Stress Analysis of Joint between Fuselage and Wing
PROKURA INNOVATIONS, NEPAL
During a flight, all the load of drone is carried by wing but fuselage of drone is much heavier than wing as it includes battery, payload, electronics components, structures, etc. So the joint between fuselage and wing should be strong enough to handle the stress exerted during flight and landing. Also, wing should be easily attached and detached modularly with less time as our VTOL is going to be used for medical delivery which will affect the life of people. So the design was made such that to attach a wing on fuselage, we have to put wing on fuselage, slide the wing forward and lock it using Quick Release Axle.
Sliding it forward locks the trailing edge part of the wing and locking with Quick Release Axle locks the leading edge part of wing with fuselage. So the stress is transferred from wing to fuselage and vice-versa using that joint. That’s why the strength of joint matters a lot.
So the stress analysis of joint including both leading edge part and trailing edge part was done. The analysis showed that keeping the locking part for leading edge far from the spar rod was creating bad effects. So the design was improved again. Then again, its stress analysis was done and the result was much improved but not yet safe. The stress has yet to be distributed and the joints were still to be strengthened. To strengthened the joint, the same joint was sandwiched using Stainless Steel sheet on both side. Joint material was previously plywood only.
Then the stress analysis was done also adding the fuselage wall, the result was much improved as stress was more distributed, but still the result of the analysis is not appropriate to be trusted as it only represented the half part of the drone. The stress may have behaved when full drone was simulated. So, the whole drone was simulated with higher computation and the result was much trusted. Finally the factor of safety was greater than 1. To make the safety margin (Safety Margin= FOS-1) greater than 1, we have to increase the thickness of joint and keep doing stress analysis again and again which would take some time.