Method for connecting a surface-structured workpiece and a plastic workpiece

A method for connecting a surface-structured workpiece and a plastic workpiece using a joining tool including a sonotrode, said surface-structured workpiece comprising a structured contact surface section, said structured contact surface section comprising pin-like elements extending away from the structured contact surface section, said method comprising:

• positioning the surface-structured workpiece and the plastic workpiece on an anvil such that the structured contact surface section faces a contact surface of the plastic workpiece,
• positioning the joining tool on the surface-structured workpiece so as to bring the sonotrode into contact with an outer surface of the surface-structured workpiece, the outer surface being opposite to the structured contact surface section,
• applying a pressure to the sonotrode and/or the anvil perpendicular to the contact surface to hold the workpieces fixed between the anvil and the sonotrode and applying ultrasonic vibrations to the workpieces by the sonotrode for a predetermined period of time, so that softening of the plastic workpiece is induced and the pin-like elements penetrate into the plastic workpiece;
• and
• removing the pressure and ultrasonic vibrations and retracting of the sonotrode;
• wherein the pin-like elements have a length of 1 to 5 mm in direction perpendicular to the contact surface section;
• wherein the pin-like elements comprise anchoring elements at their distal ends, wherein the anchoring elements of the pin-like elements are designed as conical or spherical or convex or arrow-like or hook-like heads;
• wherein the structured contact surface section comprises between 3 to 10 pin-like elements per cm2;
• and
• wherein the surface-structured workpiece is formed of a material selected from the group consisting of:
• aluminum, aluminum alloy, magnesium, magnesium alloy, titanium and titanium alloy.