STP1274

    Characterization of Localized Failure Modes in Honeycomb Sandwich Panels Using Indentation

    Published: Jan 1996


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    Abstract

    The indentation behavior of aircraft floor panels (honeycomb sandwich structures) was investigated from the viewpoints of test methodology, effects of panel construction, and failure mechanisms. An indentation test method using a simply-supported plate was developed to replicate observed in-use failure modes. The localization and type of damage induced with this test method correlated extremely well with damage present in panels returned from airlines suggesting that highly-concentrated loads, such as from high heels, cause most panel damage. Furthermore, damage appeared to spread due to an accumulation of multiple damage events more so than propagating from only a few. Both aramid- and aluminum-cored panels showed failures that occurred just below the resin fillet on the top skin. Aramid failed in brittle compression and post-buckling whereas aluminum failed due to ductile buckling. These results strongly indicate that near-surface properties dominate indentation behavior in contrast to the core-dominated stabilized core compression test as well as the skin-dominated failure criteria used in ASTM-type impact tests. Indentation tests using various skin and core constructions demonstrated the influence of changing core density, core material, and skin construction as well as the synergistic effect of skin and core on indentation damage resistance. Several analytical models were examined to aid in understanding the failure mechanisms due to indentation. These suggest that large local skin deflections are important in local load redistribution leading to core failure.

    Keywords:

    composite materials, testing, design, honeycomb sandwich structures, panel construction, failure mechanisms, indentation test method


    Author Information:

    Tsotsis, TK
    Staff scientist and director, Materials Science, CIBA Composites, Anaheim, CA

    Lee, SM
    Staff scientist and director, Materials Science, CIBA Composites, Anaheim, CA


    Paper ID: STP16543S

    Committee/Subcommittee: D30.09

    DOI: 10.1520/STP16543S


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