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The primary goal is to design parts with lattice mesostructure and demonstrate that they have better structural and/or compliance performance, per weight, than parts with bulk material, foams, or other mesostructured approaches. Mesostructure refers to features within a part that have sizes between micro and macro-scales, for example, small truss s...
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... the past 10 years, the area of lattice materials has received considerable attention due to their inherent advantages over foams in providing light, stiff, and strong materials ( Ashby et al., 2000). Lattice structures tend to have geometry variations in three dimensions; some of our designs are shown in Figure 1. As Deshpande, Fleck, and Ashby (2001) point out, the strength of foams scales as ρ 1.5 , whereas lattice structure strength scales as ρ, where ρ is the volumetric density of the material. ...
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... lattice structure strength scales as ρ, where ρ is the volumetric density of the material. As a result, lattices with a ρ = 0.1 are about 3 times stronger than a typical foam. The strength differences lie in the nature of material deformation: the foam is governed by cell wall bending, while lattice elements stretch and compress. The examples in Fig. 1 utilize the octet-truss (shown on the left), but many other lattice structures have been developed and studied (e.g., kagome, Kelvin foam). We have developed methods for designing lattice mesostructure for parts (Wang & Rosen, 2003) and have developed design-for- manufacturing rules for their fabrication in Stereolithography (SL). The ...
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... of continuum mechanics have been applied to various mesostructured materials. Ashby and co-workers wrote a book on metal foam design and analysis ( Ashby et al., 2000). They and others have applied similar methods to the analysis of lattice structures. The octet truss in Fig. 1 has been extensively analyzed. Deshpande et al. (2001) treated the octet truss unit cell as a collection of tension-compression bars that are pin-jointed at vertices and derived analytical models of their collapse behavior for many combinations of stresses. Wang and McDowell (2005) extended this study to include several other lattice ...
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... effects. We also capture non-linearities arising from large deflections (geometric non-linearity) and material property behaviors (material non-linearity), as well as buckling failures. Each node in the 3D unit lattice has six degrees of freedom, so the stiffness matrix for a unit lattice with N struts will be 6N + 6. The octet-truss unit cell ( Fig. 1) will have 300 degrees of ...
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... comparison between the relative stiffness of unit cells comprised of different size arrays of octets is enlightening. The relative stiffness of the unit cells decreases as the number of octet- truss structures increases. Specifically, a unit cell containing 27 (3x3x3) octet-truss structures (Fig. 10) has a lower relative stiffness at a fixed relative density compared to the single unit cell (and a 2x2x2 octet-truss structures, although not reported here). The dominant reason for this effect is caused by fixing the relative density of the unit cell, as this implies that strut diameters must decrease in size, which results in a more ...
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... designed a component for a replacement hip joint that takes advantage of lattice structure to fulfill its two primary functions. A typical hip joint is shown in Fig. 10 (Medical, 2005). The acetabular component serves as the socket half of the ball-and-socket hip joint. Conventional acetabular components have a polyethylene liner to absorb impacts. In our design, impact absorption will be accommodated by designing a lattice structure implant that matches the stiffness of bone along the implant's outer region. During ...
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Citations
... The current market demand places an ever-increasing emphasis on the efficient use of 3D printing for the production of complicated shapes [41][42][43]. However, the use of lattice structures in additive manufacturing has seen increasing demand due to their unique applications [44][45][46][47][48][49][50][51]. Lattice structures could be classified as porous and non-porous materials, depending on their applications [52][53][54][55][56][57][58][59][60]. ...
Over the past 15 years, interest in additive manufacturing (AM) on lattice structures has significantly increased in producing 3D/4D objects. The purpose of this study is to gain a thorough grasp of the research pattern and the condition of the field’s research today as well as identify obstacles towards future research. To accomplish the purpose, this work undertakes a scientometric analysis of the international research conducted on additive manufacturing for lattice structure materials published from 2002 to 2022. A total of 1290 journal articles from the Web of Science (WoS) database and 1766 journal articles from the Scopus database were found using a search system. This paper applied scientometric science, which is based on bibliometric analysis. The data were subjected to a scientometric study, which looked at the number of publications, authorship, regions by countries, keyword co-occurrence, literature coupling, and scientometric mapping. VOSviewer was used to establish research patterns, visualize maps, and identify transcendental issues. Thus, the quantitative determination of the primary research framework, papers, and themes of this research field was possible. In order to shed light on current developments in additive manufacturing for lattice structures, an extensive systematic study is provided. The scientometric analysis revealed a strong bias towards researching AM on lattice structures but little concentration on technologies that emerge from it. It also outlined its unmet research needs, which can benefit both the industry and academia. This review makes a prediction for the future, with contributions by educating researchers, manufacturers, and other experts on the current state of AM for lattice structures.
