Fatigue Behavior of a Functionally-Graded Titanium Matrix Composite

摘要

Functionally-graded Titanium Matrix Composites are an attempt to utilize the high-strength properties of a titanium matrix composite with a monolithic alloy having the more practical machining qualities. This work studied the mechanical characteristics of the joint region as a first step toward future evaluation of this material. The scope of this effort involved testing under monotonic tension and fatigue loading conditions. Mechanical properties and cyclic behavior were evaluated for the joint area and then compared to those of the parent materials. The results of this study found that the strength of the transition region was slightly higher than the unreinforced alloy. However, the presence of fiber ends in the transition region proved to be the source of failure under fatigue loading conditions. Failure in the transition region did not occur at the tip of the taper joint as anticipated. Instead, failure occurred at the transition to the next ply in the taper. This indicates that fiber volume, in conjunction with the presence of fiber ends, plays a key role in the fatigue life of the entire material. These findings encourage and provide the basic scientific knowledge for further evaluation and development of functionally-graded titanium matrix composites.