Investigating the effect of microstructural defects arising from the additive manufacturing process including variable diameter and bond distortion on the rate-dependent response of a symmetric twelve-layer lattice material made of Ti6Al4V alloy

In recent years, the use of lattice materials has increased in various industries due to their unique properties such as high strength to weight, impact absorption properties, low density and adjustable properties. Although the use of additive manufacturing technology is considered a suitable solution for the manufacture of this category of materials, despite the microstructural defects arising from this production process, the control of the mechanical properties of these materials has faced challenges. In this article, the effect of two defects of variable diameter and bond distortion on the strain-rate-dependent response of a symmetric twelve-layer lattice material made of Ti6Al4V alloy has been investigated. For this purpose, a finite element model based on the Timoshenko beam element has been developed to consider these two types of defects and is validated using the available experimental data for a strain rate of 1000/s. The results show that increasing the amount of both types of defects leads to a decrease in the stress level in the stress-strain curve. Also, increasing the variable diameter defect has reduced the fluctuation of this curve in the non-linear area, while the distortion of the links does not have much effect on this matter. Examining the elastic modulus indicates that the increase in diameter changes along each link causes the elastic modulus to decrease almost linearly, while the increase in distortion of the link reduces the elastic modulus with an almost quadratic relationship. By increasing the average diameter of the grafts, the effect of variable diameter defects and graft distortion increases and decreases, respectively.