STP772: Fracture Characterization of a Random Fiber Composite Material

    Alexander, RM
    Texas A&M University, College Station, Tex.

    Schapery, RA
    Texas A&M University, College Station, Tex.

    Jerina, KL
    Texas A&M University, College Station, Tex.

    Sanders, BA
    General Motors Technical Center, Warren, Mich.

    Pages: 17    Published: Jan 1982


    Abstract

    A short-glass fiber composite materials, SMC-R50, was tested under uniaxial loading at ambient temperature and humidity conditions over two orders of magnitude of loading rate. The test method, experimental results, and analytical characterization of fracture behavior are described. Baseline information on the strength of 1.27-cm and 2.54-cm wide unnotched tension specimens indicate that effects of size and test orientation (relative to molding orientation) are not significant. Fracture behavior of notched samples was studied on specimens of two different widths (2.54 and 5.08 cm); each sample had two symmetrically cut, crack-like notches. For each sample size, the effect of four different notch lengths and loading rates on ultimate strength, ultimate strain, and the overall stress-strain curve were investigated. Loading rate was found to have no significant effect on sample response. The stress-strain curves of notched and unnotched samples in terms of nominal stress σ and strain ϵ obey the power law σ ∼ ϵ0.78 out to failure. In spite of this nonlinearity, it was possible to characterize the fracture stress behavior using linear elastic fracture mechanics theory and a constant fracture toughness. The effect of notch length on sample compliance and on failure strain was found to obey this theory if ϵ0.78 is used in place of ϵ.

    Keywords:

    composite material, glass fibers, fracture (materials), failure, fracture tests, toughness, tension tests


    Paper ID: STP29387S

    Committee/Subcommittee: E08.07

    DOI: 10.1520/STP29387S


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