WO2017080841A1

WO2017080841A1 - Method of manufacturing a fibre metal laminate material

Info

Publication number: WO2017080841A1
Application number: PCT/EP2016/075946
Authority: WO
Inventors: Florian LANDGRAF
Original assignee: Aleris Rolled Products Germany GmbH
Current assignee: Novelis Koblenz GmbH
Priority date: 2015-11-13
Filing date: 2016-10-27
Publication date: 2017-05-18
Anticipated expiration: 2018-05-13
Also published as: DE112016005215T5

Abstract

The invention relates to a method of manufacturing a fibre metal laminate material having two external faces and comprising N aluminium sheet layers, said N aluminium sheet layers being the same or different, and N-1 polymer layers alternating in said laminate material with said aluminium sheet layers, wherein N is equal to at least 2, and wherein each of said polymer layers comprises high strength fibres, the method comprising the steps of: unwinding in a continuous process from coils at least two aluminium sheets and feeding these to a pressure unit, unwinding from coil(s) sheet(s) of prepreg-material comprising of high strength fibres embedded in a polymer for forming the polymer layer(s), feeding of the sheet of prepreg-material between two aluminium sheets to said pressure unit, applying pressure at elevated temperature to form a fibre metal laminate material, cooling of the fibre metal laminate material, and wherein the polymer of the prepreg-material is a semicrystalline or paracrystalline thermoplastic polymer having a crystalline melting point T_m of greater than 170°C, and preferably greater than 270°C.

Description

METHOD OF MANUFACTURING A FIBRE METAL LAMINATE MATERIAL

FIELD OF THE INVENTION

The present invention relates to a method of manufacturing a fibre metal laminate material, the fibre metal laminate material has two external faces, comprising: N aluminium sheet layers, and N-1 polymer layers alternating in said laminate material with said aluminium sheet layers, wherein N is equal to at least 2, and wherein each of said polymer layers comprises high strength fibres, in particular glass fibres.

BACKGROUND OF THE INVENTION

An increasing demand in particular in the aircraft industry for high- performance, lightweight structures have stimulated a strong trend towards the development of refined models of fibre-metal laminated materials. Similar trends can be found for space components and other structural engineering components. Fibre metal laminates are hybrid composite materials built up form alternating layers of thin metals (commonly aluminium) and plies of fibre reinforced polymeric materials. The most commercially available fibre metal laminates are ARALL (Aramid Reinforced Aluminium Laminate) based on aramid fibres, and GLARE (Glass Reinforced Aluminium Laminate) based on high strength glass fibres. Taking advantage of the hybrid nature from their two key constituents (metals and fibre-reinforced laminate) these composite materials offer several advantages such as better damage tolerance to fatigue crack growth and impact damage especially for aircraft applications. Metallic layers and fibre reinforced laminates can be bonded by classical tech- niques, i.e. mechanically and adhesively. Adhesively bonded fibre metal laminates have shown to be more fatigue resistant than mechanically bonded structures.

To produce fibre metal laminate materials the most common process involves autoclave processing, which is both time consuming and expensive. The overall scenario for the production of fibre metal laminate materials involves the following processing steps:

(a) Preparation of tools and materials. During this step, the aluminium layer surfaces can be pre-treated to improve the adhesive bonding between the aluminium and the fibre reinforced laminate;

(b) Material deposition, including cutting, lay-up and debunking. Generally, composite panels are manufactured from tapes of prepregs (pre-impregnated fibers) consisting of various types of reinforcing fibers impregnated with a thermoplastic or thermosetting adhesive. These thin sheets of prepreg are then arranged in various configurations and built up to a desired thickness by "laying them out" on a flat or in a component shape curved surface and stacking them to the desired thickness. It is advantageous to use the fiber-reinforced composite layer in the form of a pre-impregnated semi-finished product. Such a "prepreg" shows generally good mechanical properties after curing thereof, among other reasons because the fibers have already been wetted in advance by the matrix polymer.

(c) Cure preparation, including the tool cleaning and in many cases the part transferring, and in almost all cases the vacuum bag preparation.

