Integrated Topology and Fiber Optimization for 3-Dimensional Composites

Abstract

The importance of computer aided engineering in product development processes and research has been increasing throughout the past years. As e.g. energy efficiency and therefore mechanical lightweight structures of new products plays a large role, optimization tools gained more and more importance. Weight reduction can be achieved by a change of the component’s design and by selection of adapted materials. Such an improved utilization of material can be implemented only if there is an accurate knowledge of the loads and the conditions on the material. As modern composite materials can make a clear weight reduction possible, appropriate tools and methods are necessary within the design process. Even for isotropic materials, the design of complex parts is not trivial. For the design of composites, additional parameters have to be considered, such as number and thickness of the plies and the orientation of fibers. Hence, design by intuition leads only in few cases to optimal parts. For the determination of the basic layout of a new design topology optimization can be used. It involves the determination of features such as the number, location and shape of holes and the connectivity of the domain. Today topology optimization is very well theoretically studied and also a very common tool in the industrial design process but is limited to isotropic materials. Several approaches for the determination of optimal fiber orientation have been presented in the past e.g. placing the fibers in the direction of the first main stress. Based on a finite element analysis, a method is presented that uses the orientation of main stresses to determine optimal orientations and thickness relations of plies. It is now applicable to complex 3D geometries. The result is a design proposal for the laminate structure (orientation and thicknesses of plies), taking multi-axial load cases into account. To determine a design proposal for complex 3D laminate structures, the application of both methods, topology and fiber optimization, is appropriate. Regarding an independent serial application of topology and fiber optimization it makes sense carrying out topology optimization in a first step and the determination of fiber orientations in a second step. An integrated approach might show even better results in certain cases. For that, we combined topology and fiber optimization in a two-level approach by optimizing laminate structure within each iteration of topology optimization process. In this paper topology and fiber orientation optimization are integrated into a straightforward, automatic way.