Resistance welding methods and apparatus
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 method of resistance welding a first faying surface of a first composite article to a second faying surface of a second composite article, wherein one or both of the faying surfaces comprises a meltable or softenable material; the method comprising:
contacting the first and second faying surfaces to define a contact area therebetween;
providing a conductive element between the faying surfaces along a length of the contact area; the conductive element comprising a plurality of lower resistivity electrode portions spaced apart along the length of the contact area; wherein each electrode portion extends across a respective width of the contact area and each end thereof comprising an electrode extending from the contact area;
applying an electrical current between the electrodes of a first said electrode portion to raise the temperature of the meltable or softenable material and weld together a portion of the faying surfaces between the electrodes of the first electrode portion;
applying an electrical current between the electrodes of a second said electrode portion to raise the temperature of the meltable or softenable material and weld together a portion of the faying surfaces between the electrodes of the second electrode portion; and
applying an electrical current between electrodes of the first and second electrode portions to raise the temperature of the meltable or softenable material and weld together a portion of the faying surfaces of the first and second electrode portions.
2. The method of claim 1 , wherein the meltable or softenable material is a thermoplastic polymer.
3. The method of claim 1 , comprising resistively welding sequentially along a length of the contact area.
4. The method of claim 1 , comprising applying a force between the first and second composite articles, to urge the faying surfaces together.
5. The method of claim 1 , wherein the longitudinal portion comprises a conductive sheet, foil or fabric; and wherein each of the electrode portions of the conductive element further comprises a lateral portion comprising one or more layers of a conductive sheet, foil or fabric placed across a respective width of the longitudinal portion, and in electrical contact therewith.
6. The method of claim 1 , comprising assembling the conductive element, by providing a conductive longitudinal portion having a length corresponding to a length of the required contact area, providing a plurality of conductive lateral portions each sized to extend across a width of the required contact area; and bringing the plurality of lateral portions into electrical contact with the longitudinal portion, at each of a plurality of required locations spaced apart along the length of the longitudinal portion, to thereby form electrode portions having lower resistivity than adjacent portions of the conductive element.
7. The method of claim 6 , comprising cutting the longitudinal and/or lateral portions may from a conductive sheet material or a conductive fabric material.
8. The method of claim 1 , comprising placing the conductive element on the first faying surface, or assembling the conductive element in situ on the first faying surface.
9. The method of claim 1 wherein the first and second composite articles each comprise a matrix material, wherein the matrix material is the meltable or softenable material.
10. The method of claim 1 , wherein first and second composite articles each comprise more than one faying surface, wherein the method comprises:
contacting more than one first faying surface with more than one corresponding second faying surface, to define more than one contact area; providing a conducting element between the faying surfaces of each of the more than one contact areas; and applying a current between the electrodes of a first electrode portion, a second electrode portion and between electrodes of a first and a second electrode portion, of each of the more than one conductive elements;
wherein the composite structure to be formed by resistance welding the faying surfaces of the first and second composite article is a closed-geometry composite structure and a substantially enclosed volume is defined between the first and second composite articles;
the method further comprising remotely establishing electrical contact with one or more, or each of the electrodes extending from inner edge portions of contact areas within the substantially enclosed volume.