A GENERALIZED SELF-CONSISTENT MORI-TANAKA SCHEME FOR FIBER-COMPOSITES WITH MULTIPLE INTERPHASES

In this paper, we discuss methods to obtain the transversely-isotropic effective thermomechanical properties of unidirectional composites reinforced with coated cylindrical fibers. The 3-phase variant of the Mori-Tanaka (1973, Acta Metall. 21, 57) method proposed by Benveniste et al. (1989, Mech. Mater 7, 305) for isotropic reinforcements with one interphase is extended to composites with multiply-coated cylindrical reinforcements (where all constituents are transversely isotropic). Further, a generalized self-consistent (GSC) scheme is proposed for obtaining the transverse shear properties, by using a (n + 1)-phase generalization in which the n-phase composite is embedded in the effective transversely-isotropic composite medium (i.e., the (n + 1)th phase) of unknown properties. Instead of using an equivalent S tensor like Luo and Weng (1989, Mech. Mater. 8, 77), an iterative scheme is developed to solve for the transverse shear properties of the effective composite. When applied to a two-phase composite, the predicted transverse shear modulus (G23) from this (n + 1)-phase model coincides with Christensen and Lo's (1979, J. Mech. Phys. Solids 27, 315) GSC scheme result, while all other properties agree with Hashin and Rosen's (1964, J. Mech. Phys. Solids 31, 223) CCA model. Whenever possible, results for multi-phase (n > 2) composites are verified to coincide with results of other researchers such as Benveniste et al. (1989) and Tong and Jasuik (1990, Proc. ASC, 117). The model is then used to simulate composite systems with degraded interphase regions and fiber-matrix interphases with radial variations in properties.