Flexible chiral honeycomb cores generally exhibit nonlinear elastic properties due to large geometric deformation.The effective elastic moduli and Poisson's ratio typically vary with an increase in deformation.Her...Flexible chiral honeycomb cores generally exhibit nonlinear elastic properties due to large geometric deformation.The effective elastic moduli and Poisson's ratio typically vary with an increase in deformation.Here,the size and shape optimization of the chiral hexagonal honeycombs was performed to keep the Young's moduli and Poisson's ratio unchanged under large deformations.The size of the honeycomb unit cell and the position coordinates of the key points were defined simultaneously as design variables.The equivalent Young's modulus and Poisson's ratio of chiral honeycombs were calculated through geometric nonlinear analysis.The objective was to minimize the allowable tolerance between the prescribed and actual properties within the range of the target strain.A genetic algorithm was then adopted.The optimal results demonstrate that the chiral honeycombs can maintain effective elastic properties that do not vary under large deformation.These results are meaningful to morphing aircraft designs.展开更多
A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and dep...A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and depth.To this end,a framework built upon the experiment-based,machine learning approach for grooving parameters prediction was presented.The continuously grooved honeycomb bending experiments with various radii,honeycomb types,and thicknesses were carried out,and then the deformation level of honeycombs at different grooving spacing was quantitatively evaluated.A criterion for determining the grooving spacing was proposed by setting an appropriate tolerance for the out-of-plane compression strength.It was found that as the curvature increases,the grooving spacing increases due to the deformation level of honeycombs being more severe at a smaller bending radius.Besides,the grooving spacing drops as the honeycomb thickness increases,and the cell size has a positive effect on the grooving spacing,while the relative density has a negative effect on the grooving spacing.Furthermore,the data-driven Gaussian Process(GP)was trained from the collected data to predict the grooving spacing efficiently.The grooving angle and depth were calculated using the geometrical relationship of honeycombs before and after bending.Finally,the grooving parameters design and verification of a honeycomb sandwich fairing part were conducted based on the proposed grooving method.展开更多
This paper introduces a three-dimensional concave hexagonal honeycomb structure(3D-CHH) with enhanced impact resistance, developed from a two-dimensional concave hexagonal honeycomb structure(2D-CHH), to advance the a...This paper introduces a three-dimensional concave hexagonal honeycomb structure(3D-CHH) with enhanced impact resistance, developed from a two-dimensional concave hexagonal honeycomb structure(2D-CHH), to advance the application of metamaterials in ship protection structures. Both structures were fabricated using additive manufacturing techniques and subjected to quasi-static compression testing to evaluate their deformation modes and energy-absorbing capabilities. Combined experimental and numerical simulation results revealed that 2D-CHH exhibited a “<” mode,while 3D-CHH demonstrated an inward concave “I” mode, with 3D-CHH showing superior negative Poisson's ratio characteristics. The deformation behavior of both structures progresses through four distinct phases: elastic zone,stress plateau zone, plateau stress enhancement zone, and densification zone characterized by rapid stress elevation.The 3D-CHH structure exhibits superior energy absorption compared with both 2D-CHH and conventional honeycomb structures, achieving nearly twice the specific energy absorption of 2D-CHH. Additionally, 3D-CHH shows an 8.4%improvement in energy absorption efficiency compared with 2D-CHH. The enhanced negative Poisson's ratio effect and superior energy absorption properties of 3D-CHH enable effective ship protection while reducing structural weight.展开更多
