carbon fiber experts?? Options

[r_towle]

So,
Carbon fiber is 6 times stronger than steel.

here are my thoughts.

take off the outer rocker.
Fix the rust with new steel.
sandblast the area
Lay on a layer of CF directly to the inner long front to back, wrap in to the bottom and top horizontal layers.

when using CF and bonding it to steel, I have read that you would use an epoxy resin to bond it directly to the steel, so it would be the same as putting por 15 on steel (por 15 is an epoxy layer)

So, thoughts? plus, minus?

Rich

[alpha434]

Yeah. That's mostly true. Much more brittle. And don't forget that you can selectively heat treat and anneal portions of the bodywork- If you know what needs to be strong and what doesn't.

And then, you aren't getting the strength unless the cf is very tight against the metal. Very many bubbles would make it worthless.

[alpha434]

Of sourse, you could use por15 as the epoxy to hold it on.

[Jeroen]

I don't think it'll give you the desired strenght unless you put it in an autoclave
then again, I'm no expert...

go ahead and let us know if it works (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif)

[alpha434]

Wait. It's six times as strong as steel by weight!!!


Just joking.

[majkos]

What you use for making a mold? (IMG:http://www.914world.com/bbs2/html/emoticons/ohmy.gif)


Does the template has to be perfect?

[Brian Mifsud]

If the bond isn't excellent, I suspect there is no benefit and its a waste of time. Epoxy will pop loose and the carbon fibers will never do any of the load sharing. The thermal expansion coefficents of each material are different enough that there will be relative movement between the two, even with the car sitting and no preload on the CF.

Of course.. carbon fiber and aluminum are commonly bonded together in racecars and mountain bikes.. so somebody out there has figured out how to bond them, I just don't think it's with the commonly available epoxies.

you could always make up a test specimen, bond it, then torture it. That would really be the only way you'd have any confidence in it.

If you have any aspirations to put it on the INSIDE of the car, better slap a layer of kevlar over the Carbon Fiber. When carbon fiber/epoxy break from impact, you have shrapnel. The kevlar keeps the shrapnel away from the human body.....I'm still picking pieces out of my forearms before we learned this trick back when.

[lapuwali]

Lots of dangerous assumptions here.

The resin used is fairly important in any composite, and there's a huge difference between air-dry, room-temp curing epoxies and the exotic stuff the aerospace and F1 people use in their autoclaves.

Any figures you read in a book on relative strengths are theoretical, and stuff you can get off the shelf isn't necessarily up to top standards, unless that shelf happens to belong to Boeing, et al.

Strong in pure tensile strength does not mean strong in all dimensions under all uses. It's hard to align CF fibers so all of the forces are taken only in tension along the length of the fiber, and CF is actually quite weak under bending loads.

[alpha434]

Yeah Yeah. But if its already against a steele underlayer, then it wouldn't be in much of a bending situation. And the mold would be the part that you're layering.

I think you should use the por15 as the curing agent.

Por15 is very hard, so haveing a peice of CF soaked in the stuff would be like caking it on an eight of an inch thick.

And if anyone wants boeing style epoxies- boeing actually has to sell there excess stock after completing a contract. Me and all my buddies get stuff from northrup grumman.

[lapuwali]

QUOTE (alpha434 @ Jan 26 2006, 04:20 PM)

Yeah Yeah. But if its already against a steele underlayer, then it wouldn't be in much of a bending situation. And the mold would be the part that you're layering. I think you should use the por15 as the curing agent. Por15 is very hard, so haveing a peice of CF soaked in the stuff would be like caking it on an eight of an inch thick. And if anyone wants boeing style epoxies- boeing actually has to sell there excess stock after completing a contract. Me and all my buddies get stuff from northrup grumman.

What, you don't think the longs bend?

POR-15 is almost certainly a crap "epoxy" compared to anything that will provide any actual strength.

[alpha434]

Yes. They bend. But they wouldn't bend so much as to crack the CF off.

And por-15 bonds to metal. That's going to be important.

And maybe once every couple of seasons, you'll have to change up the CF layer.

[jd74914]

QUOTE (lapuwali @ Jan 26 2006, 08:05 PM)

QUOTE (alpha434 @ Jan 26 2006, 04:20 PM) Yeah Yeah. But if its already against a steele underlayer, then it wouldn't be in much of a bending situation. And the mold would be the part that you're layering. I think you should use the por15 as the curing agent. Por15 is very hard, so haveing a peice of CF soaked in the stuff would be like caking it on an eight of an inch thick. And if anyone wants boeing style epoxies- boeing actually has to sell there excess stock after completing a contract. Me and all my buddies get stuff from northrup grumman. What, you don't think the longs bend? POR-15 is almost certainly a crap "epoxy" compared to anything that will provide any actual strength.

