STP486

    Material Toughness and Residual Strength of Damage Tolerant Aircraft Structures

    Published: Jan 1971


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    Abstract

    Fracture tests were conducted on precracked panels reinforced with various crack stoppers. Motion pictures and continuous graphical records of load and local strains were taken during the tests. The purpose of these tests was to study variables affecting residual strength of reinforced panels. Results show that, for 2024-T3 aluminum skin panels reinforced with riveted or bonded flat straps made of various alloys, the residual strength increases with the product of reinforcement area and reinforcement strength. Reinforcement stiffness, which is of primary importance for other classes of panel configurations, was found not to be a significant variable for the panel configurations tested. A crack opening displacement model is proposed to illustrate the influence of the reinforcements, the skin fracture toughness, and the slow stable tear characteristics on the arrest of a stably propagating crack. The model helps to elucidate the interactions between skin variables and reinforcement variables.

    Keywords:

    aircraft panels, reinforcement (structures), stiffening, fuselages, damage, fracture properties, toughness, residual stress, loads (forces), cyclic loads, strains, fatigue (materials), cracking (fracturing), crack propagation, mechanical properties, adhesive bonding, alloys, aluminum, fracture tests


    Author Information:

    Liu, AF
    Senior structures engineer and senior design specialist, Lockheed-California Co., Burbank, Calif.

    Ekvall, JC
    Senior structures engineer and senior design specialist, Lockheed-California Co., Burbank, Calif.


    Paper ID: STP26675S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP26675S


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