This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analyti...This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analytical model developed,which makes good use of the advantage of the first-order shear deformation theory(FSDT),the multi-segment decomposition technique,the virtual spring technology,the Jacobi-Ritz approach,and the transfer function method.The equivalent material properties of HHC are firstly determined by the modified Gibson’s formula,and the related energy equations are derived for the HHC-FRCS-CS combined shells,from which the fundamental frequencies,the mode shapes,and the forced vibration responses are solved.The current model is verified through the discussion of convergence and comparative analysis with the associated published literature and finite element(FE)results.The effects of geometric parameters of HHC on the dynamic property of the structure are further investigated with the verified model.It reveals that the vibration suppression capability can be greatly enhanced by reducing the ratio of HHC thickness to total thickness and the ratio of wall thickness of honeycomb cell to overall radius,and by increasing the ratio of length of honeycomb cell to overall radius and honeycomb characteristic angle of HHC.展开更多
Layered honeycomb intermetallic phases have attracted considerable research interest due to the wide array of exciting physical properties inherent in these materials.Here,we follow the evolution in structure and elec...Layered honeycomb intermetallic phases have attracted considerable research interest due to the wide array of exciting physical properties inherent in these materials.Here,we follow the evolution in structure and electronic properties of a relatively unexplored material system,Sr_(1−x)Ca_(x)PdAs,as the hexagonal PdAs honeycomb layer in SrPdAs distorts into the orthorhombic CaPdAs structure.The Sr-rich compounds(x=0 to 1/3)form symmetric,hexagonal honeycomb PdAs layers,whereas in the Ca-rich region(x=1/2 to 1)the PdAs layers distort into an orthorhombic structure featuring long and short Pd–Pd distances.This dis tortion occurs when the average Pd–Pd distance falls below 4.21Å.All compounds are observed to exhibit metallic temperature-dependent resistivity trends.There are no apparent discontinuities indicative of metal-to-insulator transitions and the room temperature resistivity values range from 18 to 180 mΩcm.In total,this work maps out the structural and electronic phase diagram of Sr_(1−x)Cax PdAs compounds.展开更多
基金National Key Research and Development Program(2017YFB1102800)NSFC for Excellent Young Scholars(11722219)National Natural Science Foundation of China(11772258,51790171,5171101743)。
文摘Flexible chiral honeycomb cores generally exhibit nonlinear elastic properties due to large geometric deformation.The effective elastic moduli and Poisson's ratio typically vary with an increase in deformation.Here,the size and shape optimization of the chiral hexagonal honeycombs was performed to keep the Young's moduli and Poisson's ratio unchanged under large deformations.The size of the honeycomb unit cell and the position coordinates of the key points were defined simultaneously as design variables.The equivalent Young's modulus and Poisson's ratio of chiral honeycombs were calculated through geometric nonlinear analysis.The objective was to minimize the allowable tolerance between the prescribed and actual properties within the range of the target strain.A genetic algorithm was then adopted.The optimal results demonstrate that the chiral honeycombs can maintain effective elastic properties that do not vary under large deformation.These results are meaningful to morphing aircraft designs.
基金the National Natural Science Foundation of China(No.11902256)the Natural Science Basic Research Program of Shaanxi,China(No.2019JQ-479).
文摘A novel grooving method for eliminating the bending-induced collapse of hexagonal honeycombs has been proposed,which lies in determining the appropriate grooving parameters,including the grooving spacing,angle,and depth.To this end,a framework built upon the experiment-based,machine learning approach for grooving parameters prediction was presented.The continuously grooved honeycomb bending experiments with various radii,honeycomb types,and thicknesses were carried out,and then the deformation level of honeycombs at different grooving spacing was quantitatively evaluated.A criterion for determining the grooving spacing was proposed by setting an appropriate tolerance for the out-of-plane compression strength.It was found that as the curvature increases,the grooving spacing increases due to the deformation level of honeycombs being more severe at a smaller bending radius.Besides,the grooving spacing drops as the honeycomb thickness increases,and the cell size has a positive effect on the grooving spacing,while the relative density has a negative effect on the grooving spacing.Furthermore,the data-driven Gaussian Process(GP)was trained from the collected data to predict the grooving spacing efficiently.The grooving angle and depth were calculated using the geometrical relationship of honeycombs before and after bending.Finally,the grooving parameters design and verification of a honeycomb sandwich fairing part were conducted based on the proposed grooving method.
