GB2382323A

GB2382323A - Bonding a flanged tube to a laminate base

Info

Publication number: GB2382323A
Application number: GB0222281A
Authority: GB
Inventors: Dipl-Ing Christoph Breu
Original assignee: EADS Deutschland GmbH
Current assignee: Airbus Defence and Space GmbH
Priority date: 2001-10-04
Filing date: 2002-09-25
Publication date: 2003-05-28
Anticipated expiration: 2022-09-25
Also published as: FR2830482B1; GB2382323B; DE10148950C2; GB0222281D0; FR2830482A1; DE10148950A1

Abstract

A fibre reinforced structure comprises a laminar base with at least one upstanding element 6 by means of which, further elements can be attached to the base. The base comprises an upper 4,5 and a lower 2,3 layer, the upstanding element 6 being a tube having a flange 8 sandwiched between, the upper and 4,5 and lower 2,3 layers. Also disclosed is a method in which the above described item is made by resin bonding the various parts to each other. The fibre reinforcement may be provided by carbon fibre. Each layer 2,3 and 4,5 may itself be formed of multiple layers, 2,3,4,5.

Description

Sheet structure with force-introducing elements The invention relates to a

generally sheet-like component, such as a CFRP structure, having force 5 introducing elements enabling fixing to other components. In order to bind additional structures made of FRP (fibre-reinforced plastics) or other materials to fibre-composite components, these structures are often 10 cemented thereto or secured with the aid of screws or rivets. The disadvantage of these known techniques is either a weakening of the material of the components when screws or rivets are used or a lack of form-

closure or positive locking of the connections when the 15 adhesion technique is used.

An object of the invention is to provide curved or planar CFRP structures that have adequate force-

introducing elements. The invention is defined in claim 1. Embodiments provide a CFRP structure having 20 one or more force-introducing elements, in which the force-introducing elements are formed so as to be tubular or as a hollow profile section with a profile cross section that differs from the ring, in that the force-introducing elements are each made from one or 25 more carbon fibre braided sleevings which are slipped one on top of the other, in that the carbon fibre braided sleevings are each widened at one end to form a flange with which they are inserted into the CFRP structure between two multiaxial layers when the 30 preform for the CFRP structure is produced, and after impregnation and hardening of the structure are held in a form-closing manner in the CFRP structure.

With embodiments of the invention the force-

introducing elements are made from one or more carbon 35 fibre braided sleevings or tubes. The braided sleevings are widened at one end to form a flange. By means of this flange the force-introducing elements can be bound in between layers of the CFRP structure in a

manner that prevents withdrawal of the sleeve. The insertion of the forceintroducing elements between the multiaxial layers is effected when the preform of the CFRP structure is manufactured.

5 The use of carbon-fibre braided sleevings makes it possible to produce the force-introducing elements in a short time with simple tools. The flexibility of the braided sleevings advantageously enables force introducing elements to be bound into CFRP structures 10 of various shapes, from a simple sheet to quite complex forms. Compared with binding force-introducing elements by subsequent adhesion of the elements onto the surface of the CFRP structure, the solution in accordance with the invention presents the advantage 15 that one process step fewer is required, since the force-introducing elements in accordance with the invention are integrated into the CFRP structure with the production of the preform. A further advantage in comparison with force-introducing elements is that 20 greater forces can be transferred into the CFRP structure with the force-introducing elements in accordance with the invention.

The invention also relates to a method for making such a structure, in which the flanged ends of braided 25 sleeves are held between layers to form a base structure with protruding tubes.

For a better understanding of the invention embodiments of it will now be described, by way of 30 example, with reference to the accompanying drawings, in which: Figure 1 shows a cut-away portion of a CFRP structure having a force-introducing 35 element in accordance with the invention; Figure 2 shows the construction principle of the preform for a CFRP structure in accordance with the invention; and

Figure 3 shows the construction of the preform at the stage at which the carbon fibre braided sleevings have been slipped onto the support bodies 10 and have been made to 5 protrude at their supported end to form a respective flange 8.

Figure 1 shows a cross-section through a part of CFRP structure 1 which constructed with four 10 superimposed multiaxial layers 2, 3, 4, 5 forming a base. A force-introducing element 6, which is integrated into the CFRP structure 1 at this point, is formed, for example, as a tube that is circular in cross-section and of limited length, comparable with 15 its diameter. It consists of a carbon fibre braided sleeving 7. The single-layer construction of the force-introducing element 6 that is shown in this embodiment can be replaced, according to the wall thickness that is required, by a multi-layer 20 construction in which two or more carbon fibre braided sleevings 7 are drawn one over the other.

