Talk Composites - The Forum for Advanced Composites

how to define number of layers

http://www.talkcomposites.com/Topic14891.aspx

By tomzi1234 - 2/2/2015 11:36:39 AM

hi

does anyone have answer to how to define nr. of layers to obtain desired strength of object.

i would like to do seat post tube for my MTB.
so how to define what would be the minimum amount of layers that tube will still support my weight and not to have too much of not needed weight.

i know there is no 100% accurate way, but at least a point to start
By drumbum675 - 4/5/2015 4:50:05 AM

A seat post is the last part I would make if I had never made tubes.  A broken, sharp seat post where the sun don't shine is not good. If you do decide to do it I would:

Calculate the thickness of of the carbon fiber required.

Lathe down an aluminum rod as your mold.

The diameter of the aluminum rod plus the calculated thickness of the carbon fiber will equal your outside diameter.  So if you measure the outside diameter of a seatpost and subtract the required carbon thickness that is what you need to lathe your mold to.

Layup prepreg or OOA prepreg alternating between vertical, horizontal and 45 degrees both ways.  I would build up the lower section where it clamps in, several layers thicker.

Bag it and cure in autoclave or oven.

Trim to desired length.

You wont have a glossy part, but you can clear it if that is the look you want.