Nonlocal Anlaysis Of Buckling Of Bilayer Composite Material Systems

Composite materials are made from two or more different materials by physical or chemical methods.Their history can be traced back very far,so far as the straw reinforced clay from ancient times and steel reinforced concrete used for hundreds of years.Composites can play the advantages of the various constituent materials and overcome the shortcomings of a single material,thereby expanding the applications.In general,the composite materials have light weight,high strength,good elasticity,chemical resistance,thermostability and other fine features.Therefore,they are widely used in aerospace,automotive,construction,clothing and other fields.When the particles are nanoscale size,they have quantum size effect,small scale effect,surface effect and marcoscopic quantum tunneling effect,and hence exhibit many unique properties which make micr/nano composite materials have broad application in catalysis,light filter,optical absorption,medicine,magnetic and new materials.In this paper,the surface buckling of micro/nano composite system is studied by using nonlocal theory.The main work is as follows:(1)Based on nonlocal elastic plate theory,the axial buckling behavior of bilayer micro/nanoplates composite systems is investigated.Through different axial compression(uniaxial and biaxial),the conditions for surface buckling are obtained,and we also discuss the nonlocal effects,the effects of elastic modulus ratio and thickness ratio,effect of bonding strength between layers,and scale effects of geometry parameters.The results show that whether the surface buckling happens or not depends on the bonding strength,and that not only the critical bucklin load but also the critical buckling modes are changed by nonlocal parameters.(2)Based on nonlocal elastic cylindrical shell theory,the axial buckling behavior of bilayer cylindrical shells composite systems is investigated.Through different deformation(axisymmetric buckling and non-axisymmetric buckling),the conditions for surface buckling are obtained,and we also discuss the nonlocal effects,the effects of elastic modulus ratio and thickness ratio,effect of bonding strength between layers,and scale effects of radius ratio and geometric parameters.The results show that whether the surface buckling happens or not depends on the bonding strength,and that not only the critical bucklin load but also the critical buckling modes are changed under nonlocal parameters.It's showed that long thin cylindrical shell system buckles more easily under nonlocal parameters.(3)Based on nonlocal elastic theory,stripe buckling of micro/nanoplate bonded on elastic substrate is investigated,where the plate and elastic substrate are modeled respectively.Through different interface conditions(perfectly bonded interface and freely sliding interface),the Winkler elastic coefficients are derived analytically,and the nonlocal effects and the effects of the Poisson's ratio of elastic substrate,elastic modulus ratio and thickness ratio are discussed.Due to nonlocal parameters,the effective bending stiffness is decreased,and the reaction force of elastic substrate is also reduced.Therefore,micro/nanoplate more easily occurs short wavelength buckling.In addition,the load is higher but the wavelength is short with perfectly bonded interface.(4)Based on nonlocal elastic theory,circumferential buckling of cylindrical shell coating elastic body is investigated,where the cylindrical shell and elastic body are modeled respectively.Through different interface conditions(perfectly bonded interface and freely sliding interface),the Winkler elastic coefficients are derived analytically,and the nonlocal effects and the effects of the Poisson's ratio of elastic body,aspect ratio,elastic modulus ratio and thickness ratio are discussed.Due to nonlocal parameters,the effective bending stiffness is decreased,and the reaction force of elastic body is also reduced.Therefore,cylindrical shell buckles more easily,but the half wavenumber may not be changed because of the closed loop.