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    STP1285

    Evaluation of Damage Evolution and Material Behavior in a Sigma/Ti-6242 Composite Using Nondestructive Methods

    Published: 0


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    Abstract

    Correlations between damage, as it evolves under simulated service conditions, and the results produced from nondestructive evaluation (NDE) techniques are useful in establishing successful life prediction methodologies in metal-matrix composites. Traditional characterization techniques provide limited information on the failure mechanisms in metal-matrix composites because of the complexities caused by the inhomogeneous, anisotropic nature of these materials. In addition, the currently used destructive techniques yield only qualitative information on the internal damage of composites. Very little quantitative information exists correlating the internal damage with property changes in the material such as stiffness, elongation, and residual strength. This research effort correlated NDE results with the residual tensile strength of a six-ply, unidirectional BP Sigma-1240 SiC/Ti-6Al-2Sn-4Zr-2Mo composite after being isothermally fatigued. Baseline tension and fatigue curves were initially generated since minimal information on this particular metal-matrix composite was available in the literature. Information obtained from these tests was used to pinpoint load levels and interruption points for subsequent interrupted fatigue tests. The following nondestructive evaluation techniques were used to evaluate the test specimens before and after fatigue testing: (1) scanning acoustic microscopy, (2) oblique incidence shear wave scanning, (3) reflector plate ultrasonic scanning, (4) immersion surface wave scanning, (5) in situ surface and longitudinal waves and, (6) X-ray radiography. Following the interrupted fatigue tests, the composite specimens were nondestructively evaluated again prior to the residual tension tests to determine the residual strength. Scanning electron microscopy and metallography were used in the correlation and verification of fatigue damage. From these results, the immersion surface wave technique proved to be the most promising method for correlating damage with the residual tensile strength for this particular composite. This paper presents the results from each of the NDE techniques and examines the correlation among the techniques, other destructive methods, and the residual tensile strength.

    Keywords:

    nondestructive evaluation, metal-matrix composites, residual tensile strength, isothermal fatigue, scanning acoustic microscopy, oblique incidence shear waves, reflector plate inspection, in situ surface acoustic waves, in situ longitudinal acoustic waves, fatigue (materials), fracture (materials), composite materials


    Author Information:

    Benson, D
    Graduate student, associate professor and research engineer, associate research engineer and associate research engineer, University of Dayton Research Institute, Dayton, OH

    Karpur, P
    Graduate student, associate professor and research engineer, associate research engineer and associate research engineer, University of Dayton Research Institute, Dayton, OH

    Stubbs, DA
    Graduate student, associate professor and research engineer, associate research engineer and associate research engineer, University of Dayton Research Institute, Dayton, OH

    Matikas, TE
    Graduate student, associate professor and research engineer, associate research engineer and associate research engineer, University of Dayton Research Institute, Dayton, OH


    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP19944S