Reinforced panel structure

Abstract

A reinforced panel structure made by impregnating resin in a knitted fabric and allowing the resin to cure. The fabric comprises first and second spaced layers ( 1,2 ) which are interlinked by an intermediate pile layer ( 3 ) comprising two sets of ribs ( 4,5 ). The ribs ( 4 ) comprise monofilament yarns having a relatively high stiffness sufficient to provide a restoring force during impregnation of the fabric with resin. The ribs ( 5 ) are made from multifilament yarns, spun yarns or composite yarns, selected for desired properties of the finished fabric and/or for their wetting properties during impregnation. A method of making a reinforced panel structure is also described, this involving placing the impregnated fabric into a closed mold wherein it can expand, under the influence of the monofilament yarns, to fill the mold and thus produce a finished 3D article corresponding in shape to the interior of the mold.

1 . A structural panel made of a knitted fabric which is impregnated with a hardenable liquid material which is subsequently cured and/or hardened, said knitted fabric comprising first and second spaced layers which are interlinked by an intermediate pile layer comprising multiple ribs made of yarn, said panel being characterised in that said intermediate pile layer comprises at least some ribs of a first type and at least some ribs of a second type, different to the first type, and in that the ribs of said first type are made from yarns which are sufficiently stiff to provide the fabric with self-recovery characteristics when squeezed.  
     
     
         2 . A structural panel according to    claim 1    wherein the yarns of the first type are monofilament yarns.  
     
     
         3 . A structural panel according to    claim 2    wherein the yarns of the first type have a thickness in the range 0.05 to 0.25 mm.  
     
     
         4 . A structural panel according to any one of    claims 1    to    3    wherein the yarns of the second type are multifilament yarns.  
     
     
         5 . A structural panel according to any one of    claims 1    to    3    wherein the yarns of the second type are spun yarns, composite yarns, plied yarns or technical yarns.  
     
     
         6 . A structural panel as claimed in any one of the preceding claims wherein all of the yarns of the second type are of the same variety.  
     
     
         7 . A structural panel as claimed in any one of    claims 1    to    5    wherein said second yarns include mixtures of different sizes and/or varieties of yarn.  
     
     
         8 . A structural panel as claimed in any one of the preceding claims wherein the yarns of the first type and yarns of the second type are distributed evenly over the area of the fabric.  
     
     
         9 . A structural panel as claimed in any one of the preceding claims wherein at least the ribs of the first type have a length which is greater than the distance between the layers, and have a bowed shape.  
     
     
         10 . A structural panel as claimed in any one of the preceding claims wherein the yarns which comprise the ribs, at least of the first type, are slightly twisted so that they are torsionally biased in the knitted fabric.  
     
     
         11 . A method of manufacturing a structural panel made of a knitted fabric comprising first and second spaced layers which are interlinked by an intermediate pile layer comprising multiple ribs of a first type and multiple ribs of a second type, different from the first type, wherein the ribs of the first type are made from yarns which are sufficiently stiff to provide the fabric with self-recovery characteristics when squeezed, said method comprising impregnating the fabric with a hardenable liquid material, placing the fabric in a mould, and holding the fabric in the mould to permit hardening of the liquid material.  
     
     
         12 . A method as claimed in    claim 11    wherein, prior to introduction into the mould, the impregnated fabric is squeezed to ring out excess liquid material.  
     
     
         13 . A method as claimed in either one of claims  11  or  12  wherein the mould is of such shape and dimensions that, during its time in the mould, the impregnated squeezed fabric is selectively constrained and expands, under the influence of the ribs of the first type, to substantially fill the mould and thus produce a finished structural panel having a 3D shape corresponding to the interior of the mould.  
     
     
         14 . A method as claimed in any one of    claims 11    to    13    wherein the liquid material is a resin.