Sandwich hull panel to plywood bulkhead T joint???

Hi,

We have been set a task for a mini University project to prepare a test hull panel using 4 layers of CSM, Bi ax, or UD glass with polyester resin on either side of a foam core but designing in the strongest bulkhead attachment we can.

Basically what is the strongest bulkhead join to hold a plywood bulkhead onto a GRP foam core panel?

We are allowed to taper the ends of the plywood, use fillets/wedges, GRP L shaped brackets, or just glass it in etc

Any ideas or definate answers with reasoning and justification would be great plus I think it is an interesting topic.

Thanks

Lee

 

This attachment is how the panel will be tested. The hull panel will be bolted to a steel rig and the end of the plywood bulkhead loaded with weight until structural failure occurs.

 

Oh well. Put in big foam wedges that extend to the load application point and cover them with glass. The upper glass laminate will be in tension, the lower in compression. Should break the test equipment.

 

My suggestion is GRP angles on both sides. I'd use triaxial stiched fabric for each angle.
Weight of layup = about 1.5 times the shear load-carrying capacity of the skin they are attached to.
Remember.. the Tri-ax will be about 150% the strength of your skin layup.
Min length of each angle 2" tapered out at 1 in 20.
First fit a 1/4" foam piece between the edge of the ply bulkhead and your "hull".
Fillet both sides with a lightweight bog, don't smear it on the hull though.
If your "hull" is freshly made you can use polyester...but if well cured use the best epoxy you can get after rough sanding. Also use peel ply if you can.
Reasons:
You need Max adhesion.. so use epoxy
You need max strength so use a stiched fabric with all the fibres across the joint for highest strength/weight.
The 1.5x skin strength and 2" min angle lengths are based on the Australian Standard for "Boat and ship design and construction, Part 3. Fibre-reinforced plastics construction." AS 4132.3
Refer page 19,20 Section 3.7.4 to 3.8.1
Please post your results
Regards
Rob.

 

Sorry leegrace,....have just seen your diagram...the testing method puts a different light on things.
I'd add Karstens foam wedge to the top only to spread the load. I wouldn't use the foam on the bottom as this side will be under compression with your required testing method.
......but its not really how bulkheads are loaded in relation to the hull
Cheers
Rob