Stress dependence of the raman frequencies for carbon fibers and residual stresses in metal matrix composites

Abstract

A technique is described for determining residual stresses in metal matrix composites using Raman spectroscopy. It is based on the measurement of Raman frequency shifts for both carbon fibers under applied uniaxial stress and fibers in the metal matrix composites. The deformation of fibers was achieved using a tensile rig to obtain the calibration curve. A selective area electropolishing method was utilized to locally expose the constrained fibers in the metal matrix composites so that Raman measurement can be performed. It has been demonstrated that Raman microprobe can be used to determine the residual stresses in the Raman-active fiber reinforced MMC's. The ability of this new residual stress measurement method to measure the localized stress in an individual fiber offers us a useful tool to explore the fiber/matrix interface and to understand the behavior of these important material. Extensive experimental measurements are still required to define the sensitivity and applicability of this approach.