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[Duk]

After reading about high strength foam reinforced chassis being used in some new luxury cars, I did a little web searching and found http://www.sportcompactcarweb.com/proje ... index.html.
The most interesting thing in that article is the mention of how much stiffer the chassis feels after having various cavities foam filled.
I also found this http://foamseal.org/auto_aftermarket.htm. Unfortunately, trying to send an email was unsuccesful (maybe their email is out of action )
The big advantage of the Foamseal system is their pressurised delivery system, but the only other 2 part expanding structural foam that I could find (for a diyer) was http://www.uscomposites.com/foam.html, not a pressurised delivery system.
Now, it was stated in Barry's thread on the SZ, that the SZ used bonded panels to improve the chassis strength to allow the use of coil springs instead of torsion bars. If the filling of chassis rails can improve the strength as much as is said in the SportsCompactCar article, I'm seeing potential to strengthen the 116 chassis enough to do away with the torsion bars and adapt a coil over spring arrangement that allows a decent spring rate increase.
The added advantage is a clamed decrease in noise transfer.
Thoughts and opinions?

[Mats]

It is complete bullshit, don't use it.

You can quote me on that.

The only reason they use foam in moderna cars is due to NVH reasons.

[Duk]

It is complete bullshit, don't use it.

You can quote me on that.

The only reason they use foam in moderna cars is due to NVH reasons.

Hehehe, I kind of expected you to be the first to reply Matts

You have tried a high strength, 2 part foam in chassis rails and other areas like sill panels?

Now, I can apriciate the scepticism of such an online (or printed) magazine article, and I do have a motto "Beware of those with who have a vested interest in something they are trying to sell (like advertising space )" , but at the same time, it wasn't that long ago that the concept of a 2 litre, 4 cylinder engine producing 200hp was pure fantacy, let alone 600+hp.
Aluminium, fibre glass and carbon fibre were looked uppon with sceptasism also .
More input please.

[Mats]

What is the function of the foam? How can it possibly be stiffer then Steel? It will not function as a middle layer in a sandwich because the steel will not collapse witout it (obviously).
So what is the function of the foam?

Great way to add cost and weight though.

[Duk]

Taken from: http://forums.freshalloy.com/showthread.php?t=162693

Here is the original Abstract of that SAE paper 1999-01-1785

Quote:
Stability and structural intergrity are extremly important in the design of a vehicle. Sturctural foams, when used to fill body cavities and joints, can greatly improve the stiffness of the vehicle, and provide additional acoustical and strucutural benefits.
This study invovles modal testing and finite element analysis on a Sport utility vehicle to understand the effect of structual foam on modal behavior. The modal analysis studies are performed on this vehicle to inverstigate the dynamic characteristics, joint stiffness and overall body behavior. A design of experiments (DOE) study was performed to understand how the foam's density and palcement in the body influcences vehicle stiffness. Prior to the design of experiments, a design sensitivity analysis (DSA) was done to identify the senstivie joints in the body structure and to minize the number of design variables in the DOE Study.

And the Conclusion:

Quote:
The most sensitive area of the body were found to be the A-pillar, the D-pillar and their joints. With structural foam injected into this sensitive areas, the vehicle body was significantly stiffened, as shown by the increase in modal frequencies. The 1st torsional mode was most effected with an increase of 29.1% in modal frequency.
The design sensitivity analysis and design of experiments described here, can be used to identify the sensitive ares of the body structure. This results are useful in the determining the best application locations for structural foam.

[MD]

it's a wank .

Try doing a weld repair with that crap inside a channel and see how you go.

[Mats]

Ok, that SAE report is typically an NVH study. They are talking torsional modes and are probably looking at bending modes as well. This is a tuning tool to move torsional/bending modes apart to not have any modes at the same frequency as another system (i.e. engine firing frequency or prop shaft bending modes) so they can excite each others. If that happens you can have problems with vibrations or booming, not something you want in a new car.

It will however, not have anything to do with point mobility, i.e how much it moves during load. So it will not work for performance driving enhancement.

[Barry]

it's a wank .

Try doing a weld repair with that crap inside a channel and see how you go.

I rest my case Ozz ! I rest my case...

[sh0rtlife]

this has got to be the strangest thing ive ever heard of

hmm lets accelerate the rust
lets double the weight
lets make the car a bigger fire hazzard

stiffer...you gotta be kidding me...that would have to be EXTREEMLY dense stuff...youd be better off weight wise by c-channel wraping all areas your worried about with 1/8th steel...and likly end up the same weight

[Giuliettaevo2]

i can only see some result if the foam acts like a glue.

because the sills and everything is spotwelded together you might get some improvement if you also glue this parts. it would be the same idea as welding over the entire length ( doorlassen in dutch.. ).

The foam in the middle of the cavity would not have any impact, far to flexible there, but at places where different layers of sheet metal come together it might just toughen u the structure a little.

Lotus also glues chassis parts together.

Just my 2 cents... but i'm no engineer.