Recently we visited Andre Cocquyt, the GRP Guru, in Maine to learn more about the infusion process and start building a very unique Trimaran hull. We will share more on the wealth of knowledge we gained on infusion in a later post, but today we will discuss hand layup. We used CPD epoxy resins to hand layup a curved portion of the hull with carbon fiber (photo to left).
Andre taught us some tricks to ensuring that we were wetting out carbon fiber properly. He pointed out the nuances of working with fibers other than trusty fiberglass as knitted reinforcements and taught us some important lessons in making sure you have a strong, light and evenly laminated carbon fiber part.
Tip #1 - You can Always add More Resin
Andre has a wonderful way of teaching, by letting you fail, maybe even setting you up for it. When we were asked to hand lay up some practice panels he brought over ten times the amount of resin needed to fully saturate our carbon fiber. He did this to teach us a valuable lesson; it is a lot easier to add resin to your project than take it away. Especially since weight is often a crucial component to your structural laminate, start with less and work your way up if you need more. If you're a beginner start with a slower epoxy hardener to ensure you have enough time to add resin before the cure process begins.
Tip #2 - Wet out from the Bottom Up
First instinct would tell you to lay out your core and knitted reinforcement the way you want it, then pour epoxy on top to start laminating. While this often works with fiberglass which is a lot easier to saturate, it is not the best strategy for carbon fiber and epoxy. There is a simple reason why, you cannot fix what you cannot see. When you pour resin on top of your carbon fiber you cannot tell if it has made it all they way through the fibers to the other side. If you start from the bottom and use squeegees or metal rollers to pull resin through the fabric towards you, it is easy to see when the top surface has been wet out or if you have a dry area.
Tip # - Use Peel Ply to Audit your Layup
If you are unsure if your layup is consistent (and probably even if you think it is) use a layer of peel ply on top of the carbon to audit your work. The black color of carbon fiber makes it difficult to determine if it has been evenly saturated, unlike fiberglass which turns clear as an indicator. Using peel ply on top of your part gives you a lighter color substrate that you can roll with a metal roller or squeegee to see where you might have areas of too much or too little epoxy resin. The amazing thing with peel ply is you can pour resin on top of it and roll or squeegee to saturate the carbon fiber more if needed.
If you want to learn more about epoxy products excellent for use in laminating with carbon fiber check out CPD 4222A and view the Technical Data Bulletin Here.
What other tips have found helpful when working with carbon fiber? Share with us!