FRACTURE STRENGTH AND DAMAGE PROGRESSION OF THE FIBER MATRIX INTERFACES IN TITANIUM-BASED MMCS WITH DIFFERENT INTERFACIAL LAYERS/

In this paper, a concerted utilization of finite element analysis and an ultrasonic characterization technique is described to assess the in terfacial fracture strength and to monitor the progression of damage a t the interfacial region in titanium-based metal-matrix composites. Th e finite element model developed here encompasses an interfacial eleme nt with a finite thickness to simulate the interfacial region of the c oating or reaction products. The finite element model has been used in conjunction with the ultrasonic evaluation technique to assess the in situ interfacial fracture strength. The different responses of the ul trasonic amplitudes for Ti-6Al-4V/SCS-0 SiC and Ti-6Al-4V/SCS-6 SiC in terfaces 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 betwe en 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. (C ) 1998 Elsevier Science Limited. All rights reserved.