Using CF Panels to Reinforce a Steel Spaceframe

General Composites Discussions Engineering Talk
#1

Greetings,

My FSAE raceteam is looking into using CF panels to reinforce the spaceframe structure of our car. The panels would be placed in-between the spacing between the tubes in order to replace the triangulated steel member. The idea is that the panels could provide similar strength with reduced weight and double as body panels.

Does anyone have experience or insight into this idea? It’s been around for quite awhile but from what I’ve seen at competition, it isn’t used very much.

Here’s a link to the paper where I’m getting my information.

www.firearmz.com/user/SAE_983055.pdf

#2

I can’t tell much about this because of contracts, but I can tell you this:
I build bodypanels, sandwich foamcore. glued on the chassis they provide a lot of extra stiffnes. they replace aluminium bodypanels, no stuctural function, chassis is loadbearing.

#3

Thanks for the reply. If legal issues will allow you, I have more questions.

If these panels are not in-line with the center of the frame members, how effective are they at providing extra stiffness if they are not in an ideal position to accept loads? Are all your panels bonded together as well?

#4

Side panels are on the side between the weels, glued to all of the cross members and struts. They provide a box construction. can’t tell the exact numbers, but the difference between the alu panels in noticable by driver and lap times. (and in the price, haha)

(it’s like putting cardboard in stead of paper on the sides of a frame made out of small sticks and matches :wink:

#5

A very intuitive way to describe it!

Without looking too much into the details, would you say the price increase was worth the reduction in lap times?
How about our car whose entire construction budget is in the neighborhood of $50,000?

#6

YOU GUYS GET 50K??!?!!? We built out hybrid FSAE car with 7k! An extra 43k would have been really nice.

For lap times find out what your weight savings are and run lap sims with the lower mass. That should tell you whether it’s worth it or not. Sheet AL is much cheaper and easier to machine than composites are though so in my personal opinion I don’t know if you’d save that much weight, although popularity wise many teams used CF both in the hybrid and gas competitions from what I saw.

#7

50k may sound like a lot but some of the teams we were competing against priced their car at well over 200k if they had to purchase everything without sponsorship. How did u manage to make a car for 7k though? Very impressive feat.

As for race simulation, I don’t believe our team has that kind of software. Do any software companies offer sponsorship for student competition teams?

#8

It was extremely difficult and stressing at times (most of the time). It required a lot of money management and presentations for sponsorships. In the end the car ended up costing about 9000 without labor costs, 5000 out of pocket, 4000 donations. The other 2k went to shipping the vehicle to New Hampshire

I know Texas A&M gets ridiculous amounts of money, enough to keep two cars. They’re likely one of the 100k+ teams you’re talking to

As for lap sims I know some companies offer their software. It’s not easy to easy to learn but whoever learns it will get a job in two seconds, its an extremely valuable skill especially for us junior engineers. Call up ChassisSim, see if they’ll help you out. Some teams made their own lap sims in Excel as well.

Also keep me updated with your team. I would love the position of honorary internet member. :smiley:

#9

Thanks for the sim information, I’ll see if the team is interested in pursuing it.

As for your position as honorary internet member, I approve ; help is always appreciated! What are your areas of interest in FSAE cars? That way I’ll know which design challenges to post to Composites Central.

Last thing, which school did you race for?

#10

If you can get lap sims you’ll blow the judges away. After all the end goal of our cars is to get around the track as quick as possible.

Materials. It isn’t obvious from my ownership and maintenance of this forum? :smiley:

I raced with Cal Poly Pomona last year.

#11

Quick thing about this, composites companies are happy to sponsor FSAE teams. I forgot which Canadian team was at FSAE west that I talked to but Boeing let them use their autoclave and even had their fabricators rebag the cars after the students bag had leaks in it.

The weight savings are significant but for low funding teams like ours money is tight you naturally have to balance between other factors. How are your other big expenses looking e.g. steel for the frame, engine, wheels, suspension components?

#12

Don’t know the exact number on the price, but the whole care was 25k more. that included prepreg CF seats, modifications to other parts because of the thicker panels(more a one off than a production car, took 3 weeks extra)
and carbon fibre visual allmost everything. Creating simple panels isn’t that hard, or expensive. changing half of the car because of it is :wink:

#13

Cal Poly Pomona, thought that name sounded familiar. I liked the look of your car, composites work was top notch but I prob could’ve guessed that based on your involvement haha

As for the CDN team, I believe that was Manitoba, not sure how they swung that deal, but I’ve got the sponsorship section of our team working on that. OH wait, just did a search, Boeing has a composites plant in Manitoba. That would explain it…

Expenses are mostly for steel from what I’ve seen of the budget. Tires were a fair chunk because we bought a few sets down in Cali. Engine is a CBR600 F4i and lately we’ve broken quite a few so that’s quickly becoming a sinkhole. I’ll know more about it once last year’s budget is finalized.
Was your California 2011 car the one made for 17k?

#14

Fair enough. I’m pushing for more CF components in this year’s car. The only stipulation is $$, so if that pans out its gonna be sweet…

#15

Ah that was the regular FSAE car. I was on the Hybrid team, we went to New Hampshire. Our composites work was not even close to top notch, something I hated, simply because we had to spend all our money on the parts that actually moved the car. I did help the the better funded FSAE team frequently though, they were in the lab next door.

[ame=“http://www.youtube.com/watch?v=Kgman94y1EM”]Formula Hybrid 2011: Cal Poly Pomona Tilt - YouTube[/ame]

To reduce your cost with composites start calling companies immediately. For sure you’re going to need tacky tape and bagging material so get some of that as fast as you can. After that depending whether you decide to go prepreg or wet layup you’ll have a whole another list of supplies you need.

As far as stiffness goes an easy way to check is take your frame model and add plate element over all the gaps in the spaceframe in which you’re going to add composites. Depending on the layup you do, change the material definition to reflect anisotropy. I suspect you’ll use two layers bidirectional, as it’s the lightest layup that wont have pinholes in it. For the floor if you add enough layers you can actually stand on it, instead of having to have your driver step on tubes. Another added benefit is the driver compartment is usually is the least stiff since you have to reduce the number of tubes. Adding extra material to this area could help with that.

For the FEA just run it bare frame, then run it with the covered frame through all the regular torsion, cantilever etc loadings. This should give you material to give to the judges. For density, typically aluminum is 2.4 g/cm^3 on the light side. All the composites I’ve seen made in student shops like yours have been 1.2-1.7 g/cm^3. Thickness of my plates have been between 1mm to 1.3mm for one of the fabric styles I used.

Combined with area you’re going to cover over your frame this should give you enough data to get some preliminary calcs done, both for yourself and the design portion. Competition is stiff in your division. Let me know if you need any other help.

#16

Thanks a bunch for the advice Canyon, I’ll get started on it immediately.

#17

Where in Canada are you located?

#18

Saskatoon, SK