. . "Suitable fibers for the purpose of this invention must be non-combustible or thermally resistant fibers like glass fibers, particularly E-glass, and the like, metallized glass fibers, especially aluminized glass fibers, ceramic fibers, carbon fibers, graphite fibers, nickel-coated graphite fibers, and polyamide fibers, polybenzimide, polybenzoxazol, polybenzathiazol, and the like." . .