MICROMECHANICAL ANALYSIS OF HYBRID COMPOSITES (REPRINTED FROM ENERCOMP-95, PROCEEDINGS OF THE INTERNATIONAL-CONFERENCE ON COMPOSITE-MATERIALS AND ENERGY, MAY 8-10, 1995)

The response of hybrid composites to tensile and transverse loads is s tudied using a micromechanical analysis, Of particular interest are th e effects of matrix viscoelasticity and the properties of the interpha se region on the material properties and failure initiation. The tensi le response of hybrid composites is studied using a statistical model in which the fiber failure strains are represented with Weibull distri butions. A shear lag formulation is used to include the contribution o f load transfer to broken fibers to the longitudinal modulus. The tran sverse tensile response is studied using the rule-of-mixtures. Linear viscoelastic matrix properties are incorporated in both analyses. Resu lts from the analysis indicate that the interphase properties have a n egligible effect on the longitudinal failure strain and that the effec t of matrix viscoelasticity on the longitudinal tensile response is ne gligible. The longitudinal failure strains decreased with increasing c omposite length and carbon to glass volume ratios. For transverse tens ile loading, the stress rises more rapidly on the stress strain curve when the strain rate is increased and when the interphase moduli are h igher.