Need help choosing materials for my design.

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#1

I’m building a prototype with a set of leaf springs for a piece of sporting equipment.

My design:
Each “leaf” will be about 1.5" wide, 12" long, and about .040" thick (I’ve been using three layers of 9oz. uni-directional CF for each leaf). The spring itself will have around 7 leafs and will be roughly semi-circular in shape. Each spring will have a working load of 30 to 40 lbs.

My questions:

Can someone recommend an epoxy system for this design?

Given this is a piece of sporting equipment, the springs will see a range of temperatures from baking hot to freezing cold.

I used Huntsman Araldrite GY 6010 in my first attempt. I left a part in the sun for a little bit and it went totally soft. I’m a newbie and didn’t know anything about Tg until reading some threads in this forum this morning.

Can a kitchen oven be used for curing small parts without any unfavorable consequences?

I don’t have an oven (other than the one in the kitchen) but could build a simple one one if need be. Curing at RT would be ideal…if possible.

Can someone recommend a uni-directional CF to use for this design?

I’ve used two different 9 oz fabrics so far. The 1st was woven (over and under) a thin piece of (plastic?) thread. This proved to be weak where the CF lapped the thread.

The 2nd was bonded to a thin piece of (hot melt plastic?) thread on one side of the fabric. I experienced a lot of loose fibers on the side that wasn’t bonded to the thread. It was difficult to spread epoxy on this side without disturbing the lay of fiber.

I’m thinking “sewn” fabric may be the way to go…or pre-preg without any binder other than the epoxy. Any thoughts?

#2

Prepreg would be ideal. Clean to use, but you will need an oven which you can control.

On the resin used: You only mention the resin, not the hardener. I have about 25 hardeners listed as “recommended” for GY6010. All give different properties…

On your kitchen oven: I would not take the risk, actually. Building a simple oven can be as simple as a light bulb in a cardboard box. (not much control, but can reach high temperatures, even more if you line the cardboard with tin foil). That will set you back 10 USD at most. From there it goes upwards.

On the fiber:
In wet layup either a multiaxial or a glued UD would be the way to go. A good glued UD which has not been mishandled should be OK to use. Try and design your spring a bit too wide, so you can cut off the edge.

#3

The hardener I used is Huntsman Aradur 3374.

Can someone tell me where I might find a list of hardeners and their properties for the resin I mentioned? Or could someone recommend a resin/hardener system for the application I mentioned?

Also, does anyone know where I might find a simple temperature control switch for a homemade oven unit?

And finally…can someone recommend a good source for UD CF…either dry or pre-preg? I’m looking for a 9oz fabric on a 6" to 12" roll.