Hey guys. I figured this was probably the best place on H-T to ask this question. I'm working on the impact attenuator or "crush box" for Penn State's Formula SAE car. We're making a box out of carbon fiber wrapped nomex or aluminum honeycomb and going to fill it with energy absorbing foam. I was wondering if anyone had any experience with energy/impact absorbing foam and may have any suggestions? I'm having a little trouble finding a place to start looking for this type of foam and what sort of make-up and density, etc. Thanks for any help!

 

one of my buddies works at nomaco.. they produce alot of foam stuff... ill show him the thread

 

Hey, I'm the guy JDogg was talking about. I'm a mechanical engineer in the research and development department at a polymer extrusion company. I design and manage projects that entail all kinds of custom shapes and formulations. There's probably a hundred different formulations I can work with. Now, on to your problem.

We make all kinds of foam. What kind of G loading are you looking to get? Also, what type of transducer do you plan on using? Do you want it to be one time use or reusable? How big do you want this to be?

That's just the starting point. All that we need to do is make the box so that it can be assembled in two halves (making identical molds will be easiest). Make sure that the flanges are properly designed (so you can bolt the two halves together). And then fill both halves with foam and put the transducer in the middle of it all. And Whalah! you have your impact tester.

I can't tell you the formula of our foam but I can talk about densities and physical properties that you are looking for. Once we narrow down the questions above we can pick a foam that will work for your application and I can see about getting you samples.

 

Well the crush box is usually an overlooked area of the car, this is the first year that they really have a team working on it to do anything. The rules don't really state any specifics. We were thinking probably a 35mph impact for a 380 lb car + the weight of the driver. I have no idea about a transducer. It would be a one time use box. We will be trying to build a few of them and test them. It will be about 6 inches from front to back and the back will be a 9.5" by 9.5" square. It'll be shaped sort of like a "D." Thanks a lot man.

 

I'll have to run some numbers later but that sounds reasonable. I'm not sure if we could get below the injury threshold, but we can reduce the G loading on the driver.

 

Hey thanks a lot man. That was just a basic number to work off of. Any sort of general idea for a foam to work with would be great.

 

The stuff that comes in the crx's bumpers seemd to work good the other day when i got rear-ended.

Or what about that foam, its like a 2 part, you mix it its like a liquid. You fill the cavity to like 40% or something.. Then it dries and expands and turns to foam.

 

I work at a body shop in State College and could probably get you some damaged samples of impact absorbers off cars shoot me a IM if you want some.

 

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Or what about that foam, its like a 2 part, you mix it its like a liquid. You fill the cavity to like 40% or something.. Then it dries and expands and turns to foam.</TD></TR></TABLE>
Thats what we were thinking about.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by swanny &raquo;</TD></TR><TR><TD CLASS="quote">I work at a body shop in State College and could probably get you some damaged samples of impact absorbers off cars shoot me a IM if you want some.</TD></TR></TABLE>
That would probably be great for the documentation and research aspect. I'm meeting with my group today i'll get back to you.

 

Yea the rules fon't even mention it has to be foam. The way its written you could use a giant spring as long as its 150mm x 100mm x 200mm

I just joined Western Michigans team I'm not sure what kind of foam were using but ill look into it

 

No the rules certainly don't mention it, but i think that's definitely the way we're going to go.

 

yeah im on Georgia Southern's team, seems those slackers dont want to try to get any money from outside sources, so we dont have a project this year
they all want to concentrate on the mini baja buggy. which is gonna be a piece anyway...

i hate not being a senior yet, nobody listens

but we used the 2 part expanding polyurethane foam to make ours last year, and during "testing" with a light pole there was no damage to driver or car at est. 25 mph.