Strut Sizing
Using the Black Metal approach, the software model defines the location of the struts but not their size. Importantly, the placement of struts based on the manufacturing constraints meant the design had deviated from the Optistruct result.
It was apparent that to achieve an efficient truss structure, the peak strain in each strut for all load-cases should be similar to its neighbour. This ensured that for the Ultimate load, no redundant material was present. Initial studies using the model shown above, had shown a widely varying peak strain in all struts. It was also necessary to define the load carried by each strut, in order to allow the manufacturers to determine the strut geometry. It was desirable to achieve this balanced peak strain using a single strut size to reduce the complexity and cost of manufacture. Considering each strut in isolation its geometry was then modified to achieve the target strain.
The filament winding process used to manufacture the strut allows the outer diameter of a strut to be easily modified. The inner diameter is controlled by the mandrel onto which the fibre will be wound. Therefore, the strut outer diameters were modified in preference to the inner diameters in order to achieve a balanced strain. Having achieved a balanced strain in all struts using reasonable strut sizes, the loads present in each strut were extracted.
Design for Manufacture
A CAD model was required to allow the manufacturers and
designers to move to the next step. Firstly, the load requirements on the perimeter frame of the wing rib concept were used to define its thickness. Airbus UK carried out the calculations and provided the results to Oxford Brookes Uuniversity. Oxford Brookes were then able to complete the design, compensating for |
