Segmented-frame conveyor equipped with indexing plates for stamping a part made of a thermoplastic polymer matrix composite material

Abstract

A conveyor (1) for a preform (2) made of a thermoplastic polymer matrix composite material, this conveyor (1) comprising: - two guide branches (3a) and at least two free branches (3b), forming a flat and rigid outer frame (3); - a segmented inner frame (4) composed of at least three geometric indexing plates (4a); - means for holding the preform (2) on the geometric indexing plates (4a); and - a flexible attachment means between the outer frame (3) and each geometric indexing plate (4a).

Description

[0001] DESCRIPTION

[0002] SEGMENTED FRAME CONVEYOR EQUIPPED WITH INDEXING PLATES FOR STAMPING A PART MADE OF THERMOPLASTIC MATRIX COMPOSITE MATERIAL

[0003] TECHNICAL FIELD

[0004] The invention relates to a conveyor used during the manufacture and shaping of a part made of thermoplastic matrix composite material. More particularly, the present invention relates to the manufacture of composite parts used as structural parts in aircraft, these structural parts generally having at least one curvature and / or a structure of complex configuration. These curved and / or complex parts are conventionally produced by stamping.

[0005] PRIOR ART

[0006] The share of composite materials in aircraft is growing rapidly, with composite materials making it possible in particular to lighten the structure of aircraft, which were previously mainly made of metal parts, and thus to reduce kerosene consumption. In addition to their advantageous mechanical properties / density ratio, composite materials are generally resistant to corrosion, extreme temperatures and humidity.

[0007] In addition to these advantages, which are highly valued in the aeronautical field, there is a "custom" design that allows for high anisotropy of the mechanical properties of the manufactured part, which thus adapts to the mechanical stresses it will undergo. This "custom" design is based in particular on the choice of materials used in the composite material as well as their arrangement, such as linear carbon fibers to manufacture a part subjected to unidirectional stress or woven and stacked fibers to manufacture a part subjected to a stress field.

[0008] These fibers, linear or woven, constitute a fiber reinforcement which is contained in a matrix. The composite material is manufactured in plate according to the classic methods of the state of the art. For shaping by stamping, this is carried out hot: the composite plate is therefore first cut into preforms to the dimensions of the part to be stamped then heated before being shaped by stamping. The matrix is ​​generally a thermoplastic resin matrix, this having the advantage of deforming after heating while regaining its initial mechanical properties after cooling, unlike thermosetting resins whose mechanical properties in the solid state are irreversible and cannot be remelted after their manufacture.

[0009] To stamp composite parts, it is therefore necessary to convey the preforms between the oven, in which they have been heated, and the stamping tool which comprises two complementary molds, the die and the punch. The preform being heated, it is malleable and can only be conveyed with a support. The conveying is generally carried out by a horizontal and rigid frame on which is fixed either a release film which will follow the preform during the entire stamping cycle, or springs which hold the preform, this frame ensuring the transport and the maintenance of the preform during stamping.

[0010] However, although the release film resists heating temperature well, it has a limited elongation rate which is not suitable for stamping parts with a non-developable surface, i.e. parts whose surface cannot be "flattened" without tearing or stretching it.

[0011] Similarly, springs are difficult to adapt to the stamping of large preforms because they must have both a sufficiently high stiffness to support the weight of the preform and a sufficiently low stiffness to accompany the preform in its shaping during the mold closing phase during stamping. In addition, depending on their position and the final shape of the part to be manufactured by stamping, the springs will have a different elongation that is difficult to predict.

[0012] Another disadvantage of flat stamping preforms to produce curved parts lies in the topology of the molds: in fact, since the molds are curved and have a lower temperature than the preforms, the contact of the curved molds with the preforms occurs gradually and causes heterogeneous cooling of the surfaces in contact, and of the part in general, which can be the cause of geometric distortions during cooling and / or internal stresses in the part.

[0013] STATEMENT OF THE INVENTION

[0014] The main objective of the invention is to improve the stamping of a preform made of composite material using a conveyor making it possible to improve the quality of the stamping and therefore of the parts produced.

