STP1290

    Interfacial Measurements and Fracture Characteristics of Single and Multi-Fiber Composites by Remote Laser Raman Microscopy

    Published: Jan 1996


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    Abstract

    The micromechanics of stress transfer in single-fiber as well as multi-fiber composites were investigated. The material system under investigation consisted of high modulus carbon fibers embedded in an epoxy resin. The point-by-point stress in the fiber was measured using the newly developed technique of remote laser Raman microscopy (ReRaM). The composite specimens were loaded incrementally in tension and the stress transfer profiles emanating from fiber discontinuities, such as fiber breaks, were closely monitored. At each applied stress level, the interfacial shear stress (ISS) distribution was derived by means of a balance of shear-to-axial forces argument. In the single-carbon fiber/epoxy system, a maximum interfacial shear stress of 30 MPa was reached at the point of first fiber fracture. In the multi-fiber carbon fiber/epoxy system, the maximum interfacial shear stress developed at the point of first fiber fracture was of approximately the same magnitude. Finally, the local stress concentration in the intact fibers, as a result of an adjacent fiber fracture, was determined as a function of distance from the fiber fracture for three distinct levels of applied stress. A maximum stress concentration of approximately 1.2 was measured at the maximum applied composite strain level of 0.5%. This value compared well with existing analytical models.

    Keywords:

    stress-transfer, interfacial shear stress, carbon fiber, epoxy resin, laser Raman, spectroscopy, stress concentration


    Author Information:

    Galiotis, C
    Reader, research student, and research fellows, Queen Mary & Westfield College, University of London,

    Chohan, V
    Reader, research student, and research fellows, Queen Mary & Westfield College, University of London,

    Paipetis, A
    Reader, research student, and research fellows, Queen Mary & Westfield College, University of London,

    Vlattas, C
    Reader, research student, and research fellows, Queen Mary & Westfield College, University of London,


    Paper ID: STP38223S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP38223S


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