This study pioneers the integrated fabrication of magnesium corrugated-core sandwich structures using wire-arc directed energy deposition(WA-DED).Two sandwich structures—V-type and X-type—were designed with optimize...This study pioneers the integrated fabrication of magnesium corrugated-core sandwich structures using wire-arc directed energy deposition(WA-DED).Two sandwich structures—V-type and X-type—were designed with optimized deposition paths to achieve comparable grain morphology while enhancing strength.The compression properties and failure modes of the two corrugated-core sandwich structures were examined through quasi-static compression tests.Results showed that the V-type structure exhibited a higher specific compressive strength(93 MPa∙cm^(3)/g)than the X-type structure(72 MPa∙cm^(3)/g).Both finite element analysis and experimental compression tests indicated that failure occurred at the midsection of the corrugated core.This work offers valuable insights for the efficient fabrication of high-strength corrugated-core sandwich structures.展开更多
The steel-epoxy-steel sandwich structures provide enhanced corrosion resistance and fatigue resistance,making them suitable for pipeline rehabilitation with effective repair and long-term durability.However,the repair...The steel-epoxy-steel sandwich structures provide enhanced corrosion resistance and fatigue resistance,making them suitable for pipeline rehabilitation with effective repair and long-term durability.However,the repair quality can be compromised by disbond between the steel and epoxy layers,whichmay result frominsufficient epoxy injection.Conventional ultrasonic testing faces challenges in accurately locating disbond defects due to aliased echo interference at interfaces.This paper proposes a signal processing algorithm for improving the accuracy of ultrasonic reflection method for detecting disbond defects between steel and epoxy layers.First,a coati optimization algorithmvariational mode decomposition(COA-VMD)is applied to adaptively decompose the ultrasonic signals and extract the intrinsic mode function components that show high correlation with the defect-related signals.Then,by calculating the relative reflectance at the interface and establishing a quantitative evaluation index based on acoustic impedance discontinuity,the locations of disbond defects are identified.Experimental results demonstrate that this method can effectively detect the locations of disbond defects between steel and epoxy layers.展开更多
Polymethacrylimide(PMI)foam has the highest specific stiffness and strength among polymer foams,with excellent radar-absorbing capabilities,which provide it with broad prospects in underwater ap-plications.To evaluate...Polymethacrylimide(PMI)foam has the highest specific stiffness and strength among polymer foams,with excellent radar-absorbing capabilities,which provide it with broad prospects in underwater ap-plications.To evaluate the impact resistance of PMI foam sandwich structures,the dynamic response and energy absorption characteristics of PMI foam sandwich structures with different core layers under various water impact loads were investigated using combined experimental and numerical methods.A fluid-structure interaction device with a diffusion angle was used for water impact testing of the PMI foam sandwich structures.The 3D-DIC technique was employed to process the deformation images of the sandwich-structure back panel captured by the high-speed cameras.Numerical simulations were performed to analyze the dynamic deformation process of the PMI foam core.The results indicated that the maximum deformation of the back panel exhibited a nonlinear relationship with the impulse.Below the critical impulse,the maximum deformation of the back panel plateaued,which was determined by the core density.Beyond the critical impulse,the rate of deformation increased with the impulse was governed by the core thickness.Compared with different sandwich panels,PMI foam sandwich struc-tures demonstrate significant advantages in terms of impact resistance under high-impulse conditions.展开更多
The mechanical performance of an all-composite pyramidal lattice truss core sandwich structure was investigated both theoretically and experimentally.Sandwich structures were fabricated with a hot compression molding ...The mechanical performance of an all-composite pyramidal lattice truss core sandwich structure was investigated both theoretically and experimentally.Sandwich structures were fabricated with a hot compression molding method using carbon fiber reinforced composite T700/3234.The out-of-plane compression and shear tests were conducted.Experimental results showed that the all-composite pyramidal lattice truss core sandwich structures were more weight efficient than other metallic lattice truss core sandwich structures.Failure modes revealed that node rupture dominated the mechanical behavior of sandwich structures.展开更多
The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge t...The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference(EMI)shielding composites.In this work,a sandwich struc-ture polyimide(PI)composite film with alternative 2D-MXene network and 1D-Silver nanowires(Ag NWs)network was prepared through the“electrospinning-immersion-hot pressing”method.With the increase of Ag NWs content,the EMI shielding effectiveness(SE)gradually increases while maintaining good flexibility and mechanical robustness.The EMI SE and the tensile strength of 150μm thick sand-wich composite film can reach up to 79.54 dB and 39.82 MPa,respectively.The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content,which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.展开更多
Novel sandwich structure-like nanofiber multilayered meshes were fabricated via electrospinning. The purpose of the present work was to control zoledronic acid release via the novel structure of sandwich structure-lik...Novel sandwich structure-like nanofiber multilayered meshes were fabricated via electrospinning. The purpose of the present work was to control zoledronic acid release via the novel structure of sandwich structure-like meshes. The in vitro release experiments reveal that the drug release speed and initial burst release were controllable by adjusting the thicknesses of electrospun barrier mesh and drug-loaded mesh. Compared with those of other drug delivery systems, the main advantages of the sandwich structure-like fiber meshes are facile preparation conditions and the generality for hydrophobic and hydrophilic pharmaceuticals.展开更多
