STP569

    Effects of Environment on the Fatigue of Graphite-Epoxy Composites

    Published: Jan 1975


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    Abstract

    Torsional and flexural fatigue tests were performed on both uniaxial (0°) and crossplied (±45°) graphite-epoxy materials at temperatures of 24 and 7°C in environments of air and water. The results of the torsion testing showed that the number of cycles required to cause an initial decrease in stiffness as well as the rate of stiffness loss was a function of temperature and environment; the most significant losses were noted for tests at the higher temperature in water. The torsional fatigue specimens were subsequently tested in four-point bending to determine the effect of torsional damage on longitudinal properties. This damage caused changes in the flexural stiffness, failure stress, and failure energy, depending on the stress and environmental histories. The flexural fatigue tests also showed a significant effect of water (at 24°C) on the material behavior. These results are compared with the results of previous investigations and are discussed in terms of proposed damage mechanisms.

    Keywords:

    composite materials, fatigue tests, environmental tests, nonmetallic coatings


    Author Information:

    Sumsion, HT
    Research scientist and chief, Ames Research Center, NASA, Moffett Field, Calif.

    Williams, DP
    Research scientist and chief, Ames Research Center, NASA, Moffett Field, Calif.


    Paper ID: STP33175S

    Committee/Subcommittee: E08.09

    DOI: 10.1520/STP33175S


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