The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigate...The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigated.The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity.For the layer analysis,the high-order shear deformation theory(HSDT)and Frostig's second model for the displacement fields of the core layer are used.The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time.In order to validate the analytical method,the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI.Finite element(FE)simulations are conducted by means of the ABAQUS software.The effects of the parameters such as foam modulus,layer material,fiber angle,impactor mass,and its velocity on the generated voltage are reviewed.展开更多
The present study explored the influence of axial gradation of viscoelastic materials on the dynamic response of the sandwich beam for structural applications.The finite element(FE)formulations are used to model and i...The present study explored the influence of axial gradation of viscoelastic materials on the dynamic response of the sandwich beam for structural applications.The finite element(FE)formulations are used to model and investigate dynamic response of the sandwich beam.The classical beam theory is used to develop the FE formulations and Lagrange's approach is considered to obtain the equations of motion(EOM).FE code is developed and validated with the existing literature and also conducted the convergence study for the developed FE method.Further,the influence of different viscoelastic materials and boundary conditions on the dynamic response of the sandwich beam is investigated.Four different axial gradation configurations of viscoelastic materials are considered for the present work to explore the influence on natural frequency,loss factor and frequency response of the sandwich beam.The modeled axial gradation of viscoelastic material has displayed a considerable impact on the peak vibrational amplitude response of the sandwich beam for all the boundary conditions and these configurations improved the damping capabilities at different configurations for the structural applications.展开更多
Light weight high performance sandwich composite structures have been used extensively in various load bearing applications.Experiments have shown that the indentation significantly reduces the load bearing capacity o...Light weight high performance sandwich composite structures have been used extensively in various load bearing applications.Experiments have shown that the indentation significantly reduces the load bearing capacity of sandwiched beams.In this paper,the indentation behavior of foam core sandwich beams without considering the globally axial and flexural deformation was analyzed using the principle of virtual velocities.A concisely theoretical solution of loading capacity and denting profile was presented.The denting load was found to be proportional to the square root of the denting depth.A finite element model was established to verify the prediction of the model.The load-indentation curves and the profiles of the dented zone predicted by theoretical model and numerical simulation are in good agreement.展开更多
The dynamic response of elastic-plastic ideal sandwich beams is investigated. The plastic deformation is interpreted as a kind of general loads in the elastic beams, while the moving interfaces between elastic and pla...The dynamic response of elastic-plastic ideal sandwich beams is investigated. The plastic deformation is interpreted as a kind of general loads in the elastic beams, while the moving interfaces between elastic and plastic regions are treated as external restraint conditions. Particularly, the dynamic response of a cantilever beam is investigated using the classical method by means of the superposition of the vibration modes of elastic beams. The numerical results show that, compared with the rigid-plastic solutions, the dynamic be- havior of elastoplastic beam exhibits complex response modes. In some cases, elastic deformation has very important effects on the response mode of the beam, so it should not be ignored.展开更多
Piezoelectric bender elements are widely used as electromechanical sensors and actuators, An analytical sandwich beam model for piezoelectric bender elements was developed based on the first-order shear deformation th...Piezoelectric bender elements are widely used as electromechanical sensors and actuators, An analytical sandwich beam model for piezoelectric bender elements was developed based on the first-order shear deformation theory (FSDT), which assumes a single rotation angle for the whole cross-section and a quadratic distribution function for coupled electric potential in piezoelectric layers, and corrects the effect of transverse shear strain on the electric displacement integration. Free vibration analysis of simplysupported bender elements was carried out and the numerical results showed that, solutions of the present model for various thickness-to-length ratios are compared well with the exact two-dimensional solutions, which presents an efficient and accurate model for analyzing dynamic electromechanical responses of bender elements.展开更多
A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates.Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the i...A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates.Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the intensity of the magnetic field and excitation frequencies.The results show that the sandwich beams with MR elastomers cores have the capabilities of shifting natural frequencies and the vibration amplitudes decrease with the variation of the intensity of external magnetic field.展开更多
