Boundary conformal design of laser sintered sandwich cores and simulation of graded lattice cells using a forward homogenization approach

Marschall, David; Rippl, Herbert; Ehrhart, Frank; Schagerl, Martin

doi:10.1016/j.matdes.2020.108539

Cited by 14 publications

(21 citation statements)

References 17 publications

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“…This implies that it can be used to model the thickness-dependent and orthotropic response of lattice structures represented by 1D beam meshes with great detail. However, the computational cost of FE lattice models in which every strut is discretized is very high, which is why the current trend rather goes towards RVE-based homogenization approaches [ 43 , 58 ]. The decision to utilize detailed mapping or homogenization largely depends on the overall size of the FE model and should be justified for every application individually.…”

Section: Discussionmentioning

confidence: 99%

“…This principle for the efficient layout of structural members was for lightweight design purposes fundamentally described by Michell [ 40 ] and has in context of AM recently re-gained attention [ 41 , 42 ]. The outer part dimensions of 20 × 35 × 100 mm

were chosen in compliance with previous related research [ 43 ]. The two fabricated orientations comprised a part oriented with its first two principal axes parallel to the global

-directions (XZ

) and another generally oriented variant (

) to test the accuracy of the simulation routine for structures deviating from the build chamber axes (C

).…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Structural Response Prediction of Thin-Walled Additively Manufactured Parts Considering Orthotropy, Thickness Dependency and Scatter

Sindinger

Marschall²,

Kralovec

et al. 2021

Materials

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Besides the design freedom offered by additive manufacturing, another asset lies within its potential to accelerate product development processes by rapid fabrication of functional prototypes. The premise to fully exploit this benefit for lightweight design is the accurate structural response prediction prior to part production. However, the peculiar material behavior, characterized by anisotropy, thickness dependency and scatter, still constitutes a major challenge. Hence, a modeling approach for finite element analysis that accounts for this inhomogeneous behavior is developed by example of laser-sintered short-fiber-reinforced polyamide 12. Orthotropic and thickness-dependent Young’s moduli and Poisson’s ratios were determined via quasi-static tensile tests. Thereof, material models were generated and implemented in a property mapping routine for finite element models. Additionally, a framework for stochastic finite element analysis was set up for the consideration of scatter in material properties. For validation, thin-walled parts on sub-component level were fabricated and tested in quasi-static three-point bending experiments. Elastic parameters showed considerable anisotropy, thickness dependency and scatter. A comparison of the predicted forces with experimentally evaluated reaction forces disclosed substantially improved accuracy when utilizing the novel inhomogeneous approach instead of conventional homogeneous approaches. Furthermore, the variability observed in the structural response of loaded parts could be reproduced by the stochastic simulations.

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Section: Discussionmentioning

confidence: 99%

were chosen in compliance with previous related research [ 43 ]. The two fabricated orientations comprised a part oriented with its first two principal axes parallel to the global

-directions (XZ

) and another generally oriented variant (

) to test the accuracy of the simulation routine for structures deviating from the build chamber axes (C

).…”

Section: Methodsmentioning

confidence: 99%

Structural Response Prediction of Thin-Walled Additively Manufactured Parts Considering Orthotropy, Thickness Dependency and Scatter

Sindinger

Marschall²,

Kralovec

et al. 2021

Materials

Self Cite

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“…The FH approach (Yuan and Fish, 2008;Fish, 2014), which was in good agreement with the test results for small displacement analyses (Marschall et al, 2020), was used to calculate the macro-homogeneous linear material properties of Figure 5 Discretization and material modeling approach starting with the bottom face sheet (bfs) and ending with the top face sheet (tfs) the listed lattice cell types in Figure 2. The FH process provides linear orthotropic elastic properties, which were represented by the MAT9ORT material card for numerical investigation via OptiStruct TM .…”

Section: Numerical Investigationmentioning

confidence: 90%

Design, simulation, testing and application of laser-sintered conformal lattice structures on component level

Marschall¹,

Sindinger

Rippl³

et al. 2021

RPJ

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Purpose Laser sintering of polyamide lattice-based lightweight fairing components for subsequent racetrack testing requires a high quality and a reliable design. Hence, the purpose of this study was to develop a design methodology for such additively manufactured prototypes, considering efficient generation and structural simulation of boundary conformal non-periodic lattices, optimization of production parameters as well as experimental validation. Design/methodology/approach Multi-curved, sandwich structure-based demonstrators were designed, simulated and experimentally tested with boundary conformal lattice cells. The demonstrator’s non-periodic lattice cells were simplified by forward homogenization processes. To represent the stiffness of the top and bottom face sheet, constant isotropic and mapped transversely isotropic simulation approaches were compared. The dimensional accuracy of lattice cells and demonstrators were measured with a gauge caliper and a three-dimensional scanning system. The optimized process parameters for lattice structures were transferred onto a large volume laser sintering system. The stiffness of each finite element analysis was verified by an experimental test setup including a digital image correlation system. Findings The stiffness prediction of the mapped was superior to the constant approach and underestimated the test results with −6.5%. Using a full scale fairing the applicability of the development process was successfully demonstrated. Originality/value The design approach elaborated in this research covers aspects from efficient geometry generation over structural simulation to experimental testing of produced parts. This methodology is not only relevant in the context of motor sports but is transferrable for all additively manufactured large scale components featuring a complex lattice sub-structure and is, therefore, relevant across industries.

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“…However, some lattice structures are bending-dominant structures with higher energy absorption capacity [ 40 , 41 , 42 ]. TPMS unit cells have an above-average surface area with low stress generated during static loadings as well as better handling of angular loads as a result of the better load distribution compared to strut-based design strut-based lattices [ 43 , 44 ]. Topology-optimized lattices possess higher stiffness at lower relative density than TPMS and strut-based lattices [ 45 ].…”

Section: Introductionmentioning

confidence: 99%

Dual Graded Lattice Structures: Generation Framework and Mechanical Properties Characterization

Mostafa

Momesso²,

et al. 2021

Polymers

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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.

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Boundary conformal design of laser sintered sandwich cores and simulation of graded lattice cells using a forward homogenization approach

Cited by 14 publications

References 17 publications

Structural Response Prediction of Thin-Walled Additively Manufactured Parts Considering Orthotropy, Thickness Dependency and Scatter

Structural Response Prediction of Thin-Walled Additively Manufactured Parts Considering Orthotropy, Thickness Dependency and Scatter

Design, simulation, testing and application of laser-sintered conformal lattice structures on component level

Dual Graded Lattice Structures: Generation Framework and Mechanical Properties Characterization

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