Friction stir welding method and device, as well as workpiece comprising a butt weld seam

1 . A method for friction stir welding along a butt joint weld line, the method comprising:

providing a welding device comprising a probe assembly including a first probe body supported by a first shaft and a second probe body supported by a second shaft, wherein one of the first shaft and the second shaft is a hollow shaft and the other of the first shaft and the second shaft extends through the hollow shaft;

providing a first part and a second part to be joined along a butt joint weld line, wherein the first part and the second part are each a laminate comprising a first layer formed with a first material and a second layer formed with a second material, and the first material has different material properties than the second material;

arranging the first part and the second part such that a first edge of the first part is adjacent a second edge of the second part;

positioning both the first probe body and the second probe body to face a first edge of the butt joint weld line and face a first side of each of the first part and the second part;

advancing the first probe body and the second probe body in a common direction towards the first edge of the butt joint weld line and towards the first side of each of the first part and the second part;

positioning, by the advancement in the common direction, the first probe body between the first edge and the second edge, into alignment with the first layer of the first part and the first layer of the second part, at a first depth between the first edge and the second edge, and beyond an outer surface of at least one of the first part and the second part, wherein the outer surface faces the welding device;

positioning, by the advancement in the common direction, the second probe body between the first edge and the second edge, into alignment with the second layer of the first part and the second layer of the first part, and at a second depth different than the first depth; and

performing friction stir welding to join the first part and the second part using the welding device, including rotating the first probe body and the second probe body and moving the welding device along the adjacent edges of the first part and the second part such that simultaneously the first probe body acts on the first layers and the second probe body acts on the second layers.

2 . The method according to claim 1 , wherein first material of the first layer has a thermal conductivity different than the second material and/or the first layer is a metal layer and the second layer is a synthetic layer comprising a thermoplastic material.

3 . The method according to claim 1 , wherein the first part and the second part are each made from a fiber-metal laminate, wherein the first layer is a metal layer and the second layer is a synthetic layer formed with a thermoplastic matrix and reinforcing fibers embedded in the thermoplastic matrix.

4 . The method according to claim 1 , wherein each of the first probe and the second probe comprises a respective probe body configured to contact a respective one of first layer and the second layer during the friction stir welding, wherein an outer diameter of the probe body of the first probe differs from the outer diameter of the probe body of the second probe, and the method further comprises rotating the probe bodies of the first probe and the second probe body at a different rotational speeds during the friction stir welding.

5 . A method to form a workpiece component of an aircraft or spacecraft comprising:

providing a first part and a second part each formed of a fiber metal laminate including a metal layer and a synthetic layer with embedded rein-forcing fibers, wherein each of the first part and the second part have a respective outer surface;

aligning a first edge of the first part next to a second edge of the second part to form a butt joint to be welded, wherein the metal layers of the first part and the second part are aligned in a first plane and the synthetic layers of the first part and the second part are aligned in a second plane parallel to the first plane;

positioning both a first probe body supported by a first shaft and a second probe body supported by the second shaft to face a first edge of the butt joint and to face a first side of each of the first part and the second part, wherein one of the first shaft and the second shaft is a hollow shaft and the other of the first shaft and the second shaft extends through the hollow shaft;

advancing the first probe body and the second probe body in a common direction towards the first edge of the butt joint and towards the first side of each of the first part and the second part;

inserting a first probe body between and in alignment with the metal layers at the first plane, wherein the first probe body is inserted a first depth beyond the outer surface of at least one of the first part and the second part, wherein the first probe body advances along a common direction and towards a first edge of the butt joint;

inserting along the common direction and towards the first edge of the butt joint, a second probe body between and in alignment with the synthetic layers at the second plane, wherein the second probe body is inserted a second depth beyond the outer surface, the second depth is different than the first depth, and

friction stir welding the first edge to the second edge by actuating the first probe body to friction stir weld the metal layers and simultaneously actuating the second probe body to friction stir weld the synthetic layers,

diameter of the first probe body differs from an outer diameter of the second probe body.

6 . A method to form a workpiece component of an aircraft or spacecraft comprising:

providing a first part and a second part each formed of a fiber metal laminate including a metal layer and a synthetic layer with embedded rein-forcing fibers, wherein each of the first part and the second part have a respective outer surface;

aligning a first edge of the first part next to a second edge of the second part, wherein the metal layers of the first part and the second part are aligned in a first plane and the synthetic layers of the first part and the second part are aligned in a second plane parallel to the first plane;

inserting a first probe body between and in alignment with the metal layers at the first plane, wherein the first probe body is inserted a first depth beyond the outer surface of at least one of the first part and the second part;

inserting a second probe body between and in alignment with the synthetic layers at the second plane, wherein the second probe body is inserted a second depth beyond the outer surface, wherein the second depth is different than the first depth, and

friction stir welding the first edge to the second edge by actuating the first probe body to friction stir weld the metal layers and simultaneously actuating the second probe body to friction stir weld the synthetic layers;

wherein a first shaft supports the first probe body and a second shaft supports the second probe body, and one of the first shaft and the second shaft is a hollow shaft and the other of the first shaft and the second shaft extends through the hollow shaft, and

wherein the friction stir welding includes rotating the first shaft and the first probe body at a different rotational rate than the second shaft and the second probe body during the friction stir welding.

7 . The method of claim 5 , further comprising:

rotating first probe body during the friction stir welding, and

rotating the second probe body during the friction stir welding and at a rotational speed different than a rotational speed of the first probe body.

8 . The method of claim 5 , further comprising moving the first probe body and the second probe body along the first edge and the second edge during the friction stir welding.

9 . The method of claim 5 , wherein an outer diameter of the first probe body differs from an outer diameter of the second probe body.

10 . The method according to claim 1 ,

wherein the friction stir welding includes rotating the first shaft and the first probe body at a different rotational rate than the second shaft and the second probe body during the friction stir welding.