Method of manufacturing a sandwich panel, made of composite material, and a panel thereby obtained

Abstract

In order to manufacture a sandwich panel using the RTM technique, a stack comprising a core ( 10 ) with open cells, a film ( 12 ) of intumescent material covering each of the faces of the core ( 10 ), a dry barrier fabric ( 14 ) covering each of the films ( 12 ) and an overlay of dry fibers ( 16 ) covering each of the barrier fabrics is placed in a mold. During polymerization of the films ( 12 ), pressurization of the mold and the presence of the barrier fabrics ( 14 ) prevent penetration of the foam into the overlays ( 16 ). The resin is then injected into the mold and then polymerized, without danger of penetration into the cells of the core ( 10 ).

1 . Method of manufacturing a sandwich panel made of composite material, comprising the following steps: 
 placing, in a mold, an assembly comprising an open cell core, a film of intumescent material covering each of the faces of the core, a dry barrier fabric covering each of the films and an overlay of dry fibers covering each of the barrier fabrics, said barrier fabrics being sealed against a foam capable of being provided during the polymerization of said films and which can be wetted by a resin capable of being injected into the mold;    closing the mold;    pressurizing and heating the mold according to a cycle for the expansion and polymerization of the intumescent material, in a way that forms said foam, closing off the cells of the core on each of its faces, without impregnating the dry barrier fabrics;    evacuating the mold and injecting said resin into it in a manner that impregnates the overlays of dry fibers and the dry barrier fabrics;    carrying out a cycle for polymerization of the resin;    stripping the panel obtained from the mold.    
     
     
         2 . Method according to  claim 1 , in which films are used of a thickness such that after polymerization, said foam only fills the parts of the cells of the core which are close to the faces of the core.  
     
     
         3 . Method according to  claim 2 , in which films are used which have a thickness of about 2.5 mm.  
     
     
         4 . Method according to  claim 1 , in which barrier fabrics made of calendered polyamide are used.  
     
     
         5 . Sandwich panel made of a composite material comprising an open cell core and skins covering both faces of the core, said skins being formed of fibers and resin, a panel in which the cells of the core are closed off by a foam on each of said faces, and in which each of the skins comprises, starting from the core of the panel, a barrier fabric and a fiber overlay, both of which are impregnated with one and the same resin polymerized and stuck onto the core of the panel.  
     
     
         6 . Panel according to  claim 5 , in which said foam only fills the parts of the cells of the core which are close to the faces of the core.  
     
     
         7 . Panel according to  claim 5 , in which the barrier fabrics are produced in calendered polyamide.