Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-05-26
2002-11-26
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S212000, C156S256000, C428S036100, C428S072000, C428S134000, C428S137000
Reexamination Certificate
active
06485594
ABSTRACT:
The invention concerns a method for making composite fibre sandwich structures with upper and lower outer layer, at least one sectional core, and with a cut-out, in which the sectional core(s) are shaped and/or cut to size in accordance with the cut-out to be produced and the upper and lower outer layer are cut and cut to size in the region of the cut-out in matching fashion. It further concerns a composite fibre sandwich structure with upper and lower outer layer, at least one sectional core, and with a cut-out, in which the sectional core(s) are shaped and/or cut to size in accordance with the cut-out to be produced and the upper and lower outer layer are cut and cut to size in the region of the cut-out in matching fashion.
At the present time, the use of composite fibre structures with a large area is becoming increasingly important in the aircraft, ship and rail vehicle construction sectors.
As a consequence of their high load-bearing capacity combined with a low structural weight, sandwich structures with a sectional core and a composite fibre construction are often suitable for use here. Otherwise aluminium structures are used as an alternative. Thus, U.S. Pat. No. 3,912,380 proposes a sandwich structure for larger reflector mirrors with a honeycomb structure. The honeycomb structure is to consist of aluminium and the top and bottom are each provided with an appropriate coating to receive the mirror. Precisely in the centre of this structure, intended to form a telescope, a hole or through cut-out is provided, this cut-out being achieved by a simple cutting away of parts of the honeycomb structure and the outer layers.
However, door and/or window cut-outs also always have to be made in this walling for aircraft, ships or railway vehicles. As is well known, these are produced by making cut-outs in the solid material. It is very expensive to produce a durable structure notwithstanding, despite weakening the sandwich structure at this point. To implement an integral method of construction here for the cut-outs which is appropriate to composite fibre structures, reinforcing elements must be inserted where necessary, which is associated with the above-mentioned high expenditure as regards design and fabrication technology.
Therefore, the object of the invention is to propose a method of producing composite fibre sandwich structures with outer layers and sectional core and cut-outs and also such composite fibre sandwich structures themselves, by means of which a sandwich structure is feasible, which is appropriate to the stress and the fabrication method, with cut-outs for windows and doors for example.
The object is achieved in a method as described above in that the the upper and/or lower outer layer are so cut and cut to size, that cut-to-size components remain which initially partly cover the region of the cut-out, strips are laid or draped around the perimeter of the cut-out contour, the cut-to-size components of the upper and lower outer layer are wrapped around the shaped or cut-to-size sectional cores and the strips around the perimeter, appropriate to the composite fibre and the sandwich structure is soaked with resin and cured.
The object is achieved in a composite fibre sandwich structure as described above in that strips are provided which surround the cut-out and are applied to the walls of the sectional cores and in that the lower outer layer and/or the upper outer layer are shaped and/or cut in oversize manner in the area of the cut-out and project into the cut-out and cover the surrounding strips. Further embodiments of the invention are defined in the respective sub-claims.
The problem is solved by a method according to the generic part of claim 1 in that the sectional cores are shaped and/or cut to size as required for the cut-out to be produced, the upper and lower outer layers are cut through and cut to size appropriately in the area of the cut-out, strips are inserted or draped around the perimeter of the contour of the cut-out, the cut-to-size components of the upper and lower layer surround the sectional cores which have been shaped or cut to size and the surrounding strips suitable to the composite fibre construction and the sandwich structure is soaked with resin and cured. The problem is also solved by a composite fibre sandwich structure with upper and lower outer layer, at least one sectional core, and with a cut-out, in which the section cores are shaped and/or cut to size in accordance with the cut-out to be produced and the upper and lower outer layer are adjusted in the area of the cut-out by being cut and cut to size, which is characterised in that strips are provided which surround the cut-out and are applied to the walls of the sectional cores and in that the lower outer layer and/or the upper outer layer are shaped and/or cut in oversize manner in the area of the cut-out and project into the cut-out and cover the surrounding strips.
It is particularly preferable to integrate a frame into the design of the structure direct by using the shaping of the sectional cores, into which a window pane, for example, can be inserted direct and attached with adhesive. Consequently no further design measures are necessary for attaching a window pane of this type in the cut-out.
As a consequence of the advantageous layers of woven or non-woven material comprising the upper and lower outer surfaces, adjusted to the respective loadings occurring in the form of forces applied to the sandwich structure, and the shear elements within the sandwich structure, also in the area of the cut-out, no significant warping arises there. Therefore, a window pane inserted in this cut-out can be held almost without loading from forces acting within the sandwich structure.
Strips made of woven or non-woven fibre materials with a unidirectional orientation, placed in position in the area of the walls of the cut-out or shaped sectional cores, are given particular preference. In this case the strips are laid so that they run round the cut-out in an arrangement which is perpendicular to the outer layers. This transfers any forces in the direction around the cut-out, i.e. remaining in its plane. As a consequence of the advantageous and preferred positioning of the respective outer layers on the outside of these strips of material with a unidirectional orientation, the positive characteristics of the orientation of the fibres in the top and bottom layers can also be utilised in the area of the cut-out. Warping in the area of the support surface of a window pane with the preferred stepping as the shaping of the sectional cores surrounding the cut-out is also restricted advantageously to a very low level in the form of the two outer layers, laid one over the other, thus a double woven or non-woven layer.
The sectional cores are preferably each cut to size in steps in the area of the cut-out in such a way that a support surface is produced for elements to be inserted in the cut-out, such as, for example, window or door elements etc. Here the sectional cores should preferably either be removable silicone cores sheathed with a woven or non-woven fibre material, cut from non-removable, so-called lost foam cores, or pre-shaped as woven hoses in correspondingly pre-shaped master moulds and placed on the lower outer layer as pre-shaped hollow components.
It is particularly preferable to place the sectional cores on the lower outer layer made of woven or non-woven fibre material with an application-specific orientation, then to cut through or cut out the lower outer layer, especially diagonally for a rectangular cut-out, then to place the upper outer layer on the sectional cores and cut through it or cut it out and then wrap the cut areas of the outer layers round appropriately.
It is particularly preferable if the outer layers along the diagonals of the cut-out are cut through and the triangular elements or laps produced in this way are cut to size again in such a way that the area of their respective tips is cut off parallel to the edges of the cut-out with a defined overlap in respect of
Herrmann Axel
Pabsch Arno
Unckenbold Wilm Felix
Ball Michael W.
Deutsches Zentrum fur Luft -und Raumfahrt e.V.
Kilkenny Todd J.
Salter & Michaelson
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