Life prediction for composite laminates submitted to service loading spectra

Abstract This paper deals with the prediction of the fatigue life of composite laminates subjected to service loading spectra. Assuming that the spectrum loading is a Gaussian stationary and ergodic process, a model that predicts the fatigue life is proposed. This model requires the results of the constant amplitude fatigue test and is based on a combination of the Palmgreen‐Miner damage rule and the peak‐counting method to define and count the cycles. To compare the model predictions to experimental results, random loading was simulated in three different manners: block programming, random sequence block programming and individual cycles method. It is shown that the three simulation methods agree reasonably well with the experimental results; however, the best agreement is obtained with the individual cycle simulation method. All the constant amplitude and random fatigue tests were performed in three point bending on a digitally controlled servohydraulic fatigue machine that permits random simulation. The material used is a quasi‐isotropic graphite epoxy composite [± 45/0/90] _3s .