Joining method and apparatus
A first aspect of the invention provides a method of joining a part to a composite component, the composite component comprising fibres impregnated with a matrix material, and the part comprising a plurality of projections, the method comprising: inserting the projections into the composite component; and pre-heating the projections before they are inserted into the composite component, so that the projections are at a higher temperature than the composite component as they are inserted into the composite component. The projections locally heat the matrix material of the composite component as they are pushed into the composite component. Increased temperature during insertion is advantageous as the reduced matrix viscosity, due to the increased temperature of the matrix, results in better consolidation of the fibres around the projections and minimises the distortion of the fibres. The composite component is only heated locally where heating is required, which removes the need to heat the entire composite component.
1. A method of joining a part to a composite component, the composite component comprising fibres impregnated with a matrix material, and the part comprising a plurality of projections, the method comprising:
inserting the projections into the composite component; and
pre-heating the projections before they are inserted into the composite component, so that the projections are at a higher temperature than the composite component as they are inserted into the composite component, wherein the part further comprises a body, the projections extend from the body, and the projections are pre-heated by applying heat to the body so that the body conducts the heat to the projections, the method further comprising:
holding the body of the part with a fixture as the projections are inserted into the composite component;
and releasing the body of the part from the fixture after the projections have been inserted into the composite component.
2. The method of claim 1 wherein the pre-heating causes a temperature difference between the projections and the composite component which is greater than 20° C.
3. The method of claim 1 , wherein the fibres of the composite component are pushed apart by the projections as the projections are inserted into the composite component.
4. The method of claim 1 further comprising monitoring a temperature of the part, and controlling the pre-heating of the projections based on the monitored temperature of the part.
5. The method of claim 1 , the method further comprising heating the projections as the projections are inserted into the composite component.
6. The method of claim 1 further comprising monitoring an insertion force applied to the part as the projections are inserted into the composite component, and controlling the insertion force applied to the part based on the monitored insertion force.
7. The method of claim 1 further comprising curing the composite component after the projections have been inserted into the composite component, thereby adhering the part to the composite component.
8. The method of claim 1 wherein the projections are pre-heated by running an electrical current through an electrically-resistive heating element, and applying the heat to the body with the electrically-resistive heating element.
9. The method of claim 1 wherein the matrix material is a thermoplastic matrix material.
10. The method of claim 1 wherein the projections are metallic.
11. A device for joining a part to a composite component, wherein the composite component comprises fibres impregnated with a matrix material and the part comprises a body and a plurality of projections extending from the body, the device comprising: a fixture for holding the body of the part; an actuator configured to push the projections into the composite component by applying an insertion force to the part via the fixture; and a heating element configured to heat the body as it is held by the fixture.
12. A device for joining a part to a composite component, wherein the composite component comprises fibres impregnated with a matrix material and the part comprises a plurality of projections, the device comprising: a fixture for holding the part; an actuator configured to push the projections into the composite component by applying an insertion force to the part via the fixture; and a heating element configured to heat the part as it is held by the fixture, wherein the fixture comprises a socket configured to receive the part, and a vacuum channel which is in fluid communication with the socket.
13. The device of claim 11 wherein the heating element is housed within the fixture.
14. The device of claim 11 wherein the heating element is an electrically resistive heating element.
15. The device of claim 11 further comprising a load cell configured to measure the insertion force applied to the part by the actuator.
16. The device of claim 15 further comprising a thermally insulating gasket between the load cell and the fixture.
17. The device of claim 11 wherein the fixture is a metallic fixture, and the heating element is configured to heat the metallic fixture in order to heat the part via the metallic fixture.
18. The device of claim 11 wherein the fixture is configured to releasably hold the part.
19. The device of claim 11 wherein the fixture has a hole which houses the heating element.
20. The device of claim 11 wherein the actuator is a robotic arm.
21. The method of claim 1 wherein the projections are pre-heated by applying the heat to the body via the fixture.
22. The device of claim 11 wherein the heating element is configured to heat the projections by applying the heat to the body via the fixture.