Fibre-reinforced composite tubular shafts and manufacture thereof

A method of manufacturing an elongate tubular shaft comprised of a fibre-reinforced resin matrix composite material, the method comprising the steps of:

• a) providing an elongate mandrel, the mandrel having a longitudinal axis, opposite first and second ends which are mutually spaced along the longitudinal axis, and an outer circumferential surface that is non-cylindrical along at least a part of a length of the mandrel extending along the longitudinal axis;
• b) providing a preform layer comprising a fibrous reinforcement, the preform layer having first and second end portions, which are mutually spaced, and inner and outer edges, which are mutually spaced, the inner and outer edges extending from the first end portion towards the second end portion, wherein when the preform layer is in a planar configuration at least the inner edge is non-linear and a spacing between the inner and outer edges varies along a length of the preform layer extending between the first and second end portions;
• c) locating the first end portion of the preform layer adjacent to the first end of the mandrel in a starting configuration in which the inner edge is oriented towards the mandrel and the outer edge is oriented away from the mandrel;
• d) wrapping the preform layer about the mandrel so that the outer circumferential surface of the mandrel is progressively covered by the wrapped preform layer to form an elongate tube, whereby in the elongate tube the inner edge contacts the outer circumferential surface of the mandrel and the outer edge is located at an outer circumferential surface of the elongate tube, wherein during the wrapping step the mandrel and the preform layer are relatively rotated about an axis of rotation that is along the longitudinal axis of the mandrel and the preform layer is continuously fed, from the first end portion to the second end portion of the preform layer, onto the mandrel along a feeding path which is perpendicular to the longitudinal axis of the mandrel;
• and
• e) moulding the elongate tube on the mandrel to form an elongate tubular shaft comprised of a fibre-reinforced resin matrix composite material formed from the preform layer;
• wherein before or during step e) a resin material is provided in contact with the fibrous reinforcement of the preform layer, and during step e) the resin material forms a resin matrix which incorporates the fibrous reinforcement;
• wherein in step b) the inner edge of the preform layer is shaped and dimensioned so that in step d) the inner edge is continuously coincident with the outer circumferential surface of the mandrel and the elongate tube comprises a plurality of wrapped layers forming a spiral about the longitudinal axis, wherein each wrapped layer is parallel to the longitudinal axis.