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    Structural Qualification of Composite Propeller Blades Fabricated by the Resin Transfer Molding Process

    Published: Jan 2001

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    The unique challenges for developing design allowables for a resin transfer molded propeller blade are discussed. Preliminary allowables were determined based on coupon tests for the initial blade design. Nonstandard specimen geometries were investigated in order to provide valid failure modes and associated strength values for the spar, shell and adhesive bond joint in terms of static and fatigue strengths out to 108 cycles. Full-size blade component tests were performed to verify or substantiate the preliminary allowables. Analyses of failure modes on the full-size specimens directed the structural qualification process. This included follow-up coupon fatigue tests and expansion of the fullsize test matrix. The general conclusions are that coupon tests are necessary for determining elastic constants and for effects of batch variation, environment, and for shape of fatigue curves, but generally do not provide enough guidance to design a resin transfer molded (RTM) structure without some full-size test experience. This is due to the absence of edge, surface and width effects found in coupons and the inclusion of thermal, manufacturing and geometry effects found in the full-size specimens. These and other scale effect issues therefore dictate the need to test full-size specimens early on in the normal building block approach. The number of full-size tests is generally higher for an RTM blade or structure than for a metal blade or for a standard prepreg, thin composite structure, since statistical treatment of the full-size fatigue data is necessary for establishing final design allowables. This top-of-the-pyramid approach to structural qualification can make RTM unique from prepreg or metal structures.


    resin transfer molding, design allowables, propeller blade, braided materials, bond joints, fatigue analysis

    Author Information:

    Smith, SL
    Senior materials engineer and chief of Materials Engineering, Hamilton Standard, Windsor Locks, CT

    Mattavi, JL
    Senior materials engineer and chief of Materials Engineering, Hamilton Standard, Windsor Locks, CT

    Committee/Subcommittee: D30.05

    DOI: 10.1520/STP14511S

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