Structured flock fiber reinforced layer

Abstract

Various embodiments of structured flock fiber reinforced layers include fibrous organic polymer composite reinforcing materials that have been “pre-flocked” with Z-Axis reinforcing fibers. These “pre-flocked” fibrous materials (woven, knitted, mat, nonwoven or pre-pregs) are then supplied as “off-the-shelf,” “ready-to-use,” already flock reinforced, dry to the touch, pre-manufactured, storable, inventoried organic polymer composite structured flock fiber reinforced layers that are ready as needed to be laid-up and impregnated with matrix resin and cured to form fiber based z-directional reinforced composites having enhanced inter-laminar strength, impact toughness, transmission properties (electrical and thermal conduction) and coefficient of thermal expansion are provided. Methods for forming such reinforced layers are also provided.

1 . A structured flock fiber reinforced layer comprising:
 a fibrous laminar base-ply substrate comprising a plurality of fabric yarns forming a plurality of interstices;   a thin adhesive sizing layer disposed on the fibrous laminar base-ply substrate;   a plurality of reinforcing flock fibers, a majority of which are oriented substantially perpendicular to a first surface of the fibrous laminar base-ply substrate, the substantially perpendicularly oriented reinforcing flock fibers being partially embedded in the plurality of interstices, wherein the plurality of reinforcing flock fibers are bonded to surfaces of the plurality of fabric yarns by the thin adhesive sizing layer for subsequent composite ply material assembly; and   wherein the sized and flocked fibrous laminar base-ply substrate remains flexible to conform to contour layups.   
     
     
         2 . The structured flock fiber reinforced layer of  claim 1 , wherein the thin adhesive sizing layer is a resin and comprises one of:
 a sprayable polyurethane lacquer coating;   a sprayable epoxy-based lacquer coating;   a sprayable water based acrylic adhesive;   a dilute water dip-able, water based acrylic adhesive; and   a dilute solvent based dip-able resin/lacquer coating system.   
     
     
         3 . The structured flock fiber reinforced layer of  claim 1 , wherein the plurality of a reinforcing flock fibers has a flock density of about 70 fibers/mm 2  to about 200 fibers/mm 2 . 
     
     
         4 . The structured flock fiber reinforced layer of  claim 1 , wherein the plurality of reinforcing flock fibers has an average fiber length of about 0.5mm to about 2.0 mm. 
     
     
         5 . The structured flock fiber reinforced layer of  claim 1 , wherein the plurality of reinforcing flock fibers has an average fiber fineness of about 1.0 denier to about 20 denier. 
     
     
         6 . The structured flock fiber reinforced layer of  claim 1 , wherein the plurality of reinforcing flock fibers are selected from a group consisting of synthetic fibers, glass fibers, carbon fibers, natural fibers, and metal fibers. 
     
     
         7 . The structured flock fiber reinforced layer of  claim 1  further comprising a release sheet disposed adjacent to free ends of the plurality of reinforcing flock fibers. 
     
     
         8 . The structured flock fiber reinforced layer of  claim 7  wherein the release sheet comprises one of a thin, light-weight fabric lightly flocked with a plurality of high denier packaging flock fibers; and
 a thin, light-weight fabric lightly flocked with a plurality of high denier packaging flock fibers; and 
 wherein the plurality of high denier packaging flock fibers are longer and stiffer than the plurality of reinforcing flock fibers positioned on the surface of the fibrous laminar base-ply substrate. 
 
     
     
         9 . The structured flock fiber reinforced layer of  claim 1  wherein the majority of perpendicularly oriented reinforcing flock fibers being are embedded in the fibrous laminar base-ply substrate to a depth of approximately about 0.05 to about 0.1 mm. 
     
     
         10 . A method for fabricating a flock fiber composite reinforcement layer comprising:
 applying a thin coating of resinous flock adhesive sizing to a dry substrate, the dry substrate comprising a plurality of fabric yarns forming a plurality of interstices; and   flocking a plurality of reinforcing flock fibers onto a first surface of the sized dry substrate comprising:   embedding the plurality of reinforcing flock fibers into the plurality of interstices while the resinous flock adhesive sizing is still fluidic and uncured; and   attaching the plurality of reinforcing flock fibers to surfaces of the plurality of fabric yarns by curing the adhesive sizing.   
     
