A new fifth-order shear and normal deformation theory (FOSNDT) is developed for the static bending and elastic buckling analysis of functionally graded beams. The properties of functionally graded material are assumed to vary through the thickness direction according to power-law distribution (P-FGM). The most important feature of the present theory is that it includes the effects of transverse shear and normal deformations. Axial and transverse displacements involve polynomial shape functions to include the effects of transverse shear and normal deformations. A polynomial shape function expanded up to fifth-order in terms of the thickness coordinate is used to account for the effects of transverse shear and normal deformations. The kinematics of the present theory is based on six independent field variables. The theory satisfies the traction free boundary conditions at top and bottom surfaces of the beam without using problem dependent shear correction factor. The closed-form solutions of simply supported FG beams are obtained using Navier's solution procedure and non-dimensional results are compared with those obtained by using classical beam theory, first order shear deformation theory and other higher order shear deformation theories. It is concluded that the present theory is accurate and efficient in predicting the bending and buckling responses of functionally graded beams.

In the present study, a new fifth-order shear and normal deformation theory is developed and applied for the bending analysis of functionally graded (FG) plates resting on two-parameter Winkler-Pasternak elastic foundation subjected to non-linear hygro-thermo-mechanical loading. The theory involves the effects of transverse shear and normal deformations, i.e. thickness stretching. Navier's solution technique is used to obtain analytical solutions for simply supported FG plates. The results are presented in non-dimensional form and are compared with previously published results in the literature. The present study has the following novelties. The present polynomial-type theory is computationally simpler than non-polynomial-type plate theories which are mathematically complicated, tedious and more cumbersome. For the accurate structural analysis of composite plates under hygro-thermal loading, consideration of thickness coordinate up to third-order polynomial is not sufficient. Therefore, in the present theory, thickness coordinate is expanded up to fifth-order polynomial to get the accurate displacements and stresses. Transverse normal stress/strain plays an important role in the modeling of thick plates which is neglected by many theories available in the literature.

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In this paper, bending analysis of simply supported composite beam is carried out by using refined beam theories. The theory accounts for the parabolic variation of shear strain through the depth of beam, hence avoid need of shear correction factor. The governing differential equations and boundary conditions are obtained by using the principle of virtual work. A simply supported composite beam subjected to central concentrated load is considered for detail numerical study. The results of displacements and stresses are obtained and found agree well with those obtain by other higher order and lower order theories.

A new analytical solution is presented for functionally graded (FG) beams to investigate the bending behaviour under the hygro-thermo-mechanical loading using a new fifth order shear and normal deformation theory (FOSNDT). The material properties of the FG beam are varied along the thickness direction according to the power law index. In the present theory, a polynomial shape function is expanded up to fifth-order in terms of thickness coordinate to consider the effects of transverse shear and normal deformations. The present theory is free from the shear correction factor. Using the Navier's solution technique the closed-form solution is obtained for simply supported FG beams. All the results are presented in non-dimensional form and validated it by developing the classical beam theory (CBT), first order shear deformation theory (FSDT by Mindlin) and third order shear deformation theory (TSDT by Reddy) considering the hygro-thermo-mechanical loading effects which is mostly missing in the literature. It is noticed that the presented FOSNDT is very simple and accurate to predict the bending behaviour of FG beams under linear and non-linear hygro-thermo-mechanical loadings.