Thermoformable lap having reinforcement fibres

Abstract

A thermoformable lap ( 1 ) includes a first web ( 3 ) and a second web ( 4 ) made of linking fibres ( 3 a, 4 a ) made of a first thermoreactivatable material having a first reactivation temperature. An intermediate layer ( 2 ) is arranged between the first web ( 3 ) and the second web ( 4 ), and includes reinforcement fibres ( 2 a) and granules ( 2 b ) of a second thermoreactivatable material having a second reactivation temperature that is higher than the first reactivation temperature. Certain sections ( 3 b, 4 b ) of linking fibres of the first and second webs ( 3, 4 ) penetrate into the intermediate layer ( 2 ) and partially adhere to one another and to the reinforcement fibres ( 2 a ) of the intermediate layer ( 2 ), ensuring the cohesion of the assembly. Such a lap can be manufactured at a lower cost and at high speed, and can be used for the production of parts by heat moulding.

1 . Thermoformable lap ( 1 ) based on reinforcement fibers linked to a thermoreactivatable material, comprising:
 a first outer layer and a second outer layer, having a first thermoreactivatable material with a first reactivation temperature,   an intermediate layer ( 2 ) arranged between the first and second outer layers,   the intermediate layer ( 2 ) having reinforcement fibers ( 2   a ) and a second thermoreactivatable material with a reactivation temperature higher than the first reactivation temperature,   wherein:   the second thermoreactivatable material is in the form of granules ( 2   b ),   the outer layers consist of a first web ( 3 ) and a second web ( 4 ) made of linking fibers ( 3   a ,  4   a ), at least the surface of which is made of the first thermoreactivatable material having a first reactivation temperature,   at least certain sections ( 3   b ,  4   b ) of linking fibers of the first and second webs ( 3 ,  4 ) penetrate into the intermediate layer ( 2 ) and partially adhere to one another and to the reinforcement fibers ( 2   a ) of the intermediate layer ( 2 ).   
     
     
         2 . Thermoformable lap ( 1 ) based on reinforcement fibers ( 2   a ) as claimed in  claim 1 , wherein the reinforcement fibers ( 2   a ) are glass fibers. 
     
     
         3 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein the first thermoreactivatable material is a polyamide/copolyamide (PA6/CoPA), a polyethylene, a copolypropylene, an acrylic or ethyl vinyl acetate. 
     
     
         4 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein the linking fibers ( 3   a ,  4   a ) consist of a single first thermoreactivatable material. 
     
     
         5 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein the linking fibers ( 3   a ,  4   a ) consist of a central core of polyamide, polyester or polypropylene and an outer sheath made of a first thermoreactivatable material with a first reactivation temperature that is lower than that of the central core. 
     
     
         6 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein the second thermoreactivatable material in granules ( 2   b ) is a polyamide. 
     
     
         7 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein the linking fibers ( 3   a ,  4   a ) are fiber sections. 
     
     
         8 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein, in the intermediate layer ( 2 ), the reinforcement fibers ( 2   a ) are sections of reinforcement fibers ( 2   a ) mixed with the granules ( 2   b ) of second thermoreactivatable material. 
     
     
         9 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , wherein the intermediate layer ( 2 ) is laminated in layers of reinforcement fibers ( 20   a ,  20   b ,  20   c ) and layers of granules of second thermoreactivatable material ( 20   d ,  20   e ). 
     
     
         10 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , containing from 200 to 1000 grams per square meter of reinforcement fibers ( 2   a ) and from 200 to 1000 grams per square meter of granules ( 2   b ) of second thermoreactivatable material. 
     
     
         11 . Thermoformable lap ( 1 ) based on reinforcement fibers as claimed in  claim 1 , being in the form of a reel-packaged continuous strip. 
     
     
         12 . Method for manufacturing a thermoformable lap ( 1 ) as claimed in  claim 1 , comprising the steps of:
 a) on a support, depositing a first web ( 3 ) made of linking fibers ( 3   a ),   b) depositing, on the first web ( 3 ), reinforcement fibers ( 2   a ) and granules ( 2   b ) of second thermoreactivatable material, forming an intermediate layer ( 2 ),   c) depositing, on the intermediate layer ( 2 ), a second web ( 4 ) made of linking fibers ( 4   a ),   d) performing a needling to make the sections of linking fibers ( 3   b ,  4   b ) of the first and second webs ( 3 ,  4 ) penetrate into the intermediate layer ( 2 ),   e) heating the assembly to a sufficient temperature to soften the linking fibers ( 3   a ,  4   a ,  3   b ,  4   b ) and render them adhesive,   f) cold calendering the assembly.   
     
     
         13 . Application of a thermoformable lap ( 1 ) as claimed in  claim 1  to the production of parts by thermoforming the lap.