Blade for an aircraft rotor and manufacturing method and device thereof

Abstract

The present invention concerns a method for manufacturing a blade (1) of a rotor comprising the steps of: arranging a central structure (2) comprising a core structure; laminating at least one layer of composite material (3) onto the central structure (2), thereby obtaining a coated central structure (5); arranging a mould (13) having a first region (14) and a second region (15); laminating at least one layer of said composite material (3) onto the first region (14) of the mould (13), thereby obtaining a first skin (18); placing the coated central structure (5) in the mould ( 13 ), so that the coated central structure (5) lies on the first skin (18); laminating at least one layer of composite material (3) onto the assembly defined by the first region ((1144)) of the mould (13), by the first skin (18) and by the coated central structure (5), thereby obtaining a second skin (19), and so that the first skin (18) and the second skin (19) wrap the coated central structure (5); closing the mould (13) so as to define a cavity (20); injecting thermosetting resin into the closed mould (13) so as to occupy said cavity (20) and lap the first skin (18) and the second skin (19); and applying a uniform hydrostatic pressure on the first skin (18) and on the second skin (19) by injection of said resin.

Description

[0001] "BLADE FOR AN AIRCRAFT ROTOR AND RELATED MANUFACTURING METHOD

[0002] AND DEVICE"

[0003] Cross-Reference to Related Applications

[0004] This Patent Application claims priority from Italian Patent Application No . 102024000021034 filed on September 20 , 2024 , the entire disclosure of which is incorporated herein by reference

[0005] Technical Field

[0006] The present invention concerns a blade for an aircraft rotor and a relative method and device for manufacturing said blade .

[0007] Prior Art

[0008] Blades for aircraft rotors made of composite materials are known . In the present description and in the claims , the expression "composite material" is used to indicate non-metallic materials obtained as the combination of a thermosetting resin matrix with a phase dispersed in the matrix and represented by fibre reinforcements , for example glass fibres or carbon fibres or graphite fibres ; in other words , the expression "composite material" is relative to composite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix .

[0009] The above-mentioned blades are traditionally made by forming in successive steps a primary structure consisting of several components made of composite material j oined together by means of adhesive substances . Said components can consist of structural elements or filler elements , namely elements having very modest mechanical performance : in the first case , they are components obtained by depositing one or more sheets preimpregnated with resin and comprising continuous fibres ( long fibres ) organi zed in fabrics , for example carbon or glass fibres ; in the second case , the fibres are of discontinuous type ( short fibres ) . The di f ferent components mentioned above are produced independently via respective curing steps and then j oined together by means of adhesive substances to form the primary structure .

[0010] In particular, each component of the primary structure is cured and subsequently glued to another component , for example to a non-cured component , obtaining an assembly defined by the cured component and by the non-cured component . At this point , the assembly is re-cured, namely both the previously cured component and the component not yet cured undergo the curing process ( and are therefore polymerized) ; this process is repeated until the primary structure is formed and is known as co-bonding process .

[0011] The structure thus obtained is externally coated with further layers of composite material , usually glass fibre sheets pre-impregnated with resin . The coating with these further layers forms the so-called outer skin of the blade .

[0012] A further example of a method for manufacturing a blade made of composite material is known from the document WO2023 / 203293 Al .

[0013] A blade produced according to the process described above , while presenting numerous advantages ( for example , low defect rate , high repeatability of physical-mechanical performance ) is not free from drawbacks , some of which are highlighted below .

[0014] Firstly, the high number of curing steps required to form the primary structure extends the blade production time , entailing a relative increase in the production costs thereof .

[0015] Furthermore , the execution of numerous curing processes comprising pieces already cured and pieces not yet cured can result in non-optimal surface characteristics in the j oining area between said pieces . It is therefore necessary to carry out a surface finishing operation on the final surface of the blade in order to remove any defects that could entail , for example , an increase in fuel consumption or a reduction in expected aerodynamic performances . Said surface finishing operation therefore results in increased production times and costs .

[0016] In addition to the above , the co-bonding process could entail a deterioration in the chemical and / or physical properties of the resin matrix impregnating the fibres of the components cured several times .

[0017] The need is therefore felt in the sector to improve the manufacturing process of a blade for an aircraft rotor made of composite material .

[0018] The obj ect of the present invention is to meet the above need, preferably in an optimi zed and inexpensive manner .

[0019] Summary of the Invention

[0020] According to the invention, this obj ect is achieved by a method for manufacturing a blade of an aircraft rotor as claimed in claim 1 .

[0021] A further obj ect of the present invention is to provide a device for manufacturing a blade of an aircraft rotor as claimed in claim 15 .

[0022] A further obj ect of the present invention is to provide a blade for an aircraft rotor, as claimed in claim 16 .

[0023] The dependent claims illustrate particular embodiments of the invention .

[0024] Brief Description of the Drawings

[0025] For a better understanding of the present invention, a preferred embodiment thereof is described below, by way of non- limiting example and with reference to the attached drawings wherein :

[0026] • figure 1 illustrates a perspective view of a blade produced according to the manufacturing method of the present invention;

[0027] • figure 2 illustrates a perspective exploded view of a preferred embodiment of the blade of figure 1 ;

[0028] • figures 3A-3G illustrate schematically a perspective view of successive steps of the manufacturing method of the blade of figure 2 according to the present invention;

[0029] • figure 3H is a perspective view, partially in section and on an enlarged scale , of a mould in a closed configuration used in the method according to the present invention;

[0030] • figures 4A and 4B are section views , on an enlarged scale and with parts removed for clarity, of a detail of the mould of figure 3H, during two di f ferent operating conditions ;

[0031] • figure 5A illustrates schematically a forming tool according to an embodiment of the manufacturing method according to the present invention; and

[0032] • figure 5B illustrates schematically the forming tool of figure 5A during use .

[0033] Detailed Disclosure of the Invention

[0034] The expression "composite material" which will be used below relates , in the present invention and in the appended claims , to composite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix, without loss of generality .

[0035] Preferably, the thermosetting resin matrix comprises a toughened thermosetting epoxy resin impregnating fibres , in particular carbon fibres . Even more preferably, the resin has a high glass transition temperature , for example between 135 ° and 170 ° .

[0036] Figure 1 illustrates a blade 1 for an aircraft rotor produced according to the manuf cturing method of the present invention .

[0037] The term "aircraft" is relative to any type of device or vehicle designed to fly in the earth' s atmosphere , for example an aeroplane , a helicopter, a glider or an airship .

[0038] The blade 1 comprises a central structure 2 comprising a core structure .

[0039] Preferably, the core structure constitutes entirely the central structure 2 .

[0040] Conveniently, the core structure comprises a foam core .

[0041] Preferably, the foam core constitutes the core structure in its entirety, namely the central structure 2 in its entirety .

[0042] Conveniently, the foam core includes polymethylmethacrylimide ( PMI ) -based rigid material , particular it comprises a closed-cell foam .

[0043] In detail , the closed-cell foam preferably has a thermal stability up to very high temperatures , for example up to a temperature of 210 ° .

[0044] In further detail , the closed-cell foam is a rigid foam .

[0045] According to an alternative embodiment not illustrated, the core structure comprises a core made of composite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix .

[0046] In particular, the core structure comprises a hollow structure . Even more speci fically, the hollow structure entirely constitutes the core structure , namely the central structure 2 .

[0047] In particular, the core made of composite material is produced by lamination of at least one layer of composite material onto a support element ( for example of the bladder type ) .

[0048] According to a first embodiment , the core made of composite material is not pre-cured and comprises pre-impregnated composite material including dispersed fibres with a pre-defined orientation in a thermosetting resin matrix .

