Experimental characterization of 3D printed cellular structures

Abstract

Due to the advancements in additive manufacturing the production of lattice structures has become feasible. These structures offer a higher design freedom than foams, which makes them interesting for lightweight applications, where an easy adaptation of the geometry is needed. To better understand the behavior of these structures several different unit cells are investigated. An octet-truss lattice, two types of auxetic structures and newly developed structures exhibiting anisotropic behavior are selected. Compression and tension tests are performed using 3D-printed specimens with different volume fractions. Two materials, polyamide and thermoplastic polyurethane, are selected, since they are suitable for the selective laser sintering process. The behavior of the structures depends on both the volume fraction and the bulk material properties. For the auxetic structures and the structures with anisotropic behavior the specific energy absorption was calculated, which also depends on the bulk material properties and is higher for the polyamide than for the thermoplastic polyurethane.While octet-truss structures have already been investigated, they still offer a good baseline for developing a test method. The behavior of 2D auxetic structures has been studied extensively, however, for 3D auxetic structures only little information is available. The novel anisotropic structures have not been examined in literature yet and are especially interesting for tailored mechanical behavior as the directional dependence can be used to better govern the local mechanical response.