Session: 02-01-06: 7th Annual Conference-Wide Symposium on Additive Manufacturing: Unique Applications II

Paper Number: 99266

99266 - 3d Printed and Foamed Triply Periodic Minimal Surface Lattice Structures for Energy Absorption Applications in Engineering Industry 

Structures currently used in engineering industry for energy absorption include foams, composites, and honeycombs. While these structures have proven sufficient, they still have limitations concerning their ultimate strength and the amount of energy they can absorb. In an effort to find structures that exceed in these aspects, recent studies indicate the potential of triply periodic minimal surfaces (TPMS) for use in energy absorption applications as well as weight reduction. TPMS structures originate from a minimal surface, are thickened, and then replicated in three dimensions to form a lattice. They portray beneficial characteristics such as being lightweight with high stress tolerance. This study presents three TPMS lattice structures, namely the Gyroid, Fischer-Koch S, and PMY, which are fabricated in uniform and graded densities. These structures were firstly created digitally in the MSLattice software and were then 3D printed using the Markforged and Makerbot printers with Onyx and Polylactic acid filament, respectively. Onyx is a high-performance composite filament made up of nylon and chopped carbon fiber, making it potentially useful for lightweight and high thermal and strength applications. Furthermore, the polylactic acid samples underwent a solid-state foaming process to investigate benefits of higher porosity in energy absorption. The goal of foaming is to introduce a second level of porosity within the internal structure; this was done by saturating the samples with carbon dioxide in a pressure vessel at 2.8 MPa for about 3 hours under ambient conditions. The specimens embedded with gas are removed from the pressure vessel and foamed for either 10 or 20 seconds in water at 90 C. This creates a thermodynamic instability in the structure and as the gas is diffusing out of the samples, pores are generated within the structure. The Onyx and PLA structures were then characterized for compressive strength, porosity, and energy absorption. The results of the study show that the graded Fischer-Koch S structure, 3D printed with a composite base material (Onyx), withstood 5,821 N at 25 percent deformation and achieved an energy absorption value of 2.38 MJ/m­³, the most of any structure, while the PLA-based graded PMY structure exhibited the greatest compression modulus, at 28.64 MPa. Moreover, all the graded structures portrayed less deformation at 1000 N in comparison to the uniform structures. Additionally, four of the six-foamed PLA samples achieved a higher energy absorption value in comparison to its un-foamed state, validating the solid-state foaming process as a viable solution to increasing the energy absorption of a rigid structure. The values of porosity due to the gas foaming range from 33% to 53%. These values represent the amount of solid content of the TPMS structures, and the structures as a whole have a combined porosity in excess of 75%. Lastly, the results are discussed to infer possible applications in engineering industry.

Presenting Author: Sriharsha Sundarram Fairfield University

Presenting Author Biography: Sriharsha S. Sundarram, PhD is an Associate Professor of Mechanical engineering at Fairfield University, CT. He received his PhD in Mechanical Engineering from The University of Texas at Austin in 2013. He received his master’s degree from Texas A&M University in Mechanical Engineering and bachelor’s degree in Manufacturing Engineering from College of Engineering (Guindy), India. He teaches courses in design, manufacturing and materials. Dr. Sundarram’s current research interest is in the area of micro/nano manufacturing, specifically large-scale processing of advanced micro/nano-structured materials with applications in energy, thermal management and biomedicine. The work is interdisciplinary encompassing manufacturing, materials, chemistry and numerical modeling. The eventual goal of the research group is to be able to fabricate metal foams with pore sizes on the order of tens of nanometers.

Authors:

Dylan Weber Fairfield University
Sriharsha Sundarram Fairfield University