... Materials with repeating unit cell (RUC) as a relatively new class of cellular materials have been received much attention due to the simplicity of design and their multifunctional applications. Truss structures [7,8], minimal surface-based unit cells [9,10], and topologically optimized unit cells [11,12] are commonly used to design cellular materials. Triply periodic minimal surfaces (TPMS) are a nonintersecting 3D surface characterized by a zero value of mean curvature at each point. ...
... Sensitivity analysis of the compliance tensor components with respect to the total number of voxels in the RVE. Then, the coordinate of the center of each voxel (which should be used in Eqs.(1)(2)(3)(4)(5)(6)(7) as (x; y; z)) can be presented as (a x i ...
Unlike random cellular materials, in TPMS structures the ligament size and orientation distribution are constant, leading to a directional dependency of the mechanical properties. In this work, the directional dependency of elastic properties of seven TPMS-based structures has been studied in a wide range of the solid phase volume fractions (i.e., 10–90%). Our study indicates that the strong and weak directions in IWP, Gyroid, FRD, FKS, and Diamond are diagonal and axial, respectively. In contrast, Schwarz-P and Neovius structure show a reversed order. Then, the idea of designing hybrid structures consisting from Schwarz-P/Neovius and each of the other five structures in laminated or matrix-spherical inclusion form has been employed to obtain structures with a more uniform directional elastic modulus. First, the mathematical functions of the hybrid structures are presented. The functions are carefully parameterized to ensure a smooth transition between two structures. Then the effect of the combination ratio of the parent structures on the universal anisotropy index of the hybrid structures is investigated. Our study indicates that hybrid structures have more uniform directional elastic modulus compared to their parent structures, and an appropriate selection of the combination ratio of the parent structures can lead to the least universal anisotropy.
... The previously developed out-of-core modeling algorithms (e.g. [5,6]) for lattice structures could handle uniform or periodical lattice structures but becomes difficult for processing large-scale adaptive lattice structures. There is also prior research [7] seeking to reduce the number of facets in triangulating a lattice structure. ...
Lattice structures have been widely used in various applications of additive manufacturing due to its superior physical properties. If modeled by triangular meshes, a lattice structure with huge number of struts would consume massive memory. This hinders the use of lattice structures in large-scale applications (e.g., to design the interior structure of a solid with spatially graded material properties). To solve this issue, we propose a memory-efficient method for the modeling and slicing of adaptive lattice structures. A lattice structure is represented by a weighted graph where the edge weights store the struts' radii. When slicing the structure, its solid model is locally evaluated through convolution surfaces and in a streaming manner. As such, only limited memory is needed to generate the toolpaths of fabrication. Also, the use of convolution surfaces leads to natural blending at intersections of struts, which can avoid the stress concentration at these regions. We also present a computational framework for optimizing supporting structures and adapting lattice structures with prescribed density distributions. The presented methods have been validated by a series of case studies with large number (up to 100M) of struts to demonstrate its applicability to large-scale lattice structures.
... Lattice structures can be described as a periodic array of cells making up of struts connecting between two nodes which are rigidly bonded [8,9]. Lattice structures are ultralightweight metamaterials with high specific strength, high specific rigidity, high durability, high energy absorption rate, and thermal protection [8,10], therefore fulfill multifunctional requirements for most engineering and biomedical applications. ...
... The nodes (unit cells- Figure 1) are the basic unit building blocks of the lattice structures. Rhombic and diagonal nodes were selected for the study partly because they can be easily manufactured by most AM technology including LPBF [15] and as lattice structures, they could create rough surfaces, to stimulate bone ingrowth (osseointegration), to mimic bone properties in order to avoid the stress-shielding effect [12], excellent performance and multifunctionality while reducing weight for engineering applications [9,10]. The lattice structures were generated by repeating the unit cells in three dimensions along the x, y, and z-axis. ...
