Issue 51

S. Merdaci et alii, Frattura ed Integrità Strutturale, 51 (2020) 199-214; DOI: 10.3221/IGF-ESIS.51.16 201 Let the present plate is converted from lower to upper surfaces according to an exponential or polynomial laws. We will consider firstly a non-homogeneity material with a porosity volume function, α (0 ≤ α ≤ 1). In such a way, the efficient material properties, as Young’s modulus, can be expressed as: 1 2 2 1 0 P z h E E e             (1) where P (P ≥ 0) represents a factor that points out the material variation through the thickness. Note that the plate is perfectly porous homogeneous when k equals zero and it gets the perfect homogeneity shape when P = α = 0. The functional relationship between E(z) for the ceramic and metal FGM plate is assumed to be is Ref. [30-31].     ( ) 2 c m m c m E z E E V E E E       and 1 2 p z V h         (2) where E c and E m are the corresponding properties of the ceramic and metal, respectively, and “ P ” is the volume fraction exponent which takes values greater than or equal to zero. The above power-law P-FGM assumption reflects a simple rule of mixtures used to obtain the effective properties of the ceramic-metal sandwich plate. The rule of mixtures applies only to the thickness direction. Note that the volume fraction of the metal is high near the bottom surface of the plate, and that of the ceramic is high near the top surface. Furthermore, Eqn. (2) indicates that the bottom surface of the plate (z = −h/2) is metal whereas the top surface (z = h/2) of the plate is ceramic. In which n represents number of layers of sandwich plate and (1) (2) (3) 4 1 1 2 2 3 3 4 2 1 3 4 , [ , ] ; 1 , [ , ] ; , [ , ] P P z h z h V z h h V z h h V z h h h h h h                       (3) Table 1: Displacement models D ISPLACEMENT FIELD AND CONSTITUTIVE EQUATIONS n the present analysis, the shear deformation plate theory is suitable for the displacements (Merdaci et al [20-25]): Model Theory Transverse shear function Unknown variables CPT Classical plate theory   0 f z  3 FSDPT First-order shear deformation theory [26]   z f z  5 ESDPT Exponential shear deformation plate theory [28]   2 2 / ( ) . z h f z z e   5 SSDPT Sinusoidal shear deformation plate theory [27] ( ) sin z h f z h          5 HSDPT Higher-order shear deformation theory[29] 2 2 4 ( ) 1 3 z f z z h        5 Present Present higher-order shear deformation theory 2 2 5 1 ( ) 4 3 z f z z h         4 I