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

[SpecialK]

Oooh Yeah! Right up my alley! (IMG:http://www.914world.com/bbs2/html/emoticons/mueba.gif)

I actually have a 1000' roll of unidirectional, aerospace grade, defunct NASA project CF, just for this purpose!

I did nearly all of the structural repairs on the AV-8B Harrier wing (entirely CF, with the exception of the titanium outrigger attach points), and most of the CF/Kevlar repair on the F/A-18E/F SuperHornet fuselage/wing/stabilator up until a few years ago. CF is a super stiff/super light material if applied "correctly". An autoclave would give optimum results, but vacuum bagging and heat curing (one hour 70F under vacuum, followed by one hour at 190F +/- 10F under vacuum [29 in. hg]) will give satisfactory results also. The correct epoxy for the strongest/stiffest material would be Hysol EA956 CF Resin.

I talked to a couple of strength engineer buddies of my at work on whether it would be stronger to bond the CF directly to the prepped metal, or use the longs as molds, and then bond them on with a high-strength adhesive like Hysol EA934. One issue of bonding directly to the metal is that CF will corrode damn near any metal it comes in direct contact with (dissimilar metal corrosion) with the exception of Titanium, so a barrier of FG would have to be laid down first, and then the CF over that. Since an autoclave is not an option, only about 4 layers of the uni-CF could be laid down at a time to ensure correct resin content, with a final layer of peel-ply to ensure that the following layers (also laid in no more than 4 layers at a time) adhere (the peel ply give the last layer "tooth" for the following layers to adhere to without damaging fibers of the previously laid CF as you would by sanding). The Uni-CF will be laid with 50% of the plies parallel to the longs, with 25%/25% on a 45 deg. bias.

I ultimately decided to go with the "mold" method, using high-strength adhesive, and CRES pull-type fasteners (corrosion resistant steel pop-rivets [counter-sunk] Cherry Max Rivets ) for a little added strength, but mainly to get the proper squeeze out of the EA934 HSA. It'll be made in 4 separate parts, all on the interior of the car (I'll use whatever's left of the roll on the outer longs....someday). One piece for each inner long that overlaps a few inches onto the lower firewall, another piece that runs across the lower firewall (overlapping the long pieces), and up each side of the center tunnel, and one piece that runs across the lower front of the passenger compartment, and ties into the forward end of the long pieces and the center tunnel.

I'm going to have to do a little experimenting with the CF to see how many layers I'll need to lay down to get the desire thickness (shooting for .080").

PS- Unidirection is made specifically for strength/stiffeness in a given direction, most of the other weaves are for aesthetic purposes.

I guess I'll have to take some pics as I go along. I hope to get going on it in April when the weather starts cooperating....we'll see, lot of irons in the fire.