A METHOD OF CONSTRUCTING SKIN FOR A MEMBER OF A BODY SUCH AS AN AIRCRAFT

Abstract: The method of constructing a skin for a member (30) of a body such as an aircraft comprises providing from a multi-axial fabric first and second pieces (A, A1) shaped to correspond respectively to the shape of the member (30) to be covered by the skin and to the shape of a similar member (32) on the opposite side of the body, and inverting one of the pieces and placing it on the other. The method may include providing third and fourth pieces (B, B1) from multi-axial fabric shaped to correspond respectively to the shape of the member (30) to be covered by the skin and to the shape of the similar member (32) on the opposite side of the body and inverting one of the third and fourth pieces (B, B1) and placing it on the other to form a skin for the similar member. In order to minimise wastage the method preferably includes forming the first piece (A) and third piece (B) from areas of the fabric which lie alongside each other and/or forming the second piece (A1) and the fourth (B1) piece from areas of the fabric which lie alongside each other.

Description: A METHOD OF CONSTRUCTING SKIN FOR A MEMBER OF A BODY SUCH AS AN AIRCRAFT The invention relates to a method of constructing a skin for a member of a body, for example the skin of an aircraft wing. It is known to produce wing skins from composite laminae. Such laminae are produced by a process known in the art as "laying up" using, for example, carbon fibre tape. The tape is laid up in a multi-axial manner by a tape laying machine which provides a high degree of accuracy. The term "Multi-axial" means that alternate layers of tape will be laid by the machine in several different directions to produce a skin fabric having optimum strength in required directions. Commonly used directions for wing skin manufacture are 0° (spanwise for the wing) ±45°, -45° and 90° (substantially chordwise). In order for the skin to exhibit the correct characteristics when in position on, say, the completed wing, it is desirable that the laminae forming the skins be balanced. For example taking the case of a multi-axial skin having eight layers or plies a balanced lay-up from face to face could be as follows: +45° .45 0 . 90°. 0°. 0°. 90°. -45°. +45° The laying up process is slow and a object of the present invention is to enable a balanced laminae arrangement to be constructed more quickly and easily than known hitherto. According to a first aspect of the invention there is provided a method of constructing a skin for a member of a body such as an aircraft, the method comprising providing from a multi-axial fabric first and second pieces shaped to correspond respectively to shape of the member to be covered by the skin and to that of a similar member on the opposite side of the body, and inverting one of the pieces and placing it against the other to provide the skin. By using the method in accordance with the invention, the placing of one of the pieces against the other produces the balanced laminae arrangement as described above. Also, a skin substantially double the thickness of each of the separate pieces can be made without having to produce the skin by a single laying up process, thus reducing production time. The method may include, forming third and fourth pieces from multi axial fabric shaped to correspond respectively to the shape of the member to be covered by the skin and to the shape of the similar member on the opposite side of the body and inverting one of the third and fourth pieces and placing it on the other to form a skin for the similar member. The method may further include forming the pieces from areas of the fabric which lie alongside each other. In that way. fabric wastage is minimised. The areas of the fabric are preferably elongate and preferably extend substantially in a common longitudinal direction. In such a case, the method may include forming the multi-axial fabric with a layer of 0° fibres extending in the longitudinal direction of said areas thereof. Preferably, the method includes forming the multi-axial fabric by joining together edges of a plurality a fabrics made by a laying up process. In such a case, the method may include producing at least one of the first and second pieces in such a way that said piece is formed partly from one of said plurality of fabrics and partly from the other joined thereto. The joint between the two fabrics preferably runs in the one of the axial directions of the multi-axial fabric, for example in the 0° direction. In a preferred embodiment, the member is an aerofoil such as a wing on the body and the method include shaping the first and second pieces to correspond respectively to the plan view shape of the aerofoil and to that of a similar aerofoil on the opposite side of the body, inverting one of the pieces and placing it against the other to provide a skin for one of the aerofoils. According to a second aspect of the invention there is provided a skin for a member of a body such as an aircraft, the skin being constructed in accordance with the method of the first aspect of the invention or any of the consistory clauses relating thereto. According to a third aspect of the invention there is