Abstract:Bio-inspired self-similar hierarchical honeycombs are multifunctional cellular topologies used for resisting various loadings. However, the crushing behavior under large plastic deformation is still unknown. This paper investigates the in-plane compressive response of selective laser melting (SLM) fabricated hierarchical honeycombs. The effects of hierarchical order, relative density as well as constituent material are evaluated. The results show that at small deformation, the AlSi10Mg alloy hierarchical honey… Show more
“…The results (Table 1) indicate that the mechanical anisotropy of the 316L steel material is inconspicuous, which is different from that of AlSi10Mg alloy. 11,23 Out-of-plane compressive response of hierarchical honeycombs…”
Section: Uniaxial Tensile Characteristics Of Parent Materialsmentioning
confidence: 99%
“…The results (Table 1) indicate that the mechanical anisotropy of the 316L steel material is inconspicuous, which is different from that of AlSi10Mg alloy. 11,23 Figure 2.(a) Geometric dimension and SLM fabricating directions of tensile test coupon; (b) Uniaxial tensile stress-strain response of 316L steel parent material.…”
Hierarchical honeycomb is a topology presenting better weight-efficiency than the conventional honeycomb. However, the existing research are mainly conducted based on an assumption of uniform in-plane wall thickness. Rare studies consider the effect of different wall thicknesses in hierarchies. This paper investigates the out-of-plane crashworthiness of vertex hexagonal-based hierarchical honeycombs with non-uniform wall thickness in distinct hierarchies experimentally and theoretically. The coupons with parent material of 316L steel are obtained using Selective Laser Melting fabricating technique. The experimental results indicate that the first order honeycombs with uniform wall thickness experience a failure mechanism transition from local elastic buckling to local plastic buckling of cell walls at the critical density of 0.0772. A progressive folding wave can be identified when relative density is lower than 0.0386. At any edge length ratio, the plateau crushing stress increases monotonously as the increase of the wall thickness ratio, but not for the half wavelength. Both the half wavelength and maximum plateau crushing stresses are linearly related to relative density. For the first order honeycombs, the effect of edge length ratio is more considerable on the plateau crushing stress than the wall thickness ratio. The second order honeycombs exhibit higher half wavelengths and maximum plateau crushing stresses than the first order honeycombs owing to the more considerable cell wall constraint among the hierarchies. Compared to the hierarchical honeycombs with uniform wall thicknesses at relative densities of 0.005∼0.0386, the non-uniform wall thickness enhances the maximum plateau crushing stress significantly, especially at a low relative density, and the maximum improvements for first order and second order honeycombs are 71.5 and 48.6%, respectively. However, the absolute improvements are similar, averaging approximately 1.18 MPa. This work provides a foundation for developing ultralight hierarchical material candidates applied in passive protection equipment, such as aircrafts and vehicles.
“…The results (Table 1) indicate that the mechanical anisotropy of the 316L steel material is inconspicuous, which is different from that of AlSi10Mg alloy. 11,23 Out-of-plane compressive response of hierarchical honeycombs…”
Section: Uniaxial Tensile Characteristics Of Parent Materialsmentioning
confidence: 99%
“…The results (Table 1) indicate that the mechanical anisotropy of the 316L steel material is inconspicuous, which is different from that of AlSi10Mg alloy. 11,23 Figure 2.(a) Geometric dimension and SLM fabricating directions of tensile test coupon; (b) Uniaxial tensile stress-strain response of 316L steel parent material.…”
Hierarchical honeycomb is a topology presenting better weight-efficiency than the conventional honeycomb. However, the existing research are mainly conducted based on an assumption of uniform in-plane wall thickness. Rare studies consider the effect of different wall thicknesses in hierarchies. This paper investigates the out-of-plane crashworthiness of vertex hexagonal-based hierarchical honeycombs with non-uniform wall thickness in distinct hierarchies experimentally and theoretically. The coupons with parent material of 316L steel are obtained using Selective Laser Melting fabricating technique. The experimental results indicate that the first order honeycombs with uniform wall thickness experience a failure mechanism transition from local elastic buckling to local plastic buckling of cell walls at the critical density of 0.0772. A progressive folding wave can be identified when relative density is lower than 0.0386. At any edge length ratio, the plateau crushing stress increases monotonously as the increase of the wall thickness ratio, but not for the half wavelength. Both the half wavelength and maximum plateau crushing stresses are linearly related to relative density. For the first order honeycombs, the effect of edge length ratio is more considerable on the plateau crushing stress than the wall thickness ratio. The second order honeycombs exhibit higher half wavelengths and maximum plateau crushing stresses than the first order honeycombs owing to the more considerable cell wall constraint among the hierarchies. Compared to the hierarchical honeycombs with uniform wall thicknesses at relative densities of 0.005∼0.0386, the non-uniform wall thickness enhances the maximum plateau crushing stress significantly, especially at a low relative density, and the maximum improvements for first order and second order honeycombs are 71.5 and 48.6%, respectively. However, the absolute improvements are similar, averaging approximately 1.18 MPa. This work provides a foundation for developing ultralight hierarchical material candidates applied in passive protection equipment, such as aircrafts and vehicles.
