The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scatt...The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scattering have been extensively deployed in structural health monitoring due to their advantages,such as lightweight and ease of embedding.However,identifying the precise location of damage from the optical fiber signals remains a critical challenge.In this paper,a novel approach which namely Modified Sliding Window Principal Component Analysis(MSWPCA)was proposed to facilitate automatic damage identification and localization via distributed optical fiber sensors.The proposed method is able to extract signal characteristics interfered by measurement noise to improve the accuracy of damage detection.Specifically,we applied the MSWPCA method to monitor and analyze the debonding propagation process in honeycomb sandwich panel structures.Our findings demonstrate that the training model exhibits high precision in detecting the location and size of honeycomb debonding,thereby facilitating reliable and efficient online assessment of the structural health state.展开更多
How to ensure the safety of occupants has become a challenge for protective design of armored vehicles against intensive blast loadings.In this study,for armored vehicles subjected to shallow-buried explosions,an anal...How to ensure the safety of occupants has become a challenge for protective design of armored vehicles against intensive blast loadings.In this study,for armored vehicles subjected to shallow-buried explosions,an analytical model was established to characterize the dynamic performance of an all-metallic sandwich floorboard attached with a double mass-spring-damping system(mimicking seat and occupant),with the former consisting of a front face,a core and a rear face.For validation,numerical simulations with the method of finite elements(FE)were performed.Good agreement between analytical predictions and numerical results was achieved.The analytical model was then employed to quantify the effects of explosive mass,yield stress of material make,configurational parameters of sandwich panel,spring stiffness,and damping coefficient on dynamic response of the sandwich panel and double mass-spring-damping system.With increasing explosive mass and decreasing yield stress of material make,the peak displacements of rear face,seat and occupant were all found to increase.As core relative density was increased,these peak displacements also increased when the ratio of face thickness to core height was relatively small.Increasing the ratio of face thickness to core height led to increased peak accelerations of seat and occupant.The peak displacement of rear face was insensitive to the increase of either spring stiffness or damping coefficient,while the peak acceleration of occupant increased with increasing spring stiffness.Upon increasing the damping coefficient between the rear face and seat or that between the seat and occupant or both,the peak acceleration of occupant increased.With occupant safety duly considered,the proposed analytical model provides useful guidance for designing high-performance protective structures for armored vehicles subjected to intensive blast loadings.展开更多
Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores.The top and bottom facesheets were interconnected with truss cores.Both end...Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores.The top and bottom facesheets were interconnected with truss cores.Both ends of the truss cores were embedded into four layers of top and bottom facesheets.The mechanical properties of truss core sandwich panels were then investigated under out-of-plane and in-plane compression loadings to reveal the failure mechanisms of sandwich panels.Experimental results indicated that the mechanical behavior of sandwich structure under in-plane loading is dominated by the buckling and debonding of facesheets.展开更多
In this paper,an aluminum corrugated sandwich panel with triangular core under bending loads was investigated.Firstly,the equivalent material parameters of the triangular corrugated core layer,which could be considere...In this paper,an aluminum corrugated sandwich panel with triangular core under bending loads was investigated.Firstly,the equivalent material parameters of the triangular corrugated core layer,which could be considered as an orthotropic panel,were obtained by using Castigliano's theorem and equivalent homogeneous model.Secondly,contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory,and these equivalent material parameters were compared with finite element analysis solutions.Then,based on the Mindlin orthotropic plate theory,this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions,and parameters study and comparison by the finite element method were executed simultaneously.展开更多
