Fabrication of polymeric lattice structures for optimum energy absorption using Multi Jet Fusion technology

Cellular structures with tailored topologies can be fabricated using additive manufacturing (AM) processes to obtain the desired global and local mechanical properties, such as stiffness and energy absorption. Lattice structures usually fail from the sharp edges owing to the high stress concentration and residual stress. Therefore, it is crucial to analyze the failure mechanism of lattice structures to improve the mechanical properties. In this study, several lattice topologies with fillets were designed, and the effects of the fillets on the stiffness, energy absorption, energy return, and energy loss of an open-cell lattice structure were investigated at a constant relative density. A recently developed high-speed AM multi-jet fusion technology was employed to fabricate lattice samples with two different unit cell sizes. Nonlinear simulations using ANSYS software were performed to investigate the mechanical properties of the samples. Experimental compression and loading–unloading tests were conducted to validate the simulation results. The results showed that the stiffness and energy absorption of the lattice structures can be improved significantly by the addition of fillets and/or vertical struts, which also influence other properties such as the failure mechanism and compliance. By adding the fillets, the failure location can be shifted from the sharp edges or joints to other regions of the lattice structure, as observed by comparing the failure mechanisms of type B and C structures with that of the type A structure (without fillets). The results of this study suggest that AM software designers should consider filleted corners when developing algorithms for generating various types of lattice structures automatically. Additionally, it was found that the accumulation of unsintered powder in the sharp corners of lattice geometries can also be minimized by the addition of fillets to convert the sharp corners to curved edges.

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Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-021-00251-1 ◽

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.

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Multi-objective design optimization of additively manufactured lattice structures for improved energy absorption performance

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406221995542 ◽

2021 ◽

pp. 095440622199554

Author(s):

Recep M Gorguluarslan

Keyword(s):

Energy Absorption ◽

Response Surfaces ◽

Optimization Process ◽

Truss Optimization ◽

Size Optimization ◽

Lattice Structures ◽

Multi Objective ◽

Lattice Design ◽

Highly Nonlinear ◽

Absorption Performance

This paper aims to improve the energy absorption performance of stiffness-optimized lattice structures by utilizing a multi-objective surrogate-based size optimization that considers the additive manufacturing (AM) constraints such as the minimum printable size. A truss optimization is first utilized at the unit cell level under static compressive loads for stiffness maximization and two optimized lattice configurations called the Face-Body Centered Cubic (FBCC) lattice and the Octet Cubic (OC) are obtained. A multi-objective size optimization process is then carried out to improve the energy absorption capabilities of those lattice designs using non-linear compression simulations with Nylon12 material to be fabricated by the Multi Jet Fusion (MJF) AM process. Thin plate spline (TPS) interpolation method is found to produce very high accuracy as the surrogate model to predict the highly nonlinear response surfaces of energy absorption objectives in the optimization. Compared to the lattice designs with uniform strut diameters, by using the optimization process, the maximum energy absorption efficiency ( EAEm) and the crush stress efficiency ( CSE) of the OC lattice design are further improved up to 33% and 37%, respectively. The FBCC lattice design is also found to have superior EAEm performance compared to the existing lattice types considered for fabricating by the MJF process in the literature.

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Supportless Lattice Structures for Energy Absorption Fabricated by Fused Deposition Modeling

3D Printing and Additive Manufacturing ◽

10.1089/3dp.2019.0089 ◽

2020 ◽

Vol 7 (2) ◽

pp. 85-96 ◽

Cited By ~ 1

Author(s):

Ajeet Kumar ◽

Saurav Verma ◽

Jeng-Ywan Jeng

Keyword(s):

Energy Absorption ◽

Fused Deposition Modeling ◽

Lattice Structures ◽

Fused Deposition ◽

Deposition Modeling

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

Proceedings of the Institution of Mechanical Engineers Part L Journal of Materials Design and Applications ◽

10.1177/1464420720923004 ◽

2020 ◽

Vol 234 (8) ◽

pp. 1099-1116 ◽

Cited By ~ 2

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.

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Deformation mode and energy absorption of polycrystal-inspired square-cell lattice structures

Applied Mathematics and Mechanics ◽

10.1007/s10483-020-2648-8 ◽

2020 ◽

Vol 41 (10) ◽

pp. 1561-1582

Author(s):

Yijie Bian ◽

Puhao Li ◽

Fan Yang ◽

Peng Wang ◽

Weiwei Li ◽

...

Keyword(s):

Energy Absorption ◽

Deformation Mode ◽

Lattice Structures ◽

Square Cell

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Effect of Annealing on Microstructures and Mechanical Properties of PA-12 Lattice Structures Proceeded by Multi Jet Fusion Technology

Additive Manufacturing ◽

10.1016/j.addma.2021.102285 ◽

2021 ◽

pp. 102285

Author(s):

Mubasher Ali ◽

Resy Kumala Sari ◽

Uzair Sajjad ◽

Muhammad Sultan ◽

Hafiz Muhammad Ali

Keyword(s):

Mechanical Properties ◽

Lattice Structures ◽

Fusion Technology ◽

Microstructures And Mechanical Properties

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On the mechanical behaviour of additively manufactured metamaterials under dynamic conditions

EPJ Web of Conferences ◽

10.1051/epjconf/202125005006 ◽

2021 ◽

Vol 250 ◽

pp. 05006

Author(s):

R. Sancho ◽

F. Galvez ◽

C.L. Garrido ◽

S. Perosanz-Amarillo ◽

D. Barba

Keyword(s):

Energy Absorption ◽

Computational Models ◽

Volume Fraction ◽

Testing Machine ◽

High Energy ◽

Lattice Structures ◽

Static Tests ◽

Dynamic Conditions ◽

Lattice Materials ◽

High Energy Absorption

High-energy absorption and light-weightiness are two critical properties for impact protection in the aerospace sector. In the past, the use of periodic honeycomb structures or random porous metallic foams were the preferred route to obtain a good specific-energy absorption performance. In recent years, the use of additive manufacturing has increased the design freedom creating a new generation of reticulated and porous materials: the metamaterials or lattice materials. The internal geometries of these lattice structures can be tuned for superior optimal properties, e.g., energyabsorption and density. However, the mechanics of these materials under impact need to be understood with the purpose of mechanical optimisation, and the computational models validated. In this work, we present the experimental compressive behaviour, at room temperature, of two Ti6Al4V lattice structures under static and dynamic conditions. The quasi-static tests were performed by using a universal testing machine while the dynamic tests were conducted at 480s-1 with a split-Hopkinson bar. In all cases, the deformation process was filmed to analyse the failure. Finally, finiteelement simulations were done, employing the Johnson-Cook model, to describe the response of the alloy. The simulations were able to reflect the failure characteristics of each metamaterial but were not able to describe the macroscopic response due to the differences between the experimental and computational volume fraction.

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