Due to the incompatibility of the interlaminar deformations,the interface debonding or cracking usually happens in a layered magnetoelectric(ME)structure under an applied load.In this paper,the transient responses of ...Due to the incompatibility of the interlaminar deformations,the interface debonding or cracking usually happens in a layered magnetoelectric(ME)structure under an applied load.In this paper,the transient responses of the anti-plane interface cracks in piezoelectric(PE)-piezomagnetic(PM)sandwich structures are studied by the standard methods of the integral transform and singular integral equation.Discussion on the numerical examples indicates that the PE-PM-PE structure under electric impact is more likely to fracture than the PM-PE-PM structure under a magnetic impact.The dynamic stress intensity factors(DSIFs)are more sensitive to the variation of the active layer thickness.The effects of the material constants on the DSIFs are dependent on the roles played by PE and PM media during the deformation process.展开更多
Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight.This makes them very suitable for lightweight applications,where high stiffness to weight ratios are needed....Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight.This makes them very suitable for lightweight applications,where high stiffness to weight ratios are needed.Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets.However,adhesive bonding is prone to delamination,a failure mode that is often difficult to detect.This paper presents the results of delamination testing of fully additive manufactured(AM)AlSi10Mg sandwich structures with pyramidal lattice truss core using Laser Powder Bed Fusion(LPBF).The faces and struts are 0.5 mm thick,while the core is 2 mm thick.The inclination of the struts is 45°.To characterise the bonding strength,climbing drum peel tests and out-of-plane tensile tests are performed.Analytical formulas are derived to predict the expected failure loads and modes.The analytics and tests are supported by finite element(FE)calculations.From the analytic approach,design guidelines to avoid delamination in AM sandwich structures are derived.The study presents a critical face sheet thickness to strut diameter ratio for which the structure can delaminate.This ratio is mainly influenced by the inclination of the struts.The peel tests resulted in face yielding,which can also be inferred from the analytics and numerics.The out-of-plane tensile tests didn’t damage the structure.展开更多
Improving the thermal decomposition performance of hexanitrohexaazaisowurtzitane(CL-20)by appropriate methods is helpful to promote the combustion performance of CL-20-based solid propellants.In this study,we synthesi...Improving the thermal decomposition performance of hexanitrohexaazaisowurtzitane(CL-20)by appropriate methods is helpful to promote the combustion performance of CL-20-based solid propellants.In this study,we synthesized a sandwich structure of CL-20 and nanoporous carbon scaffolds film(NCS)and emphatically studied the thermal decomposition performance of the composite structure.Thermogravimetric analysis and differential scanning calorimetry were used to measure the thermal decomposition process of the composite structure.The kinetic parameters of thermal decomposition were calculated by the thermal dynamic analysis software AKTS.These results showed that the thermal decomposition performance of the sandwich structure of CL-20 and NCS was better than CL-20.Among the tested samples,NCS with a pore size of 15 nm had the best catalytic activity for the thermal decomposition of CL-20.Moreover,the thermal decomposition curve of the composite structure at the heating rate of 1 K/min was deconvoluted by mathematical method to study the thermal decomposition process.And a possible catalytic mechanism was proposed.The excellent thermal decomposition performance is due to the sandwich structure enhances the interface reaction of CL-20 and NCS.This work may promote the extensive use of CL-20 in the field of solid rocket propellant.展开更多
Potential damage in composite structures caused by hail ice impact is an essential safety threat to the aircraft in flight.In this study,a nonlinear finite element(FE)model is developed to investigate the dynamic resp...Potential damage in composite structures caused by hail ice impact is an essential safety threat to the aircraft in flight.In this study,a nonlinear finite element(FE)model is developed to investigate the dynamic response and damage behavior of hybrid corrugated sandwich structures subjected to high velocity hail ice impact.The impact and breaking behavior of hail are described using the FE-smoothed particle hydrodynamics(FE-SPH)method.A rate-dependent progressive damage model is employed to capture the intra-laminar damage response;cohesive element and surface-based cohesive contact are implemented to predict the inter-laminar delamination and sheet/core debonding phenomena respectively.The transient processes of sandwich structure under different hail ice impact conditions are analyzed.Comparative analysis is conducted to address the influences of core shape and impact position on the impact performance of sandwich structures and the corresponding energy absorption characteristics are also revealed.展开更多
This paper is concerned with the decay of Saint-Venant end effects for plane deformations of piezoelectric （PE）-piezomagnetic （PM） sandwich structures, where a PM layer is located between two PE layers with the sa...This paper is concerned with the decay of Saint-Venant end effects for plane deformations of piezoelectric （PE）-piezomagnetic （PM） sandwich structures, where a PM layer is located between two PE layers with the same material properties or reversely. The end of the sandwich structure is subjected to a set of self-equilibrated magneto-electro-elastic loads. The upper and lower surfaces of the sandwich structure axe mechanically free, electrically open or shorted as well as magnetically open or shorted. Firstly the constitutive equations of PE mate- rials and PM materials for plane strain are given and normalized. Secondly, the simplified state space approach is employed to arrange the constitutive equations into differential equations in a matrix form. Finally, by using the transfer matrix method, the characteristic equations for eigen- values or decay rates axe derived. Based on the obtained characteristic equations, the decay rates for the PE-PM-PE and PM-PE-PM sandwich structures are calculated. The influences of the electromagnetic boundary conditions, material properties of PE layers and volume fraction on the decay rates are discussed in detail.展开更多