[0049] According to an alternative embodiment , the core made of composite material is pre-cured, thereby obtaining a core made of pre-cured composite material , and comprises composite material including dispersed fibres with a predefined orientation in a resin matrix .

[0050] The blade 1 comprises at least one layer of pre-impregnated composite material 3 laminated onto an outer surface 4 of the central structure 2 so as to define a coated central structure 5 .

[0051] Preferably, the layer of composite material 3 is laminated onto the entire outer surface 4 , completely wrapping the central structure 2 .

[0052] The blade 1 further comprises a skin comprising at least one further layer of pre-impregnated composite material 3 wrapping the coated central structure 5 .

[0053] Preferably, the blade 1 further comprises at least one auxiliary structure 6 comprising a further foam core .

[0054] In particular, the auxiliary structure 6 comprises a first portion 7 and / or a second portion 8 , wherein at least one of the first portion 7 and the second portion 8 is arranged adj acent to the coated central structure 5 . According to a possible embodiment , the auxiliary structure 6 comprises the first portion 7 and the second portion 8 .

[0055] According to the embodiment illustrated above , at least one of the first portion 7 and the second portion 8 comprises a further foam core .

[0056] Conveniently, both the first portion 7 and the second portion 8 each comprise a respective further foam core . In particular, each further foam core constitutes respectively the first portion 7 and / or the second portion 8 entirely .

[0057] Even more speci fically, the further foam core comprised in each portion 7 , 8 includes a polymethylmethacrylimide ( PMI ) - based rigid material , in detail comprises a closed-cell foam .

[0058] In particular, the closed-cell foam has a thermal stability up to very high temperatures , for example up to a temperature of 210 ° . In further detail , the closed-cell foam is a rigid foam .

[0059] In detail , the first portion 7 and the second portion 8 define respectively a leading edge 7 and a trailing edge 8 of the blade 1 .

[0060] Therefore , in accordance with the above , the auxiliary structure 6 defines a leading edge 7 and / or a trailing edge 8 of the blade 1 .

[0061] In further detail , the leading edge 7 is a front part of the blade 1 which, during the movement , comes first into contact with the air, while the trailing edge 8 is a rear part of the blade 1 from which the air detaches after crossing the surface of the blade 1 .

[0062] Conveniently, the above-mentioned skin wraps the coated central structure 5 and the auxiliary structure 6. In particular, the above-mentioned skin wraps the coated central structure 5 , the leading edge 7 and the trailing edge 8 of the blade 1 .

[0063] According to an alternative embodiment , the auxiliary structure 6 comprises a further core made of compos ite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix . In particular, the auxiliary structure 6 is arranged adj acent to the coated central structure 5 .

[0064] According to the embodiment described above , at least one of the first portion 7 and the second portion 8 comprises a further core made of composite material .

[0065] Conveniently, both the first portion 7 and the second portion 8 each comprise a respective further core made of composite material . In particular, each further core made of composite material constitutes respectively the first portion 7 and / or the second portion 8 entirely .

[0066] Also in this embodiment , the above-mentioned skin wraps the coated central structure 5 and the auxiliary structure 6 .

[0067] In particular, the above-mentioned skin wraps the coated central structure 5 , the leading edge 7 and / or the trailing edge 8 of the blade 1 .

[0068] In the embodiment described above , the further core made of composite material of the auxiliary structure 6 is produced by lamination of at least one layer of composite material onto a support element ( for example of the bladder type ) .

[0069] According to a first embodiment , the further core made of composite material of the auxiliary structure 6 is not pre-cured and comprises pre-impregnated composite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix .

[0070] According to an alternative embodiment , the core made of composite material is pre-cured, thereby obtaining a core made of pre-cured composite material , and comprises impregnated composite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix .

[0071] It should be noted that figures 3H, 4A and 4B described below do not necessarily represent a real section of the blade 1 . In particular, figures 3H, 4A and 4B represent a schemati zation of a strati fication of the blade 1 .

[0072] Figures 3A-3G illustrate successive steps of a manufacturing method of the blade 1 according to a preferred embodiment of the present invention .

[0073] Figure 3A illustrates the central structure 2 comprising the above-mentioned core structure comprising the foam core .

[0074] In accordance with the above , the method according to the invention comprises the step of a ) arranging a central structure 2 comprising the core structure .

[0075] As illustrated in figure 3B, at least one layer of preimpregnated composite material 3 is laminated onto an outer surface 4 of the central structure 2 , in such a way as to thereby obtain the above-mentioned coated central structure 5 .

[0076] Therefore , the method according to the invention comprises the step b ) of laminating at least one layer of pre-impregnated composite material 3 including dispersed fibres with a predefined orientation in a thermosetting resin matrix onto an outer surface 4 of the central structure 2 , thereby obtaining a coated central structure 5 .

[0077] In particular, the central structure 2 is coated by at least two layers of pre-impregnated composite material 3 , arranged one above the other . Even more speci fically, the at least two layers of pre-impregnated composite material 3 are laminated onto the outer surface 4 of the central structure 2 and compacted together .

[0078] Therefore , preferably, in the method according to the present invention, step b ) of laminating at least one layer of pre-impregnated composite material 3 onto an outer surface 4 of the central structure 2 comprises the further steps of : bl ) laminating at least two layers of said composite material 3 onto the outer surface 4 of the central structure 2 ; and b2 ) compacting the at least two layers of composite material 3 together .

[0079] Preferably, the at least two layers of composite material 3 are compacted by means of a vacuum bag . In particular, the assembly defined by the central structure 2 and by the two layers of composite material 3 is arranged inside a vacuum bag and heated to a predetermined temperature so that , when the vacuum is applied inside the vacuum bag, the at least two layers of composite material 3 are compacted .

[0080] Conveniently, the assembly defined by the central structure 2 and by the two layers of composite material 3 arranged inside the vacuum bag is heated, prior to application of the vacuum, to a temperature equal to fi fty or eighty degrees Celsius ( ° C ) for a predefined time interval , for example for thirty minutes .

[0081] In particular, at least one thermocouple is inserted inside the vacuum bag, configured to measure the temperature inside the vacuum bag throughout the compaction step of the at least two layers of composite material 3 .

[0082] Preferably, the compaction of the at least two layers of composite material 3 by means of vacuum bag involves the application of an airpad which intensi fies the pressure applied and improves the final surface finish of the compaction of the at least two layers of composite material 3 .

[0083] Conveniently, in accordance with the above , the step b2 ) of compacting the at least two layers of pre-impregnated composite material 3 in the method according to the present invention comprises :

[0084] - placing the assembly defined by the central structure 2 and by the two layers of composite material 3 inside a vacuum bag;

[0085] - heating the assembly defined by the central structure 2 and by the two layers of composite material 3 to a predetermined temperature ;

[0086] - applying the vacuum inside the vacuum bag, in such a way as to compact the layers of composite material 3 .

[0087] Alternatively, the at least two layers of pre-impregnated composite material 3 are compacted by means of a forming tool (not illustrated) .

[0088] In particular, the forming tool is arranged in such a way that a forming surface applies a pressure against the at least two layers of composite material 3 .

[0089] In particular, the forming surface is internally complementary to an outer surface of the assembly defined by the central structure 2 and by the at least two layers of composite material 3 .

[0090] In detail , the assembly defined by the central structure 2 and by the two layers of composite material 3 is placed in contact with the forming surface so that the at least two layers of composite material 3 are compacted by means of the pressure applied by the forming surface on the assembly .

