This feels such a dumb question ... on a post elsewhere someone commented that painted carbon fibre was lighter than unpainted, as the resin that had to cover the fibre to ensure it was waterproof was heavier than the equivalent painted.
So ... why isn't every bit of carbon fibre on an F1 car painted ?
You have a link to the original quote? Doesn't seem right, but if they were talking in the context of comparing a gel coat cured part with a raw carbon part which is then painted maybe there could be some truth.
the first question here is -what do you mean by waterproof?
would it be necessary a cf panel is not letting any water through ? I can understand in bonded structure ,sandwich material -you don´t want to have water entering the structure espeicially with kevlar /nomex in the equation .But generally all epoxies
have a certain capacity to embed water especially boiling water can be a problem.modifying the resins characteristics to the worse...
Is acoat of paint water tight by definition or also capable to contain water or even let it though?
High performance composite parts are typically fabricated from what is called prepreg. This consists of the fibers (almost always coated with a proprietary film to aid adhesion to the resin chosen) and a very carefully controlled fixed amount of partially cured resin. These prepregs are supplied by manufacturers. The resin is viscous and tacky, which allows the fibers to be draped over complex shaped tools. An autoclave heat cure completely polymerizes the resin.
The controlled amount of resin allows the maximum structural performance from the laminate without excessive weight. The side of the laminate cured against a smooth tool gives a finish as smooth as the tool and the part is completely full of resin and fibers - that is, it's waterproof. For sandwich panels, each manufacturer has processing tricks to ensure that no water gets into the sandwich cores.
Extra resin applied to the surface of the tool is usually only done in laminates that are not as weight critical , such as composite cure tools for extra surface durability, in wet layups (resin applied by hand by the user to dry fibers) for which the resin amount isn't as accurate, or in layups whose surface will be sanded for more than just paint adhesion.
The post you can't find referring to waterproofing and gel coating was incorrect.
The choice to paint or not depends of how much graphics are needed for team and sponsor colors and names. Neither the paint nor the extra gel coat are required to waterproof the laminate.
Think some of the original question may of been lost in translation ?
But to answer the question its "mostly" no but depends what your comparing
Road car where you want the best finnish from the mould or the best base you can to apply paint to you can apply various types of surface films-basically pure pre preg resin with no cloth(sometimes a light film binder to hold it together) which is put in the mould before any material.
F1 you would never use a surface film but on the parts that are painted most parts will be 2-3 shot parts so the outer skins will of seen 90 psi and have a perfect finnish but with the none structural bodywork you have the choice of doing one shot,30 psi cook so as not to crush the core then correct the surface with filler
From my bicycling background - to get the fancy carbon fibre weave you see on road cars, a superficial cosmetic layer is carefully laid down and then clearcoated. This last layer usually does very little for strength, and probably adds weight. So by designing components and parts properly for strength, a light layer of paint probably about breaks even with getting a sexy carbon fibre look...
monsi wrote:This feels such a dumb question ... on a post elsewhere someone commented that painted carbon fibre was lighter than unpainted, as the resin that had to cover the fibre to ensure it was waterproof was heavier than the equivalent painted.
So ... why isn't every bit of carbon fibre on an F1 car painted ?
as far as I understand it the sun breaks down cf so it needs a protective layer, I guess an opaque paint can be thinner than a clear coat that offers the same protection. F1 parts probably don't last long enough for the sun to be an issue
langwadt wrote:..
as far as I understand it the sun breaks down cf so it needs a protective layer, I guess an opaque paint can be thinner than a clear coat that offers the same protection. F1 parts probably don't last long enough for the sun to be an issue
no, uv rays can break down some resins, not the carbon. uv resistance can be engineered into the resin if desired.
There are also very thin sprays, 3m 303 is one I think. it has to be reapplied every once in a while. it gives some UV protection... Some folks wax their bare carbon.
