OPTIMAL-DESIGN OF SANDWICH AND LAMINATED COMPOSITE PLATES ON THE PLANNING OF EXPERIMENTS

Optimal design problems of sandwich. plates with soft core and laminat ed composite face layers, and multilayered composite plates are invest igated. The optimal design problems are solved by using the method of the planning of experiments. The optimization procedure is divided int o the following stages: choice of control parameters and establishment of the domain of search, elaboration of plans of experiment for the c hosen number of reference points, execution of the experiment, determi nation of simple mathematical models from the experimental data, desig n of the structure on the basis of the mathematical models discovered, and finally verification experiments at the point of the optimal solu tion. Vibration and damping analysis is performed by using a sandwich plate finite elements based on a broken line model. Damping properties of the core and face layers of the plate are taken into account in th e optimal design. Modal loss factors are computed using the method of complex eigenvalues or the energy method. Frequencies and modal loss f actors of the plate are constraints in the optimal design problem. The re are also constraints on geometrical parameters and the bending stif fness of the plate. The mass of the plate is the objective function. D esign parameters are the thickness of the plate layers. In the points of experiments computer simulation using FEM is carried out. Using thi s information, simple mathematical models for frequencies and modal lo ss factors for the plate are determined. These simple mathematical fun ctions are used as constraints in the nonlinear programming problem, w hich is solved by random search and the penalty function method. Numer ical examples of the optimal design of clamped sandwich and simply sup ported laminated composite plates are presented. A significant improve ment of damping properties of a. sandwich plate is observed in compari son with a simple plate of equal natural frequencies.