Volume 14, Issue 1 (March 1992)

    Redesign of the Mixed-Mode Bending Delamination Test to Reduce Nonlinear Effects

    CODEN: CTROAD

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    Abstract

    The mixed-mode bending (MMB) test uses a lever to apply simultaneously Mode I and Mode II loading to a split-beam specimen. An iterative analysis that accounts for the geometric non-linearity of the MMB test was developed. The analysis accurately predicted the measured load-displacement response and the strain energy release rate, G, of an MMB test specimen made of APC22 (AS4/PEEK). The errors in G when calculated using linear theory were found to be as large as 30% in some cases. Because it would be inconvenient to use a nonlinear analysis to analyze MMB data, the MMB apparatus was redesigned to minimize the nonlinearity. The nonlinear analysis was used as a guide in redesigning the MMB apparatus. With the improved apparatus, loads are applied just above the midplane of the test specimen through a roller attached to the lever. This apparatus was demonstrated by measuring the mixed-mode delamination fracture toughness of APC2. The nonlinearity errors associated with testing this tough composite material were less than ±3%. The data from the improved MMB apparatus analyzed with a linear analysis were similar to those found with the original apparatus and the nonlinear analysis.


    Author Information:

    Crews, JH
    Research engineer and senior scientist, NASA Langley Research Center, Hampton, VA

    Reeder, JR
    Research engineer and senior scientist, NASA Langley Research Center, Hampton, VA


    Stock #: CTR10078J

    ISSN: 0884-6804

    DOI: 10.1520/CTR10078J

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    Author
    Title Redesign of the Mixed-Mode Bending Delamination Test to Reduce Nonlinear Effects
    Symposium , 0000-00-00
    Committee D30