Metallic lattice structures are well known for having high specific elastic moduli and strength. However, very little is understood about their resistance to fracture. In this work Ti–6Al–4V lattice structures are additively manufactured by selective laser melting and their fracture toughness characteristics are investigated. Resistance to fracture was determined under Mode-I loading at static rates using an extended compact tension (EC(T)) specimen, modified to contain lattice cells. The lattices consist of octet cells with a 3.5 mm edge length and relative densities ranging from 25% to 56%. Toughness is shown to increase by a power law with relative density and this trend was also obtained with finite element models. A new functional grading optimisation methodology is also presented for increasing fracture toughness. The size optimisation results in a functionally graded lattice whereby lattice truss diameters become the design variables. After size optimisation, initiation fracture toughness increases by up to 37%.

金属晶格结构具有高的比弹性模量和强度是众所周知的。然而，关于它们的抗断裂性了解甚少。在这项工作中，通过选择性激光熔炼来添加Ti-6Al-4V晶格结构，并研究其断裂韧性特征。使用扩展的紧凑张力（EC（T））样品，在I型载荷下以静态速率确定了抗断裂性，该样品经过修饰以包含晶格单元。晶格由边缘长度为3.5 mm的八位位组组成，相对密度为25％至56％。韧性通过相对密度的幂定律增加，并且这种趋势也可以通过有限元模型获得。还提出了一种新的功能分级优化方法，以提高断裂韧性。尺寸优化可生成功能渐变的晶格，其中晶格桁架直径成为设计变量。优化尺寸后，初始断裂韧性提高了37％。