[0091] Preferably, in accordance with the above , the step b2 ) of compacting at least two layers of composite material 3 in the method according to the present invention comprises :

[0092] - arranging a first forming tool having a first forming surface ;

[0093] - placing the assembly defined by the central structure 2 and by the two layers of composite material 3 in contact with the first forming surface ; and

[0094] - compacting the at least two layers of composite material 3 by means of a pressure applied by the first forming surface against the assembly defined by the central structure 2 and by the two layers of composite material 3 .

[0095] According to a possible embodiment , the central structure 2 comprises a root portion 11 intended to be connected to a hub ( known per se and not illustrated) of a rotor, and a main portion 12 extending from the root portion 11 mainly in a longitudinal direction A. Preferably, the root portion 11 has a f rustoconical shape .

[0096] Preferably, i f the central structure 2 comprises a foam core , the method further comprises the step, prior to the lamination step b ) , of arranging an adhesive material , preferably an adhesive film, at least partially on the central structure 2 , in particular on the core structure .

[0097] According to an alternative embodiment , the adhesive material comprises an adhesive paste .

[0098] According to a possible embodiment , the adhesive material is applied on the entire outer surface of the core structure . Conveniently, the adhesive material is applied at least in the area of at least one of the points at which there is a reduction in thickness of the foam core of the foam structure .

[0099] In other words , the adhesive material is interposed between the foam core and the layers of composite material 3 , and therefore forms , in said case , an integral part of the coated central structure 5 .

[0100] In detail , the above-mentioned adhesive material has a high glass transition temperature , high toughness and resistance to humidity .

[0101] In further detail , the adhesive material comprises toughened epoxy resin .

[0102] In particular, the adhesive material interposed between the central structure 2 , even more speci fically the core structure , and the layers of pre-impregnated composite material 3 prevents the resin from positioning itsel f inside the cells of the core structure of the central structure 2 , compromising lamination of the layers of composite material 3 onto said core structure of the central structure 2 . In this way, the final quality of the laminated component is signi ficantly improved .

[0103] According to an alternative embodiment , i f the core structure of the central structure 2 comprises the above- mentioned core made of pre-cured composite material , the adhesive material is arranged at least partially, preferably entirely, on all the outer surface of the core structure made of pre-cured composite material , in such a way as to favour adhesion of the core structure of the central structure 2 with at least one layer of composite material , the latter preferably pre-impregnated, laminated on the core structure , namely on the central structure , so as to improve the final quality of the assembly obtained . Advantageously, at least one layer of pre-impregnated composite material 3 is laminated onto at least one of the root portion 11 and the main portion 12 . In particular, at least one layer of composite material 3 is laminated onto the root portion 11 and at least one layer of composite material 3 is laminated onto the main portion 12 .

[0104] In detail , successive layers of composite material 3 are laminated onto the respective root portion 11 and onto the respective main portion 12 with di f ferent angles ; for example , i f the first layer of composite material 3 is laminated in a direction parallel to the longitudinal direction A, the second layer of composite material 3 is laminated in a direction transverse to the longitudinal direction A, the third layer of composite material 3 in a di f ferent direction from the layer of composite material 3 previously laminated and so on .

[0105] Subsequently, other layers of composite material 3 are laminated and partially overlapped on at least one of the root portion 11 and the main portion 12 , in such a way that the j oints between the various laminated layers of composite material 3 do not locally alter the thickness due to the coating of these portions 11 , 12 via the layers of composite material 3 , so as not to generate any wrinkles , thereby obtaining a uni form laminated surface .

[0106] After lamination of the at least one layer of preimpregnated composite material 3 , in particular of the various layers of composite material 3 onto the above-mentioned outer surface 4 of the central structure 2 , a mould 13 is arranged having a first region 14 and a second region 15 delimiting between them a space adapted to accommodate at least one portion of the coated central structure 5 .

[0107] In accordance with the above , the method according to the invention comprises the step of c ) arranging a mould 13 having a first region 14 and a second region 15 delimiting between them a space adapted to accommodate at least one portion of the coated central structure 5 .

[0108] Optionally, the first region 14 and the second region 15 delimit between them a space adapted to accommodate at least one portion of the coated central structure 5 and the auxiliary structure 6 . Terms such as "upper" , " lower" or similar that will be used below are relative to a reference system wherein the vertical direction is defined by the direction of the force of gravity, without loss of generality .

[0109] In particular, the first region 14 is a lower part of the above-mentioned mould 13 , while the second region 15 is an upper part of the mould 13 .

[0110] Preferably, the mould 13 comprises a third region 16 , in particular an intermediate region, interposed, in use , between the first region 14 and the second region 15 .

[0111] According to a preferred embodiment described below, the coated central structure 5 is accommodated entirely in the above-mentioned mould 13 , in particular in the space delimited by the first region 14 and by the second region 15 .

[0112] Therefore , the regions 14 , 15 , 16 are configured to be closed, in use , around the entire coated central structure 5 .

[0113] Preferably, the regions 14 , 15 , 16 are configured to be closed, in use , around the entire coated central structure 5 and the auxiliary structure 6 .

[0114] Optionally, the first region 14 comprises a shaped portion defining a compartment 17 configured to receive and support only the coated central structure 5 . According to the embodiment illustrated in figure 3C, the first region 14 comprises a shaped portion defining a compartment 17 configured to receive and support the coated central structure 5 and the auxiliary structure 6.

[0115] Before arranging the coated central structure 5 on the first region 14 of the mould 13 , at least one layer of pre-impregnated composite material 3 is laminated onto the first region 14 , in particular in the compartment 17 , in such a way as to obtain a first skin 18 made of composite material .

[0116] In accordance with the above , the method according to the invention comprises the step of d) laminating at least one layer of pre-impregnated composite material 3 onto the first region 14 of the mould 13 , thereby obtaining a first skin 18 made of composite material .

[0117] Preferably, to obtain the first skin 18 made of composite material , at least two layers of pre-impregnated composite material 3 are arranged on the first region 14 of the mould 13 and subsequently compacted together . In particular, the assembly defined by the f irst region 14 of the mould 13 and by the two layers of composite material 3 is arranged inside a vacuum bag and heated to a predetermined temperature , for example fi fty or eighty degrees Celsius ( ° C ) , in detail for a given time period, for example for thirty minutes ; at this point , the vacuum is applied inside the vacuum bag in such a way as to compact the at least two layers of composite material 3 .

[0118] Alternatively, to obtain the first skin 18 made of composite material , the lamination of at least two layers of preimpregnated composite material 3 onto the first region 14 of the mould 13 comprises compacting the two layers of composite material 3 via the use of a further forming tool (not illustrated) , the latter comprising a further forming surface (not illustrated) . In particular, the two layers of composite material 3 are compacted by pressing the further forming surface against the two layers of composite material 3 .

[0119] Therefore , preferably, in the method according to the present invention, step d) of laminating at least one layer of pre-impregnated composite material 3 onto the first region 14 of the mould 13 comprises : laminating at least two layers of pre-impregnated composite material 3 including dispersed fibres with a predefined orientation in a thermosetting resin matrix on the first region 14 of the mould 13 ;

[0120] - placing the assembly defined by the first region of the mould 14 and by the two layers of composite material 3 inside a vacuum bag;

[0121] - heating the assembly defined by the first region of the mould 14 and by the two layers of composite material 3 to a predetermined temperature ;

[0122] - applying the vacuum inside the vacuum bag, so as to compact the two layers of composite material 3 ; or in which step d) of laminating at least one layer of preimpregnated composite material 3 onto the first region 14 of the mould 13 comprises :

[0123] - laminating at least two layers of pre-impregnated composite material 3 including dispersed fibres with a predefined orientation in a thermosetting resin matrix on the first region of the mould 14 ;

[0124] - arranging a second forming tool having a second forming surface ;

[0125] - placing the assembly defined by the first region of the mould 14 and by the at least two layers of composite material 3 in contact with the second forming surface ;

[0126] - compacting the two layers of composite material 3 by pressing the second forming surface against the assembly defined by the first region of the mould 14 and by the two layers of composite material 3 . As can be seen in particular in figures 3D-3E , the first skin 18 defines a lower portion of the above-mentioned skin which wraps the above-mentioned coated central structure 5.

