This proposal was for the structural analysis and design optimisation of the lower fuselage of an aircraft. The objective of the structural optimisation was minimum weight and the design constraints fall into two categories; firstly, the capability to withstand structural loads with sufficient margins, and secondly constraints relating to the manufacturing methods. The structure to be optimised was a thin-walled metallic structure with stiffening elements (stringers and frames) using three options for the manufacturing technology:

• Riveted stiffeners (conventional technology),
• Laser welded integral stiffeners,
• Load-adapted stiffeners with welded integral knots.

The first two options are reference designs that were analysed and compared with a new proposal based on the third manufacturing technology. Additionally, two types of aluminium alloy were considered for the weldable options. The work was carried out by experienced aerospace engineers at AOES Group BV, a Dutch SME with many years specialist experience in the structural design, analysis and verification of aircraft and spacecraft structures, including FEM-simulation of large components for aircraft fuselage structures. AOES used design optimisation and topology optimisation tools in NASTRAN for identifying the preliminary layout and sizing then standard stress and buckling analysis approaches for the accurate simulation of the load-bearing characteristics and detailed mass calculation. For seamless transmission of data and dissemination of results, data can be received or transmitted as engineering drawings, neutral CAD files or CATIA files. AOES also intended to use the resources of its Media lab department to provide attractive 2-D and 3-D rendering of the results of the work performed.