An idea to develop a family of cellular cores for sandwich panels using a technology of prepreg folding is presented.Polar folded quadra-structures are regarded as a geometric basis for these cores whose standard frag...An idea to develop a family of cellular cores for sandwich panels using a technology of prepreg folding is presented.Polar folded quadra-structures are regarded as a geometric basis for these cores whose standard fragment has the fourth degree of axial symmetry.The classification of the polar structures are described and a method of various quadra-structure synthesis is developed.A possibility to provide high strength of the structure due to preservation of faces reinforcement pattern is presented.Arrangement of the plane core on a bi-curvature surface is also introduced.Besides,provision of isotropy of the core in two or three directions are described.Finally,examples of cellular folded cores manufactured from basalt reinforced plastic are demonstrated.展开更多
To investigate the temperature field and residual bearing capacity of the sandwich wall panels with GFRP skins and a wood-web core under a fire,three sandwich walls were tested.One of them was used for static load tes...To investigate the temperature field and residual bearing capacity of the sandwich wall panels with GFRP skins and a wood-web core under a fire,three sandwich walls were tested.One of them was used for static load test and the other two for the one-side fire tests.Besides,temperature probe points were set on the sandwich walls to obtain the temperature distribution.Meanwhile,the model of the sandwich wall was established in the finite element software by the method of core material stiffness equivalent.The temperature distribution and performance reduction of materials were also considered.The residual bearing capacity of specimens after fire exposure were simulated considering the effects of web spacing,wall panel thickness and fire exposure time.Because the sandwich wall panels were stressed by eccentric compression after a fire,the residual compressive strength of the wall panel after the fire can be calculated through the eccentric loading analysis.Compared with the numerical results,it can be concluded that the effectiveness of calculation method of residual bearing capacity after fire exposure was proved.展开更多
In this paper,an exact closed-form solution for a curved sandwich panel with two piezoelectric layers as actuator and sensor that are inserted in the top and bottom facings is presented.The core is made from functiona...In this paper,an exact closed-form solution for a curved sandwich panel with two piezoelectric layers as actuator and sensor that are inserted in the top and bottom facings is presented.The core is made from functionally graded(FG)material that has heterogeneous power-law distribution through the radial coordinate.It is assumed that the core is subjected to a magnetic field whereas the core is covered by two insulated composite layers.To determine the exact solution,first characteristic equations are derived for different material types in a polar coordinate system,namely,magneto-elastic,elastic,and electro-elastic for the FG,orthotropic,and piezoelectric materials,respectively.The displacement-based method is used instead of the stress-based method to derive a set of closed-form real-valued solutions for both real and complex roots.Based on the elasticity theory,exact solutions for the governing equations are determined layer-by-layer that are considerably more accurate than typical simplified theories.The accuracy of the presented method is compared and validated with the available literature and the finite element simulation.The effects of geometrical and material parameters such as FG index,angular span along with external conditions such as magnetic field,mechanical pressure,and electrical difference are investigated in detail through numerical examples.展开更多
This paper presents the significance analysis of a new type of hybrid composite sandwich wall panel which can be manufactured as modular panelised system. Two different types of natural fibers reinforced plastics (NFR...This paper presents the significance analysis of a new type of hybrid composite sandwich wall panel which can be manufactured as modular panelised system. Two different types of natural fibers reinforced plastics (NFRP) laminate were incorporated into the new sandwich panel as an intermediate layer. The significance analysis in this research has been carried out using analysis of variance (ANOVA). As the aim of the analysis is to select the most appropriate natural fiber composites for the intermediate layer, the experiments were arranged as a single factor experiment in which 3 levels of a factor have been examined. The factor refers to the type of intermediate layer used in the sandwich panel. The result of this study shows that the incorporation of intermediate layer has significantly enhanced the load carrying capacity of the sandwich panels.展开更多
Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, i...Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, including explosion cratering, scabbing of the backside, radial cracking induced failure and circumferential cracking induced failure. It also illustrates that the foam material sandwiched in the multi-layered media has an important effect on damage patterns. The phenomena encountered have been analyzed by the calculation with ALE method. Meanwhile, the optimal analysis of foam material thickness and position in the sandwich panel were performed in terms of experimental and numerical analysis. The proper thickness proportion of the soft layer is about 20% to the thickness of sandwich panel and the thickness of the upper hard layer and lower hard layer is in the ratio of 7 to 3 under the condition in this paper when the total thickness of soft layer remains constant.展开更多
