Method and mold for infusing a matrix material

Abstract

Method for infusing a matrix material into a fiber material for the production of a fiber composite component by winding, comprising the steps: a) providing a molding tool which is designed as a liner and which has a tool surface in which infusion openings are provided which are pressure-tightly connected to a matrix material reservoir; b) winding the fiber material onto the tool surface of the forming tool; c) Infusing the matrix material into the fiber material wound onto the forming tool by forcing the matrix material from the matrix material reservoir out of the infusion openings provided in the tool surface with an infusion pressure in the direction of the wound fiber materials, wherein the forming tool is provided as a liner with a tool surface that runs circumferentially in at least one direction and in which the infusion openings are provided, which are connected to the matrix material reservoir via internal pressure-resistant connecting elements, wherein the fiber material is wound continuously circumferentially onto the tool surface, characterized in that the forming tool is provided with an elastic tool surface in which the infusion openings are provided and which borders on an internal cavity that can be subjected to an internal overpressure, wherein before,During or after the winding of the fiber material onto the elastic tool surface, the cavity is subjected to an internal overpressure and the matrix material is pressed out of the infusion openings in the elastic tool surface by the matrix material reservoir with an infusion pressure that is greater than the internal overpressure to which the cavity of the mold is subjected.

Description

The invention relates to a method and a mold relating thereto for infusion of a matrix material into a fiber material for the production of a fiber composite component according to the preamble of main claims 1 and 6.In the production of fiber composite components, a matrix material infused into a fiber material is generally cured by tempering the component, so that the fiber material embedded in the matrix material together forms an integral component. In particular in the fiber direction, the highest demands on strength and rigidity are thus obtained, while the component itself has a very low weight compared to conventional materials.In the production of fiber composite components by the so-called injection or infusion method, dry fiber material is deposited on a molding tool having a molding tool surface, which usually has at least partially the later component shape. With the aid of a pressure difference, for example by applying an overpressure to the matrix material or creating a vacuum in the region of the fiber materials (vacuum injection method), the matrix material is now infused into the dry fiber material that has been introduced into the molding tool. After complete impregnation of the fiber material, the matrix material can be cured by tempering and optionally pressurizing the fiber material, and the fiber composite component can thus be produced.An important process or quality parameter in this case is the fact of complete impregnation of the dry fiber material with matrix material. This is because regions which are not completely impregnated with matrix material represent a defect in the later produced fiber composite component, which degrades the component quality and can impair the strength and rigidity of the component. Especially in the case of fiber composite components in safety-critical application areas, such as, for example, in the case of rotor blades or in the case of pressure tanks, this quickly leads to waste of the complete component, which increases the production costs and thus ultimately the unit prices.In particular, thick-walled structures in the area of the banding of rapidly revolving rotors require high tangential prestresses of the fiber material in order to be able to introduce targeted radial tension gradients into the bandage. This makes it difficult to impossible to deposit already preimpregnated fiber materials, so that predominantly dry fiber material is deposited, which must later be infused with a suitable matrix material.For both the wet and dry winding processes, yarn tensions of up to 100 MPa are used. This leads to fiber volume contents of up to 70% by volume. During curing, particularly in the case of so-called ring windings, microbends (buckling of the fiber material in the event of resin shrinkage) occur at almost regular intervals in the circumferential direction and per thread width, which lead to delaminations, particularly in the case of centrifugal force loading and high internal overpressure in pressure vessels, which delaminations reduce the strength and the service life of rotors. In addition, the ring windings suffer a prestressing loss of up to 30%, at lower fiber contents, especially in the case of wet-wound structures. This can lead to fiber misalignment and fiber ripple, especially in the case of thick-wall structures, which lead to undesirable and difficult-to-tolerate dynamic imbalance, especially in the case of rotors.In the case of thick-walled structures and / or pressure vessels produced by the dry winding process, the resin infusion is carried out by means of vacuum infusion processes with and without autoclave support from the outside to the inside. In the absence of pressure-stable exterior tools, the maximum pressures with which the resin system can be pressurized are limited to atmospheric pressure and autoclave pressure (autoclaves with a total