AN EXPERIMENTAL-STUDY OF RESIDUAL FIBER STRAINS IN TI-15-3 CONTINUOUS FIBER COMPOSITES

A simplified experimental technique to determine the axial fiber residual strain in continuously-reinforced metal matrix composites is described. The residual fiber strains in two Ti-15V-3Cr-3Al-3Sn/SiC metal matrix composites have been measured with this technique. Residual fiber strains on the order of 0.2% are measured in the as-processed condition, and the residual stresses approach zero after testing the composite in tension to failure at room temperature. A conceptual description of the effect of tensile testing on the residual stresses is provided. The experimental results are consistent with predictions based on a concentric cylinder iso-strain analysis of thermal strains. Measurement errors result in a residual fiber strain error that is typically less than +/-0.05%. Periodic fiber bending induced by cross-weave fibers is also analyzed, and may contribute significantly to measurement errors.