High-Order Finite Elements Reduced Models for Use in a Flutter Design Tool

In this paper a new "Element Independent" Finite Element modelling and analysis method for efficient modal analysis of fiber reinforced structural elements is presented. Core of this method is the use of a single, high order, "brick type, finite element for modeling 1d, 2d, and 3d-like structural elements. The use of a single element guarantiees speed and flexibility in the (re)modeling of the structure and solves the consistency and the convergence problems connected to FE-analysis in MDO environments. The present method has been implemented as a tool of a Design and Engineering Engine (DEE) for wing design, analyis and optimization in the preliminary design phase. A volume mesh of the structure is required to apply the method. A geometrical modeller-FEM preprocessor has been developed as Knowledge Based Engineering application using the ICAD Development Environment of Knowledge Technologies International (KTI). The performance of this approach has been evaluated earlier for parametric wing box structures made of an isotropic material, defined in ICAD. Modal analysis with the p-elements showed that with a limited number of p-elemets results comparable to shell elements are obtained. In this paper we define and test methods to incorporate composite materials in the DEE. We show that 3d orthotropic solid p-elements can be used to model the fiber reinforced shell structures by the use of models only having the same extensional stiffness.