DESIGN OF VARIABLE STIFFNESS COMPOSITE PANELS FOR MAXIMUMFUNDAMENTAL FREQUENCY USING LAMINATION PARAMETERS

摘要

In this paper, we consider the maximisation of the naturalfrequency of composite panels. The use of composite ma-terialsallows greater freedom in tailoring the response ofthe panels. The tailoring potential of composite panelsis further expanded by introducing the concept of vari-ablestiffness panels. Variable stiffness panels are pan-elsin which fibre paths are not necessarily straight butcan be continuously curved. In this fashion, the stiffnessproperties at every point of the panel can be varied inde-pendentlyleading to optimal tailoring of the compositepanel to design requirements. The variation of the stiff-nessproperties is parameterised using lamination para-meters,and the fundamental frequency is predicted basedon classical lamination theory. A new structural approx-imationscheme is introduced which we call the gener-alisedreciprocal approximation. The optimality condi-tionsfor the problem are formulated based on the gen-eralisedreciprocal approximation. Results indicate thatsignificant increase in the optimal fundamental naturalfrequency of variable stiffness panels as compared withpanels of constant stiffness.