An improved analytical model is developed to predict the dynamic response of clamped lightweight sandwich beams with cellular cores subjected to shock loading over the entire span.The clamped face sheets are simplifie...An improved analytical model is developed to predict the dynamic response of clamped lightweight sandwich beams with cellular cores subjected to shock loading over the entire span.The clamped face sheets are simplified as a single-degree-of-freedom(SDOF)system,and the core is idealized using the rigid-perfectly-plastic-locking(RPPL)model.Reflection of incident shock wave is considered by incorporating the bending/stretching resistance of the front face sheet and compaction of the core.The model is validated with existing analytical predictions and FE simulation results,with good agreement achieved.Compared with existing analytical models,the proposed model exhibits superiority in two aspects:the deformation resistance of front face sheet during shock wave reflection is taken into account;the effect of pulse shape is considered.The practical application range of the proposed model is therefore wider.展开更多
The original purpose of FGMs was the development of super resistant materials for propulsion systems. In the present work, numerical and experimental techniques are used to investigate the dynamic behavior of generall...The original purpose of FGMs was the development of super resistant materials for propulsion systems. In the present work, numerical and experimental techniques are used to investigate the dynamic behavior of generally laminated composited beams. In the numerical analysis, the laminated beam is modeled using the commercial finite element software ANSYS. In the experimental study the core and face materials of sandwich beam specimens are nylon/epoxy FGMs and pure epoxy laminates respectively. The dynamic behavior of the sandwich composite beam specimens with different fiber orientation was carried out using two dynamic excitation techniques, harmonic using harmonic response and impulse using hammer. The specimens were prepared in the following configurations, different orientation angles, different layers, and different thickness. The results reveal that the natural frequencies of sandwich beam were affected directly by the face materials. The natural frequency decreases with increasing fiber orientations of the nylon/epoxy face laminates. Increasing the thickness increases natural frequencies. This study concluded that it is useful for the designers to select the fiber orientation angle to shift the natural frequencies as desired or to control the vibration level.展开更多
The equation of motion of sandwich beam with pyramidal lattice core in the supersonic flow considering geometric nonlinearity is formulated using Hamilton's principle. The piston theory is used to evaluate aerodynami...The equation of motion of sandwich beam with pyramidal lattice core in the supersonic flow considering geometric nonlinearity is formulated using Hamilton's principle. The piston theory is used to evaluate aerodynamic pressure. The structural aeroelastic properties are analyzed using frequency- and time-domain methods, and some interesting phenomena are observed. It is noted that the flutter of sandwich beam occurs under the coupling effect of low order modes. The critical flutter aerodynamic pressure of the sandwich beam is higher than that of the isotropic beam with the same weight, length and width. The influence of inclination angle of core truss on flutter characteristic is analyzed.展开更多
This work deals with the active control of the vibrations of mechanical structures incorporating magnetorheological elastomer. The damping coefficient and shear modulus of the elastomer increase when exposed to a magn...This work deals with the active control of the vibrations of mechanical structures incorporating magnetorheological elastomer. The damping coefficient and shear modulus of the elastomer increase when exposed to a magnetic field. Compared with the vibration control where the elastomer is permanently exposed to a magnetic field, the control of this process through time reduces vibrations more effectively. The experimental study for the vibrations of a sandwich beam filled with an elastomer is conducted, followed by a numerical study using the Abaqus code. The vibration damping is found to be dependent on the loading rate of micro-size ferromagnetic particles in the elastomer.展开更多
As a novel vibration absorber,Nitinol-steel wire rope(NiTi-ST)has rarely been studied on vibration suppression for lattice sandwich beams in supersonic airflow.In this paper,NiTi-ST with nonlinear stiffness and hyster...As a novel vibration absorber,Nitinol-steel wire rope(NiTi-ST)has rarely been studied on vibration suppression for lattice sandwich beams in supersonic airflow.In this paper,NiTi-ST with nonlinear stiffness and hysteretic damping is embedded in a lattice sandwich beam to control the beam's vibration.The nonlinear restoring and hysteretic damping force of NiTi-ST are treated as polynomials.The dynamic equation is established based on Hamilton's principle.The amplitude responses of the beam with different NiTi-ST configurations are calculated.The vibration-suppression effects and energy dissipation of lattice sandwich beam with different NiTi-ST configurations under different air velocities are also compared.The frequency-domain and time-domain methods are used to analyze the structural aeroelastic properties.Simulation results show that the use of NiTi-ST can significantly suppress excessive vibration of a lattice sandwich beam in supersonic airflow.展开更多