pressure of 15 bar are known). At higher fiber volume contents, it is not always possible, especially in the case of thick-walled rotors and in the cylindrical regions of pressure vessels, regardless of the sprue concept, to completely impregnate the fiber material. Incomplete impregnation, however, always leads to waste parts, so that an enormous cost penalty is associated with this, in particular for pressure vessels produced in series.In rotors and pressure vessels made of fiber composite materials, large or exclusive portions of so-called ring windings are always present, which ideally have a thread start and exactly one associated thread end. Therefore, resin infusion over open fiber cross sections is not possible, since the running distance in a capillary is usually more than one kilometer. Owing to the high packing density of the fibers, autoclave-assisted infusion is usually not possible, since the flow resistance due to the filaments lying on all sides on block is too high and is additionally increased by the application of external pressure. This applies in particular to thick-walled structures.DE 198 59 798 C2 discloses a method and a device for producing molded bodies from fiber composite materials, in which the fiber material is deposited on a mold and closed with a pressure bell, wherein starting from the pressure bell, matrix material is then infused into the fiber material.EP 2 653 296 A1 discloses a vacuum infusion method for producing a wind turbine component, in which the matrix material is infused into the fiber material through an opening in the shaping tool surface.DE 10 2012 023 608 A1 discloses a method and a device for producing a molded part, in which fiber material is inserted into a multipart mold, at least one side of the multipart mold being flexible in order to be able to better distribute the infused matrix material.DE 10 2007 027 755 A1 discloses a method for producing a fiber-reinforced plastic component, in which the fiber material is wound onto a hollow core and then inserted into a multipart tool mold. The matrix material is then infused into the fiber material from the outside.DE 101 40 166 A1 discloses a method and a device for producing fiber-reinforced components by means of an injection method, in which the fiber material is placed in a tool and sealed off in an airtight manner with a vacuum film, the matrix material then being infused into the fiber material from the outside.Finally, DE 10 2011 082 842 A1 discloses a method for producing structural components in which fiber material is inserted into a multipart mold and then infused with matrix material from the outside.US 2010 / 0310886 A1 discloses a hat-shaped or cup-shaped molding tool, on the inner wall of which a fiber material can be deposited for producing a fiber composite component. The mold can be closed with a cover.Furthermore, DE 101 06 923 A1 discloses a method for producing components made of fiber-reinforced plastic, wherein an inner tool and an outer tool are provided, between which fiber material can be deposited in a winding process. The fiber material can be infused with matrix resin from the inside to the outside.EP 0 295 819 A2 discloses a tool core which consists of four separate tool surfaces which can be supplied with matrix resin via internal infusion lines.DE 10 2010 051 739 B3 discloses a method and a device for producing cylindrical large structures, wherein an inner tool and an outer tool are also provided here, between which the fiber material is arranged in the winding process, wherein the outer tool is sheathed with steel cables in order to press the outer tool onto the inner tool with the fiber material being interposed.DE 10 2007 060 029 A1 discloses a flexible tool core which can be subjected to a pressure and can thus generate a radially acting force. According to the production method there, this is a type of pressure bellows with which the fiber material is pressed against an inner wall of a tubular forming tool. The aim of this method is to produce a smooth and true-to-shape outer surface of a hollow fiber composite body.Against this background, it is an object of the present invention to specify an improved method for infusion of matrix material into a wound-up fibre material, in particular in the case of rotor bandages and pressure vessels, with which a complete infusion of the matrix material and by impregnation of the fibre material can be ensured. It is also an object of the present invention to provide an improved device for this purpose.The object is achieved according to the invention by the method according to claim 1 and the apparatus according to claim 6.According to claim 1, a method for infusion of a matrix material into a fiber material for the production of a fiber composite component is proposed, wherein in the first step it is provided that a molding tool is provided which is designed as a liner and which has a tool surface in which infusion openings are provided. These infusion openings are connected pressure-tightly to a matrix material storage reservoir, so that matrix material can be forced out of the matrix material storage reservoir from the infusion openings provided in the tool surface.In the next step, the fiber material is then wound onto the tool surface of the forming tool, namely in particular in such a way that at least a part, preferably all infusion openings in the tool surface are covered by the fiber material after completion of the winding of the fiber material, i.e. the fiber material is laid over the infusion openings. The winding of the fiber material