Composite material

Sealable element comprising:

• a first piece, consisting of two plates separated from each other and linked by a means provided with several openings to define a room or groove between said two plates;
• a second piece consisting of two plates separated from each other and linked by a means provided with several openings to define a room or groove between said two plates;
• and a composite material partly located in the room or groove of the first piece and partly located in the room of the second piece, with the composite material comprising a support including a first plate and a second plate disposed parallel to and spaced from one another, and means for connecting the plates together to form a room or groove between the two plates of the support, and a heat foamable material arranged in said room or groove of the support, and with said support being made of a heat resistant material with a melting temperature higher than the temperature required for the foaming of the foamable material, so that said foamable material, when heat is applied thereto, expands to a foamed form extending out of the room or groove of the support through at least one opening of the support or formed in the support due to foaming pressure and into the rooms or groove of the first and second pieces reaching the means linking the plates of said pieces so as to push the pieces away from each other.