Magnetorheological fluid(MRF)sandwich beams belong to a class of adaptive beams that consists of MRF sandwiched between two or more face layers and have a great prospective for use in semi-active control of beam vibra...Magnetorheological fluid(MRF)sandwich beams belong to a class of adaptive beams that consists of MRF sandwiched between two or more face layers and have a great prospective for use in semi-active control of beam vibrations due to their superior vibration suppression capabilities.The composition of MRF has a strong influence on the MRF properties and hence affects the vibration characteristics of the beam.In this work,six MRF samples(MRFs)composed of combination of two particle sizes and three weight fractions of carbonyl iron pow-der(CIP)were prepared and their viscoelastic properties were measured.The MRFs were used to fabricate different MRF core sandwich beams.Additionally,a sandwich beam with commer-cially available MRF 132DG fluid as core was fabricated.The modal parameters of the cantilever MRF sandwich beams were determined at different magnetic fields.Further,sinusoidal sweep excitation tests were performed on these beams at different magnetic fields to investigate their vibration suppres-sion behavior.MRF having larger particle size and higher weight fraction of CIP resulted in higher damping ratio and vibration suppression.Finally,optimal particle size and weight fraction of CIP were determined based on the maximization of damping ratio and minimization of weight of MRF.展开更多
Experiments were conducted to investigate the deformation of cantilever sandwich beams with pyramidal truss cores subjected to impact by a projectile at their tips.A new technique was employed to the fabrication of sa...Experiments were conducted to investigate the deformation of cantilever sandwich beams with pyramidal truss cores subjected to impact by a projectile at their tips.A new technique was employed to the fabrication of sandwich beams with pyramidal truss cores.For a better observation of large deformation of specimens during impact process,a high-speed digital video camera was successfully used to capture the instant shapes of the deformed beams.A projectile collection device was designed and installed to avoid the projectile flying away from the beam tips after impact and thus the kinetic energy imparted to the beams was measurable.The experiments show that the sandwich beams have a superior shock resistance compared to the monolithic beams of the same material and mass.Further,finite element simulations were performed to gain insight into the deformations and plastic energy absorptions in the sandwich beams.展开更多
The sandwich structure is of great interest because of its advantage of combining light weight and high flexural stiffness. Many previous researchers have studied the failure modes in sandwich structures and the effec...The sandwich structure is of great interest because of its advantage of combining light weight and high flexural stiffness. Many previous researchers have studied the failure modes in sandwich structures and the effects on the load capacity caused by the change of the constituent materials’ properties. In this research, by applying Finite Element Analysis (FEA) method, we simulated a cantilever beam composed of a sandwich structure in Abaqus, to find out the preferred design principles that help decrease the stress and displacement in the beam when applied a uniform load. We also determined the effect of the core geometry on decreasing the displacement and the stress in the beam.展开更多
This paper is focused on the post-buckling behavior of the fixed laminated composite beams with effects of axial compression force and the shear deformation.The analytical solutions are established for the original co...This paper is focused on the post-buckling behavior of the fixed laminated composite beams with effects of axial compression force and the shear deformation.The analytical solutions are established for the original control equations(that is not simplified)by applying the Maclaurin series expansion,Chebyshev polynomials,the harmonic balance method and the Newton’s method.The validity of the present method is verified via comparing the analytical approximate solutions with the numerical ones which are obtained by the shooting method.The present third analytical approximate solutions can give excellent agreement with the numerical solutions for a wide range of the deformation amplitudes.What’s more,the effect of shear deformation on the post-bucking configuration of the sandwich beam is also proposed.It can be found that the shear angle has a great influence on the post-buckling load of composite beams.Therefore,the model simplifying the shear formation term as small quantity is not accurate for the case of sandwich beam with soft core.展开更多
文摘The dynamic responses and generated voltage in a curved sandwich beam with glass reinforced laminate(GRL)layers and a pliable core in the presence of a piezoelectric layer under low-velocity impact(LVI)are investigated.The current study aims to carry out a dynamic analysis on the sandwich beam when the impactor hits the top face sheet with an initial velocity.For the layer analysis,the high-order shear deformation theory(HSDT)and Frostig's second model for the displacement fields of the core layer are used.The classical non-adhesive elastic contact theory and Hunter's principle are used to calculate the dynamic responses in terms of time.In order to validate the analytical method,the outcomes of the current investigation are compared with those gained by the experimental tests carried out by other researchers for a rectangular composite plate subject to the LVI.Finite element(FE)simulations are conducted by means of the ABAQUS software.The effects of the parameters such as foam modulus,layer material,fiber angle,impactor mass,and its velocity on the generated voltage are reviewed.