can be automated by a fiber laying device or manually.After the fiber material has been completely wound up on the tool surface in such a way that at least a part of the infusion opening in the tool surface is covered by the wound-up fiber material, the actual infusion process for producing the fiber composite component now takes place. For this purpose, the matrix material located in the matrix material storage container is conducted through the pressure-tight connection to the infusion openings with the aid of a pump or pressure device and forced out of the latter, so that the matrix material infuses the fiber material wound up via the infusion openings from the direction of the molding tool.For this purpose, the molding tool can be introduced into an autoclave, for example, wherein the fiber material is pressed onto the molding tool by a pressure set in the autoclave. With a corresponding infusion pressure, the matrix material can now be forced out of the matrix material storage reservoir from the infusion openings of the tool surface in order to infuse the fiber material, wherein due to the autoclave pressure the fiber material is pressed onto the tool surface despite the infusion pressure.Before the fiber material is wound onto the tool surface of the forming tool, a flow aid is advantageously placed over the infusion openings, onto which the fiber material is then wound. This can ensure that the matrix material forced out of the infusion openings of the tool surface is spatially well distributed between the fiber material and the tool surface in order to infuse the wound fiber material completely and over the entire surface.After the matrix material has been forced out through the injection openings and the wound fiber material has been completely impregnated with the matrix material, the curing process can begin, for example, by exposure to temperature. In this case, the matrix material infused into the fiber material is cured, so that the matrix material and the fiber material form an integral unit and the fiber composite component with its advantageous properties is thus produced.In a further advantageous embodiment, it is conceivable that a molding tool is provided which has a flow channel texture in the tool surface next to the infusion openings, so that a plurality of flow channels are produced. As a result, the matrix material can be distributed very well under the fiber material and thus increase the probability of complete impregnation of the fiber material.With the aid of the present invention, it is thus possible to let matrix material infuse completely into the fiber material into a fiber material wound onto a tool, even if, due to the deposition method or production method used, the fiber material is wound onto the tool with a high pressure or the fiber material has a very high fiber volume content, which makes it difficult in principle to infiltration matrix systems.According to a particularly advantageous embodiment, the infusion pressure at which the matrix material is forced out of the infusion openings is adjusted such that the infusion pressure is greater than the contact pressure at which the fiber material rests on the tool surface. Such a contact pressure can be set, for example, by the fiber material being pressed onto the tool surface on account of an autoclave pressure. Such a contact pressure can also be set by the fiber material being laid under tension in winding technology, so that, due to the set tangential thread tension, the fiber material lies on the tool surface over the full surface with a corresponding contact pressure.At an infusion pressure which is greater than the support pressure, the matrix material is now forced out of the infusion openings, wherein the forced-out matrix material expands the fiber layers of the fiber material and in particular the capillaries between the filaments and thus distributes itself over the surface between the fiber material and the molding tool. In this case, the fiber material is infused by the matrix material successively radially from the inside to the outside against a generally uniform flow resistance. The effect of the distribution of the matrix material can be improved by a corresponding flow channel structure, for example in the form of a flow aid or milled flow channels.According to the invention, a molding tool is provided with a tool surface which runs in at least one direction and in which the infusion openings are provided radially around the circumference of the molding tool, wherein the infusion openings are connected to the matrix material storage reservoir via internal pressure-resistant connecting elements. Such a circumferential tool surface can be, for example, a so-called liner, with which hollow components are produced from a fiber composite material, for example rotor blades or pressure tanks. These so-called liners, which have a circumferential tool surface in at least one direction, are now wound around with fiber material, for example by the molding tool rotating about a corresponding axis and thus the circumferential tool surface executing a circular movement. The fiber material is then likewise laid circumferentially, in particular continuously circumferentially. In this case, it is particularly advantageous if the matrix material is then forced out of the infusion openings with a higher infusion pressure than the fiber material rests on the tool surface. The pushing out of the matrix material thereby becomes a widening of the circumferentially laid fiber materials, whereby an infusing of the matrix material into the