An invariant eight-node hybrid-stress element for thin and thick multilayer laminated plates

A hybrid‐stress eight‐node isoparametric element is developed for the analysis of thin or thick multilayer fiber‐reinforced composite plates. Transverse shear deformation effects are included by allowing for individual layer cross‐section warping for thick laminates, or alternatively, laminate non‐normal cross‐section rotations for thin to moderately thick laminates. All stress components are included and are interpolated independently within each layer. Interlayer surface traction continuity and appropriate upper/lower surface traction‐free conditions are exactly satisfied. The layer stress field is selected on the basis of earlier single‐layer element studies so that the resulting element is naturally invariant with respect to co‐ordinate translation or rotations, is non‐locking in the thin‐plate limit, and the element stiffness is of correct rank. An example for which an elasticity solution is available is used to demonstrate the element performance. Schemes for reduction of element stiffness computation time are also presented.