Composite Dynamics Stuff Initial Testing Plan

Factors to consider

• Bond gap

• Insert size

• Insert length

• Insert material

• Filler material

  • What material

  • What percentage

• Adhesive

• Oven Curing

• Surface Prep

  • Prep of carbon

  • Prep of aluminum

Open

Model of Parts in Carbon Fiber Pushrod

Control Group

We will be testing Carbon Fiber and Metal interface epoxy strength for our Carbon Fiber push rods. We want to find the optimal method for attaching these materials not only for push rods but for any future parts for the car.

For our control group we will start with the following:

• Bond gap - 0.008' or 0.20mm

• Insert OD - 0.367” or 9.32mm (Determined by ID of tube and Bond gap)

• Insert length - 1/2”

• Carbon Fiber Length - 4”

• Insert material - aluminum

• Filler material - none

• Adhesive - Loctite Hysol E‐120HP Epoxy (33 MPa for abraded aluminum)

• Oven Curing - none

• Surface Prep

  • Prep of carbon - the inner part will just be sanded and degreased

  • Prep of aluminum - inserts will be sanded with 300 grit, degreased

Steps

1. Create Aluminum inserts

   1. 0.008 in gap

   2. Leave shoulder length for Instron machine to grab

   3. Have a length of about 1/2” that will adhere to the inside of tube

2. Cut the Carbon Fiber tubes into about 4-inch sections

   1. The tubes are 6 feet long, so we can get at least 18 tests from one tube

3. Prep the surfaces

   1. The aluminum inserts will be sanded (~300 grit) and degreased (acetone)

   2. The CF inner part will be sanded (~300 grit) and degreased (acetone)

4. Add Epoxy

   1. Slather Loctite Hysol E‐120HP on the insert and inner part of CF tube

5. Insertion

   1. Slowly push insert into tube and let cure for 24 hours at room temperature

6. Testing

   1. After putting the insert into both sides of the tube, attach to Instron machine

   2. Pull until failure

7. Repeat 3 times

Variable Testing

Insert Length

We will increment by 1/4” since our math seems like we only need 0.5” of insert length. We will start at 0.5” and work our way up to 1.25”. We will see how much the length impacts the max force to test for redundancy.

Bond Gap

We are starting with a gap of 0.008” because research shows this is the ideal gap. We can decrease the gap to 0.006” and increase it to 0.010” and analyze the increase/decrease in strength.

Insert Material

We are going to start by using aluminum because of the low weight, however the strength is less than steel and may be scratched by steel rod end. We may even have to use a Helicoil to interface the two parts. We can change the insert material to steel to see if the strength increase and less work is worth the extra weight.

Adhesive

We are going to start with slathering adhesive on the insert and inner part of the CF tube. We will also test injecting adhesive straight into the tube with the insert already in the CF tube. Whichever method yields the best strength/if there is any noticeable difference, we will go with that method.

We will also test if oven curing is a necessary/viable option for our epoxy. We are going to start with room temperature curing for our control, and then test how heat curing affects the strength of the bond.

Filler

We are going to try without filler first. We may test with silica or glass beads infused into the epoxy. This would complicate the process since we would have to determine the bead to epoxy ratio and injecting would be very difficult, so we would have to use slather-and-push method to connect the insert. The point of filler is to make sure the insert and tube are concentric creating equal stress on the epoxy bond.