Glass cloth with thin reinforced joints

Claim 1

In a continuous glass cloth for use in the formation of pre-pregs by impregnating said continuous glass cloth with a thermosetting resin varnish and heating the soimpregnated continuous glass cloth to dry the varnish comprising a plurality of glass cloth pieces of predetermined thickness, having edges and end portions associated with and adjacent respective edges, which are joined together, the improvement comprising: joints connecting adjacent glass cloth pieces together at respective adjacent edges thereof, each said joint having a total thickness less than about 1.5 times the thickness of said glass cloth, said joints comprising: end portions of respective adjacent glass cloth pieces, said end portions being disposed in a subtantially coplanar relationship with one another and having respective associated edges thereof in substantially abutting relationship with each other; at least one joining member overlapping said end portions of said adjacent glass cloth pieces, said joining member inert to and insoluble in said thermosetting resin varnish during pre-preg formation and being capable of withstanding the drying temperature of said varnish without substantial loss of bending, tensile and impact strength; and a thermoplastic resin located between said at least one joining member and said end portions of said adjacent glass cloth pieces, said thermoplastic resin bonding said at least one joining member to said end portions, said thermoplastic resin being inert to and insoluble in said thermosetting resin varnish during pre-preg formation and capable of withstanding the drying temperature of said varnish without substantial loss of bonding strength.