PURPOSE: To obtain the subject material, usable as exterior trim parts of mufflers for internal combustion engines, resistant to vibration and having water repellency by impregnating the whole layer or at least a surface layer part of a glass fiber layer with a silicone varnish.

CONSTITUTION: The objective material obtained by, etc., punching glass fibers according to the product shape, etc., impregnating the punched glass fibers with an activated silica binder solution, calcining the glass fibers and impregnating the whole or surface layer with a silicone varnish by spraying, dipping, etc., and naturally drying or calcining the impregnated material at about 150°C for about 15min.