Thermal Expansion Measurements of Polymer Matrix Composites and Syntactics

The coefficients of thermal expansion (CTE) of various polymer matrix materials were measured using a thermal mechanical analyzer. The measurements include a set of standard materials used as calibration materials for the instrument. The data for the base polymers, syntactics, and E and S-2 glass- reinforced polyester matrix composites were obtained in the temperature range from -77 deg C to l20 deg C. The results for all of the polymeric materials, especially for the epoxy and epoxy syntactic (above 65 deg C), are nonlinear. The CTE of the syntactics were reduced by a factor of -2 for the base resins. The data taken for the glass-reinforced composites show peaks and/or humps in the thermal expansion. These features are believed to be from the formation of voids within the plies of the composite laminate. The irregular behavior of the thermal expansion was minimized by thermal annealing under load conditions, whereas annealing in free-space does not significantly dampen this behavior. The thermal expansion of the material appears to be directly related to the fiber loading.