A Study on Mechanical Behavior of 3D Printed Elastomers with Various Infills and Densities

Obtaining the mechanical properties of 3D printed elastomers is a difficult task given the large variety of combinations with respect to materials and process parameters. Specifically, with Fused-Filament-Fabrication (FFF) printers, the tool path to lay-down lines of material can be modified for both the external and internal portions of the part. The internal structures are referred to as infill patterns and are akin to lattice structures. In this paper, we investigate the effect of infill pattern and infill density on both the working range of common elastomeric applications and the break characteristics. A commercial slicer is used to generate six patterns with a variety of shapes and different alignments to the tensile direction. With the infill patterns selected, the samples are printed using a FFF 3D printer at different infill densities. Finally, the properties of the samples are acquired through tensile tests. The characteristics at break, the inflection point, and the behavior of the working range are then presented and analyzed. Current literature on 3D printed structures mostly focuses on reporting break characteristics for different infill patterns, with no mention of its relationship to the working range. Additionally, lack of reproducibility of their results limits their applicability. As most common applications of elastomeric materials have a working range within 45% strain, the behavior within this region needs to be analyzed as well. This paper answers two hypotheses: increasing the density, regardless of infill pattern, will uniformly increase break characteristics; and increasing the break characteristics will similarly decrease the softening behavior of the eccentric elasticity zone. The paper presents three key findings. First, density's relative effect on tensile properties increases as density increases. Second, the working rangefollows similar trends, in terms of strongest and weakest samples, to the break characteristics. However, the relative behavior of all samples in the working range remained constant regardless of pattern or density. Last, it was found that both the inflection point, where the elastomer goes from softening to stiffening, and the softening rate of the working range, are independent to infill pattern and density. Understanding the underlying effects of 3D printing parameters such as infill pattern and infill density can guide the generation of new patterns to address specific applications. (c) 2023 The Authors. Published by ELSEVIER Ltd. This is an open access article under the CC BY-NC-ND license (http: //creativecommons.org /licenses /by-nc-nd /4.0)