2003 Volume 52 Issue 3 Pages 281-287
Experiments on inelastic deformation of epoxy were performed under fundamental loading conditions systematically from the viewpoint of the formulation of an inelastic constitutive equation. In experiments under monotonic loading conditions, stress-strain relations depending on the loading rate and loading direction defined in stress space were elucidated. Moreover, creep curves and transient behaviors in tension with change in stress rate were obtained. In the case of loading conditions including unloading, on the other hand, strain recovery during unloading depending on the loading history was elucidated since the strain recovery is significant in epoxy. Then, the inelastic constitutive equation that has been developed for CFRP (epoxy reinforced by carbon fibers) so far was applied to the experimental results. In order to take into account the effect of hydrostatic pressure on the inelastic deformation of epoxy, the first invariant of stress tensor was introduced into the constitutive equation. The experimental results were simulated by the modified constitutive equation, and the describability of the inelastic deformation of epoxy by the modified constitutive equation was discussed.