ASSESSMENT OF FRACTURE STRENGTH OF THE FIBER/MATRIX INTERFACES IN TITANIUM-BASED METAL MATRIX COMPOSITES
Prezone Karpur, Theodore E. Matikas, Robert L. Crane, S. Krishnamurthy *, Leon L. Shaw** USAF Wright Laboratory Materials Directorate (UDRI), WL/MLLP Wright-Patterson Air Force Base, OH 45433-7817 *USAF Wright Laboratory Materials Directorate (UES, Inc. ), WL/MLLM Wright-Patterson Air Force Base, OH 45433-7817 **Department of Metallurgy, Institute of Materials Science, University of Connecticut, Storrs, CT, 06269, U. S. A.
In this paper, a concerted utilization of finite element analysis and an ultrasonic characterization technique is described to assess the interfacial fracture strength and to monitor the progression of the damage at the interfacial region in titanium- based MMCs. The finite element model developed here encompasses an interfacial element with a finite thickness to simulate the interfacial region of the coating or reaction products. The FEA model has been used in conjunction with the ultrasonic evaluation technique to assess the in-situ interfacial fracture strength. The different responses of the ultrasonic amplitudes for Ti-6Al-4V/SCS-0 SiC interface and Ti-6Al-4V/SCS-6 SiC interface have been explained in terms of the reflection of ultrasonic waves from the fiber/matrix interface. It is established that the non- monotonic stress dependence of the ultrasonic reflection amplitude for both the SCS-0 and SCS-6 interfaces is related to the debonding between the fiber and matrix. The results indicate that the SCS-0 interface has a much higher fracture strength than the SCS-6 interface although both these interfaces exhibit similar apparent debonding stresses. Further, samples containing fully embedded fibres are used to further determine the fracture strength thereby eliminating the effects of tensile residual stress imposed when the fiber tips are exposed to the surface.
Publication Source: Trends in NDE Science & Technology; Proceedings of the 14th World Conference on Non-Destructive Testing, New Delhi, 8-13 December 1996.Vol. 1, pages 149 - 152 Publisher:Ashgate Publishing Company
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