[0015] To improve the quality of the stamping, the invention provides for adapting the conveyor to the topology of the part to be stamped by internal guidance and thus making it possible to shape the preform by substantially uniform positioning thereof relative to the molding surfaces of the stamping tool.

[0016] More specifically, the present invention relates to a conveyor for a flat preform made of thermoplastic matrix composite material transporting this preform between a heating furnace and a stamping tool, this conveyor comprising two guide branches parallel to each other and at least two other free branches, the guide branches and the free branches forming a flat and rigid external frame.

[0017] The conveyor also includes:

[0018] - an internal segmented frame composed of at least three geometric indexing plates coplanar with the external frame, arranged between the preform and the external frame, each geometric indexing plate having a location and drive interface in a direction perpendicular to the external frame;

[0019] - means for holding the preform on the geometric indexing plates, and

[0020] - a flexible means of attachment between the external frame and each geometric indexing plate.

[0021] Advantageously, the flat external frame allows the preform to be heated flat, this flat heating then being uniform over the entire preform, allowing for homogeneous and therefore better quality stamping shaping. Also advantageously, the internal segmented frame allows the preform to approach the curvature of the stamping molds: the contact of the molds with the preform is then homogeneous and rapid over the entire preform, thus limiting temperature variations at the time of contact with the molds and therefore internal stresses in the part as well as its geometric distortion during cooling.

[0022] Advantageously also, the parts obtained by stamping preforms held by geometric indexing plates have optimized mechanical performance because the rate of internal stresses is minimized. With the same mechanical strength, the parts resulting from this stamping are therefore of reduced thickness, thereby reducing the weight of the part.

[0023] According to preferred embodiments taken alone or in combination:

[0024] - the external frame is rectangular;

[0025] - the internal segmented frame comprises at least three geometric indexing plates opposite each guide branch of the external frame;

[0026] - hooks hold the preform on the geometric indexing plates;

[0027] - tension springs hold the preform on the geometric indexing plates;

[0028] - each geometric indexing plate is attached to the external frame by a flexible spring;

[0029] - at least one secondary indexing plate is arranged between the preform and each free branch of the external frame;

[0030] - each secondary indexing plate is connected to the preform by a holding means and to a free branch by a flexible attachment means;

[0031] - each secondary indexing plate has a location and drive interface;

[0032] - the localization and training interface is made by a bore;

[0033] - the location and drive interface is made by a through bore;

[0034] - the location and drive interface is provided by at least one lug. The invention also relates to a stamping tool comprising:

[0035] - two molds producing a lower die and an upper punch, these molds being secured to, respectively, a lower press plate and an upper press plate;

[0036] - a conveyor as defined above with an internal segmented frame composed of at least three geometric indexing plates;

[0037] - at least three upper indexing pads installed on the upper press plate, each upper indexing pad being capable of driving a geometric indexing plate during the stamping of a composite preform.

[0038] According to preferred embodiments taken alone or in combination:

[0039] - the lower press plate has lower indexing studs installed on the lower press plate and opposite the upper indexing studs, and

[0040] - each upper indexing pad has a drive pin which passes through the location and drive interface of a geometric indexing plate and which is inserted into a lower indexing pad.

[0041] - a stop mechanism equips at least one upper indexing stud, and

[0042] - a stop mechanism equips at least one indexing stud and lower ones.

[0043] PRESENTATION OF FIGURES

[0044] Other characteristics and advantages of the invention will emerge from the non-limiting description which follows, with reference to the appended drawings which represent respectively:

[0045] Figure 1, a schematic representation seen from above of an example of a conveyor of a composite preform according to the invention;

[0046] Figure 2a, Figure 2b, a schematic representation in section in plane A of two variants of the stamping tool;

[0047] Figure 3, Figure 4 and Figure 5, a schematic sectional representation in plane A (see Figure 1) of the stamping tooling and the conveyor during different stages of the stamping of the composite preform; Figure 6, Figure 7, Figure 8, Figure 9, Figure 10 and Figure 11, a sectional representation in plane B (see Figure 1) of the stamping tooling and the conveyor during different stages of the stamping of the composite preform.

