PSI - Issue 37

Yifan Li et al. / Procedia Structural Integrity 37 (2022) 49–56 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

53 5

where P cr is the critical load when specimen fractured. a is the cack length, B is the specimen thickness and W is the specimen width.

Fig. 5. The displacement-load curves of octet-truss lattices.

The geometrical values of lattice specimens in different orientations are shown in Table. 1. Substituting the critical load P cr we obtained from fracture tests and the geometrical values into Eqs. (1) and (2), stress intensity factors at fracture can be calculated. The fracture resistances of orientations X, Y and Z lattices are 5.72, 8.52 and 8.49MPa √ mm, respectively.

Table 1. The geometry of octet-truss lattices in different orientations. Orientation a (mm) W (mm)

B (mm)

X Y Z

27 24 26

80 83 83

25 25 25

Photographs of the lattices taken during and after fracture for different orientations are shown in Fig. 6. The fracture in different orientations lattices initiates at the struts adjacent to the crack tip. Once the first strut failed, the specimen quickly broken into two pieces. Most failures in struts occurred at the location near to the joint caused by the influence of local stress concentration. The crack paths for orientations X and Z specimens were almost horizontal to the initial crack. While the crack of orientation-Y specimen deviated from the initial crack and the entire crack plane was rotated by 30◦ to the initial crack plane. The experimental phenomena are consistent with the prediction results in the literature (Gu et al. 2019).