Low Velocity Impact And Thermal Dynamic Analysis Of Functionally Graded And Fibre Metal Lamianted Shells

Functionally graded (FG) shallow spherical shells and Fibre metal laminated(FML) shallow spherical shells are considered in this thesis. The material properties offunctionally graded materials (FGMs) vary continuously from one interface to theother interface and determined by Mori-Tanaka scheme or rule of mixtures based onVoigt model. Fibre metal laminates (FMLs) are hybrid composite materials built upfrom metal layers and fibre reinforced composite layers. The low velocity impact andthermal problem of these composite structures which are frequently experienced intheir serve environments are addressed in this thesis.By adapting the approximate coefficients of contact stiffness, the modifiednonlinear Hertzian contact law is established and used to determine contact force.Based on the first-order shear deformation theory and Mori-Tanaka scheme, anonlinear low velocity impact model for functionally graded shallow spherical shellsis established, and a semi-analytical method is proposed to seek the solution. Thedeformation, contact force, velocity and indentation during the low velocity impactare discussed.Based on the higher-order shear deformation theory and rule of mixtures, and thetemperature field are determined by the steady state heat transfer equation, an exactnonlinear low velocity impact model for functionally graded shallow spherical shellsto thermal effect is established, and the solution are obtained by an iterative procedurebased on the Chebyshev collocation method and the Newmark method. The effects ofmaterial properties, temperature, initial impact velocity and mass of the impactor onthe nonlinear dynamic response of functionally graded shallow spherical shells arediscussed.An exact displacement field with interfacial damage is established by introducingthe shape functions and the interfacial relative displacements, and combining theCohesive Zone theory, the elastic constitutive relations for fibre metal laminatedshallow spherical shells with interfacial damage are obtained. The transienttemperature field is obtained from the unsteady state heat transfer equation by usingthe finite difference method. Then the transient thermal model for fibre metallaminated shallow spherical shells is presented, and the solution is obtained by aniterative procedure based on the Chebyshev collocation method and the Newmarkmethod. The transient temperature of fibre metal laminated and pure metal shallow spherical shells, thermal deformation and stresses of fibre metal laminated shallowspherical shells with or without interfacial damage are discussed.By using the elastic constitutive relations reflecting interfacial damage, andcontact force determined by the nonlinear modified Hertzian contact law forcomposite laminated structures，a nonlinear low velocity impact model for fibre metalshallow spherical shells is established. Stresses in fibre metal laminated shallowspherical shells with or without interfacial damage are analyzed. The effects ofinterfacial damage on the nonlinear dynamic response of fibre metal laminatedshallow spherical shells are discussed.Based on the higher-order shear deformation theory, and introducing the shapefunctions and Heaviside function, an exact displacement field which satisfies thetransverse shear stresses vanish on the upper and lower surfaces and the stressescontinuity conditions at the interfaces for composite laminated shells is proposed. TheChoi and Chang failure criteria is used to predict the matrix crack and thedelamination. And in order to account for the stiffness reduction of the damage region,the elastic constitutive relations are modified by using reduced material propertiesmethod. Then, a semi-analytical model for the evolution of matrix crack anddelamination of fibre metal shallow spherical shells to low velocity impact isestablished. The matrix crack and delamination evolution, contact force and deflectionof fibre metal laminated shallow spherical shells are investigated.