Anisotropy and Failure in Octahedral Lattice Structure Parts Fabricated Using the FDM Technology

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral, octet, vertex centroid, dode, diamond, rhombi octahedron, rhombic dodecahedron and solid lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, plastic strain hardening to a peak in strength, followed by a drop in flow stress to a plateau region and finally rapid hardening associated with contact of the deformed struts with each other as part of densification. It was found that the elastic modulus and strength of the various lattice structured materials are proportional to each other. In addition, it was found that the octahedral, octet and diamond lattice structures are amongst the most efficient based on the measured specific stiffness and specific strength.

Download Full-text

Stress-Strain Behavior of an Octahedral and Octet-Truss Lattice Structure Fabricated Using the CLIP Technology

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1142.245 ◽

2017 ◽

Vol 1142 ◽

pp. 245-249 ◽

Cited By ~ 1

Author(s):

Anil Saigal ◽

John Tumbleston

Keyword(s):

Additive Manufacturing ◽

3D Printing ◽

Lattice Structure ◽

Liquid Interface ◽

Layer By Layer ◽

Stress Strain ◽

Strain Behavior ◽

Octet Truss ◽

Continuous Liquid Interface Production ◽

Similar Density

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the stress-strain behavior of an octahedral-and octet-truss lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. Continuous Liquid Interface Production (CLIP) is a breakthrough technology that grows parts instead of printing them layer by layer. Lattice structures such as the octahedral-and octet-truss lattice have recently attracted a lot of attention since they are often structurally more efficient than foams of a similar density made from the same material, and the ease with which these structures can now be produced using 3D printing and additive manufacturing. This research investigates the stress-strain behavior under compression of an octahedral-and octet-truss lattice structured polyacrylate fabricated using CLIP technology

Download Full-text

Mechanical Behavior of As-Fabricated and UV-Cured Lattice Structures Printed Using the CLIP Technology

Volume 2: Advanced Manufacturing ◽

10.1115/imece2017-70886 ◽

2017 ◽

Author(s):

Anil Saigal ◽

John R. Tumbleston ◽

Hendric Vogel

Keyword(s):

Additive Manufacturing ◽

Mechanical Behavior ◽

Relative Density ◽

Uv Curing ◽

Elastic Response ◽

Lattice Structures ◽

Minimum Diameter ◽

Strain Behavior ◽

End Use ◽

Continuous Liquid Interface Production

In the rapidly growing field of additive manufacturing (AM), the focus in recent years has shifted from prototyping to manufacturing fully functional, ultralight, ultrastiff end-use parts. This research investigates the mechanical behavior of octahedral and octet lattice structured polyacrylate fabricated using Continuous Liquid Interface Production (CLIP) technology based on 3D printing and additive manufacturing processes. Five different octahedral structures and seven different octet structures with relative densities ranging from approximately 0.07 to 0.35 were fabricated by changing the strut diameter. The minimum diameter of the strut elements is 0.50 mm and 0.35 mm for the octahedral and octet structures, respectively. The different relative density structures were tested in compression in the as-fabricated state and after they were UV cured. The compressive stress-strain behavior of the lattice structures observed is typical of cellular structures which include a region of nominally elastic response, yielding, and plastic strain hardening to a peak in strength, followed by a drop in flow stress. It was found that the stiffness and strength of octahedral lattice structures is greater than the stiffness and strength of octet lattice structures at all relative densities for both as printed/fabricated and UV cured parts, and the ratio of stiffness and strength of UV cured parts to as fabricated parts decreases as the relative density increases. However, the ratio of stiffness and strength of UV cured parts to as fabricated parts for octet lattice structures in general is greater than that for octahedral structures. This can be attributed to the relative diameter of the struts and the depth of UV curing.

Download Full-text

Elastic Response of Anisotropic Gyroid Cellular Structures under Compression: Parametric Analysis

Materials & Design ◽

10.1016/j.matdes.2021.109706 ◽

2021 ◽

pp. 109706

Author(s):

Xing Peng ◽

Qiyuan Huang ◽

Yali Zhang ◽

Xiaogang Zhang ◽

Tongtong Shen ◽

...

