We are attempting to replace spring steel sheet with kevlar composite

[aero18]

Kevlar replacement:

We have looked into spring steel and are considering kevlar sheets to wind up a panel/sheet nearly 26" width on to a 4"-5" diameter tube.

The panel coils up with a tensioning spring and feeds out a odd shape track to define a aerodynamic surface.

Can some one help consult on this project?

We wish to design a lighter weight composite sheet.. yet a 3'x26" spring steel panel coiling up is going to be too heavy for the application.

Any ideas would be helpful.. cold weather and high fatigue conditions exist.

 

[Compositepro]

Carbon fiber composite will be the closest you can get to spring steel while saving weight. Kevlar has less than half the modulus of steel and has really poor compressive properties, including high compressive creep.

 

[aero18]

We need very high rigidity about the axis of coiling and flexability in the tangential direction.

So, should be use a specialty design..

like tubing of carbon fiber.. composite tubes.. interlocked between two very thin sheet or possibly a fabric of kevlar?

we need to wind up the panel on a 4" tube... and resist about a .2psi normal load without extreme flexure

The panel will be in an arc'd shape with wind up to 120mph incident upon the face. or .2psi near

The sheet panel is 26" width in the axial direction and about 34" length along the panel feed out direciton.. like a roll top desk.. feeds out into a parabolic profile.


Drawings may be appropriate

Mark

 

[berkshire]

I think you had better post some drawings of what you are designing.
This sounds like an extendible wing coming out like a steel measuring tape.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[aero18]

The design is for a Fairing to block off a radiator of a Class 8 Tractor...

For class 8 trucks hood retro fit kit that is.

on the L and Right of the hood next to the radiator a sheet of spring steel uncoils into a aerodynamic shape..

it cuts off a portion of the radiator to the flow and slips the air past....

you save anywhere from 10-20HP at top speeds and .5 to 1Gallon of diesel every hour of top speed operation

Long Haul trucks may use this Fairing design for aerodynamic reasons... DOE Grant proposed for the design is in the works also.

Coiling up the sheet just like a tape measure .. yes....

The sheet thickness determines the outer skin stress when the coiled up metal/composite is wound around a vertically oriented tube on the L and Right of the Radiator

 

[berkshire]

So as I see this You are using this as a partial shutter and to radius the edge of the radiator for airflow reasons, I am presuming this material will be extended on a track to keep the shape you want.
This sounds like a job for a single skin of carbon fiber using a toughened epoxy resin.
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[aero18]

yes.. that sounds good.. but will a sheet coil up on a spooler like the old style film feed cameras?

I am thinking that the inside portion of the skin will be in compression too highly possibly

and the sheet must be 26" x 40" in size.. without flexing too much from wind loads of .2psi normal to the surface

 

[berkshire]

Ok 90 miles per hour gives a wind load of 0.2014 lbs per square inch.
It would sound as though you are going to need some kind of support rails to prevent the pressure of the wind from capsizing the sheet when it is extended.
I think the difficulty you are going to have will be a trade off. When the sheet is flexible enough to roll around the cylinder, it will be too flexible to do what you want. When it is stiff enough to do what you want ,it will not roll around the cylinder.
I do not know your cost requirements, but you could look at .015" titanium sheet. It can be rolled to fit your cylinder and has good spring back capability
B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[Hansmeister]

If you make an unsymmetrical laminate, it will curl up on its own (using an elevated temperature cure).

 

[aero18]

yes. there are quide pathes on edges .. yet the mid section can not deflect greatly

we understand the balance of design

now.. can we use some unidirectional fabric with kevlar in resin?

make the fibers of kevlar run axial direction to gain rigidity and radial direction would flex around the cylinder.