RC Chassis Plate?

[stormridersp]

I’m currently investing on equipment so it seems to be the right time and right place to ask.

My first attempt couldnt be easier; I’m planning to make a 3mm to 4mm thick carbon fiber plate, about the size of an A3 print paper, then cut it with my dremel 300 into smaller R/C parts. My second attempt will be to create a mold to make the same R/C’s chassis bathtub, about 2mm to 3mm thick.

The most affordable carbon fiber sheet I’ve found so far here in Brasil is a 2/2 twill, 3k, 0,2Kg/m2. I’m also planning on using a higher heat resistance epoxi resin.

A few questions:
1- How many layers of carbon fiber do I have to use in order to achive those desired thickness?
2- Is it possible to alternate layers of carbon fiber and fiberglass? Would that reduce significantly the final product performance?
3- At my first attempt, I’m thinking about trying the resin hand laying technique, cause its my first contact ever with composites and also because I can’t afford all the vacuum related equipment plus carbon textile all at once. Would this technique also reduce the final product’s performance too much?

To build the chassis bathtube and planning on trying a vacuum bagging or infusion, following one of the great tutorials found here at composite central.

Cheers

[wyowindworks]

A few questions:
1- How many layers of carbon fiber do I have to use in order to achive those desired thickness?
2- Is it possible to alternate layers of carbon fiber and fiberglass? Would that reduce significantly the final product performance?
3- At my first attempt, I’m thinking about trying the resin hand laying technique, cause its my first contact ever with composites and also because I can’t afford all the vacuum related equipment plus carbon textile all at once. Would this technique also reduce the final product’s performance too much?

To build the chassis bathtube and planning on trying a vacuum bagging or infusion, following one of the great tutorials found here at composite central.

Cheers

#1 - It’s going to take about 6 layers of 5.7 ounce carbon to get to 2mm with a hand layup (40% Vf)
#2 - Putting glass in the middle is a simple way to reduce the cost of the laminate. You would want to put the carbon on the outside and the glass on the inside to maximize the stiffness of the laminate. I would do the orientation at 0/90, +/-45, 0/90, 0,90, +/-45, 0/90 to maximize the stability of the panel.
#3 - You can make them with a hand layup and get adequate performace. Using a vacuum bag or press will allow you put more fiber into the same thickness. If you used a vacuum bag to get a 50% Vf then you have to add 2 more layers to get to 2mm. The vacuum bagged panel would weigh more than a non-bagged panel of equal thickness (fiber is more dense than resin). The performace of a non-bagged panel would be less than one that is bagged. But a non-bagged panel many still exceed your requirements. A little testing will reveal a lot.

[herman]

Also instead of vacuum bagging, you could press mould sheets, or even bath tubs. The only extra things you need are a top sheet (both top and bottom mould should be stiff and strong) and some clamps.

Courser carbon (6K, 12K in heavier weights are cheaper, as well as multiaxials). If you can get them, but I am sure there will be a supplier in Brasil.

[ryan]

#2 - Putting glass in the middle is a simple way to reduce the cost of the laminate. You would want to put the carbon on the outside and the glass on the inside to maximize the stiffness of the laminate. I would do the orientation at 0/90, +/-45, 0/90, 0,90, +/-45, 0/90 to maximize the stability of the panel.

I would keep the first half of the layup Herman said, but make it symmetrical to avoid warp and “springback”: 0/90, +/-45, 0/90, 90/0, -/+45, 90/0. Make sense?

[wyowindworks]

I would keep the first half of the layup Herman said, but make it symmetrical to avoid warp and “springback”: 0/90, +/-45, 0/90, 90/0, -/+45, 90/0. Make sense?

If the fabric isn’t balance, then the layup you describe would create instability. If it’s balanced then it wouldn’t matter. You want the fiber orientation to be an exact mirror from the middle of the stack out. This will guarantee that there is an equal amount of fiber in each direction on both faces to resist cupping and bowing. If the fabric isn’t balanced the middle layers could both be 90/0 but the outside ones must mirror each other. You would need to use a balanced fabric for the +/-45 layers. If the fabric is unbalance, the process is risky, but the warp fibers should all be pointing the same direct and the fill should be pointing the same direction (mirror). If the bias cut fabrics are flipped the panel WILL warp. Again, the whole process is easier if you use a balance fabric.

[wings]

If you plan to design the chassis as a plate remember that for an RC car of that size, torsional stiffness is a design driver; than you have to place the ±45° layer outside
Probably you will face the problem of holes for screws (unless you will use glued inserts); carbon fiber is very critical in this area, since cracks will be present at hole edges, even if you disperse ±45° layers in the thickness of the plate: take care to place ,around holes, some layers of glass since it works as stress relief.
For the bathub design, things are better for stiffnesses; maybe in this case you have room to place somewhere a light core in order to make a sandwich structure (for holes ,what said above is still valid) .
Depending on the type of RC cars you are designing, in the case of f1 or lemans protos like models, the underside is critical for continuous hitting and skimming with the track; place there a layers of Kevlar or at least carbo/kevlar to protect the chassis.