Mechanical performance of additively manufactured uniform and graded porous structures based on topology-optimized unit cells

2020 ◽  
pp. 095440622094711
Author(s):  
Mohsen Teimouri ◽  
Masoud Asgari
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Mechanical Performance ◽  
Functionally Graded ◽  
Geometrical Parameters ◽  
Lattice Structures ◽  
Shell Type ◽  
Two Samples ◽  
Unit Cells ◽  
Thin Walled

A topology optimization (TO) method is used to develop new and efficient unit cells to be used in additively manufactured porous lattice structures. Two types of unit cells including solid and thin-walled shell-type ones are introduced for generating the desired regular and functionally graded (FG) lattice structures. To evaluate structural stiffness and crushing behavior of the proposed lattice structures, their mechanical properties, and energy absorption parameters have been calculated through implementing finite element (FE) simulations on them. To validate the simulations, two samples were fabricated by a stereolithography (SLA) machine. Besides, the effects of geometrical parameters and optimizing scheme of the unit cells on the mechanical properties of the proposed structures are studied. Consequently, energy absorption parameters have been calculated and compared for both the solid and thin-walled lattice structures to evaluate their ability in energy absorption. It was found in general that for the solid lattice structures, the mechanical properties, and the crushing parameters are directly affected by porosity though in shell-type ones superior mechanical properties could be achieved even for a smaller proportion of material usage.

Architected functionally graded porous lattice structures for optimized elastic-plastic behavior

2020 ◽  
Vol 234 (8) ◽  
pp. 1099-1116 ◽  
Author(s):  
Mahshid Mahbod ◽  
Masoud Asgari ◽  
Christian Mittelstedt
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Specific Energy ◽  
Elastic Moduli ◽  
Maximum Stress ◽  
Functionally Graded ◽  
Plastic Behavior ◽  
Lattice Structures ◽  
Porous Structures ◽  
Specific Energy Absorption

In this paper, the elastic–plastic mechanical properties of regular and functionally graded additively manufactured porous structures made by a double pyramid dodecahedron unit cell are investigated. The elastic moduli and also energy absorption are evaluated via finite element analysis. Experimental compression tests are performed which demonstrated the accuracy of numerical simulations. Next, single and multi-objective optimizations are performed in order to propose optimized structural designs. Surrogated models are developed for both elastic and plastic mechanical properties. The results show that elastic moduli and the plastic behavior of the lattice structures are considerably affected by the cell geometry and relative density of layers. Consequently, the optimization leads to a significantly better performance of both regular and functionally graded porous structures. The optimization of regular lattice structures leads to great improvement in both elastic and plastic properties. Specific energy absorption, maximum stress, and the elastic moduli in x- and y-directions are improved by 24%, 79%, 56%, and 9%, respectively, compared to the base model. In addition, in the functionally graded optimized models, specific energy absorption and normalized maximum stress are improved by 64% and 56%, respectively, in comparison with the base models.

scholarly journals Mechanical Performance of Additively Manufactured Fiber-Reinforced Functionally Graded Lattices

JOM ◽  
2019 ◽  
Vol 72 (3) ◽  
pp. 1292-1298 ◽  
Author(s):  
János Plocher ◽  
Ajit Panesar
Keyword(s):  
Energy Absorption ◽  
Mechanical Performance ◽  
Weight Ratio ◽  
Short Fiber ◽  
Functionally Graded ◽  
Fused Deposition Modelling ◽  
Valuable Insight ◽  
Fiber Reinforced ◽  
Fused Deposition ◽  
Unit Cells

AbstractLatticing has become a common design practice in additive manufacturing (AM) and represents a key lightweighting strategy to date. Functional graded lattices (FGLs) have recently gained immense traction in the AM community, offering a unique way of tailoring the structural performance. This paper constitutes the first ever investigation on the combination of graded strut- and surface-based lattices with fiber-reinforced AM to further increase the performance-to-weight ratio. The energy absorption behavior of cubic lattice specimens composed of body-centered cubic and Schwarz-P unit cells with different severities of grading but the same mass, considered for uniaxial compression testing and printed by fused deposition modelling of short fiber-reinforced nylon, were investigated. The results elucidate that grading affects the energy absorption capability and deformation behavior of these lattice types differently. These findings can provide engineers with valuable insight into the properties of FGLs, aiding targeted rather than expertise-driven utilization of lattices in design for AM.