[0127] At this point , the coated central structure 5 is arranged on the first region 14 of the mould 13 , in such a way that the coated central structure 5 lies on the first skin 18 .

[0128] Therefore , the method according to the invention comprises step e ) of arranging the at least one portion of the coated central structure 5 on the first region 14 of the mould 13 , in such a way that the portion of the coated central structure 5 lies on the first skin 18 .

[0129] Subsequently, at least one layer of pre-impregnated composite material 3 is laminated onto the assembly defined by the first region 14 of the mould 13 , by the first skin 18 and by the coated central structure 5 , thereby obtaining a second skin 19 made of composite material , and in such a way that the first skin 18 and the second skin 19 wrap the coated central structure 5 .

[0130] In particular, the first skin 18 and the second skin 19 each comprise at least one layer of pre-impregnated composite material 3 , even more speci fically at least two layers of composite material 3 . In detail , the second skin 19 is partially overlapped on the first skin 18 . In particular, the first skin 18 and the second skin 19 are positioned around the coated central structure 5 in such a way that they are partially overlapped on each other in the area of a j oining zone .

[0131] More speci fically :

[0132] - a lateral edge portion of the first skin 18 is folded and wrapped on the coated central structure 5 ;

[0133] - a lateral edge portion of the second skin 19 is folded and wrapped on the edge portion of the first skin 18 and, therefore , on the coated central structure 5 (not illustrated) .

[0134] In this way, the assembly is obtained consisting of the coated central structure 5 and the first skin 18 and second skin 19 partially overlapped in the area of their lateral edge portions .

[0135] In accordance with the above , the method according to the present invention comprises the step of f ) laminating at least one layer of pre-impregnated composite material 3 onto the assembly defined by the first region 14 of the mould 13 , by the first skin 18 and by the portion of the coated central structure 5 , thereby obtaining a second skin 19 made of composite material , and in such a way that the first s kin 18 and the second skin 19 wrap the portion of the coated central structure 5 .

[0136] In particular, the second skin 19 defines an upper portion of the above-mentioned skin which wraps the above-mentioned coated central structure 5 .

[0137] According to the embodiment described above , at least two layers of pre-impregnated composite material 3 are laminated onto the assembly defined by the first region 14 of the mould 13 , the first skin 18 and the coated central structure 5 . In particular, the lamination of the at least two layers of preimpregnated composite material comprises compacting of the at least two layers of composite material 3 . In detail , the assembly defined by the first skin 18 , the coated central structure 5 and the at least two layers of composite material 3 is placed inside a vacuum bag and heated to a predetermined temperature , for example fi fty or eighty degrees Celsius ( ° C ) , in particular for a given period of time , for example thirty minutes .

[0138] At this point , the vacuum is applied inside the vacuum bag so as to compact the at least two layers of composite material 3 .

[0139] Preferably, also the first region 14 of the mould 13 forms part of the assembly defined by the first skin 18 , by the coated central structure 5 and by the at least two layers of composite material 3 , so that also the first region 14 of the mould 13 is inserted inside the vacuum bag .

[0140] Alternatively, the lamination of the at least two layers of pre-impregnated composite material 3 onto the as sembly defined by the first skin 18 and by the coated central structure 5 comprises compacting the two layers of composite material 3 via the use of a further forming tool , in particular by pressing a further forming surface against the assembly defined by the first skin 18 , by the coated central structure 5 and by the two layers of composite material 3 .

[0141] In particular, said further forming surface is internally complementary to an outer surface of the assembly defined by the first skin 18 , by the coated central structure 5 and by the two layers of composite material 3 .

[0142] According to a possible embodiment illustrated in figure 3F, also the auxiliary structure 6 is arranged on the first skin 18 , in particular adj acent to the coated central structure 5 .

[0143] Conveniently, in accordance with the above , the method according to the present invention comprises the step ) of arranging, after the steps d) of laminating and e ) of arranging and prior to step f ) of laminating, at least one auxiliary structure 6 comprising a foam core on the first region 14 of the mould 13 , so that said at least one auxiliary structure 6 is arranged on the first skin 18 , in a position adj acent to the portion of the coated central structure 5 . In detail , at least one layer of pre-impregnated composite material 3 is laminated onto the assembly defined by the first region 14 of the mould 13 , by the first skin 18 , by the coated central structure 5 and by the auxiliary structure 6 . In further detail , the second skin 19 is arranged also on the auxiliary structure 6 .

[0144] Preferably, in accordance with the method according to the present invention, the lamination step f ) compri ses laminating at least one layer of said pre-impregnated composite material 3 onto the assembly defined by the first region 14 of the mould 13 , by the first skin 18 , by the portion of the coated central structure 5 and by the auxiliary structure 6 , so that the first skin 18 and the second skin 19 wrap the portion of the coated central structure 5 and the auxiliary structure 6 . In particular, the first skin 18 and the second skin 19 each comprise at least one layer of pre-impregnated composite material 3 , even more speci fically at least two layers of composite material 3 . As illustrated in figures 4A and 4B, the second skin 19 is partially overlapped on the first skin 18 . In particular, the first skin 18 and the second skin 19 are positioned around the coated central structure 5 and the auxiliary structure 6 so that they partially overlap each other in the area of a j oining zone 31 .

[0145] More speci fically :

[0146] - a lateral edge portion of the first skin 18 is folded and wrapped on the coated central structure 5 and on the auxiliary structure 6 ( figure 3F) ;

[0147] - a lateral edge portion of the second skin 19 is folded and wrapped on the edge portion of the first skin 18 and, therefore , on the coated central structure 5 and on the auxiliary structure 6 (not illustrated) .

[0148] In this way, the assembly illustrated in figure 3G is obtained, consisting of the coated central structure 5, the auxiliary structure 6 and the first skin 18 and second skin 19 partially overlapped in the area of their lateral edge portions , namely in the area of the j oining zone 31 . Conveniently, i f the auxiliary structure 6 comprises a foam core , the arrangement step j ) comprises the step j l ) of arranging an adhesive material , preferably an adhesive film, at least partially on the coated central structure 5 .

[0149] According to an alternative embodiment , the adhesive material comprises an adhesive paste .

[0150] According to a possible embodiment , the adhesive material is arranged throughout the outer surface of the coated central structure 5 .

[0151] According to a possible embodiment , the adhesive material is arranged at least partly, or entirely, on the auxiliary structure 6 .

[0152] Conveniently, the adhesive material is arranged in the area of at least one of the j oining points between the coated central structure 5 and the auxiliary structure 6 , in particular where there is a reduction in thickness of the foam core of the auxiliary structure 6 .

[0153] In other words , the adhesive material is interposed between the foam core of the auxiliary structure 6 (namely between each of the foam cores of the first portion 7 and second portion 8 ) and the coated central structure 5 .

[0154] In detail , the above-mentioned adhesive material has a high glass transition temperature , high toughness and resistance to humidity .

