Topology and Parametric Optimization of a Lattice Composite Fuselage Structure

Conventional commercial aircraft fuselages use all-aluminium semi-monocoque structures where the skin carries the external loads, the internal fuselage pressurization and is strengthen using frames and stringers. Environmental and economic issues force aircraft designers to minimize weight and costs to keep air transport competitive and safe. But as metal designs have reached a high degree of perfection, extraordinary weight and cost savings are unlikely in the future. Carbon composite materials combined with lattice structures and the use of topology optimization have the potential to offer such weight reductions. The EU FP7 project Advanced Lattice Structures for Composite Airframes (ALaSCA) was started to investigate this. An anisogrid composite fuselage section was optimized using topology optimization with respect to weight and structural performance. The fuselage was parameterised and then a detail optimization was carried out using Genetic Algorithms on a metamodel generated with Genetic Programming from a 101 point Latin hypercube design of experiments. Two optimum lattice fuselage barrels were obtained and verified with finite element simulations. The first was optimized for strength requirement, producing a light weigh fuselage with few thin helical ribs and circumferential frames, and large skin bays. The second was optimized for strength, stability and stiffness requirements, producing a heavier structure with smaller skin bays and more stiffeners, where stability became the driving O. M. Querin, V. V. Toropov, D. Liu, H. Lohse-Busch, C. Hühne, S. Niemann, B. Kolesnikov 2 criterion. It is concluded that the use of the global metamodel-based approach combined with topology optimization has allowed to solve this optimization problem with sufficient accuracy as well as provided the designers with a wealth of information on the structural behaviour of the novel anisogrid composite fuselage design. This article presents this research which has now led to the development of a new airframe concept.