Abstract: A flat composite material based on a flat porous rigid material and one or more elongate elements of a fiber reinforced plastic material for stiffening the basis material, wherein the thickness of the elongate elements is smaller than that of the flat porous rigid material.

Abstract: A torsional vibration damper has a drive side transmission element connected to a drive; a takeoff side transmission element, which can be brought into working connection with a takeoff and which can rotate with respect to the drive side transmission element; and a damping device installed between the two transmission elements, the damping device being equipped with a spring system, which serves to transmit torque between the drive side and the takeoff side transmission element and has at least one reservoir space containing a gaseous medium. Each reservoir space of the spring system is in working connection with an assigned pressure space of a pressure circuit containing a fluid medium, where the pressure circuit can be used to adjust the pressure present in the pressure space when the torque to be transmitted by the spring system changes and thus to adapt the characteristic of the spring system to the new torque as needed.