Low pressure thermoplastic molding materials for fiber-reinforced composite structures

Abstract

Fiber-reinforced molding materials and a related method of manufacture are provided. The fiber-reinforced molding materials include a fiber-reinforced tape that is moldable into complex structures at relatively low pressures while having high fiber concentrations. The fiber-reinforced tape includes a plurality of discontinuous fiber segments extending unidirectionally within a thermoplastic matrix material. The fiber-reinforced tape can be interwoven into multiple woven panels that are consolidated to form a fiber-reinforced mat. The fiber-reinforced mat is suitable for a wide range of molding applications where high strength and light weight are desired, while accommodating a variety of reinforcing fibers and thermoplastic resins.

1 . A method for forming a fiber-reinforced tape comprising:
 providing a unidirectional tape including a plurality of continuous fibers disposed in a thermoplastic resin; and   perforating the unidirectional tape to separate the plurality of continuous fibers into a plurality of discontinuous fiber segments.   
     
     
         2 . The method according to  claim 1  wherein adjacent ones of the plurality of discontinuous fiber segments are longitudinally offset from each other. 
     
     
         3 . The method according to  claim 1  wherein the unidirectional tape includes an upper surface and a lower surface, each perforation extending from the upper surface to the lower surface of the unidirectional tape. 
     
     
         4 . The method according to  claim 1  wherein the thermoplastic resin defines a molten temperature, the method further including heating the perforated unidirectional tape to above the molten temperature of the thermoplastic resin. 
     
     
         5 . The method according to  claim 4  further including pinch rolling the heated thermoplastic resin to substantially close the perforations in the unidirectional tape. 
     
     
         6 . The method according to  claim 5  further including taking-up the unidirectional tape into a spool. 
     
     
         7 . The method according to  claim 1  wherein the plurality of unidirectional fibers includes at least one of fiberglass strands, aramid strands, and carbon fiber strands. 
     
     
         8 . A fiber-reinforced tape comprising:
 a thermoplastic matrix material; and   a plurality of aligned discontinuous fiber segments extending unidirectionally within the thermoplastic matrix material.   
     
     
         9 . The fiber-reinforced tape of  claim 8  wherein laterally adjacent ones of the plurality of discontinuous fiber segments are longitudinally offset from each other. 
     
     
         10 . The fiber-reinforced tape of  claim 8  wherein laterally adjacent groups of the plurality of discontinuous fiber segments are longitudinally offset from each other. 
     
     
         11 . The fiber-reinforced tape of  claim 8  wherein the thermoplastic matrix material is selected from the group consisting of polyamide, polyethylene terephtalate, polyphenylene sulphide, polybutylene terephthalate, polysulfone, and polycarbonate. 
     
     
         12 . The fiber-reinforced tape of  claim 8  wherein the plurality of discontinuous fiber segments include at least one of fiberglass, aramid and carbon fiber. 
     
     
         13 . The fiber-reinforced tape of  claim 8  wherein the plurality of discontinuous fiber segments are between about 20% and 80% by weight of the fiber-reinforced tape. 
     
     
         14 . The fiber-reinforced tape of  claim 8  wherein the fiber-reinforced tape defines a width of at least about 0.125 inches and a thickness of between about 0.005 inches and 0.075 inches. 
     
     
         15 . A method for forming a thermoplastic composite structure, comprising:
 providing a first plurality of spaced apart fiber-reinforced weft strips;   providing a first plurality of spaced apart fiber-reinforced warp strips;   interweaving the first plurality of weft strips and the first plurality of warp strips to form a first woven panel, wherein the first plurality of weft strips and the first plurality of warp strips each include a plurality of discontinuous fiber segments extending unidirectionally within a thermoplastic matrix material.   
     
     
         16 . The method according to  claim 15  further including:
 providing a second plurality of spaced apart fiber-reinforced weft strips; 
 providing a second plurality of spaced apart fiber-reinforced warp strips; 
 interweaving the second plurality of weft strips and the second plurality of warp strips to form a second woven panel, wherein the second plurality of weft strips and the second plurality of warp strips each include a plurality of discontinuous fiber segments extending unidirectionally within a thermoplastic matrix material; and 
 layering the second woven panel over the first woven panel to form a multi-layered mat. 
 
     
     
         17 . The method according to  claim 16  further including:
 inserting the multi-layered mat into a mold; 
 applying heat and pressure to the multi-layered mat in the mold; and 
 removing a finished composite structure from the mold. 
 
     
     
         18 . A woven panel comprising:
 a plurality of spaced apart fiber-reinforced weft strips; and   a plurality of spaced apart fiber-reinforced warp strips being interwoven with the plurality of weft strips at a plurality of junctions, wherein the weft strips and the warp strips include a plurality of discontinuous fiber segments extending unidirectionally within a thermoplastic matrix material.   
     
     
         19 . The woven panel of  claim 18  wherein laterally adjacent ones of the plurality of discontinuous fibers are longitudinally offset from each other. 
     
     
         20 . The woven panel of  claim 18  wherein laterally adjacent groups of the plurality of discontinuous fibers are longitudinally offset from each other. 
     
     
         21 . The woven panel of  claim 18  wherein the thermoplastic matrix material is selected from the group consisting of polyamide, polyethylene terephtalate, polyphenylene sulphide, polybutylene terephthalate, polysulfone, and polycarbonate. 
     
     
         22 . The woven panel of  claim 18  wherein the plurality of discontinuous fibers includes at least one of fiberglass, aramid, and carbon fiber. 
     
     
         23 . The woven panel of  claim 18  wherein the plurality of discontinuous fibers are between about 20% and 80% by weight of the woven panel.