Elastic Constants of Uniaxially Fiber-Reinforced Composites with Degraded Interphase

Aboudi's micromechanics based unit cell model for the effective elastic properties of two-phase composites has been extended to three-phase composites to include the effect of an interphase coating. Instead of Aboudi's displacement approach, a cell-stress approach associated with complimentary energy has been employed. Effective elastic constants of three-phase composite, with degraded interphase coating, have been calculated for the graphite/epoxy composite system. The effect of the degree of degradation of the coating interphase has been found to be significant for the transverse Young's modulus, shear modulus, and Poisson's ratio. The axial shear modulus and Poisson's ratio are also affected. The axial Young's modulus is, of course, not affected.