Friction stir welding of polymeric materials

A method for welding thermoplastic material comprising;

• rotating an element and directing the rotating element into a thermoplastic material and advancing the rotating element along a path in thermoplastic material where a weld is to be formed, the element having a geometry, and rotated at a speed and advanced at a rate relative to the thermoplastic material where the rotation of the element against the thermoplastic material introduces frictional energy into thermoplastic material in a weld forming region,
• introducing thermal energy into at least a portion of the weld forming region where the frictional energy and the thermal energy are sufficient to heat the thermoplastic material to a temperature to fuse the thermoplastic material in the weld forming region,
• constraining the thermoplastic material in the weld forming region with a constraining surface directed along the path that has a motion independent of rotating motion of the rotating element, such that the independent motion and construction of the constraining surface inhibit expulsion of heated thermoplastic material from the weld forming region resulting from the rotation and advancement of the element, inhibit lateral forces induced in the rotating element from the constraining surface, assist in consolidation thermoplastic material that is heated and fused.

An apparatus of welding thermoplastic material which comprises;

• a rotating element with apparatus for advancing the rotating element into a thermoplastic material and directing the rotating element along an path in thermoplastic material where a welded joint is to be formed to introduce frictional energy into a weld forming region in the thermoplastic material by rotation of the element against the thermoplastic material sufficient to heat the thermoplastic material in the weld forming region to a temperature to fuse the thermoplastic material, the rotating element having a geometry that contributes to the frictional energy introduced into the weld,
• constraining surface constructed to be directed along the path that has construction for a motion independent of rotating motion of the rotating element, such that the independent motion and the construction of the constraining surface inhibit expulsion of heated thermoplastic material from the weld forming region resulting from the rotation and advancement of the element, inhibit lateral forces induced in the rotating element from the constraining surface, assist in consolidation thermoplastic material that is heated and fused.

An apparatus of welding thermoplastic material which comprises;

• a rotating element with apparatus for advancing the rotating element into a thermoplastic material and directing the rotating element along an path in thermoplastic material where a welded joint is to be formed to introduce frictional energy into a weld forming region in the thermoplastic material by rotation of the element against the thermoplastic material, the rotating element having a geometry that contributes to the frictional energy introduced into the weld,
• an energy source for introducing thermal energy into at least a portion of the weld forming region in addition to the frictional energy, the frictional energy and the thermal energy sufficient to heat the thermoplastic material in the weld forming region to a temperature to fuse the thermoplastic material,
• constraining surface constructed to be directed along the path that has construction for a motion independent of rotating motion of the rotating element, such that the independent motion and the construction of the constraining surface inhibit expulsion of heated thermoplastic material from the weld forming region resulting from the rotation and advancement of the element, inhibit lateral forces induced in the rotating element from the constraining surface, assist in consolidation thermoplastic material that is heated and fused.