scholarly journals Dual Graded Lattice Structures: Generation Framework and Mechanical Properties Characterization

Polymers ◽  
2021 ◽  
Vol 13 (9) ◽  
pp. 1528
Author(s):  
Khaled G. Mostafa ◽  
Guilherme A. Momesso ◽  
Xiuhui Li ◽  
David S. Nobes ◽  
Ahmed J. Qureshi
Keyword(s):  
Mechanical Properties ◽  
Relative Density ◽  
Lattice Structure ◽  
Cell Types ◽  
Functionally Graded ◽  
Unit Cell ◽  
Lattice Structures ◽  
Unit Cells ◽  
Mechanical Properties Characterization ◽  
Graded Lattice

Additive manufacturing (AM) enables the production of complex structured parts with tailored properties. Instead of manufacturing parts as fully solid, they can be infilled with lattice structures to optimize mechanical, thermal, and other functional properties. A lattice structure is formed by the repetition of a particular unit cell based on a defined pattern. The unit cell’s geometry, relative density, and size dictate the lattice structure’s properties. Where certain domains of the part require denser infill compared to other domains, the functionally graded lattice structure allows for further part optimization. This manuscript consists of two main sections. In the first section, we discussed the dual graded lattice structure (DGLS) generation framework. This framework can grade both the size and the relative density or porosity of standard and custom unit cells simultaneously as a function of the structure spatial coordinates. Popular benchmark parts from different fields were used to test the framework’s efficiency against different unit cell types and grading equations. In the second part, we investigated the effect of lattice structure dual grading on mechanical properties. It was found that combining both relative density and size grading fine-tunes the compressive strength, modulus of elasticity, absorbed energy, and fracture behavior of the lattice structure.

scholarly journals Influence of the Miniaturisation Effect on the Effective Stiffness of Lattice Structures in Additive Manufacturing

Metals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1442
Author(s):  
Guillaume Meyer ◽  
Florian Brenne ◽  
Thomas Niendorf ◽  
Christian Mittelstedt
Keyword(s):  
Mechanical Properties ◽  
Additive Manufacturing ◽  
Mechanical Performance ◽  
Effective Properties ◽  
Weight Ratio ◽  
Effective Stiffness ◽  
Analytical Models ◽  
Lattice Structures ◽  
Thin Walled ◽  
The Impact

Thin-walled and cellular structures are characterised by superior lightweight potential due to their advantageous stiffness to weight ratio. They find particular interest in the field of additive manufacturing due to robust and reproducible manufacturability. However, the mechanical performance of such structures strongly depends on the manufacturing process and resultant geometrical imperfections such as porosity, deviations in strut thickness or surface roughness, for which an understanding of their influence is crucially needed. So far, many authors conducted empirical investigations, while analytical methods are rarely applied. In order to obtain efficient design rules considering both mechanical properties and process induced characteristics, analytical descriptions are desirable though. Available analytical models for the determination of effective properties are mostly based on the simple advancement of beam theories, mostly ignoring manufacturing characteristics that, however, strongly influence the mechanical properties of additive manufactured thin-walled structures. One example is the miniaturisation effect, a microstructural effect that has been identified as one of the main drivers of the effective elasto-plastic properties of lightweight structures processed by additive manufacturing. The current work highlights the need to quantify further microstructural effects and to encourage combining them into mesostructural approaches in order to assess macrostructural effective properties. This multi-scale analysis of lattice structures is performed through a comparison between effective stiffness calculated through an analytical approach and compression tests of lattice structures, coupled with an investigation of the arrangement of their struts. In order to cover different potential loading scenarios, bending-dominated and stretch-dominated lattice structures made of the commonly used materials 316L and Ti6Al4V are considered, whereby the impact of microstructural phase transformation during processing is taken into account.

scholarly journals Compressive Behaviour of Additively Manufactured Lattice Structures: A Review

Aerospace ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 207
Author(s):  
Solomon O. Obadimu ◽  
Kyriakos I. Kourousis
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Lattice Structure ◽  
Evolutionary Process ◽  
Lattice Structures ◽  
Compressive Behaviour ◽  
Technology Industry ◽  
Unit Cells ◽  
Superior Mechanical Properties ◽  
And Performance

