Design for Additive Manufacturing: Effectiveness of Unit Cell Design Guidelines As Ideation Tools

2019 ◽  
Author(s):  
I’Shea Boyd ◽  
Mohammad Fazelpour
Keyword(s):  
Additive Manufacturing ◽  
Effective Properties ◽  
Cellular Materials ◽  
Design Guidelines ◽  
Unit Cell ◽  
Cell Design ◽  
Recent Approach ◽  
Wide Range ◽  
Unit Cells ◽  
High Flexibility

Abstract The periodic cellular materials are comprised of repeatable unit cells. Due to outstanding effective properties of the periodic cellular materials such as high flexibility or high stiffness at low relative density, they have a wide range of applications in lightweight structures, crushing energy absorption, compliant structures, among others. Advancement in additive manufacturing has led to opportunities for making complex unit cells. A recent approach introduced four unit cell design guidelines and verified them through numerical simulation and user studies. The unit cell design guidelines aim to guide designers to re-design the shape or topology of a unit cell for a desired structural behavior. While the guidelines were identified as ideation tools, the effectiveness of the guidelines as ideation tools has not been fully investigated. To evaluate the effectiveness of the guidelines as ideation tools, four objective metrics have been considered: novelty, variety, quality, and quantity. The results of this study reveal that the unit cell design guidelines can be considered as ideation tools. The guidelines are effective in aiding engineers in creating novel unit cells with improved shear flexibility while maintaining the effective shear modulus.

A User Study on Exploring the Sequencing of Unit Cell Design Guidelines

2017 ◽  
Author(s):  
Mohammad Fazelpour ◽  
Apurva Patel ◽  
Prabhu Shankar ◽  
Joshua D. Summers
Keyword(s):  
User Study ◽  
Cellular Materials ◽  
Design Guidelines ◽  
Unit Cell ◽  
Structural Behavior ◽  
Cell Design ◽  
Unit Cells ◽  
Meso Scale

The objective of this user study is to evaluate the effect of sequencing of unit cell design guidelines. The unit cell design guidelines support engineers in intentionally redesigning the topology and shape of unit cells for a desired structural behavior. In this study, four different unit cell design guidelines are selected to enable designers in increasing the shear flexure in meso-scale periodic cellular materials. These guidelines are not necessarily objective and may result in different modified unit cells when applied by different designers. Therefore, this user study was designed to evaluate the effect of sequencing the guidelines on the subjectivity and the modified unit cells. Twelve different sequencing sets are tested and it is found that certain sequencing of guidelines resulted in more novel ideas than other cases with less subjective guidelines.

Design of Three-Dimensional, Triply Periodic Unit Cell Scaffold Structures for Additive Manufacturing

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Mazher Iqbal Mohammed ◽  
Ian Gibson
Keyword(s):  
Additive Manufacturing ◽  
Periodic Structures ◽  
Three Dimensional ◽  
Unit Cell ◽  
Final Size ◽  
Fused Filament Fabrication ◽  
Cell Structures ◽  
Triply Periodic ◽  
Unit Cells ◽  
Scaffold Structure

Highly organized, porous architectures leverage the true potential of additive manufacturing (AM) as they can simply not be manufactured by any other means. However, their mainstream usage is being hindered by the traditional methodologies of design which are heavily mathematically orientated and do not allow ease of controlling geometrical attributes. In this study, we aim to address these limitations through a more design-driven approach and demonstrate how complex mathematical surfaces, such as triply periodic structures, can be used to generate unit cells and be applied to design scaffold structures in both regular and irregular volumes in addition to hybrid formats. We examine the conversion of several triply periodic mathematical surfaces into unit cell structures and use these to design scaffolds, which are subsequently manufactured using fused filament fabrication (FFF) additive manufacturing. We present techniques to convert these functions from a two-dimensional surface to three-dimensional (3D) unit cell, fine tune the porosity and surface area, and examine the nuances behind conversion into a scaffold structure suitable for 3D printing. It was found that there are constraints in the final size of unit cell that can be suitably translated through a wider structure while still allowing for repeatable printing, which ultimately restricts the attainable porosities and smallest printed feature size. We found this limit to be approximately three times the stated precision of the 3D printer used this study. Ultimately, this work provides guidance to designers/engineers creating porous structures, and findings could be useful in applications such as tissue engineering and product light-weighting.

