Ultrasonic Plastic Welding of Carbon Fiber Reinforced Polyamide 6 to Aluminium and Steel

An experimental study has been performed to examine the application of displacement controlled Ultrasonic Plastic Welding (UPW) in the creation of joints between aluminium or steel and carbon fiber reinforced polyamide 6 (CFR-PA6). This is known as a fast welding technique in which in the order of seconds a joint can be created by means of fusion bonding of thermoplastics. This study has been focused on an assessment of the power and displacement feedback obtained during welding, the electro-insulating behavior of the created joints and their single lap shear strength & fracture. Both non-hybrid and hybrid joints have been welded. For hybrid welds, both steel and aluminium were used as metallic substrate. For aluminium substrates, the effect of not applying a coating has been evaluated as well. The absence of a coating was found to result in no bond between the applied thermoplastic and pretreated metallic surface. With the applied welding settings, hybrid welds with coated metallic substrates showed to dissipate the same amount of energy as non-hybrid welds, in the order of 700 Joules on average, at a welding time in the order of 0.5 seconds. The obtained power and displacement feedback during welding showed to be affected by both material choice and the type of adherend in contact with the sonotrode during welding. Welding resulted in an electro-insulating thermoplastic adhesive layer between both adherends for hybrid welds. Welding grit blasted and coated aluminium samples resulted in an average single lap shear strength (SLSS) of 11 MPa. This was 16.5 MPa with a coefficient of variation of 2.2 % for welding with a grit blasted, nitric acid etched and coated aluminium surface. This strength is up to 80 % of a tested adhesive reference. Hybrid welds with coated grit blasted steel and the used welding settings proved to result in an average SLSS of 8 MPa. For hybrid welded samples generally adhesive peel fracture on the metallic surface occurred. The findings support the application of displacement controlled ultrasonic plastic welding in the creation of hybrid joints between CFR-PA6 and thermoplastic coated metals like aluminium or steel.Structural Integrity & CompositesAerospace Structures & MaterialsAerospace Engineerin