[0155] In further detail , the adhesive material comprises a toughened epoxy resin .

[0156] In particular, the adhesive material interposed between the coated central structure 5 and the foam core of the auxiliary structure 6 prevents the resin positioning itsel f inside the cells of the core structure , for example in the area of the points where there is a reduction in thickness of the foam core of the auxiliary structure 6 , and compromising the adhesion between the coated central structure 5 and the auxiliary structure 6 .

[0157] In this way, the final quality of the laminated component is signi ficantly improved .

[0158] For example , the adhesive material could be interposed in the area of an edge of the foam core of the auxiliary structure 6 .

[0159] According to an alternative embodiment , the method according to the present invention further comprises the step of : arranging, after the laminating step d) and arranging step e ) and prior to the laminating step f ) , at least one auxiliary structure 6 comprising a core made of composite material including dispersed fibres with a predefined orientation in a thermosetting resin matrix on the first region 14 of the mould 13 , so that said at least one auxiliary structure 6 is arranged on the first skin 18 , in a position adj acent to the portion of the coated central structure 5 ; and wherein the lamination step f ) comprises laminating at least one layer of said pre-impregnated composite material 3 onto the assembly defined by the first region 14 of the mould 13 , by the first skin 18 , by said portion of the coated central structure 5 and by said auxiliary structure 6 , so that the first skin 18 and the second skin 19 wrap the portion of the coated central structure 5 and the auxiliary structure 6.

[0160] According to a possible embodiment , i f the auxiliary structure 6 comprises one or more cores made of pre-cured composite material , the adhesive material is arranged at least partially, preferably entirely, on the outer surface of the core structure made of pre-cured composite material of the auxiliary structure 6 , in such a way as to facilitate adhesion of the core structure of the auxiliary structure 6 with the coated central structure 5 , so as to improve the final quality of the assembly obtained .

[0161] In the light of the above , the blade 1 may comprise :

[0162] - a central structure 2 comprising a foam core structure and an auxiliary structure 6 comprising a foam core or core made of composite material ( alternatively pre-impregnated or precured) ; or

[0163] - a central structure 2 comprising a core structure made of composite material ( alternatively pre-impregnated or precured) and an auxiliary structure 6 comprising a foam core or core made of composite material .

[0164] In particular, after laminating at least two layers of preimpregnated composite material 3 onto the assembly defined by the first skin 18 , by the coated central structure 5 and by the auxiliary structure 6 , the assembly defined by the first skin 18 , by the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 is placed inside a vacuum bag and heated to a predetermined temperature , for example fi fty or eighty degrees Celsius ( ° C ) , in particular for a given time period, for example thirty minutes . At this point , the vacuum is applied inside the vacuum bag so as to compact the at least two layers of composite material 3 .

[0165] Preferably, in accordance with the above , the lamination step f ) in the method according to the present invention comprises : laminating at least two layers of pre-impregnated composite material 3 on the assembly defined by the first skin 18 , by said portion of the coated central structure 5 and by the auxiliary structure 6 ;

[0166] - placing the assembly defined by the first skin 18 , by the portion of the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 inside a vacuum bag; heating to a predetermined temperature the assembly defined by the first skin 18 , by the portion of the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 ; and

[0167] - applying the vacuum inside the vacuum bag, so as to compact the two layers of composite material 3 .

[0168] Conveniently, also the first region 14 of the mould 13 forms part of the assembly defined by the first skin 18 , by the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 , so that also the first region 14 of the mould 13 is inserted inside the vacuum bag .

[0169] Alternatively, in the embodiment illustrated in figures 5A and 5B, the lamination of at least two layers of pre-impregnated composite material 3 onto the assembly defined by the first skin 18 , by the coated central structure 5 and by the auxiliary structure 6 comprises compacting the two layers of preimpregnated composite material 3 via the use of a further forming tool 9 , in particular by pressing a further forming surface 10 against the assembly defined by the first skin 18 , by the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 .

[0170] Therefore , alternatively, in accordance with the above , in the method according to the present invention, the lamination step f ) comprises :

[0171] - laminating at least two layers of pre-impregnated composite material 3 onto the assembly defined by the first skin 18 , by the portion of the coated central structure 5 and by the auxiliary structure 6 ;

[0172] - arranging a third forming tool 9 having a third forming surface 10 ;

[0173] - placing the assembly defined by the first skin 18 , by the portion of the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 in contact with the third forming surface 10 ; and

[0174] - compacting the two layers of composite material 3 by pressing the third forming surface 10 against the assembly defined by the first skin 18 , by the portion of the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 .

[0175] In particular, the forming surface 10 is internally complementary to an outer surface of the assembly defined by the first skin 18 , by the portion of the coated central structure 5 , by the auxiliary structure 6 and by the two layers of composite material 3 .

[0176] At this point , the assembly is obtained composed of :

[0177] - coated central structure 5 ;

[0178] - first and second skin 18 , 19 ;

[0179] - preferably, auxiliary structure 6 ( and in particular first and second portion 7 , 8 ) ;

[0180] - preferably, adhesive material , said assembly defining the blade 1 .

[0181] At this point , the mould 13 is closed so as to define a cavity 20 between the second skin 19 previously laminated onto the coated central structure 5 and the second region 15 of the mould 13 , in particular between an upper surface 28 of the second skin 19 and a lower surface 27 of the second region 15 facing the upper surface 28 .

[0182] Therefore , the method according to the present invention comprises step g) of closing the mould 13 so as to define a cavity 20 between at least the second skin 19 previously laminated onto the portion of the coated central structure 5 and the second region 15 of the mould 13 .

[0183] Preferably, the mould 13 is closed in such a way as to define a cavity 20 between at least the second skin 19 previously laminated both on the coated central structure 5 and on the auxiliary structure 6 and the second region 15 of the mould 13 , in particular at least between the upper surface 28 of the second skin 19 and the lower surface 27 of the second region 15 facing the upper surface 28 .

[0184] More precisely, the second region 15 has a portion shaped in relief which traces and follows the profile of the outer surface 4 of the central structure 2 and of the compartment 17 , when the mould 13 is closed, namely when the regions 14 , 15 , 16 are clamped and j oined to each other .

[0185] Preferably, the shaped portion traces and follows the profile , in particular the upper profile , of the coated central structure 5 and the auxiliary structure 6 .

[0186] Conveniently, al so the first region 14 comprises a shaped portion which traces and follows the profile of the outer surface 4 of the central structure 2 .

[0187] Preferably, said shaped portion traces and follows the profile , in particular the lower profile , of the coated central structure 5 and the auxiliary structure 6 .

[0188] For the positioning, closing and clamping of the various regions 13 , 14 , 15 of the mould 13 , conventional means are used such as , for example , screws or bolts (not illustrated) .

[0189] Once the mould 13 is closed, a thermosetting resin is inj ected into the closed mould 13 through an inlet opening 22 of the mould 13 , so as to occupy the cavity 20 and lap (preferably completely) the first skin 18 and the second skin 19 , in particular so that a flow of resin 29 laps (preferably completely) the entire outer surface of the assembly defined by coated central structure 5 , first skin 18 and second skin 19 , and even more in particular also including the auxiliary structure 6 .

[0190] In other words , the inj ected resin occupies the cavity 20 and laps the entire outer surface of the blade 1 , as explained below .

[0191] Even more speci fically, the inj ected thermosetting resin applies a pressure throughout the outer surface of the coated central structure 5 , with interposition of the second skin 19 and the first skin 18 .

