Prevost XLII Skin Delamination Repair

[davidbrady]

Buckling FEA results: Remarkably, adding ribs increases the buckling strength of the flat stainless steel panel by a factor of 7. Double remarkably, the buckling critical load of an H3 fiberglass panel is very close to the that of a ribbed stainless steel panel. Granted, I'm estimating the dimensions of the ribs; the actual size could put the buckling loads on par with each other. Notice how slight the buckling displacement is, it's in the hundredths of inches.

Here's the model. Forces are applied longitudinally on one end. The other end is constrained to resist the forces.



Flat stainless steel panel. Buckles at 748 lbs applied longitudinally:


Ribbed stainless steel panel. Buckles at 5201 lb, applied longitudinally, parallel to the ribs:


Flat Fiberglass panel. Buckles at 6830 lbs:


What does this exercise tell me? It says that differences in panel characteristics between the Fiberglass H3 panel and the ribbed stainless XLII panel aren't critical in the glue failure, and it tells me the glue stresses are low. The buckling strength of the panels puts an upper limit on the forces induced in the adhesive and that's approximately 200 lb/in. So if the bead is one inch wide, the shear stress in the glue is at a maximum of 200 psi, which is well within the elastic range of the usual adhesives, and is well below the endurance stress levels; i.e., the glue should last a good long time before failure.

----EDIT 5/6/17---
The stiffness of the SS panel is two times the stiffness of the FRP panel. Greater stiffness leads to more load supported which leads to greater stresses on the adhesive.