... Lattice structures are known to mimic the anisotropic porous nature of bone and the possibility of tuning their elastic modulus over a wide range by varying the lattice properties [35]. The creating of open space within the lattices would also translate to minimal material usage [10] and the discrete pore volumes in microns' dimensions would equally produce a perfect surface for bone-implant interlocking with suitable biomechanical properties [36]. The quest for the intense research into the mechanical properties of lattice structures for biomedical applications is driven by their ability to prevent stress shielding effect [12,[37][38][39]. ...
The study focused on producing lattice structures using rhombic and diagonal nodes and indicating their logical biomedical and engineering applications. Laser powder bed fusion manufacturing technology a subset of additive manufacturing was used to manufacture the lattice structures with different struts geometry. Average elastic modulus value of 5.3±0.2 GPa was obtained for the rhombic lattice structures and 5.1±0.1 GPa for the diagonal lattice structures. Generally, the mechanical properties of the lattice structures produced could be logically considered suitable for biomedical and engineering applications. The mechanical properties of the lattice structures could be fine-tuned for a specific engineering or biomedical applications by varying the lattice properties of the lattice structures.
... Lattice structures can be described as a periodic array of cells making up of struts connecting between two nodes which are rigidly bonded [8,9]. Lattice structures are ultralightweight metamaterials with high specific strength, high specific rigidity, high durability, high energy absorption rate, and thermal protection [8,10], therefore fulfill multifunctional requirements for most engineering and biomedical applications. ...
... The nodes (unit cells- Figure 1) are the basic unit building blocks of the lattice structures. Rhombic and diagonal nodes were selected for the study partly because they can be easily manufactured by most AM technology including LPBF [15] and as lattice structures, they could create rough surfaces, to stimulate bone ingrowth (osseointegration), to mimic bone properties in order to avoid the stress-shielding effect [12], excellent performance and multifunctionality while reducing weight for engineering applications [9,10]. The lattice structures were generated by repeating the unit cells in three dimensions along the x, y, and z-axis. ...
... Lattice structures are known to mimic the anisotropic porous nature of bone and the possibility of tuning their elastic modulus over a wide range by varying the lattice properties [35]. The creating of open space within the lattices would also translate to minimal material usage [10] and the discrete pore volumes in microns' dimensions would equally produce a perfect surface for bone-implant interlocking with suitable biomechanical properties [36]. The quest for the intense research into the mechanical properties of lattice structures for biomedical applications is driven by their ability to prevent stress shielding effect [12,[37][38][39]. ...
The study focused on producing lattice structures using rhombic and diagonal nodes and indicating their logical biomedical and engineering applications. Laser powder bed fusion manufacturing technology a subset of additive manufacturing was used to manufacture the lattice structures with different struts geometry. Average elastic modulus value of 5.30.2 GPa was obtained for the rhombic lattice structures and 5.10.1 GPa for the diagonal lattice structures. Generally, the mechanical properties of the lattice structures produced could be logically considered suitable for biomedical and engineering applications. The mechanical properties of the lattice structures could be fine-tuned for a specific engineering or biomedical applications by varying the lattice properties of the lattice structures.
... properties that surpass their constitutive material properties. They have a wide range of applications in structural design including light structures with high strength [2,3], impact and crushing energy absorption [4][5][6], sound absorption and acoustic performance [7][8][9], compliant structures and mechanisms [10][11][12], high shear flexure and large shear strain applications [13][14][15], and development of non-pneumatic structures [16][17][18]. ...
This paper presents recent advances in developing a systematic design procedure for nonlinear cellular meta-materials. In previous work by the authors, the Unit Cell Synthesis method was introduced for designing unit-cell-based meta-materials that exhibit targeted nonlinear deformation response. The method is based on a fundamental understanding of simple entities that exhibit geometric nonlinearities under deformation. The geometric parameters associated with these entities can be tuned to achieve the desired nonlinear response. In this work, the original Unit Cell Synthesis method is extended to include a multi-objective optimization step to take into consideration multiple application-specific criteria while optimizing the meta-material design. A case study of designing a meta-material to mimic the nonlinear compressive behavior of an existing elastomer component in a military tracked vehicle is presented to demonstrate the method. Furthermore, to understand the effects of the manufacturing accuracy of design parameters on the performance of the optimized meta-material, a sensitivity analysis is carried out to obtain a feasible range of mechanical behavior for the meta-material and reveal the significance of individual design parameters and their interactions.
