Howdy,
In learning all this I have heard of the pre-preg CF. From what I can guess it does not unravel as easy?
I really do not have a clear understanding of the fabrics properties and how it really can make things easier.
I would love to get to the experience level of making a Carbon Fiber race seat, and with that I would want to use that wishbone lay on the first layer, down the middle of the seat.
Is this where I could benefit with pre preg?

p.s. someone please fix my thread header.... benefit..



If Brute Force Isn''''t working your not using enough...

Hi,

Prepreg (some-times called 'dry' carbon) is a very different beast to infusion or wet-layup, essentially the material is a 'tacky' cloth with the resin already impregnated, this raw material is stored frozen and can have a working time (out of the freezer) of anywhere between 2hours and 6 months depending on the resin formulation. The prepreg is cut to shape and laid into the mould by hand ensuring that it follows the contours of the mould properly. Once the material has been laid the part is then vacuum bagged and cured in either an oven or an autoclave. To get a pin-hole free surface finish with standard prepreg materials you must use an autoclave (applies pressure to the laminate as well as heat, very expensive machines) or a conventional oven with our easy-preg system which will again provide a void-free finish, it is a common misconception that prepreg parts have a satin or matte surface finish, this is simply not true, it will take on the finish of the mould like any other composites moulding.

In answer to your questions; Yes it does cut neatly without fraying and also stays very straight; another way to achieve this is to use the Profinish cloth with infusion or wet-layup.
The other potential benefits of prepreg are; clean processing, product consistency and strength. Prepreg is still seen as the ultimate in performance composites however it is increasingly being replaced by infusion processing especially for lager structures.

Paul Statham
Easy Composites / Carbon Mods - Technical

I have to agree with Paul on the profinish carbon.  Especially if you dont need ultimate strength or ultimate lightness that pre-preg gives, then resin infusion with profinish can be the best of both worlds at half the price...

I used profinish on a couple of my projects and it is great to cut without fraying.  It is not just great for a good cosmetic finish, but can be very good for complicated layups where you need to use multiple cuts in the fabric to lay up and or you are using small pieces of fabric.

If you look on this layup:


the stump on the right is only 7cm high and a few cm across.  It is layed around with profinish carbon as no way would normal fabric survive so well during the layup.

So although profinish can give you the consistant cosmetic appearance similar to pre-pregs, it can also make some complicated layups easier to do.

I've got pin holing in my pressure bagged scope mould Paul - Any ideas what I can do about it ? I wonder if a breather /peel ply inside might help ?

Steve

Hi Steve,

Sorry for the delay in getting back to you about this point, I know we've developed a new method for you now which is working a treat so this is somewhat a mute point but to help others out there, it's oftena  good idea to combine a pressure bag with a vacuum bag. The vacuum will help to get any trapped air out of the laminate whilst the pressure bag puts the real pressure on. This would probably help with the pin holes quite a bit.

Best regards, Matt

Matt Statham
Easy Composites / Carbon Mods - Technical Sales

I use your easypreg system and an aluminum mold, full vacuum with an active vacuum, and an oven but never able to get a pinhole free surface. Can you explain the difference between a pressure bag, and a vacuum bag? Any other tips would be appreciated. 

A vacuum bag you remove the air between mould surface and the bagging film, thus the air outside the bag forces the bag onto the mould.

Pressure bagging you in effect inflate a bag and directly apply pressure that way with an inflated bag.

Pinholes can be caused by a number of reasons. First make sure youve zero bridging.  Then a good bag and that you have the correct cure cycle.

Warren Penalver
Easy Composites / Carbon Mods - Technical Support Assistant