An experimental and theoretical study of creep of a graphite/epoxy woven composite

Abstract The creep behavior of woven fiber polymer composites has been investigated through both an experimental study and analytical modeling. In the modeling, the matrix is assumed to be a 4‐parameter model (a Maxwell‐Voigt combination) and the fibers to be elastic. The fiber undulation model developed by Ishikawa and Chou for elastic behavior of woven fiber composites has been extended to the viscoelastic system by the correspondence principle. This considers the longitudinal and transverse fibers separately. The weave geometry and dimensions are accounted for, thus bringing the model closer to the actual composite. While this model has been used previously to predict the composites elastic behavior, this is the first time it is considered as a viscoelastic solid, which helps determine its time dependent behavior. The resultant model takes into account the different parameters associated with the weave (the density of the fibers in the weave, the radius of the fibers and the profile of the fill and warp fibers), volume concentration of the fiber and matrix in the composite, and the elastic moduli of the fill and warp fibers and the viscoelastic properties of the polymer matrix. We have conducted creep tests on graphite fiber/epoxy composites to evaluate our model. Experiments have been conducted from room temperature (22°C) to 200°F (93°C). The results from experiments have been analyzed and an inverse simulation has been performed to obtain the unknown parameters of the matrix and fibers in the composite. The model is then used to predict the creep behavior of the woven fiber composite under other loading conditions and temperature levels, showing satisfactory agreement with the data.