STP775

    Characterizing Delamination Growth in Graphite-Epoxy

    Published: Jan 1982


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    Abstract

    As part of an overall effort to develop durability and damage tolerance methodology for graphite-epoxy composites, coupon specimens have been developed to measure the fundamental static fracture and subcritical growth behavior of delaminations. Two basic designs, one for the tensile opening mode (Mode I) and one for the forward shear mode (Mode II), are described. These specimens were used to characterize the behavior of two types of interfaces (0/0 and 0/90) for static fracture, constant amplitude fatigue, and spectrum fatigue. Fracture mechanics technology was applied through the principles of strain-energy release rate. Three-dimensional finite-element analyses were employed to interpret the experimental results. A simple growth law was shown to correlate the constant-amplitude and spectrum-growth data. It was found that the applied cyclic load must be nearly equal to the critical static load to obtain observable growth in the tensile opening mode. On the other hand, the graphite-epoxy delamination growth rate in the forward shear mode is comparable to the aluminum growth rate in tension, which suggests that shear is the chief subcritical growth mode for graphite-epoxy.

    Keywords:

    composite materials, composite structures, crack propagation, defects (materials), epoxy resin, fatigue (mechanics), fiber-reinforced composites, fracture (mechanics), graphite, laminates, life expectancy, mechanical properties, reliability assurance, spectra, test methods, tolerance, toughness


    Author Information:

    Wilkins, DJ
    Engineering specialist senior, engineering specialist, senior engineer, senior engineer, and engineer, General Dynamics, Fort Worth Division, Fort Worth, Tex.

    Eisenmann, JR
    Engineering specialist senior, engineering specialist, senior engineer, senior engineer, and engineer, General Dynamics, Fort Worth Division, Fort Worth, Tex.

    Camin, RA
    Engineering specialist senior, engineering specialist, senior engineer, senior engineer, and engineer, General Dynamics, Fort Worth Division, Fort Worth, Tex.

    Margolis, WS
    Engineering specialist senior, engineering specialist, senior engineer, senior engineer, and engineer, General Dynamics, Fort Worth Division, Fort Worth, Tex.

    Benson, RA
    Engineering specialist senior, engineering specialist, senior engineer, senior engineer, and engineer, General Dynamics, Fort Worth Division, Fort Worth, Tex.


    Paper ID: STP34326S

    Committee/Subcommittee: E08.08

    DOI: 10.1520/STP34326S


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