Aircraft laminated composite components often suffer a variety of high velocity impacts with large quantity of energy,which usually affects aircraft behavior and would incur component damages,even disastrous consequen...Aircraft laminated composite components often suffer a variety of high velocity impacts with large quantity of energy,which usually affects aircraft behavior and would incur component damages,even disastrous consequences.Therefore,one investigates the impact resistance of a new type of composite material,Ti/CFRP/Ti sandwich structure,and launches impact tests by using an air gun test system.Then one acquires the critical breakthrough rate of the structure and analyzes the damages.The results show that the main failure mode of the front titanium sheet is shear plugging and brittle fracture of adhesive layer with fiber breakage,while the back titanium sheet is severely ripped.The rear damage is worse than the front one.Compared with traditional CFRP laminates,the critical breakthrough rate of Ti/CFRP/Ti sandwich structure is improved by 69.9% when suffered the impact of a bearing ball with 2mm radius.展开更多
A wood-based X-type lattice sandwich structure was manufactured by insertion-glue method.The birch was used as core,and Oriented Strand Board was used as panel of the sandwich structure.The short beam shear properties...A wood-based X-type lattice sandwich structure was manufactured by insertion-glue method.The birch was used as core,and Oriented Strand Board was used as panel of the sandwich structure.The short beam shear properties and the failure modes of the wood-based X-type lattice sandwich structure with different core direction(vertical and parallel),unit specification(120 mm×60 mm and 60 mm×60 mm),core size(50 mm and 60 mm),and drilling depth(9 mm and 12 mm)were investigated by a short beam shear test and the establishment of a theoretical model to study the equivalent shear modulus and deflection response of the X-type lattice sandwich structure.Results from the short beam shear test and the theoretical model showed that the failure modes of the wood-based X-type lattice sandwich structure were mainly the wrinkling and crushing of the panels under three-point bending load.The experimental values of deflection response of various type specimens were higher than the theoretical values of them.For the core direction of parallel,the smaller the unit specification is,the shorter the core size is,and the deeper the drilling depth is,the greater the short beam shear properties of the wood-based X-type lattice sandwich structure is.展开更多
The preparation of highly sensitive and stable non-enzymatic glucose sensors is critical to the prevention and treatment of diabetes.Fe_(3)O_(4)@Au@Co Fe-LDH is prepared through a spontaneous galvanic displacement rea...The preparation of highly sensitive and stable non-enzymatic glucose sensors is critical to the prevention and treatment of diabetes.Fe_(3)O_(4)@Au@Co Fe-LDH is prepared through a spontaneous galvanic displacement reaction.A series of structural characterizations testify the successful formation of Fe_(3)O_(4)@Au@Co FeLDH electrocatalyst,with the Au intercalating between Fe_(3)O_(4)and LDH to form the sandwich structure.Cyclic voltammetry tests indicate that Au is responsible for the electrocatalytic oxidation of glucose.The characterizations of the electrochemical sensor for glucose detection indicate that Fe_(3)O_(4)@Au@Co FeLDH possesses high sensitivity of 6342μA m M^(-1)cm^(-2),with an extremely low oxidation potential of 0.82 V vs.RHE.Even with the high glucose concentration of 15 m M,the sensitivity remains at 4359μA m M^(-1)cm^(-2).Due to the broad linear detection range(0.0375 to 15.64 m M)and the low limit of detection(12.7μM),Fe_(3)O_(4)@Au@Co Fe-LDH is applicable towards practical application.Thanks to the sandwich structure,which confines the Au in between Fe_(3)O_(4)and Co Fe-LDH,the Fe_(3)O_(4)@Au@Co Fe-LDH glucose sensor shows high long-term stability and satisfactory selectivity.The successful synthesis of the sandwichstructured Fe_(3)O_(4)@Au@Co Fe-LDH provides a new conception for the design of highly sensitive and stable non-enzymatic glucose electrodes.展开更多
The so-called″X-cor sandwich structure″is a highly promising novel material as an alternative to honeycomb used in aircraft.Although much work has been conducted on the performance of the X-cor sandwich structure,th...The so-called″X-cor sandwich structure″is a highly promising novel material as an alternative to honeycomb used in aircraft.Although much work has been conducted on the performance of the X-cor sandwich structure,the gap is still hardly bridged between experimental results and theoretical analyses.Therefore,a method has been innovated to establish semi-empirical formula for the prediction of compressive and shear moduli of X-cor sandwich structure composites,by combining theoretical analyses and experimental data.In addition,aprediction software was first developed based on the proposed method,of which the accuracy was verified through confirmatory experiments.This software can offer a direct reference or guide for engineers in structural designing.展开更多
In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gu...In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of loading.Moreover,the explicit solver was run in Abaqus to create the finite element model.The numerically obtained test results were compared with the experimental to check the accuracy of the modelling.The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus.Furthermore,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined.The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading.Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance.Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption.However,inscribe circle diameter had a negative influence on the ballistic resistance.Also,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions.The energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.展开更多
