Method for manufacture of a fiber reinforced rebar

Abstract

A composite reinforcing bar is formed by providing a reinforcing material supply of fiber strands rovings; a resin supply bath, and a puller for pulling the resin-impregnated reinforcing material through the resin bath. The reinforcing fibers include a series of inner rovings longitudinal to the bar with a first and a second helical wrappings of at least one roving wrapped around the inner rovings in opposed directions of wrapping. The resin is permeated through both the inner rovings and through the wrapped rovings to the outer surface where the inner rovings having parts thereof between the first and second wrapped rovings exposed and bulged outwardly by tension applied by the wrappings during curing with the bulged parts defining components of the outer surface portion of the bar which are thus rough and exposed for engaging a material to be reinforced so as to transfer longitudinal loads between the material to be reinforced and the inner rovings.

1 . A method of forming a reinforcing bar comprising:
 providing a series of inner rovings of reinforcing fibers arranged longitudinal to the bar;   wrapping a first helical wrapping or wrappings of at least one roving around the inner rovings in a first direction of wrapping;   wrapping a second helical wrapping or wrappings of at least one roving around the inner ravings in a second opposed direction of wrapping;   permeating a thermosetting resin through both the inner rovings and through the wrappings to form a structure integrated by the permeated resin;   the bar having an outer surface portion which extends along at least most of the length of the bar;   at the outer surface portion, the inner rovings having parts thereof between the first and second wrapping or wrappings exposed;   causing the exposed parts to bulge outwardly between the first and second wrapping or wrappings by tension applied by the wrapping or wrappings;   and curing the thermosetting resin through the inner and wrapped rovings while the inner and wrapped rovings are free from external pressure from a die such that the shape of the outer surface is defined solely by the shape of the inner and wrapped rovings as the resin is cured;   the bulged parts defining components of the outer surface portion of the bar which are thus rough and exposed for engaging a material to be reinforced so as to transfer longitudinal loads between the material to be reinforced and the inner rovings.   
     
     
         2 . The method according to  claim 1  wherein the resin is exposed on the outside surfaces of the inner ravings and the wrapped ravings. 
     
     
         3 . The method according to  claim 2  wherein the outside surface portion is free from bonded exterior roughening elements attached onto the outside surface of the resin. 
     
     
         4 . The method according to  claim 1  wherein the bar includes at least one additional outer surface portion where the resin and the inner rovings and the wrapped rovings are compressed to form a polygonal cross section for engaging a correspondingly shaped chuck by which the bar can be rotated about a longitudinal axis of the bar.