(Dr. Richard Neu, advisor)

"Study of Damage Evolution in a Titanium Matrix Composite at Quasi-static and Dynamic Strain Rate"

Abstract

Titanium matrix composites have received recent considerable attention as advanced aerospace structural materials. They posse unique combinations of several attractive properties such as high specific stiffness, high specific strength, excellent corrosion resistance, and good thermal stability. They can be applied in gas turbine engine, airframe for supersonic aircraft, and advanced energy conversion systems. However, the engineering databases for metal matrix composites are significantly lacking but are beginning to develop. The nature and properties of the interface fiber/matrix play a critical role in the performance and failure behavior of the composite. A significant amount of work aimed towards developing an understanding of the fundamental nature of the complex interfacial phenomena has been conducted. However most of the research on Ti composites reinforced with long SiC fibers have been directed on material with unidirectional reinforcement. Moreover there has been little research work performed at high strain rate on those materials. The purpose of this study is to develop an experimental understanding of the damage initiation and evolution of a titanium-carbon composite with cross-ply reinforcement fiber arrangement, at different strain rate. The first part focuses on tensile and bending behavior at quasi-static deformation rates. Understanding of the damage phenomenon is based on in-situ microscopic observations. The second part focuses on bending behavior at impact loading rate. Comprehension of damage evolution is based on energy balance methods and post damage investigation. Finally, results at different strain rate are discussed and compared.