Creep behavior of unidirectional composites

The creep behavior of the continuous fiber reinforced unidirectional composites due to the viscoelasticity of the resin matrix is investigated assuming that the constituent matrix obeys the nonlinear creep law and the fiber is the linear elastic materials. Utilizing a quasi three-dimensional finite element method, the macroscopic creep behavior of the composites with regular fiber packing is obtained, giving the orthotropic creep law for the composites. Then, the creep of the composites with random fiber packing is estimated applying the random model proposed by Kondo and Saito in which the neat matrix cylinders are embedded in the regular array composites. The theoretical predictions for the creep behavior are compared with the experimental results.