Stability of variable stiffness composite laminates under compressive and shearing follower forces

Dynamic stability characteristics of variable stiffness composite rectangular panels subjected to non-conservative compressive or shear follower loads are investigated here using the shear-deformable finite element method. At the beginning, the veering of modal frequencies are studied by the eigenvalue analysis to classify the divergence and flutter type of instabilities and evaluate the critical loads for isotropic and variable stiffness composite plates under both types of follower forces. Thereafter, the governing finite element equations are reduced into a set of Mathieu-Hill equations employing the modal transformation technique and the method of multiple scales is used to determine the regions of instability of composite laminates under pulsating follower forces. Limited numerical examples are presented to demonstrate the simple and combination (additive/difference) type of parametric instabilities of edge supported and cantilever panels with curvilinear fibers under compressive or shear pulsating follower forces.