STP569

    Fatigue and Shakedown in Metal Matrix Composites

    Published: Jan 1975


      Format Pages Price  
    PDF Version (356K) 24 $25   ADD TO CART
    Complete Source PDF (7.3M) 24 $102   ADD TO CART


    Abstract

    Simple mechanical models of unidirectional metal matrix composites are used to analyze elastoplastic deformation and shakedown in the matrix under cyclic composite loads. Both axial and off-axis loadings of a lamina are considered. It is shown that the fatigue limits of as-fabricated boron-aluminum, beryllium-aluminum, tungsten-copper, and other composites generally coincide with the composite shakedown limits because the matrix yield stresses and fatigue limits are equal.

    In heat-treated composites, the matrix yield stress is usually much higher than the fatigue limit, and matrix fatigue failure can take place in the shakedown state. The residual microstresses caused by heat treatment are estimated, and their influence on fatigue is discussed. A method for improvement of the fatigue resistance of heat-treated composites is discussed.

    The theoretical predictions of fatigue limits are verified by an extensive comparison with available experiments, and a very good agreement is obtained. It is concluded that, in principle, the composite fatigue failure can be avoided if each of the constituents is stressed within its particular fatigue limits during a cyclic loading program of the composite.

    Keywords:

    composite materials, fibers, aluminum, beryllium, boron, copper, tungsten, reinforcement (structures), fatigue (materials), fatigue limit, cyclic loads


    Author Information:

    Dvorak, GJ
    Professor of civil engineering and graduate assistant, Duke University, Durham, N. C.

    Tarn, JQ
    Professor of civil engineering and graduate assistant, Duke University, Durham, N. C.


    Paper ID: STP33171S

    Committee/Subcommittee: E08.09

    DOI: 10.1520/STP33171S


    CrossRef ASTM International is a member of CrossRef.