Design of variable stiffness composite panels for maximum fundamental frequency using lamination parameters

This paper considers maximisation of the natural frequency of composite panels. The use of composite materials allows greater freedom in tailoring the response of the panels. The tailoring potential of composite panels is further expanded by introducing the concept of variable stiffness laminates. Variable stiffness implies that fibre paths are not necessarily straight but can be continuously curved. In this fashion, the stiffness properties at every point of the panel can be varied independently leading to optimal tailoring of the composite panel to design requirements. In this paper, the variation of the stiffness properties is parameterised using lamination parameters, and the fundamental frequency is predicted based on classical lamination theory. A new structural approximation scheme is introduced which is referred to as the generalised reciprocal approximation. The optimality conditions for the problem are formulated based on this generalised reciprocal approximation. Results indicate that significant increase can be achieved of the optimal fundamental natural frequency of variable stiffness panels as compared with panels of constant stiffness.