STP972

    Automated Design of Composite Plates for Improved Damage Tolerance

    Published: Jan 1988


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    Abstract

    This paper is a first step toward automating the design for local damage tolerance of composite plates under compressive loadings simulating the local damage condition by a central through-the-thickness crack-like notch. Based on recent experimental investigations, the failure mode is assumed to be shear crippling, believed to be the result of kinking failure of the principal load-carrying fibers at a point of stress concentration in a laminate. The paper utilizes a microme-chanical failure model for the fiber kink formation in the load-carrying layers accounting for the combined effects of compressive and shearing stresses around the notch.

    A previously developed code for cracked plates under tensile loading is used for the design purpose. The design code combines a finite-element analysis program with an optimization program and an automated mesh generation interface program. Minimum weight designs are achieved for stiffened and unstiffened plates subject to a constraint that a crack will not grow by fiber kinking failures. Design variables are ply thicknesses in different regions of the plates. Stiffened plates with four stiffeners that are assumed to be perfectly bonded to the plate section are considered. For stiffened plates, minimum weight configurations are obtained where the crack is isolated in low stiffness plate regions.

    Keywords:

    composite plates, optimization, damage tolerance, cracks, compressive loading, fiber kinking


    Author Information:

    Gürdal, Z
    Assistant professor, Department of Engineering Science and Mechanics, and professor, Aerospace and Ocean Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA

    Haftka, RT
    Assistant professor, Department of Engineering Science and Mechanics, and professor, Aerospace and Ocean Engineering Department, Virginia Polytechnic Institute and State University, Blacksburg, VA


    Paper ID: STP26125S

    Committee/Subcommittee: D30.02

    DOI: 10.1520/STP26125S


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