Plate Fabrication

Composite Frame Design and Fabrication:

The frame is to be made of carbon fiber laid over Core-cell Foam

In order to simulate this process at a much lower cost, fiberglass over blue foam is being used.

Here is a video that was made by a previous senior design group explaining the fiberglassing process, in this case for a hydrofoil, but the general process is the same. (Ctrl + click to activate link in word doc. Regular click to activate link in PDF)http://youtu.be/WiN3WTp8Smc

In lieu of having the time/set up to run a vacuum bagging system, I started to get some practice in working with both the fiberglass and the resin required to harden it by first using a fast acting resin and hardener combo specifically designed for automotive purposes.

This sets up incredibly quickly which leaves very little working time, making it very difficult to get a smooth, even finish.  This resin is designed to be used more as a gap filler and reinforcer than a true coating, as the instructions involve significant sanding and finishing work.  

As such, the finished bars look and feel chunky and don’t really conform to the exact profile of the blocks they are wrapped around as the resin started to set before the air could be worked out. Pictured here are 2 “finished” blocks.  

They are dry as the resin takes about 20-25 minutes to cure. The darker piece has two sheets of fiberglass and the resin was applied much more liberally. The lighter colored block has only one layer of fiberglass and had the resin spread very thin.

2

As the automotive resin worked way too fast, I also attempted to work with a slower resin.  This gave me more time to work with the part, helping to remove air bubbles and achieve a better finish, but as I worked my way around the part, the resin entered into a very tacky phase that the automotive resin seemed to skip.  

This made the fiberglass almost impossible to work with as any part of the block that I touched stuck to my gloves and it became a challenge to just set the part down without damaging it, much less improving the finish.  It is pictured here as it is still drying, as this particular resin takes approximately 2 hours to cure.

This process taught me that we need to choose a resin and hardener combo that gives us plenty of time to work with the fiberglass/carbon fiber to get it to conform to our frame exactly without setting up or becoming overly tacky before we are done manipulating it.

It is also hoped that a higher quality carbon fiber than the cheap but effective piece of fiberglass that came with my automotive kit will show significantly less fraying and that will be a non-issue while we are fabricating our plates.

More practice is needed, especially on a larger scale, but this is a step in the right direction.  

Owen Accas Team 13211 Plate Fabrication2012-11-15