Composite pipe to resist torsional loading
Composite pipe to resist torsional loading
(OP)
Hi,
I am looking to replace an existing steel pipe with a composite pipe for the steering shaft for an 86ft Steel motor barge.
I need to do this as this piece needs to be lightweight and removable.
Any suggestions as to suitable materials would be greatly appreciated.
Our main concern is related to the torsional loading of such a pipe.
Thanks
I am looking to replace an existing steel pipe with a composite pipe for the steering shaft for an 86ft Steel motor barge.
I need to do this as this piece needs to be lightweight and removable.
Any suggestions as to suitable materials would be greatly appreciated.
Our main concern is related to the torsional loading of such a pipe.
Thanks





RE: Composite pipe to resist torsional loading
What is the torsional loading and what size is your steel pipe at present?
desertfox
RE: Composite pipe to resist torsional loading
The torsional loading is provided by the water resistance on the rudder, probably 1m2 which can be turned into the oncoming water flow to about 30degrees. The vessel speed is approximately 8mph. The max loading occurs when the vessel is in reverse.
Unfortunately I cannot give you any numrical data for the scale of the loading at this stage.
The shaft connects the rudder to the chain attached to the steering wheel and is about 4m in length and 20cm in diameter. Thickness curently unknown.
Thanks
RE: Composite pipe to resist torsional loading
We really need the pipe size as well as the loading, however if you can tell us the pipe thickness we could give you an equivalent polar moment of inertia in various materials to that which you have with the steel one at present.
desertfox
RE: Composite pipe to resist torsional loading
cheers
RE: Composite pipe to resist torsional loading
I'll run some numbers and post later, in the mean time you might like to look at this:-
http:/
desertfox
RE: Composite pipe to resist torsional loading
If the shaft is impacted by debris that will break any surface protection and again let the water in.
Once the water gets in it will delaminate and fall to bits.
Metal is probably best.
RE: Composite pipe to resist torsional loading
Thanks for the reply, the existing shaft runs from the engine room to the steering gear room where it connects with the rudder post and so the entire shaft is inside the vessel and does not come into contact with water (if it does we have sunk!)
Cheers,
Marine10
RE: Composite pipe to resist torsional loading
gwolf.
RE: Composite pipe to resist torsional loading
Layup should be with fibers oriented mostly at 45° to the tube axis. However, while that should exceed the steel tube's torsional capacity, it will give a deficit for the bending properties.
A tube of 200 mm x 5 mm wall in E-glass should have a reasonably well factored allowable torsion of, say, 75 kNm.
If cost is less a factor than weight then a carbon tube made of something like Panex 33 fiber/epoxy should be about half the weight.
Close attention is needed for design of attachment fittings.
RE: Composite pipe to resist torsional loading
RE: Composite pipe to resist torsional loading
Mike Halloran
Pembroke Pines, FL, USA
RE: Composite pipe to resist torsional loading
I thought that was what he was trying to replace,
God knows why.
B.E.
RE: Composite pipe to resist torsional loading
Thinking out of the box here but might a cored laminate reduce the weight and provide the necessary stiffness?
RE: Composite pipe to resist torsional loading
I personally don't see any benefit in going to a sandwich.
Compositepro is right about glass's stiffness being low. (Basalt is a bit better but not that much.) The only way to match a steel part's stiffness with composite is to use carbon. However, for a tube that's not in bending, stiffness is unlikely to be a major factor. A glass tube with a lot of 45° plies is likely to have a stiffness in torsion about 1/7th of a steel tube's, maybe less depending on exact layup.
However, for a shaft dominated by torsion you should still be able to take a lot of weight out with glass, probably about 40% to 50%, and with carbon maybe 60% to 70%.
Some info on the steel used for the original part might help refine these sorts of very, very rough (gu)estimates.
RE: Composite pipe to resist torsional loading
Aliene Elkins
Advanced Materials Group
The ET Horn Company
www.ethorn.com