Prediction of the cyclic durability of woven composite laminates

The fatigue data of woven fiberglass laminate specimens cut at different angles to the principal axes are reported. Changes in the cyclic modulus were monitored in all of the tests. It was found that the final critical damage level before failure, defined by reduction in the cyclic modulus, did not depend on the durability (cycles to failure), but did vary in different loading directions, depending on the asymmetry (in ratio of minimum to maximum load) of cyclic loading. The invariance of critical damage level with respect to the durability provides a means of predicting the cyclic life time by monitoring the damage accumulation reflected by cyclic modulus change.