Mechanical Response of Different Lattice Structures Fabricated Using the CLIP Technology

Author(s):  
Anil Saigal ◽  
John R. Tumbleston ◽  
Hendric Vogel

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.

Author(s):  
Anil Saigal ◽  
John R. Tumbleston ◽  
Hendric Vogel

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.


2017 ◽  
Vol 1142 ◽  
pp. 245-249 ◽  
Author(s):  
Anil Saigal ◽  
John Tumbleston

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


Author(s):  
Erica Liverani ◽  
Adrian H. A. Lutey ◽  
Alessandro Fortunato ◽  
Alessandro Ascari

Tensile and compression test specimens comprising lattice structures with simple cubic, crossing-rod and body-centered cubic (BCC) unit cells are produced via SLM additive manufacturing (AM) of AISI 316L stainless steel and CoCr powder. Equivalent stress-elongation curves are obtained, with equivalent strength, specific strength, stiffness modulus and specific stiffness calculated based on specimen density and sample cross-section. The obtained results highlight the fact that analogous structures can behave very differently depending on the chosen material. While large differences are obtained in strength and stiffness between the different unit cell types, specific strength and specific stiffness vary to a lesser extent. Two case studies are presented, including a porous structure suitable for bone implants in the field of biomedical engineering and an AISI 316L food packaging machine component. The results obtained in this study provide useful guidelines and equivalent properties for designers wishing to exploit the advantages of internal lattice structures in AM.


Author(s):  
Gian J. Calise ◽  
Anil Saigal

Mechanical metamaterials are man-made materials in which the mechanical properties are mainly defined by their structures instead of the properties of each component. Periodic cellular structures consisting of honeycomb, tetrahedral, 3D Kagome and pyramidal truss arrangement of webs or struts have recently attracted a lot of attention since they have a broad range of applications including structural components, energy absorption, heat exchangers, catalyst support, filters and biomaterials. In addition, lattice structures such as the octahedral are being investigated since they are 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 mechanical behavior and anisotropy in octahedral lattice structures of two different relative densities fabricated out of Acrylonitrile butadiene styrene (ABS) using Stratasys FDM 360mc and Dimension sst 1200es 3D printers. The machines were used to print octahedral lattice structured parts with struts 1.00 mm in diameter followed by parts with struts 2.6 mm in diameter and tested in compression in three mutually perpendicular directions. 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 not only is the stiffness and strength of the as fabricated parts anisotropic but they, in addition to failure, are also a function of the relative density/strut diameter of the structure.


Author(s):  
Gian J. Calise ◽  
Anil Saigal

This research concerns the production of mechanical metamaterials by a new means of additive manufacturing (AM). Mechanical metamaterials are man-made materials in which the mechanical properties are defined mainly by their structures rather than the properties of each material component. They are typically cellular lattice structures consisting of various arrangements of interconnected webs and struts. These metamaterials have a wide range of applications, but due to a recent breakthrough technology in the field of AM developed by Carbon, called Continuous Liquid Interface Production (CLIP), they can now be produced with ease at substantially higher speeds on a large scale. Using the CLIP process, Adidas is now utilizing these metamaterials in the midsoles of their new athletic shoes. More information about the mechanical response of parts produced by CLIP was needed to assess their relevance in this application. The goal of this research was to quantitatively determine the isotropy of octahedral and octet lattice structures produced from CLIP technology. Carbon claims that CLIP technology, unlike most other AM processes, produces parts that are isotropic. This means parts will have the same mechanical properties regardless of the direction of applied load. This claim has yet to be proven on lattice structures like the octahedral and octet structures. Those particular lattice structures are popular in the field of mechanical metamaterials because they are more structurally efficient than foams that are made of the same material with similar densities. The degree of isotropy of samples was measured by comparing values of various mechanical properties. These properties include Young’s modulus, a common measure of elasticity, and peak stress, a common measure of strength. Results indicated relatively isotropic behavior because mechanical properties varied based on the axis of compression by 6.5%, on average. The physical responses and failure mechanisms were also consistent.


Author(s):  
Jacopo Fiocchi ◽  
Chiara Bregoli ◽  
Giulio Gerosa ◽  
Ausonio Tuissi ◽  
Carlo Alberto Biffi

2021 ◽  
Vol 113 (11-12) ◽  
pp. 3599-3612
Author(s):  
Chen Zhang ◽  
Abhishek Banerjee ◽  
Alison Hoe ◽  
Achutha Tamraparni ◽  
Jonathan R. Felts ◽  
...  

2021 ◽  
Vol 1 ◽  
pp. 2841-2850
Author(s):  
Didunoluwa Obilanade ◽  
Christo Dordlofva ◽  
Peter Törlind

AbstractOne often-cited benefit of using metal additive manufacturing (AM) is the possibility to design and produce complex geometries that suit the required function and performance of end-use parts. In this context, laser powder bed fusion (LPBF) is one suitable AM process. Due to accessibility issues and cost-reduction potentials, such ‘complex’ LPBF parts should utilise net-shape manufacturing with minimal use of post-process machining. The inherent surface roughness of LPBF could, however, impede part performance, especially from a structural perspective and in particular regarding fatigue. Engineers must therefore understand the influence of surface roughness on part performance and how to consider it during design. This paper presents a systematic literature review of research related to LPBF surface roughness. In general, research focuses on the relationship between surface roughness and LPBF build parameters, material properties, or post-processing. Research on design support on how to consider surface roughness during design for AM is however scarce. Future research on such supports is therefore important given the effects of surface roughness highlighted in other research fields.


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