[0192] In the preferred embodiment illustrated, the inj ected thermosetting resin applies a pressure throughout the outer surface of the coated central structure 5 and the auxiliary structure 6 , with interposition of the second skin 19 and the first skin 18 , namely throughout the outer surface of the blade 1 . In further detail , due to the pressure applied by the inj ected thermosetting resin, the latter also laps the first skin 18 . In particular, the inj ected thermosetting resin "pushes" and moves the first skin 18 away from the lower region of the mould 14 . In this way, the cavity 20 is defined around the entire outer surface of the blade 1 (namely around the first skin 18 and the second skin 19 ) , and the inj ected thermosetting resin laps both the second skin 19 and the first skin 18 , hence the entire outer surface of the coated central structure 5 and / or the auxiliary structure 6 .

[0193] Preferably, the thermosetting resin inj ected into the closed mould 13 is a toughened thermosetting epoxy resin . Even more preferably, the resin has a glass transition temperature ranging from 135 ° to 170 ° .

[0194] Conveniently, the thermosetting resin is inj ected into the mould 13 by means of an inj ection pump ( known per se and not illustrated) .

[0195] In particular, the mould 13 comprises at least one inlet channel 21 arranged, namely obtained, in the second region 15 , in particular in a peripheral portion of the second region 15 , and configured to allow the passage of a fluid, in particular of the resin, inside the closed mould 13 .

[0196] Preferably, the mould 13 comprises a plurality of said inlet channels 21 , distributed around the compartment 17 and therefore around the blade 1 .

[0197] In further detail , each inlet channel 21 comprises an inlet opening 22 through which the resin, in use , flows into the inlet channel 21 and then into the cavity 20 .

[0198] In practice , in use , the resin flows from a tank (not illustrated) towards the inside of the mould 13 , via the inlet channels 21 ; from the latter, the resin flows into the cavity 20 .

[0199] Conveniently, the mould 13 further comprises an outlet channel 24 , arranged, namely obtained, in the second region 15 , in particular in a peripheral portion of the second region 15 and configured to allow the passage of fluid from the inside of the mould 13 towards the outside of the mould 13 .

[0200] More precisely, the outlet channel 24 is configured to allow outflow of the resin, previously inj ected, to the outside of the mould 13 , after passage of the same through the cavity 20 . In detail , as soon as the resin has occupied, in use , the entire cavity 20 , it is fed to the outlet channel 24 and flows towards the outside of the mould 13 through an outlet opening 26 of the outlet channel 24 .

[0201] In particular, the resin is fed to the outlet channel 24 after lapping the first skin 18 and the second skin 19 .

[0202] Therefore , preferably, the mould 13 comprises an outlet opening 26 fluidically connected to each inlet opening and, in use , to said cavity 20 .

[0203] According to a possible embodiment , the resin is inj ected by suction of the resin into the mould 13 by application of the vacuum inside the mould 13 by means of a vacuum source ( known per se and not illustrated) .

[0204] In particular, the vacuum source is configured to be fluidically connected, in use , with the outlet channel 24 and to apply the vacuum inside the mould 13 , appropriately sealed, in such a way as to cause a suction that draws the resin through the inlet channel 21 .

[0205] Application of the vacuum helps to facilitate flowing of the resin along its path inside the mould 13 and towards the outlet channel 24 .

[0206] Conveniently, the mould 13 comprises at least one seal , for example a sealing ring, to guarantee that the mould 13 is appropriately sealed . In further detail , a sealing ring ( known per se and not illustrated) , in particular made of silicone , is configured to guarantee the seal of the vacuum throughout the mould 13 . Even more in detail , at least one sealing ring is arranged in the mould 13 to guarantee that the inj ected resin does not flow out of the mould 13 once closed . Alternatively, the resin is inj ected by application of a positive thrust pressure , which forces the flow of the resin from the tank towards the inlet channel 21 .

[0207] According to an alternative embodiment not illustrated, the mould 13 could comprise two or more outlet channels 24 .

[0208] Therefore , the resin is inj ected into the mould 13 in such a way as to occupy the cavity 20 and flow through the outlet channel 24 .

[0209] Complete filling of the cavity 20 by the inj ected resin is indicated by outflow of the resin from the outlet opening 26 fluidically connected to the inlet opening 22 and, in use , to the cavity 20 .

[0210] At this point , the outlet channel 24 and, therefore , the outlet opening 26 are sealed fluid-tight so as to stop the inj ected resin from flowing out .

[0211] At the same time , according to the invention, the resin continues to be fed towards each inlet opening 22 .

[0212] Since the outlet opening 26 is sealed, this step causes a pressure increase inside the mould 13 , in particular inside the cavity 20 , and consequently the application of a uni form hydrostatic pressure by the resin (more precisely by the continued feeding of the latter ) on the first skin 18 and on the second skin 19 . Once the predetermined consolidated hydrostatic pressure is reached, for example 5 bar, inj ection of the resin is stopped .

[0213] In particular, the hydrostatic pressure is uni form and is applied both on the first skin 18 and on the second skin 19 . Therefore , the method according to the invention comprises the step of h) inj ecting thermosetting resin into the closed mould 13 through an inlet opening 22 of the mould 13 , so that it occupies the cavity 20 and laps the first skin 18 and the second skin 19 .

[0214] Furthermore , the method according to the invention comprises the step of i ) applying a uni form hydrostatic pressure on the first skin 18 and on the second skin 19 by inj ection of the resin .

[0215] In particular, the method according to the present invention comprises the further steps of continuing to inj ect the resin through the inlet opening 22 until the inj ected resin flows out of the outlet opening 26 and sealing the outlet opening 26 fluid- tight , so as to stop the inj ected resin from flowing out .

[0216] Preferably, the thermosetting resin is inj ected onto the first skin 18 and onto the second skin 19 , without impregnating them, applying the above-mentioned hydrostatic pressure .

[0217] Therefore , in accordance with the above , conveniently, in steps h) and i ) of the method according to the present invention, the thermosetting resin is inj ected onto the first skin 18 and onto the second skin 19 , without impregnating them .

[0218] This preserves the orientation of the fibres of the first skin 18 and the second skin 19 , which, as speci fied above , are not impregnated in an uncontrolled manner during the inj ection of resin into the mould 13 . This guarantees the direction of the fibres of the first skin 18 and the second skin 19 .

[0219] After completing said inj ection process , the mould 13 is opened, namely the second region 15 is separated from the first region 14 , and the assembly defined by the first skin 18 , by the coated central structure 5 , and possibly by the auxiliary structure 6 and the second skin 19 , namely the blade 1 including the inj ected and consolidated resin, is extracted from the mould 13 .

[0220] Conveniently, a curing cycle is carried out on the assembly defined by the first skin 18 , by the coated central structure 5 and by the second skin 19 .

[0221] Therefore , preferably, the method according to the present invention further comprises the step of administering heat and applying pressure to the material in the mould 13 so as to carry out a curing cycle on the assembly defined by the first skin 18 , by the at least one portion of the coated central structure 5 and by the second skin 19 .

[0222] Optionally, the curing cycle is carried out on the assembly defined by the first skin 18 , by the coated central structure 5 , by the auxiliary structure 6 and by the second skin 19 . In particular, heat is administered and pressure is applied to the assembly so as to carry out the curing cycle . Furthermore , once the curing cycle has been completed, this cured assembly undergoes an appropriate cooling cycle .

[0223] The present invention also concerns a device for manufacturing the blade 1 made of composite material for a rotor of an aircraft starting from the central structure 2 comprising the above-mentioned core structure .

