Composite Structure

Abstract

A composite structure, such as a structural member ( 12 ), is formed by the steps of knitting a three dimensional pre-form ( 17 ) from one or more selected fibres such as natural fibres selected from hemp, cotton, flax, jute and synthetic fibres such as boron aramide fibres, carbon fibres, glass fibres and polymer based fibres, using a three dimensional knitting machine ( 16 ). The pre-form ( 17 ) has a shape commensurate with that of the structure ( 12 ) to be formed. The pre-form ( 17 ) is caused to take its three dimensional shape by inflating or otherwise expanding the pre-form such as by injecting a foamable synthetic plastics material into the interior of the pre-form, and thereafter fixing the shape of the shaped fibres to form the composite structure.

What is claimed is: 
     
         1 - 27 . (canceled) 
     
     
         28 . A knitted three dimensional pre-form formed by knitting one of composite natural fibers and synthetic fibers into a knitted structure which, when one of inflated and expanded to take a three dimensional shape, takes the shape of a composite structure to be formed, the pre-form fibres being adapted to be fixed to maintain the three dimensional shape. 
     
     
         29 . A composite structure comprising:
 a knitted, three dimensional pre-form having a three dimensional shape commensurate with that of the structure to be formed, the pre-form being knitted using at least one selected fibre, and   the fibers being fixed when the pre-form is one of inflated and expanded to take the three dimensional shape whereby the fixed three dimensional shape defines the composite structure.   
     
     
         30 . A composite structure as claimed in  claim 57  wherein the three dimensional shape is fixed by impregnating the fibers with a curable resin and subsequently curing the resin while the pre-form is in the inflated condition. 
     
     
         31 . (canceled) 
     
     
         32 . A composite structure as claimed in  claim 57  wherein the structure is designed such that the knitted pre-form forms, in its three dimensional shape, a composite space frame having the shape of the composite structure to be formed. 
     
     
         33 . A composite structure as claimed in  claim 57  wherein the pre-form is knitted using a mixture of natural and synthetic fibers. 
     
     
         34 . A composite structure as claimed in  claim 57  wherein the fibers are selected from the group consisting of hemp, cotton, flax, jute and synthetic fibers including boron aramide fibers, carbon fibers, glass fibres and polymer based fibers. 
     
     
         35 . A composite structure as claimed in  claim 57  wherein the fibers are aligned and arranged to utilise unique properties of the selected fibers whereby fibers are incorporated into the knitted product to at least one of:
 provide strength in at least one direction and 
 provide stiffness in predetermined areas of the pre-form. 
 
     
     
         36 . A composite structure as claimed in  claim 57  wherein the fibers,
 when one of:
 heated, 
 subjected to microwaves, and 
 subjected to other forms of energy, 
 
 one of:
 cure and 
 set 
 
 
       so as to retain the three dimensional shape of the knitted pre-form. 
     
     
         37 . A composite structure as claimed in  claim 57  wherein the foam material comprises a foamable synthetic plastics material injected into the interior of the knitted pre-form and caused to expand within the knitted pre-form to cause the knitted fibers to take the three dimensional geometry. 
     
     
         38 . A composite structure as claimed in  claim 37  wherein the foamed synthetic plastics material comprises a material selected from the group consisting of polyurethane, polypropylene, and polystyrene foam. 
     
     
         39 . A composite structure as claimed in  claim 57 , wherein the knitted pre-form expanded by the foam material is sprayed with a resin binder which is subsequently cured. 
     
     
         40 . A composite structure as claimed in  claim 57  wherein the knitted pre-form, expanded by the foam material, is one of dipped and immersed in a resin binder. 
     
     
         41 . A composite structure as claimed in  claim 39  wherein the resin binder is one of a polyester and vinyl ester resin. 
     
     
         42 . A composite structure as claimed in  claim 57  wherein at least one of the fibers forming the three dimensional knitted pre-form is formed of a material able to be used in the knitted product but curable by application of one of UV light, heat, microwaves and other energy, to harden and bind with other fibers to form the three dimensional composite structure. 
     
     
         43 . (canceled) 
     
     
         44 . A composite structure as claimed in  claim 57  wherein the knitted pre-form is knitted so that, in areas of high stress or high load bearing regions of the formed composite structure, the knitted pre-form will have a pattern and thickness, and be formed of fibers appropriate to resist the stresses and loads. 
     
     
         45 . (canceled) 
     
     
         46 . A composite structure as claimed in  claim 57  wherein an outer shape of the composite structure to be formed is defined by one of jigs and fixtures supporting the pre-form when the pre-form is expanded by injection with the foam material. 
     
     
         47 . A composite structure as claimed in  claim 57  wherein resin coated fibres are introduced to the pre-form during the knitting stage, the fibres being coalesced with the application of heat. 
     
     
         48 . A composite structure as claimed in  claim 57  wherein the resin matrix binder is selected to be sprayable onto the expanded pre-form. 
     
     
         49 . A composite structure as claimed in  claim 57  wherein the resin binder comprises a two part epoxy binder resin that is adapted to be cured by applying a reactive agent. 
     
     
         50 . A composite structure as claimed in  claim 57  wherein the knitted pre-form is a seamless single piece. 
     
     
         51 . A composite structure as claimed in  claim 57  wherein the knitted pre-form is made in a number of separate, knitted pre-form sections and subsequently assembled to produce a composite pre-form. 
     
     
         52 . (canceled) 
     
     
         53 . A composite structure as claimed in  claim 57  further comprising a plurality of one of:
 tethers, 
 shape defining fibres and 
 shape defining threads 
 extending between opposed wall portions of the pre-form, at least one of internally and externally, to hold the pre-form to a desired shape when expanded. 
 
     
     
         54 - 56 . (canceled) 
     
     
         57 . A composite structure, comprising:
 a knitted three-dimensional pre-form, the pre-form being knitted with a tailored fiber type, gauge, orientation, density, knit pattern and stitch resulting in localized regions of higher to lower load-bearing capability within the three-dimensional geometry of the composite structure, wherein the localized regions provide resistance to loads and stresses on the composite structure;   a foam material disposed in at least one interior space thereof to expand the pre-form into the three-dimensional geometry; and   a cured and set resin binder infused into the expanded pre-form to fix the three-dimensional geometry of the composite structure.   
     
     
         58 . The composite structure of  claim 57 , wherein the resin binder is selected to be curable by application of one of:
 ultra violet light;   heat; and   other energy.   
     
     
         59 . A composite structure, comprising:
 a knitted three-dimensional pre-form having walls enclosing at least one interior space, the pre-form being adapted to adopt a required three-dimensional shape of said composite structure;   a foam material disposed in said at least one interior space to expand the pre-form into the three-dimensional geometry; and   a cured and set resin binder infused into the expanded pre-form to fix the three-dimensional geometry of the composite structure.