Loads on Shear Cleats (fuselage frames)
Loads on Shear Cleats (fuselage frames)
(OP)
My question is about loads acting on shear cleat attaching a typical fuselage frame to the skin.
It is a Airbus design policy to use L- shape shear cleats to attach frames to the skin & stringers. In this case frames have no mouse-holes,where stringers pass through. Mouse-holes are on shear cleats.
As far as I know,load on the fasteners attaching shear cleat to the skin, shear only. Is it the case also for deltaP load cases? I mean, for internal pressure load cases, might there be any tensile load on these fasteners i.e. does shear cleat becomes tension cleat :)
If you can help me I will be glad.
Thanks in advance.
It is a Airbus design policy to use L- shape shear cleats to attach frames to the skin & stringers. In this case frames have no mouse-holes,where stringers pass through. Mouse-holes are on shear cleats.
As far as I know,load on the fasteners attaching shear cleat to the skin, shear only. Is it the case also for deltaP load cases? I mean, for internal pressure load cases, might there be any tensile load on these fasteners i.e. does shear cleat becomes tension cleat :)
If you can help me I will be glad.
Thanks in advance.





RE: Loads on Shear Cleats (fuselage frames)
RE: Loads on Shear Cleats (fuselage frames)
Probably, since the magnitude is small, it is ignored for metallic designs. Therefore, in my short carrier, I have never seen that they have ever been taken into account.
But in composite design, it seems, even this magnitude, that it can cause a problem because of pull-through phenomenon.
Cheers.
RE: Loads on Shear Cleats (fuselage frames)
RE: Loads on Shear Cleats (fuselage frames)
RE: Loads on Shear Cleats (fuselage frames)
Question was whether there can be any tension load on the shear cleats due to internal pressure. In metallic fuselage structure I have never seen anybody who is trying to calculate such load acting on the cleats.
Question was not about shear loads.
Regards.
RE: Loads on Shear Cleats (fuselage frames)
RE: Loads on Shear Cleats (fuselage frames)
Shear loads on them are calculated by simply taking the differences of normal forces (calculated from grid point force balance) at two ends of each BAR element idealizing the frame.
RE: Loads on Shear Cleats (fuselage frames)
if you're stressing hte clips you always try "no analysis required, as these aren't primary structure (not modelled in the fuselage model)". my next tack would be "OEM, because you didn't model them I'll have to do ,000s of hours of work to determine the effect (basically to model them !), so you pay me for that" seriosuly, trying to actuately account for their effect is going to be little short of adding them into the model; you might (just, might) get somewhere by modelling a section of the fuselage with and without shear clips, applying a unit shear load into the skin to see how it redistributes with the new load path.
good luck !
RE: Loads on Shear Cleats (fuselage frames)
I am not in global model business. But as far as I know,in the company that I work for, they model frames as BAR elements and skins as membrane elements and nodes are located at the outer loft. I did not see any shear cleat idealization in their global models. If I do the fuselage global model, I would model them with elements like NASTRAN CSHEAR elements lying on the plans perpendicular to the fuselage skin. Anyway, as I said, that's not my business and not my responsibility and I am not the decision maker.
I have got my answer about order of magnitude of possible tensile loads from you. It is as I expected. Thanks again.
RE: Loads on Shear Cleats (fuselage frames)
from this model i think you could say that the radial tension stresses in the frame webs (as modelled) is the tension that the shear clip has to carry, in addition to the shear introduced into the frame web.