(d) Curing, the chemical curing reactions, as well as to establish a bond between the fibre and the aluminium layers. In an autoclave it is heated to the required curing temperature for the required curing time and the required pressure is applied. Upon cooling to room temperature, a solid composite laminate material is obtained. (e) As the case may be possibly post-stretching after the curing cycle that may reverse the residual stress over the thickness of the material;

(f) Inspection, for example by means of ultra-sonic inspection, for the quality of the resultant fibre metal laminate material.

Patent document DE-102012000508-A1 discloses a method of producing a multi-layered component, preferably a glass laminate aluminium reinforced epoxy component, comprising the steps of arranging alternating layers of aluminium and prepreg sheets on a surface of a laminating- and adhesive-device, where outer layers of finished component are respectively formed from aluminium sheets, and wherein the prepreg sheets are fixed on the aluminium sheets by an electrostatic charge.

There is a demand for a manufacturing process of fibre metal laminate material which limits the amount of manual handling.

DESCRIPTION OF THE INVENTION

As will be appreciated herein below, except as otherwise indicated, aluminium alloy designations and temper designations refer to the Aluminium Association designations in Aluminium Standards and Data and the Registration Records, as published by the Aluminium Association in 2015 and well known to the persons skilled in the art.

For any description of alloy compositions or preferred alloy compositions, all references to percentages are by weight percent unless otherwise indicated. The term "up to" and "up to about", as employed herein, explicitly includes, but is not limited to, the possibility of zero weight-percent of the particular alloying component to which it refers. For example, up to about 0.2% Ti may include an alloy having no Ti. It is an object of the present invention to provide a method of manufacturing fibre metal laminate materials having polymer layers comprising high strength fibres.

It is another object of the present invention to provide a method of manufacturing fibre metal laminate materials having polymer layers comprising glass fibres.

These and other objects and further advantages are met or exceeded by the present invention providing a method of manufacturing a fibre metal laminate material, the fibre metal laminate material has two external faces and comprising N aluminium sheet layers, said N aluminium sheet layers being the same or different, and N-1 polymer layers alternating in said laminate material with said aluminium sheet layers, wherein N is equal to at least 2, and wherein each of said polymer layers comprises high strength fibres, the method comprising the steps of:

(a) unwinding in a continuous process from coils at least two aluminium sheets and feeding these to a pressure unit;

(b) unwinding from coil(s) sheet(s) of prepreg-material comprising of high strength fibres embedded in a polymer for forming the polymer layer(s);

(c) feeding of the sheet of prepreg-material between two aluminium sheets to said pressure unit;

(d) applying pressure at elevated temperature to the aluminium sheets and to the prepreg-material interposed between the aluminium sheets to form a fibre metal laminate material and which is performed at a temperature in the range of 150°C to 400°C, preferably in the range of 280°C to 400°C; (e) cooling of the fibre metal laminate material on leaving the pressure unit;

(f) coiling or cutting-to-length of the fibre metal laminate material; and wherein the polymer of the prepreg-material is a semicrystalline or paracrystal- line thermoplastic polymer having a crystalline melting point T_m of greater than 170°C, and preferably greater than 270°C.

The invention provides a continuous process of manufacturing fibre metal laminate materials. The amount of manual handling is significantly reduced and thereby making the manufacturing process more time and cost efficient.

Depending on the intended use and requirements set, the optimum number of aluminium sheets can easily be determined by the person skilled in the art. Although the invention is not restricted to fibre metal laminate materials with a maximum number of aluminium sheets, in practice the number will be in a range of 2 to 10, for example 2, 3, or 4.

The method according to the invention can be applied using a wide range of aluminium alloy sheet materials, for example alloys of the AA2000 and AA7000- series alloys, for example AA2024, AA2524, AA7075 and AA7475.

In a preferred embodiment at least one of the two external faces, and preferably at least both external faces, of the fibre metal laminate are made of an aluminium non-heat treatable alloy. In particular aluminium alloys of the AA5000-series are preferred, such as alloys selected from the group of 5024, 5028, 5059, 5082, 5083, 5383, 5182, 5086, 5186, and 5456.

