Efficient shear deformation theories for laminated elastic and smart composite plates

Abstract

newline In this thesis, two new shear deformation theories have been developed and assessed newlinefor laminated composites. newlineThe first shear deformation theory is an enhanced efficient zigzag theory which is newlineformulated for static response of elastic composite plates under sinusoidal and uniformly newlineapplied mechanical loading on lateral surfaces of laminated elastic rectangular plates. newlineThe number of variables is six, which is one more than the conventional zigzag theory. newlineTransverse shear stresses have been obtained through the use of constitutive equations in newlineboth symmetric and antisymmetric laminates. The theory has a good representation of all newlinethe three displacement components. This is obtained by using individual descriptions for newlineeach layer as is observed in three dimensional elasticity solution. Interlaminar continuity newlineconditions on all displacement components, all transverse stresses and on the gradient of newlinetransverse normal stress as well as transverse shear free conditions on the top and the newlinebottom surfaces have been utilized to make the primary variables independent of number newlineof layers in the laminate. Equilibrium equations and boundary conditions are derived from newlinevariational principle. Analytical Navier solution is obtained for simply supported square newlineand rectangular plates. The accuracy of the present theory is assessed by comparison newlinewith three dimensional elasticity solution. It is found that refinement of the transverse newlinedisplacement alone is not sufficient to make the new theory capable to provide good newlineaccuracy in calculation of transverse stresses from constitutive equations, though some newlineimprovement is obtained in case of symmetric laminates. newlineThe second shear deformation theory is a zigzag theory which is formulated based newlineon the relaxation of zero transverse shear stress condition on lateral surfaces of laminated newlinepiezoelectric plates. Variational principle is used to derive the theory. Nonlinear variation newlinexiv newlineof the electric potential field has been captured by dividing each layer into suitable number newline