Finite element model is presented for the analysis of hybrid piezoelectric beams under static electromechanical load, using the one-dimensional (1D) coupled zig-zag theory developed recently by the authors. Two noded elements are used with cubic Hermite interpolation for deflection and electric potentials at the sub-layers and with linear interpolation for axial displacement and shear rotation. The expressions for the variationally consistent stiffness matrix and load vector are derived and evaluated in closed form using exact integration. The formulation is validated by comparison with the analytical solution for simply-supported beam. The finite element model is free of shear locking. The present zig-zag finite element results for cantilever beams are compared with the 2D finite element results using ABAQUS to establish the accuracy of the zig-zag theory for these boundary conditions.
IntroductionHybrid piezoelectric laminates with embedded or surface bonded piezoelectric sensors and actuators to achieve desired control, form part of a new generation of adaptive structures. Robust coupled electromechanical models are needed to obtain accurate response of these structures. This work presents a finite element model of an efficient zig-zag theory for static analysis of hybrid beams. A review of 3D approaches, 2D theories for plates and shells, and 1D theories for beams, has been presented by Saravonas and Heyliger [19]. Analytical 2D solutions [16,23] for static response are available for simply-supported hybrid panels and beams. Finite element modelling of adaptive structural elements has been recently reviewed [1]. The normal to the mid-surface of thick and moderately thick beams gets distorted due to significant shear deformation and layerwise inhomogeniety. Classical lamination theory (CLT), first order shear deformation theory (FSDT) and third order shear deformation theory (TOT) use the same approximation for displacement across the thickness. Layer-wise approximations are used in discrete layer theories (DLT) with the number of unknowns dependent on the number of layers. The conditions of continuity of shear stress at the layer interfaces are violated in these theories. Zig-zag theories (ZIGT) are discrete layer theories in which the continuity conditions of shear stress at the layer interfaces and the shear traction-free conditions at the bottom and top of the beam are enforced to reduce the number of primary displacement unknowns whose number becomes independent of the number of layers. In coupled theories the electric variables are included as additional unknowns and the charge equations of equilibrium are included, whereas in uncoupled theories these are excluded. Smeared beam and discrete layer elastic beam models [2,7,10,17] have been used for hybrid beams by including the effect of induced strain of actuators. Uncoupled CLT, FSDT and TOT [3,4,8,15,22,25] and coupled CLT, FSDT, TOT [7,9,14,20,21,24,26] and coupled DLT [6,18] have been applied for the analysis of hybrid beams.Efficient zig-zag theories...