ELASTIC STRESS-STRAIN PROPERTIES OF FIBER REINFORCED COMPOSITE MATERIALS

摘要

Approximate equations for determining the elastic constants of a unidirectional fiber reinforced composite material from constituent material properties are derived. In particular, equations are developed for longitudinal modulus, transverse modulus,- and Poisson's ratio, while an equation already available in the literature is suggested for shear modulus.. Classical theory of elasticity is applied to simplified models of a composite unit cell resulting in closed form solutions. Airy stress functions are applied to the fiber and matrix with boundary conditions requiring continuity of displacements across the fiber-matrix interface (perfect bonding is assumed) and continuity of the appropriate stresses. Graphical results are shown for glass-epoxy composites and for boron-epoxy composites. For a composite with a high volume percent of reinforcement these graphs clearly indicate that even though resin properties are the predominant factor in transverse modulus, and shear modulus they can be improved by high modulus fibers such as boron. Experimental results were obtained for longitudinal modulus, transverse modulus, shear modulus and Poisson's ratio of a boron fiber reinforced composite. A general discussion of stress-strain relationships as applied to fiber reinforced composites is also presented. Considerable detail is given concerning the fabrication of the experimental samples.