Profile of interfacing projections

1. A method of joining a first component to a second component, the method comprising:

preparing the first component by forming an array of projections extending from a bond surface of the first component, each projection having a base, a tapered tip and a tapered overhang beneath the tip, wherein a portion of the bond surface beneath each projection is a local bond surface for that projection, wherein the overhang has an undercut surface which is inclined and faces towards the local bond surface;

bringing the components together so as to embed the projections in the second component; and

hardening the second component after the array of projections has been embedded into it.

2. A method according to claim 1 , wherein the base of each projection tapers towards the overhang.

3. A method according to claim 1 , wherein each projection has either a linear centreline, or a curved centreline.

4. A method according to claim 3 , wherein the centreline of each projection is either perpendicular to the bond surface at its intersection with the bond surface, or forms an oblique angle with the bond surface at its intersection with the bond surface.

5. A method according to claim 3 , wherein each projection is rotationally symmetric about its centreline.

6. A method according to claim 1 , wherein each projection has a frustoconical base, a conical tip, and an inverted frustoconical overhang between the base and the tip.

7. A method according to claim 1 , wherein the projections are grown on the bond surface in a series of layers, each layer being grown by directing energy and/or material to the bond surface.

8. A method according to claim 7 , wherein each layer is grown by an additive fabrication process.