A cellular material in the form of 3-layered sandwich structure material was prepared via sole use of mechanical stirring without any use of a foaming agent,while Tween-80 was employed as a foam stabilizer via a devel...A cellular material in the form of 3-layered sandwich structure material was prepared via sole use of mechanical stirring without any use of a foaming agent,while Tween-80 was employed as a foam stabilizer via a developed in-situ mold casting.The resulting structure displayed a good appearance with no visual defects.The 3-layered composition of the sandwish structure,“nonporous resin layer-porous foam layer-nonporous resin layer”,was examined in terms of the microstructure,density&density distribution,pulverization ratio,mechanical strength,insulation and flame retardant performance.It was indicated from the results that the bonding between the resin layer and foam layer was tight,while the tensile rupture always occurred in the porous layer.Also,the density of the sandwich structure material was symmetrical with“saddle”distribution,and a uniform density for any given layer.The increase in the density at the interface layer provided a good interpretation for the tensile rupture never occurred at the interface.The brittleness resistance of the developed material was significantly improved,and the pulverization ratio was sharply decreased from 9.93%to 0.31%.The material acquired a thermal conductivity and limiting oxygen index(LOI)of 0.0241 W/m⋅K and 29.92%,respectively,indicating potential use of such materials broadly in fields of insulation and flame retardancy.展开更多
This paper is a review of the past research of mechanical testing methods for natural fibre honeycomb sandwich structure as well as failure modes analysis at a microscopic level by using Scanning Electron Microscope (...This paper is a review of the past research of mechanical testing methods for natural fibre honeycomb sandwich structure as well as failure modes analysis at a microscopic level by using Scanning Electron Microscope (SEM). As the world is garnering attention towards renewable resources for environmental purposes, studies of natural fibre have been increasing as well as the application of natural fibre throughout various industries such as aerospace, automobiles, and construction sectors. This paper is started with brief information regarding the honeycomb sandwich structure, introduction to natural fibre, its applications as well as the factors affecting the performances of the structure. Next, the mechanical testing methods are listed out as well as the expected outcomes obtained from the respective testing. The mechanical properties are also identified by conducting lab tests according to the ASTM standard for sandwich and core structures. The microstructure of the deformed samples is then examined under Scanning Electron Microscope (SEM) by using different magnifications to study the failure mechanisms of the samples. The images obtained from the SEM test are analyzed by using fractography which will show the failure modes of the samples. This article is based on past research conducted by professional on the related topic.展开更多
Substrate photopatterning has provided versatile applications in biomedical fields. Herein, an universal and efficient photoligation reaction has been used to prepare a patterned capture substrate for a sandwich SERS ...Substrate photopatterning has provided versatile applications in biomedical fields. Herein, an universal and efficient photoligation reaction has been used to prepare a patterned capture substrate for a sandwich SERS immunoassay. Photoirradiation induces mild and efficient immobilization of antibodies at the desired region of a gold surface, and the antibody-antigen interaction helps the substrate to capture the antigens in solution specifically. After exposing to SERS probes, i.e., the gold nanoparticles labelled with both antibodies and intrinsically strong Raman reporters, multiple quantitative SERS determination of antigens can be achieved with high sensitivity and specificity. The limit of detection can be as low as 10^(-12) mol/L for four kinds of cancer biomarkers, which provides a promising method for the construction of highly sensitive and high-throughput SERS detection chip and the application of in vitro diagnosis.展开更多
By introducing a dimensionless parameter to couple the two objectives, weight and radar absorbing performance, into a single objective function, a multi-objective optimization procedure for the radar absorbing sandwic...By introducing a dimensionless parameter to couple the two objectives, weight and radar absorbing performance, into a single objective function, a multi-objective optimization procedure for the radar absorbing sandwich structure （RASS） with a cellular core is proposed. The optimization models considered are one-side clamped sandwich panels with four kinds of cores subject to uniformly distributed loads. The average specular reflectivity calculated with the transfer matrix method and the periodic moment method is utilized to characterize the radar absorbing performance, while the mechanical constraints include the facesheet yielding, core shearing, and facesheet wrinkling. The optimization analysis indicates that the sandwich structure with a two-dimensional （2D） composite lattice core filled with ultra-lightweight sponge may be a better candidate of lightweight RASS than those with cellular foam or hexagonal honeycomb cores. The 2D Kagome lattice is found to outperform the square lattice with respect to radar absorbing.展开更多
基金supported by JCKY Project(Grant No.JCKY2023602B012).
文摘This study pioneers the integrated fabrication of magnesium corrugated-core sandwich structures using wire-arc directed energy deposition(WA-DED).Two sandwich structures—V-type and X-type—were designed with optimized deposition paths to achieve comparable grain morphology while enhancing strength.The compression properties and failure modes of the two corrugated-core sandwich structures were examined through quasi-static compression tests.Results showed that the V-type structure exhibited a higher specific compressive strength(93 MPa∙cm^(3)/g)than the X-type structure(72 MPa∙cm^(3)/g).Both finite element analysis and experimental compression tests indicated that failure occurred at the midsection of the corrugated core.This work offers valuable insights for the efficient fabrication of high-strength corrugated-core sandwich structures.
