Method for manufacturing a workpiece made from a thermoplastic material reinforced with fibres

Abstract

Method for manufacturing at least one workpiece which comprises at least locally a rounded shape and / or an angle comprising the following successive steps: winding at least one fibre which is pre-imp

Description

Title: Method for manufacturing a workpiece made from a thermoplastic material reinforced with fibres Technical field of the invention The present invention generally relates to workpieces made from a composite material comprising a thermoplastic material reinforced with fibres. More specifically, the invention relates to a method for manufacturing a workpiece which comprises at least locally a rounded shape and / or an angle and which is formed from a thermoplastic material reinforced with fibres, such as a fitting used to connect at least two members. Prior art The use of a fitting formed from composite material, in particular from a thermoplastic material reinforced with fibres, such as glass or carbon fibres, is particularly advantageous for replacing metal fittings for fields in which the weight saving is essential, such as for example in aeronautics. Specific types of fittings have at least locally com plex shapes, being rounded and / or comprising an angle. It is known to manufacture these fittings from sheets which are formed by a flat stack of layers of fibres which are connected by a thermoplastic material. The sheets are deformed and assembled in order to produce a preform. Specific portions of the sheets are pleated, folded or cut out and displaced in order to form the rounded portions and the angles of the fitting to be manufactured. However, the pleating of the sheets for producing non-unfolding, rounded or angular shapes according to such a manufacturing method involves mechanical weaknesses, which greatly impairs the performance levels of the fitting by reducing the mechanical strength properties. Furthermore, the correct arrangement of the material of the sheets of the rounded portions and the angles in order to form the preform remains complex, which limits industrialisation. Summary of the invention Therefore, an object of the invention is to overcome these disadvantages and to provide a simple method for manufacturing a workpiece, such as a fitting, made of a thermoplastic material reinforced by fibres and comprising nonunfolding complex portions, which conserves the mechanical properties of the workpiece. Therefore, there is proposed a method for manufacturing one or more workpieces which comprise at least locally a rounded shape and / or an angle and which are formed from a thermoplastic material reinforced with fibres, characterized in that it comprises the following successive steps: - at least one step of winding at least one fibre which is pre-impregnated with a thermoplastic material around a mandrel in order to form on the mandrel a lay-up comprising a wound layer of fibres or a plurality of wound and superimposed layers of fibres, - at least one step of cutting out the lay-up formed, - at least one step of removing from the mandrel the cut-out lay-up, In one embodiment, the workpiece to be manufactured is obtained directly from the cut-out lay-up. In another embodiment, the manufacturing method comprises one or more preforms of the workpiece to be manufactured being obtained from the cut-out lay-up and further comprises a step of inserting one or more of the preforms inside a mould and of over-moulding from a thermoplastic material. For process reasons, the cut-out lay-up or preform may have a slightly different shape from the shape of the final workpiece to be manufactured, the over-moulding step in the mould may allow the desired, final shape to be obtained. In one embodiment, the manufacturing method may comprise a plurality of winding steps, a plurality of cut-out steps for the formed lay-ups, a plurality of steps of removing from the mandrel one or more preforms of the workpiece to be manufactured from each cut-out lay-up, the manufacturing method further comprising a step of superimposing a plurality of preforms obtained, the overmoulding step being carried out on the superimposition of preforms. In one embodiment, the step of cutting out the lay-up can lead to the production of two identical workpieces during the step of removal from the mandrel. Preferably, the step of winding the fibre around the mandrel is controlled by computer. Advantageously, the step of winding can be assisted by laser heating in order to maintain the thermoplastic material of the pre-impregnated fibre in the liquid state. Preferably, the fibre is wound around the mandrel so as to form a plurality of angles relative to the axis of the mandrel. For example, the material of the fibres wound around the mandrel can be selected from: carbon, glass, Kevlar® or an admixture thereof. Advantageously, a plurality of cut-out lay-ups or a plurality of preforms can be connected by a welding step, such as a step of ultrasonic welding. According to an alternative, a plurality of cut-out lay-ups or a plurality of preforms can be connected by a step of consolidation by heating. The heating allows the thermoplastic material to be melted again. The different heated cutout lay-ups or the different heated preforms to be assembled are connected to each other during the cooling of the thermoplastic material. The invention also relates to a fitting made of composite material which is manufactured by carrying out the manufacturing method as described above. Brief description of the figures Further aims, advantages and features will become apparent from the following description, which is given purely by way of illustration and with reference to the appended drawings, in which: [Fig 1] illustrates a first fitting to be manufactured, [Fig 2] is a flow chart illustrating the steps of a manufacturing method for the first fitting illustrated in Figure 1 according to an exemplary embodiment of the invention, [Fig 3A], [Fig 3B], [Fig 3C], [Fig 3D] and [Fig 3E] are schematic, perspective views of the first fitting illustrated in Figure 1 at different steps of the manufacture according to an exemplary embodiment of the manufacturing method of the invention, [Fig 4] illustrates a second fitting to be manufactured, [Fig 5] is a flow chart illustrating the steps of a manufacturing method for the second fitting illustrated in Figure 4 according to an exemplary embodiment of the invention, and [Fig 6A] and [Fig 6B] show schematic, perspective views of the second fitting illustrated in Figure 4 at different steps of its manufacture according to an exemplary embodiment of the manufacturing method of the invention. Detailed description of the invention Figure 1 illustrates a first exemplary embodiment of a workpiece 1 to be manufactured. The workpiece 1 to be manufactured