GB2056888A

GB2056888A - Sandwich-type composite structural component

Info

Publication number: GB2056888A
Application number: GB8026079A
Authority: GB
Original assignee: Messerschmitt Bolkow Blohm AG
Current assignee: Airbus Defence and Space GmbH
Priority date: 1979-08-25
Filing date: 1980-08-11
Publication date: 1981-03-25
Also published as: FR2463677A1

Abstract

The composite structural component, which is more especially for use in the construction of thermally and mechanically highly-stressed lightweight structural member comprises a core in the form of a lattice 2 consisting of titanium powder shaped by hot-isostatic pressing and to which, after removal of any titanium oxide layer, metallic covering layers 3 are hard-soldered. The lattice 2 containing a honeycomb filling 4. The layers 3 may be of aluminium reinforced with boron fibres. <IMAGE>

Description

SPECIFICATION Sandwich-type composite structural component SPECIFICATION This invention relates to sandwich-type composite structural component having a core of titanium or titanium alloy and metal covering layers, more especially for the production of thermally and mechanically highly-stressed lightweight structural members.

Such composite components, in flying body and turbine constructions, are exposed to temperatures of up to 500,C and additionally to serve mechanical stresses, for example as a result of erosion, cavitation and foreign-body impact. Hitherto, the core parts have been either milled from the solid of prefabricated as forging blanks and brought to the desired final shape by reworking. These two methods involve high blank weights and a considerable amount of waste, and thus they generally involve high material and production costs.

The ratio of blank weight to end product weight additionally is considerably more unfavourable in the case of cores which, to save weight, are designed in a lattice or rib form of construction.

It has indeed already become known, as a result of United States Patent No. 4,029,838, to produce highly-stressed parts which are subject to surface erosion and corrosion from a laminar structure which consists alternatey of titanium and fibre-reinforced aluminium. In this proposal however, the layers of fibrereinforced aluminium are relatively thick, and the layers of titanium are relatively thin. Moreover, the layers are connected together by bonding. On account of the presence of the core layers of aluminium, which are softer as compared with the covering layers of titanium, and because the layers are connected by adhesive, these laminates are not suitable for structural components which are subjected simultaneously to very high mechanical and temperature stresses.

The task of the invention is therefore to provide a sandwich-type composite structural component which involves tolerable production expenditure, which provides saving on materials as compared with prior known proposals, and which withstands extremely high mechanical and stresses.

To solve this problem, the present invention provides a sandwich-type composite structural component having a core of titanium or titanium alloy and metal covering layers, more especially for the production of thermally and mechanically highly-stressed lightweight structural members, characterised in that the core consists of titanium powder which is shaped by hot-isostatic pressing and to which, after removal of any titanium oxide layer, the metal covering layers are hard-soldered.

Advantageous developments of the invention are set forth in claims 2 to 9 of the claims appended hereto.

In the composite structural component in accordance with the invention, the crude core produced by hot-isostatic pressing can be produced with only very little excess material present, so that in comparison with the finished mass only a slightly greater consumption of titanium powder is involved, and the time expanded in machining is very small.

Because the covering layers, consisting of light metal, more especially of aluminium reinforced with boron fibres, are applied by brazing or hard-soldering, even in the case of a core of lattice-like construction, the connection surfaces are sufficient to transmit practicallyencountered forces from the covering layers to the core. Particularly-favourable strength properties of the entire composite structural part are achieved when the covering layers consist of several sheets, arranged crosswise relative to one another, of aluminium reinforced with boron fibres.With the invention a new field of application for the hot-isostatic pressing is opened up and thus prejudices are dispelled that it is not possible to be able to produce structural components which are subject to high mechanical and temperature stresses such as surface components for flying bodies flying at several Mach, economically in lightweight sandwich type of construction.

The invention will be described further, by way of example, with reference to the accompanying drawing, in which: Figure 1 is a perspective view illustrating a flying body rudder construction in accordance with the invention; and Figure 2 is a section taken along the line Il-Il of Fig. 1.

