Functionally graded cellular materials, which combine cellular materials with a gradient of properties, have been recently investigated as cores of sandwich panels.
The present work aims to evaluate the flexural properties of functionally graded cellular structures with a gradient of cell thickness on configurations recently proposed. The structures hexagonal honeycomb (Hr), lotus (Lt), and hexagonal honeycomb with Plateau borders (Pt) were designed with three different gradients of cell thickness. The parts were manufactured by material extrusion using FFF (Fused Filament Fabrication).
To evaluate the mechanical properties, three-point bending tests were conducted, both experimentally and by numerical modelling, by means of the finite element method. The materials used were polylactic acid (PLA) and aluminum.
Although experimental and numerical results exhibited some deviations, they revealed the same trends. The results showed that the stiffness and the absorbed energy of the graded Hr, Lt and Pt structures, made of PLA, are higher than such values for the regular hexagonal honeycombs. For the same gradient of cell thickness, the lotus structure tends to exhibit the highest stiffness and absorbed energy, while the hexagonal honeycomb arrangement achieves the largest value of strength. Graded aluminum specimens also attain higher values of stiffness, strength and absorbed energy in comparison with non-graded hexagonal honeycomb configurations.
Thus, the use of gradients of cell thickness can promote structures with higher stiffness and absorbed energy, which may compete with the conventional structures of sandwich panel cores.
SunZShiSGuoX, et al.On compressive properties of composite sandwich structures with grid reinforced honeycomb core. Compos Part B Eng2016; 94: 245–252.
2.
VinsonJR. The behavior of sandwich structures of isotropic and composite materials. Boca Raton, FL: CRC Press, 1999.
3.
EvansAGHutchinsonJWFleckNA, et al.The topological design of multifunctional cellular metals. Prog Mater Sci2001; 46: 309–327.
4.
LiuJHaoCYeW, et al.Free vibration and transient dynamic response of functionally graded sandwich plates with power-law nonhomogeneity by the scaled boundary finite element method. Comput Methods Appl Mech Eng2021; 376: 113665.
5.
GibsonLJAshbyMF. Cellular solids: structure and properties. Cambridge: Cambridge University Press, 1997.
6.
ZhuFLuGRuanD, et al.Plastic deformation, failure and energy absorption of sandwich structures with metallic cellular cores. Int J Prot Struct2010; 1: 507–541.
AraújoHLeiteMRibeiroAR, et al.The effect of geometry on the flexural properties of cellular core structures. Proc Inst Mech Eng Part L J Mater Des Appl2019; 233: 338–347.
9.
UllahIBrandtMFeihS. Failure and energy absorption characteristics of advanced 3D truss core structures. Mater Des2016; 92: 937–948.
10.
ZhangYXiaoMZhangX, et al.Topological design of sandwich structures with graded cellular cores by multiscale optimization. Comput Methods Appl Mech Eng2020; 361: 112749.
11.
DeshpandeVSFleckNA. Collapse of truss core sandwich beams in 3-point bending. Int J Solids Struct2001; 38: 6275–6305.
12.
MonteiroJSardinhaMAlvesF, et al.Evaluation of the effect of core lattice topology on the properties of sandwich panels produced by additive manufacturing. Proc Inst Mech Eng Part L J Mater Des Appl2021; 235: 1312–1324.
13.
UzalASonmezFOOzFE, et al.A composite sandwich plate with a novel core design. Compos Struct2018; 193: 198–211.
14.
DuYLiHLuoZ, et al.Topological design optimization of lattice structures to maximize shear stiffness. Adv Eng Softw2017; 112: 211–221.
15.
HabibFNIovenittiPMasoodSH, et al.Fabrication of polymeric lattice structures for optimum energy absorption using multi Jet fusion technology. Mater Des2018; 155: 86–98.
16.
MastersIGEvansKE. Models for the elastic deformation of honeycombs. Compos Struct1996; 35: 403–422.
17.
LiTWangL. Bending behavior of sandwich composite structures with tunable 3D-printed core materials. Compos Struct2017; 175: 46–57.
18.
MirandaALeiteMReisL, et al.Evaluation of the influence of design in the mechanical properties of honeycomb cores used in composite panels. Proc Inst Mech Eng Part L J Mater Des Appl2021; 235: 1325–1340.
19.
BruJLeiteMRibeiroA, et al.Bioinspired structures for core sandwich composites produced by fused deposition modelling. Proc Inst Mech Eng Part L J Mater Des Appl2020; 234: 379–393.
20.
IngroleAHaoALiangR. Design and modeling of auxetic and hybrid honeycomb structures for in-plane property enhancement. Mater Des2017; 117: 72–83.
21.
SurjadiJUGaoLDuH, et al.Mechanical metamaterials and their engineering applications. Adv Eng Mater2019; 21: 1800864.
ChoySYSunC-NLeongKF, et al.Compressive properties of functionally graded lattice structures manufactured by selective laser melting. Mater Des2017; 131: 112–120.
24.
VatanabeSLRubioWMSilvaECN. Modeling of functionally graded materials. In: Comprehensive materials processing. Amsterdam: Elsevier, 2014, pp. 261–282.
25.
MiyamotoYKaysserW A.RabinBH, et al.Functionally graded materials: design, processing and application. New York: Springer, 1999.
26.
