A METHOD FOR MEASURING RESIDUAL STRAINS IN FIBER-REINFORCED TITANIUM MATRIX COMPOSITES

A new method for measuring the residual fiber strains in fiber-reinfor ced titanium matrix composites has been developed. The method involves selectively etching the matrix over a prescribed length of composite and subsequently measuring the extension of the relaxed fibers relativ e to neighboring fibers that are still embedded within the matrix mate rial. The extensions are measured using confocal microscopy. The metho d is demonstrated on three unidirectionally reinforced composites with varying fiber volume fractions. The effects of specimen tilt and fibe r splaying following dissolution on the measured fiber extensions are analyzed. The residual fiber strains are rationalized on the basis of the thermoelastic properties of the constituents through a concentric cylinder model. The current method can be applied to other metal matri x composites reinforced with large diameter (monofilament) fibers, pro vided the matrix can be selectively etched. Copyright (C) 1996 Acta Me tallurgica Inc.