continuously circumferentially laid fiber material is effected.Advantageously, a forming tool is provided at the lateral delimitation of which so-called winding shoulders are provided on the circumferential tool surface in order to thus set the lateral pressure-resistant outer side with a rigid dimensioning corresponding to the expected transverse forces from the winding process, so that the outer pressure-resistant tool side on all sides is also provided together with the fiber material for rotor bandages.Furthermore, according to the invention, a molding tool with an elastic tool surface is provided, in which the infusion openings are provided, wherein the elastic tool surface adjoins an inner cavity, which can be subjected to an internal overpressure. Before, during or after the fiber material is placed on the elastic tool surface, the cavity is subjected to an internal overpressure, wherein the matrix material is forced out of the infusion opening present in the elastic tool surface by the matrix material storage reservoir at an infusion pressure which is greater than the internal overpressure with which the cavity of the mold is subjected.It is thus conceivable that a slight internal overpressure is provided before the fiber material is laid, in order to sufficiently stabilize the molding tool with the elastic tool surface for fiber laying.Due to the fact that the infusion pressure is greater than the internal overpressure of the cavity of the mold, when the matrix material is pushed out of the infusion openings, the elastic mold surface deflects from the infusion pressure, so that a gap is formed between the fiber material and the elastic mold surface, in which the matrix material can spread for infusing the fiber material.In this case, it is particularly advantageous if, after the fiber material has been wound up, the cavity is subjected to an internal overpressure in order to thus increase the contact pressure in that the fiber material rests on the tool surface. This makes it possible to achieve an increase in the fiber volume content, wherein irregularities in fiber deposition can be eliminated at the same time. An internal overpressure can be applied up to the design load of the fiber materials in the cavity, wherein due to the again increased infusion pressure, a complete infusion of the fiber material with matrix material can nevertheless be achieved.For this purpose, it is particularly advantageous if, after a predetermined amount of matrix material has been pushed out of the infusion openings, the pressure difference between the infusion pressure and the internal pressure is eliminated in order to thus allow the pushed-out matrix material to infuse into the fiber material, wherein, after a predetermined period of time has elapsed, the pressure difference between the infusion pressure and the internal pressure is increased again until the infusion pressure is again greater than the internal pressure. The setting of a pressure difference can be effected, for example, by the infusion pressure being increased or the internal pressure of the cavity being lowered. To eliminate the pressure difference, the infusion pressure may be lowered to substantially the internal pressure of the cavity or the internal pressure of the cavity may be raised to substantially the infusion pressure.Such a stepwise infusion is necessary, for example, at flow rates which are too low in order to avoid container instability in the case of excessively large deformations of the molding tool.A further advantage of the elastic tool surface is that by evacuation of the mold after curing of the matrix material has taken place, the mold can be removed from the container with a sufficiently dimensioned pole opening. It is thus conceivable, for example, for a molding tool to be provided which has an elastic tool surface made of a PE material, as a result of which the possible use of an elastic winding or molding core for the production of fiber composite structures is possible. The mould core can be about 1 m in diameter and about 3 m in length and can consist, for example, of a PE material 4 mm to 5 mm thick, which can be produced, for example, by a simple rotomoulding process. For sufficient stabilization of such a molding tool, the molding or winding core is subjected to an internal overpressure of about 100 mbar, which is sufficient for a corresponding fiber deposition.When using PE material, the mold can furthermore be melted in to demold a winding or forming core and the melt can be discharged. A prerequisite for this is the use of a low-temperature crosslinked resin system which reaches its final strength at temperatures far above the melting temperature of the material used for the molding tool, so that melting of the molding tool becomes possible.An elastic tool surface as a molding tool also serves as an ideal forming element in the production process. In contrast to solid, dimensionally stable winding tools, contour imperfections and other geometric imperfections of the tool surface can be corrected with elastic tool surfaces after fiber deposition has taken place. This is effected by simply applying pressure to the components produced with pressures up to the design load of the fiber material. Deformations of the forming tool are formed here, which arise from the displacement of non-precise, geodetically laid fiber material and non-isotensoidally embodied outer contour of the forming tool in the so-called bottom regions of the container. The deformed container structure produced in this way represents almost the optimum with regard to the