Patent Description:
The present invention relates to a method of manufacturing a multilayer member for aeronautic and aerospace applications.

Multilayer members for aeronautic and aerospace applications comprise thermal straps. The thermal straps used in the aeronautical and aerospace fields are generally of two types.

In a first type, the thermal strap comprises a stack of thermally conductive sheets made of a metallic material such as, for example, aluminium or copper or alloys thereof or of a non-metallic material such as, for example, graphite or graphene or carbon fibres.

The sheets have, for example, an elongated rectangular shape, and comprise a flexible central portion and two mechanical coupling interfaces on opposite sides of the central portion to enable the thermal strap to be connected to the two objects.

The sheets are mutually separated at the central portion, and are mutually connected, for example through pressing, at the mechanical coupling interfaces.

Generally, each mechanical coupling interface is connected to the corresponding object through at least one screw or clamping bolt mounted through the sheets.

In the second types, the thermal strap comprises at least one braid or strand comprising, in turn, a plurality of thermally conductive wires made of a metallic material such as, for example, aluminium or copper or alloys thereof or of a non-metallic material such as, for example, graphite or graphene or carbon fibres.

The braid or strand comprises a flexible central portion and two mechanical coupling interfaces on opposite sides of the central portion to enable the thermal strap to be connected to the two objects.

The wires are mutually separated at the central portion, and are mutually connected, for example through pressing, at the mechanical coupling interfaces.

Generally, each mechanical coupling interface is connected to the corresponding object through at least one screw or clamping bolt mounted through the wires.

<CIT> discloses flexible connector comprising a multilayer metal strip and at least one connecting element arranged at at least one strip end, wherein the layers of the metal strip are joined together in the region of the strip end by friction welding, and a reinforcement element (<NUM>) is arranged at the strip end (<NUM>) and is bonded to the strip.

<CIT> discloses a heat transfer system comprising a heat source, a first heat exchanger coupled to the heat source to remove heat from the heat source, and a second heat exchanger, which is coupled to the first heat exchanger to remove heat from the first heat exchanger. The heat transfer system also comprises, furthermore, a heat duplicator coupled to the second heat exchanger to remove heat from the second heat exchanger, a first heat pipe coupled to the heat duplicator to remove heat from the heat duplicator, and a second heat pipe, which is coupled to the first heat pipe to remove heat from the first heat pipe.

<CIT> discloses a method of diffusion bonding and forming metallic sheets. The method comprises stacking a first metallic sheet and a second metallic sheet to define a sheet slack; creating a pneumatic seal between the first metallic sheet and the second metallic sheet to define a sealed sheet stack that defines a pneumatically isolated region; increasing a surface area of the sealed sheet stack to define an expanded sheet stack; and compressing at least a portion of the expanded sheet stack to form a diffusion bond between a corresponding portion of the first metallic sheet and an opposed portion of the second metallic sheet, thereby defining a diffusion bonded sheet stack.

The article "Pyrolytic Graphite Film Thermal Straps: Characterization Testing" assesses feasibility of replacing standard aluminium sheets in thermal belts with a more conductive and lighter graphite film.

The article "Thermal conductance characterization of a pressed copper rope strap between <NUM> and <NUM>" relates to a method of mechanical pressing the ends of a solid copper braid to build seamless conductive belts for cryogenic applications.

Known thermal straps of the above-described type have some drawbacks mainly due to the fact that, at the mechanical coupling interfaces, each pair of adjacent sheets or wires exposes a discontinuity of material, which leads to additional thermal resistance, and limits the correct and homogeneous transmission of heat along the thermal strap.

Known thermal straps of the above-described type also have the additional drawback that the costs and time for their procurement are relatively high.

The aim of the present invention is to provide a method of manufacturing a multilayer member for aeronautic and aerospace applications.

According to the present invention, a method of manufacturing a multilayer member for aeronautic and aerospace applications is provided, as claimed in claims <NUM> and <NUM>.