is a T-shaped fitting which is used to connect two ball joint members which move relative to each other, in particular which are intended to be used in the field of aeronautics. Below, the fitting according to the first exemplary embodiment is called the "first fitting". The first fitting 1 comprises a body 2. The body 2 comprises a first portion 2a which is also referred to as the web and a second portion 2b which is in the form of a base and which comprises a fixing zone for the first member to be connected. The first portion 2a comprises a through-hole 3 which is arranged near an upper end and which is intended to receive a ball joint. The first portion 2a and the second portion 2b are monobloc and extend in accordance with substantially perpendicular geometric planes, respectively. The term "substantially perpendicular" is intended to be understood to mean here that the angle which is formed between the two geometric planes is included in the range from 60° to 90°. The web 2a comprises here first and second opposite main faces 4 and 5. The two main faces 4, 5 are substantially parallel and diverge in a direction away from each other in a lower portion of the web until moving into contact with the base. The first fitting 1 illustrated comprises two complex portions, each one constituted by a boss. A first boss 6 extends at the joint of the first face 4 and the base 2b and a second similar boss extends at the joint between the second face 5 and the base 2b. These bosses 6 provide an undulating appearance for the body 2 and allow the rigidity of the first fitting 1 to be improved. A first exemplary embodiment of the manufacturing method according to the invention which is intended to manufacture the first fitting 1 from composite material which is formed from thermoplastic material reinforced with fibres is described with reference to the flow chart of Figure 2. As illustrated in Figure 3A, during a step 100, one or more preimpregnated fibres made of a thermoplastic material are wound around a mandrel M in order to form, on the mandrel M, a lay-up 8 constituted by a plurality of layers of fibres which are wound and superimposed one on the other. In a variant, the lay-up 8 may comprise a single layer of wound fibres. In the exemplary embodiment illustrated, a fibre in the form of a band is wound around the mandrel M. According to an alternative, several fibres may be wound simultaneously around the mandrel M. Each fibre is initially prewound on a head. In order to carry out the filament winding, the mandrel M is rotated about the axis X thereof. A sub-step of the initial winding of the pre-impregnated fibres around the mandrel M allows a first layer to be formed around the mandrel M. This first layer is formed with the rotation of the mandrel M around the axis X thereof and the displacement of the heads which support the fibres parallel with the axis X. Subsequently, a succession of sub-steps of winding the fibres allows the lay-up 8 to be formed by superimposition of layers one on the other around the mandrel M. According to an alternative, the lay-up 8 may be constituted by a single layer of wound fibres. Advantageously, the step 100 of winding the fibres around the mandrel M may be controlled by computer and thus automated. Preferably, each fibre is wound around the mandrel M so as to advantageously form a plurality of angles relative to the axis X of the mandrel M in order to improve the final properties of mechanical strength of the first fitting 1 manufactured. Preferably, the angle varies between 0 and 90°. For example, for the same layer of fibres, the angle formed relative to the axis X of the mandrel M may be substantially constant plus or minus 5° and for each new layer the angle formed relative to the axis X of the mandrel M for this new layer may be different from the angle of the preceding layer while being substantially constant plus or minus 5° during the formation of this new layer. For example, the fibres may be glass fibres, carbon fibres, Kevlar® fibres or any other suitable material. The thermoplastic material is, for example, selected from the following materials: PEEK, PEKK, PPS, PEAK or any other suitable material. With reference to Figures 3A and 3B, in this first exemplary embodiment the mandrel M has an outer surface which comprises first and second grooves Ml and M2 which are radially opposite and intended to form first and second grooves 13 and 14 on the lay-up 8 and the first and second bosses 6 of the first fitting 1 to be manufactured. In a step 200, the lay-up 8 obtained at the end of the step 100 of filament winding is cut out. The number of cut-outs may vary as a function of the number and the shape of the preforms to be obtained for the manufacture of the desired workpiece to be manufactured. As illustrated in Figure 3B, in the first exemplary embodiment illustrated, four cut-outs are carried out on the lay-up 8. Naturally, the number of cut-outs may be different. Subsequently, in a step 300, the cut-out portions of the lay-up 8 are removed from the mandrel M in order to obtain the workpiece to be manufactured which is the first fitting in this first exemplary embodiment illustrated. The first and second ends 9 and 10 of the lay-up 8 are removed via two cut-outs which are formed in a plane perpendicular to the axis of the mandrel M and are not used. Two other cut-outs are formed in two different planes which are parallel with the axis X of the mandrel M so as to obtain identical first and second central portions which form first and second preforms 11 and 12 which are substantially identical, respectively. Each of the first and second preforms 11 and 12 comprises one of the first and second grooves 13 and 14. As can be seen in Figure 3C, the first and second opposite main faces are each formed from one of the preforms which are obtained in this manner from the common lay-up 8 which is formed in the step 100 of filament winding and positioned one against the other. In the exemplary embodiment illustrated with reference to Figure 3D, the first and second preforms 11 and 12 are subsequently positioned inside a mould 15 in order to carry out an additional over-moulding step 500, also referred to as injection-moulding. The over-moulding is carried out from a thermoplastic material. Preferably, the over-moulding is carried out from a thermoplastic material which is identical to the thermoplastic material of the pre-impregnated fibres used for the step 100 of filament winding around the mandrel M. The thermoplastic material may, for example, be reinforced by fibres. In the exemplary embodiment illustrated, thermoplastic material 16 reinforced with fibres is added by over-moulding to the first and second preforms 11 and 12 so as to connect the first and second preforms 11 and 12 and to form the base 2b of the first