     
         11 . The method of  claim 10 , wherein flocking a plurality of reinforcing flock fibers further comprises one of:
 vacuum assisted flocking (VAF);   shaking and vibration assisted flocking (SAF); and   a combination of VAF and SAF.   
     
     
         12 . The method of  claim 10 , wherein the resinous flock adhesive sizing comprises one of:
 a water based acrylic adhesive;   a sprayable polyurethane lacquer coating;   a sprayable epoxy-based lacquer coating;   a sprayable water based acrylic adhesive;   a dilute water dip-able, water based acrylic adhesive; and   a dilute solvent based dip-able resin/lacquer coating system.   
     
     
         13 . The method of  claim 10 , wherein applying a thin coating of resinous flock adhesive sizing to the dry substrate comprises applying uncured resinous flock adhesive sizing at a thickness of about 0.01 mm to about 0.05 mm. 
     
     
         14 . The method of  claim 10 , further comprising applying a release sheet adjacent to free ends of the plurality of the flocked reinforcing flock fibers. 
     
     
         15 . A structured flock fiber reinforced layer comprising:
 a pre-preg composite reinforcement ply layer structure, including a B-staged epoxy matrix outer surface; a plurality of reinforcing flock fibers, a majority of which are oriented substantially perpendicular to a first surface of the pre-preg composite reinforcement ply structure, the majority of substantially perpendicularly oriented reinforcing flock fibers being partially embedded in the B-staged epoxy matrix outer surface of the B-staged epoxy resin pre-preg composite reinforcement ply structure, wherein the plurality of reinforcing flock fibers are secured in place within the B-staged epoxy matrix outer surface for subsequent composite ply material assembly; and   wherein the pre-preg composite reinforcement ply structure remains flexible to conform contour layups.   
     
     
         16 . A method for fabricating a flock fiber composite reinforcement layer comprising:
 providing a pre-preg composite reinforcement ply structure, including B-stage epoxy matrix;   softening the B-stage epoxy matrix of the pre-preg composite reinforcement ply structure to lower a B-stage epoxy matrix viscosity forming a tacky surface; and   flocking a plurality of reinforcing flock fibers onto a first surface of the pre-preg composite reinforcement ply structure such that the plurality of reinforcing flock fibers penetrate an outer surface of the B-staged epoxy matrix.   
     
     
         17 . The method of  claim 16 , wherein softening the B-stage epoxy matrix comprises heating the B-stage epoxy matrix after the pre-preg composite reinforcement ply structure is initially manufactured; and
 further comprising cooling down the epoxy matrix of the pre-preg composite reinforcement ply structure.   
     
     
         18 . The method of  claim 17 , wherein heating the epoxy matrix of the pre-preg composite reinforcement ply structure comprises heating the B-staged epoxy matrix such that the B-staged epoxy matrix becomes tacky enough to accept impinging flock fibers while the pre-preg composite reinforcement ply structure remains partially uncured. 
     
     
         19 . The method of  claim 18 , wherein heating the epoxy matrix of the pre-preg composite reinforcement ply structure comprises heating the epoxy matrix to a maximum temperatures of about 65° C. 
     
     
         20 . The method of  claim 16 , wherein flocking a plurality of reinforcing flock fibers comprises up-flocking; and
 wherein the method further comprises:
 orienting the flocked pre-preg composite reinforcement ply structure, flock side down; and 
 shaking the composite reinforcement layer vigorously to remove unsecured flock fibers; and 
 refreezing the composite reinforcement layer to inhibit further curing of the B-staged epoxy matrix of the pre-preg composite reinforcement ply structure. 
   
     
     
         21 . The method of  claim 16 , wherein softening the B-stage epoxy matrix comprises:
 spraying the pre-preg surface with a solvent for the B-staged epoxy matrix; and   applying a thin coating of B-staged epoxy resin to the surface of the pre-preg composite reinforcement ply structure.