maximum load capacity of the fiber composite structures.According to a further advantageous embodiment, the matrix material is forced out of the infusion openings by means of a hydraulically generated infusion pressure, whereby substantially higher infusion pressures can be set than in conventional methods.In addition, the invention is also achieved with a device for producing a fiber composite component from a fiber material infused with a matrix material, wherein the device has a molding tool as a liner with a tool surface, in which one or more infusion openings are provided, which are connected in a pressure-proof manner to a matrix material storage reservoir. In addition, the device has a pressurizing device which is designed for pushing out the matrix material from the matrix material storage reservoir from the infusion openings in the direction of deposited fiber materials at a predetermined infusion pressure, wherein the molding tool has a tool surface which runs around in at least one direction and in which the infusion openings are provided, wherein the infusion openings are connected to the matrix material storage reservoir via internal pressure-resistant connecting elements, wherein the molding tool has an elastic tool surface in which the infusion openings are provided, wherein the molding tool furthermore has an internal cavity which adjoins the elastic tool surface and is designed for application with an internal overpressure in order to increase the contact pressure of deposited fiber material.Advantageous embodiments of the device are found in the corresponding dependent claims.The invention is explained by way of example with reference to the figures. The following are shown: FIG. 1 is a schematic illustration of a side view of a winding tool; FIG. 2 shows a sectional view of the schematically illustrated winding tool according to FIG. 1 ; FIG. 3 shows a schematic illustration of a liner for producing pressure vessels.FIG. 1 shows schematically in a lateral view a forming tool 1 which has a tool surface 2 running around in at least one direction as a winding tool. The forming tool 1 can rotate about an axis 3 or shaft, so that the surface 2 performs a rotational movement. In this way, fiber material can then be laid circumferentially on the surface 2 of the tool. For lateral support, so-called winding shoulders 4 are provided, which bring about a lateral limitation of the fiber material to be deposited on the surface 2.FIG. 2 schematically shows the winding tool 1 of FIG. 1 from a 90° rotated angle of view, namely in a plan view of the tool surface 2. according to the invention a plurality of infusion openings 5 are provided in the tool surface 2, all of which are connected to a matrix material storage tank 7 via a pressure-tight connection 6.With the aid of a pressurizing device 8, the matrix material 9 contained in the matrix material storage tank 7 can be forced out of the infusion openings 5 of the tool surface 2 via the pressure-tight connection 6, so that a fiber material 10 deposited on the tool surface 2 can be infused with the matrix material 9 radially from the inside to the outside. FIG. 2 shows the fiber material 10 deposited on the tool surface 2 in a sectional illustration, in order to thus make it possible to see the tool surface 2.Preferably, the infusion pressure at which the matrix material 9, for example a resin system, is forced out of the infusion openings 5 should be greater than the contact pressure of the fiber material 10.Before the fibrous material 10 is deposited on the tool surface 2, a coarse fabric can preferably be placed under it as a flow aid, in order to be able to distribute the matrix material pressed out of the infusion openings 5 between the fibrous material 10 and the tool surface 2 in a good planar manner, in order to reliably achieve complete impregnation of the fibrous material 10. It is also conceivable for corresponding flow channels (not shown) to be milled into the tool surface 2, by means of which flow channels the matrix material is initially distributed on the tool surface 2 and then, on account of the injection pressure, then infused into the fiber material.FIG. 3 schematically shows a liner 15 for producing a pressure vessel from a fiber composite material. The liner 15 has a pole opening 11 on one side, through which the sprue lines for infiltration of the matrix material are guided into the interior of the liner 15. On the other side, the liner 15 has a pole opening 12 with which a medium pressure can be applied to the cavity 13 of the liner. As a result, for example, a flexible tool surface 14 can be stabilized for the purpose of depositing the fibers or brought to the maximum design load of the deposited fiber materials.After the fiber material 10 has been deposited in an annular winding, the matrix material 9 is guided to the flexible tool surface 14 via the pressure-tight connection of the pole opening 11, wherein here matrix material 9 is pressed out of corresponding infusion openings and distributed between the flexible tool surface 14 and the fiber material 10. If the cavity 13 is pressurized, it is sufficient if the matrix material is forced out of the infusion openings with a slightly increased infusion pressure, so that the resin is distributed between the flexible tool surface 14 of the liner 15 and the laid-down fiber material 10. For this purpose, the flexible tool surface 14 can be textured, for example, so that small resin channels are formed on the tool surface, through which the fiber material can be distributed on the flexible tool surface.