provided an aircraft aerofoil having a skin made in accordance with the method of the first aspect of the invention or any of the consistory clauses relating thereto. A method in accordance with the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a plan view of a multi-axial fabric having thereon wing-skin patterns for wings on both sides of an aircraft and shown partly broken away; Figure 2 is a perspective view partly broken away showing the way in which two pieces cut from the fabric have been inverted and placed on each other to form a wing-skin; Figure 3 shows to a larger scale a cross-section through a wing-skin shown in Figure 2 on the line III III in Figure 2; and Figure 4 is a diagrammatic front view of an aircraft having wing skins made by the method of the present invention. Looking at Figure 1 , two lengths 10, 12 of multi-axial fabric are provided. Each length of fabric has a 0° layer 14. a -45° layer 16 and a +45° layer 18. Such a fabric is also disclosed in our UK Patent Application No. 9817777.7 filed 15 August 1998 and in our co-pending International Patent Application No. PCT/GB99/ (Ref. MA/BO 14PCT) claiming priority therefrom, entitled "Composite Material Construction" and filed simultaneously with this application. The two lengths of fabric 10,12 are joined together along a joint line 20. Again, the joint line is disclosed in the aforesaid co-pending application and the reader is directed to the specification thereof for full details of the joint. The joint will not be described in detail in the present application. The two lengths of material 10,12 are joined together so that their 0° layers 14 form the upper surface of the fabric as viewed in Figure 1, and the +45° layers form the lower surface of the fabric. An elongate wing-skin pattern is applied to the joined fabrics 10,12 so as to form four discrete areas B, Bl and A, Al . The areas A, Al are substantially mirror images of each other and the areas B, B l are likewise substantially mirror images of each other. The patterns A, Al correspond substantially to wing skin plan view shapes for right and left hand wings 30, 32 respectively and the patterns B, B l similarly correspond to wing skin plan view shapes for the respective left and right hand wings. The areas are then cut out to produce four pieces. In the embodiment illustrated it will be noted that the joint line 20 runs through each piece. The 0° layer runs longitudinally of the four areas preferably parallel with the joint line 20. The cut out piece A corresponding to the shape of the right hand wing 30 can be inverted about its inner edge 22 and laid on cut out piece cut out piece Al corresponding to the shape of the left hand wing 32 or can be inverted about its leading edge 24 and placed on B 1. Similarly, the cut out piece B corresponding to the shape of the right hand wing 30 can be inverted about its outer edge 26 and placed on the cut out piece B 1 corresponding to the shape of the left hand wing or can be inverted about its leading edge 28 and placed on Al . The latter arrangement is shown in Figure 2. By following the inversion process the wing-skin cross-section will take the form shown in Figure 3 showing a balanced arrangement of laminae as follows: laminae 18 16 14 14 16 18 axes +45° -45° 0° 0° -45° +45° Several fabric cross-sections as shown in Figure 3 can be produced and laid one upon the other to form an even thicker wing-skin and. if desired, the wing skin can be gradually tapered from the wing root end towards the wing tip end by reducing the numbers of laminae towards the wing tip. Where tape is used to produce the fabric, it is normally pre-impregnated with epoxy resin which is in an uncured stated in the laying up process and when cut to produce the pieces A. Al. B. B l . Once the desired skin thickness has been built up. the wing-skins are then placed in an autoclave under heat and pressure to compress the fabric layers, create a bond between them and effect curing of the epoxy resin to complete the skin. The wing-skin may. however, be formed from layers of fabric to which a suitable bonding matrix is applied as described in our aforesaid co-pending application. By making up four wing skins as shown in Figure 2 and indicated at SK. the skins, when cured, can be orientated and used to form upper and lower surfaces on the wings 30.32 extending from a fuselage 33 of an aircraft as shown in Figure 4. If desired, the pieces A. B can be made from a first piece of fabric 34 and the pieces A, B from a separate second piece of fabric 35 rather than from a continuous piece By arranging the areas A, B and Al. Bl alongside each other in the manner shown in Figure 1. maximum use is made of the fabric with minimum wastage. Also, as the skin thickness can be effectively doubled by laying one piece upon another, it is necessary only to lay up the basic fabric 10, 12 instead of having to lay-up fabrics of double thickness thereby saving lay-up time. If desired smaller discrete pieces A. Al, B, B l can be made from single fabric lengths not joined at 20 and can be arranged in a similar manner to minimise wastage. However, using joined fabrics 10.12 is particularly advantageous as the wing skin construction time is reduced bv doine so.