The present invention will now be described in detail with reference to the appended figures to make it possible for persons skilled in the art relevant to the present invention to produce and use it. Various modifications to the described embodiments will be readily apparent to those persons skilled in the art, and the general principles described may be applied to other embodiments and applications without however departing from the protective scope of the present invention, as defined in the appended claims. Accordingly, the present invention is not to be limited in scope to the embodiments described and illustrated herein, but is limited by the scope of the appended claims.

With reference to <FIG>, reference numeral <NUM> references, as a whole, a thermal strap to mutually connect two objects (not shown), in particular two objects having different temperatures.

The thermal strap <NUM> comprises a stack <NUM> of thermally conductive sheets <NUM>. The stack <NUM> comprises a number of sheets <NUM> ranging between <NUM> to <NUM>, and each sheet <NUM> has an elongated rectangular shape and is <NUM> to <NUM> thick.

Sheets <NUM> are made of a thermally conductive metallic material such as, for example, aluminium or copper or alloys thereof, or of a thermally conductive non-metallic material such as, for example, graphite or graphene or carbon fibres.

Preferably, but not necessarily, sheets <NUM> are made of the same material and have the same thickness.

Thermal strap <NUM> further defines a flexible central portion <NUM>, where sheets <NUM> are mutually separated, i.e., they are not mutually connected, and two end portions <NUM> arranged on opposite sides of the flexible central portion <NUM>.

At each end portion <NUM>, sheets <NUM> are mutually welded and further welded to a pair of thermally conductive straps <NUM>, which are arranged on opposite sides of sheets <NUM>, are made of either the same material as, or a different material from, sheets <NUM>, and each of which is thicker than a sheet <NUM>, in particular a thickness of at least <NUM>.

Sheets <NUM> and straps <NUM> are mutually welded through a Friction Stir Welding (FSW) process, namely a solid state friction stir welding and remixing process wherein the material to be welded fails to reach melting temperature and the weld bead is generated by contact between a rotating welding tool, straps <NUM>, and sheets <NUM>. In particular, the welding tool comprises a shoulder, rotation of which generates friction and, hence, heat, making the material plastic; and a pin, the rotation of which remixes the plasticised material by mutually joining sheets <NUM> and straps <NUM>.

Higher thickness of straps <NUM> enables correct execution of the Friction Stir Welding process, avoiding any damage to and/or breakage of thinner sheets <NUM>.

Each end portion <NUM> defines a mechanical connection interface provided with a pair of coupling holes <NUM>, which enable end portion <NUM> to be connected to the corresponding object (not shown) through respective clamping screws (not shown) or respective clamping bolts (not shown) mounted through coupling holes <NUM>.

Obviously, the number of holes <NUM> in each mechanical connection interface may be different from two.

In a variant not shown, each end portion <NUM> is joined to only one strap <NUM> arranged on an end face of stack <NUM> where welding of sheets <NUM> and of strap <NUM> is carried out.

The variant shown in <FIG> differs from what is shown in the previous Figures only in the thermal strap <NUM> further comprising an end sheet <NUM>, which has substantially the same shape as sheets <NUM>, and is interposed between the stack <NUM> of sheets <NUM> and the two straps <NUM>.

Sheet <NUM> is made of either the same material as, or a different material from, sheets <NUM>, and is thicker than a sheet <NUM>.

Sheets <NUM>, straps <NUM>, and sheet <NUM> are mutually welded at the two end portions <NUM> through Friction Stir Welding. Sheets <NUM> and <NUM> are mutually separated, i.e., they are not mutually connected, at the flexible central portion <NUM>.

In a variant not shown, thermal strap <NUM> comprises two sheets <NUM> arranged on opposite sides of the stack <NUM> of sheets <NUM>.

In a further variant not shown, straps <NUM> are removed and sheets <NUM> and <NUM> are mutually welded at the end portions <NUM> to define corresponding mechanical connection interfaces, and are mutually separated, i.e., they are not mutually connected, at the flexible central portion <NUM>.

