I'm installing a lot of stereo equipment into my car. As well as making some custom enclosures for the speakers out of GRP, I also need to stiffen the roof.

My idea is to get some 10mm thick 3/4" Aluminium honeycomb and some polyurethane 2 part expanding foam to make some panels to bond to the roof.

Would this be a suitable way to add significant strength/stiffness to a metal panel. here's a pic of my car roof

Each of those section is 900mm x 300mm. Any advice or other ideas welcome.

Cheers

I think most people damp the roof rather than stiffen it.  From what I've seen a couple of layers of self adhesive dynamat is the method of choice although you can do a similar job with several coats of stonechip.  It will be significantly easier than adding composite structures.

I'm well aware of Dynamat and Silent Coat and all the various methods of Constrained Layer Damping. All of which are expensive for what they are and also very heavy. The roof isn't going to have speakers in it and doesn't need to be treated the same as a door or floor pan where road noise or resonance from a high power speaker is the issue.

I believe my idea is cheaper and also much lighter. It would also provide insulation from hot/cold conditions.

What I need to know is if this idea will provide the benefits I require.

Do you have any idea how you will fill every little hole with expanding polyurethane? :p 

Matthieu Libeert
Founder MAT2 Composites X Sports
website: www.mat2composites.com