I think you need more practical experience before going to all the exotic materials. You also need a budget that says what the exotic materials are buying you for their cost. So how much lighter for how much money, and did you land up with something safer when it's elasticity before breaking is less then %10 compared to %40 percent for the square 1010 mild steel. These are not simple questions and you could probably build and start driving the car before you understand all the different exotics and their individual plusses and minuses. Which says build your first car the normal way people have experience and then use your own experience you have gained and consider the impact of the exotics.
Something I would note on the Carbon arm you are looking at is that the material it is made from is inappropriate for it's use. It may or may not contain unidirectional fibers inside. What I can see though is woven cloth. Half of the fibers are not going in a direction that you need ( you need some circling, but not nearly %50). THe fibers that travel lengthwise are woven so they are already buckled by nature, how much compression will they stand? I assume you have done the thing of standing on a beer can and then tapping it with your finger. Please do that if you haven't, it's one thing to hear that story and another to do it yourself.
Proper carbon materials are not woven and contain unidirectional fibers in one or more layers which are either lightly stitched or bonded together. I'm glad your doing testing, if you off the beaten path that's what you need to do to be responsible for yourself and other people. It's a lot of fun too. Remember to be careful when testing. I did some of this a long time ago and it quickly became obvious that fiberglass pieces of any size produce large loads and a lot of flex. Pretty quickly you are in a situation of being in a room with a hunter's bow pointed in random directions.
Having a desire to do better is what brings most of here to begin with. If you really want something better and are willing to do the extra work, you could consider building with round DOM 1020/1025 tubing. It's yield is considerably higher with reasonable failure modes etc.
There are good reasons to do things like custom uprights, if you can it would be great if the problem you solve here is useful to a wider community. It's fun to build your own stuff, it's really satisfying to build something a bunch of other people use too. Again, consider building with something like 6061 instead of the fancy stuff. Things like corrosion and fatigue life are real world issues. A car will not likely see the maintenance that an airplane or rocket will and it's exposed to more abuse and salt too.
The carbon arms are unidirectional with an outer layer of 45°. I have not built or designed anything without extensive testing. I have even put the Carbon under compression and did a break test (weighted drop) to test the real world situations like an object hitting them. They will also have an aramid lay up over the outside due to that testing. The pre gap for the epoxy is set by using a stepped custom made rod end. The tube id is gauged after sanding and the step is then matched. E120-HP is the epoxy.
7075 makes sense from a strength aspect. I can reduce the weight by 1/2lb+ by going with it instead of 6061. We dont have Saltspray issues here in Colorado but if we did I would test that too. They are going to be Hard Annodized too so that will cut down a bunch on the corrosion issuse. I am more worried about the HAB-8T bearings but i am accepting the fact that i will watch them and replace them as needed. No winter driving either
Yeah i like your guys idea to switch to DOM 1020 but i still cannot find it cheaper. The frame is actually on revision 16 so chaging material won’t make that big of a difference.
Thanks though. Added insight is always useful. I promise more pics once i get to the other computer tonight ; )