Abstract: A method of making a wind turbine component of composite construction with enhanced radar absorbing properties is described. The method comprises making the component and then modifying the component by applying circuit analog elements to a surface of the component.

Abstract: A flexible core for a composite structure is described. The core includes a first core layer, a second core layer, and a ground plane between the first and second core layers. A plurality of slits is provided in the core, and each slit extends through one of the first of second core layers and through the ground plane. The core may be the core of a sandwich panel, for example a sandwich panel of the type used in the composite construction of wind turbine blades.

Abstract: A wind turbine component incorporating radar-absorbing material having increased compatibility with lightning protection systems is described. The radar absorbing material includes a ground plane having an electrical conductivity and/or a dielectric constant that is higher in the presence of an electric field having a frequency of 1 GHz and above than in the presence of an electric field having a frequency of 10 MHz and below. Suitable materials for the ground plane include ferroelectric and ferrimagnetic materials and percolating material combinations, all of which have frequency-dependent properties that can be tuned to make the ground plane highly reflective at radar frequencies and benign at lightning discharge frequencies.

Abstract: A split core for a composite structure is described. The split core includes a first core layer, a second core layer, and a functional interlayer disposed between the first and second core layers. The first core layer separates the functional interlayer from a functional layer of the composite structure and/or from an outer surface of the composite structure. The thickness of the first core layer is substantially uniform across the composite structure and the distance between the functional interlayer and the functional layer and/or the outer surface of the composite structure is substantially constant across the composite structure.

Abstract: A wind turbine composite structure for absorbing radio frequency energy, the wind turbine composite structure comprising: a sandwich panel construction comprising a core having an inner surface and an outer surface, disposed between an inner skin and an outer skin; the outer surface and the outer skin facing towards an exterior surface of the wind turbine composite structure and the inner surface and the inner skin facing towards an interior of the wind turbine composite structure; a reflector layer disposed adjacent to the inner skin; and a functional layer comprising printed or deposited circuitry, the functional layer forming a radar absorbing circuit in combination with the reflector layer, wherein the functional layer is printed or deposited directly on to the outer surface of the core.

Abstract: A core for a composite structure is described. The core has first and second core layers, and an interlayer region between the first and second core layers. At least one of the first and second core layers has hinge portions that facilitate draping of the core without interrupting the interlayer region. The interlayer region may include functionality such as a radar reflecting layer and/or optical fibres. Alternatively, the core may be a bonded core in which the interlayer region includes an adhesive layer for bonding the first and second core layers together.

Abstract: A wind turbine component incorporating radar-absorbing material having increased compatibility with lightning protection systems is described. The radar absorbing material includes a ground plane having an electrical conductivity and/or a dielectric constant that is higher in the presence of an electric field having a frequency of 1 GHz and above than in the presence of an electric field having a frequency of 10 MHz and below. Suitable materials for the ground plane include ferroelectric and ferrimagnetic materials and percolating material combinations, all of which have frequency-dependent properties that can be tuned to make the ground plane highly reflective at radar frequencies and benign at lightning discharge frequencies.

Abstract: A flexible core (60) for a composite structure is described. The core includes a first core layer (62), a second core layer (64), and a ground plane (66) between the first and second core layers. A plurality of slits (72) is provided in the core, and each slit extends through one of the first of second core layers and through the ground plane. The core may be the core of a sandwich panel, for example a sandwich panel of the type used in the composite construction of wind turbine blades (10).

Abstract: A foam core for a composite structure is described. The core includes a first core layer (62) and a second core layer (64). The first core layer (62) is a dielectric foam material and the second core layer (64) is a radar reflecting ground plane comprising an electrically conductive foam material.

Abstract: A method of making a wind turbine component of composite construction with enhanced radar absorbing properties is described. The method comprises making the component and then modifying the component by applying circuit analogue elements to a surface of the component.

Abstract: A wind turbine having a tower and at least one radar-absorbing panel attached to an outer surface of the tower is described. The panels are attached by mounts that do not penetrate the outer surface of the tower. In preferred embodiments of the invention, the mounts attach magnetically to the outer surface of the tower.

Abstract: A wind turbine composite structure for absorbing radio frequency energy, the wind turbine composite structure comprising: a sandwich panel construction comprising a core having an inner surface and an outer surface, disposed between an inner skin and an outer skin; the outer surface and the outer skin facing towards an exterior surface of the wind turbine composite structure and the inner surface and the inner skin facing towards an interior of the wind turbine composite structure; a reflector layer disposed adjacent to the inner skin; and a functional layer comprising printed or deposited circuitry, the functional layer forming a radar absorbing circuit in combination with the reflector layer, wherein the functional layer is printed or deposited directly on to the outer surface of the core.

Abstract: A split core for a composite structure is described. The split core includes a first core layer, a second core layer, and a functional interlayer disposed between the first and second core layers. The first core layer separates the functional interlayer from a functional layer of the composite structure and/or from an outer surface of the composite structure. The thickness of the first core layer is substantially uniform across the composite structure and the distance between the functional interlayer and the functional layer and/or the outer surface of the composite structure is substantially constant across the composite structure.

Abstract: A core for a composite structure is described. The core has first and second core layers, and an interlayer region between the first and second core layers. At least one of the first and second core layers has hinge portions that facilitate draping of the core without interrupting the interlayer region. The interlayer region may include functionality such as a radar reflecting layer and/or optical fibres. Alternatively, the core may be a bonded core in which the interlayer region includes an adhesive layer for bonding the first and second core layers together.

Abstract: Incorporation of functional cloth into prepreg composites A combined prepreg material (10) for use in composite lay-up techniques is described. The material (10) comprises first and second layers (12, 18) impregnated with a matrix material such as a resin. The first layer (12) is a functional layer and the second layer (18) is a keying layer. The keying layer (18) comprises a keying medium to facilitate bonding of the combined prepreg material (10) to a gel coat. The functional layer (12) comprises a woven cloth (14). A circuit is provided on a first surface (16) of the cloth (14).