Carbon Fiber Fabrication

A lot of hands on work is happening over the summer! 
On the past couple of days, we fabricated a small, 3-layer carbon fiber plate to test its material properties and gain experience in the fabrication process. It was our first time fabricating a composite part!

This picture shows the end product (a carbon fiber plate) cut into 3 parts.

We started with a foam mold that we wish to prepare the carbon fiber composite on so it conforms to the shape of the foam. In this exercise, we use a flat foam surface, but eventually we will be doing this process on foam in the shape of our car.

First, we prepared the mold.
 We applied an epoxy mixture on a foam mold *quickly* as it only had 20 minutes until it began hardening. 

 The surface looking smooth and glossy!
We put it in an oven overnight with a temperature set at 50°C to speed up the cure time.

The next morning:
 We sanded & waxed the surface coating multiple times to make it smooth. This is the surface on which we will prepare the carbon fiber composite part. To start, we apply a few layers of mold release on the surface coating, which prevents the carbon fiber from adhering to it as it cures.

 We then prepared the second mixture, an epoxy resin that we will use to harden and bond the 3 carbon fiber sheets together. The picture above shows us degassing the mixture in a vacuum.

The picture above shows us drawing the resin through the carbon fiber sheets, where the resin is sucked up from the cup in the bottom-right corner, drawn through the carbon fiber layers, and into the resin trap (the large upright cylinder). This process is called Vacuum Assisted Resin Transfer Molding (VARTM).

 Watching the resin flow..

We left the setup for the night and when we came in the next day... 
 We didn't do a good job sealing it so there were air bubbles in the vacuum bag. As a result, there are some small dimples on the end product.

Lesson learnt: We'll use more tapes and make sure we seal it perfectly the next time.

If we look at the carbon fiber plate closely:

This is the side facing the surface coating on the foam:

This is the side facing the peel ply:

Although the carbon fiber plates looked nice on the outside, we will test them on a materials testing machine to see if its properties are up to our expectation.