[0224] Preferably, the core structure comprises a foam core . In particular, the foam core comprises a polymethylmethacrylimide ( PMI ) -based rigid material , even more speci fically it comprises a closed-cell foam . In particular, the closed-cell foam has a thermal stability also at very high temperatures , even more speci fically up to a temperature of 210 ° .

[0225] In further detail , the closed-cell foam is a rigid foam . Alternatively, the core structure comprises a core made of composite material .

[0226] The above-mentioned device comprises lamination means configured to laminate at least one layer of pre-impregnated composite material 3 including dispersed fibres with a predefined orientation in a thermosetting resin matrix onto the outer surface 4 of the central structure 2 , thereby obtaining the above-mentioned coated central structure 5 . In particular, the lamination means comprise automated means , even more speci fically manipulation systems , for example robots , to laminate the above-mentioned layers onto the outer surface 4 of the central structure . According to a pos sible embodiment , the lamination means comprise a vacuum bag . In particular, the layers of composite material 3 are arranged inside the vacuum bag and heated to a predetermined temperature , for example to fi fty or eighty degrees Celsius ( ° C) ; subsequently the vacuum is created in such a way as to laminate the above-mentioned layers of composite material 3 by means of compaction of the latter .

[0227] According to an alternative embodiment , the layers of composite material 3 are arranged on the further forming tool and laminated by means of a pressure exerted by the further forming surface on the above-mentioned layers of composite material 3 by compaction of the latter .

[0228] Alternatively, the layers of composite material 3 are manually laminated onto the outer surface 4 of the central structure 2 , for example by manual application of the above- mentioned layers of composite material 3 on the outer surface 4 by an operator .

[0229] The above-mentioned device further comprises the mould 13 having the first region 14 and the second region 15 delimiting between them a space adapted to accommodate at least one portion of the coated central structure 5 .

[0230] In accordance with the above , the lamination means are further configured to :

[0231] - laminate at least one layer of pre-impregnated composite material 3 onto the first region 14 of the mould 13 , thereby obtaining the above-mentioned first skin 18 ;

[0232] - laminate at least one layer of pre-impregnated composite material 3 onto the assembly defined by the first region 14 of the mould 13 , by the first skin 18 and by the portion of the coated central structure 5 , thereby obtaining the second skin 19 , the first skin 18 and the second skin 19 wrapping the coated central structure 5 ( as previously explained) .

[0233] Furthermore , the second region 15 is configured to be arranged on the assembly defined by the first region 14 of the mould 13 , by the first skin 18 , by the portion of the coated central structure 5 and by the second skin 19 , in such a way as to close the mould 13 and define a cavity 20 between at least the second skin 19 and a region of said mould 13 .

[0234] Preferably, the second region 15 is configured to be arranged on the assembly defined by the first region 14 of the mould 13 , by the first skin 18 , by the portion of the coated central structure 5 , by the auxiliary structure 6 and by the second skin 19 , so as to close the mould 13 and def ine a cavity 20 between at least the second skin 19 and a region of said mould 13 .

[0235] The above-mentioned device further comprises inj ection means configured to inj ect thermosetting resin into the closed mould 13 through an inlet opening 22 of the mould 13 , so as to occupy said cavity 20 and lap (preferably completely) the first skin 18 and the second skin 19 , and in such a way as to apply a uni form hydrostatic pressure on the first skin 18 and on the second skin 19 by inj ection of said resin .

[0236] According to a possible embodiment , the inj ection means comprise a device configured to inj ect the thermosetting resin into the mould 13 , for example a vacuum pump configured to suck the resin into the mould 13 by application of the vacuum inside the mould 13 by means of a vacuum source ( known per se and not illustrated) .

[0237] According to an alternative embodiment , the resin inside the mould is inj ected by means of manual inj ection devices such as , for example , lever instruments or hydraulic pistons .

[0238] From the above , the advantages of the manufacturing method and device of the blade 1 according to the present invention are clear .

[0239] Firstly, using the manufacturing method according to the present invention, the coated central structure 5 is subj ect to a reduced number of curing cycles , preserving the physical and / or chemical properties of the resin impregnating the fibres .

[0240] Due to this expedient , the assembly defined by the first skin 18 , by the coated central structure 5 , and possibly by the auxiliary structure 6 and by the second skin 19 extracted from the mould 3 has a low porosity level and a high-quality surface finish, thereby obtaining optimal surface characteristics also in the j oining zone between said pieces .

[0241] Moreover, inj ecting the resin through the inlet opening 22 in a continuous manner until the inj ected resin flows out of the mould 13 through the outlet opening 26 allows removal from the mould 13 of any air bubbles that have formed due to closing of the mould 13 .

[0242] Furthermore , the use of a foam core gives the blade 1 various functional properties . In particular, the foam has a very low density, which helps to reduce the overall weight of the blade 1 with respect to the blades currently on the market , improving the aerodynamic performance thereof . In addition to the above , the foam can absorb and dissipate energy, giving the blade 1 resistance to the impact and vibrations to which it is subj ect during flight .

[0243] Lastly, it is clear that modi fications and variations that do not depart from the protective scope defined by the claims can be made to the blade 1 , and to the method and device for manufacturing said blade 1 according to the present invention .

Claims

CLAIMS1. A method for manufacturing a blade (1) of an aircraft rotor made of composite material; the method comprises the steps of : a) arranging a central structure (2) comprising a core structure ; b) laminating at least one layer of pre-impregnated composite material (3) including dispersed fibres with a predefined orientation in a thermosetting resin matrix on an outer surface (4) of the central structure (2) , thereby obtaining a coated central structure (5) ; c) arranging a mould (13) having a first region (14) and a second region (15) delimiting between them a space capable of accommodating at least a portion of the coated central structure (5) ; d) laminating at least one layer of said composite material (3) on the first region (14) of said mould (13) , thereby obtaining a first skin (18) of composite material; e) placing said at least one portion of said coated central structure (5) on the first region (14) of the mould (13) , such that said portion of the coated central structure (5) lies on the first skin (18) ; f) laminating at least one layer of said composite material (3) onto the assembly defined by the first region (14) of the mould (13) , the first skin (18) and said portion of the coated central structure (5) , thus obtaining a second skin (19) of composite material, and in such a way that the first skin (18) and the second skin (19) wrap the portion of the coated central structure ( 5 ) ; g) closing the mould (13) so as to define a cavity (20) between at least the second skin (19) previously laminated over said portion of the coated central structure (5) and the second region (15) of said mould (13) ; h) injecting thermosetting resin into the closed mould (13) through an inlet opening (22) of the mould (13) so as to occupy said cavity (20) and lap the first skin (18) and the second skin(19) ; and i) applying uniform hydrostatic pressure to the first skin (18) and the second skin (19) by injection of said resin.

2. The method as claimed in claim 1, wherein the core structure comprises a foam core or a composite material core comprising dispersed fibres with a predefined orientation in a thermosetting resin matrix.

3. The method according to claim 1 or 2, comprising the step of, prior to step b) of laminating, placing an adhesive material at least partially on the central structure (2) .

4. The method as claimed in any one of the preceding claims, wherein in steps h) and i) , the thermosetting resin is injected onto the first skin (18) and the second skin (19) , without impregnating the latter.

5. The method as claimed in any one of the preceding claims, further comprising the step of administering heat and applying pressure to the material in the mould (13) so as to effect a curing cycle on the assembly defined by the first skin (18) , said at least one portion of the coated central structure (5) and the second skin (19) .

6. The method as claimed in any one of the preceding claims, wherein step b) of laminating at least one layer of preimpregnated composite material (3) including dispersed fibres with a predefined orientation in a thermosetting resin matrix on an outer surface (4) of said central structure (2) comprises the further steps of: bl) laminating at least two layers of said composite material (3) on the outer surface (4) of the central structure ( 2 ) ; and b2) compacting the at least two layers of composite material(3) together.

