Title : Dynamic buckling of smart sandwich beam subjected to electric field based on hyperbolic piezoelasticity theory
Abstract:
CNTs have superior properties such as high tensile strengths, high aspect ratio, high stiffness and low density and however, can be used as the reinforce phase for the composite materials. In this paper, dynamic buckling of the smart subjected to blast load subjected to electric field is studied. The effect of CNTs on the forced vibration of micro cylindrical shell is presented. In nano and micro scales, considering size effect is essential. The sandwich structure is rested on Pasternak foundation with springs and shear elements. Applying piezoelasticity theory and hyperbolic shear deformation beam theory (HSDBT), the motion equations are derived by energy method. For calculating the dynamic instability region (DIR) of the sandwich structure, differential quadrature method (DQM) along with Bolotin method is used. The effect of different parameters including CNTs volume percent and distribution type, boundary conditions, size effect and length to thickness ratio on the frequency response of the of the system was studied. It can be concluded that the FGX pattern was the best choice compared to other cases. It was observed that increasing the CNT volume fraction increases the frequency and decreases the deflection of the structure. As can be seen the deflection of the strain gradient theory was lower than couple stress and the deflection of the couple stress was lower than classical one. In addition, by increasing the material length scale parameter, the amplitude of the system will be reduced. Furthermore, by considering CC boundary condition, the maximum amplitude decreases and the frequency is increased. Beam the geometry of the embedded micro cylindrical shell with radius, R, length, L, and thickness h. The structure is reinforced by FG-CNTs and is subjected to harmonic load. The structure is made from Poly methyl methacrylate (PMMA) with the constant Poisson’s ratios of vm = 0.34, temperature-dependent thermal coefficient of αm = (1 + 0.0005ΔT)× 10?6/K, and temperature-dependent Young moduli of Em =(3.52?0.0034T)GPa in which T=T0 +ΔT and T0 = 300 K (room temperature) (Madani et al. 2016). The effect of distribution type of CNT on the frequency response of the structure is shown.
