View Full Version : Increased structural integrity with structural foam

12-20-2005, 11:32 AM
After thinking about this for a while i searched online and found out that this has been done and is being done in some new cars. Filling structures with foam increases the strength and the ability to absorb impact of that structure.
I am going to do this on my truck in order to have more rigidity and safety without significantly increasing weight. I was wondering if anyone here has filled A/B pillars, frames, or roll cages with expanding structural foam, and if so, is there anything I need to know about doing this

12-20-2005, 05:21 PM
I know the new FORD trucks have a foam filled frame. there claim is for a quieter ride.

12-20-2005, 06:00 PM
I was about to ask this same thing.

Its got to help sound deadening.

It should act as a crush zone.

Does it make the body flex less?

Does it promote or prevent rust?

12-20-2005, 08:46 PM
it prevents rust, lowers noise, makes the body flex less by spreading the loads over a greater area and increases safety. I read about one roll over test where the top of the vehicle initially caved in 14". After they filled the pillars with the structural foam it only caved in 3" in the roll over test. Thats pretty impressive if you ask me.
My fiance works at a body shop and she checked with her supply manager, and for 2 part set it is $22. I am not sure how much this will do but I know I can get the stuff now and I am going to try it.
There are different kinds of foam used in new vehicles, structural and noise dampening. The structural foam expands about 3X and the regular noise dampening foam expands around 10X the volume you apply. This is according to what I have read. I have not used the stuff yet so I cant say from experience. I have used great stuff expandable foam in the structure in my trunk on my 68 firebird and it was amazing how much noise it killed, so I have to believe this other stuff works too.

12-20-2005, 10:45 PM
Did someone mention Foam?


Whoops, you wanted info on structural foam, not Foamy. Sorry.

You have to make sure to get the correct foam. I know FoamSeal is an OEM manufacturer and makes the foam used in several Infiniti chassis; it's a 2-part structural catalyzed foam. Lord "Fusor" Terocore foam is the structural foam Ford uses in their new trucks frames and A-pillars. You need structural foam, not sound deadening foam. BIG difference!

Also, the structural foam is very minimally expanding, so you need a LOT of it, and it ain't cheap; $25 usually gets you about 8 ounces or so. The acoustical foam is usually very high expansion and much cheaper.

I have seen the FoamSeal structural foam offered in different density ranges; the higher the density the stronger obviously. You could easily estimate the weight gain of the foam by rough measuring all the box-sections you would have to fill to figure out your final filled volume and then calculate based off the manufacturer's claimed density. If the gain is minimal, I'd go for the highest density stuff you can get!

If you prep the body/frame properly you can get some pretty darn good stiffness improvements out of the stuff; however the foam has to have a clean surface to "bite" to for maximum effectiveness; otherwise it will pop off the walls of the frame and you'll just have a block of foam bouncing around in there doing nothing for structural improvements.

I'm planning on using structural foam in my new chassis and will probably fill the A-pillars and some of the roof inner structure with it, as well as the area between the floorpan and the open-section floorpan braces. Filling the rockers would be a good idea from a strength standpoint but since the rockers also serve as a water drain for the cowl area and a drain for any water that makes it down the 1/4 windows it may not be a practical idea to foam the rockers as you may inhibit water drainage and promote rust. Pretty much any box section or closed-profile in the body, frame, or subframe would be a good candidate to foam-- drill holes if you have to for injection spots and a bleed-out spot at the other end of the closed section.

You need to use caution where you use it and how much, especially on thinner panels; I've seen several trunk lids, doors, and quarter panels literally blown apart by guys using foam in car audio installs to cut down on rattles. It would be pretty hard to bloat or pop a frame, but use caution on sheetmetal stuff. This goes for the high-expansion acoustical foam more than the low-expansion structural foam, but you still need to keep it in mind.

In fact, here's a datasheet for the Lord Terocore stuff:

Last thing: cleanup on this stuff is NASTY. If you get some where you won't want any remove it ASAP, and wear gloves!


12-23-2005, 03:16 AM
Thanks Troy. Its one more cool thing that I will never be able to do.

12-23-2005, 05:33 AM
I made a pvc bumper support and filed it with foam from the hardware store, this was tested by a careless driver that backed into the front of my car it did collaps the pvc but not as much as it would have without the foam and the bumper cover was reusable