In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order she...In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.展开更多
Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and...Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and deformation for concrete sandwich panels is obtained. These formulae can describe the slip distribution and account for its effect on deformation. In order to restrict the bound of formula, the formula of crack moment is obtained. The results of theoretical calculation are compared with those of tests and finite element methods. The comparison shows that the results of theoretical calculation are in accord with those of tests and finite element methods. So the theoretical calculation can be used to calculate slip and deformation of concrete sandwich panels in practical projects.展开更多
One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. A bonding assistant coat used below 850℃ was developed. It contained copper as basic ...One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. A bonding assistant coat used below 850℃ was developed. It contained copper as basic element and zinc as main alloy element. Other small elements and rare metals were added to decrease the melting point and to obtain a better clouding and high plasticity. Based on the theory of brazing and transient liquid diffusion welding, two carbon steel plates were rolled with small reduction by using self-made bonding assistant coat. Temperature, pressure and holding time are the main technology parameters for controlling the process of diffusion-rolling. The results show that the bonding strength is the greatest when the bonding temperature is 830℃, holding time is 3min and the reduction rate is 9%.展开更多
Sandwich panels are increasingly used in the aerospace industry in recent years. Aircrafts are always affected by the thermal and noise environment during their life in service. Analytical studies on the sound vibrati...Sandwich panels are increasingly used in the aerospace industry in recent years. Aircrafts are always affected by the thermal and noise environment during their life in service. Analytical studies on the sound vibration response of the sandwich panels with flexible core under thermal environments are performed in the paper. Governing equations are obtained by applying Hamilton 's principle with both anti-symmetric and symmetric motions taken into consideration. Natural frequencies,mode shape and critical temperature are acquired with thermal stresses considered. The forced vibration response and sound radiation are obtained based on the mode superposition principle and the Rayleigh integral. The model is validated compared with the results in literature. Natural frequencies for both anti-symmetric and symmetric motions decrease with temperature rise.Lower order flexural mode and higher-order dilatational mode are sensitive to the temperature change. Symmetric motion induces the anti-resonance frequencies move to the low frequency range. The peaks of sound vibration response remove to the low frequency range as the temperature rise and the amplitude of the peaks decrease due to the enhanced damping.The proposed model may serve as an effective guideline for the application of sandwich panels in thermal environments.展开更多
In this paper,the large deflection theory is adopted to analyse the geometrical nonlinear stability of a sandwich shallow cylindrical panel with orthoiropic surfaces.The critical point is determined and the postbuckli...In this paper,the large deflection theory is adopted to analyse the geometrical nonlinear stability of a sandwich shallow cylindrical panel with orthoiropic surfaces.The critical point is determined and the postbuckling behaviour of the panel is studied.展开更多
In the present work the dynamic characteristics of Multilayer Polyurethane foam glass/fiber composite sandwich panels have been determined through Experimental Investigations. Using a Multilayer Polyurethane foam sand...In the present work the dynamic characteristics of Multilayer Polyurethane foam glass/fiber composite sandwich panels have been determined through Experimental Investigations. Using a Multilayer Polyurethane foam sandwich panel with rectangular cross-section, the natural frequencies, mode shapes and the damping ratio of sandwich panels were evaluated. Three types of boundary conditions were simulated namely, C-F-F-F (Clamped Free-Free-Free), C-F-C-F (Clam-ped-Free-Clamped-Free), C-C-C-C-(Clamped-Clamped-Clamped-Clamped). Experimental modal tests were conducted on sandwich panels with available polyurethane foam of densities 56 kg/m3, 82 kg/m3and 289 kg/m3.The traditional “strike method” has been used to measure vibration properties. The modal characteristics of the specimens have been obtained by studying their impulse response. Each specimen has been subjected to impulses through a hard tipped hammer which is provided with a force transducer and the response has been measured through the accelerometer. The impulse and the response are processed through a computer aided FFT Analyzing test system in order to extract the modal parameters. Finite Element modeling was carried out treating the facing and core as orthotropic with different elastic constants as recommended in the literature. The experimental results were validated with FEA and were found to be in good agreement.The results obtained through modal test on multilayer sandwich panels are presented. They indicate a significant variation in the dynamic parameters in case of multilayer sandwich panels for the same core density as compared to a monolayer sandwich panel.展开更多
