Carbon Fiber

[Jeff K.]

I've seen a lot of teams use carbon fiber in different parts of their bots. We recently acquired a composite sponsor, and were considering constructing the chassis and frame out of this composite material.

It would be totally offseason, and we would test it thoroughly before we ever decided to use it for an actual season.

I was wondering though if this is practical for FIRST.

Also, if the company were to actually make the chassis and frame, it would all be one piece, since they would mold it all together, not as seperate pieces and then connect them to each other with carbon fiber strips and resin.

[sanddrag]

I've never done it but I wouldn't recommend it. It's hard to beat a good TIG welded aluminum box tubing frame.

[Peter Matteson]

It depends on how you plan to do it. I tend to think that the time invested in doing a proper layup and autoclave or vacuum bag cure is a diminishing return for use in a FIRST bot. I believe many of the teams that use CF have used pre-formed structural shapes, for example Hyper (69) using hockey sticks in 2005. If the sponsor is say Easton or Reynolds you may be able to use their catalog shapes in this manner.

The problem will become joining other materials to your base after you mold it. Also the cost of the material could in fact be crippling. Remember you still have to account for the material cost in your $3500 additional materials budget.

Also it may just be heavier than a welded tubing or kitbot frame. I believe it was the 767 where they designed a composite tail to save weight and when all was said and done it weight virtually the same as an all aluminum one.

To sum up the ramble if you're serious look at the real trade offs before you do it. You make work yourself into a corner.

[Al Skierkiewicz]

As Peter stated, there are certain constraints that limit the materials. As a rule of thumb, exotic materials cannot be used. The test being are they available to everyone. If you make it will other teams be able to buy the same thing.

<R41> Additional Parts must be generally available from suppliers such that any other FIRST team, if it so
desires, may also obtain them at the same price. A specific device fabricated by a team from non-2006 Kit
materials does not have to be available to others; however, the materials it is made from must be available to
other teams.

[Gdeaver]

We have use FRP pultrusuions for our arm before. Worked out very well. As mentioned attachment points require different techniques than metal. Clamp thing onto a tube. We used carbon cloth to reinforce birch plywood. A coupler for a motor was made out of chopped carbon fiber and epoxy. You may have a problem with cost. The market price for carbon cloth is way up their. Also beware that certain prepeg resins are toxic and I wouldn't want to use them around students. Amine allergies are enough to worry about. Putting some fiber in your robot can be a good thing.

[Tytus Gerrish]

if you can do it do it it would be awesome. dont be afraid of new technology. embrace it and experment with it figure out the problems on the way and then tell us about it so it gets easier.

[=Martin=Taylor=]

We have never used CF in our frame but we have made our electronics boards out of it.

Yes it is light and yes it is strong but it is NASTY stuff. If you want to cut it or drill it you are going to have to purchase special bits and saws.

Also, depending on what type you use the edges will end up like razors. If you don't coat them in some type of resin they'll cut people and worse... electrical wires...

I have often thought that given the difficulty of using them it would be worth it to use conventional materials instead.

[KenWittlief]

I would say dont use CF.

The main reason is: your robot is really an engineering prototype. During the final stages of build and test, and at regionals and the championship it is very likely that

A. the robot will be seriously damage and will require extensive repairs (not only on the field, but you have to consider things like your crate being smashed, or dropped off a forklift from 6 feet in the air - it happens! )

2. You will want to make changes to your robot, possibly major changes.

For these two reasons its best to have a frame structure that is easy to repair and modify. Cutting, drilling and grinding on a CF frame in the pits at a regional would put hazardous materials into the air.

Carbon Fiber would be a good choice after the prototype stage of an engineering project. For example, after the year is over, and you have refined your design, and you want to make 1000 robots a year and sell them. At that point all the bugs would be worked out.

Unfortunately, FIRST robots never get to that part of the Engineering Design Cycle.

[Greg Perkins]

Team 84 built a good portion of their robot in 2004 out of carbon fibre. I believe their subframe was made of common materials though.

[Tytus Gerrish]

wOWH! wowh! a bunch of people arte saying what could go wrong. well anything can go wrong and many things can go right the fact is we dont know because nobody has built a CRP Frame before. and until somone does WITCH I ENCOURAGE! because it would be a great learning step in first for all of us. i see more good coming out of this than bad.

What is the worst that could happen? a problem arises and you teach yourself and the rest of us how to solve it.

Go for it

[Gdeaver]

There are other fabrics that can be used in composite construction. Kevlar cloth is good for vibration dampening and impact resistance. S2 fiberglass is also economic and close to the spec of low grade carbon. In high power rocketry my son and I used many hybrid construction methods and were very successful. Knowing what materials and where to use them is why aerospace composite engineers make some big bucks.

[Ben Piecuch]

Team 842 has used fiberglass for their robot chassis for several years now. It's thick and beefy fiberglass, but it seems to hold up very well. I would assume that Carbon Fiber frame rails would be quite similar in robustness.

From my experiences in designing around Carbon Fiber, the connections and interfaces with other components are always the toughest challenges. CF is so strong and can handle so much load, that the connections tend to be bigger and heavier than the metal component the CF replaced.

I love CF, as two of my road bicycles can prove. But I'm not quite sure the advantages it provides in the FIRST world outweigh its difficultly in use, and the obvious time constraint to design around it. YMMV, best of luck.

BEN

[Peter Matteson]

Originally Posted by Tytus Gerrish

wOWH! wowh! a bunch of people arte saying what could go wrong. well anything can go wrong and many things can go right the fact is we dont know because nobody has built a CRP Frame before. and until somone does WITCH I ENCOURAGE! because it would be a great learning step in first for all of us. i see more good coming out of this than bad.

What is the worst that could happen? a problem arises and you teach yourself and the rest of us how to solve it.

Go for it

I completely disagree.

So far this thread has been people with more experience giving their views on the issue. This includes difficulties that might arise and considerations that should be taken. All this should be done to determine if the product is worth the effort. Any business you work in you will see this happen not to necessarily discourage the individual from what they are trying to do but make sure they consider everything and go in well informed. This is why we have peer reviews and and concept reviews early in the design process where trade studies and feasabilty are discussed. In the end you make an informed decision. That is where we are leading this.

Pete

[KenWittlief]

What is the worst that could happen?

I dont know if many students are aware of this, but FIRST has a psuedo-official Prime Directive for mentors: Dont let you team fail to have the opportunity to compete (dont show up at an event with a robot that cannot / willnot function at all).

That would be the worst that can happen. You create a frame that ends up being damaged and you have no way to fix or replace it. You are not allowed to bring the resins on the aircraft. You are not allowing to fabricate new parts, or fix broken parts at an event because the chemicals and the dust are hazardous.

Your team ends up being spectators with a fancy statue on the playfield (that looks like a robot).

That would be the worse that can happen.

Its a risk the team must assess. You must have workarounds and a plan B before you take a new approach.

[Billfred]

Originally Posted by KenWittlief

Its a risk the team must assess. You must have workarounds and a plan B before you take a new approach.

Ken's right--but luckily, a plan B is not that hard to find. (Granted, you're not going to just switch it out between qualifying rounds, but they have come together quickly. Realistically, I'd expect for a team in that situation to limp around with their current arrangement for a match or two while it came together.)

Of course, there's one easy way to find out whether all these steps would be necessary--test it before you put all your metaphorical eggs in that competition basket.