Abstract

Octet-truss lattice materials have excellent potential for use as lightweight structures due to their high strength and stiffness, but low relative density. Octet-truss lattice specimens fabricated by stereolithography technique with a photopolymer resin were studied in this research. The unit cell orientation effects on the compressive fatigue behaviors of octet-truss lattices were studied using experimental analysis and computer simulation. A detailed comparison was made between the failure modes of static and fatigue failures, and the deformation mechanisms of lattices in different orientations under compressive cyclic load were determined. Both the static mechanical properties and fatigue properties of octet-truss lattices are highly dependent on the lattice orientation. When normalized with respect to their orientation-dependent Young’s moduli, the fatigue endurance of lattices in different orientations conforms very well (R² = 0.88) to a single S-N curve described by a power law. Finally, the differences in fatigue performance between lattices in different orientations were explained and a simple compression–compression fatigue mechanism was determined.

1. Highlights

2. Compressive fatigue behaviors of octet-truss lattice structures in three different unit cell orientations were investigated and compared in this research. Orientation-Z structure has the best resistance to fatigue failure in comparison to other orientations.

3. The absolute S–N curves of lattices in different orientations were normalized by their Young’s moduli into a curve that can be expressed by one single power law.

4. The mechanism of compressive fatigue failure of octet-truss lattice structures in different orientations was determined. Comparing with fatigue crack initiation and propagation in struts, cyclic ratchetting made dominant contribution to the compressive fatigue failure.

5. The differences between the fatigue resistances of lattices in three orientations were explained by comparing the mechanical response in the finite element model.

摘要

Octet-truss 晶格材料由于其高强度和刚度，但相对密度低，因此具有用作轻质结构的巨大潜力。在这项研究中，研究了通过立体光刻技术用光聚合物树脂制造的八角桁架点阵样品。使用实验分析和计算机模拟研究了晶胞取向对八位组桁架晶格压缩疲劳行为的影响。详细比较了静态和疲劳失效的失效模式，确定了不同取向晶格在压缩循环载荷作用下的变形机制。八位组桁架晶格的静态力学性能和疲劳性能都高度依赖于晶格取向。R ² = 0.88) 到由幂律描述的单个 SN 曲线。最后，解释了不同取向晶格之间疲劳性能的差异，并确定了简单的压缩-压缩疲劳机制。

1. 强调

2. 本研究研究并比较了三种不同晶胞取向的八角组桁架晶格结构的压缩疲劳行为。方向 - Z结构与其他方向相比具有最佳的抗疲劳失效能力。

3. 不同方向晶格的绝对 S-N 曲线通过其杨氏模量归一化为一条可以用一个单一幂律表示的曲线。

4. 确定了不同方向的八角组桁架点阵结构压缩疲劳失效的机理。与支柱中的疲劳裂纹萌生和扩展相比，循环棘轮效应对压缩疲劳失效起主导作用。

5. 通过比较有限元模型中的机械响应，解释了三个方向晶格的疲劳抗力之间的差异。