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 (202, 402) arranged longitudinally relative to one another in a single layer, each strength rod (202, 402) being disposed adjacent to and spaced from at least one adjacent strength rod (202, 402); each strength rod (202, 402) including multiple unidirectional, substantially straight collimated structural fibers fixed in a solidified matrix resin so that each strength rod (202, 402) 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 (312, 313) to which the multiple strength rods (202, 402) are joined by an adhesive applied to at least one of the carrier layer (312, 313) and the strength rods (202, 402); wherein the carrier layer (312, 313) locates adjacent strength rods (202, 402) to permit the flow of liquid bonding resin between adjacent strength rods (202, 402); and, wherein the carrier layer (312, 313) 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 (312, 313), characterized in that the carrier layer (312, 313) 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 (202, 402). 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 (202, 402) arranged longitudinally relative to one another in a single layer, each strength rod (202, 402) being disposed adjacent to and spaced from at least one adjacent strength rod (202, 402); each strength rod (202, 402) including multiple unidirectional, substantially straight collimated structural fibers fixed in a solidified matrix resin so that each strength rod (202, 402) 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 (312, 313) to which the multiple strength rods (202, 402) are joined by an adhesive applied to at least one of the carrier layer (312, 313) and the strength rods (202, 402); wherein the carrier layer (312, 313) locates adjacent strength rods (202, 402) to permit the flow of liquid bonding resin between adjacent strength rods (202, 402); and, wherein the carrier layer (312, 313) 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 (312, 313), characterized in that the carrier layer (312, 313) 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 (202, 402).