A form-fill-seal machine 100 has a pull-down belt mechanism 23, a vertical sealing mechanism 2, and a controller 29. The pull-down belt mechanism conveys a cylindrical film Fm. The vertical sealing mechanism applies pressure and ultrasonic oscillation to the cylindrical film which is conveyed by the pull-down belt mechanism, and seals the cylindrical film. The controller controls the pull-down belt mechanism, and the pressure and the amplitude of the ultrasonic oscillation applied to the cylindrical film by the vertical sealing mechanism. The controller applies pressure and ultrasonic oscillation to the cylindrical film immediately before reaching a first point in time when the cylindrical film begins to be conveyed. The controller changes at least one of the pressure and the amplitude of the ultrasonic oscillation applied to the film according to the speed of the film in a time period after reaching the first point in time.

The invention provides a sonotrode (100) for welding a material, the sonotrode (100) comprising a welding section (110) configured for contacting the material, wherein the welding section (110) defines a rounded shape (111) in a cross-section parallel to a longitudinal axis (A) of the sonotrode (100), wherein the rounded shape (111) approximates a circular sector (20), wherein the circular sector (20) has a central angle .sub.c selected from the range of 25-300, and wherein the circular sector (20) has a central radius r.sub.c selected from the range of 5-30 mm, and wherein the sonotrode (100) has a width W perpendicular to the longitudinal axis (A) [and to the cross-section], wherein W is selected from the range of 10-100 mm.

A method for manufacturing a thermally protected polymer composite structure using a thermal barrier layer, the thermal barrier layer being porous and including a tool-side surface and a non-tool-side surface opposed from the tool-side surface, the method including co-bonding an adhesive onto the non-tool-side surface of the thermal barrier layer to yield a coated thermal barrier layer comprising a coated surface, and co-bonding a polymer matrix composite material onto the coated surface of the coated thermal barrier layer.