Investigation of energy absorption and crushing behaviors of lattice materials under static and dynamic loads

Lattice materials have a number of superior properties compared to dense solids, such as low weight, high strength and high energy absorption capacity. Because of these superior properties, lattice materials are widely used as structural components in various industries, including machinery, construction, aerospace, automotive, biomedical and personal protective equipment. In recent years, advancements in additive manufacturing technologies have made it possible to produce lattice materials with complex geometries that cannot be produced with traditional production methods. Furthermore, with the development of technology, the need for materials with higher energy absorption capacity has increased, making the study of energy absorption and crushing behavior of lattice materials with different unit cell geometries an important research area. However, although the research on such materials is growing rapidly, it is predominantly limited to hexagonal and other classical lattice materials. In this study, the in-plane energy absorption and crushing behaviors of five new isotropic lattice materials (C Tekoğlu. Truss-lattice materials consisting of mixed polygons, 2023. World Intellectual Property Organization, Application Number: PCT/TR2022/051154.) with superior mechanical properties, namely Mixed Hexagonal-2 Triangular, Hierarchical-3 Triangular, Modified Kagome-I, Modified Kagome-II and Modified Kagome-III, were investigated by finite element analyses. The results were compared with analyzes of Hexagonal and Triangular-Triangular lattices. By observing crushing behaviors of lattice matertials, three different deformation modes were defined according to the crushing velocity: quasi-static, transition and dynamic mode. The energy absorption and crushing behaviors were compared using five different metrics that are often used in the literature: densification strain, peak crushing stress, mean plateau stress, energy absoprtion and ideality parameter. Modified Kagome-II lattice together with Triangular-Triangular lattice structure have the lowest energy absorption capacity in quasi-static and transition modes. The Mixed Hexagonal-2 Triangular, Hierarchical-3 Triangular, Modified Kagome-I, and Modified Kagome-III lattice structures exhibited, compared to the Hexagonal lattice, approximately 19.6%, 20.2%, 19%, and 27% higher energy absorption capacities in static mode, and 17%, 11.6%, 10.8%, and 29.5% higher energy absorption capacities in transition mode, respectively. In dynamic mode, the hexagonal lattice has the lowest energy absorption capacity. The Mixed Hexagonal-2 Triangular, Hierarchical-3 Triangular, Triangular-Trianglar, Modified Kagome-I, Modified Kagome-II, and Modified Kagome-III lattice structures have higher energy absorption capacities in dynamic mode compared to the Hexagonal lattice, 22.5%, 5%, 5.1%, 9.9%, 10.8%, and 26.1% higher energy absorption capacities, respectively. The lattice with the highest energy absorption capacity in all deformation modes is the Modified Kagome-III. In terms of the ideality parameter, the Hierarchical-3 Triangular lattice structure exhibited the closest behavior to an ideal energy absorber. Overall, this study clearly reveals that the lattices studied in the thesis are important competitors to Hexagonal and other classical lattice materials, which are frequently used in energy absorption and crushing applications.