Which has more tensil strength graphite or carbon fiber?

Question

IF a study was conducted to see if graphite and carbon fiber had the same tensil strength which would be the stronger of the two. They both use the same resin and are both preimpregnated with the resin and cooked on a tool at 70 psi of nitrogen pressure in an autoclave for two hours at 350 degrees. Which is stronger? Plus they both have the same weave pattern, which is a plain weave.

I work in the aerospace industry, I was asking the question to see what results would come about. There is a process were the carbon and the graphite are produced. The first stage that is made would be the carbon fiber which is cured around 1500 degrees f and the graphite fiber is cured around 3000 degrees f. therefore making the graphite fiber stronger than the carbon fiber that is why in the aerospace industry the graphite is chosen over the carbon fiber and kevlar. The graphite is a material that will absorb the resin into the fibers which makes it stronger, the kevlar on the other had is a non porous material so the resin creates a shape around the kevlar which makes the kevlar disbond easier from the shape that it is created to. the carbon fiber on the other hand still absorbs the resin to help keep the shape and strenght but longgevity is a factor with the carbon fiber since it is the first stage that you get to before the graphite. I just asked the ? to create a discussion.

Answer 1

Graphite is made of parallel sheets of hexagonal graphite structure, which is why it's so slippery (and makes a good lubricant and drawing material). Carbon fiber is formed when the graphite rolls into a tube.

The bonds between carbon atoms are the same in either case, so the only differences in tensile strength would come from the manner in which the carbon can bond to the resin. Graphite forms sheets, where carbon fiber forms tubes.

I would expect the carbon fiber to bond to the resin more strongly because the resin could completely surround each thread, leading to more efficient transfer of stress from the weaker fibers to the stronger fibers. Thus, I would expect to the carbon fiber composite to have the higher tensile strength.

Answer 2

Carbon Fiber. Graphite CAN be very, very weak. It depends on how the molecules are aligned. It's cellular structure is like a cracker, with many flat layers. If you have forces pulling parallel to the layers, it can be very strong. However, if you line it up so the forces pull the layers apart, it's extremely weak.