On the Use of Higher Order Plate Theories for Determining Free-Edge Stresses

The minimum number of kinematic variables in conjunction with higher order plate theories for approximating the stresses in the free-edge zone of a laminate under uniaxial inplane tension is examined. It is well recognized that classical shear deformation theory is not appropriate for such problems. The through-the-thickness normal strain component must be non-zero in order to obtain reasonable results. Two classes of higher order theories are compared for approximating interlaminar stress distributions in the free-edge zone. These theories employ kinematic relations which lead to constant and linear distributions of transverse normal strain through-the-thickness of the laminate. Interlaminar stresses in the free-edge zone at the midplane and at the 00/900 interface of a bidirectional laminate are considered.