SYMPOSIA PAPER Published: 01 January 1995
STP14682S

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

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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.

Author Information

Karpur, P
WL/MLLP, Materials Directorate, Wright Laboratory, Wright Patterson Air Force Base, OH
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
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Details
Developed by Committee: E08
Pages: 130–146
DOI: 10.1520/STP14682S
ISBN-EB: 978-0-8031-5308-0
ISBN-13: 978-0-8031-2003-7