基金support from the Department of Science and Technology (DST)file no.ECR/2016/001448 titled“Experimental Investigation of Passive,Semi-active and Active vibration control of Composite Sandwich Structure”funded by Science and Engineering Research Board,Government of India。
文摘The present study explored the influence of axial gradation of viscoelastic materials on the dynamic response of the sandwich beam for structural applications.The finite element(FE)formulations are used to model and investigate dynamic response of the sandwich beam.The classical beam theory is used to develop the FE formulations and Lagrange's approach is considered to obtain the equations of motion(EOM).FE code is developed and validated with the existing literature and also conducted the convergence study for the developed FE method.Further,the influence of different viscoelastic materials and boundary conditions on the dynamic response of the sandwich beam is investigated.Four different axial gradation configurations of viscoelastic materials are considered for the present work to explore the influence on natural frequency,loss factor and frequency response of the sandwich beam.The modeled axial gradation of viscoelastic material has displayed a considerable impact on the peak vibrational amplitude response of the sandwich beam for all the boundary conditions and these configurations improved the damping capabilities at different configurations for the structural applications.
基金supported by the National Natural Science Foundation of China(90916026,10532020 and 10672156)the Chinese Academy of Sciences(KJCX2-EW-L03)
文摘Light weight high performance sandwich composite structures have been used extensively in various load bearing applications.Experiments have shown that the indentation significantly reduces the load bearing capacity of sandwiched beams.In this paper,the indentation behavior of foam core sandwich beams without considering the globally axial and flexural deformation was analyzed using the principle of virtual velocities.A concisely theoretical solution of loading capacity and denting profile was presented.The denting load was found to be proportional to the square root of the denting depth.A finite element model was established to verify the prediction of the model.The load-indentation curves and the profiles of the dented zone predicted by theoretical model and numerical simulation are in good agreement.
文摘The dynamic response of elastic-plastic ideal sandwich beams is investigated. The plastic deformation is interpreted as a kind of general loads in the elastic beams, while the moving interfaces between elastic and plastic regions are treated as external restraint conditions. Particularly, the dynamic response of a cantilever beam is investigated using the classical method by means of the superposition of the vibration modes of elastic beams. The numerical results show that, compared with the rigid-plastic solutions, the dynamic be- havior of elastoplastic beam exhibits complex response modes. In some cases, elastic deformation has very important effects on the response mode of the beam, so it should not be ignored.
基金the National Natural Science Foundation of China(No.10472102)theNational Basic Research Program of China(No.2007CB714200)
文摘Piezoelectric bender elements are widely used as electromechanical sensors and actuators, An analytical sandwich beam model for piezoelectric bender elements was developed based on the first-order shear deformation theory (FSDT), which assumes a single rotation angle for the whole cross-section and a quadratic distribution function for coupled electric potential in piezoelectric layers, and corrects the effect of transverse shear strain on the electric displacement integration. Free vibration analysis of simplysupported bender elements was carried out and the numerical results showed that, solutions of the present model for various thickness-to-length ratios are compared well with the exact two-dimensional solutions, which presents an efficient and accurate model for analyzing dynamic electromechanical responses of bender elements.
基金Project(10602033) supported by the National Natural Science Foundation of ChinaProject(07B012) supported by Scientific Research Fund of Education Department of Hunan ProvinceProject(VSN-2007-01) supported the Research Fund of State Key Laboratory of Mechanical System and Vibration
文摘A sandwich beam specimen was fabricated by treating with MR elastomers between two thin aluminum face-plates.Experiment was carried out to investigate the vibration responses of the sandwich beam with respect to the intensity of the magnetic field and excitation frequencies.The results show that the sandwich beams with MR elastomers cores have the capabilities of shifting natural frequencies and the vibration amplitudes decrease with the variation of the intensity of external magnetic field.