KhanS. Analysis of tribological applications of functionally graded materials in mobility engineering. Int J Sci Eng Res2015; 6: 1150–1160.
27.
ZhangCChenFHuangZ, et al.Additive manufacturing of functionally graded materials: a review. Mater Sci Eng A2019; 764: 138209.
28.
BrothersAHDunandDC. Mechanical properties of a density-graded replicated aluminum foam. Mater Sci Eng A2008; 489: 439–443.
29.
AjdariACanavanPNayeb-HashemiH, et al.Mechanical properties of functionally graded 2-D cellular structures: a finite element simulation. Mater Sci Eng A2009; 499: 434–439.
30.
ZengHBPattofattoSZhaoH, et al.Impact behaviour of hollow sphere agglomerates with density gradient. Int J Mech Sci2010; 52: 680–688.
31.
SalehBJiangJMaA, et al.Effect of main parameters on the mechanical and wear behaviour of functionally graded materials by centrifugal casting: a review. Met Mater Int2019; 25: 1395–1409.
32.
MirzaaliMJHerranz de la NavaAGunashekarD, et al.Mechanics of bioinspired functionally graded soft-hard composites made by multi-material 3D printing. Compos Struct2020; 237: 111867.
33.
XiaoLSongW. Additively-manufactured functionally graded Ti-6Al-4 V lattice structures with high strength under static and dynamic loading: experiments. Int J Impact Eng2018; 111: 255–272.
34.
LiangMLiZLuF, et al.Theoretical and numerical investigation of blast responses of continuous-density graded cellular materials. Compos Struct2017; 164: 170–179.
35.
NiknamHAkbarzadehAH. Graded lattice structures: simultaneous enhancement in stiffness and energy absorption. Mater Des2020; 196: 109129.
36.
ZhangZZhangQZhangD, et al.Enhanced mechanical performance of brazed sandwich panels with high density square honeycomb-corrugation hybrid cores. Thin-Walled Struct2020; 151: 106757.
37.
LimmahakhunSOloyedeASitthiseripratipK, et al.Stiffness and strength tailoring of cobalt chromium graded cellular structures for stress-shielding reduction. Mater Des2017; 114: 633–641.
ZhangX-YFangGLeeflangS, et al.Topological design, permeability and mechanical behavior of additively manufactured functionally graded porous metallic biomaterials. Acta Biomater2019; 84: 437–452.
40.
LiSZhaoSHouW, et al.Functionally graded Ti-6Al-4 V meshes with high strength and energy absorption. Adv Eng Mater2016; 18: 34–38.
41.
SunYGuoLWangT, et al.Bending strength and failure of single-layer and double-layer sandwich structure with graded truss core. Compos Struct2019; 226: 111204.
42.
JinXWangZNingJ, et al.Dynamic response of sandwich structures with graded auxetic honeycomb cores under blast loading. Compos Part B Eng2016; 106: 206–217.
43.
XuGZhaiJZengT, et al.Response of composite sandwich beams with graded lattice core. Compos Struct2015; 119: 666–676.
44.
CroccoloDDe AgostinisMOlmiG. Experimental characterization and analytical modelling of the mechanical behaviour of fused deposition processed parts made of ABS-M30. Comput Mater Sci2013; 79: 506–518.
45.
CrumpSS. Apparatus and Method for Creating 1. Crump, S. S. Apparatus and Method for Creating Three-Dimensional Objects. US Pat. 5,121,329 15 (1992).Three-Dimensional Objects. US Pat 5,121,329.
46.
TurnerBNStrongRGoldSA. A review of melt extrusion additive manufacturing processes: i. Process design and modeling. Rapid Prototyp J2014; 20: 192–204.
47.
RybachukMAlice MaugerCFiedlerT, et al.Anisotropic mechanical properties of fused deposition modeled parts fabricated by using acrylonitrile butadiene styrene polymer. J Polym Eng2017; 37: 699–706.
48.
FarahSAndersonDGLangerR. Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review. Adv Drug Delivery Rev2016; 107: 367–392.
49.
RonanWDeshpandeVSFleckNA. The tensile ductility of cellular solids: the role of imperfections. Int J Solids Struct2016; 102–103: 200–213.
50.
AraújoHLeiteMRibeiroA, et al.Investigating the contribution of geometry on the failure of cellular core structures obtained by additive manufacturing. Frat ed Integrità Strutt2019; 13: 478–486.
51.
FernandesJDeusAMReisL, et al.Study of the influence of 3D printing parameters on the mechanical properties of PLA. In: 3rd International Conference on Progress in Additive Manufacturing (Pro-AM 2018). Singapore, 2018, pp. 547–552.
52.
CES 2019. The Cambridge engineering selector, Granta Design.
53.
ASTM C393-00: 2000. Standard test method for flexural properties of sandwich constructions. Stand West Conshohocken, PA: ASTM, 2000.
54.
StocchiAColabellaLCisilinoA, et al.Manufacturing and testing of a sandwich panel honeycomb core reinforced with natural-fiber fabrics. Mater Des2014; 55: 394–403.
55.
FiedlerTÖchsnerA. Experimental analysis of the flexural properties of sandwich panels with cellular core materials. Materwiss Werksttech2008; 39: 121–124.
56.
BitzerT. Honeycomb technology: material design, manufacturing applications and testing. New York: Springer, 1997.
