Will carbon layers help torsional stiffness of laminate?

[flanajb]

Slightly off topic, but I am making a rack for my bike forks to hold a 5 litre pannier bag and was planning on using 2 * layers of 1.5mm aeroply and a number of layers of carbon / fibreglass and I wondered whether using fibreglass or carbon fibre will help to make the end product torsionally stiff or is there nothing to be gained?

 

[MusicMan]

yes there is with carbon fibre, not much with fibreglass as the stiffness is not very different from wood for the same volume.

But you will get more stiffness still if you make it as a closed box shape, like box section tubing (even rectangular).

 

[flanajb]

Ok thanks. I cannot do a box section and I was just planning on flat laminates to give me a 4mm thick section.

 

[MusicMan]

If that is all the space you have, then carbon fibre laminate is your best bet.

 

[flanajb]

Thanks

 

[profchris]

In model making shops I've seen very thin square section carbon tube, probably less than 4mm. A few of these side by side, with carbon front and back, should be very stiff and strong. Worth considering?