Claims

Method for infusion of a matrix material into a fibre material for the production of a fibre composite component in the winding process, comprising the steps: a) providing a moulding tool which is designed as a liner and which has a tool surface in which infusion openings are provided which are connected in a pressure-proof manner to a matrix material storage reservoir; b) winding the fibre material onto the tool surface of the moulding tool; c) infusing the matrix material into the fibre material wound onto the moulding tool by the matrix material storage reservoir being forced out of the infusion openings present in the tool surface with an infusion pressure in the direction of the wound fibre materials, wherein the moulding tool is provided as a liner having a tool surface which runs around in at least one direction and in which the infusion openings are provided, The invention provides a method for continuously winding the fiber material on the tool surface in a continuously circumferential manner, wherein the mold is provided with an elastic tool surface in which the infusion openings are provided and which adjoins an inner cavity which can be subjected to an inner overpressure, wherein before, during or after winding the fiber material on the elastic tool surface the cavity is subjected to an inner overpressure and the matrix material is forced out of the infusion openings present in the elastic tool surface by the matrix material storage with an infusion pressure which is greater than the inner overpressure which is applied to the cavity of the mold.Method according to claim 1, characterised in that the infusion pressure at which the matrix material is forced out of the infusion openings is greater than or equal to the contact pressure at which the fibre material rests on the tool surface.Method according to one of the preceding claims, characterized in that after the fiber material has been wound up, the cavity is subjected to an internal overpressure, so that the contact pressure with which the fiber material rests on the tool surface is increased.Method according to one of the preceding claims, characterized in that after a quantity of matrix material has been pushed out of the infusion openings, the infusion pressure is lowered to the internal pressure of the cavity or the internal pressure of the cavity is raised to the infusion pressure in order to let the pushed-out matrix material infuse into the fibre material, wherein after a period of time has elapsed the infusion pressure is raised again or the internal pressure of the cavity is lowered again until the infusion pressure is again greater than the internal pressure.Method according to one of the preceding claims, characterized in that the matrix material is pushed out of the infusion openings by means of a hydraulically generated infusion pressure.Device for producing a fibre composite component from a fibre material infused with matrix material in the winding process, wherein the device has a moulding tool as a liner with a tool surface on which fibre material can be wound, wherein one or more infusion openings are provided in the tool surface, which are connected in a pressure-tight manner to a matrix material storage store, wherein a pressurization device is provided which is designed for pushing out the matrix material storage store from the infusion openings in the direction of wound-up fibre materials at a predetermined infusion pressure, wherein the moulding tool has a tool surface which extends all around in at least one direction and in which the infusion openings are provided, wherein the infusion openings are connected to the matrix material storage store via internal pressure-tight connection elements, characterized in that the moulding tool has an elastic tool surface in which the infusion openings are provided, wherein the molding tool further comprises an inner cavity adjoining the elastic tool surface and configured to be acted upon by an inner overpressure in order to increase the contact pressure of deposited fiber material.The device according to claim 6, characterized in that the device comprises a hydraulic pressurizing device, which is configured to generate a hydraulic infusion pressure for pushing out the matrix material from the infusion openings.

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