Wilson Audio did extensive empirical testing of contrained layer panels and they found out that the only method that worked well was to have two equal thickness panels bonded by a thin viscoelastic glue or barrier only no more than a few thousands of an inch thick.
If the inner layer is too thick and elastic it just acts like a spring and in some cases can actually amplifiy the resonances. If a thicker inner is used like bitumen then the lamination method should be a non viscoelasitc type of glue like epoxy so that no other compliances are added into the mix beyond the bitumen.
The other approach to dead panels is to have two thin but rigid skins on the outside of a very well internally damped middle. Like a foam core.
I think an extremely dead panel could be made up of half inch plywood and thin crossbracings with structural foam cores glued in all of the voids and then another half inch plywood panel on the inside.
All surfaces should be glued together with no voids. Then you could skin the inner and outer walls with fiberglass and epoxy or polyester resin to make it even stiffer with very little added thickness.
This would be a relatively low mass solution.
A high mass solution that has worked very well is to create a thin inner and outer wall of fiberglass and then pour in to the center a synthetic marble type of material such as epoxy and crushed stones.
This type of construction is very heavy, very rigid, and very dead.
If the inner layer is too thick and elastic it just acts like a spring and in some cases can actually amplifiy the resonances. If a thicker inner is used like bitumen then the lamination method should be a non viscoelasitc type of glue like epoxy so that no other compliances are added into the mix beyond the bitumen.
The other approach to dead panels is to have two thin but rigid skins on the outside of a very well internally damped middle. Like a foam core.
I think an extremely dead panel could be made up of half inch plywood and thin crossbracings with structural foam cores glued in all of the voids and then another half inch plywood panel on the inside.
All surfaces should be glued together with no voids. Then you could skin the inner and outer walls with fiberglass and epoxy or polyester resin to make it even stiffer with very little added thickness.
This would be a relatively low mass solution.
A high mass solution that has worked very well is to create a thin inner and outer wall of fiberglass and then pour in to the center a synthetic marble type of material such as epoxy and crushed stones.
This type of construction is very heavy, very rigid, and very dead.
Javor Pivka d.d. is a plywood manufacturer in my country..
in their brochure I've found an interesting material:
http://www.javor.si/javor/vp/img/VezanePlosce.pdf
page 3, FONOPAN, with special mixture of cork and rubber
perhaps any comments?
(more infos on http://www.javor.si/javor/ang/vp/specialne/transportni/img/fonopanENG.pdf)
in their brochure I've found an interesting material:
http://www.javor.si/javor/vp/img/VezanePlosce.pdf
page 3, FONOPAN, with special mixture of cork and rubber
perhaps any comments?
(more infos on http://www.javor.si/javor/ang/vp/specialne/transportni/img/fonopanENG.pdf)
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