A structural component in the form of a rudder 1, as shown in the figures, for a flying body is of sandwich construction and comprises a core in the form of a rib framework 2 built up in lattice-like manner and, on both sides, substantially identical covering layers 3.

In Fig. 1, a part of the upper covering layer 3 has been omitted, so that the rib framework 2 is shown partially in elevation. Provided between the rib framework 2, for further rigidity, is a honeycomb filling 4. For some specific instances of use, the honeycomb filling 4 can be omitted. To achieve a smooth rudder surface, as shown in Fig. 2, the covering layers 3 are let-in in a surrounding 5 of the rib framework 2. The rudder is mounted on a flying body fuselage (not shown) by means of a flange 6 and is also actuated by way of the latter.

The rib framework 2 is produced from titanium powder, for example from the titanium aluminium alloy TiAl 6V4, by hot-isostatic pressing (HIP). Although HIP is a known production method, the necessary work steps will be listed briefly hereinunder.

Production of a positive mould or pattern for HIP chill moulds from metallic or nonmetallic materials; Galvanic deposition of nickel onto the positive pattern; Loosening of the core material out of the resultant nickel chill mould; Analysis of the titanium powder; Filling of the HIP chill mould with titanium powder and carrying-out of the HIP operations; Stripping of the nickel capsule from the titanium HIP blank; and mechanical working of the outer surfaces on the HIP blank for the application of the covering layers with boron aluminium.

The covering layers 3 are, in the case of the illustrated rudder for a flying body which flies at about Mach 3, produced from several thin sheets of aluminium which is reinforced with boron fibres. The sheets, of about 0.2 mm thickness, are produced by layers of boron fibres being fixed by plasma-sprayed aluminium on an aluminium foil. To increase strength, five sheets having alternating fibre directions are placed one above the other and these are then brazed together. Instead of five sheets, depending on the stressings involved and the thickness of the individual sheets, more or fewer sheets may be used. The fibre alignments have to be determined by computation according to the expected stresses.

To prepare for the soldering of the covering layers 3 onto the ready-finished rib frame 2, the usual titanium oxide layer is removed from the frame 2 in known manner, for instance in a high vacuum. After that a protective metallic layer is immediately evaporated on or atomised on. Thereupon, the covering layers 3 can be applied to the rib framework 2 by hard soldering or brazing. An economical method involves carrying out the soldering in the eutectic temperature range of the metallic protective layer and of aluminium. In the liquid phase which results at this temperature range, the protective matallic layer serves also as soldering agent and diffuses into the covering layers. In this way there arises an extremely secure brazed connection, whereby the covering layers are united with the rib framework.

Claims

CLAiMS

1. A sandwich-type composite structural component having a core of titanium or titanium alloy and metal covering layers, more especially for the production of thermally and mechanically highly-stressed light-weight structural members, characterised in that the core consists of titanium powder which is shaped by hot-isostatic pressing and to which, after removal of any titanium oxide layer, the metal covering layers are hard-soldered.

2. A composite structural component as claimed in claim 1, characterised in that the core has a lattice-like structure.

3. A composite structural component as claimed in claim 2, characterised in that the lattice-like structure of the core is filled up by a filler.

4. A composite structural component as claimed in claim 3 characterised in that the filler is a honeycomb filler.

5. A composite structural component as claimed in any preceding claim characterised in that the covering layers consist of thin sheets of fibre-reinforced aluminium.

6. A composite structural component as claimed in claim 5, characterised in that the sheets for the covering layers consist of aluminium reinforced with boron fibres.

7. A composite structural component as claimed in any preceding claim characterised in that the individual sheets for the covering layers are soldered together prior to soldering onto the core.

8. A composite structural component as claimed in claim 7 characterised in that the titanium core is provided, prior to the soldering, with a thin metal protective layer, and the covering layers are soldered on at the eutectic temperature of the protective layer and of the aluminium.

9. A composite structural component as claimed in any preceding claim characterised in that the edges of the structural component consist completely of titanium and the covering layers are let into the core with an edge spacing so that they form a flat surface with the edge of the core.

10. A composite structural component substantially as hereinbefore described with reference to and as illustrated in the accompanying drawing.