Thin membrane at high temperatures

[Marsh91]

Hey guys,

I'm looking to test and implement a new way of attenuating sound in a car muffler. The idea involves thin plates in line with the walls of the muffler which vibrate, and in turn cause destructive interferance. However I'm having trouble seeing if there is indeed a material that fits the specifications I need. This is the basic gist:

1. Extremely light (i.e. really low density).
2. Extremely stiff
3. A relatively high (compared to the density) elasticity modulus
4. Able to resist extremely high temperatures (motorcycle exhaust temperatures I have heard can range from 400-600 deg celsius)

For example: Balsa wood has a density of around 150kg/m^3 and a Young's Modulus of 3 GPa. Something like this, while not optimal, will most likely be satisfactory for the application without the high temperature. Imagine light and very bendy.

At the moment I was thinking of carbon fiber with a high temperature resin, but I just read a paper on aluminium honeycomb which has even better characteristics, but can only stand around 200 degrees celsius.

I would be very grateful if you guys had any ideas of a material I can use to fit these specifications.

P.S. I'm kinda new here so I'm not sure if there's an overarching Materials forum I should have posted in or not, so sorry if this is the wrong place.

 

[Metalhead97]

Marsh91,

Have you checked out the Al-Be MMCs? Might be a little low on the temperature requirement though, however I wouldn't think the metal component would actually reach the temperature of the exhaust if it's being cooled.

MH

http://www.linkedin.com/pub/luke-autry/1b/510/566

 

[Marsh91]

Metalhead97,

Thanks for the reply! I haven't heard of the Al-Be MMC's. A quick google tells me a lot about Al/Si MMC's, but nothing about Al-Be. Do you have any suggestions where I can find more info on it?

Also when you refer to be cooled, are you talking about cooling from the external air going over the muffler?

To give an illustration of what I'm trying to do, here's a cross section of the muffler. This design is quite simple with two chambers, one upper and one lower.

 

[Metalhead97]

There is a company called Materion that commercialized these alloys in wrought form. Might be a good fit as long as the temperature isn't too high.

When I was talking about cooling I was referring to any cooling loads put on the part.
MH

http://www.linkedin.com/pub/luke-autry/1b/510/566

 

[unclesyd]

We worked with both Reade and Brush Wellman, now the aforementioned Materion. Our end use was polymer jets and as component for an electrolytic cell.

There is a serious drawback to the use of these alloys and that is the Beryllium, that carries a highly toxic burden label with it.

http://www.reade.com/Products/Alloys/aluminum_beryllium_alloy_al_be.html

 

[Metalhead97]

Marsh91,

Since beryllium has little solubility in Al the beryllium phase will oxidize just like elemental beryllium. My suggestion is to talk to an application engineer at Materion about toxicity concerns.

MH

http://www.linkedin.com/pub/luke-autry/1b/510/566

 

[unclesyd]

Adding t o the above recommendation here is some additional information on the hazards of Beryllium from NGK