In a more preferred embodiment all aluminium sheets in the fibre metal laminate material are made of an AA5000-series alloy. More in particular Al-Mg-Sc alloys are preferred comprising Mg in the range of 3% to 8% in combination with a purposive Sc addition in the range of 0.02% to 1 %, and preferably 0.1 % to 1 %. Such Al-Mg-Sc alloy may further comprise 0.2% to 1 % Mn, and up to 1 % of at least one element forming dispersoids selected from the group consisting of Zr, Cr, Hf, La, Ti, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er, Y, and Yb. The balance is typically made by Cu up to 0.1 %, Fe up to 0.40%, and Si up to 0.30%, and unavoidable impurities (each <0.05%, total <0.15%) and aluminium. Optionally the alloy may contain up to 2% Zn.

Very suitable Al-Mg-Sc alloys are those selected from the group of AA5024 and AA5028, and modifications thereof.

In order to achieve a good balance of strength, fatigue properties and corrosion resistance, the AA5000-series sheet materials, in particular AA5024 and AA5028 sheet materials, are preferably provided in an H1 condition, more preferably in an H1 X, and more preferably an H1 16 condition.

An H1 temper means that the alloy sheet is strain hardened. In some embodiments, the alloy sheet may be strain hardened in accordance with typical H1 X, where X is a whole number from 0 to 9. This second digit following the designations H1 indicates the final degree of strain hardening.

In order to enhance bonding between polymer and the aluminium sheets, preferably the aluminium sheets are being pre-treated as known in the art, preferably by means of anodizing.

Although the thickness of the polymer layers and the aluminium sheets may be varied within a large range, in a preferred embodiment the thickness of the aluminium sheets is between about 0.1 mm to 1 .5 mm. A more preferred lower limit is about 0.3 mm. A more preferred upper limit is about 0.8 mm. The fiber-reinforced composite layers in the fiber-metal laminates according to the invention are light weight and strong and comprise reinforcing fibers embedded in a polymer. The polymer may also act as a bonding means between the various metal layers. Preferred reinforcing high strength fibers that are suitable for use in the fiber-reinforced composite layers are carbon fibers, aramid fibers or glass fibers. More preferred fibers include reinforcing fibers with a relatively high tensile strength and/or stiffness, of which class high strength glass fibers, such as S2-glass fibers, and HS2 and HS4 fibers (PPG) are particularly preferred. Preferred reinforcing fibers include glass fibers having a tensile strength of at least 3 GPa, more preferred of at least 3.5 GPa, even more preferred of at least 4 GPa, and most preferred of at least 4.5 GPa. Other preferred reinforcing fibers include glass fibers having a tensile modulus of at least 70 GPa, more preferred of at least 80 GPa, even more preferred of at least 85 GPa, and most preferred of at least 90 GPa. Another preferred range of glass fibers has a tensile modulus of at most 100 GPa. The most preferred reinforcing fibers include glass fibers having a tensile strength of at least 3 GPa, and a tensile modulus of at least 80 GPa, and/or a tensile modulus of at most 100 GPa.

The preferred thermoplastic polymers further comprise an almost amorphous thermoplastic polymer having a glass transition temperature Tg of greater than 140°C, preferably greater than 160°C, such as polyarylate (PAR), polysulphone (PSO), polyethersulphone (PES), polyetherimide (PE1 ) or polyphenylene ether (PPE), and in particular poly-2,6 dimethyl phenylene ether.

According to the invention, more preferably semicrystalline or paracrystalline thermoplastic polymers are being applied and having a crystalline melting point T_m of greater than 170°C, preferably greater than 270°C, such as polyphenylene sulphide (PPS), polyetherketones, in particular polyetheretherketone (PEEK), poly- etherketone (PEK) and polyetherketoneketone (PEKK), "liquid crystal polymers" such as XYDAR by Dartco derived from monomers biphenol, terephthalic acid and hydrobenzoic acid. Suitable matrix materials also comprise thermosetting polymers such as epoxies, unsaturated polyester resins, melamine/formaldehyde resins, phenol/formaldehyde resins, polyurethanes.

In a more preferred embodiment of the invention the polymer is based on pol- yphenylene sulphide (PPS).

In another more preferred embodiment of the invention the polymer is based on polyether ether ketone or sometimes also written as polyetheretherketone (PEEK).

In another preferred embodiment of the invention the polymer is based on pol- yetherketoneketone (PEKK).

