In a method of using ultrasonic welding for fusion bonding of thermoplastic composites, an energy director is formed in place on a first thermoplastic substrate. The energy director can be protrusions arranged in a grid pattern over the entire weld region. The energy director can have protrusions of varying thicknesses to account for unevenness along the weld interface. Forming the energy director can be carried out by placing thermoplastic film on the first thermoplastic substrate, melting the thermoplastic film, and stamping the thermoplastic film with an energy director stamp. After the energy director is formed, the first thermoplastic substrate is ultrasonically welded to a second thermoplastic substrate with the energy director sandwiched between the first and second thermoplastic substrates.

The present invention relates to a processing element for processing a material, such as, e.g. a sonotrode or an anvil, having a substantially cylindrical or cylinder-segment-shaped carrier surface which is intended to come into contact with the material during processing, the processing element being provided to be rotated about its longitudinal axis during processing, so that the carrier surface moves in a circumferential direction and rolls on the material to be processed, wherein at least one structural element is arranged on the carrier surface, which structural element protrudes in a radial direction beyond the carrier surface, wherein the structural element has a top surface which is intended to come into contact with the material to be processed. In order to provide a processing element enabling reliable welding at a higher feed rate, it is proposed according to the invention that the top surface comprises a base section and at least one recess section having a smaller distance from the longitudinal axis than the base section, wherein in a sectional view perpendicularly to the longitudinal axis, the base section and the recess section are arranged next to one another.

An apparatus for welding together webs, the apparatus comprising first and second weld tools, wherein at least the first weld tool is rotatable about an axis of rotation and has a substantially cylindrical surface on which is located a welding contact portion, and wherein the welding contact portion extends at least partly circumferentially around the cylindrical surface and at least partly axially along the cylindrical surface.