STP497: Reinforced Cutouts in Graphite Composite Structures

    Kocher, LH
    Senior engineers, Bell Aerospace Company Division of Textron Inc., Buffalo, N.Y.

    Cross, SL
    Senior engineers, Bell Aerospace Company Division of Textron Inc., Buffalo, N.Y.

    Pages: 14    Published: Jan 1972


    Abstract

    A 1-in.-diameter, unreinforced hole in a 6-in.-wide, multidirectional, graphite composite laminate test specimen is shown to reduce the gross section strength by a factor of two. This stress and strain concentration effect is more severe than with most metals because of the nonyielding behavior of the composite but is not as severe as with typical brittle materials. Integral composite reinforcements around holes in several tension specimens are shown to carry loads efficiently, that is, they develop 80 to 90 percent of the strength of a specimen without a hole. For the particular metallic and composite reinforcement designs considered, the composite reinforcements are three to six times as light as metallic ones giving approximately the same load carrying capability. Although these reinforcements are not of an optimum configuration, they demonstrate a capability for reinforcing cutouts in composite structures. Strain responses and ultimate loads compare reasonably well with predictions based on discrete element analysis. A technique of lightweight reinforcement for a cutout in a stiffened compression panel is successfully demonstrated by fabrication and structural testing.

    Keywords:

    graphite composites, laminates, composite structures, reinforcement (structures), metals, stiffening, aircraft panels, airframes, mechanical properties, elastic properties, ultimate strength, anisotropy, orthotropism, symmetry, strains, loads (forces), stress concentration, cracking (fracturing)


    Paper ID: STP27759S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP27759S


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