Talk Composites - The Forum for Advanced Composites

bonded sheet strengths

http://www.talkcomposites.com/Topic15641.aspx

By brucethemoose - 3/16/2015 10:11:01 AM

Hi people, brand new on here and got a question for those who may know. I have aproject for a new manufacturing idea based on carbon fibre , I use the term loosely What I need to know is.

Imagine two circular sheets of fibre bonded together, using whatever materials best for the job.

When standing on its edge What would the compessive strength of this bonded disc in kilos before buckling or breaking.

Based on discs of 700mm diameter and 900 mm in diameter.

ANY info would be greatly appreciated not an idiot but the simpler the better for my inexperience head

regards

brucethemoose 
By Dravis - 3/16/2015 11:21:21 AM

This question is impossible to answer from the given information.. Doze


I have built CF "disc-wheels" using two very  "flat cone-shaped" sheets of Carbon-fibre-Epoxy bound composite. They were bonded using Permabond, both at the centre and around the edge, to a CF wheel rim.

The first set of  "wheels" were used and tested to destruction on a cycle-cross bike..   The rider weighed around 80 kg .. but the "impulse" loads from riding on rough tracks would have been much higher. The "cones" were 1 layer of 200 gsm twill + 1 layer of 300gsm Biaxial CF.   Destruction occurred because of failure of the bonding to the aluminium wheel hub.

A single free-standing 700 mm diameter disc of CF reinforced composite WILL bend and buckle under a very light load.. 

Two pieces of 2x200gsm twill fabric with 5 mm of Aluminium Honeycomb (small cell grade 5000 alu) in between will easily support more than 75 kg (my weight.. ) on the edge .... no visible distortion at all.

The piece i tested is 7 cm tall and 5 cm wide, and weighs 5 grams ... Cool  It did not fail, even though I have already pre-buckled one side with an indentation,  caused by testing compressive strength by putting 75 kg/sq-cm of localized pressure on it.  This caused a 0,7 mm depression in the laminate.