Advanced Metallic Rib Solutions for Composite Wing Box: Joint Study by Aleris and Bombardier

In the frame of customer (Bombardier) supplier (Aleris) cooperation a support project was initiated. Within the cooperation Aleris performed an optimisation study into a structural metallic rib component in a composite wing torque box. A topological optimisation, using the Altair Optistruct Software, has been identified to serve as a tool to show a potential weight saving based on both the topology and sizing of the rib. Parallel to study performed by Aleris/CRD&T Bombardier used their own methods to reach a solution for an optimised wing rib. Both solutions take into account any manufacturing preferences on minimum gauge, machining tolerances etc. The objectives of the project are to achieve a low weight and low cost solution for a metallic rib in a composite torque box. The stepped approach to achieve the objective is built-up of several phases. Phase 1 is using the topology software in combination with the boundary conditions, e.g. respective load cases etc. to asses the most optimum geometry (closed web, truss or combination) Second Phase will then focus on the influence of different materials on the solution. Starting with the baseline material being 7475-T7351 and two alloys suggested for by Aleris 7081-T7651 and a corrosion resistant alloy 5059-H136. 7081-T7651 offers improved static and fatigue properties over the baseline material and 5059-H136 offers low cost and low density benefits. The result of the activities is an optimised I-beam truss design for a metallic rib, each design fulfils the design criteria for limit stress, machining tolerances etc. The low weight solution is based on 7081-T7651, 7475-T7351 is a second solution with the 5059-H136 being the last in line. All three designs provide a weight saving over the traditional closed web solution.