基金supported by the Research Funding of Hangzhou International Innovation Institute of Beihang University(Grant No.015731201-2024KQ126)National Key R&D Program of China(Grant No.2023YFF0716600)National Natural Science Foundation of China(Grant No.62271021).
文摘The steel-epoxy-steel sandwich structures provide enhanced corrosion resistance and fatigue resistance,making them suitable for pipeline rehabilitation with effective repair and long-term durability.However,the repair quality can be compromised by disbond between the steel and epoxy layers,whichmay result frominsufficient epoxy injection.Conventional ultrasonic testing faces challenges in accurately locating disbond defects due to aliased echo interference at interfaces.This paper proposes a signal processing algorithm for improving the accuracy of ultrasonic reflection method for detecting disbond defects between steel and epoxy layers.First,a coati optimization algorithmvariational mode decomposition(COA-VMD)is applied to adaptively decompose the ultrasonic signals and extract the intrinsic mode function components that show high correlation with the defect-related signals.Then,by calculating the relative reflectance at the interface and establishing a quantitative evaluation index based on acoustic impedance discontinuity,the locations of disbond defects are identified.Experimental results demonstrate that this method can effectively detect the locations of disbond defects between steel and epoxy layers.
文摘Polymethacrylimide(PMI)foam has the highest specific stiffness and strength among polymer foams,with excellent radar-absorbing capabilities,which provide it with broad prospects in underwater ap-plications.To evaluate the impact resistance of PMI foam sandwich structures,the dynamic response and energy absorption characteristics of PMI foam sandwich structures with different core layers under various water impact loads were investigated using combined experimental and numerical methods.A fluid-structure interaction device with a diffusion angle was used for water impact testing of the PMI foam sandwich structures.The 3D-DIC technique was employed to process the deformation images of the sandwich-structure back panel captured by the high-speed cameras.Numerical simulations were performed to analyze the dynamic deformation process of the PMI foam core.The results indicated that the maximum deformation of the back panel exhibited a nonlinear relationship with the impulse.Below the critical impulse,the maximum deformation of the back panel plateaued,which was determined by the core density.Beyond the critical impulse,the rate of deformation increased with the impulse was governed by the core thickness.Compared with different sandwich panels,PMI foam sandwich struc-tures demonstrate significant advantages in terms of impact resistance under high-impulse conditions.
基金supported by the National Natural Science Foundation of China under Grant Nos.90816024 and 10872059the Major State Basic Research Development Program of China under Grant No. 2011CB610303+2 种基金the Fundamental Research Funds for the central Universities grant No. HIT. NSRIF. 2010069the Program of Excellent Team in Harbin Institute of Technologythe Program for New Century Excellent Talents in University under Grant No.NCET-08-0152
文摘The mechanical performance of an all-composite pyramidal lattice truss core sandwich structure was investigated both theoretically and experimentally.Sandwich structures were fabricated with a hot compression molding method using carbon fiber reinforced composite T700/3234.The out-of-plane compression and shear tests were conducted.Experimental results showed that the all-composite pyramidal lattice truss core sandwich structures were more weight efficient than other metallic lattice truss core sandwich structures.Failure modes revealed that node rupture dominated the mechanical behavior of sandwich structures.
基金the Fund of Natural Science Founda-tion of Shaanxi Provincial(No.2021JQ-111)the Fund of Basic and Applied Fundamental Research of Guangdong Provincial(No.2020A1515110861).
文摘The design and fabrication of electromagnetic interference shielding films with a novel structure to eliminate undesirable electromagnetic pollution is an important research direction.However,it is still a challenge to combine and organize nanofillers in different dimensions into the structured network in polymer-based electromagnetic interference(EMI)shielding composites.In this work,a sandwich struc-ture polyimide(PI)composite film with alternative 2D-MXene network and 1D-Silver nanowires(Ag NWs)network was prepared through the“electrospinning-immersion-hot pressing”method.With the increase of Ag NWs content,the EMI shielding effectiveness(SE)gradually increases while maintaining good flexibility and mechanical robustness.The EMI SE and the tensile strength of 150μm thick sand-wich composite film can reach up to 79.54 dB and 39.82 MPa,respectively.The prepared flexible and robust PI composite film with a sandwich structure has high EMI SE with less metal content,which can provide guidelines for the development of high-performance EMI polymeric films with potentials in wearable devices and equipment.
文摘Novel sandwich structure-like nanofiber multilayered meshes were fabricated via electrospinning. The purpose of the present work was to control zoledronic acid release via the novel structure of sandwich structure-like meshes. The in vitro release experiments reveal that the drug release speed and initial burst release were controllable by adjusting the thicknesses of electrospun barrier mesh and drug-loaded mesh. Compared with those of other drug delivery systems, the main advantages of the sandwich structure-like fiber meshes are facile preparation conditions and the generality for hydrophobic and hydrophilic pharmaceuticals.
