An experimental investigation of normal and shear stress interaction of an epoxy resin and model predictions

Abstract

The axial-torsional interaction of an epoxy resin was investigated by subjecting thin-walled tubular specimens to combined normal and shear stress components. It is shown that a superimposed normal stress (tensile or compressive) or hydrostatic pressure will influence shear creep behavior. Similarly, a superposed shear stress affects the normal stress response of the resin. The axial-torsional stress interaction is also observed in transient stress responses under different strain paths, and in the creep deformation with non-proportional stress histories. Linear viscoelastic constitutive models are unable to predict the aforementioned behaviors. Two typical nonlinear viscoelastic constitutive models are examined with respect to their capabilities to predict the observed response. It is shown that the predictions of these two models agree only qualitatively but not quantitatively with experimental results.