Keyword(s):

Parametric Analysis ◽

Elastic Response ◽

Cellular Structures

Download Full-text

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

Volume 1A: 36th Computers and Information in Engineering Conference ◽

10.1115/detc2016-60012 ◽

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.

Download Full-text

An experimental investigation on mechanical performances of 3D printed lightweight ABS pipes with different cellular wall thickness

JOURNAL OF MECHANICAL ENGINEERING AND SCIENCES ◽

10.15282/jmes.15.2.2021.16.0641 ◽

2021 ◽

Vol 15 (2) ◽

pp. 8169-8177

Author(s):

Berkay Ergene ◽

İsmet ŞEKEROĞLU ◽

Çağın Bolat ◽

Bekir Yalçın

Keyword(s):

Compressive Strength ◽

Energy Absorption ◽

Wall Thickness ◽

Lattice Structure ◽

Honeycomb Structure ◽

Cellular Structures ◽

Compression Tests ◽

Absorbed Energy ◽

Great Opportunity ◽

3D Printed

In recent years, cellular structures have attracted great deal of attention of many researchers due to their unique properties like exhibiting high strength at low density and great energy absorption. Also, the applications of cellular structures (or lattice structures) such as wing airfoil, tire, fiber and implant, are mainly used in aerospace, automotive, textile and biomedical industries respectively. In this investigation, the idea of using cellular structures in pipes made of acrylonitrile butadiene styrene (ABS) material was focused on and four different pipe types were designed as honeycomb structure model, straight rib pattern model, hybrid version of the first two models and fully solid model. Subsequently, these models were 3D printed by using FDM method and these lightweight pipes were subjected to compression tests in order to obtain stress-strain curves of these structures. Mechanical properties of lightweight pipes like elasticity modulus, specific modulus, compressive strength, specific compressive strength, absorbed energy and specific absorbed energy were calculated and compared to each other. Moreover, deformation modes were recorded during all compression tests and reported as well. The results showed that pipe models including lattice wall thickness could be preferred for the applications which don’t require too high compressive strength and their specific energy absorption values were notably capable to compete with fully solid pipe structures. In particular, rib shape lattice structure had the highest elongation while the fully solid one possessed worst ductility. Lastly, it is pointed out that 3D printing method provides a great opportunity to have a foresight about production of uncommon parts by prototyping.

Download Full-text

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

Journal of Engineering and Science in Medical Diagnostics and Therapy ◽

10.1115/1.4051419 ◽

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.

Download Full-text

Dynamic Loading of Lattice Structure Made by Selective Laser Melting-Numerical Model with Substitution of Geometrical Imperfections

Materials ◽

10.3390/ma11112129 ◽

2018 ◽

Vol 11 (11) ◽

pp. 2129 ◽

Cited By ~ 7

Author(s):

Radek Vrána ◽

Ondřej Červinek ◽

Pavel Maňas ◽

Daniel Koutný ◽

David Paloušek

Keyword(s):

Mechanical Properties ◽

Numerical Model ◽

Cross Section ◽

Lattice Structure ◽

Low Velocity Impact ◽

Lattice Structures ◽

Laser Melting ◽

Low Velocity ◽

Velocity Impact ◽

Geometrical Imperfections

Selective laser melting (SLM) is an additive technology that allows for the production of precisely designed complex structures for energy absorbing applications from a wide range of metallic materials. Geometrical imperfections of the SLM fabricated lattice structures, which form one of the many thin struts, can lead to a great difference in prediction of their behavior. This article deals with the prediction of lattice structure mechanical properties under dynamic loading using finite element method (FEA) with inclusion of geometrical imperfections of the SLM process. Such properties are necessary to know especially for the application of SLM fabricated lattice structures in automotive or aerospace industries. Four types of specimens from AlSi10Mg alloy powder material were manufactured using SLM for quasi-static mechanical testing and determination of lattice structure mechanical properties for the FEA material model, for optical measurement of geometrical accuracy, and for low-velocity impact testing using the impact tester with a flat indenter. Geometries of struts with elliptical and circular cross-sections were identified and tested using FEA. The results showed that, in the case of elliptical cross-section, a significantly better match was found (2% error in the Fmax) with the low-velocity impact experiments during the whole deformation process compared to the circular cross-section. The FEA numerical model will be used for future testing of geometry changes and its effect on mechanical properties.

