Creep and damage accumulation in orthotropic composites under cyclic loading

Experimental results and theoretical prediction of the response of glassfib er-reinforced polyester under quasi-static, static (creep), and cyclic (fat igue) loading are presented. The nonlinear strain component at static loadi ng and the strain amplitude rate at cyclic off-axis loading of an orthotrop ic composite are shown to follow the associated flow rule with a single-par ameter quadratic potential function. The influence of fatigue damage on def ormation is considerable due to the reduction in the elastic modulus of the composite and is apparently negligible with respect to its effect on the p arameters of the creep kernel.