INELASTIC CONTACT DEFORMATION OF METAL-COATED FIBERS

Metal matrix composites (MMCs) can be synthesized by aligning metal co ated ceramic fibers in a shaped container and applying pressure at ele vated temperatures. The high stresses created at the contacts between neighboring fibers cause inelastic matrix flow that fills interfiber v oids, reduces interfiber separations and results in composite densific ation. The rate of densification depends on the contact's resistance t o flow. Current contact mechanics models are unable to adequately pred ict this resistance because they do not account for tile effect of the (elastic) fiber. Closed-form solutions for contact stress-displacemen t rate and contact area-strain relationships are used to describe meta l coated fiber blunting as a function of fiber volume fraction, matrix material non-linearity (i.e. creep stress exponent) and fiber packing geometry. The solutions contain two unknown coefficients (c and F) wh ich are evaluated using the finite element method. A simple model for the consolidation of coated SiC fibers is developed in terms of the co efficients, c and F. The model indicates that materials with a low cre ep stress exponent are more difficult to densify as the fiber volume f raction increases whereas, perfectly plastic materials exhibit a relat ively weak dependence on the fiber volume fraction. (C) 1997 Acta Meta llurgica Inc.