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Effects of infill patterns on the strength and stiffness of 3D printed topologically optimized geometries

Nadim S. Hmeidat (Mechanical, Aerospace and Biomedical Engineering Department, University of Tennessee, Knoxville, Tennessee, USA)
Bailey Brown (Mechanical Engineering and Mechanics Department, Lehigh University, Bethlehem, Pennsylvania, USA)
Xiu Jia (Mechanical Engineering and Mechanics Department, Lehigh University, Bethlehem, Pennsylvania, USA)
Natasha Vermaak (Mechanical Engineering and Mechanics Department, Lehigh University, Bethlehem, Pennsylvania, USA)
Brett Compton (Mechanical, Aerospace and Biomedical Engineering Department, University of Tennessee, Knoxville, Tennessee, USA and Materials Science and Engineering Department, University of Tennessee, Knoxville, Tennessee, USA)

Rapid Prototyping Journal

ISSN: 1355-2546

Article publication date: 18 August 2021

Issue publication date: 2 September 2021

570

Abstract

Purpose

Mechanical anisotropy associated with material extrusion additive manufacturing (AM) complicates the design of complex structures. This study aims to focus on investigating the effects of design choices offered by material extrusion AM – namely, the choice of infill pattern – on the structural performance and optimality of a given optimized topology. Elucidation of these effects provides evidence that using design tools that incorporate anisotropic behavior is necessary for designing truly optimal structures for manufacturing via AM.

Design/methodology/approach

A benchmark topology optimization (TO) problem was solved for compliance minimization of a thick beam in three-point bending and the resulting geometry was printed using fused filament fabrication. The optimized geometry was printed using a variety of infill patterns and the strength, stiffness and failure behavior were analyzed and compared. The bending tests were accompanied by corresponding elastic finite element analyzes (FEA) in ABAQUS. The FEA used the material properties obtained during tensile and shear testing to define orthotropic composite plies and simulate individual printed layers in the physical specimens.

Findings

Experiments showed that stiffness varied by as much as 22% and failure load varied by as much as 426% between structures printed with different infill patterns. The observed failure modes were also highly dependent on infill patterns with failure propagating along with printed interfaces for all infill patterns that were consistent between layers. Elastic FEA using orthotropic composite plies was found to accurately predict the stiffness of printed structures, but a simple maximum stress failure criterion was not sufficient to predict strength. Despite this, FE stress contours proved beneficial in identifying the locations of failure in printed structures.

Originality/value

This study quantifies the effects of infill patterns in printed structures using a classic TO geometry. The results presented to establish a benchmark that can be used to guide the development of emerging manufacturing-oriented TO protocols that incorporate directionally-dependent, process-specific material properties.

Keywords

Acknowledgements

This work is supported by the National Science Foundation (NSF) under Grant No. CMMI-1825815. The authors would also like to thank Mr Jake Dvorak and Mr Zane Palmer for assistance preparing test specimens and Dr Stephen Young and Mr Zach Arwood for assistance with shear tests.

Citation

Hmeidat, N.S., Brown, B., Jia, X., Vermaak, N. and Compton, B. (2021), "Effects of infill patterns on the strength and stiffness of 3D printed topologically optimized geometries", Rapid Prototyping Journal, Vol. 27 No. 8, pp. 1467-1479. https://doi.org/10.1108/RPJ-11-2019-0290

Publisher

:

Emerald Publishing Limited

Copyright © 2021, Emerald Publishing Limited

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