基金supported by the National Natural Science Foundation of China (Grants 11972185, 11802221, 11472208, and 11472209)the China Postdoctoral Science Foundation (Grant 2016M600782)+2 种基金the Postdoctoral Scientific Research Project of Shaanxi Province (Grant 2016BSHYDZZ18)the Zhejiang Provincial Natural Science Foundation of China (Grant LGG18A020001)the Natural Science Basic Research Plan in Shaanxi Province of China (Grant 2018JQ1078)
文摘An improved analytical model is developed to predict the dynamic response of clamped lightweight sandwich beams with cellular cores subjected to shock loading over the entire span.The clamped face sheets are simplified as a single-degree-of-freedom(SDOF)system,and the core is idealized using the rigid-perfectly-plastic-locking(RPPL)model.Reflection of incident shock wave is considered by incorporating the bending/stretching resistance of the front face sheet and compaction of the core.The model is validated with existing analytical predictions and FE simulation results,with good agreement achieved.Compared with existing analytical models,the proposed model exhibits superiority in two aspects:the deformation resistance of front face sheet during shock wave reflection is taken into account;the effect of pulse shape is considered.The practical application range of the proposed model is therefore wider.
文摘The original purpose of FGMs was the development of super resistant materials for propulsion systems. In the present work, numerical and experimental techniques are used to investigate the dynamic behavior of generally laminated composited beams. In the numerical analysis, the laminated beam is modeled using the commercial finite element software ANSYS. In the experimental study the core and face materials of sandwich beam specimens are nylon/epoxy FGMs and pure epoxy laminates respectively. The dynamic behavior of the sandwich composite beam specimens with different fiber orientation was carried out using two dynamic excitation techniques, harmonic using harmonic response and impulse using hammer. The specimens were prepared in the following configurations, different orientation angles, different layers, and different thickness. The results reveal that the natural frequencies of sandwich beam were affected directly by the face materials. The natural frequency decreases with increasing fiber orientations of the nylon/epoxy face laminates. Increasing the thickness increases natural frequencies. This study concluded that it is useful for the designers to select the fiber orientation angle to shift the natural frequencies as desired or to control the vibration level.
基金Project supported by the National Natural Science Foundation of China(Nos.11572007 and 11172084)
文摘The equation of motion of sandwich beam with pyramidal lattice core in the supersonic flow considering geometric nonlinearity is formulated using Hamilton's principle. The piston theory is used to evaluate aerodynamic pressure. The structural aeroelastic properties are analyzed using frequency- and time-domain methods, and some interesting phenomena are observed. It is noted that the flutter of sandwich beam occurs under the coupling effect of low order modes. The critical flutter aerodynamic pressure of the sandwich beam is higher than that of the isotropic beam with the same weight, length and width. The influence of inclination angle of core truss on flutter characteristic is analyzed.
文摘This work deals with the active control of the vibrations of mechanical structures incorporating magnetorheological elastomer. The damping coefficient and shear modulus of the elastomer increase when exposed to a magnetic field. Compared with the vibration control where the elastomer is permanently exposed to a magnetic field, the control of this process through time reduces vibrations more effectively. The experimental study for the vibrations of a sandwich beam filled with an elastomer is conducted, followed by a numerical study using the Abaqus code. The vibration damping is found to be dependent on the loading rate of micro-size ferromagnetic particles in the elastomer.
基金supported by the National Natural Science Foundation of China(Project Nos.12022213 and 11902203)Liaoning Educational Committee Scientific Research Project in General(JYT2020035).
