A structural element for a wind turbine blade comprising: a preform layer (300A - 300H, 400, 400A - 400H) of a composite beam configured to extend along at least a portion of an airfoil of the wind turbine blade , the preform layer (300A - 300H, 400, 400A - 400H) including multiple elongate strength rods arranged longitudinally relative to one another in a single layer, each strength rod being disposed adjacent to and spaced from at least one adjacent strength rod ; each strength rod including multiple unidirectional, substantially straight collimated structural fibers fixed in a solidified matrix resin so that each strength rod is rigid and defines a finished geometry including a selected length and width and a selected profile; the preform layer (300A - 300H, 400, 400A - 400H) including at least one carrier layer to which the multiple strength rods are joined by an adhesive applied to at least one of the carrier layer and the strength rods ; wherein the carrier layer locates adjacent strength rods to permit the flow of liquid bonding resin between adjacent strength rods ; and, wherein the carrier layer of the preform layer (300A - 300H, 400, 400A - 400H) includes one or more permeable materials suitable to facilitate permeation and penetration to permit flow of liquid bonding resin through the carrier layer , characterized in that the carrier layer of the preform layer (300A - 300H, 400, 400A - 400H) comprises at least one of a nonwoven material and a woven material having one or more of substantially unidirectional: multiple fibers, multiple yarns and multiple rovings disposed at a substantially transverse orientation relative to the longitudinal axis of the strength rods . a preform layer (300A - 300H, 400, 400A - 400H) of a composite beam configured to extend along at least a portion of an airfoil of the wind turbine blade , the preform layer (300A - 300H, 400, 400A - 400H) including multiple elongate strength rods arranged longitudinally relative to one another in a single layer, each strength rod being disposed adjacent to and spaced from at least one adjacent strength rod ; each strength rod including multiple unidirectional, substantially straight collimated structural fibers fixed in a solidified matrix resin so that each strength rod is rigid and defines a finished geometry including a selected length and width and a selected profile; the preform layer (300A - 300H, 400, 400A - 400H) including at least one carrier layer to which the multiple strength rods are joined by an adhesive applied to at least one of the carrier layer and the strength rods ; wherein the carrier layer locates adjacent strength rods to permit the flow of liquid bonding resin between adjacent strength rods ; and, wherein the carrier layer of the preform layer (300A - 300H, 400, 400A - 400H) includes one or more permeable materials suitable to facilitate permeation and penetration to permit flow of liquid bonding resin through the carrier layer , characterized in that the carrier layer of the preform layer (300A - 300H, 400, 400A - 400H) comprises at least one of a nonwoven material and a woven material having one or more of substantially unidirectional: multiple fibers, multiple yarns and multiple rovings disposed at a substantially transverse orientation relative to the longitudinal axis of the strength rods . <EOS>