An Analytical Model for Estimating the Coefficient of Thermal Expansion of Random Fiber Reinforced Composites

The coefficient of thermal expansion (CTE) of random glass fiber rein forced polyethylene (PE) and polypropylene (PP) composites prepared using the patented aqueous wet laid process has been measured over a temperature range of 150°C (from -40°C to 110°C). It was found that there were two CTE values for both PE and PP/glass fiber filled composites in this range, namely a low temperature value (from —40°C to a transition value) and a high temperature value (from the transition temperature to 110°C). Predictions were calculated from a model based on Halpin-Pagano laminate analogy, the Halpin-Tsai equations, and Schapery's energy method. Excellent estimates were obtained for the CTE values of PE and PP matrix random fiber composites with varying length and volume fraction of short glass fibers. A computer program developed for the analysis of the data significantly reduced the analysis time.