Abstract: A platen roll core has a plurality of roll elements, and spacers interposed between adjacent roll elements of attenuation of propagated vibrations. The core, seen in terms of vibrating system, is equivalent to the sum of vibrating systems independent of one another and corresponding to the respective roll elements. The axial length of each roll element is set to such a value that the natural frequency thereof in an axial flexural oscillation mode is greater than a frequency of vibration applied from a vibration source, to thereby avoid the resonance of the core in the axial flexural oscillation made with the vibration source, such resonance being a main cause of an increase in noise level.

Abstract: A light metallic composite material containing therein fine granular additives dispersed in a matrix of a light metallic material, which composite material has a light weight, high mechanical strength, and excellent characteristics such as high damping ability. The additives each have a density less than that of the matrix and heat resistance enough to withstand a heating temperature at which they are composited with the matrix. Preferably, the additives are each formed with a coating which increases mechanical strength and provides an electromagnetic characteristic different from that of the matrix. Preferably, the composite material is produced by heating a mixture of matrix powders and additives up to a temperature where only part of the mixture including no microspheres is softened but the mixture is adequately composited, an amount of additives being equal to 10% to 70% by volume of the matrix, and by forming the composited mixture into a desired shape and solidifying same.

Abstract: A filler material, having a light weight, an increased mechanical strength, and various excellent characteristics such as damping ability, as well as a composite material and a structural material thereof are provided. The filler material comprises mats made of alumina fibers, and layers of hollow silica-alumina-microspheres which are dispersed of and affixed to the associated mat, with the mats and the layers alternately stacked with each other. The composite material comprises a matrix of aluminum in which the above-mentioned filler material is filled. The structural material, which contains therein a predetermined amount of microspheres enough to provide the material with a desired vibration amplitude-frequency characteristic, is applied to a head arm for supporting a magnetic head of a disk device, for instance.