7. The method as claimed in claim 6, wherein step b2) of compacting the at least two layers of composite material (3) comprises :- arranging the assembly defined by the central structure(2) and the two layers of composite material (3) inside a vacuum bag;- heating the assembly defined by the central structure (2) and the two layers of composite material (3) to a predetermined temperature; and- applying the vacuum inside the vacuum bag so as to compact the layers of composite material (3) .

8. The method as claimed in claim 6, wherein step b2) of compacting at least two layers of composite material (3) comprises :- arranging a first forming tool having a first forming surface ;- placing the assembly defined by the central structure (2) and the two layers of composite material (3) in contact with the forming surface; and- compacting the at least two layers of composite material(3) by pressure applied from the first forming surface against the assembly defined by the central structure (2) and the two layers of composite material (3) .

9. The method as claimed in any one of the preceding claims, wherein the step d) of laminating comprises: laminating at least two layers of pre-impregnated composite material (3) including dispersed fibres with a predefined orientation in a thermosetting resin matrix onto the first region (14) of the mould (13) ;- placing the assembly defined by the first mould region (14) and the two layers of composite material (3) inside a vacuum bag;- heating the assembly defined by the first mould region (14) and the two layers of composite material (3) to a predetermined temperature; and- applying the vacuum inside the vacuum bag so as to compact the two layers of composite material (3) ; or wherein the step d) of laminating comprises: laminating at least two layers of pre-impregnated composite material (3) including dispersed fibres with a predefined orientation in a thermosetting resin matrix over the first mould region (14) ;- arranging a second forming tool with a second forming surface ;- placing the assembly defined by the first mould region (14) and at least two layers of composite material (3) in contact with the second forming surface; and- compacting the two layers of composite material (3) by pressing the second forming surface against the assembly defined by the first mould region (14) and the two layers of composite material (3) .

10. The method as claimed in any one of the preceding claims, and further comprising the steps of: j ) arranging, subsequent to the steps d) of laminating and e) of placing and prior to the step f) of laminating, at least one auxiliary structure (6) comprising a foam core or a composite material core including dispersed fibres with a predefined orientation in a thermosetting resin matrix on the first region (14) of the mould (13) , such that said at least one auxiliary structure (6) is arranged on the first skin (18) , in a position adjacent to said portion of the coated central structure (5) ; and wherein the step f) of laminating comprises laminating at least one layer of said pre-impregnated composite material (3) including fibres dispersed in a predefined orientation in a thermosetting resin matrix on the assembly defined by the first region (14) of the mould (13) , the first skin (18) , said portion of the coated central structure (5) and said auxiliary structure(6) , such that the first skin (18) and the second skin (19) wrap the portion of the coated central structure (5) and the auxiliary structure ( 6 ) .

11. The method as claimed in claim 10, wherein step j) of arranging comprises the step jl) of arranging an adhesive material at least partially on the coated central structure (5) and / or at least partially on the auxiliary structure (6) .

12. The method as claimed in any one of claims 10 or 11, wherein said auxiliary structure (6) defines a leading edge (7) and / or a trailing edge (8) of the blade (1) .

13. The method as claimed in any one of claims 10-12, wherein the step f) of laminating comprises: laminating at least two layers of pre-impregnated composite material (3) including dispersed fibres with a predefined orientation in a thermosetting resin matrix onto the assembly defined by the first skin (18) , by said portion of the coated central structure (5) and by said auxiliary structure (6) ;- placing the assembly defined by the first skin (18) , said portion of the coated central structure (5) , said auxiliary structure (6) and the two layers of composite material (3) within a vacuum bag; heating to a predetermined temperature the assembly defined by the first skin (18) , said portion of the coated central structure (5) , said auxiliary structure (6) and said two layers of composite material (3) ;- applying the vacuum within the vacuum bag so as to compact the two layers of composite material (3) ; or wherein the step f) of laminating comprises: laminating at least two layers of pre-impregnated composite material (3) comprising dispersed fibres in a predefined orientation in a thermosetting resin matrix over the assembly defined by the first skin (18) , said portion of the coated central structure (5) and said auxiliary structure (6) ;- arranging a third forming tool (9) having a third forming surface (10) ;- placing the assembly defined by the first skin (18) , said portion of the coated central structure (5) , said auxiliary structure (6) and said two layers of composite material (3) in contact with the third forming surface (10) ; and- compacting the two layers of composite material (3) by pressing the third forming surface (10) against the assembly defined by the first skin (18) , said portion of the coated central structure (5) , said auxiliary structure (6) and the two layers of composite material (3) .

14. The method as claimed in any one of the preceding claims, wherein the mould (13) comprises an outlet opening (26) fluidically connected to the inlet opening (22) and, in use, to said cavity (20) ; wherein the method comprises the further steps of: k) continuing to inject resin through said inlet opening (22) until the injected resin flows out of the outlet opening (26) ; and l) sealing the outlet opening (26) fluid-tight, so as to stop the injected resin from flowing out.

15. A device for manufacturing a blade (1) of composite material for an aircraft rotor from a central structure (2) comprising a core structure, said device comprising:- laminating means configured to laminate at least one layer of pre-impregnated composite material (3) comprising dispersed fibres in a predefined orientation in a thermosetting resin matrix on an outer surface (4) of the central structure (2) , resulting in a coated central structure (5) ; and- a mould (13) having a first region (14) and a second region (15) delimiting between them a space capable of accommodating at least a portion of the coated central structure (5) ; wherein the laminating means are further configured to laminate at least one layer of composite material (3) onto thefirst region (14) of the mould (13) , thereby obtaining a first skin (18) ; wherein the laminating means are also configured to laminate at least one layer of composite material (3) on the assembly defined by the first region (14) of the mould (13) , the first skin (18) and said at least one portion of the coated central structure (5) , thereby obtaining a second skin (19) , the first skin (18) and the second skin (19) wrapping the coated central structure ( 5 ) ; wherein the second region (15) is configured to be arranged on the assembly defined by the first region (14) of the mould (13) , the first skin (18) , said portion of the coated central structure (5) and said second skin (19) , so as to close the mould (13) and define a cavity (20) between at least the second skin (19) and a region of said mould (13) ; and wherein the device further comprises:- injection means configured to inject thermosetting resin within the closed mould (13) through an inlet opening (22) of the mould (13) , so as to occupy said cavity (20) and lap the first skin (18) and the second skin (19) , and so as to apply uniform hydrostatic pressure on the first skin (18) and the second skin (19) by injection of said resin.

16. A blade (1) for an aircraft rotor comprising: a central structure (2) comprising a core structure; at least one layer of pre-impregnated composite material (3) comprising dispersed fibres with a predetermined orientation in a thermosetting resin matrix laminated to an outer surface (4) of the central structure (2) to define a coated central structure ( 5 ) ; and a skin comprising at least one further layer of said composite material (3) wrapping the coated central structure (5) .

17. The blade as claimed in claim 16, wherein the core structure comprises a foam core or a composite material corecomprising dispersed fibres with a predefined orientation in a thermosetting resin matrix.

18. The blade as claimed in any one of claims 16 or 17, further comprising at least one auxiliary structure (6) comprising a foam core or a composite material core including fibres dispersed in a predefined orientation in a thermosetting resin matrix arranged adjacent to the coated central structure (5) , wherein the skin wraps the coated central structure (5) and the auxiliary structure (6) .

Images