[0048] DETAILED DESCRIPTION

[0049] Figure 1 illustrates a conveyor 1 of a preform 2 made of composite material in the plane P of the external frame 3. This preform 2 is made up of fibers 2a contained in a matrix 2b. These fibers are oriented in the longitudinal direction X of the preform 2, the latter being shaped by stamping resulting, in this exemplary embodiment, in a curvature (see figure 11) of the preform 2 in this longitudinal direction X. Stamping therefore makes it possible to produce a part from the preform. Depending on the desired shape of the part after stamping, other orientations of the fibers and / or orientations more complex than linear - for example laminates with unidirectional folds or fabrics - are produced in the preform depending on the mechanical constraints observed in the part to be produced.

[0050] To carry out the stamping of the preform 2, it is first heated so that it can be deformed without damaging its structure: a thermoplastic matrix 2b is therefore chosen. Indeed, thermoplastic materials have the advantage of deforming after heating and regaining their initial mechanical properties after cooling. This behavior makes it possible to heat a preform again to flatten it or send it to another stamping tool without causing any degradation of its mechanical performance.

[0051] The conveyor 1 therefore makes it possible to transport the preform 2 made of thermoplastic matrix composite material 2b between a heating furnace and a stamping tool 6 (see figures 2a-2b). The conveyor 1 comprises two guide branches 3a parallel to each other and parallel to the longitudinal direction X of the preform 2, as well as two free branches 3b perpendicular to the guide branches 3a. The guide branches 3a and free branches 3b form a flat and rigid external frame 3 of rectangular geometry in the plane P.

[0052] Conveyor 1 also includes:

[0053] - an internal frame called segmented 4 composed of six geometric indexing plates 4a facing each guide branch 3a of the external frame, the geometric indexing plates 4a being coplanar with the external frame 3 and arranged between the preform 2 and the external frame 3;

[0054] - tension springs 5a for holding the preform 2 on the geometric indexing plates 4a, and

[0055] - a flexible spring 5b between the external frame 3 and each geometric indexing plate 4a.

[0056] The branches 3a are called guide branches because they serve as anchor points for guiding the geometric indexing plates 4a called main plates during the shaping preceding the stamping of the preform 2 (see figure 4). The branches 3b are called free branches because they are not connected to the main indexing plates and are therefore free with respect to the guidance of these plates.

[0057] The internal segmented frame 4 serves as a preform holding frame, i.e. a rigid structure capable of holding the preform in a plane parallel to the plane P of the external frame during transport by the conveyor between the furnace and the stamping tool. In addition, the segmented structure of this internal frame composed of geometric indexing plates advantageously provides a weight saving to the conveyor, a mobility factor, as well as adaptability of the arrangement and shape of these plates depending on the shaping desired by stamping. To optimize the arrangement of the plates, a discretization of the stamping profile of the preform, i.e. a sectional discretization in the thickness of the part produced by stamping the preform, makes it possible to determine the spacing between each geometric indexing plate.Thus, the number of geometric indexing plates appears to be determined as inversely proportional to the radius of curvature of the stamping profile.

[0058] In this embodiment illustrated in Figure 1, the preform 2 is held to the geometric indexing plates 4a of the internal segmented frame 4 by twelve tension springs 5a. Each of the twelve geometric indexing plates 4a is therefore connected on the one hand to the external frame 3 by a flexible spring 5b and on the other hand to the preform 2 by a tension spring 5a. The geometric indexing plates 4a are distributed symmetrically on either side of the preform 2 in the direction of the longitudinal direction X. Alternatively to the tension springs 5a, hooks can hold the preform on the geometric indexing plates, or any other equivalent connecting element (steel wire, etc.).

[0059] The internal segmented frame 4 can advantageously be supplemented by secondary indexing plates 4b, these being arranged between the preform and a free branch 3b of the external frame 3 (in FIG. 1, only one secondary indexing plate 4b is shown). Each secondary indexing plate 4b is connected to the preform 2 by a holding means 4d, here a tension spring, and to a free branch 3b of the external frame 3 by a flexible attachment means, here a flexible spring 4e.

[0060] Furthermore, the internal segmented frame 4 being composed of several geometric indexing plates and secondary indexing plates, each of these indexing plates can be actuated individually in a stamping tool and thus initiate shaping of the preform 2. To be actuated, each geometric indexing plate 4a and secondary indexing plate 4b has a location and drive interface in a direction perpendicular to the plane P of the external frame 3. This location and drive interface is produced here by a through bore 4c. Alternatively, the location and drive interface can be produced by a lug driven by a shape complementary to this lug.