Claims: CLAIMS 1. According to the invention there is provided a method of constructing a skin for a member of a body such as an aircraft, the method being characterised by providing from a multi-axial fabric (10, 12) first and second pieces (A, Al) shaped to correspond respectively to the shape of the member (30) to be covered by the skin and to the shape of a similar member (32) on the opposite side of the body (33), and inverting one of the pieces (A) and placing it on the other (Al), to form a skin (SK) for the member (30). 2. A method according to claim 1 characterised by providing third and fourth pieces (B, B l) from multi-axial fabric (10, 12), the pieces being shaped to correspond respectively to the shape of the member (30) to be covered by the skin and to the shape of the similar member (32) on the opposite side of the body (33) and inverting one of the third and fourth pieces (B) and placing it on the other (B l) to form a skin (SK) for the similar member (32). 3. A method according to claim 2 characterised by forming the first piece (A) and third piece (B) from areas of the fabric which lie alongside each other. 4. A method according to claim 2 or 3 characterised by forming the second piece (B) and the fourth piece (B l ) from areas of the fabric (10. 12) which lie alongside each other. 5. A method according to claim 3 or 4 in which the pieces are of elongate form and the areas of the fabric are elongate and extend substantially in a common longitudinal direction. 6. A method according to claim 4 or 5. characterised by forming the multi-axial fabric (10, 12) with a layer of 0° fibres extending in the longitudinal direction of said areas thereof. 7. A method according to any preceding claim characterised by forming the multi-axial fabric by joining together edges of a plurality a fabrics for example by a laying up process. 8. A method according to claim 7 characterised by producing at least one of the first and second pieces (A. Al) in such a way that said piece (A) is formed partly from one of said plurality of fabrics (10, 12) and partly of another joined thereto. 9. A method according to claim 7 or 8 in which a joint (20) between the two fabrics (10. 12) runs in the one of the axial directions of the multi-axial fabric. 10. A method according to claim 9 in which the joint (20) between the two fabrics (10, 12) runs in the 0° direction. 11. A method according to any preceding claim characterised in that the member is an aerofoil on the body and in that the method includes shaping the first and second pieces (A. Al) to correspond respectively to the plan view shape of the aerofoil (30) and to that of a similar aerofoil on the opposite side of the body (33). inverting one of the pieces (A) and placing it on the other (Al) to provide a skin for one of the aerofoils (30). 12. A method according to any preceding claim characterised by bonding the pieces (A. Al ; B, B l) together after placing them one upon the other. 13. An aircraft aerofoil such as a wing having a skin made in accordance with the method of anv of claims 1 to 1 1. 14. An aircraft having a skin made in accordance with the method of any of claims l to l l .

Inventors: GODBEHERE ANDREW PAUL, SPEAR ROBERT DAVID, WILLIAMS STEPHEN, GODBEHERE, ANDREW, PAUL, SPEAR, ROBERT, DAVID, WILLIAMS, STEPHEN
Applicants: BRITISH AEROSPACE, GODBEHERE ANDREW PAUL, SPEAR ROBERT DAVID, WILLIAMS STEPHEN, BRITISH AEROSPACE PLC, GODBEHERE, ANDREW, PAUL, SPEAR, ROBERT, DAVID, WILLIAMS, STEPHEN
Application year: 1999
Main classification: B29C70
IPC codes: B29C70, B64C3