scholarly journals Energy Absorption and Mechanical Performance of Functionally Graded Soft–Hard Lattice Structures

Materials ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1366 ◽  
Author(s):  
Hafizur Rahman ◽  
Ebrahim Yarali ◽  
Ali Zolfagharian ◽  
Ahmad Serjouei ◽  
Mahdi Bodaghi
Keyword(s):  
Cell Size ◽  
Energy Absorption ◽  
Mechanical Performance ◽  
Lattice Structure ◽  
Unit Cell ◽  
Lattice Structures ◽  
Hard Materials ◽  
Unit Cell Size ◽  
Rational Combination ◽  
Dual Material

Today, the rational combination of materials and design has enabled the development of bio-inspired lattice structures with unprecedented properties to mimic biological features. The present study aims to investigate the mechanical performance and energy absorption capacity of such sophisticated hybrid soft–hard structures with gradient lattices. The structures are designed based on the diversity of materials and graded size of the unit cells. By changing the unit cell size and arrangement, five different graded lattice structures with various relative densities made of soft and hard materials are numerically investigated. The simulations are implemented using ANSYS finite element modeling (FEM) (2020 R1, 2020, ANSYS Inc., Canonsburg, PA, USA) considering elastic-plastic and the hardening behavior of the materials and geometrical non-linearity. The numerical results are validated against experimental data on three-dimensional (3D)-printed lattices revealing the high accuracy of the FEM. Then, by combination of the dissimilar soft and hard polymeric materials in a homogenous hexagonal lattice structure, two dual-material mechanical lattice statures are designed, and their mechanical performance and energy absorption are studied. The results reveal that not only gradual changes in the unit cell size provide more energy absorption and improve mechanical performance, but also the rational combination of soft and hard materials make the lattice structure with the maximum energy absorption and stiffness, in comparison to those structures with a single material, interesting for multi-functional applications.

Determination of Optimal Unit-Cell Size of Homogeneous Conformal Unit-Cell Lattice Structure Using Solid Shape Matching

2016 ◽  
Author(s):  
Mahmoud A. Alzahrani ◽  
Seung-Kyum Choi
Keyword(s):  
Cell Size ◽  
Solid Body ◽  
Strain Energy ◽  
Lattice Structure ◽  
Weight Ratio ◽  
Unit Cell ◽  
Optimal Size ◽  
Lattice Structures ◽  
Unit Cell Size ◽  
Unit Cells

With rapid developments and advances in additive manufacturing technology, lattice structures have gained considerable attention. Lattice structures are capable of providing parts with a high strength to weight ratio. Most work done to reduce computational complexity is concerned with determining the optimal size of each strut within the lattice unit-cells but not with the size of the unit-cell itself. The objective of this paper is to develop a method to determine the optimal unit-cell size for homogenous periodic and conformal lattice structures based on the strain energy of a given structure. The method utilizes solid body finite element analysis (FEA) of a solid counter-part with a similar shape as the desired lattice structure. The displacement vector of the lattice structure is then matched to the solid body FEA displacement results to predict the structure’s strain energy. This process significantly reduces the computational costs of determining the optimal size of the unit cell since it eliminates FEA on the actual lattice structure. Furthermore, the method can provide the measurement of relative performances from different types of unit-cells. The developed examples clearly demonstrate how we can determine the optimal size of the unit-cell based on the strain energy. Moreover, the computational cost efficacy is also clearly demonstrated through comparison with the FEA and the proposed method.

