A DISCRETE MODEL FOR THE OPTIMAL-DESIGN OF THIN COMPOSITE PLATE-SHELL TYPE STRUCTURES USING A 2-LEVEL APPROACH

The sensitivity analysis of the optimization of general thin shell structures made of composite materials is presented. The model is based on a simple and efficient plate-shell finite element with 18 degrees of freedom using the discrete Kirchhoff theory for the bending effects. The design variables consist of the fiber orientation angles and/or thicknesses of each individual layer. The design sensitivities are evaluated through a semi-analytical formulation. The objective of the design is the minimization of a maximum displacement or maximization of a specified natural frequency and the minimization of the volume of plate-shell material which is carried out using a two-level approach. The constraint functions are the displacements, stresses (Tsai-Hill failure criterion), volume of shell material or the natural frequency of a specified vibration mode. Numerical examples are given to show the application, efficiency and accuracy of the proposed model.