基金financially supported by the National Natural Science Foundation of China (Grant No.52201334)。
文摘This paper introduces a three-dimensional concave hexagonal honeycomb structure(3D-CHH) with enhanced impact resistance, developed from a two-dimensional concave hexagonal honeycomb structure(2D-CHH), to advance the application of metamaterials in ship protection structures. Both structures were fabricated using additive manufacturing techniques and subjected to quasi-static compression testing to evaluate their deformation modes and energy-absorbing capabilities. Combined experimental and numerical simulation results revealed that 2D-CHH exhibited a “<” mode,while 3D-CHH demonstrated an inward concave “I” mode, with 3D-CHH showing superior negative Poisson's ratio characteristics. The deformation behavior of both structures progresses through four distinct phases: elastic zone,stress plateau zone, plateau stress enhancement zone, and densification zone characterized by rapid stress elevation.The 3D-CHH structure exhibits superior energy absorption compared with both 2D-CHH and conventional honeycomb structures, achieving nearly twice the specific energy absorption of 2D-CHH. Additionally, 3D-CHH shows an 8.4%improvement in energy absorption efficiency compared with 2D-CHH. The enhanced negative Poisson's ratio effect and superior energy absorption properties of 3D-CHH enable effective ship protection while reducing structural weight.
基金supported by the National Natural Science Foundation of China(Nos.52175079 and 12072091)the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environments of China(No.6142905192512)+2 种基金the Fundamental Research Funds for the Central Universities of China(No.N2103026)the Major Projects of AeroEngines and Gas Turbines of China(No.J2019-I-0008-0008)the China Postdoctoral Science Foundation(No.2020M680990)。
文摘This study analyzes and predicts the vibration characteristics of fiberreinforced composite sandwich(FRCS)cylindrical-spherical(CS)combined shells with hexagon honeycomb core(HHC)for the first time based on an analytical model developed,which makes good use of the advantage of the first-order shear deformation theory(FSDT),the multi-segment decomposition technique,the virtual spring technology,the Jacobi-Ritz approach,and the transfer function method.The equivalent material properties of HHC are firstly determined by the modified Gibson’s formula,and the related energy equations are derived for the HHC-FRCS-CS combined shells,from which the fundamental frequencies,the mode shapes,and the forced vibration responses are solved.The current model is verified through the discussion of convergence and comparative analysis with the associated published literature and finite element(FE)results.The effects of geometric parameters of HHC on the dynamic property of the structure are further investigated with the verified model.It reveals that the vibration suppression capability can be greatly enhanced by reducing the ratio of HHC thickness to total thickness and the ratio of wall thickness of honeycomb cell to overall radius,and by increasing the ratio of length of honeycomb cell to overall radius and honeycomb characteristic angle of HHC.
基金supported by the Center for Emergent Materials,an NSF-funded MRSEC under award no.DMR-1420451Partial support for transport measurements by M.R.S.was provided by AFOSR project no.FA9550-18-1-0335+1 种基金J.E.G.acknowledges the Camille and Henry Dreyfus Foundation for partial support.D.W.gratefully acknowledges the financial support by the German Science Foundation DFG Research Fellowship(WE6480/1)Y.W.and W.W.thank the Ohio Supercomputer Center for computer time under grant PAS0072.
文摘Layered honeycomb intermetallic phases have attracted considerable research interest due to the wide array of exciting physical properties inherent in these materials.Here,we follow the evolution in structure and electronic properties of a relatively unexplored material system,Sr_(1−x)Ca_(x)PdAs,as the hexagonal PdAs honeycomb layer in SrPdAs distorts into the orthorhombic CaPdAs structure.The Sr-rich compounds(x=0 to 1/3)form symmetric,hexagonal honeycomb PdAs layers,whereas in the Ca-rich region(x=1/2 to 1)the PdAs layers distort into an orthorhombic structure featuring long and short Pd–Pd distances.This dis tortion occurs when the average Pd–Pd distance falls below 4.21Å.All compounds are observed to exhibit metallic temperature-dependent resistivity trends.There are no apparent discontinuities indicative of metal-to-insulator transitions and the room temperature resistivity values range from 18 to 180 mΩcm.In total,this work maps out the structural and electronic phase diagram of Sr_(1−x)Cax PdAs compounds.
