STP1251

    Nondestructive Crack Size and Interfacial Degradation Evaluation in Metal Matrix Composites Using Ultrasonic Microscopy

    Published: Jan 1995


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    Abstract

    Ultrasonic scanning acoustic microscopy is a nondestructive method useful for material elastic property quantification as well as crack size determination for surface and subsurface cracks. The advantage of the method over destructive methods for crack size determination is that the imaging technique can provide the crack sizing information while helping in the detection of interface degradation and early crack initiation so that their growth can be monitored during interrupted fatigue tests. Various metal matrix composite systems with titanium based matrix and SCS-6 fibers have been evaluated for this study [Ti-24Al-11Nb (atomic percent), Ti-6Al-2Sn-4Zr-2Mo (weight percent), and Ti-15Mo-3Nb-3Al-0.2Si (weight percent)]. The scanning acoustic microscope technique has been applied to materials subjected to both room temperature and elevated temperature fatigue cycling in addition to thermomechanical fatigue (in-phase and out-of-phase) conditions. A 50 MHz scanning acoustic microscope has been used for the imaging and evaluation of the damage initiation and growth of surface/subsurface cracks and interfacial degradation. All the images have been produced by exploiting the surface wave component of the ultrasonic signals from the scanning acoustic microscope because of the higher sensitivity of surface waves to both surface/subsurface cracks and perhaps also due to the changes in interfacial elastic properties. The results shown in this paper provide a very good understanding of the crack initiation and growth as well as interfacial degradation process of titanium based metal matrix composites when subjected to cyclical stresses at elevated temperatures and room temperature. The results indicate that the combination of high temperature and stress is very severe to the interface between the matrix and the fiber.

    Keywords:

    metal matrix composites, thermomechanical behavior, interfacial damage, nondestructive evaluation, ultrasound, scanning acoustic microscope, crack sizing, crack growth, crack initiation, Rayleigh waves, interfacial degradation, environmental effects


    Author Information:

    Karpur, P
    Research Institute, University of DaytonWL/MLLP, Materials Directorate, Wright Laboratory, DaytonWright Patterson Air Force Base, OHOH

    Matikas, TE
    National Research Council Associate, WL/MLLP, Materials Directorate, Wright Laboratory, Wright Patterson Air Force Base, OH

    Blodgett, MP
    WL/MLLP, Materials Directorate, Wright Laboratory, Wright Patterson Air Force Base, OH

    Jira, JR
    WL/MLLN, Materials Directorate, Wright Laboratory, Wright Patterson Air Force Base, OH

    Blatt, D
    WL/MLLN, Materials Directorate, Wright Laboratory, Wright Patterson Air Force Base, OH


    Paper ID: STP14682S

    Committee/Subcommittee: E08.06

    DOI: 10.1520/STP14682S


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