Bonding Fiberglass to steel

How do I go about bonding fiberglass to steel? I'm going to be laying up several layers of fiberglass over a steel shape and I'm worried about it poping off. Is there a certain resin I need to use or do I fix and adhesive with the fiberglass to get it to stick? It's going to be structural so it needs to be tough.

if your looking for real strength don't use the standard resin it sticks great when laying layers together but in not nearly as good when bonding to different materials. go with a good quality epoxy resin it is much stronger and bonds to steel and other materials much better. West system epoxy is basicly the king in the marine world although it is expensive it is bar none the best stuff out there. right next to that is MAS epoxy which is also very strong and i beleive slightly cheaper.

I "semi" agree here,fiberglass is out,Epoxy is in.But"Bonding" to steel "structurally" is almost impossible.You can reinforce using imbedded steel,but if your thinking of some form of lamination?What are you trying to do?

laminate skidplate...don't want it popping off or peeling when the skidplate gets nailed.

I've done limited fiberglass work before with regular resign, but not failmiler with expoy resign all that much. Is the epoxy mixed with resign during layup? Also I'm assuming the steel need to be primered from what I've read.

You have to think "concrete and rebar" to get on the right track.

Vinylester resins and epoxies do not in and of themselves "bond" well in a structural sense.

You will need to laminate over some "ears" or studs to mechanically fasten to the metal you will be glassing to, and this presents another problem.

If it's steel, especially sheetmetal, the bond to the surface, and the ears or studs will eventually "wick" moisture. The metal will rust under your laminate, even if you use stainless. 90 percent of all stainless steels will rust in the absence of oxygen, although it's done in just about every rudder (sailboats) construction.

As the rust builds, it will split the laminate, just like blisters on a boat.

Personally, for a vehicle application, I'm thinking you want some "give". Epoxy laminate is extremely rigid and brittle, especially done at home where you will not be able to achieve the proper resin to glass ratios. Amine blush will also hurt you in the metal department, and in layup, if you do it in stages.

Vinylesters are more forgiving, but in any event, think more glass than resin.

In short, laminating resin has no wax in it, it will stay "tacky" while exposed to the air. Finishing resin does have wax in it. As the resin cures, it heats up, and the wax floats to the surface preventing exposure to the air. All surfaces where the wax covers will cure complete.

West Systems is indeed good stuff, but in inexperienced hands, it's also a good way to waste alot of money.

--ron

PS: Some Vinylester trivia for ya. Acetone is the "dirty" component, Styrene is the "clean" component.

Getting resin to bond to metal isn't hard, the more porous the metal the better the bond. Trouble often starts, because fiber glass, resin and metal expand and contract at different rates. Can cause separation.
Some kind of ribbing, helps them to expand and contract together somewhat.
Just an option that I've used for years, is 12 ply 3/4" marine plywood as a backing for sheet metal skid plates. I seal the plywood with a resin and bolt it to my skid. The plywood is as strong or stronger than say 1/4" steel but has a much better memory and doesn't bend, but bows and springs back.
I've also used the marine plywood structurally. I used it for years as a sub frame for VW desert racers. A lot of guys laughed, but I noticed more and more buggies showing up with plywood skid pans at the races.

Yeah I do want it to flex, not super stiff, but to stick to the steel. Plywood's a good idea but I have some goofy contours that may cause problems...fiberglass was considered due to the extra strength and lightweight, although most of the glasses weight comes from the resin. I hadn't consider the expansion rates much though.

Unless you get really exotic, fiber glass wouldn't be my first choice for something structural. If I wanted light weight and strength, I'd be thinking a sandwhich or ribs.
Just as an example, a flat piece of sheet steel 2 feet square by 3/16" thick. With ribs of 1/2 angle iron spaced in rows. Three rows of angle iron will increase the strength drastically. It really doesn't have to be angle iron, ribs of 3/16" X 1/2" flat stock welded perpendicularly to the sheet steel will do pretty much the same thing. If you use two layers of sheet metal and ribs between the layers, you have really increased the strength, with much less weight.
I listen to a lot guys and they like to produce bullet proof stuff. My reasoning has always been, something is gonna bend or break and I'd rather it be my skid pan, than my Jeep. I usually try to build in some kind of crush or flex. One reason I prefer nuts and bolts to welding or both when practical. I also avoid solid beads when welding, I usually weld to 1 and 1/2 times the strength, needed to do the same job with a bolt or a series of one inch beads (spaced).

Trying to keep theskid under 20lbs. Right now I have ribs, break on the edges, and a raised center section with bends to stiffen up the center section. Don't going to run 3/16" if I can help it, way to heavy and so 1/2" is definatly out. The fiberglass isn't the main support more of just a secondary stifftner. See my posts in Laminate skidplate design and other skidplate design threads.

How about a sandwhich, a layer of sheet steel, a layer of glass and matting and a layer of sheet steel. I doubt the resin is going to bond to the sheet metal forever, but some bolts through all three layers in a grid, will help hold it in one junk, for as long as possible.
I used to lay up nose peices and such for formula cars. The technology has come a long ways, but we rarley tried to bond metal and glass, we would use fasteners (rivits, nuts and bolts, cleekos or whatever).

Weasel said:

Trying to keep theskid under 20lbs. Right now I have ribs, break on the edges, and a raised center section with bends to stiffen up the center section. Don't going to run 3/16" if I can help it, way to heavy and so 1/2" is definatly out. The fiberglass isn't the main support more of just a secondary stifftner. See my posts in Laminate skidplate design and other skidplate design threads.

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what about a high density plastic? a lot of buggies are running them these days; they're lightweight and slide well.

buggies use it with mixed results. Jason Paule doesn't recomment the stuff. Som rock it slides on, others it catches, gouges and tears. Tracy Jordan is running plastic and has huge holes ripped in it. Jason prefers steel as it usually slides easier as it won't gouge. And the rocks around here tend to be really pointy and gougin would be an issue. I'm thinking of ditching the glass and just beefing up the steel a bit. The wood idea the 8mud suggested sounds interesting and I maybe be working with that a bit. What kind of resign do you coat it with? And it will be sandwitched between two pieces of steel so bonding isn't too critical.

I'm also trying to minimize the amount of bolts running throught the structure nothing to hang up on or haivng to worry about bolt heads being mashed. Along holes for recessed bolts that rocks could catch in. Problem I'm having right now is trying to work with the tranny mount bolts to get them out of the way.

I need to do some final measuring tommorrow, then I make a post in the enginerding forum when I get the numbers close.

Carriage bolts may work well. I used boat paint (clear) with a hardener, I think it was Urethane (smelled like it), payed special attention to the edges (three coats) the edges are were it sucks moisture. Varnish would probably work just as well, but takes forever to dry. They have some other stuff I've used, you see it truck trailer beds on occasion. It's a laminated plywood, resin impregnated. The only trouble with the stuff is, it's expensive and few things will stick to it (undercoating peels off).

so basicly desk stain or the similar would work.

8Mud said:

Carriage bolts may work well.

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Elevator bolts if you can find them heavy enough.