In this paper, the mechanical behavior of short fiber reinforced polymer (SFRP) composites in high vacuum and temperature conditions is investigated. Even though tested at the same temperature 298 K, the SFRP. composite kept in high vacuum condition has higher tensile strength and equivalent Young's modulus than that in the atmospheric condition. In high vacuum condition, the matrix resin is shrank owing to the degas and/or moisture desorption from the matrix and from the interface between the matrix and fibers, and thus yield the residual stresses in the composites. A homogenization theory with multi-scale asymptotic expansion 'and a fiber distribution model is described for evaluation of mechanical property of SFRP composites in environmental conditions.
