Carbon Fiber
 

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.

Re: Carbon Fiber
 

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

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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

Re: Carbon Fiber
 

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

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

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.

Re: Carbon Fiber
 

Ooh wow thanks for all the replies.
Yeah, we are aware that it is hazardous to deal with, so most of the machining, such as cutting and drilling will be done by a sponsor machining company. We may build it with the composite sponsor, working along side them with all the proper safety precautions in the right work environment. For safety also, whenever we work with it, we may wear resperators to not inhale the dust and will also wipe it with a wet cloth every now and then, and definitely whenever it comes back from being machined.

For connections and interfaces, there won't be any since it will all just be one single molded chassis. For upper structures, if we choose to go with a modular design, it'll probably just have an aluminum bracket or angle aluminum with nuts and bolts to attach.

Tytus, thanks for the support of just giving it a shot and trying it out. No team, that has publicly announced it, has yet to make their whole bottom chassis out of molded composites, all one piece with no connections or interfaces. 842 has made much of their chassis using composites, but with interfaces and components to connect them.
If we do plan to try it out, we will definitely experiment on it in the offseason before we ever use it during the actual season to see if it can really take a beating or if it is just impractical.

Re: Carbon Fiber
 

exactly! But how would you do that in the pit area of an event? I dont remember the exact rules from last year, but I dont think you are allowed to take the robot anywhere you want during an event, only to the designated offsite machine shop

and they may not allow CF to be fabricated or machined in their shop.

Re: Carbon Fiber
 

Start small. Before investing a season and a good deal of money (potentially), work with the sponsor to develop smaller, key parts that can best take advantage of the carbon fibers properties. It will also give you a season or two to devolp your relationship with the sponser- I've had plenty of sponsers change thier mind after a season, deciding that it wasn't at all what they had imgained it.

In the future, when you're team has built up some experience with the material, you will better be able to answer your own questions. Successful teams in FIRST usually evolve the basic designs and technologies behind their robots over the course of many seasons, rather then trying to make tectonic changes in techniques and materials. But the progress has been steady- teams today regurally feild robots today that wouldn't have seemed remotely feasible when I first joined (multi gear transmissions are so 2 seasons ago- It's all about going sideways these days).

A great deal of attention is paid to composite materials great strength and low weight, but I've always been more interested in it's incredible stiffness. Aluminum has always struck me as being a fine material where strength (most measures of strength anyways) and low weight is a concern, but it's softness can worry me. If the bicycle and R/C car industry are any indicators, Carbon Fiber's stiffness sure is winning people over.

I suggest that you consider the composite for any part that you feel requires the extreme stiffness and strength, or perhaps an odd shape. Keep them small to start with, and keep a backup plan for producing the same part in aluminum or some such. Producing a whole frame with an untested, in FIRST, material with a brand new sponser sounds risky to me.

-Local

Re: Carbon Fiber
 

First of all, if I knew there was a one piece composite frame at a competition, CF or not, I'd go check it out, and probably ogle it.

That said, I just have one thing to add to what everyone else has said- think damage control. If you can use all clamps on tube, and set up a way to quick change a broken frame, then by all means, if you have the resources, go for it. But, remember, if your frame breaks (And it likely will at some point unless overdesigned - just the way Murphy and robot prototypes tangle), that particular one is pretty mush toast. You'll have either a crack with layers and a few fibers sticking out all over the place that will propagate, or a massive composite explosion, but either way, a replacement will be in order. So just design with an option out, and bring some gloves.

The best of luck- I think this could turn out to look really good!

Re: Carbon Fiber
 

Thanks for all the help.
I'm not sure if I mentioned this or not, but our main reason for going CF is for weight, in hopes of saving weight. We had a problem this past year with weight. We're already using different design tools such as Inventor to help and CF would be able to help out in some places to also save weight. Another reason is how it is stiff, unlike aluminum which will bend. Also unlike aluminum, it just shatters, which is a definite minus. Another reason though that we are considering it is because it is sort of an unchartered territory for design and would just be interesting.:D

I think we can all agree for now, that a CF does seem kind of on the impractical side.:rolleyes:

From all the concerns of it shattering from a FIRST competition, I think modularity is the way to go with this. Having different tubes to swap out, and some aluminum connectors and adapters so we can do a quick fix if it were to shatter sounds pretty good. We're not exactly sure about weight though, but 0.25" thick CF should be pretty strong, and somewhat lighter than .25" thick 6061 tubing.