(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif) 100%, longs bend and POR though flexible and able to bond to metal is not a proper resin, or even a good bonding agent to the longs. If it was why would people use anything else? (IMG:http://www.914world.com/bbs2/html/emoticons/cool.gif)

[bondo]

What if you layed up all the carbon fiber and then lay a sheet of plastic on it... Then close the doors and fill the car with sand while it sets up. Instant even pressure to push out any bubbles! (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

[TimT]

I think its a bad idea to try and reinforce the long with CF.

First to get a get a proper bond between the CF and steel substrate you need to finish the substrate (steel) with an anchor profile which will provide enough "tooth" for a good mechanical bond between the resin and the steel.

Second the CF strands have to be oriented properly (as mentioned earlier in the thread). I have a feeling the longs on these cars move in three planes.

Third, even if you prepare the substrate with a proper anchor profile..You will have holidays in the resin.. ie corrosion paths right to the raw steel..

best bet to reinforce is thoughtful application of extra sheet metal rosette welded to the tub ..or a roll cage..

[anthony]

Sounds like a big waste of time. Just fix the longs, por15 them, or paint them. Store the car in the garage whennot used and don't drive it when it rains. Once a year clean out the rockers. The longs should last another 40 or 50 years.

[alpha434]

QUOTE (bondo @ Jan 26 2006, 05:28 PM)

What if you layed up all the carbon fiber and then lay a sheet of plastic on it... Then close the doors and fill the car with sand while it sets up. Instant even pressure to push out any bubbles! (IMG:http://www.914world.com/bbs2/html/emoticons/smile.gif)

Thats an ok Idea. But if your already covering with plastic- then why use sand instead of a vacuum to suck the epoxy down.

[alpha434]

QUOTE (TimT @ Jan 26 2006, 05:35 PM)

I think its a bad idea to try and reinforce the long with CB. First to get a get a proper bond between the CB and steel substrate you need to finish the substrate (steel) with an anchor profile which will provide enough "tooth" for a good mechanical bond between the resin and the steel. Second the CB strands have to be oriented properly (as mentioned earlier in the thread). I have a feeling the longs on these cars move in three planes. Third, even if you prepare the substrate with a proper anchor profile..You will have holidays in the resin.. ie corrosion paths right to the raw steel.. best bet to reinforce is thoughtful application of extra sheet metal rosette welded to the tub ..or a roll cage..

Wow. You guys have no interest in R&D data at all, do you.

If we find out that the CF bonds properly, then we can do reinforcement bars out of CF instead of steel.

And CB stands for cardboard. That definately has no application here. (IMG:http://www.914world.com/bbs2/html/emoticons/wavey.gif)

[r_towle]

lots of good thoughts...

I will tell you what I know...

Carbon fiber has been tested in a specific application...to reinforce aging bridges..it is applied cold to bare sand blasted steel to add structural integrity to these aging structures...

The epoxy is very specific, and por 15 is not it.
I would use the correct epoxy, it is available.

So, in the bridge application, it is applied in the field, in varying weather conditions, and has held up to being exposed to many different twisting and bending stresses.

I would use the same cloth and epoxy that is being used for the bridge application.

I still have my concerns...but I am gonna run this by a few composite engineers to get some real world feedback, I may even track down the company that is doing the bridge tests to get some feedback...

I was just thinking that it would be a great way to stiffen up the car with less weight.

And, if it does not work...I can always remove it and add more steel.

Rich

[TimT]

thats cool manipulate my response when you quote me, make CF appear as CB "cardboard" (IMG:http://www.914world.com/bbs2/html/emoticons/screwy.gif)

I actually may have a clue about how some of these things work..Besides being a PE, I am very involved with AWS(CWI), and NACE. I have done structural analysis for years

CF reinforcement may be applicable, but many controls need to be in place.. first would be preparing the substrate with a proper anchor profile., which is probably beyond the capability of a home mechanic.

It would be much easier and cost effective to weld some reinforcments in the hot spots..

Por-15?...lets find out which composite mfg recommends that to be used with their fabric.

[TimT]

(IMG:http://www.914world.com/bbs2/html/emoticons/hijacked.gif)

QUOTE

I would use the same cloth and epoxy that is being used for the bridge application.

Id love to see the white papers on this..

Ive been working on the Suspension Bridges surrounding NYC for 25 years, and have yet to see a FRP applied...

Im very curious