The force-introducing element 6 is upstanding from the phase of the base at that point and has at its end that is integrated into the CFRP structure a pre-formed 25 flange 8. The force-introducing element 6 is held between the inner multi-axial layers 3 and 4 by means of this flange 8. The flange has a horizontal extent also comparable with the diameter of the tube.

As an alternative to the force-introducing 30 element 6 presented above, it is also possible with the braided sleevings to realize different crosssections of the tube other than circular ones, since the braided sleevings are very flexible; for example hollow profile sections that have a rectangular cross-section can be 35 realized. The hole in the upper layers of the base should correspond to the cross-section of the sleeve.

It is possible for a plurality of force-

introducing elements 6 to be integrated in a CFRP

structure, if required. For example, two force introducing elements 6 are integrated into the CFRP structure now to be described with reference to Figure 2.

5 Figure 2 shows the construction of a preform for a CFRP structure that has force-introducing elements in accordance with the invention. The preform is assembled on a laying device 9 which has two projecting, cylindrical support bodies 10 for the 10 formation of two forceintroducing elements. The cross-section of the cylindrical support bodies 10 is matched to the inner cross section of the respective tubular or profile section-shaped force-introducing element. 15 In this embodiment, two multiaxial layers 2 and 3 are provided below the flange 8 of the force introducing elements 6 and two multiaxial layers 4 and 5 are provided above the elements, though there could be any number of such layers above and below.

20 Two respective circular openings 11 are cut into the multiaxial layers 2 to 5 at the positions provided for the force-introducing elements.

The diameters of the openings 11 on the lower multiaxial layers are matched to the diameters of the 25 support bodies 10 so that these can pass straight through the openings. The diameters of the upper openings 11 are matched, for example, to the outside diameters of the carbon fibre braided sleeving 7 or composite sleevings 7. However, the diameters of the 30 openings 11 can also be formed somewhat larger, as long as the flanges 8 of the force-introducing elements 6 are then still held to a sufficient extent between the multiaxial layers.

Instead of the embodiments described above, if 35 required the CFRP structure can be constructed out of more than or less than four multiaxial layers - an odd number is also possible - with it being necessary to

use at least two layers between which the flange of the force-introducing element is inserted.

Figure 3 shows the construction of the preform at the stage at which the braided sleevings have been 5 slipped onto the support bodies 10 and have been made to protrude at their supported ends to form a respective flange 8. The lower multiaxial layers 2 and 3 are already placed onto the laying device 9 at this stage and the braided sleevings 7 are slipped over 10 the support bodies 10 which pass through the openings 11 of the multiaxial layers 2 and 3. When slipping on the flexible braided sleevings 7, by applying sufficient thrust the lower end of a braided sleeving 7 is widened and deflected outwards so that 15 the respective flange 8 is formed. However, the flange could instead be fully or partly preformed.

In this connection, before the flange is widened, as an auxiliary measure the carbon fibre braided sleeving 7 can be held together by binding the tubular 20 part with a sleeving-binder or a tear-off fabric tape so that only the desired flange region is widened during the pressing-on process.

Subsequently, the openings 11 of the two upper multiaxial layers 4 and 5 are placed over the braided 25 sleevings 7 that have been slipped on and the preform is impregnated with resin in the usual way and hardened to form the CFRP structure 1.

Claims

1. A fibre-reinforced structure comprising a generally laminar base and at least one upstanding 5 element (6) by means of which further elements can be attached, in which the base comprises at least an upper (4, 5) and a lower (2, 3) layer, and the upstanding element is in the form of a rod or tube having a flange (8) at one end, this flange being 10 held between the upper and lower layers of the base.

2. A fibre-reinforced structure according to claim 1, in which either or both of the base and the 15 element is made of carbon-fibre-reinforced plastics.

3. A structure according to claim 1 or 2, in which one or both of the base layers itself has two or 20 more multiaxial layers (2, 3; 4, 5).

4. A method of making a fibre-reinforced structure having a generally laminar base and one or more protruding force-introducing elements, the or each 25 force-introducing element (6) being tubular or of a hollow profile section, in which the or each element is widened at one end to form a radial flange (8), and the flange is inserted between two multiaxial layers (2, 3, 4 and 5) making up the 30 base, so as to form a preform for the CFRP (1); and the preform is then impregnated and hardened so as to lock the components together.

5. A CFRP structure substantially as described herein 35 with reference to the accompanying drawings.