In particular polymers based PPS, PEEK and PEKK have a melting temperature in the range of the creep forming temperature of AIMgSc sheet alloys, e.g. AA5024 or AA5028, and thereby provide the possibility to form fiber metal laminate material at elevated temperatures to impose a curvature on that fiber metal laminate material.

In a more preferred embodiment the polymer based material PPS, PEEK or PEKK is combined with S2-type glass fibres.

In an embodiment of the method at least the sheet of prepreg material is being preheated to a temperature avoiding melting of the polymer, and is preferably in a range of about 150°C to about 300°C, and more preferably of about 150°C to about 270°C, prior to being fed into the pressure unit. More preferably also the aluminium sheets are being preheated prior to being fed into the pressure unit. This can be achieved by heating the various sheets using for example convection heating or infrared heating. It is also feasible to preheat all the sheets by continuously moving these through a heating chamber being heated to the required temperature. The pressing unit include an upper pressurizing means and a lower pressurizing means and the fibre metal laminate is fed in a continuous fashion between the upper pressurizing means and the lower pressurizing means. The applied pressure should not exceed 30 bar, and is preferably in a range of 5 to 20 bar.

The applied pressure is preferably such that there is imparted to the laminate in its entirety a permanent specific elongation in the range of less than 1 .5%, more particularly less than 1 % in the direction of the length of the aluminium sheets. More preferably the applied pressure is such that the elongation imparted to the laminate in its entirety by the pressing operation is not more than the elastic elongation of the metal sheets such that the aluminium sheets being subjected to substantially no plastic deformation during the pressing process.

The pressing unit may comprise of a continuous press provided with a twin band unit formed by a pair of revolving endless belts in which the bands are heated such that the polymer in the laminate is brought to a temperature of preferably at least about 280°C, and more preferably of at least about 300°C. Alternatively, the continuous press can be positioned in a chamber with temperature restoration means for maintaining a temperature in a range of about 150°C to 400°C.

Alternatively, the pressing unit may comprise of at least one pair of cooperating, pressure loaded rolls, and preferably a series of pairs of cooperating, pressure loaded planishing rolls. The pressing step by means of at least one set rolls taking place at a substantially constant temperature in a chamber with temperature restoration means for maintaining a temperature in a range of about 150°C to 400°C.

On leaving the pressure unit the fibre metal laminate material is being cooled, preferably to ambient temperature. Most preferably the cooling is carried out by maintaining pressure, typically in a range of up to about 20 bar, to the continuously moving fibre metal laminate material to prevent delamination between the aluminium sheets and the polymer material and to limit any springback. Continuous cooling can be achieved by passing the moving fibre metal laminate material through a set of cooled cooperating pressure loaded rolls. Further cooling can be achieved by applying air cooling or forced air cooling to the moving fibre metal laminate material. Alternatively the laminate material can be continuously cooled under pressure by passing it through a continuous press provided with a twin band unit formed by a pair of revolving endless belts in which the belts are cooled.

The width of the produced fibre metal laminate material is limited to the width of the aluminium sheet material used. However, it is possible to manufacture wider fibre metal laminate materials by continuously unwinding at least two aluminium sheet materials each from a coil and continuously joining by means of welding the at least two adjacent sheet materials together into a wider sheet material. The wider sheet material can be coiled again and used as a starting material for the method according to this invention of manufacturing a fibre metal laminate material. Although several welding techniques can be applied to join two adjacent sheet materials, preferred welding techniques are laser beam welding and friction stir welding.

In an embodiment of the invention the cooled fibre metal laminate material can be subsequently formed at a temperature in the range of about 270°C to about 400°C to impose a curvature on the fibre metal laminate material. More preferably the forming operation is by means of creep forming in the range of about 270°C to about 350°C, more preferably in a range of 300°C to 350°C, for example at about 320°C or at about 325°C, to impose a curvature on the fibre metal laminate material.

Due to choice of specific polymer and of the aluminium alloy, in particular AIMgSc based alloys, the fibre metal laminate material can be further formed at elevated temperature. By heating the fibre metal laminate material up to the creep forming temperature of the AIMgSc alloy the laminate material can be formed. For the (creep) forming similar dies as used for AIMgSc sheet material can be applied and whereby there is even less springback for the fibre metal laminate material. Patent document EP-1216768 (Airbus) discloses for example a suitable a device and method for forming a metal sheet by means of creep forming.

