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.

Our first solar cell encapsulation experience!
Third try - Second try - First try

Behind the scenes:
Tedlar backsheet - EVA film - 1/3 solar cell - EVA film - Teflon FEP film

Covered with a couple layers of breathers and vacuum bagging film, and sealed, they're all set to be baked under air tight condition!

Temperature: 180°F, Pressure: 14psi, Countdown: 30 minutes

We failed on our first try :( 
Reason of failure is shown in the picture below.

Second try: We shifted the thru-bag vacuum connector so that it doesn't sit on top of the solar cell...and we baked them for 45 minutes..but we failed again! 
We found out that the temperature range of the top film is up to 205°F, but due to the temperature fluctuation of the toaster oven, the temperature sometimes exceeds 205°F. We suspected that this caused the formation of the dimples. (Sorry if this picture ruined your appetite) 

Third try: 
Temperature: 175°F, bake time: 30 minutes, cool down: 21 minutes.
This time the temperature never exceeded 205°F and we succeeded!!!
No bubbles, dimples almost nonexistent.

In the near future we will encapsulate the entire cell instead of just one third the cell. We will also sandwich them with two aluminium plates. 
While waiting for the materials for encapsulation to arrive, we practiced cutting solar cells using a diamond tip glass cutter.


The cut wasn't perfect, but we were happy because it looked much better compared to our first try! (Refer to picture below)

Practice leads to perfection!