Nonlinear creep-recovery response of a polymer matrix and its composites

The nonlinear-viscoelastic response of neat epoxy resin and unidirectional graphite/epoxy and glass/epoxy composites was characterized. Numerical techniques were developed for the efficient evaluation of the viscoelastic parameters in the Schapery integral representation that was used. A microcomputer-based test facility for automatic creep-recovery testing was developed. The time-dependent response of the composites correlated well with predictions obtained using a finite-element micromechanics program with the neat-epoxy-resin viscoelastic data as input.