Mechanistic understanding of compression-compression fatigue behavior of functionally graded Ti-6Al-4V mesh structure fabricated by electron beam melting

In recent years, mesh structures have attracted significant interest for structural and functional applications. However, the mechanical strength and energy absorption ability of uniform mesh structured materials degrade with density. To address this challenge, we propose the concept of functionally graded mesh structures. The objective of the proposed research is to fundamentally understand the compressive behavior of graded mesh structures. The compression-compression fatigue behavior of functionally graded Ti-6Al-4V mesh structure under identical bulk stress condition is studied here. During cyclic deformation, it was observed that the local stress distribution in the struts was not uniform because of inhomogeneous mechanical properties of the constituents. Fatigue cracks first initiated in the lowest strength constituent, and then propagated until structural failure occurred. However, no obvious damage was observed in other constituents during the entire process. In contrast with iso-strain state, the fatigue life of graded structure is mainly determined by the constituent with the lowest strength.