Composite sandwich structures are highly proven materials that provide high strength to weight ratio. However research works are still being carried out in the area of impact characteristics of sandwich composites. Th...Composite sandwich structures are highly proven materials that provide high strength to weight ratio. However research works are still being carried out in the area of impact characteristics of sandwich composites. This paper provides a better understanding on the effect of core density and core thickness of sandwich panels subject to low velocity drop test. Specific energy absorption capacity of sandwich panels is obtained and factors affecting the same are explored with facings made of woven glass fiber laminates and polyurethane foam core with three different densities of 70 Kg/m3, 100 Kg/m3, 200 Kg/m3.展开更多
Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic...Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.展开更多
In this study, various sandwich panel structures with different reticulate lattice core geometries were designed and then fabricated in titanium via the electron beam melting (EBM) process. Bending tests were performe...In this study, various sandwich panel structures with different reticulate lattice core geometries were designed and then fabricated in titanium via the electron beam melting (EBM) process. Bending tests were performed on the titanium samples, and mechanical properties such as modulus, bending strength, and energy absorption were evaluated. Different failure mechanisms were observed, and it was found that sandwich structures with auxetic cores exhibited more homogeneous deflection and bending compliance compared with other structures. It was also demonstrated that properties of auxetic sandwich structures can be tailored using different cell structure geometries to suit the needs of a given design application. Furthermore, it was found that other 3D cellular sandwich structures can also exhibit high stiffness and strength, which is desirable in potential applications.展开更多
A theoretical analysis is presented to predict the nonlinear thermo-structural response of metallic sandwich panels with truss cores under through-thickness gradient temperature field, which is a common service condit...A theoretical analysis is presented to predict the nonlinear thermo-structural response of metallic sandwich panels with truss cores under through-thickness gradient temperature field, which is a common service condition for metallic thermal protection system(TPS). The in-plane temperature distribution is assumed to be uniform, and through-thickness temperature field is determined by heat conduction. Two typical conditions are analyzed: nonlinear thermal bending in fixed inside surface temperature, and thermal post-buckling in fixed temperature difference between two surfaces. Temperature-dependent mechanical properties are considered, and gradient shear stiffness and bending stiffness due to non-uniform temperature is included. Results indicate that the temperature-dependent material properties obviously affect bending resistance;however, the effect is negligible on post-buckling behavior. Influences of geometric parameters on the thermo-structural behavior of the sandwich panel according to the present theoretical model are discussed.展开更多
基金supported by the National Key Research and Development Program of China(No.2018YFA0702800)the National Natural Science Foundation of China(No.12072056)supported by National Defense Fundamental Scientific Research Project(XXXX2018204BXXX).
文摘The safety and integrity requirements of aerospace composite structures necessitate real-time health monitoring throughout their service life.To this end,distributed optical fiber sensors utilizing back Rayleigh scattering have been extensively deployed in structural health monitoring due to their advantages,such as lightweight and ease of embedding.However,identifying the precise location of damage from the optical fiber signals remains a critical challenge.In this paper,a novel approach which namely Modified Sliding Window Principal Component Analysis(MSWPCA)was proposed to facilitate automatic damage identification and localization via distributed optical fiber sensors.The proposed method is able to extract signal characteristics interfered by measurement noise to improve the accuracy of damage detection.Specifically,we applied the MSWPCA method to monitor and analyze the debonding propagation process in honeycomb sandwich panel structures.Our findings demonstrate that the training model exhibits high precision in detecting the location and size of honeycomb debonding,thereby facilitating reliable and efficient online assessment of the structural health state.
