A method of producing a fibre reinforced profile by using a pultrusion assembly, said method comprising the steps of: i) introducing a reinforcing structure and liquid matrix materials into said pultrusion assembly, said reinforcing structure comprising a first layer of reinforcing fibres and a second layer of reinforcing fibres, said first layer of reinforcing fibres and said second layer of reinforcing fibres being arranged opposite each other and defining an enclosed space between themselves within said pultrusion assembly, ii) impregnating said first layer of reinforcing fibres by introducing a first amount of a first liquid matrix material into said pultrusion assembly, impregnating said second layer of reinforcing fibres by introducing a second amount of a second liquid matrix material into said pultrusion assembly, introducing a third amount of a third liquid matrix material into said pultrusion assembly and expanding said third amount of said liquid matrix material within said enclosed space between said first layer of reinforcing fibres and said second layer of reinforcing fibres, said first, second and third liquid matrix materials being compatible and of identical composition, whereby said first liquid matrix material is defined as the portion of said liquid matrix material which enters and remains inside said first layer, said second liquid matrix material is defined as the portion of said liquid matrix material which enters and remains inside said second layer and said third liquid matrix material is defined as the portion of the liquid matrix material which enters and remains inside said enclosed space, and iii) curing said first amount of said first liquid matrix material in a substantially non-expanded state within said first layer of reinforcing fibres, curing said second amount of said second liquid matrix material in a substantially non-expanded state within said second layer of reinforcing fibres, and curing said third amount of said third liquid matrix material in an expanded state within said enclosed space between said first layer and said second layer of reinforcing fibres, wherein said method further comprising the step of introducing a mandrel partially between said first layer and said second layer of reinforcing fibres and adjacent said enclosed space, characterized in that said first, second and third amount of liquid matrix material is introduced into said first layer of reinforcing fibres and/or said second layer of reinforcing fibres in a direction towards said mandrel, said third amount of liquid matrix material entering said enclosed space via said first layer of reinforcing fibres and/or said second layer of reinforcing fibres. i) introducing a reinforcing structure and liquid matrix materials into said pultrusion assembly, said reinforcing structure comprising a first layer of reinforcing fibres and a second layer of reinforcing fibres, said first layer of reinforcing fibres and said second layer of reinforcing fibres being arranged opposite each other and defining an enclosed space between themselves within said pultrusion assembly, ii) impregnating said first layer of reinforcing fibres by introducing a first amount of a first liquid matrix material into said pultrusion assembly, impregnating said second layer of reinforcing fibres by introducing a second amount of a second liquid matrix material into said pultrusion assembly, introducing a third amount of a third liquid matrix material into said pultrusion assembly and expanding said third amount of said liquid matrix material within said enclosed space between said first layer of reinforcing fibres and said second layer of reinforcing fibres, said first, second and third liquid matrix materials being compatible and of identical composition, whereby said first liquid matrix material is defined as the portion of said liquid matrix material which enters and remains inside said first layer, said second liquid matrix material is defined as the portion of said liquid matrix material which enters and remains inside said second layer and said third liquid matrix material is defined as the portion of the liquid matrix material which enters and remains inside said enclosed space, and iii) curing said first amount of said first liquid matrix material in a substantially non-expanded state within said first layer of reinforcing fibres, curing said second amount of said second liquid matrix material in a substantially non-expanded state within said second layer of reinforcing fibres, and curing said third amount of said third liquid matrix material in an expanded state within said enclosed space between said first layer and said second layer of reinforcing fibres, wherein said method further comprising the step of introducing a mandrel partially between said first layer and said second layer of reinforcing fibres and adjacent said enclosed space, characterized in that said first, second and third amount of liquid matrix material is introduced into said first layer of reinforcing fibres and/or said second layer of reinforcing fibres in a direction towards said mandrel, said third amount of liquid matrix material entering said enclosed space via said first layer of reinforcing fibres and/or said second layer of reinforcing fibres.