Improve Strength of Composites Tube w/+45/-45 Layup

[mhajinaw]

Homework Statement

Given a composites tube made up of +45 layup. The tube is subjected to positive torque. Suggest a new layup that will improve the strength of the tube when subject to clockwise and anti-clockwise torque. Motivate your choice.

Homework Equations

The Attempt at a Solution

I think the layup should be [+45/-45] as this will provide shear strength on both torque directions. But should it be symmetry as well?

 

[CWatters]

Not my field but yes you want layers that are + and -45.

Google found this..

http://library.propdesigner.co.uk/tubes.pdf

Tubes carrying torsional loads should have there innermost ply of carbon fibre applied so that it is in compression and there outermost ply applied so that it is in tension. This will prevent the tube failing by torsional delimitation.

This implies if you just had two layers the tube would be stronger in one direction than the other - so you need more than just two layers.

I don't know if it needs to be symmetric.