“…In general, a sandwich structure is composed of solid face and back plates, and a lightweight cellular core. While the cellular core absorbs a considerable amount of energy, various types of cores with excellent energy absorption capacity have been proposed, for instance, metal foam core [ 11 , 12 ], polymeric foam core [ 13 , 14 ], foam concrete core [ 15 , 16 , 17 ], honeycomb core [ 18 ], negative Poisson’s ratio honeycomb core [ 19 ], foam-filled honeycomb core [ 20 , 21 ], and other high-performance cores [ 22 ]. The mechanical performance and energy absorption of these core materials or structures subjected to quasi-static and dynamic loads have been extensively and intensively investigated based on the approaches of experimental tests, numerical simulations, and theoretical analyses.…”
Foam-filled honeycombs have been widely applied due to their excellent load transfer mitigation and energy absorption capacity. In the present study, a layered graded foam concrete-filled auxetic honeycomb was proposed by tuning its overall compression deformation mode to layer-by-layer deformation mode to realize multi-level structural protection. The effect of the honeycomb cell-wall thickness gradient (with an average thickness of 0.25 mm, thickness gradients of 0.30:0.25:0.20, 0.35:0.25:0.15 and 0.40:0.25:0.10, and corresponding positive gradients) and the foam concrete filler density gradient (408:575:848, 848:575:408) on the response mode, load transfer, energy absorption, and Poisson’s ratio of the proposed composite was systematically investigated. The results showed that the graded composite exhibited an obvious layered deformation mode and a negative Poisson’s ratio effect under relatively low and moderate loading rates (1 m/s, 10 m/s, respectively), especially with the foam concrete density gradient. Under a high loading rate (100 m/s), the graded composite demonstrated progressive collapse initiating from the loading end with a layer-by-layer crushing mode, regardless of the thickness and density gradient. In the response of the composite with a 0.2:0.2:0.2 thickness ratio and a 408:575:848 foam concrete gradient subjected to 1 m/s crushing, the first-layer, second-layer, and third-layer foam concrete absorbed 94.62%, 88.72%, and 86.94% of the total foam concrete energy absorption in the corresponding crushing stage, respectively. Compared with the counterpart homogeneous composites, although the graded composite had an insignificant improvement on energy absorption (less than 5%), it was able to significantly reduce the peak load (as high as 30%) to mitigate the load transfer to the protected structure. The effective Poisson’s ratio of the first layer in the composite with positive gradient (408:575:848) increased to −2 then converged to −0.6 under 2 m/s and 10 m/s crushing, and ranged from −0.4 to −0.1 under 50 m/s and 100 m/s crushing, respectively. The effective Poisson’s ratio of the middle and bottom layers increased to −2 initially and converged to range −0.4 to −0.1, regardless of the crushing speed. The staged response mode of the graded composite facilitated the realization of multi-level structure protection with significantly reduced peak load transferred to the protected structure and tuned energy absorption.
“…These structures can present multiple attractive properties depending on the specific application, such as light weight, high specific stiffness, and high energy absorption capacity [ 5 , 6 , 7 , 8 , 9 ]. Sandwich panel fabrication is one of the most widely studied and reported in the literature [ 10 , 11 , 12 , 13 , 14 , 15 ]. Properties such as high impact energy absorption increase the use of cellular materials as protective structures [ 16 , 17 , 18 ].…”
A three-dimensional auxetic structure based on a known planar configuration including a design parameter producing asymmetry is proposed in this study. The auxetic cell is designed by topology analysis using classical Timoshenko beam theory in order to obtain the required orthotropic elastic properties. Samples of the structure are fabricated using the ABSplus fused filament technique and subsequently tested under quasi-static compression to statistically determine the Poisson’s ratio and Young’s modulus. The experimental results show good agreement with the topological analysis and reveal that the proposed structure can adequately provide different elastic properties in its three orthogonal directions. In addition, three point bending tests were carried out to determine the mechanical behavior of this cellular structure. The results show that this auxetic cell influences the macrostructure to exhibit different stiffness behavior in three working directions.
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