fitting 1. According to an alternative to the over-moulding step 500, the first and second preforms 11 can be connected by a welding step, such as an ultrasonic welding step. After the over-moulding step, the workpiece 17 obtained, illustrated in Figure 3E, is removed from the mould 15 in a step 600. According to embodiments, the step 600 of removal can be followed by optional steps 700 of finishing the workpiece 17, for example, steps of machining and / or polishing and / or surface treatment and application of a coating and / or inserting a trunnion in order to obtain the first fitting 1, as illustrated in Figure 1. Figure 4 illustrates a second embodiment of a workpiece to be manufactured. The workpiece to be manufactured is a fitting, known by the name corner fitting, which serves to join, reinforce and rigidify three planes together, and which is in particular intended to be used in the field of aeronautics. Below, the fitting according to the second embodiment is referred to as the "second fitting". The second fitting 18 comprises a body 19. The body 19 comprises a first portion 19a, a second portion 19b and a third portion 19c which are monobloc and which extend in different geometric planes, respectively. The first and second portions 19a and 19b form two wings, the joint of which forms a bending line 20 and extends in two substantially perpendicular planes. The third portion 19c extends in a plane which is substantially perpendicular to the plane of the first portion 19a and substantially perpendicular to the plane of the second portion 19b and extends from a first end of the first portion 19a as far as a first end of the second portion 19b. The term "substantially perpendicular" is intended here to be understood to mean that the angle formed between the geometric planes considered in pairs is included within the range from 60° to 90°. The outer face of each of the first portion 19a, second portion 19b and third portion 19c forms a connection zone with one of the three planes of an assembly, in which the second fitting 18 is intended to be fixed. A second exemplary embodiment of the manufacturing method according to the invention which is intended for the simultaneous manufacture of two second fittings 18 which are made of composite material and which are formed from thermoplastic material which is reinforced with fibres is described with reference to the flow chart of Figure 5. As illustrated in Figure 6A, during a step 110, one or more preimpregnated fibres made of a thermoplastic material are wound around a mandrel M in order to form, on the mandrel M, a lay-up 21 constituted by a plurality of layers of fibres which are wound and superimposed one on the other. In the exemplary embodiment illustrated, a fibre in the form of a band is wound around the mandrel M. According to an alternative, several fibres may be wound simultaneously around the mandrel M. Each fibre is initially prewound on a head. In order to carry out the filament winding, the mandrel M is rotated about the axis X thereof. A sub-step of initial winding of the pre-impregnated fibres around the mandrel M allows a first layer to be formed around the mandrel M. This first layer is formed with the rotation of the mandrel M around the axis X thereof and the displacement of the fibres parallel with the axis X. Subsequently, a succession of sub-steps of winding the fibres allows the lay-up 21 to be formed by superimposition of layers one on the other around the mandrel M. According to an alternative, the lay-up 21 may be constituted by a single layer of wound fibres. Advantageously, the step 110 of winding the fibres around the mandrel M may be controlled by computer and thus automated. Preferably, each fibre is wound around the mandrel M so as to advantageously form a plurality of angles relative to the axis X of the mandrel M relative to the axis of the mandrel M in order to improve the final properties of mechanical strength of the second fitting 1 manufactured. Preferably, the angle varies between 0 and 90°. For example, for the same layer of fibres, the angle formed relative to the axis X of the mandrel M may be substantially constant plus or minus 5° and for each new layer the angle formed relative to the axis X of the mandrel M for this new layer may be different from the angle of the preceding layer while being substantially constant plus or minus 5° during the formation of this new layer. For example, the fibres may be glass fibres, carbon fibres, Kevlar® fibres or any other suitable material. With reference to Figures 6A and 6B, in this second exemplary embodiment the mandrel M has first and second angular portions M3 and M4 which are radially opposite and which extend axially between the two ends of the mandrel M, each being intended to form a bending line of one of the two second fittings 18 to be manufactured. In a step 210, the lay-up 21 obtained at the end of the step 110 of filament winding is cut out. As illustrated in Figure 6B, in the second embodiment illustrated, a single cut-out is carried out on the lay-up 21. Naturally, the number of cut-outs may be different. Subsequently, in a step 310, the cut-out portions of the lay-up 21 are removed from the mandrel M in order to obtain the workpieces to be manufactured which are the two second fittings 18 in this second exemplary embodiment illustrated. The cut-out is carried out in a plane which is oblique relative to the axis X of the mandrel M so as to obtain two second substantially identical fittings 18 from the common lay-up 21. According to embodiments, the step 210 of cutting out can be followed by optional steps 610 of finishing the second fittings 18, for example, steps of machining and / or polishing and / or adding material and / or surface treatment and application of a coating. In another embodiment, the manufacturing method may comprise a plurality of winding steps 100, 110 each comprising the winding of one or more fibres pre-impregnated with a thermoplastic material around the mandrel M. The lay-up 8, 21 which is formed at the end of each winding step is cut out and removed from the mandrel M in order to obtain several preforms. Alternatively, the plurality of winding steps 100, 110 can be carried out on several different mandrels. The manufacturing method also comprises a step of superimposing a plurality of preforms which are obtained at the end of different winding steps. The over-moulding step 500 is thus carried out on the obtained superimposition of preforms inside the mould 15. The first and second fittings 1, 18 which are obtained according to the first and second embodiments are only possible examples of a workpiece to be manufactured according to the manufacturing method according to the invention and other forms or configurations are possible without departing from the scope of the invention.