The invention further relates to the use or to a method of use of the fibre metal laminate material obtained by the method according to this invention for forming at a temperature in the range of 270°C to 400°C to impose a curvature on the fibre metal laminate material. In a preferred embodiment it relates to forming by means of creep forming at a temperature in the range of 270°C to 350°C, more preferably in a range of 300°C to 350°C, for example at about 320°C or at about 325°C, to impose a curvature on the fibre metal laminate material.

DESCRIPTION OF THE DRAWING.

The invention shall also be described with reference to the appended drawing Fig. 1 showing a schematic representation of the method according to this invention.

A fibre metal laminate material (1 ) is being manufactured by continuously unwinding aluminium sheets (2, 3) for coils (4, 5) and being fed via support rolls (8, 9) into a pressure unit formed by two pairs of co-operating pressure rolls (14a, 14b, 15a, 15b). Simultaneously at ambient temperature a sheet (6) of prepreg material is continuously unwound from a coil (7) or a roll and also fed via support rolls (10, 1 1 ) into the pressure unit and whereby the sheet (6) of prepreg material is positioned between two aluminium sheets (2, 3). In this embodiment both the aluminium sheets (2, 3) and the sheet (6) of prepreg material are being heated while being continuously moved through a heating room (12) towards the pressure unit. In the heating room (12) additional heating means (not shown) can be used to bring the sheet of prepreg material in a controlled manner to a desired temperature, for example by means of infrared heating or convection heating. Next, in the pressure unit the aluminium sheets (2, 3) and the sheet (6) of prepreg material are firmly bonded together while moving through the pressure unit to form a fibre metal laminate material (1 ), and whereby preferably the applied pressure is controlled such that the elongation imparted to the laminate in its entirety by the pressing operation is not more than the elastic elongation of the metal sheets such that the aluminium sheets being subjected to substantially no plastic deformation during pressing process. If desired, the applied pressure onto the moving fibre metal laminate material (1 ) may gradually increase while it is moving through the pressure unit, meaning that at the beginning a lower pressure is applied and gradually increased to a somewhat higher pressure level and then kept substantially constant at that level. The bonding using the pressure unit is carried out at elevated temperature, for example by locating the pressure unit in a heated room (13), although alternative ways of heating have been set out in this description. In the pressure unit side dams (not shown) can be used on either side of the moving fibre metal laminate material to avoid loss of polymer material being squeezed out of the fibre metal laminate material under pressure. Such side dams have a thickness slightly less than the expected laminate thickness and can be made of materials like for example stainless steel or aluminium. Upon leaving the pressure unit (14a, 14b, 15a, 15b) the fibre metal laminate material is cooled, preferably under pressure using for example multiple pairs of pressure rollers (16a, 16b, 17a, 17b, 18a, 18b). The pressure rollers can be cooled and can be supplemented by additional cooling means like for example applying forced air cooling to the continuously moving fibre metal laminate material. The cooled fibre metal laminate material can be cut-to-length using a cutter (19) or coiled using a coiler device (not shown).

It will be immediately evident for the skilled person that by continuously unwinding a next aluminium sheet material and a next sheet of prepreg material a fibre metal laminate material can be manufactured having additional layers, for example two layers of prepreg material interposed between three layers of aluminium sheet material.

The invention is not limited to the embodiments described before, which may be varied widely within the scope of the invention as defined by the appending claims.

Claims

1 . A method of manufacturing a fibre metal laminate material (1 ), the fibre metal laminate material has two external faces and comprising:

N aluminium sheet layers (2,3), said N aluminium sheet layers being the same or different, and

N-1 polymer layers (6) alternating in said laminate material with said aluminium sheet layers (2,3), wherein N is equal to at least 2, and wherein each of said polymer layers (6) comprises high strength fibres,

the method comprising the steps of:

(a) unwinding in a continuous process from coils (4,5) at least two aluminium sheets (2,3) and feeding these to a pressure unit (14a, 14b, 15a, 15b);

(b) unwinding from coil(s) (7) sheet(s) of prepreg-material (6) comprising of high strength fibres embedded in a polymer for forming the polymer layer(s);