[0061] Figure 2a and figure 2b show, according to a section in plane A perpendicular to plane P of figure 1, two variants of a stamping tool 6 comprising:

[0062] - two molds producing a lower die 6a and an upper punch 6b, these molds being secured to - respectively - a lower press plate 6c and an upper press plate 6d;

[0063] - the conveyor 1 of figure 1 with the internal segmented frame 4 composed of 12 geometric indexing plates, and

[0064] - twelve upper indexing pads 6f installed on the upper press plate 6d, each upper indexing pad 6f being capable of driving a geometric indexing plate 4a during the stamping of a preform 2.

[0065] The stamping tool 6 of figure 2b further comprises twelve lower indexing studs 6e, installed on the lower press plate 6c and opposite the upper indexing studs 6f, the lower indexing studs 6e and upper indexing studs 6f being equipped with a stop mechanism 6i.

[0066] The sectional view in plane A shows only two geometric indexing plates 4a as well as two upper indexing pads 6f and two lower indexing pads 6e.

[0067] Each upper indexing pad 6f also includes driving means, a driving pin 6g in the example, which passes through the locating and driving interface, here the through bore 4c, and which is inserted into a lower indexing pad 6e during stamping (see figure 4).

[0068] Different stages of stamping the preform 2 are shown in Figures 3 to 5, the two variants of Figure 2a and Figure 2b being shown combined in the stamping tool 6, this combination also constituting an embodiment. During stamping, the lower press plate 6c is fixed and immobile. The upper press plate 6d descends towards the lower press plate 6c to engage in Figure 3 the upper indexing studs 6f in the geometric indexing plates 4a. The drive pins 6g then pass through the geometric indexing plates 4a in the through bores 4c. The upper punch 6b is not yet in contact with the preform 2.

[0069] The upper press plate 6d continues to descend towards the lower press plate 6c until, in Figure 4, the geometric indexing plates 4a come into contact with the lower indexing studs 6e installed on the lower press plate 6c. The drive pins 6g of the upper indexing studs 6f are then inserted into grooves 6h of the lower indexing studs 6e, advantageously providing an additional possibility of immobilizing the geometric indexing plates 4a.

[0070] Furthermore, the stop mechanisms 6i make it possible to accompany the closing of the upper punch 6b in the lower die 6a (see figure 5) while maintaining the geometric indexing plates 4a between the lower indexing studs 6e and the upper indexing studs 6f. In this exemplary embodiment, a stop mechanism equips each of the lower and upper indexing studs. Alternatively, a stop mechanism can be mounted either on lower indexing studs or on upper indexing studs.

[0071] Figures 6 to 11 illustrate different phases of the stamping of the preform 2 in a sectional view along plane B (see figure 1). In this plane B, the preform 2 is in section along the direction of the longitudinal direction X and the stamping tool comprises six lower indexing studs 6e facing six upper indexing studs 6f, distributed on either side of six geometric indexing plates 4a. In addition, the indexing studs are equipped with stop mechanisms 6i.

[0072] The lower die 6a and the upper punch 6b have a curvature C, this curvature being applied to the preform 2 during stamping. The objective of the stamping tooling being to carry out a preliminary shaping of the preform 2 using the geometric indexing plates 4a and the indexing pads, the latter discretizing the curvature C during this shaping. In the embodiment illustrated in Figure 6, the upper 6f and lower 6e indexing pads are aligned along three parallel planes Z1, Z2 and Z3 which make it possible to produce bearings that match the curvature C as closely as possible.

[0073] Figures 7 to 9 represent more precisely the contacting of the upper indexing pads 6f with the geometric indexing plates 4a in the planes Z1, Z2 and Z3 respectively.

[0074] Figure 10 shows in plane B the state of the stamping tool 6 illustrated in figure 4 in plane A (see figure 1). The geometric indexing plates 4a are then in contact with the upper 6f and lower 6e indexing pads, the drive pins 6g of the upper 6f indexing pads being inserted into the grooves 6h of the lower 6e indexing pads. In addition, the preform 2 is as close as possible to the curvature C. In figure 11, the stop mechanisms 6i accompany the closing of the upper punch 6b in the lower die 6a to finalize the shaping of the preform 2.