Design guidelines as ideation tools – a user study on exploring the subjectivity of unit-cell design guidelines

2018 ◽  
Vol 7 (1-2) ◽  
pp. 50-69 ◽  
Author(s):  
Mohammad Fazelpour ◽  
Apurva Patel ◽  
Prabhu Shankar ◽  
Joshua D. Summers
Keyword(s):  
User Study ◽  
Design Guidelines ◽  
Unit Cell ◽  
Cell Design

Developing Design Guidelines for Meso-Scaled Periodic Cellular Material Structures Under Shear Loading

2016 ◽  
Author(s):  
Mohammad Fazelpour ◽  
Prabhu Shankar ◽  
Joshua D. Summers
Keyword(s):  
Design Process ◽  
Effective Property ◽  
Design Guidelines ◽  
Shear Loading ◽  
Unit Cell ◽  
Cellular Material ◽  
Plane Shear ◽  
Unit Cells ◽  
Cell Topology ◽  
Shape Characteristics

Much research has been conducted on effective elastic properties of meso-scaled periodic cellular material (MPCM) structures; however, limited research is found in the literature for design guidelines to develop a unit cell (UC) topology and shape for multiple loading conditions. The current methods to design topology of unit cells has experienced limitations including numerical modeling challenges and trial-and-error associated with topology optimization and intuitive methods, respectively. To address this limitation this paper aims to develop guidelines for redesign of unit cell topology and shape under in-plane shear loading. The guidelines are intended to use design knowledge for helping engineers by providing recommendations at any stage of the design process. In this paper, the guidelines are developed by changing topology characteristics to achieve a desired effective property of a MPCM structure. The effect of individual members such as side connection and transverse connection of MPCM structure when subjected to in-plane shear loading are investigated through conducting a set of numerical simulation on UCs with similar topology and shape characteristics. Based on the simulation results, the unit cell design guidelines are developed to provide recommendations to engineers on improving shear flexure of MPCM during the design process.

Analytical Determination of Viscous Permeability of Fibrous Porous Media

2008 ◽  
Author(s):  
A. Tamayol ◽  
M. Bahrami
Keyword(s):  
Experimental Data ◽  
Aspect Ratio ◽  
Unit Cell ◽  
Analytical Determination ◽  
Fibrous Media ◽  
Wide Range ◽  
Unit Cells ◽  
The Media ◽  
Micro Structures

In this study, the permeability of ordered fibrous media towards normal and parallel flow is determined analytically. In this approach, porous material is represented by a “unit cell” which is assumed to be repeated throughout the media. Several fiber arrangements including: touching and non-touching arrays are considered. Modeling 1D touching fibers as a combination of Channel-like conduits, a compact relationship is proposed to predict permeability. Employing an integral technique and assuming a parabolic velocity profile within the unit cells, analytical relationships are developed for pressure drop for rectangular arrangements. The developed models are successfully compared with existing experimental data collected by others for square arrangement over a wide range of porosity. Due to the random nature of the porous micro structures, determination of exact permeability of real fibrous media is impossible. However, the analyses developed for ordered unit cells enable one to predict the trends observed in experimental data. Moreover, it is shown that the proposed normal flow permeability of square unit cell serves as a lower bound for the permeability of fibrous media. The effects of unit cell aspect ratio and fibers diameter on the permeability are also investigated. It is noted that with an increase in the aspect ratio the normal permeability decreases while, the parallel permeability remains constant. It is also shown that the permeability of fibrous media is related to the diameter of fibers squared.

A Unit Cell Design Guideline Development Method for Meso-Scaled Periodic Cellular Material Structures

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Mohammad Fazelpour ◽  
Prabhu Shankar ◽  
Joshua D. Summers
Keyword(s):  
Design Process ◽  
Guideline Development ◽  
Design Guidelines ◽  
Shear Loading ◽  
Unit Cell ◽  
Cellular Material ◽  
Cell Design ◽  
Plane Shear ◽  
Design Guideline ◽  
Development Method

Much research has been conducted on effective elastic properties of meso-scaled periodic cellular material (MPCM) structures; however, there is only limited research providing guidelines on how to develop improved unit cell (UC) topologies and shapes for a given set of loading requirements and conditions. This paper presents guidelines to improve the shear flexibility of the MPCMs while maintaining the effective shear modules by changing the topology or the shape of a unit cell. The guidelines are intended to use design knowledge for helping engineers by providing recommendations at any stage of the design process. In this paper, the guidelines are developed by changing topology characteristics to achieve a desired effective property of the MPCM structure. The effects of individual members, such as side connection, transverse connection, vertical legs, and curved beams of MPCM structure, when subjected to the in-plane shear loading are investigated through conducting a set of numerical simulation on UCs with similar topology and shape characteristics. Based on the simulation results, the unit cell design guidelines are developed to provide recommendations to engineers on improving the shear flexure of MPCM during the design process. Ultimately, a unit cell design guideline development method is offered and demonstrated by developing two new design guidelines.

scholarly journals A Multi-Scale Approach to Predict the Impact Resistance of Braided Composites using Progress Failure

