On the large deformation and localization behavior of an epoxy resin under multiaxial stress states

The paper describes a series of experiments that were conducted in order to examine the response of a cross linked epoxy resin. A variety of stress states were considered by conducting experiments under uniaxial tension, plane strain compression, simple shear and combinations of tension or compression and shear (biaxial). Strain rate effects were considered in the simple shear experiments and displacement measurements using geometric moire were made in order to follow the onset and propagation of shear bands under simple shear and compression on shear. Some birefringence measurements were also made. Localization in the form of shear bands occurred under the tensile, simple shear and the biaxial stress states but not under plane strain compression. The shear bands in simple shear and compression and shear grew quickly along the specimen gage length and then broadened, and detailed strain distributions were determined as a function of load level. The birefringence became constant in regions where shear banding had occurred. The onset of shear banding was delayed by higher strain rates and compressive stresses but was promoted by tensile stresses. The lack of a limit load in the plane strain compression response indicates that the epoxy considered here does not strain soften and that the response obtained is the true material one.