Observing the effect of infill shapes on the tensile characteristics of 3D printed plastic parts

Abstract

The term 3D printing is becoming more of a household term every day. From hobby enthusiasts to industrial production, 3D printing technology has generated great progress in the product and development sector. The ability to quickly go from an idea to a tangible product is the dream of any engineer. The potential for the types of parts that can be created using 3D printing is truly limitless. One major reason for this is the large number of customizable inputs the user can define before the printing process begins. One of the most important considerations, especially when dealing with structural components, is the type and percentage of part infill. This study takes a look at how the geometrical shape of this infill affects the mechanical properties, specifically tensile ones, of a given part. Specimen of rectangular, diamond, and hexagonal infill patterns were printed on an open source desktop printer using the fused filament fabrication (FFF) 3D printing method. A sampling of solid specimen were also printed in order to provide a baseline for comparison. These specimen were then subjected to tensile testing in accordance with the ASTM D638 standard. Unlike some other previously published studies, this study factored in the percent infill in regards to the cross-sectional area in the calculations performed. Load vs. elongation data was obtained from the TestWorks 4 software and exported to a spreadsheet for post-processing. This data was then converted to stress and strain values in order to construct stress vs. strain diagrams. Through the combined use of these diagrams and a few basic formulas, mechanical properties such as modulus, yield stress, ultimate tensile stress, and percent elongation were able to be determined for each geometrical infill configuration. The results for each shape were then compared and contrasted using both visual and tabulated means. A computer simulation was also done in order to reflect on the predictability of the printed specimen’s performance.