The accumulated dissipated energy of composites under cyclic-dynamic stress

This paper presents a method for the estimation of the vibratory fatigue strength of composite materials, which is based on the accumulated dissipated energy. The accumulated dissipated energy was measured with a special measuring technique that is able to catch quasi-continuously the mechanical properties of the tested samples. The samples were made of glass-fiber epoxy foams reinforced with pretreated woven fabrics. The curves of the accumulated dissipated energy were approximated by an equation that includes several parameters. These parameters were identified for experiments with different types of load and for samples with different contents of micropores. In the equation for samples that reach more than 10(6) load cycles, the accumulated dissipated energy in one load stage tests turns out to be a linear function. With this function the fatigue limit of the samples can be predicted.