<FIG> shows a thermal strap <NUM> having at least one braid or strand <NUM> comprising a plurality of thermally conductive wires <NUM> made of a metallic material such as, for example, aluminium or copper or alloys thereof, or of a non-metallic material such as, for example, graphite or graphene or carbon fibres.

Preferably, but not necessarily, wires <NUM> are made of the same material and have the same diameter.

Thermal strap <NUM> further comprises a flexible central portion <NUM>, at which wires <NUM> are mutually separated, i.e., they are not mutually connected, and two end portions <NUM> arranged on opposite sides of the flexible central portion <NUM>.

At each end portion <NUM>, wires <NUM> are mutually welded and also welded to a pair of thermally conductive straps <NUM>, which are arranged on opposite sides of wires <NUM>, are made either of the same material as, or a different material from, wires <NUM>, and each of which has a given thickness, in particular a thickness of at least <NUM>.

Wires <NUM> and straps <NUM> are mutually welded through a Friction Stir Welding process.

Each end portion <NUM> defines a mechanical connection interface provided with a pair of coupling holes <NUM>, which enable end portion <NUM> to be connected to the corresponding object (not shown) through respective clamping screws (not shown) or respective clamping bolts (not shown) mounted through holes <NUM>.

Welding of sheets <NUM> with straps <NUM> and/or sheet <NUM>, and welding of wires <NUM> with straps <NUM> enable a continuous heat path to be created within end portions <NUM> and <NUM>, so maximising heat transmission along thermal straps <NUM> and <NUM>. Flexibility of central portions <NUM> and <NUM> guarantees thermal straps <NUM> and <NUM> a relatively high versatility and ease of use.

<FIG> show a multilayer member <NUM> for use, for example, as a meteoritic impact protection panel.

Multilayer member <NUM> comprises a stack <NUM> of sheets <NUM> having, in the example shown, a quadrilateral shape. Obviously, in a variant not shown, sheets <NUM> may have a different shape from quadrilateral.

Stack <NUM> comprises a number of sheets <NUM> ranging between <NUM> to <NUM> and each sheet <NUM> is <NUM> to <NUM> thick, and is made of either a metallic material such as, for example, aluminium or aluminium metallic alloys or a non-metallic material such as, for example, a polymeric material.

Multilayer member <NUM> further comprises an end sheet <NUM>, which has substantially the same shape as sheets <NUM>, overlaps sheets <NUM>, is made of either the same material as or a different material from, sheets <NUM>, and is thicker than a sheet <NUM>.

In a variant not shown, multilayer member <NUM> comprises two sheets <NUM> arranged on opposite sides of sheets <NUM>.

Stack <NUM> comprises a central portion <NUM> and a perimetral edge <NUM> extending around at least part of portion <NUM>.

Sheets <NUM> and <NUM> are mutually separated, i.e., they are not mutually connected, at the central portion <NUM>, and are mutually welded along at least part of perimetral edge <NUM>.

In particular, sheets <NUM> and <NUM> are mutually welded at the perimetral edge <NUM> through a Friction Stir Welding process.

Higher thickness of sheet <NUM> enables the correct execution of the Friction Stir Welding process, so avoiding any damage to and/or breakage of thinner sheets <NUM>.

In a variant not shown, sheet <NUM> is replaced with a strap, which is arranged along perimetral edge <NUM>, is made of either the same material as or a different material from, sheets <NUM>, and is thicker than a sheet <NUM>.

Claim 1:
A method of manufacturing a multilayer member (<NUM>) for aeronautic and aerospace applications comprising:
- forming a stack (<NUM>) of sheets (<NUM>), wherein the stack (<NUM>) comprises a number of sheets (<NUM>) ranging between <NUM> to <NUM>, and wherein each sheet (<NUM>) is <NUM> to <NUM> thick; and
- at least partially mutually welding the sheets (<NUM>) through Friction Stir Welding along at least part of a perimetral edge (<NUM>) of the stack (<NUM>) of sheets (<NUM>) to form the multilayer member (<NUM>).