Also, we would go CF ONLY if we could use bumpers. This past season, most of our main chassis lasted. The only part that got tweaked was where the bumper wasn't, in the front for our collector. I'm already scared thinking of what bare unprotected CF would be like after a single regional.:eek:

But yeah, going CF is def an idea, but we're going to experiment with it first. We're not planning on building a beautiful CF chassis, bringing it to competition, and finding out that it can't get rammed by another 130+lb robot without totally failing.:ahh:

Re: Carbon Fiber
 

My team may have picture some where of what unprotected carbon fiber looks like after a COUPLE MATCHES!. This was our first year using carbon fiber, even though it was just tubing. Luckily we brought plenty of spare rods with us to every competition. I'd say that we were breaking or shattering some rods after 2 or 3 matches.

While carbon fiber is light and can save a ton of weight, I wouldn't recommend using it for a chassis or some other component that is exposed to frequent impacts from other robots.

Re: Carbon Fiber
 

Team 1726 also used fiberglass to build and prepare the chassis of our robot last year. This helped us to win a regional and we never had a fiberglass piece break. We decided not to use the provided bumpers and the fiberglass was taking numerous direct hits at full speed. The bot is still fully functional today. I would also note that some of the impacts we suffered bent aluminum crash bars at 45 degree angles while similar hits on the fiberglass had no effect at all. While fiberglass is not exactly the same as carbon fiber I can vouch for the use of composites. I'd urge your team to experiment with these building methods. I hope this has helped.

Re: Carbon Fiber
 

we used fiberglass for our ball transport parts (conveyors, ball tubes) and for protecting sensitive components (camera helmet) and found it very durable, easy to cut with a rotozip, easy to put together, and relatively cheap.

I realize it isnt as durable/strong as carbon fiber but overall it seems to me a better material due to its ease of use and application.

-Q

Re: Carbon Fiber
 

Not entirely true I can get a sub kilo Titanium bike frame (litespeed) as well as a CF one (Look, Giant, Trek, etc.). The true advantage with carbon fiber, in that specific application, is the ability to tune the frame through the layup. By putting the material where it is needed for stiffness and making structural shapes not necessarilly possible in metal a frame builder can make a lateraly stiff structure that is vertically compliant to dampen road shock (vibrations transmitted from uneven pavement) and minimize rider fatigue. Anyone with a CF bike who's had an AL one will tell you this.

This is harder to do with aluminum because the tubes need to be stiff to minimize deflection in order to have a reasonable fatigue life. They do this by using large OD Al tubing. The result is a frame that transmits a lot of bumps.

CF alone isn't stiff, think of a CF fishing pole. Uni-directional fibers laid cured together in a matrix to have flexibility. It is the structural shapes and fiber orientations that you can use with it that allows is to be stiff.

Once again it all comes down to knowing the material you are working with and how to optimize it. Don't just use something because you can. Learn the whys and hows so you can use it correctly.

Re: Carbon Fiber
 

i would love to see some CF on a robot .. like on a part that dosent take any damage at all... like a shooter on one fo this years bots

Re: Carbon Fiber
 

We almost used CF for out shooter, but we realized we wouldn't have enough time to properly make our shooter out of CF. We did use it for the shaft on our feeding mechanism among other places.

Perhaps we'll use it for our fuselage in this years air game :rolleyes:

Re: Carbon Fiber
 

If you had used carbon fibre for the shooter wheel itself, I hope that you would also have had the presence of mind to do some serious investigation into the effects of that thing shattering when struck or jammed suddenly. As an inspector, I would have been very concerned about the potential for carbon fibre shards to be expelled from such a device as it failed.

Re: Carbon Fiber
 

We weren't going to use it for the wheel, just the shell around the wheel. We decided to stick with aluminum as you can see in This Picture

Re: Carbon Fiber
 

I've split this thread, placing the posts mainly discussing the legality of Carbon Fiber, and the associated cost determination discussions here:

http://www.chiefdelphi.com/forums/sh...threadid=49552

Re: Carbon Fiber
 

Yes its true, we have been using it very great success for years.

http://www.phxhs.k12.az.us/education...88&pagecat=136

Team 842 , the material is from www.creativepultrusions.com

We have never broken our fiberglass frame.