FIBER DAMAGE DURING THE CONSOLIDATION OF PVD TI-6AL-4V COATED NEXTEL 610(TM) ALUMINA FIBERS

Titanium matrix composites reinforced with sol-gel synthesized alpha-a lumina fiber tows have attracted interest as a potentially low cost co ntinuous fiber reinforced metal matrix composite system. We have condu cted a detailed investigation of fiber damage during high temperature consolidation of PVD Ti-6Al-4V metallized sol-gel alumina fiber tows. Using both hot isostatic pressing and interrupted vacuum hot press con solidation cycles, the two principal mechanisms of fiber damage have b een experimentally identified to be microbending/fracture and fiber ma trix reaction. A time dependent micromechanics model incorporating the evolving geometry and mechanical properties of both the fibers and ma trix has been formulated to simulate the fiber bending/failure mechani sm in a representative unit cell and explore the effect of fiber stren gth loss due to reaction with the matrix. This model has been used to design a process cycle that minimizes damage by exploiting the enhance d superplastic deformation of the initially nanocrystalline PVD Ti-6Al -4V matrix.