Resistance welding methods and apparatus

Abstract

Disclosed is a method of resistance welding between composite articles. A conductive element is provided between faying surfaces, having a plurality of lower resistivity electrode portions spaced apart along the length of the contact area between the composite articles. The electrode portions can be used to spot weld across the electrode portions, and along a longitudinal portion of the conductive element between the electrode portions by application of an electrical current. Also disclosed are apparatus for use in the resistance welding methods and composite articles and structures and elements incorporating the conductive element.

1 . A composite structure comprising:
 a first composite article;   a second composite article;   a join having an area defined by respective faying surfaces of the first and second composite articles, wherein the join comprises a meltable or softenable material by which the composite articles are held together; and   a conductive element in the join between the faying surfaces or embedded within one of the said faying surfaces along the join, the conductive element comprising:
 a longitudinal portion having a length corresponding substantially to the length of the join, and 
 a plurality of lower resistivity electrode portions spaced apart along a length of the conductive element, each of the plurality of lower resistivity electrode portions extending across a respective width of the conductive element and comprising an electrode at the ends thereof, wherein the electrodes extend beyond a respective width of the join. 
   
     
     
         2 . The composite structure according to  claim 1 , wherein the meltable or softenable material is present as a layer between the first and second composite articles. 
     
     
         3 . The composite stricture according to  claim 1 , wherein the meltable or softenable material is a matrix material of one or both of the first and second composite articles. 
     
     
         4 . The composite structure of  claim 1 , wherein the meltable or softenable material is a thermoplastic polymer. 
     
     
         5 . The composite structure of  claim 1 , wherein the composite structure is a carbon fibre composite structure. 
     
     
         6 . The composite structure of  claim 1 , wherein the conductive element comprises at least one of: a conductive mesh, a foil formed as a lattice, a conductive fabric, a conductive paint, and a conductive ink. 
     
     
         7 . The composite structure of  claim 1 , wherein each of the first and second composite articles comprises a primary faying surface and a secondary faying surface, wherein the join further comprises a primary join and a secondary join, with a corresponding primary and secondary conductive element therein, wherein the composite structure is a closed geometry structure having an enclosed volume defined between the primary and secondary joins. 
     
     
         8 . The composite structure of  claim 7 , wherein the enclosed volume defined between the primary and secondary joins is a cavity having one or more openings, wherein the enclosed volume is bounded by greater than ninety percent of external area of the enclosed volume by the composite structure. 
     
     
         9 . An electrical connection apparatus for use in resistance welding to form a closed-geometry composite structure defining a high-aspect ratio substantially enclosed volume, the electrical connection apparatus comprising:
 a probe arrangement comprising:
 a foot portion having an engagement surface for engaging a surface of the substantially enclosed volume and comprising an electrical contact element; 
 a shoulder portion having an engaging surface for engaging an opposite surface of the substantially enclosed volume; 
 a reconfigurable body portion operatively coupled between the foot portion and the shoulder portion, wherein the reconfigurable body portion is remotely configurable between a contracted configuration and an expanded configuration; wherein in the contracted position the engagement surfaces are spaced apart by less than a distance between opposed surfaces of a substantially enclosed volume defined between composite articles, and in the expanded configuration the engagement surfaces are further spaced apart sufficient to engage opposed surfaces of the substantially enclosed volume and to urge the electrical contact element into electrical contact with an inner electrode within the substantially enclosed volume. 
   
     
     
         10 . The electrical connection apparatus of  claim 9 , wherein the reconfigurable body portion is pneumatically or hydraulically reconfigurable. 
     
     
         11 . The electrical connection apparatus of  claim 10 , wherein the reconfigurable body portion comprises an inflatable chamber. 
     
     
         12 . The electrical connection apparatus of  claim 9 , wherein the foot portion comprises a primary electrical contact element oriented towards a first side of the probe arrangement, and a secondary electrical contact element oriented towards an opposite second side of the probe arrangement. 
     
     
         13 . The electrical connection apparatus of  claim 9 , comprising two probe portions spaced apart by a longitudinal distance between longitudinally adjacent inner electrodes of the composite structure being welded. 
     
     
         14 . A composite structure comprising:
 a first composite article;   a second composite article;   a join having an area defined by respective faying surfaces of the first and second composite articles, wherein the join comprises a meltable or softenable material by which the composite articles are held together, wherein the join has a length and a width; and   a conductive element in the join between the faying surfaces or embedded within one of the said faying surfaces along the join, the conductive element having a mesh or lattice configuration with pores or apertures through which the meltable or softenable material extends through, the conductive element comprising:
 a longitudinal portion having a length extending at least a portion of the length of the join, and 
 a plurality of lower resistivity electrode portions spaced apart along the length of the longitudinal portion, each of the plurality of lower resistivity electrode portions extending at least partially across a respective width of the conductive element and comprising an electrode at ends thereof, wherein the electrodes extend beyond the respective widths of the join. 
   
     
     
         15 . The composite structure according to  claim 14 , wherein the meltable or softenable material is present as a layer between the first and second composite articles or the meltable or softenable material is a matrix material of one or both of the first and second composite articles. 
     
     
         16 . The composite structure according to  claim 14 , wherein the plurality of lower resistivity electrode portions are comprised of thicker conductive material than adjacent portions of the conductive element. 
     
     
         17 . The composite structure of  claim 14 , wherein the meltable or softenable material is at least one of a thermoplastic polymer, an epoxy resin material, and a vitrimer material. 
     
     
         18 . The composite structure of  claim 14 , wherein the first composite article and the second composite article comprises at least one of carbon fibre, aramid fibre, glass fibre, and plant fibre. 
     
     
         19 . The composite structure of  claim 14 , wherein the conductive element comprises at least one of: a conductive mesh, a foil formed as a lattice, a conductive fabric, a conductive paint, and a conductive ink. 
     
     
         20 . The composite structure of  claim 14 , wherein each of the first and second composite articles comprises a primary faying surface and a secondary faying surface, wherein the join further comprises a primary join and a secondary join, with a corresponding primary and secondary conductive element therein, wherein the composite structure is a closed geometry structure having an enclosed volume defined between the primary and secondary joins.