all embodiments of the present invention utilize a uniform and substantially homogenous mixture of non - conductive fibers with conductive fibers . the non - conductive fibers may be formed of aramid resin , acrylic resin , or even mineral wool . the conductive fibers may be formed of steel , copper , or brass , or may be formed of carbon other than graphite . the conductive fibers have a small diameter , less than 0 . 05 inch ( 1 . 2 mm ), and should have an average length of less than one inch ( 25 mm ). the non - conductive fibers also have a small diameter , and should have an average length of less than 0 . 5 inch ( 12 . 5 mm ). the fiber length need not be uniform and may vary to a substantial extent . aramid and acrylic fibers are preferred for the non - conductive fibers . the term &# 34 ; brake pad &# 34 ;, as used herein , refers to and includes brake linings , brake blocks , brake shoes and other forms of molded friction elements for brakes . friction materials included in the final mixture may include granular phenolic resin , friction particles made from cashew nut oil , natural or synthetic rubber in granular form , mineral particles such as calcium carbonate , clay , fiberglass , wollastonite , barytes , magnesium oxide , mineral wool , and other ingredients selected by the brake pad manufacturer . the drawing illustrates one method of preparing a preliminary mixture and a final mixture of granular and fibrous materials for use in molding brake pads . a supply 10 of non - conductive fibers , preferably of aramid or acrylic resin , producing an output mass or strip 11 , is fed into a chopper - mixer apparatus 18 . by way of example , apparatus 18 may comprise a conventional hammer mill . the system shown in the drawing also includes a supply 14 of conductive fibers &# 39 ; supply 14 may comprise a conventional machine for manufacturing steel wool or other metal fiber wool . the output of the conductive fiber supply 14 is a continuous strip 15 of interleaved metal fibers of indeterminate length that is also fed into the chopper - mixer 18 . the directions of movement of the metal fiber strip 15 and the resin fiber supply 11 are indicated in the drawing by the arrows a and b , respectively . in the chopper - mixer 18 , the conductive metal fiber strip 15 is comminuted to produce a quantity of short conductive fibers of small diameter . these conductive fibers should have an average length no greater than about one inch ( 25 mm ); they may be , and usually are , appreciably shorter . the chopper - mixer 18 also comminutes the non - conductive fiber material 11 to produce a quantity of short non - conductive fibers of small diameter . like the conductive fibers , these non - conductive fibers have an average length no greater than about 0 . 5 inch ( 12 . 5 mm ). for the non - conductive fibers , a preferred average length is no more than about 0 . 15 inch ( 0 . 374 mm ). there is no requirement for uniformity of length . the two types of fiber are supplied to the chopper - mixer 18 in a predetermined ratio so that the preliminary mixture 31 constituting the output 19 from chopper - mixer 18 maintains the two kinds of fiber in that ratio . as shown in the drawing , the preliminary mixture 31 from the output 19 of chopper - mixer 18 may be supplied to one input of a mixing apparatus 42 by means of a conveyor 22 or other appropriate means . on the other hand , the preliminary mixture ( premix ) 31 may be packaged or stored for subsequent use in the manufacture of brake pads or other products . mixing apparatus 42 has two additional inputs to which granular friction materials for a brake pad are supplied from two different supplies 34 and 36 . the granular friction materials need not be of uniform size ; substantial variation is permissible . the arrangement illustrated in the drawing employs two different granular friction materials ; there may be additional granular friction material supplies , with outputs to mixer 42 . in the mixing apparatus 42 the friction ingredients are mixed with the preliminary mixture 31 from device 18 to form a moldable brake pad mixture 46 that is supplied by appropriate means , such as a conveyor 48 , to suitable brake pad molding apparatus . because the present invention is not concerned with the final molding process for the brake pads , no molding apparatus has been illustrated . in the illustrated process , mixing apparatus 42 can accept premix 31 and other ingredients in a single load or in a preselected sequence , with mixing time between sequences . the blend or premix 31 of conductive and non - conductive fibers can be added at any desired time appropriate for the final mix . indeed , the process steps performed by mixing apparatus 42 , friction ingredient supplies such as 34 and 36 , etc . may occur at a completely different location from the preliminary steps afforded by supplies 10 and 14 and the chopper - mixer 18 , or their equivalents . in the process shown specifically in the drawing , the strip 15 of intertwined conductive fibers of indeterminate length is chopped in the chopper - mixer 18 to produce the desired multiplicity of short conductive fibers having an average length no greater than about one inch ( 25 mm ), or preferably much shorter , schematically indicated at 31 . similarly , the mass 11 of intertwined non - conductive fibers 11 , which again may have indeterminate lengths , is chopped to produce a multiplicity of short non - conductive fibers having an average length no greater than about 0 . 5 inch ( 12 . 5 mm ) or shorter . accordingly , the output 31 from chopper - mixer 18 includes both conductive and non - conductive fibers in a uniform mixture , of predetermined ratio . this mixture does not hold a static charge and does not tend to cling to the inner walls of the mixing apparatus ; accordingly , in the mixing apparatus 42 the preliminary mixture can be readily and uniformly mixed with the granular ingredients from supplies such as 34 and 36 . as a consequence , the material 46 supplied to the brake pad molding apparatus does not tend to separate according to its components and is appropriate for molding of brake pads . it will be recognized that the drawing is a simplified illustration of a suitable process for preparing a brake pad molding mixture . to meet the requirements of brake pad manufacturers , the ratios of the conductive and non - conductive fibers and the other granular friction components requires control . this control can be afforded by conventional means , such as weighing or metering of the outputs from the granular friction material supplies 34 and 36 . of course , weighing or metering can be utilized for control of the rates of input to the chopper - mixer 18 from the fiber supplies 10 and 14 . because such control apparatus is susceptible of many forms and is well known in the art , no metering or other ratio controls have been shown in the drawing .