DEVICE AND METHOD FOR PRODUCING A MOLDED BODY FROM A FIBER MATERIAL

Abstract

The invention relates to a method (30) for producing a molded body (52) from a fiber material (50), wherein a textile structure (54) that is provided with a binder material is first produced from the fiber material (50) using a textile technology (step 32). This textile structure (54) is subsequently shaped (step 34) and fixed in a predetermined three-dimensional form by an activation of the binder material (step 36). The activation of the binder material (step 36) is carried out iteratively here. This means that the binder material is activated progressively in some selected areas of the textile structure (54) (and the shape of the structure is fixed in these areas as a result) before an activation/fixing is carried out in other areas of the textile structure (54).

Claims

1. A method for producing a molded body from a fiber material, the method comprising: wherein providing a textile structure with a binder material is produced from the fiber material using a textile technology; shaping the textile structure; and fixing the shaped textile structure in a predetermined three-dimensional form by an activation of the binder material wherein the activation of the binder material is carried out iteratively.

2. The method according to claim 1, wherein the activation of the binder material is carried out in-process during production of the textile structure.

3. The method according to claim 1, wherein the shaping of the textile structure and the activation of the binder material overlap in time.

4. The method according to claim 1, wherein the shaping of the textile structure (step 34) and the activation of the binder material (step 36) are carried out in synchronization with the production of the textile structure (step 32).

5. The method according to claim 1, wherein the shaping of the textile structure is carried out using an industrial robot.

6. The method according to claim 1, wherein the textile structure is produced by means of a weaving technology.

7. The method according to claim 1, wherein the activation of the binder material is accomplished by electromagnetic radiation.

8. The method according to claim 1, wherein the activation of the binder material is accomplished by electric current.

9. A device for producing a molded body from a fiber material, the device comprising: an assembly unit for producing a textile structure that is provided with a binder material from the fiber material; and, a fixing unit for geometrical fixing of the textile structure emerging from the assembly unit.

10. The device according to claim 9, wherein the fixing unit includes a shaping unit for spatial forming of the textile structure from fiber material.

11. The device according to claim 10, wherein the shaping unit includes at least one industrial robot.

12. The device according to claim 9, wherein the fixing unit includes an activation unit for activating a binder material contained in the textile structure.

13. The device according to claim 12, wherein the activation unit includes an electromagnetic radiation source.

14. The device according to claim 12, wherein the activation unit includes an electric current source.

15. The device according to claim 9, wherein the assembly unit includes a weaving machine.

16. The device according to claim 15, wherein the weaving machine is a single phase weaving machine.

Description

[0026] Exemplary embodiments and variants of the invention are explained in detail below on the basis of the drawings. They show:

[0027] FIG. 1 a perspective view of a molded body made from a fiber material;

[0028] FIG. 2 a schematic representation of a device for producing the molded body from FIG. 1;

[0029] FIGS. 3a-3f a schematic representation of a sequence of operations according to the invention for producing a molded body from a fiber material;

[0030] FIG. 4 a schematic representation of an alternative device for producing a molded body.

[0031] FIG. 1 shows, in a perspective view, a molded body 52 made from a fiber material 50. A carbon fiber roving can be used as fiber material 50, for example. The molded body 52 consists of a flat textile structure 54, which was produced by a weaving process known from the prior art and then formed. The textile structure 54 is thus a woven fabric 54′ with interwoven warp threads 55 and weft threads 56 made of fiber material 50. For reasons of clarity, only isolated warp and weft threads 55, 56 are shown in FIG. 1 here.

[0032] The molded body 52 is a dimensionally stable structure that has two domelike curves 58. Such a molded body 52 can be used, for example, as a preform for producing a fiber-reinforced composite component. In this case, the molded body is infiltrated with a resin in a subsequent step with the aid of an infusion process (resin transfer molding (RTM) or vacuum assisted resin infusion (VARI), for example), and the resin is then cured by the action of heat.

[0033] For producing the molded body from FIG. 1, a device 10 is employed that is shown in a schematic representation in FIG. 2. The device 10 includes a schematically indicated assembly unit 12 with a weaving machine 13, by means of which the woven fabric 54′ is produced. Some of the warp threads 55 are schematically indicated in the interior of the weaving machine 13.

[0034] The woven fabric 54′ is provided with a thermoplastic binder material, which can be thermally activated repeatedly, becomes soft under the action of heat, and solidifies again after cooling. The binder material is thus formable in the heated state, and the shape imposed by the shaping is “frozen” upon cooling. The binder material can be applied to the woven fabric 54′ in the form of a thermoplastic powder, for example during the course of or immediately after the production of the woven fabric 54′ in the weaving machine 13; alternatively, the fiber material of the warp threads 55 and/or the of weft threads 56 can have already been provided with the binder material prior to the weaving process.

