometric and boundary contact non-linearities have an essentially insignificant effect on the load-displacement diagrams and internal stresses in the specimens subjected to small shear deformations. The non-linear material behavior significantly reduced the internal stress concentrations at the roots of the notches. For the proper evaluation of the shear strength of unidirectional graphite/polymer composite materials using the Iosipescu shear test, the non-linear material behavior must be considered in a finite element analysis. However, it has also been shown in this research that the shear strength of unidirectional graphite/epoxy composites can be quite accurately determined from the experimental load-displacement data.