基金supported by the National Natural Science Foundation of China(Grant Nos.11972185 and 12002156)the Research Fund of State Key Laboratory of Mechanics and Control of Mechanical Structures(Grant No.MCMS-I-0222K01)+1 种基金the Fund of Prospective Layout of Scientific Research for NUAAthe Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)。
文摘How to ensure the safety of occupants has become a challenge for protective design of armored vehicles against intensive blast loadings.In this study,for armored vehicles subjected to shallow-buried explosions,an analytical model was established to characterize the dynamic performance of an all-metallic sandwich floorboard attached with a double mass-spring-damping system(mimicking seat and occupant),with the former consisting of a front face,a core and a rear face.For validation,numerical simulations with the method of finite elements(FE)were performed.Good agreement between analytical predictions and numerical results was achieved.The analytical model was then employed to quantify the effects of explosive mass,yield stress of material make,configurational parameters of sandwich panel,spring stiffness,and damping coefficient on dynamic response of the sandwich panel and double mass-spring-damping system.With increasing explosive mass and decreasing yield stress of material make,the peak displacements of rear face,seat and occupant were all found to increase.As core relative density was increased,these peak displacements also increased when the ratio of face thickness to core height was relatively small.Increasing the ratio of face thickness to core height led to increased peak accelerations of seat and occupant.The peak displacement of rear face was insensitive to the increase of either spring stiffness or damping coefficient,while the peak acceleration of occupant increased with increasing spring stiffness.Upon increasing the damping coefficient between the rear face and seat or that between the seat and occupant or both,the peak acceleration of occupant increased.With occupant safety duly considered,the proposed analytical model provides useful guidance for designing high-performance protective structures for armored vehicles subjected to intensive blast loadings.
基金supported by the National Science Foundation of China under grant Nos.90816024 and 10872059the Major State Basic Research Development Program of China (973 Program) under grant No.2006CB601206+1 种基金the Program of Excellent Team inHarbin Institute of Technologythe Program for New Century Excellent Talents in Universityunder grant No.NCET-08-0152
文摘Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores.The top and bottom facesheets were interconnected with truss cores.Both ends of the truss cores were embedded into four layers of top and bottom facesheets.The mechanical properties of truss core sandwich panels were then investigated under out-of-plane and in-plane compression loadings to reveal the failure mechanisms of sandwich panels.Experimental results indicated that the mechanical behavior of sandwich structure under in-plane loading is dominated by the buckling and debonding of facesheets.
基金the National Natural Science Foundation of China(Grant 11572122)the Scientific Research Foundation of Huaihua University(Grant HHUY2017-02)+2 种基金111 Project(Grant B16015)Stake Key Laboratory of Mechanical Structural Strength and Vibration(Grant SV2017-KF-20)Joint Centre for Intelligent New Energy Vehicle.
文摘In this paper,an aluminum corrugated sandwich panel with triangular core under bending loads was investigated.Firstly,the equivalent material parameters of the triangular corrugated core layer,which could be considered as an orthotropic panel,were obtained by using Castigliano's theorem and equivalent homogeneous model.Secondly,contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory,and these equivalent material parameters were compared with finite element analysis solutions.Then,based on the Mindlin orthotropic plate theory,this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions,and parameters study and comparison by the finite element method were executed simultaneously.
基金supported by the Ministry of Education and Science of Russian Federation (No.RFMEFI57414X0078)
文摘An idea to develop a family of cellular cores for sandwich panels using a technology of prepreg folding is presented.Polar folded quadra-structures are regarded as a geometric basis for these cores whose standard fragment has the fourth degree of axial symmetry.The classification of the polar structures are described and a method of various quadra-structure synthesis is developed.A possibility to provide high strength of the structure due to preservation of faces reinforcement pattern is presented.Arrangement of the plane core on a bi-curvature surface is also introduced.Besides,provision of isotropy of the core in two or three directions are described.Finally,examples of cellular folded cores manufactured from basalt reinforced plastic are demonstrated.