(c) feeding of the sheet of prepreg-material (6) between two aluminium sheets (2,3) to said pressure unit (14a, 14b, 15a, 15b);

(d) applying pressure to the aluminium sheets (2,3) and to the prepreg- material (6) interposed between the aluminium sheets (2,3) to form a fibre metal laminate material (1 ) and is performed at a temperature in the range of 150°C to 400°C;

(e) cooling of the fibre metal laminate material (1 ) on leaving the pressure unit;

(f) coiling or cutting-to-length of the cooled fibre metal laminate material (1 ); and wherein the polymer of the prepreg-material is a semicrystalline or paracrystalline thermoplastic polymer having a crystalline melting point T_m of greater than 170°C, and preferably greater than 270°C.

2. A method according to claim 1 , wherein the high strength fibre is a glass fibre or an aramid fibre.

3. A method according to claim 1 or 2, wherein the high strength fibre is a glass fibre.

4. A method according to any one of claims 1 to 3, wherein of the fibre metal laminate material N is at least 3, preferably N is 3 or 4.

5. A method according to any one of claims 1 to 4, wherein at least one of the two external faces of said fibre metal laminate comprises an aluminium non- heat treatable aluminium alloy sheet, preferably an AA5000-series aluminium alloy.

6. A method according to any one of claims 1 to 5, wherein all aluminium sheet layers of said fibre metal laminate material are made of an Al-Mg alloy having 3% to 8% Mg and 0.02% to 1 % Sc.

7. A method according to claim 6, wherein all aluminium sheet layers of said fibre metal laminate material are made of an Al-Mg alloy comprising 3% to 8% Mg, 0.02% to 1 % Sc, 0.2% to 1 % Mn, and up to 1 %of at least one element forming dispersoids selected from the group consisting of Zr, Cr, Hf, La, Ti, Ce, Nd, Eu, Gd, Tb, Dy, Ho, Er, Y, and Yb.

8. A method according to any one of claims 1 to 7, wherein each aluminium sheet layer of said fibre metal laminate material is made of AA5024 or AA5028.

9. A method according to any one of claims 1 to 8, wherein each aluminium sheet layer has been pre-treated by means of anodization.

10. A method according to any one of claims 1 to 9, wherein each aluminium sheet layer of said fibre metal laminate material has a thickness in the range of 0.1 to 1 .5 mm, and preferably in the range of 0.3 to 0.8 mm.

1 1 . A method according to any one of claims 1 to 10, wherein the polymer of the prepreg-material is polyetheretherketone (PEEK).

12. A method according to any one of claims 1 to 10, wherein the polymer of the prepreg-material is polyphenylene sulphide (PPS).

13. A method according to any one of claims 1 to 10, wherein the polymer of the prepreg-material is polyetherketoneketone (PEKK).

14. A method according to any one of claims 1 to 13, wherein each polymer based layer (6) comprises S2-type glass fibres.

15. A method according to any one of claims 1 to 14, wherein the applied pressure during step (d) is not exceeding 30 bar, and is preferably in a range of 5 to 20 bar.

16. A method according to any one of claims 1 to 15, wherein at least the prepreg- material (6) has been heated to a temperature in a range of 150°C to 300°C, and preferably of 150°C to 250°C, prior to being fed into said pressure unit.

17. A method according to any one of claims 1 to 16, wherein the fibre metal laminate material on leaving said pressure unit is cooled to ambient temperature, and is preferably cooled to ambient temperature under pressure.

18. A method according to any one of claims 1 to 17, wherein the cooled fibre metal laminate material is subsequently formed at a temperature in the range of 270°C to 400°C to impose a curvature on the fibre metal laminate material, and preferably is subsequently formed by means of creep forming at a temperature in the range of 270°C to 350°C.

19. Use of a fibre metal laminate material obtained by the method according to any one of claims 1 to 17, for forming at a temperature in the range of 270°C to 400°C to impose a curvature on the fibre metal laminate material.

20. Use of a fibre metal laminate material obtained by the method according to any one of claims 1 to 17, for forming by means of creep forming at a temperature in the range of 270°C to 350°C, more preferably in the range of 300°C to 350°C, to impose a curvature on the fibre metal laminate material.