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    STP1285

    The Influence of Transverse Bearing Loads Upon the Bypass Strength of Composite Bolted Joints

    Published: 0


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    Abstract

    The performance of biaxially loaded composite joints was examined at the coupon level using a simple, low-cost test apparatus designed to apply transverse bearing loads independent of longitudinal bypass loads. The apparatus consisted of clevises, load links, and attachments to test machine supports. Bending and extensional strain gage bridges were placed on the load links to measure transverse bearing stress levels as longitudinal bypass loads were applied and used to determine when bearing damage initiated. Two laminate configurations were examined to compare transverse bearing effects in relatively high and low stiffness laminates. At low bearing stress levels, transverse bearing was found to be a less damaging load condition than longitudinal on-axis bearing; however, bearing-related failure modes became prominent at lower stress levels in the transverse loading case than in the on-axis case. High stiffness laminates exhibited greater sensitivity to transverse hole deformation, laminate damage, and fastener torque than low stiffness laminates. Experimental data were compared with failure predictions generated with the Boeing-developed BEARBY analysis code. Predictions for the high stiffness laminate were in general agreement with test results, but were conservative for the low stiffness laminate as bearing damage relieved the stress concentration.

    Keywords:

    fatigue (materials), fracture (materials), composite materials, bolted composite joints, biaxial loading, bearing-bypass interaction, bolt torque, hole elongation


    Author Information:

    Sawicki, A
    Technical specialists, Structures Technology, Boeing Defense & Space Group, Philadelphia, PA

    Nguyen, N
    Technical specialists, Structures Technology, Boeing Defense & Space Group, Philadelphia, PA


    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP19930S