Claims

1. Method for manufacturing one or more workpieces (1; 18) which comprise at least locally a rounded shape and / or an angle and which are formed from a thermoplastic material reinforced with fibres, characterized in that it comprises the following successive steps:- at least one step (100; 110) of winding at least one fibre which is preimpregnated with a thermoplastic material around a mandrel (M) in order to form on the mandrel a lay-up (8; 21) comprising a wound layer of fibres or a plurality of wound and superimposed layers of fibres,- at least one step (200; 210) of cutting out the lay-up (8; 21) formed, and- at least one step (300; 310) of removing from the mandrel (M) the cutout lay-up (8; 21).

2. Manufacturing method according to Claim 1, wherein the workpiece (18) to be manufactured is obtained directly from the cut-out lay-up (21).

3. Manufacturing method according to Claim 1, comprising one or more preforms (11, 12) of the workpiece (18) to be manufactured being obtained from the cut-out lay-up (21) and further comprising a step (400) of inserting one or more of the preforms (11, 12) inside a mould (15) and a step (500) of over-moulding a thermoplastic material.

4. Manufacturing method according to Claim 3, comprising a plurality of winding steps (100; 110), a plurality of cut-out steps (200; 210) for the formed lay-ups, a plurality of steps (300; 310) of removing from the mandrel one or more preforms of the workpiece to be manufactured from each cut-out lay-up, the manufacturing method further comprising a step of superimposing a plurality of preforms obtained, the over-moulding step being carried out on the superimposition of preforms.

5. Manufacturing method according to any one of the preceding claims, wherein a plurality of cut-out lay-ups or a plurality of preforms can be connected by a welding step, such as a step of ultrasonic welding.

6. Manufacturing method according to any one of the preceding claims, wherein the step (310) of cutting out the lay-up (21) leads to the production of two identical workpieces (18) during the step (300; 310) of removal from the mandrel (M).5 7. Manufacturing method according to any one of the precedingclaims, wherein the step (100; 110) of winding is assisted by laser heating in order to maintain the thermoplastic material of the pre-impregnated fibre in the liquid state.

8. Manufacturing method according to any one of the preceding 10 claims, wherein the fibre is wound around the mandrel (M) so as to form a plurality of angles relative to the axis (X) of the mandrel (M).

9. Manufacturing method according to any one of the preceding claims, wherein the material of the fibres wound around the mandrel (M) is selected from: carbon, glass, Kevlar® or an admixture thereof.15 10. Fitting made of composite material, characterized in that it ismanufactured by carrying out the manufacturing method according to any one of the preceding claims.

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