基金Project supported by the National Natural Science Foundation of China(Nos.11272222,11502108,and 11611530686)the Natural Science Foundation for Distinguished Young Scholars of Jiangsu Province of China(No.BK20140037)
文摘Due to the incompatibility of the interlaminar deformations,the interface debonding or cracking usually happens in a layered magnetoelectric(ME)structure under an applied load.In this paper,the transient responses of the anti-plane interface cracks in piezoelectric(PE)-piezomagnetic(PM)sandwich structures are studied by the standard methods of the integral transform and singular integral equation.Discussion on the numerical examples indicates that the PE-PM-PE structure under electric impact is more likely to fracture than the PM-PE-PM structure under a magnetic impact.The dynamic stress intensity factors(DSIFs)are more sensitive to the variation of the active layer thickness.The effects of the material constants on the DSIFs are dependent on the roles played by PE and PM media during the deformation process.
基金Part of this work was supported by the German Federal Ministry for Economic Affairs and Energy(BMWi)(Grant No.20E1713B).
文摘Sandwich structures possess a high bending stiffness compared to monolithic structures with a similar weight.This makes them very suitable for lightweight applications,where high stiffness to weight ratios are needed.Most common manufacturing methods of sandwich structures involve adhesive bonding of the core material with the sheets.However,adhesive bonding is prone to delamination,a failure mode that is often difficult to detect.This paper presents the results of delamination testing of fully additive manufactured(AM)AlSi10Mg sandwich structures with pyramidal lattice truss core using Laser Powder Bed Fusion(LPBF).The faces and struts are 0.5 mm thick,while the core is 2 mm thick.The inclination of the struts is 45°.To characterise the bonding strength,climbing drum peel tests and out-of-plane tensile tests are performed.Analytical formulas are derived to predict the expected failure loads and modes.The analytics and tests are supported by finite element(FE)calculations.From the analytic approach,design guidelines to avoid delamination in AM sandwich structures are derived.The study presents a critical face sheet thickness to strut diameter ratio for which the structure can delaminate.This ratio is mainly influenced by the inclination of the struts.The peel tests resulted in face yielding,which can also be inferred from the analytics and numerics.The out-of-plane tensile tests didn’t damage the structure.
基金supported by the National Natural Science Foundation of China(No:21975227)the Shanxi Province Graduate Student Innovation Project(No:2020SY403)。
文摘Improving the thermal decomposition performance of hexanitrohexaazaisowurtzitane(CL-20)by appropriate methods is helpful to promote the combustion performance of CL-20-based solid propellants.In this study,we synthesized a sandwich structure of CL-20 and nanoporous carbon scaffolds film(NCS)and emphatically studied the thermal decomposition performance of the composite structure.Thermogravimetric analysis and differential scanning calorimetry were used to measure the thermal decomposition process of the composite structure.The kinetic parameters of thermal decomposition were calculated by the thermal dynamic analysis software AKTS.These results showed that the thermal decomposition performance of the sandwich structure of CL-20 and NCS was better than CL-20.Among the tested samples,NCS with a pore size of 15 nm had the best catalytic activity for the thermal decomposition of CL-20.Moreover,the thermal decomposition curve of the composite structure at the heating rate of 1 K/min was deconvoluted by mathematical method to study the thermal decomposition process.And a possible catalytic mechanism was proposed.The excellent thermal decomposition performance is due to the sandwich structure enhances the interface reaction of CL-20 and NCS.This work may promote the extensive use of CL-20 in the field of solid rocket propellant.
基金supported by the Natural Science Foundation of Jiangsu Province(Grant No.BK20180855)Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(Grant No.MCMS-E-0219Y01)Research and Practice Innovation Program of postgraduates in Jiangsu Province(Grant No.KYCX20-3076)。
文摘Potential damage in composite structures caused by hail ice impact is an essential safety threat to the aircraft in flight.In this study,a nonlinear finite element(FE)model is developed to investigate the dynamic response and damage behavior of hybrid corrugated sandwich structures subjected to high velocity hail ice impact.The impact and breaking behavior of hail are described using the FE-smoothed particle hydrodynamics(FE-SPH)method.A rate-dependent progressive damage model is employed to capture the intra-laminar damage response;cohesive element and surface-based cohesive contact are implemented to predict the inter-laminar delamination and sheet/core debonding phenomena respectively.The transient processes of sandwich structure under different hail ice impact conditions are analyzed.Comparative analysis is conducted to address the influences of core shape and impact position on the impact performance of sandwich structures and the corresponding energy absorption characteristics are also revealed.
基金Project supported by the National Natural Science Foundation of China (No. 10972147)
文摘This paper is concerned with the decay of Saint-Venant end effects for plane deformations of piezoelectric （PE）-piezomagnetic （PM） sandwich structures, where a PM layer is located between two PE layers with the same material properties or reversely. The end of the sandwich structure is subjected to a set of self-equilibrated magneto-electro-elastic loads. The upper and lower surfaces of the sandwich structure axe mechanically free, electrically open or shorted as well as magnetically open or shorted. Firstly the constitutive equations of PE mate- rials and PM materials for plane strain are given and normalized. Secondly, the simplified state space approach is employed to arrange the constitutive equations into differential equations in a matrix form. Finally, by using the transfer matrix method, the characteristic equations for eigen- values or decay rates axe derived. Based on the obtained characteristic equations, the decay rates for the PE-PM-PE and PM-PE-PM sandwich structures are calculated. The influences of the electromagnetic boundary conditions, material properties of PE layers and volume fraction on the decay rates are discussed in detail.