Download Full-text

Topology, Shape, and Size Optimization of Additively Manufactured Lattice Structures Based on the Superformula

Volume 2A: 44th Design Automation Conference ◽

10.1115/detc2018-86191 ◽

2018 ◽

Cited By ~ 2

Author(s):

Andrea Nessi ◽

Tino Stanković

Keyword(s):

Lattice Structure ◽

Lightweight Design ◽

Mathematical Formulation ◽

Lattice Structures ◽

Structural Synthesis ◽

Normal Surface ◽

Technical Problems ◽

Wide Range ◽

Tetrahedral Meshing

This paper investigates the application of Superformula for structural synthesis. The focus is set on the lightweight design of parts that can be realized using discrete lattice structures. While the design domain will be obtained using the Superformula, a tetrahedral meshing technique will be applied to this domain to generate the topology of the lattice structure. The motivation for this investigation stems from the property of the Superformula to easily represent complex biological shapes, which opens a possibility to directly link a structural synthesis to a biomimetic design. Currently, numerous results are being reported showing the development of a wide range of design methods and tools that first study and then utilize the solutions and principles from the nature to solve technical problems. However, none of these methods and tools quantitatively utilizes these principles in the form of nature inspired shapes that can be controlled parametrically. The motivation for this work is also in part due to the mathematical formulation of the Superformula as a generalization of a superellipse, which, in contrast to the normal surface modeling offers a very compact and easy way to handle set of rich shape variants with promising applications in structural synthesis. The structural synthesis approach is organized as a volume minimization using Simulated Annealing (SA) to search over the topology and shape of the lattice structure. The fitness of each of candidate solutions generated by SA is determined based on the outcome of lattice member sizing for which an Interior Point based method is applied. The approach is validated with a case study involving inline skate wheel spokes.

Download Full-text

Design of Shape Reconfigurable, Highly Stretchable Honeycomb Lattice With Tunable Poisson’s Ratio

Frontiers in Materials ◽

10.3389/fmats.2021.660325 ◽

2021 ◽

Vol 8 ◽

Author(s):

Le Dong ◽

Chengru Jiang ◽

Jinqiang Wang ◽

Dong Wang

Keyword(s):

Theoretical Model ◽

Ambient Temperature ◽

Shape Memory ◽

Poisson’S Ratio ◽

Lattice Structure ◽

Poisson's Ratio ◽

Lattice Structures ◽

Straight Beam ◽

Highly Stretchable ◽

3D Printed

The mechanical behaviors of lattice structures can be tuned by arranging or adjusting their geometric parameters. Once fabricated, the lattice’s mechanical behavior is generally fixed and cannot adapt to environmental change. In this paper, we developed a shape reconfigurable, highly stretchable lattice structure with tunable Poisson’s ratio. The lattice is built based on a hexagonal honeycomb structure. By replacing the straight beam with curled microstructure, the stretchability of the lattice is significantly improved. The Poisson’s ratio is adjusted using a geometric angle. The lattice is 3D printed using a shape memory polymer. Using its shape memory effect, the lattice demonstrates tunable shape reconfigurability as the ambient temperature changes. To capture its high stretchability, tunable Poisson’s ratio and shape reconfigurability, a phase evolution model for lattice structure is used. In the theoretical model, the effects of temperature on the material’s nonlinearity and geometric nonlinearity due to the lattice structure are assumed to be decoupled. The theoretical shape change agrees well with the Finite element results, while the theoretical model significantly reduces the computational cost. Numerical results show that the geometrical parameters and the ambient temperature can be manipulated to transform the lattice into target shapes with varying Poisson’s ratios. This work provides a design method for the 3D printed lattice structures and has potential applications in flexible electronics, soft robotics, and biomedicine.

Download Full-text