[0035] On leaving the weaving machine 13, the woven fabric 54′ (area 60) has a slack, flat form, which is symbolized by a dashed representation of the warp and weft threads 55, 56. After leaving the weaving machine 13, the slack woven fabric 54′ arrives in a fixing unit 14, where it is brought into the desired three-dimensional shape and fixed. The fixing unit 14 includes a shaping unit 16, by means of which the fabric 54′ emerging from the weaving machine 13 can be shaped three-dimensionally. In the present exemplary embodiment, the domelike curve 58 is to be molded into the woven fabric 54′. To this end, the shaping unit 16 includes multiple manipulators 17, which are composed of a movable punch 20 and multiple grippers 21 in the present case. The grippers 21 grip the woven fabric 54′ at the sides and tauten it (arrows 23), while the punch 20, acting from below, bulges the woven fabric 54′ in the middle (arrow 22). The woven fabric 54′ is thus pulled over the punch 20 with the aid of the grippers 21, and the woven fabric 54′ is brought into the desired shape by the simultaneous application of force by the punch 20 and the grippers 21 (arrows 22, 23). In order to minimize a displacement of the fibers in the woven fabric 54′ in the event of strong bulging and shaping, the warp threads 55 in the weaving unit 13 are flexibly suspended in such a manner that they can yield in the event of strong (local) exertion of tensile forces by the shaping unit 16. In this context, the tension of the warp threads 55 can be set under closed- or open-loop control in such a manner that a required density and stability of the woven fabric 54′ is achieved on the one hand, but on the other hand a certain amount of play is present in order to avoid wrinkling of the woven fabric 54′ during the shaping.

[0036] If the desired three-dimensional shape has been achieved in a selected area of the woven fabric 54′, then this shape is permanently fixed with the aid of an activation unit 18 integrated in the fixing unit 14. In the present exemplary embodiment, the activation unit 18 is an infrared source 18′ whereby the selected areas of the woven fabric 54′ can be heated. The thermoplastic binder material contained in the woven fabric 54′ is melted by the heating and solidifies upon cooling in the shape molded in the woven fabric 54′ by the shaping unit 16, by which means this three-dimensional shape is “frozen” and thus fixed.

[0037] In an area 62 of the woven fabric 54′ more distant from the weaving machine 13, this shape is already “frozen,” which is symbolized by a representation of the warp and weft threads in solid lines. In this area 62, the woven fabric 54′ that was shaped in an earlier process step is already fixed in the shaped form, and thus no longer requires manipulators 17 to hold the woven fabric 54′ in this area 62 in shape. As the weaving process progresses, the woven fabric 54′ produced by the weaving machine 13 is thus transported in the direction of the fixing unit 14, where it is locally shaped and fixed in shape and then transported onward (arrow direction 24). Shown in FIG. 2 is a snapshot in which some areas 60 of the woven fabric 54′ are already fixed in shape while other areas 60 are still limp and unshaped.

[0038] FIGS. 3a-3f show, in a schematic representation, a sequence of operations 30 for producing a molded body from a fiber material 50. The production of a textile structure 54 is carried out (continuously or progressively) using a textile process in the assembly unit 12 (method step 32, FIG. 3a). The textile structure 54 emerging from the assembly unit 12 is limp at first, which is represented by a dashed line. The textile structure 54 arrives in the fixing unit 14, where it is first shaped with the aid of a shaping unit 16, wherein a punch 20′ is symbolically represented as a forming tool (method step 34, FIG. 3b). The area of the textile structure 54 shaped by means of the punch 20′ is subsequently fixed in this shaped state with the aid of the activation unit 18 (method step 36, FIG. 3c). In this process, a binder material contained in the textile structure 54 is cured, for example with a use of electromagnetic radiation, by which means the textile structure 54 is now flexurally stiff in this area and the curve molded by the punch 20′ is “frozen”. The fixed part 62′ of the textile structure 54 is indicated by a solid line in FIG. 3c.

[0039] Another section of limp textile structure 54 is now produced by the assembly unit 12 (method step 32, FIG. 3d), which arrives in the fixing unit 14 and is shaped with the use of another punch 20″ (method step 34, FIG. 3e). The area of the textile structure 54 shaped by means of this punch 20″ is subsequently fixed in turn in this shaped state with the aid of the activation unit 18 (method step 36, FIG. 3f). FIGS. 3a-3f thus show a sequence of operations 30 in which the production (step 32), shaping (step 34), and fixing in shape (step 36) of the textile structure 54 are carried out area-by-area and progressively in sequence. However, the method steps can advantageously overlap in time, so that, for example, the production (step 32) is carried out continuously and shaping (step 34) and fixing in shape (step 36) are carried out in synchronization with production (step 32). Furthermore, shaping (step 34) and fixing in shape (step 36) can also overlap in time, for example in that the limp woven fabric 54 is continuously formed with the aid of manipulators 17 (step 34) and the fixing (step 36) is carried out in sections synchronously therewith.

