Methods of randomly dispersing chopped carbon fiber and consolidating the materials together to make a fiber reinforcement mat

Abstract

Methods of randomly dispersing chopped carbon fiber and consolidating the materials together to make a fiber reinforcement mat are disclosed. The term “Z-mat” is used to describe the claimed random fiber mat in which the chopped fibers are not preferentially oriented in either the x or y direction in the in-plane directions of the mat. The stiffness in the Z-mat is substantially independent of the test direction in the plane of the mat. The Z-mat offers the distinct advantages of higher stiffness and lighter weight.

1 . An apparatus for producing a chopped fiber mat, comprising a tow spreader for spreading a fiber tow prior to a chopper that chops said fiber tow into chopped fiber bundles, and a randomizer that breaks up the chopped fiber bundles to produce fibers having a random orientation in a direction in the plane of the chopped fiber mat.  
     
     
         2 . The apparatus of  claim 1 , wherein the chopped fiber mat has a stiffness that is substantially independent of a test direction in the plane of the chopped fiber mat.  
     
     
         3 . The apparatus of  claim 2 , wherein the chopped fiber mat has a ratio of a maximum-in-plane stiffness to a minimum-in-plane stiffness of 1.3.  
     
     
         4 . The apparatus of  claim 2 , wherein the chopped fiber mat has a ratio of a maximum-in-plane stiffness to a minimum-in-plane stiffness of 1.2.  
     
     
         5 . The apparatus of  claim 2 , wherein the chopped fiber mat has a ratio of a maximum-in-plane stiffness to a minimum-in-plane stiffness of 1.1.  
     
     
         6 . The apparatus of  claim 1 , wherein the fiber tow is a carbon fiber tow.  
     
     
         7 . The apparatus of  claim 1 , wherein the chopped fiber mat further comprises a backing.  
     
     
         8 . The apparatus of  claim 7 , wherein the backing is selected from the group consisting of a fiberglass veil, a thermoplastic veil, a thermoplastic scrim, a fiberglass scrim, a thermoplastic film, and combinations thereof.  
     
     
         9 . The apparatus of  claim 1 , wherein the fiber tow comprises a sizing and the chopped fiber mat comprises a powder binder.  
     
     
         10 . The apparatus of  claim 8 , wherein the sizing is a polyester-containing sizing and the powder binder is a polyester powder binder.  
     
     
         11 . A method for producing a chopped fiber mat, comprising spreading a fiber tow, chopping the fiber tow to produce chopped fiber bundles and breaking up the chopped fiber bundles to produce fibers having a random orientation in a direction in the plane of the chopped fiber mat.  
     
     
         12 . The method of  claim 11 , wherein the chopped fiber mat has a stiffness that is substantially independent of a test direction in the plane of the chopped fiber mat.  
     
     
         13 . The method of  claim 12 , wherein the chopped fiber mat has a ratio of a maximum-in-plane stiffness to a minimum-in-plane stiffness of 1.3.  
     
     
         14 . The method of  claim 12 , wherein the chopped fiber mat has a ratio of a maximum-in-plane stiffness to a minimum-in-plane stiffness of 1.2.  
     
     
         15 . The method of  claim 12 , wherein the chopped fiber mat has a ratio of a maximum-in-plane stiffness to a minimum-in-plane stiffness of 1.1.  
     
     
         16 . The method of  claim 11 , wherein the fiber tow is a carbon fiber tow.  
     
     
         17 . The method of  claim 11 , wherein the chopped fiber mat further comprises a backing.  
     
     
         18 . The method of  claim 17 , wherein the backing is selected from the group consisting of a fiberglass veil, a thermoplastic veil, a thermoplastic scrim, a fiberglass scrim, a thermoplastic film, and combinations thereof.  
     
     
         19 . The method of  claim 11 , wherein the fiber tow comprises a sizing and the chopped fiber mat comprises a binder.  
     
     
         20 . The method of  claim 19 , wherein the sizing is selected from the group consisting of a thermosetting sizing, a thermoplastic sizing, and combinations thereof.  
     
     
         21 . The method of  claim 20 , wherein the thermosetting sizing is selected from the group consisting of an epoxy-containing sizing and a polyester-containing sizing.  
     
     
         22 . The method of  claim 20 , wherein the thermoplastic sizing is selected from the group consisting of a polypropylene-containing sizing and a polyethylene-containing sizing.  
     
     
         23 . The method of  claim 19 , wherein the binder is selected from the group consisting of a thermosetting binder, a thermoplastic binder, and combinations thereof.  
     
     
         24 . The method of  claim 23 , wherein the thermosetting binder is selected from the group consisting of an epoxy-containing binder and a polyester-containing binder.  
     
     
         25 . The method of  claim 23 , wherein the thermoplastic binder is selected from the group consisting of a polypropylene-containing binder and a polyethylene-containing binder.  
     
     
         26 . The method of  claim 23 , wherein the thermoplastic binder is selected from the group consisting of a powder-containing binder and a fiber-containing binder.