Additive manufacturing (AM) technology has undergone an evolutionary process from fabricating test products and prototypes to fabricating end-user products—a major contributing factor to this is the continuing research and development in this area. AM offers the unique opportunity to fabricate complex structures with intricate geometry such as the lattice structures. These structures are made up of struts, unit cells, and nodes, and are being used not only in the aerospace industry, but also in the sports technology industry, owing to their superior mechanical properties and performance. This paper provides a comprehensive review of the mechanical properties and performance of both metallic and non-metallic lattice structures, focusing on compressive behaviour. In particular, optimisation techniques utilised to optimise their mechanical performance are examined, as well the primary factors influencing mechanical properties of lattices, and their failure mechanisms/modes. Important AM limitations regarding lattice structure fabrication are identified from this review, while the paucity of literature regarding material extruded metal-based lattice structures is discussed.

Rapid Manufacturing of Cellular Structures of Steel or Titaniumalumide

2011 ◽  
Vol 690 ◽  
pp. 103-106 ◽  
Author(s):  
Lukas Löber ◽  
Denis Klemm ◽  
Uta Kühn ◽  
Jürgen Eckert
Keyword(s):  
Mechanical Properties ◽  
Mechanical Performance ◽  
Steel Powder ◽  
Cellular Structures ◽  
Rapid Manufacturing ◽  
Lattice Structures ◽  
Experimental Conditions ◽  
X Ray ◽  
Whole Process ◽  
Unit Cells

The Selective Laser Melting (SLM) technique is used to produce different cellular structures. Regular unit cells are placed in tensile bars to determine the mechanical performance of different lattice structures. The mechanical properties of the tensile bars with lattice structures are compared to fully dense tensile bars. Tensile bars are produced by conventional casting to compare the mechanical properties between SLM and casting. To exclude other influences, the whole process chain starting from the powder to the finished part is characterized. The different powders, namely 1.4404 steel powder and a titaniumaluminde (Ti-48Al-2Cr-2Nb [TiAl]) powder are characterized via scanning electron microscopy (SEM), energy disperse x-ray spectroscopy (EDS), chemical analysis and light microscopy (LM). In addition measurements of the particle size distribution are conducted. Detailed experimental conditions of the SLM-process are given.

scholarly journals Compressive Properties of Functionally Graded Bionic Bamboo Lattice Structures Fabricated by FDM

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4410
Author(s):  
Zhou Wen ◽  
Ming Li
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Honeycomb Structure ◽  
Absorption Capacity ◽  
Functionally Graded ◽  
Honeycomb Lattice ◽  
Lattice Structures ◽  
Compression Tests ◽  
Uniform Lattice ◽  
Static Compression

Bionic design is considered a promising approach to improve the performance of lattice structures. In this work, bamboo-inspired cubic and honeycomb lattice structures with graded strut diameters were designed and manufactured by 3D printing. Uniform lattice structures were also designed and fabricated for comparison. Quasi-static compression tests were conducted on lattice structures, and the effects of the unit cell and structure on the mechanical properties, energy absorption and deformation mode were investigated. Results indicated that the new bionic bamboo structure showed similar mechanical properties and energy absorption capacity to the honeycomb structure but performed better than the cubic structure. Compared with the uniform lattice structures, the functionally graded lattice structures showed better performance in terms of initial peak strength, compressive modulus and energy absorption.

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.

scholarly journals Compressive Behaviour of Aluminium Pyramidal Lattice Material-Filled Tubes

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3817
Author(s):  
Yingjie Huang ◽  
Wenke Zha ◽  
Yingying Xue ◽  
Zimu Shi
Keyword(s):  
Mechanical Properties ◽  
Energy Absorption ◽  
Al Alloy ◽  
Compressive Behaviour ◽  
Lattice Material ◽  
Empty Tube ◽  
Thin Walled

This study focuses on the uniaxial compressive behaviour of thin-walled Al alloy tubes filled with pyramidal lattice material. The mechanical properties of an empty tube, Al pyramidal lattice material, and pyramidal lattice material-filled tube were investigated. The results show that the pyramidal lattice material-filled tubes are stronger and provide greater energy absorption on account of the interaction between the pyramidal lattice material and the surrounding tube.

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