Moisture and Thermal Expansion Properties of Unidirectional Composite Materials and the Epoxy Matrix

Abstract

Experimental techniques are presented for determining the moisture- and thermal- expansion coefficients of polymers and polymer-matrix composite materials. Materials tested included Hercules 3501-6 neat epoxy resin, Hercules AS/3501-6 graphite/epoxy unidirectional composite, and Owens-Corning S2 glass fibers in the same Hercules 3501-6 epoxy matrix. Correlations of the experimentally determined moisture- and thermal-expansion properties with a nonlinear, finite element, micromechanics analysis are presented. Thermal expansion results for all three materials, both dry and moisture-conditioned, were obtained. Moisture diffusivity constants were also ex perimentally determined. It is demonstrated that the moisture and thermal expansion of composite materials can be determined experimentally and predicted numerically, with generally good results.