基金funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Aircraft laminated composite components often suffer a variety of high velocity impacts with large quantity of energy,which usually affects aircraft behavior and would incur component damages,even disastrous consequences.Therefore,one investigates the impact resistance of a new type of composite material,Ti/CFRP/Ti sandwich structure,and launches impact tests by using an air gun test system.Then one acquires the critical breakthrough rate of the structure and analyzes the damages.The results show that the main failure mode of the front titanium sheet is shear plugging and brittle fracture of adhesive layer with fiber breakage,while the back titanium sheet is severely ripped.The rear damage is worse than the front one.Compared with traditional CFRP laminates,the critical breakthrough rate of Ti/CFRP/Ti sandwich structure is improved by 69.9% when suffered the impact of a bearing ball with 2mm radius.
基金supported by National Natural Science Foundation of China(31470581)Fundamental Research Funds for the Central Universities(2572016EBJ1).
文摘A wood-based X-type lattice sandwich structure was manufactured by insertion-glue method.The birch was used as core,and Oriented Strand Board was used as panel of the sandwich structure.The short beam shear properties and the failure modes of the wood-based X-type lattice sandwich structure with different core direction(vertical and parallel),unit specification(120 mm×60 mm and 60 mm×60 mm),core size(50 mm and 60 mm),and drilling depth(9 mm and 12 mm)were investigated by a short beam shear test and the establishment of a theoretical model to study the equivalent shear modulus and deflection response of the X-type lattice sandwich structure.Results from the short beam shear test and the theoretical model showed that the failure modes of the wood-based X-type lattice sandwich structure were mainly the wrinkling and crushing of the panels under three-point bending load.The experimental values of deflection response of various type specimens were higher than the theoretical values of them.For the core direction of parallel,the smaller the unit specification is,the shorter the core size is,and the deeper the drilling depth is,the greater the short beam shear properties of the wood-based X-type lattice sandwich structure is.
基金financially supported by the National Natural Science Foundation of China(No.21805308)the Taishan Scholar Project of Shandong Province,the Fundamental Research Funds for the Central Universities(No.19CX05001A)the Graduate Innovation Project of China University of Petroleum(No.YCX2020052)。
文摘The preparation of highly sensitive and stable non-enzymatic glucose sensors is critical to the prevention and treatment of diabetes.Fe_(3)O_(4)@Au@Co Fe-LDH is prepared through a spontaneous galvanic displacement reaction.A series of structural characterizations testify the successful formation of Fe_(3)O_(4)@Au@Co FeLDH electrocatalyst,with the Au intercalating between Fe_(3)O_(4)and LDH to form the sandwich structure.Cyclic voltammetry tests indicate that Au is responsible for the electrocatalytic oxidation of glucose.The characterizations of the electrochemical sensor for glucose detection indicate that Fe_(3)O_(4)@Au@Co FeLDH possesses high sensitivity of 6342μA m M^(-1)cm^(-2),with an extremely low oxidation potential of 0.82 V vs.RHE.Even with the high glucose concentration of 15 m M,the sensitivity remains at 4359μA m M^(-1)cm^(-2).Due to the broad linear detection range(0.0375 to 15.64 m M)and the low limit of detection(12.7μM),Fe_(3)O_(4)@Au@Co Fe-LDH is applicable towards practical application.Thanks to the sandwich structure,which confines the Au in between Fe_(3)O_(4)and Co Fe-LDH,the Fe_(3)O_(4)@Au@Co Fe-LDH glucose sensor shows high long-term stability and satisfactory selectivity.The successful synthesis of the sandwichstructured Fe_(3)O_(4)@Au@Co Fe-LDH provides a new conception for the design of highly sensitive and stable non-enzymatic glucose electrodes.
基金supported by the Aviation Science Fund of China(Nos.2015ZE52049,2015ZE521049)
文摘The so-called″X-cor sandwich structure″is a highly promising novel material as an alternative to honeycomb used in aircraft.Although much work has been conducted on the performance of the X-cor sandwich structure,the gap is still hardly bridged between experimental results and theoretical analyses.Therefore,a method has been innovated to establish semi-empirical formula for the prediction of compressive and shear moduli of X-cor sandwich structure composites,by combining theoretical analyses and experimental data.In addition,aprediction software was first developed based on the proposed method,of which the accuracy was verified through confirmatory experiments.This software can offer a direct reference or guide for engineers in structural designing.
