RELATIONSHIP BETWEEN INTERPHASE COMPOSITION, MATERIAL PROPERTIES, ANDRESIDUAL THERMAL-STRESSES IN COMPOSITE-MATERIALS

A methodology for predicting the formation and influence of interphase regions in composite materials is illustrated through an investigatio n of the relationship of sizing-induced interphase regions to the deve lopment of residual thermal stresses in a carbon fiber epoxy-amine com posite. Fiber surface and sizing induced concentration gradients in th e epoxy-amine system were predicted. Material property data was measur ed for bulk epoxy-amine systems corresponding to the predicted interph ase concentrations and the properties mapped into property profiles in the vicinity of the fiber surface. Micromechanical models were used t o predict residual thermal stresses for carbon fiber epoxy-amine compo sites with these interphase properties. The analyses predict that the thermal stress state is significantly affected by modulus variations i n the interphase region. The variations in the properties of the inter phase material can be affected through processing conditions and/or ma terial selections.