Longitudinal stress/strain response of Al₂O₃/Ti 6Al 4V continuous fiber composites

To avoid the high-cost of SiC monofilaments, a new approach to making a monofilament using low-cost tow fibers has been developed. This new approach uses either carbon or an oxide to bind an Al₂O₃ tow (3M Nextel 610) together to essentially form an Al₂O₃ monofilament. Traditional processing techniques developed for monofilaments may then be used; avoiding the difficulties of processing titanium matrix composites (TMCs) with tow based fibers [3]. Our objective was to investigate how this new processing approach affected the composite stress/strain response. We found that processing damage to the fibers (fiber/matrix reactions, fiber fracture and residual bending) caused reductions in the observed ultimate tensile strength (UTS, 0.7 to 1.4 GPa) compared to the predicted UTS (1.5 GPa, using Curtin's lower bound model [14]). Better control of the coating thickness around the Al₂O₃ monofilament would avoid fiber/matrix reactions while fiber fracture and residual bending will decrease as the fiber volume fraction in the Al₂O₃ monofilament increases. Thus this new approach to fiber processing has the potential to produce low-cost TMCs with predicted room temperature UTS.