Research on Producing Complex Metal Parts with Lattice Structure by Selective Laser Melting

2013 ◽  
Vol 371 ◽  
pp. 280-284 ◽  
Author(s):  
Voicu Mager ◽  
Nicolae Bâlc ◽  
Dan Leordean ◽  
Mircea Cristian Dudescu ◽  
Mathias Fockele
Keyword(s):  
Cell Size ◽  
Applied Load ◽  
Titanium Powder ◽  
Lattice Structure ◽  
Unit Cell ◽  
Lattice Structures ◽  
Bending Properties ◽  
Metal Parts ◽  
Unit Cell Size ◽  
A Cell

This study evaluates the manufacturability and performances of periodic cellular lattice structures designed by repeating a cubic unit cell and produced by SLM using titanium powder. The effects of unit cell size on the manufacturability, density, compression and bending properties of the manufactured cellular lattice structures were investigated. Lattice structures manufactured with various unit cell sizes ranging from 0.5 to 1.2 mm could be produced free of defects by the SLM process, with a novel type of supports. By the increasing of the cell size, a decrease of the applied load together with an enhancement of the flexure extension were observed. Specimens with a cell size higher than 1 mm manifested an excellent flexibility by flexure tests.

scholarly journals A Comparison of Miniature Lattice Structures Produced by Material Extrusion and Vat Photopolymerization Additive Manufacturing

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2163
Author(s):  
Rafael Guerra Silva ◽  
María Josefina Torres ◽  
Jorge Zahr Viñuela
Keyword(s):  
Additive Manufacturing ◽  
Energy Absorption ◽  
Lattice Structure ◽  
Solid Material ◽  
Unit Cell ◽  
Lattice Structures ◽  
Compression Tests ◽  
Material Extrusion ◽  
Lower Accuracy ◽  
Manufacturing Methods

In this paper, we study the capabilities of two additive manufacturing technologies for the production of lattice structures, namely material extrusion and vat photopolymerization additive manufacturing. A set of polymer lattice structures with diverse unit cell types were built using these additive manufacturing methods and tested under compression. Lattice structures built using material extrusion had lower accuracy and a lower relative density caused by the air gaps between layers, but had higher elastic moduli and larger energy absorption capacities, as a consequence of both the thicker struts and the relatively larger strength of the feedstock material. Additionally, the deformation process in lattices was analyzed using sequential photographs taken during the compression tests, evidencing larger differences according to the manufacturing process and unit-cell type. Both additive manufacturing methods produced miniature lattice structures with similar mechanical properties, but vat polymerization should be the preferred option when high geometrical accuracy is required. Nevertheless, as the solid material determines the compressive response of the lattice structure, the broader availability of feedstock materials gives an advantage to material extrusion in applications requiring stiffer structures or with higher energy absorption capabilities.

Compression behavior of three-dimensional printed polymer lattice structures

2018 ◽  
Vol 233 (8) ◽  
pp. 1574-1584 ◽  
Author(s):  
Mohammed Al Rifaie ◽  
Ahsan Mian ◽  
Raghavan Srinivasan
Keyword(s):  
Energy Absorption ◽  
Lattice Structure ◽  
Three Dimensional ◽  
Unit Cell ◽  
The Body ◽  
Basic Unit ◽  
Lattice Structures ◽  
Body Centered Cubic ◽  
Static Compression ◽  
Compression Behavior

This paper focuses on the compression behavior of additively manufactured or three-dimensional printed polymer lattice structures of different configurations. The body-centered cubic lattice unit cell, which has been extensively investigated for energy absorption applications, is the starting point for this research. In this study, the lattice structure based on the body-centered cubic unit cell was modified by adding vertical struts in different arrangements to create three additional configurations. Four lattice structure designs were selected for comparison: the basic unit cell (body centered cubic), body centered cubic with vertical struts added to all nodes in the lattice, body centered cubic with vertical struts added to alternate nodes in the lattice, and body centered cubic with gradient in the number of vertical bars in the lattice. Samples of all four designs were prepared using acrylonitrile–butadiene–styrene polymer by three-dimensional printing. The stiffness, failure loads, and energy absorption behaviors of all four configurations were determined under quasi-static compression loading. Specific properties were calculated by normalizing the test properties by the sample mass. It is observed from experimental data that selective placement of vertical support struts in the unit cell influences both the absolute and specific mechanical properties of lattice structures.

