Apparatus with a thermoplastic tube to tube-sheet joint and associated friction stir based fabrication method

A method of fabricating a thermoplastic tube-to-tube-sheet joint, the method comprising:

• providing at least one thermoplastic tube-sheet having a first aperture extending therethrough and a plurality of mounting holes;
• securing the at least one thermoplastic tube-sheet to a welding fixture using a plurality of bolts inserted through the mounting holes, the welding fixture having a second aperture aligned with the first aperture such that the first aperture is positioned above the second aperture;
• inserting a thermoplastic tubular member through the first aperture and into the second aperture such that a radial clearance gap of at least 0.5 mm is maintained between an outer surface of the tubular member and an inner surface of the first aperture;
• performing a friction stir welding (FSW) process at the interface between the thermoplastic tubular member and the tube-sheet such that:
• frictional heat generated during the FSW process produces in situ molten thermoplastic workpiece material from the tube-sheet and/or the tubular member;
• and
• the molten thermoplastic workpiece material flows into and fills the radial clearance gap;
• forming a sealed joint between the tubular member and the tube-sheet without the use of any external consumable filler material.