Fatigue of octet-truss lattices manufactured by Laser Powder Bed Fusion

The octet-truss lattice is a three-dimensional lattice with high strength and low density. Practical use of these lattices requires a knowledge of their resistance to fatigue crack growth. Lattice specimens manufactured by laser powder bed fusion technique were prepared with different orientations to explore the orientation effects on lattice fatigue behaviour. X-ray tomography was used to measure the surface roughness of the lattice struts, and also used to validate the accuracy of the crack length measurement by compliance method. The experimental results show that the fatigue crack growth rate and crack growth path depend on the orientation of the lattice. A finite element prediction of the fatigue life of the lattice was carried out, based on measurements of the fatigue life of single struts cut from the lattice. The finite element predictions were in good agreement with the experimental results. A procedure for predicting the crack growth path was proposed. These findings can help designers optimize the orientation of lattice structures in structural applications.