Prediction of Long-term Creep of Composites from Doubly-shifted Polymer Creep Data

Environmental effects on the creep response of composites are of great interest because these materials are very sensitive to temperature and other environmental conditions. Short and long-term creep effects have been studied for composites under various environmental conditions, but most studies rely on experimental testing of particular laminates. Here, a novel micro-mechanical/laminate model is developed to predict the creep response of laminated polymer matrix composites from matrix creep data. Furthermore, a novel two-parameter super-position method is used to predict the long-term response of the polymer matrix as a function of two environmental parameters: moisture and temperature. The procedure used to compute the two shift factors is described. The resulting master curve can be used to predict the long-term properties of the matrix and for any temperature and humidity conditions. Once the matrix behavior is known, the micro-mechanical/laminate model allows for accurate prediction of long-term properties of arbitrary laminates for the same conditions.