Is this right then? Carbon fiber is floppy laterally but very resistant to stretching. Fabric made of CF is flexible. Resin gets into the gaps in the weave and hardens. When a force attempts to bend the fiber, it would have to stretch to get around the bit of resin. It doesn’t want to stretch and so the overall effect is rigidity. In that way, the resin doesn’t have to be particularly resistant to anything apart from crush, and the strength of the overall product rests with CFs resistance to stretch/break when getting around a hard thing?
They key point about carbon fibre, as pointed out, is its tensile strength. It is silly strong. The key metric is it’s modulus. Carbon fibre comes in a number of grades, standard, intermediate, high and ultra-high modulus. (The prices rise very rapidly through the range.) The modulus through this range is from less than 265GPa to in excess of 440Gpa. As a comparison, hemp fibre is about 35 and steel varies in the range 200 to 240.
As noted above, really good carbon layouts use pre-preg - with is carbon (typically unidirectional) that is impregnated with a very highly controlled amount of resin, and with which you get the highest ratio of carbon to resin whilst ensuring a fully bonded fibre. The job of the resin is to glue the fibres together into a bulk. It isn’t to add strength - in fact it reduces strength. You won’t get the full strength of the raw fibre in a layup, but you can get a good fraction (say 1/4 to well over 1/2 depending upon directionality).
Carbon is great in tension, but unidirectional layups have very low strength 90 degrees to the layup, and that leads to the art of designing a high strength component. Often you will use a woven cloth, compromising ultimate strength for bi-directional strength. But as a rough comparison, you get something with say one third to up the same strength as a similar item made out of high quality steel, but with the density of carbon. 1.6 versus 7.8 - close to a 5 times. So say 2 to 5 times the strength to weight ratio of steel. And that is for solid items. The ability to create laminates, such a foam core and honeycomb structures leads to some ridiculously strong and lightweight constructions. Now that the price is (just) affordable just about any high end racing yacht is end to end carbon. Some classes still restrict its use to keep costs down, but at the top end it is all carbon.
Everything you can seen in this picture is carbon fibre except the people and the water.
Have concrete and carbon fiber been mixed?
In reinforced concrete, steel is added to compensate for concrete’s high compressive but low tensile and shear strength. Could steel be replaced by carbon fiber?
Or is the price of carbon fiber too high for general construction applications?