CONTINUUM PREDICTIONS OF DEFORMATION IN COMPOSITES WITH 2 CREEPING PHASES .1. MODEL SYSTEMS

Analytical and finite element (FE) method continuum analyses of deform ation are described for model composites in which both phases exhibit either transient or steady-state creep. Both models predict that the p resence of a weak ductile phase within a strong matrix, e.g. ductile-p hase toughened intermetallic matrix composites, degrades the creep res istance of the strong phase less severely with decreases in: (1) the s tress exponent of the matrix; (2) the volume fraction of the discontin uous ductile phase; and (3) the creep rate of the ductile phase. The F E models predict potential locations for creep damage within the compo site, and that the steady-state creep rate of strong-matrix composites is nearly independent of the reinforcement geometry. Finally, both mo dels predict that the composite steady-state stress exponent generally nearly equals that of the slower creeping phase due to the redistribu tion of stress from the faster to the slower creeping phase.