STP602

    Effects of Thermal Cycling Environment on Graphite/Epoxy Composites

    Published: Jan 1976


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    Abstract

    Graphite/epoxy (Gr/E) composites have attractive properties—low density, high stiffness, and a low coefficient of thermal expansion (CTE)—that make them prime candidates for many spacecraft applications. The effects of a thermal cycling environment on the dimensional stability and microstructural integrity of Gr/E composites were evaluated. Severe microcracking was found in several high-modulus fiber (HMS)-reinforced 350°F-cure epoxy resin systems after exposure to 25 thermal cycles between the temperature of liquid nitrogen (−320°F) and that of boiling water (+212°F). A hybrid system combining Thornel-300 (T-300) fabric and HMS tape exhibited fewer microcracks, with the fabric acting as a crack stopper. Of the material systems investigated, a 250°F-cure system, HMS/CE 339, was found to be the most resistant to microcracking. The effects of thermal cycling on the microyield strength (MYS) and CTE of several near-zero expansion Gr/E composites were also studied.

    Keywords:

    composite materials, graphite composites, epoxy composites, thermal cycling tests, microyield strength, coefficient of thermal expansion, cracking


    Author Information:

    Camahort, JL
    Materials and processes specialist, Space Systems Division, and research specialist, Manufacturing Research, Lockheed Missiles and Space Company, Incorporated, Sunnyvale, Calif.

    Rennhack, EH
    Materials and processes specialist, Space Systems Division, and research specialist, Manufacturing Research, Lockheed Missiles and Space Company, Incorporated, Sunnyvale, Calif.

    Coons, WC
    Staff scientist, Lockheed Palo Alto Research Laboratory, Palo Alto, Calif.


    Paper ID: STP27779S

    Committee/Subcommittee: D30.08

    DOI: 10.1520/STP27779S


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