... The biggest disadvantage of stochastic cellular materials is the lack of design freedom. Therefore, ordered structures, especially lattice structures, are of higher interest [2]. Lattices have a trusslike structure with interconnected struts and nodes in a threedimensional space [3]. ...
... The differences in performance come from a different deformation behaviour. Foams are goverend by cell wall bending, whereas lattice cells stretch and compress [2]. This stretch dominated behaviour means that the initial yield is followed by either plastic buckling or brittle collapse which leads to post yield softening and then at the densification strain the stress rises steeply [4]. ...
Lattice structures are currently of high interest, especially for lightweight design. They generally have better structural performance per weight than parts made of bulk material. With conventional manufacturing techniques they are difficult to produce, but with additive manufacturing (AM) fabricationisfeasible. To better understand their behaviour under various loading conditions two lattice structures in different configurations were observed. For each structure three different test specimens were designed and manufactured using selective laser sintering (SLS). To investigate the mechanical performance under large deformations the specimens were made of a thermoplastic polyurethane(TPU), which shows a hyperelastic material behaviour. Beside the experimental observations also finite element analyses (FEA) were conducted to investigate the deformation behaviour in more detail.
... However, the hollowed cells in their method are closed, and they are not suitable for some common 3D printing technologies (such as SLS and DLP). There were also some similar ways that used lightweight structures to improve the strength of models in earlier years [9,10]. Wang et al. [3] proposed a frame structure to reduce the material in 3D printing by formulating the problem as a multi-objective optimization. ...
Lightweight modeling is one of the most important research subjects in modern fabrication manufacturing, and it provides not only a low-cost solution but also functional applications, especially for the fabrication using 3D printing. This approach presents a multi-scale porous structure-based lightweight framework to reduce the weight of 3D printed objects while meeting the specified requirements. Specifically, the triply periodic minimal surface (TPMS) is exploited to design a multi-scale porous structure, which can achieve high mechanical behaviors with lightweight. The multi-scale porous structure is constructed using compactly supported radial basis functions, and it inherits the good properties of TPMS, such as smoothness, full connectivity (no closed hollows) and quasi-self-supporting (free of extra supports in most cases). Then, the lightweight problem utilizing the porous structures is formulated into a constrained optimization. Finally, a strength-to-weight optimization method is proposed to obtain the lightweight models. It is also worth noting that the proposed porous structures can be perfectly fabricated by common 3D printing technologies on account of the leftover material, such as the liquid in SLA, which can be removed through the fully connected void channel.
... Using lightweight cellular structures for decreasing the support materials has been studied in the field of AM [2], [6], [9]. Hussein et al. [4] explored the potential of using cellular structures for the support of metallic parts based on SLM while distortion of the part occurred. ...
... The more symmetrical patterns of linear (FFF1), hexagonal (FFF6) and 407 diamond (FFF7) provided greater resistance to the compression forces. The irregular inner 408 geometry of the moroccanstar (FFF5) could explain its poorer mechanical performance since 409 more regular lattice-type structures have a greater load-bearing capacity (Rosen et al., 2006). 410 Tablet hardness of the three different manufacturing processes can be found in Figure 8. ...
Oral tablets are a convenient form to deliver active pharmaceutical ingredients (API) and have a high level of acceptance from clinicians and patients. There is a wide range of excipients available for the fabrication of tablets thereby offering a versatile platform for the delivery of therapeutic agents to the gastrointestinal tract. However, the geometry of tablets is limited by conventional manufacturing processes. This study aimed to compare three manufacturing processes in the production of flat-faced oral tablets using the same formulation composed of a polymer blend and caffeine as a model drug: fused-filament fabrication (FFF), direct compression (DC) and injection molding (IM). Hot-melt extrusion was used to convert a powder blend into feedstock material for FFF and IM processes, while DC was performed on the powder mixture. Tablets were produced with the same dimensions and were characterised for their physical and dissolution properties. There were statistical differences in the physical properties and drug release profiles of the tablets produced by the different manufacturing processes. DC tablets displayed immediate release, IM provided sustained release over 48 hours, and FFF tablets displayed both release types depending on the printing parameters. FFF continues to demonstrate high potential as a manufacturing process for the efficient production of personalized oral tablets.