[0040] In the exemplary embodiment shown in FIG. 4, a method is used for producing a molded body 52″ in which the process step of producing the woven fabric 54′ (step 32) overlaps continuously with the process steps of shaping (step 34) and fixing (step 36): Here, a woven fabric 54″ emerging continuously from the weaving machine 13 is not only tensioned and shaped with the aid of manipulators 17, which have the form of robot-guided grippers, but also draped three-dimensionally in space. The warp threads 55 (of which only a few are represented in FIG. 4) always run linearly in this case; the actual “rotating” of the object formed from the woven fabric 54″ is done by the manipulators 17. With the aid of the activation unit 18, selected areas of the woven fabric 54″ formed by the manipulators 17 are fixed continuously and in synchronization with the emergence of the woven fabric 54″ from the weaving machine 13. The areas 62″ fixed in this manner are represented with dots in FIG. 4. With the aid of the method shown in FIG. 4, any desired three-dimensionally shaped molded bodies 52″ can be produced, which, in particular, can have undercuts or can even be designed as spatially closed hollow bodies. Production of such molded bodies 54″ is not possible using conventional preforming methods, in which the woven fabric 54″ is placed in a fixed mold and shaped and fixed as a whole.

[0041] In the exemplary embodiments from FIGS. 1 to 3, the fixing of the shaped woven fabric 54, 54′, 54″ is carried out by heating with the aid of an electromagnetic radiation source, for example by infrared radiation or by UV radiation (when a thermosetting resin is used as binder material, for example).

[0042] If at least some of the warp and weft threads are electrically conductive, then the heating can also be accomplished by means of electric current. In this case, an electric current is applied to selected warp threads 55 and weft threads 56. The strength of the current is chosen in such a way that sufficient heating for activating the binder material is achieved in the area of the crossing points of the fibers 55, 56 that are supplied with current; in these areas, therefore, the binder material is melted and solidifies after cooling in the three-dimensional shape molded by the manipulators. The area where the binder material is to be activated can be defined very precisely by the choice of the fibers that are supplied with current, so that well-defined local curing takes place.

[0043] Activation by means of electric current has the advantage that even fiber structures that are opaque to electromagnetic radiation, which is to say that can only be surface-hardened with the aid of a radiation source, can be cured in this way. In the case of activation by means of electric current, however, only areas in which the fibers are incorporated in the woven fabric (i.e., have crossing points with other fibers) can be fixed, in contrast to activation by means of electromagnetic radiation.

[0044] Alternatively to the thermoplastic binder material described in the exemplary embodiments, a thermosetting binder material can be used. Such a thermosetting binder can, in particular, be applied in liquid form to the fibers before the fibers are made up into the textile structure 54. The activation of the thermosetting binder is carried out with the aid of UV radiation, for example; in this case, the activation unit is designed as a UV source.

[0045] In the exemplary embodiments from FIGS. 1 to 4, the invention was explained on the basis of a flat woven fabric 54, 54′, 54″. As a result of using a 2.5-dimensional or 3-dimensional weaving process, however, the woven fabric can also have a more complex form, for example be a multilayer construction with interconnected layers of fabric, a box structure or honeycomb structure, etc.

[0046] Furthermore, any other textile, for example a knitted textile, a felt, a braid, etc., can be used in place of the woven fabric.

LIST OF REFERENCE SYMBOLS

[0047] 10 Device

[0048] 12 Assembly unit

[0049] 13 Weaving machine

[0050] 14 Fixing unit

[0051] 16 Shaping unit

[0052] 17 Manipulator

[0053] 18 Activation unit

[0054] 20 Punch

[0055] 21 Gripper

[0056] 22-24 Arrows

[0057] 30 Sequence of operations

[0058] 32 Method step: textile processing (production of textile structure)

[0059] 34 Method step: shaping

[0060] 36 Method step: binder activation

[0061] 50 Fiber material

[0062] 52, 52′ Molded body made of fiber material

[0063] 54 Textile structure

[0064] 54′ Woven fabric

[0065] 55 Warp threads

[0066] 56 Weft threads

[0067] 58 Domelike curves

[0068] 60 Area after leaving the weaving machine (slack)

[0069] 62 Fixed area of the woven fabric