2017 ◽  
Vol 26 (1) ◽  
pp. 096369351702600
Author(s):  
Xu Lei ◽  
Khazar Hayat ◽  
Sung Kyu Ha
Keyword(s):  
Effective Properties ◽  
Impact Resistance ◽  
Unit Cell ◽  
Braided Composites ◽  
Damage Models ◽  
Multi Scale ◽  
Constituent Material ◽  
Unit Cells ◽  
Plastic Resin ◽  
The Impact

A novel multi-scale approach based on micromechanics of failure together with the progressive damage models of the fibre and matrix constituents is presented to predict the impact resistance of braided composites. The meso- and micro-scale unit-cells of the braided composites with both thermosetting and thermos-plastic resin systems, were employed, and the effective properties of the braided tows, in the meso unit cell, were updated using the micro unit cell for which the degradation of constituent material properties were incorporated.

Effective properties of a periodic chiral arrangement of identical biaxially dielectric plates

1989 ◽  
Vol 4 (6) ◽  
pp. 1511-1514 ◽  
Author(s):  
A. Lakhtakia ◽  
V. K. Varadan ◽  
V. V. Varadan
Keyword(s):  
Electromagnetic Fields ◽  
Effective Properties ◽  
Unit Cell ◽  
Characteristic Matrix ◽  
Periodic Medium ◽  
Lyapunov Theorem ◽  
Anisotropic Plates ◽  
Left Handed ◽  
Unit Cells ◽  
Cell Thickness

A periodically inhomogeneous medium is constructed by stacking up unit cells made of (identical) structurally chiral slabs. Each structurally chiral slab is comprised of a certain number of identical biaxially anisotropic plates, the consecutive optic axes describing either a right- or a left-handed spiral. The characteristic matrix of the unit cell is obtained and used with the Floquet-Lyapunov theorem to obtain the electromagnetic fields in the periodic medium. When the unit cell thickness is very small compared to the principal wavelengths in the biaxial plates, the periodically inhomogeneous biaxial medium is shown to be equivalent to a homogeneous biaxial medium, the two optic axes of the equivalent medium being dependent on the handedness of the periodic medium.

scholarly journals Influence of unit cell parameters of tetrachiral mechanical metamaterial on its effective properties

2021 ◽  
Vol 8 (1) ◽  
pp. 150-157
Author(s):  
Linar R. Akhmetshin ◽  
◽  
Igor Yu. Smolin ◽  
◽  
◽  
...  
Keyword(s):  
Rotation Angle ◽  
Effective Properties ◽  
Three Dimensional ◽  
Unit Cell ◽  
The Finite Element Method ◽  
Unit Cell Parameters ◽  
Cell Parameters ◽  
Chiral Structures ◽  
Unit Cells ◽  
Loading Axis

In the paper, we study the mechanical behavior of a three-dimensional chiral mechanical metamaterial using numerical modeling. A feature of chiral structures is that during their uniaxial loading a twisting is observed along the loading axis. A rod of the mechanical metamaterial composed of 3 × 3 × 9 unit cells along the corresponding three orthogonal axes. The relative strain of uniaxial compression of the sample in the simulation did not exceed 3.3%. The simulation was performed by the finite element method in a threedimensional case. Original results on the dependencies of the rotation angle and the reaction of the rigidly fixed support of the metamaterial sample on the parameters characterizing the structure of the unit cell of the metamaterial are presented in this context. All the dependencies, except one, are nonlinear with portions of large and small changes.

DfAM of Nonlinear Cellular Flexible Structures

2019 ◽  
Author(s):  
Jelena Djokikj ◽  
Jovana Jovanova
Keyword(s):  
Additive Manufacturing ◽  
Geometrical Nonlinearity ◽  
Flexible Structures ◽  
Multiple Scale ◽  
Systematic Design ◽  
Unit Cells ◽  
Traditional Manufacturing ◽  
High Flexibility ◽  
High Level ◽  
3D Shapes

Abstract Nonlinear cellular structures are defined as structures with multiple scale unit cells patterned through the volume of the structure. The geometrical nonlinearity allows local high flexibility in the movement and also in the sense of strength of materials. The focus of this paper is to create a framework for design for additive manufacturing (DfAM) of a modular nonlinear cellular structure with high level of flexibility. The flexibility will be exploited in skin-like structures adaptable to freeform geometries or utilize flat printed designs for voluminous and structural 3D shapes. For the modeling of the structure CAD software is used and for the fabrication of the structure additive manufacturing (AM) is applied. These technologies work by adding the material in layers, which enables fabrication of parts with complex geometries. The working principal of AM which is opposite to the traditional manufacturing requires for changes in the design process. These changes are applied in the DfAM that we are presenting with this study. The DfAM is used to develop a systematic design approach to support the fabrication of unique structure shapes by AM.

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