Designing Highly Loaded Connections in a Composite Fuselage

Abstract

The increased use of composites in airframe structures creates some very challenging design problems where the need for low weight and low, or at least acceptable, cost dictate very careful selection of design concepts and fabrication processes. Typical examples of challenging structural details are highly loaded connections with parts meeting at an angle. Usually, optimizing the individual components of the joint yields relatively low weight savings. Only by redesigning the adjacent structure and optimizing load transfer and redistribution can one benefit from the use of composites to the fullest and generate highly weight-efficient structures. The case of the floor–skin attachment for a transport fuselage with skins made with grid-stiffened structure is used as the example in this study. Finite elements and local analysis methods are combined for the design iterations. It is shown that, by incorporating the floor substructure and the skin into the design problem and redistributing the load between the different joining members, low-cost low-weight structures can be generated.