A FIBER FRACTURE MODEL FOR METAL-MATRIX COMPOSITE MONOTAPE CONSOLIDATION

The consolidation of plasma sprayed monotapes is emerging as a promisi ng route for producing metal and intermetallic matrix composites reinf orced with continuous ceramic fibers. Significant fiber fracture has b een reported to accompany the consolidation of some fiber/matrix syste ms, particularly those with creep resistant matrices. Groves et al. [A cta metall. mater. 42, 2089 (1994)] determined the predominant mechani sm to be bending at monotape surface asperities and showed a strong de pendence of damage upon process conditions. Here, a previous model for the densification of monotapes [Elzey and Wadley, Acta metall. mater. 41, 2297 (1993)] has been used with a stochastic model of the fiber f ailure process to predict the evolution of fiber fracture during eithe r hot isostatic or vacuum hot pressing. Using surface profilometer mea sured roughness data for the monotapes and handbook values for the mec hanical properties of different matrices and fibers, this new model is used to elucidate the damage dependence on process conditions, monota pe surface roughness, and the mechanical properties both of the fiber and matrix. The model is used to investigate the ''processibility'' of several currently important matrix and fiber systems and to identify the factors governing this. An example is also given of its use for th e simulation of a representative consolidation process cycle. This app roach to the analysis of a complex, nonlinear, time-varying process ha s resulted in a clear understanding of the causal relationships betwee n damage and the many process, material and geometric variables of the problem and identified new strategies for its elimination.