文摘To investigate the temperature field and residual bearing capacity of the sandwich wall panels with GFRP skins and a wood-web core under a fire,three sandwich walls were tested.One of them was used for static load test and the other two for the one-side fire tests.Besides,temperature probe points were set on the sandwich walls to obtain the temperature distribution.Meanwhile,the model of the sandwich wall was established in the finite element software by the method of core material stiffness equivalent.The temperature distribution and performance reduction of materials were also considered.The residual bearing capacity of specimens after fire exposure were simulated considering the effects of web spacing,wall panel thickness and fire exposure time.Because the sandwich wall panels were stressed by eccentric compression after a fire,the residual compressive strength of the wall panel after the fire can be calculated through the eccentric loading analysis.Compared with the numerical results,it can be concluded that the effectiveness of calculation method of residual bearing capacity after fire exposure was proved.
文摘In this paper,an exact closed-form solution for a curved sandwich panel with two piezoelectric layers as actuator and sensor that are inserted in the top and bottom facings is presented.The core is made from functionally graded(FG)material that has heterogeneous power-law distribution through the radial coordinate.It is assumed that the core is subjected to a magnetic field whereas the core is covered by two insulated composite layers.To determine the exact solution,first characteristic equations are derived for different material types in a polar coordinate system,namely,magneto-elastic,elastic,and electro-elastic for the FG,orthotropic,and piezoelectric materials,respectively.The displacement-based method is used instead of the stress-based method to derive a set of closed-form real-valued solutions for both real and complex roots.Based on the elasticity theory,exact solutions for the governing equations are determined layer-by-layer that are considerably more accurate than typical simplified theories.The accuracy of the presented method is compared and validated with the available literature and the finite element simulation.The effects of geometrical and material parameters such as FG index,angular span along with external conditions such as magnetic field,mechanical pressure,and electrical difference are investigated in detail through numerical examples.
文摘This paper presents the significance analysis of a new type of hybrid composite sandwich wall panel which can be manufactured as modular panelised system. Two different types of natural fibers reinforced plastics (NFRP) laminate were incorporated into the new sandwich panel as an intermediate layer. The significance analysis in this research has been carried out using analysis of variance (ANOVA). As the aim of the analysis is to select the most appropriate natural fiber composites for the intermediate layer, the experiments were arranged as a single factor experiment in which 3 levels of a factor have been examined. The factor refers to the type of intermediate layer used in the sandwich panel. The result of this study shows that the incorporation of intermediate layer has significantly enhanced the load carrying capacity of the sandwich panels.
文摘Surface contact explosion experiments have been performed for the study of dynamic response of the hard-soft-hard sandwich panel under blast loading. Experimental results have shown that there are four damage modes, including explosion cratering, scabbing of the backside, radial cracking induced failure and circumferential cracking induced failure. It also illustrates that the foam material sandwiched in the multi-layered media has an important effect on damage patterns. The phenomena encountered have been analyzed by the calculation with ALE method. Meanwhile, the optimal analysis of foam material thickness and position in the sandwich panel were performed in terms of experimental and numerical analysis. The proper thickness proportion of the soft layer is about 20% to the thickness of sandwich panel and the thickness of the upper hard layer and lower hard layer is in the ratio of 7 to 3 under the condition in this paper when the total thickness of soft layer remains constant.
