Abstract: A noise attenuation panel used to attenuate noise in aircraft engines includes a cellular core and a facing sheet formed with an array of holes. The holes are laser drilled to provide: (i) hole size variation over the facing sheet; (ii) non-circular hole cross section; (iii) polygonal hole cross section; (iv) hole locations not contiguous with walls of the cellular core; and (v) inclined holes passing through the facing sheet in a direction inclined to the normal to the facing sheet.

Abstract: A noise attenuation panel used to attenuate noise in aircraft engines includes a cellular core and a facing sheet formed with an array of holes. The holes are laser drilled to provide: (i) hole size variation over the facing sheet; (ii) non-circular hole cross section; (iii) polygonal hole cross section; (iv) hole locations not contiguous with walls of the cellular core; and (v) inclined holes passing through the facing sheet in a direction inclined to the normal to the facing sheet.

Abstract: In the manufacture of a noise attenuation panel for an aeroengine nacelle an adhesive film is applied to a front face of a cellular component of the panel. The adhesive film is caused to reticulate to the ends of the walls of the cells at the front face of the cellular component. A perforate facing component of the panel is bonded to the front face of the cellular component by adhesive flow from the cell walls to the facing component. To avoid unpredictable adhesive flow giving rise to cosmetic spots on the front face of the facing component the two components are brought together with the interposition of an adhesive flow control sheet and the reticulated adhesive caused to bond the two components together by adhesive flow under the control of the adhesive flow control sheet.

Abstract: A noise attenuation panel used to attenuate noise in aircraft engines includes a cellular core and a facing sheet formed with an array of holes. The holes are laser drilled to provide: (i) hole size variation over the facing sheet; (ii) non-circular hole cross section; (iii) polygonal hole cross section; (iv) hole locations not contiguous with walls of the cellular core; and (v) inclined holes passing through the facing sheet in a direction inclined to the normal to the facing sheet.

Abstract: In forming a multi-axial yarn structure a bias yarn assembly forming device makes use of cooperating yarn guide and yarn transfer members having yarn guide elements defining guide and transfer openings which hold warp yarns spaced apart in the weft direction. Warp yarn transfer from an opening in one member to an opening in the other member is facilitated by providing the guide elements of the two members with cooperating complementary salient and re-entrant inclined end portions. Furthermore, a yarn diverter blade extends from the end portion of each guide element of one of the members to hold the transferring yarns away from the junctions between the cooperating end portions of the guide elements. To facilitate insertion of binding warp yarns two sets of yarn guide and yarn transfer members are provided to hold the yarns spaced apart to form binding warp yarn insertion zones between the two sets.

Abstract: A method of producing a structural component (12) from a primary wall structure (14) which defines a plurality of juxtaposed primary cells (15) which extend between and which are open to the front face and the rear face of the component (12) and a secondary wall structure (16) within the primary wall structure (14) which divides each primary cell (15) into two or more subcells (151, 152) comprises first forming the primary wall structure (14) and then forming the secondary wall structure (16) within the primary wall structure (14) by bringing the primary wall structure (14) into a condition in which it lies within a body of liquid the surface of which provides or is provided with a photosensitive layer and in which the photosensitive layer is at a predetermined level in each primary cell (15) and exposing the photosensitive layer to a radiation source to bring the photosensitive layer to a consolidated state within the primary wall structure (14) to form the secondary wall structure (16).