[0075] The invention is not limited to the embodiments described and shown. Thus, a number and a non-symmetrical arrangement of the geometric and / or secondary indexing plates provide additional shaping possibilities for the preform, in particular complex shaping, for example oblique or curved transverse to the longitudinal direction X. In addition, the plates can be connected by rods on which an indexing pad rests to achieve flat shaping.

Claims

CLAIMS 1. Conveyor (1) for a flat preform (2) made of thermoplastic matrix composite material transporting this preform (2) between a heating furnace and a stamping tool (6), this conveyor (1) comprising two guide branches (3a) parallel to each other and at least two free branches (3b), the guide branches (3a) and the free branches (3b) forming a flat and rigid external frame (3), the conveyor (1) being characterized in that it also comprises: - an internal segmented frame (4) articulated composed of at least three geometric indexing plates (4a) coplanar with the external frame (3), arranged between the preform (2) and the external frame (3), each geometric indexing plate (4a) having a location and drive interface in a direction perpendicular to the external frame (3); - means for holding the preform (2) on the geometric indexing plates (4a), and - a flexible attachment means between the external frame (3) and each geometric indexing plate (4a).

2. Conveyor (1) according to claim 1, characterized in that the external frame (3) is rectangular.

3. Conveyor (1) according to any one of claims 1 to 2, characterized in that the internal segmented frame (4) comprises at least three geometric indexing plates (4a) opposite each guide branch (3a) of the external frame (3).

4. Conveyor (1) according to any one of claims 1 to 3, characterized in that hooks hold the preform (2) on the geometric indexing plates (4a).

5. Conveyor (1) according to any one of claims 1 to 3, characterized in that tension springs (5a) hold the preform (2) on the geometric indexing plates (4a).

6. Conveyor (1) according to any one of claims 1 to 5, characterized in that each geometric indexing plate (4a) is attached to the external frame (3) by a flexible spring (5b).

7. Conveyor (1) according to any one of claims 1 to 6, characterized in that at least one secondary indexing plate (4b) is arranged between the preform (2) and each free branch (3b) of the external frame (3).

8. Conveyor (1) according to claim 7, characterized in that each secondary indexing plate (4b) is connected to the preform (2) by a holding means and to a free branch (3b) by a flexible attachment means.

9. Conveyor (1) according to any one of claims 7 to 8, characterized in that each secondary indexing plate (4b) comprises a location and drive interface.

10. Conveyor (1) according to any one of claims 1 to 9, characterized in that the location and drive interface is produced by a bore.

11. Conveyor (1) according to any one of claims 1 to 9, characterized in that the location and drive interface is produced by a through bore (4c).

12. Conveyor (1) according to any one of claims 1 to 9, characterized in that the location and drive interface is produced by at least one lug.

13. Stamping tool (6) comprising: - two molds producing a lower die (6a) and an upper punch (6b), these molds being secured to, respectively, a lower press plate (6c) and an upper press plate (6d); - a conveyor (1) according to any one of claims 1 to 12 with an internal segmented frame (4) composed of at least three geometric indexing plates (4a), and - at least three upper indexing pads (6f) installed on the upper press plate (6d), each upper indexing pad (6f) being capable of driving a geometric indexing plate (4a) during the stamping of a composite preform (2).

14. Stamping tool (6) according to claim 13, characterized in that the lower press plate (6c) comprises lower indexing studs (6e) installed on the lower press plate and opposite the upper indexing studs (6f).

15. Stamping tool (6) according to claim 14, characterized in that that each upper indexing pad (6f) comprises a drive pin (6g) which passes through the location and drive interface of a geometric indexing plate (4a) and which is inserted into a lower indexing pad (6e).

16. Stamping tool (6) according to any one of claims 13 to 15, characterized in that at least one upper indexing stud (6f) is equipped with a stop mechanism (6i).

17. Stamping tool (6) according to any one of claims 14 to 16, characterized in that at least one lower indexing stud (6e) is equipped with a stop mechanism (6i).

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