scholarly journals Fabrication and Compressive Behavior of a Micro-Lattice Composite by High Resolution DLP Stereolithography

Polymers ◽  
2021 ◽  
Vol 13 (5) ◽  
pp. 785
Author(s):  
Chow Shing Shin ◽  
Yu Chia Chang
Keyword(s):  
High Resolution ◽  
Lattice Structure ◽  
Low Cost ◽  
Hierarchical Structures ◽  
Dip Coating ◽  
Unit Cell ◽  
Digital Light Processing ◽  
Unit Cell Size ◽  
Wide Range ◽  
And Performance

Lattice structures are superior to stochastic foams in mechanical properties and are finding increasing applications. Their properties can be tailored in a wide range through adjusting the design and dimensions of the unit cell, changing the constituent materials as well as forming into hierarchical structures. In order to achieve more levels of hierarchy, the dimensions of the fundamental lattice have to be small enough. Although lattice size of several microns can be fabricated using the two-photon polymerization technique, sophisticated and costly equipment is required. To balance cost and performance, a low-cost high resolution micro-stereolithographic system has been developed in this work based on a commercial digital light processing (DLP) projector. Unit cell lengths as small as 100 μm have been successfully fabricated. Decreasing the unit cell size from 150 to 100 μm increased the compressive stiffness by 26%. Different pretreatments to facilitate the electroless plating of nickel on the lattice structure have been attempted. A pretreatment of dip coating in a graphene suspension is the most successful and increased the strength and stiffness by 5.3 and 3.6 times, respectively. Even a very light and incomplete nickel plating in the interior has increase the structural stiffness and strength by more than twofold.

scholarly journals Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

2021 ◽  
Vol 21 (3) ◽  
Author(s):  
S. Talebi ◽  
R. Hedayati ◽  
M. Sadighi
Keyword(s):  
Surface Area ◽  
Dynamic Behavior ◽  
Energy Absorption ◽  
Peak Stress ◽  
Absorption Capacity ◽  
Unit Cell ◽  
Lattice Structures ◽  
Energy Absorption Capacity ◽  
Closed Cell ◽  
Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

A Proof of Concept Study of the Mechanical Behavior of Lattice Structures Used to Design a Shoulder Hemi-Prosthesis

2021 ◽  
Author(s):  
Marinela Peto ◽  
Oscar Aguilar-Rosas ◽  
Erick Erick Ramirez-Cedillo ◽  
Moises Jimenez ◽  
Adriana Hernandez ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Mechanical Response ◽  
Mechanical Performance ◽  
Cell Attachment ◽  
Lattice Structure ◽  
Material Model ◽  
Patient Specific ◽  
Hexagonal Prism ◽  
Lattice Structures ◽  
Proof Of Concept

Abstract Lattice structures offer great benefits when employed in medical implants for cell attachment and growth (osseointegration), minimization of stress shielding phenomena, and weight reduction. This study is focused on a proof of concept for developing a generic shoulder hemi-prosthesis, from a patient-specific case of a 46 years old male with a tumor on the upper part of his humerus. A personalized biomodel was designed and a lattice structure was integrated in its middle portion, to lighten weight without affecting humerus’ mechanical response. To select the most appropriate lattice structure, three different configurations were initially tested: Tetrahedral Vertex Centroid (TVC), Hexagonal Prism Vertex Centroid (HPVC), and Cubic Diamond (CD). They were fabricated in resin by digital light processing and its mechanical behavior was studied via compression testing and finite element modeling (FEM). The selected structure according to the results was the HPVC, which was integrated in a digital twin of the biomodel to validate its mechanical performance through FEM but substituting the bone material model with a biocompatible titanium alloy (Ti6Al4V) suitable for prostheses fabrication. Results of the simulation showed acceptable levels of Von Mises stresses (325 MPa max.), below the elastic limit of the titanium alloys, and a better response (52 MPa max.) in a model with equivalent elastic properties, with stress performance in the same order of magnitude than the showed in bone’s material model.

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