The stress distributions over the rib structure are shown the illustration above. The results from the bending and shear-flow load-cases show the highest stress levels at the top of the castellations. High stress levels are also noted at the corner locations where the rib was connected to the wing. The highest stress levels in the struts were found in strut 5, which corresponds to the highest tensile force observed in the axial load results.

The successful completion of this analysis work demonstrated that the single struts were able to meet the maximum tensile loads. Physical samples of single struts and bonded end test pieces were subsequently subjected to testing on a bespoke rig to verify the loads the analysis had shown would be present in the struts.

The project was a bold yet successful first step in the realization of the promise first indicated in the early Airbus study. MIRA’s pragmatic approach demonstrated the importance of validating a baseline FE model of a component before moving to the system level. This was standard practice for metallic structures ten years ago, but as confidence in the metallic material models and modeling techniques has increased this has become less commonplace. The relatively undeveloped composite material models and modeling techniques, ensure it is vital that confidence is gained with small structures before moving to large components. When combined with novel manufacturing techniques, this becomes even more important.