STP631: Fracture Toughness of Random Glass Fiber Epoxy Composites: An Experimental Investigation

    Gaggar, S
    Research Associate and professor of materials engineering, Illinois Institute of Technology, Chicago, Ill.

    Broutman, LJ
    Research Associate and professor of materials engineering, Illinois Institute of Technology, Chicago, Ill.

    Pages: 21    Published: Jan 1977


    Abstract

    An experimental investigation to determine the applicability of linearelastic fracture mechanics to a randomly oriented, discontinuous fiber epoxy composite is described. Two epoxy resins differing in ductility were reinforced by a glass fiber mat such that the volume fraction of glass could be varied from 20 to 45 percent. The candidate stress-intensity factor (KQ) was measured using single-edge notched (SEN), double-edge notched (DEN), and notched bend tests (NBT). The effect of specimen thickness, notch-root radius, and a/w ratio was investigated. It is suggested that a conservative value of stress-intensity factor representative of the onset of fiber-matrix debonding (KD) be utilized for design purposes. It is shown that good correlation for KQ exists between the various types of specimens and that KQ is independent of specimen thickness. KQ is also independent of the a/w ratio for DEN and NBT specimens. It is also shown by calculation that the magnitude of the fracture energy is dominated by the fiber-matrix debonding energy and the fiber pull-out energy.

    Keywords:

    crack propagation, fractures (materials), glass fibers


    Paper ID: STP35547S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP35547S


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