基金the Iranian Nanotechnology Development Committee for their financial supportthe University of Kashan for supporting this work (No. 891238/11)。
文摘In this paper,the stresses and buckling behaviors of a thick-walled mi-cro sandwich panel with a flexible foam core and carbon nanotube reinforced composite(CNTRC)face sheets are considered based on the high-order shear deformation theory(HSDT)and the modified couple stress theory(MCST).The governing equations of equi-librium are obtained based on the total potential energy principle.The effects of various parameters such as the aspect ratio,elastic foundation,temperature changes,and volume fraction of the canbon nanotubes(CNTs)on the critical buckling loads,normal stress,shear stress,and deflection of the thick-walled micro cylindrical sandwich panel consider-ing different distributions of CNTs are examined.The results are compared and validated with other studies,and showing an excellent compatibility.CNTs have become very use-ful and common candidates in sandwich structures,and they have been extensively used in many applications including nanotechnology,aerospace,and micro-structures.This paper also extends further applications of reinforced sandwich panels by providing the modified equations and formulae.
基金Supported by Natural Science Foundation of Tianjin (No.06YFJMJC05800)
文摘Slip and deformation of concrete sandwich panels under uniformly distributed loads is concerned. The effect of slip on the deformation of concrete sandwich panels are studied,and the analytical expressions of slip and deformation for concrete sandwich panels is obtained. These formulae can describe the slip distribution and account for its effect on deformation. In order to restrict the bound of formula, the formula of crack moment is obtained. The results of theoretical calculation are compared with those of tests and finite element methods. The comparison shows that the results of theoretical calculation are in accord with those of tests and finite element methods. So the theoretical calculation can be used to calculate slip and deformation of concrete sandwich panels in practical projects.
文摘One of the key problems by diffusion-rolling bonding with small reduction for carbon steel plates is the bonding assistant coat. A bonding assistant coat used below 850℃ was developed. It contained copper as basic element and zinc as main alloy element. Other small elements and rare metals were added to decrease the melting point and to obtain a better clouding and high plasticity. Based on the theory of brazing and transient liquid diffusion welding, two carbon steel plates were rolled with small reduction by using self-made bonding assistant coat. Temperature, pressure and holding time are the main technology parameters for controlling the process of diffusion-rolling. The results show that the bonding strength is the greatest when the bonding temperature is 830℃, holding time is 3min and the reduction rate is 9%.
基金Sponsored by the National Natural Science Foundation of China(Grant No.11372084)
文摘Sandwich panels are increasingly used in the aerospace industry in recent years. Aircrafts are always affected by the thermal and noise environment during their life in service. Analytical studies on the sound vibration response of the sandwich panels with flexible core under thermal environments are performed in the paper. Governing equations are obtained by applying Hamilton 's principle with both anti-symmetric and symmetric motions taken into consideration. Natural frequencies,mode shape and critical temperature are acquired with thermal stresses considered. The forced vibration response and sound radiation are obtained based on the mode superposition principle and the Rayleigh integral. The model is validated compared with the results in literature. Natural frequencies for both anti-symmetric and symmetric motions decrease with temperature rise.Lower order flexural mode and higher-order dilatational mode are sensitive to the temperature change. Symmetric motion induces the anti-resonance frequencies move to the low frequency range. The peaks of sound vibration response remove to the low frequency range as the temperature rise and the amplitude of the peaks decrease due to the enhanced damping.The proposed model may serve as an effective guideline for the application of sandwich panels in thermal environments.
文摘In this paper,the large deflection theory is adopted to analyse the geometrical nonlinear stability of a sandwich shallow cylindrical panel with orthoiropic surfaces.The critical point is determined and the postbuckling behaviour of the panel is studied.
文摘In the present work the dynamic characteristics of Multilayer Polyurethane foam glass/fiber composite sandwich panels have been determined through Experimental Investigations. Using a Multilayer Polyurethane foam sandwich panel with rectangular cross-section, the natural frequencies, mode shapes and the damping ratio of sandwich panels were evaluated. Three types of boundary conditions were simulated namely, C-F-F-F (Clamped Free-Free-Free), C-F-C-F (Clam-ped-Free-Clamped-Free), C-C-C-C-(Clamped-Clamped-Clamped-Clamped). Experimental modal tests were conducted on sandwich panels with available polyurethane foam of densities 56 kg/m3, 82 kg/m3and 289 kg/m3.The traditional “strike method” has been used to measure vibration properties. The modal characteristics of the specimens have been obtained by studying their impulse response. Each specimen has been subjected to impulses through a hard tipped hammer which is provided with a force transducer and the response has been measured through the accelerometer. The impulse and the response are processed through a computer aided FFT Analyzing test system in order to extract the modal parameters. Finite Element modeling was carried out treating the facing and core as orthotropic with different elastic constants as recommended in the literature. The experimental results were validated with FEA and were found to be in good agreement.The results obtained through modal test on multilayer sandwich panels are presented. They indicate a significant variation in the dynamic parameters in case of multilayer sandwich panels for the same core density as compared to a monolayer sandwich panel.