文摘In the present study,experimental and numerical investigations were carried out to examine the behavior of sandwich panels with honeycomb cores.The high velocity impact tests were carried out using a compressed air gun.A sharp conical nosed projectile was impacted normally and with some offset distance(20 mm and 40 mm).The deformation,failure mode and energy dissipation characteristics were obtained for both kinds of loading.Moreover,the explicit solver was run in Abaqus to create the finite element model.The numerically obtained test results were compared with the experimental to check the accuracy of the modelling.The numerical result was further employed to obtain strain energy dissipation in each element by externally running user-defined code in Abaqus.Furthermore,the influence of inscribe circle diameter and cell wall and face sheet thickness on the energy dissipation,deformation and failure mode was examined.The result found that ballistic resistance and deformation were higher against offset impact compared to the normal impact loading.Sandwich panel impacted at 40 mm offset distance required 3 m/s and 1.9 m/s more velocity than 0 and 20 mm offset distance.Also,increasing the face sheet and wall thickness had a positive impact on the ballistic resistance in terms of a higher ballistic limit and energy absorption.However,inscribe circle diameter had a negative influence on the ballistic resistance.Also,the geometrical parameters of the sandwich structure had a significant influence on the energy dissipation in the different deformation directions.The energy dissipation in plastic work was highest for circumferential direction,regardless of impact condition followed by tangential,radial and axial directions.
基金National Natural Science Foundation of China(NSFC 31760187,31971595)Yunnan Provincial Natural Science Foundation(2017FB060)+1 种基金the“Ten-thousand Program”–Youth Talent Support Program and Yunnan Provincial Reserve Talents for Middle&Young Academic and Technical Leaders(2019HB026)the 111 Project(D21027).
文摘A cellular material in the form of 3-layered sandwich structure material was prepared via sole use of mechanical stirring without any use of a foaming agent,while Tween-80 was employed as a foam stabilizer via a developed in-situ mold casting.The resulting structure displayed a good appearance with no visual defects.The 3-layered composition of the sandwish structure,“nonporous resin layer-porous foam layer-nonporous resin layer”,was examined in terms of the microstructure,density&density distribution,pulverization ratio,mechanical strength,insulation and flame retardant performance.It was indicated from the results that the bonding between the resin layer and foam layer was tight,while the tensile rupture always occurred in the porous layer.Also,the density of the sandwich structure material was symmetrical with“saddle”distribution,and a uniform density for any given layer.The increase in the density at the interface layer provided a good interpretation for the tensile rupture never occurred at the interface.The brittleness resistance of the developed material was significantly improved,and the pulverization ratio was sharply decreased from 9.93%to 0.31%.The material acquired a thermal conductivity and limiting oxygen index(LOI)of 0.0241 W/m⋅K and 29.92%,respectively,indicating potential use of such materials broadly in fields of insulation and flame retardancy.
文摘This paper is a review of the past research of mechanical testing methods for natural fibre honeycomb sandwich structure as well as failure modes analysis at a microscopic level by using Scanning Electron Microscope (SEM). As the world is garnering attention towards renewable resources for environmental purposes, studies of natural fibre have been increasing as well as the application of natural fibre throughout various industries such as aerospace, automobiles, and construction sectors. This paper is started with brief information regarding the honeycomb sandwich structure, introduction to natural fibre, its applications as well as the factors affecting the performances of the structure. Next, the mechanical testing methods are listed out as well as the expected outcomes obtained from the respective testing. The mechanical properties are also identified by conducting lab tests according to the ASTM standard for sandwich and core structures. The microstructure of the deformed samples is then examined under Scanning Electron Microscope (SEM) by using different magnifications to study the failure mechanisms of the samples. The images obtained from the SEM test are analyzed by using fractography which will show the failure modes of the samples. This article is based on past research conducted by professional on the related topic.
基金supported by Shanghai Science and Technology Commission (No. 21ZR1415500)the National Nature Science Foundation of China (NSFC, Nos. 21907029, 22171085)。
文摘Substrate photopatterning has provided versatile applications in biomedical fields. Herein, an universal and efficient photoligation reaction has been used to prepare a patterned capture substrate for a sandwich SERS immunoassay. Photoirradiation induces mild and efficient immobilization of antibodies at the desired region of a gold surface, and the antibody-antigen interaction helps the substrate to capture the antigens in solution specifically. After exposing to SERS probes, i.e., the gold nanoparticles labelled with both antibodies and intrinsically strong Raman reporters, multiple quantitative SERS determination of antigens can be achieved with high sensitivity and specificity. The limit of detection can be as low as 10^(-12) mol/L for four kinds of cancer biomarkers, which provides a promising method for the construction of highly sensitive and high-throughput SERS detection chip and the application of in vitro diagnosis.
基金Project supported by the National Natural Science Foundation of China (Nos. 90816025, 10632060,and 10640150395)the National Basic Research Program of China (No. G2006CB601202)the Fund of State Key Laboratory of Explosion Science and Technology (No. KFJJ08-15)
文摘By introducing a dimensionless parameter to couple the two objectives, weight and radar absorbing performance, into a single objective function, a multi-objective optimization procedure for the radar absorbing sandwich structure （RASS） with a cellular core is proposed. The optimization models considered are one-side clamped sandwich panels with four kinds of cores subject to uniformly distributed loads. The average specular reflectivity calculated with the transfer matrix method and the periodic moment method is utilized to characterize the radar absorbing performance, while the mechanical constraints include the facesheet yielding, core shearing, and facesheet wrinkling. The optimization analysis indicates that the sandwich structure with a two-dimensional （2D） composite lattice core filled with ultra-lightweight sponge may be a better candidate of lightweight RASS than those with cellular foam or hexagonal honeycomb cores. The 2D Kagome lattice is found to outperform the square lattice with respect to radar absorbing.