文摘As a novel vibration absorber,Nitinol-steel wire rope(NiTi-ST)has rarely been studied on vibration suppression for lattice sandwich beams in supersonic airflow.In this paper,NiTi-ST with nonlinear stiffness and hysteretic damping is embedded in a lattice sandwich beam to control the beam's vibration.The nonlinear restoring and hysteretic damping force of NiTi-ST are treated as polynomials.The dynamic equation is established based on Hamilton's principle.The amplitude responses of the beam with different NiTi-ST configurations are calculated.The vibration-suppression effects and energy dissipation of lattice sandwich beam with different NiTi-ST configurations under different air velocities are also compared.The frequency-domain and time-domain methods are used to analyze the structural aeroelastic properties.Simulation results show that the use of NiTi-ST can significantly suppress excessive vibration of a lattice sandwich beam in supersonic airflow.
基金This work was supported by the Ministry of Human Resource Development[IMPRINT/2016/7330]Ministry of Road Transport and Highways[IMPRINT/2016/7330].
文摘Magnetorheological fluid(MRF)sandwich beams belong to a class of adaptive beams that consists of MRF sandwiched between two or more face layers and have a great prospective for use in semi-active control of beam vibrations due to their superior vibration suppression capabilities.The composition of MRF has a strong influence on the MRF properties and hence affects the vibration characteristics of the beam.In this work,six MRF samples(MRFs)composed of combination of two particle sizes and three weight fractions of carbonyl iron pow-der(CIP)were prepared and their viscoelastic properties were measured.The MRFs were used to fabricate different MRF core sandwich beams.Additionally,a sandwich beam with commer-cially available MRF 132DG fluid as core was fabricated.The modal parameters of the cantilever MRF sandwich beams were determined at different magnetic fields.Further,sinusoidal sweep excitation tests were performed on these beams at different magnetic fields to investigate their vibration suppres-sion behavior.MRF having larger particle size and higher weight fraction of CIP resulted in higher damping ratio and vibration suppression.Finally,optimal particle size and weight fraction of CIP were determined based on the maximization of damping ratio and minimization of weight of MRF.
基金supported by the National Natural Science Foundation of China (Grant Nos. 11032001 and 10602005)
文摘Experiments were conducted to investigate the deformation of cantilever sandwich beams with pyramidal truss cores subjected to impact by a projectile at their tips.A new technique was employed to the fabrication of sandwich beams with pyramidal truss cores.For a better observation of large deformation of specimens during impact process,a high-speed digital video camera was successfully used to capture the instant shapes of the deformed beams.A projectile collection device was designed and installed to avoid the projectile flying away from the beam tips after impact and thus the kinetic energy imparted to the beams was measurable.The experiments show that the sandwich beams have a superior shock resistance compared to the monolithic beams of the same material and mass.Further,finite element simulations were performed to gain insight into the deformations and plastic energy absorptions in the sandwich beams.
文摘The sandwich structure is of great interest because of its advantage of combining light weight and high flexural stiffness. Many previous researchers have studied the failure modes in sandwich structures and the effects on the load capacity caused by the change of the constituent materials’ properties. In this research, by applying Finite Element Analysis (FEA) method, we simulated a cantilever beam composed of a sandwich structure in Abaqus, to find out the preferred design principles that help decrease the stress and displacement in the beam when applied a uniform load. We also determined the effect of the core geometry on decreasing the displacement and the stress in the beam.
基金supported by the National Natural Science Foundation of China(Grant No.41972323 and 51991364)Science and Technology Project of the 13th Five-Year Plan of Jilin Provincial Department of Education(Grant No.JJKH20190126KJ)the Science and Technology Developing Plan Project of Jilin Province(Grant No.20160520021JH).
文摘This paper is focused on the post-buckling behavior of the fixed laminated composite beams with effects of axial compression force and the shear deformation.The analytical solutions are established for the original control equations(that is not simplified)by applying the Maclaurin series expansion,Chebyshev polynomials,the harmonic balance method and the Newton’s method.The validity of the present method is verified via comparing the analytical approximate solutions with the numerical ones which are obtained by the shooting method.The present third analytical approximate solutions can give excellent agreement with the numerical solutions for a wide range of the deformation amplitudes.What’s more,the effect of shear deformation on the post-bucking configuration of the sandwich beam is also proposed.It can be found that the shear angle has a great influence on the post-buckling load of composite beams.Therefore,the model simplifying the shear formation term as small quantity is not accurate for the case of sandwich beam with soft core.