文摘Composite sandwich structures are highly proven materials that provide high strength to weight ratio. However research works are still being carried out in the area of impact characteristics of sandwich composites. This paper provides a better understanding on the effect of core density and core thickness of sandwich panels subject to low velocity drop test. Specific energy absorption capacity of sandwich panels is obtained and factors affecting the same are explored with facings made of woven glass fiber laminates and polyurethane foam core with three different densities of 70 Kg/m3, 100 Kg/m3, 200 Kg/m3.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51779110 and 51809122)the Natural Science Foundation of Jiangsu Province(Grant No.BK20191461)the Six Talent Peaks Project in Jiangsu Province(Grant No.KTHY-064).
文摘Sandwich panel is commonly used in ship and marine engineering equipment,such as side structure and superstructure deck of a ship,which is of good anti-explosion performance.This paper addresses a study on the dynamic response of the U-typed sandwich panel under explosion load through the numerical simulation and theoretical methods.Based on the orthotropic plate theory,the U-typed sandwich panel is simplified and transformed into a single degree of freedom(SDOF)spring system,the equivalent motion equation of the SDOF system and the expression of triangular explosion load function are established based on the SDOF theory,and the maximum response spectrum of the SDOF system is obtained.Then,the response of the equivalent SDOF system of the U-typed sandwich panel under explosion load is analyzed,and the theoretical results match well with the numerical simulation results,which verifies the accuracy of the theoretical method proposed in this paper.The theoretical method proposed in this paper could have good engineering applications for the structural anti-explosion design,and provide a reference for the evaluation of the anti-explosion performance of ship and offshore platform structures.
文摘In this study, various sandwich panel structures with different reticulate lattice core geometries were designed and then fabricated in titanium via the electron beam melting (EBM) process. Bending tests were performed on the titanium samples, and mechanical properties such as modulus, bending strength, and energy absorption were evaluated. Different failure mechanisms were observed, and it was found that sandwich structures with auxetic cores exhibited more homogeneous deflection and bending compliance compared with other structures. It was also demonstrated that properties of auxetic sandwich structures can be tailored using different cell structure geometries to suit the needs of a given design application. Furthermore, it was found that other 3D cellular sandwich structures can also exhibit high stiffness and strength, which is desirable in potential applications.
基金The financial support from the National Natural Science Foundation of China (91016025, 11472276, 11602271, and 11332011)the Defense Industrial Technology Development Program of China (JCKY2016130B009)
文摘A theoretical analysis is presented to predict the nonlinear thermo-structural response of metallic sandwich panels with truss cores under through-thickness gradient temperature field, which is a common service condition for metallic thermal protection system(TPS). The in-plane temperature distribution is assumed to be uniform, and through-thickness temperature field is determined by heat conduction. Two typical conditions are analyzed: nonlinear thermal bending in fixed inside surface temperature, and thermal post-buckling in fixed temperature difference between two surfaces. Temperature-dependent mechanical properties are considered, and gradient shear stiffness and bending stiffness due to non-uniform temperature is included. Results indicate that the temperature-dependent material properties obviously affect bending resistance;however, the effect is negligible on post-buckling behavior. Influences of geometric parameters on the thermo-structural behavior of the sandwich panel according to the present theoretical model are discussed.
