PREDICTION OF THE PORE-CLOSING KINETICS DURING THE CONSOLIDATION STAGE OF SIC UNIDIRECTIONAL LONG FIBERS - TITANIUM-ALLOY MATRIX COMPOSITES

Titanium-aluminium alloy matrix composites reinforced by long SiC fibe rs are considered as potential replacements for the conventional alloy s used in aerospace applications for higher temperature service. A dir ect elaboration route of such composites is the hot uniaxial pressing of an assembly of metal foils stacked between uniaxial fiber mars. The kinetics of pore closing are studied through a finite-element simulat ion, the pressure boundary conditions, rigid-fiber rheology, sticking friction between the matrix and the fibers and a two-domain rheologica l constitutive equation (modelled by two Norton-Hoff laws) correspondi ng to both superplastic and high strain-rate behaviour ranges for the Ti-6Al-4V alloy, being considered. The influence of the distance betwe en the fibers for two types of arrangement (rectangular and triangular ) is studied. The effects on the kinetics of pore closing of both cons olidation pressure and rheological laws are discussed also.