Reinforcement textile armature and method for making same

Abstract

A textile armature that can be used for making composite materials or parts includes a central layer containing fiber segments of a first type of synthetic material previously submitted, before shaping it into a layer, to a process imparting a permanent crimp; outer layers including a mixture of segments of chemical fibers previously submitted to a process imparting a permanent crimping, and of segments of reinforcing fibers, at least some of the segments of chemical fibers of the outer layers penetrate along a portion of their length into the central layer. First segments of chemical fibers of the outer layers are bonded at least partially between them and to the other fiber segments of the textile armature.

1 . Textile armature ( 1 ) usable for the production of composite materials or parts, comprising:
 a central layer ( 3 ) based on chopped fiber sections ( 3   a ) of a first type of synthetic material that have received before their formation into a layer a treatment communicating to them a permanent crimp,   external layers ( 21 ,  22 ) disposed on opposite sides of the central layer ( 3 ),   characterized in that:   the external layers ( 21 ,  22 ) include chopped chemical fiber sections ( 7 ) that have previously received a treatment conferring on them a permanent crimp and chopped reinforcement fiber sections ( 4 ),   at least some of the chopped chemical fiber sections ( 7 ) penetrate over a part of their length into the central layer ( 3 ),   the chopped chemical fiber sections ( 7 ) include at least first chopped chemical fiber sections ( 70 ) including at least one surface layer ( 7   b ) of a thermoplastic material having a melting point lower than or equal to that of the chopped fiber sections ( 3   a ) of the central layer ( 3 ),   the first chopped chemical fiber sections ( 70 ) of the external layers ( 21 ,  22 ) adhere at least partly to each other and to the other chopped fiber sections ( 3   a ,  4 ) of the textile armature ( 1 ).   
     
     
         2 . Textile armature ( 1 ) according to  claim 1 , wherein the chopped fiber sections ( 3   a ) of the central layer ( 3 ) are of polypropylene, polyester or polyamide. 
     
     
         3 . Textile armature ( 1 ) according to  claim 1 , wherein the chopped fiber sections ( 3   a ) of the central layer ( 3 ) have at least two different unitary linear densities. 
     
     
         4 . Textile armature ( 1 ) according to  claim 1 , wherein the chopped chemical fiber sections ( 7 ) of the external layers ( 21 ,  22 ) have a cross section with a diameter less than that of the chopped reinforcement fiber sections ( 4 ). 
     
     
         5 . Textile armature ( 1 ) according to  claim 1 , wherein the first chopped chemical fiber sections ( 70 ) of the external layers ( 21 ,  22 ) are of a thermoplastic material with a melting point lower than that of the chopped fiber sections ( 3   a ) of the central layer ( 3 ). 
     
     
         6 . Textile armature ( 1 ) according to  claim 1 , wherein:
 the first chopped chemical fiber sections ( 70 ) of the external layers ( 21 ,  22 ) are two-component chopped fiber sections having a central core ( 7   a ) of a first component and an external sheath ( 7   b ) of a second component,   the melting point of the first component of the central core ( 7   a ) is higher than that of the second component of the external sheath ( 7   b ).   
     
     
         7 . Technical armature ( 1 ) according to  claim 6 , wherein:
 the central core ( 7   a ) is of polyamide, polyester or polypropylene,   the external sheath ( 7   b ) is of a thermoplastic material with a melting point lower than that of the chopped fiber sections ( 3   a ) of the central layer ( 3 ).   
     
     
         8 . Textile armature ( 1 ) according to  claim 1 , wherein the chopped chemical fiber sections ( 7 ) in the external layers ( 21 ,  22 ) include only first chopped chemical fiber sections ( 70 ). 
     
     
         9 . Textile armature ( 1 ) according to  claim 1 , wherein the chopped chemical fiber sections ( 7 ) in the external layers ( 21 ,  22 ) include a mixture of first chopped chemical fiber sections ( 70 ) and second chopped chemical fiber sections ( 71 ). 
     
     
         10 . Textile armature ( 1 ) according to  claim 1 , wherein the chopped chemical fiber sections ( 7 ) and the chopped reinforcement fiber sections ( 4 ) in the external layers ( 21 ,  22 ) are mixed in a generally homogeneous manner. 
     
     
         11 . Textile armature according to  claim 1 , wherein the external layers ( 21 ,  22 ) are stratified, comprising an external stratum ( 21   c ,  22   c ) essentially of chopped chemical fiber sections ( 7 ), with or without an internal stratum ( 21   a ,  22   a ) essentially of chopped chemical fiber sections ( 7 ) and with an intermediate stratum ( 21   b ,  22   b ) essentially of reinforcement fibers ( 4 ). 
     
     
         12 . Method of fabricating a textile armature ( 1 ) usable for the production of composite materials or parts, including the following successive steps:
 a) providing a central layer ( 3 ) based on chopped fiber sections ( 3   a ) of a first type of synthetic material that have received before their formation into a layer a treatment conferring on them a permanent crimp,   b) disposing on opposite sides of the central layer ( 3 ) an external layer ( 21 ,  22 ) including chopped reinforcement fiber sections ( 4 ) and chopped chemical fiber sections ( 7 ) with a permanent crimp including at least first chopped chemical fiber sections ( 70 ) having at least one surface layer ( 7   b ) of a second type of thermoplastic synthetic material with a melting point lower than or equal to that of the first type of synthetic material,   c) effecting preliminary needle-punching to cause the chopped chemical fiber sections ( 7 ), in particular the first chopped chemical fiber sections ( 70 ), to penetrate into the central layer ( 3 ) over part of their length,   d) heating the textile armature ( 1 ) to soften at least superficially and to render adherent at least said first chopped chemical fiber sections ( 70 ).   
     
     
         13 . Method according to  claim 12 , further including after the step d) a step e) during which the textile armature ( 1 ) is cold-rolled. 
     
     
         14 . Method according to  claim 12 , wherein:
 the chopped chemical fiber sections ( 7 ) of the external layers ( 21 ,  22 ) have a diameter less than that of the chopped reinforcement fiber sections ( 4 ),   the preliminary needle-punching of the step c) is effected by means of needles ( 8 ) that have barbs ( 8   a ) adapted to entrain preferentially the chopped chemical fiber sections ( 7 ), in particular the first chopped chemical fiber sections ( 70 ), but not to entrain significantly the larger diameter chopped reinforcement fiber sections ( 4 ).   
     
     
         15 . Method according to  claim 12 , wherein during the step d) the heating is effected by circulating hot air through the textile armature ( 1 ).