A CONSISTENT REFINEMENT OF FIRST-ORDER SHEAR DEFORMATION THEORY FOR LAMINATED COMPOSITE AND SANDWICH PLATES USING IMPROVED ZIGZAG KINEMATICS

A refined zigzag theory is presented for laminated-composite and sandwich plates that includes the kinematics of first-order shear deformation theory as its baseline. The theory is variationally consistent and is derived from the virtual work principle. Novel piecewise-linear zigzag functions are used, providing a more realistic representation of the deformation states of transverse shear-flexible plates than other similar theories. The formulation does not enforce full continuity of the transverse shear stresses across the plate's thickness, yet it is robust. Transverse shear correction factors are not required to yield accurate results. The theory avoids the shortcomings of earlier zigzag theories ( such as shear-force inconsistency and difficulties in simulating clamped boundary conditions) which have limited their accuracy. This new theory requires only C-0-continuous kinematic approximations and is perfectly suited for developing computationally efficient finite elements. It should be useful for obtaining relatively efficient, accurate estimates of structural response, needed in designing high-performance load-bearing aerospace structures.