Multilayered hollow body made of a textile composite

Abstract

The invention relates to a hollow body, in particular for a mast, pile or tube, comprising at least one hollow-profile-shaped main body with at least two layers adjoining one another, at least one of which is a textile layer containing natural fibres selected from the group comprising bast fibres, leaf fibres or fruit fibres, wherein at least one of the layers is impregnated with a matrix material, the hollow body being characterized in that at least the textile layer contains a sheet-like textile formation, in particular a woven or knitted fabric and / or felt, and also relates to a method for producing such a hollow body.

Description

[0001] Multilayer hollow body made of textile composite

[0002] The present invention relates to a hollow body, in particular for a mast, pillar, or pipe, comprising at least one hollow profile-shaped base body with at least two adjacent layers, at least one of which is a textile layer containing natural fibers selected from the group of bast fibers, leaf fibers, or fruit fibers, wherein at least one of the layers is impregnated with a matrix material. The invention also relates to a method for producing such a base body.

[0003] Materials such as steel, concrete, or reinforced concrete are often used to construct overhead power line pylons, such as those for high-voltage or medium-voltage grids. However, the production of solid or hollow-section components made of steel and / or concrete requires a high level of energy. Furthermore, the dismantling and recycling of such components, and the associated disposal of the materials, can be relatively costly and environmentally harmful.

[0004] Wood can be a more environmentally friendly alternative material. However, the use of wood is disadvantageous given the increasing global demand. Wooden poles also have comparatively limited load-bearing capacity. Furthermore, environmentally harmful impregnation agents are regularly used to protect wooden poles from negative environmental influences.

[0005] US 2008 / 0274319 A1 discloses a multilayer hollow body made of a composite material, which can be produced using a fiber winding process and can be used, for example, as a mast or tube. The hollow body has an inner core and one or more layers wound around the core. The core and the layers are formed from a polyurethane resin and a reinforcement impregnated with the resin. The reinforcement can, for example, comprise fibers, particles, flakes, or fillers made of glass, carbon, or aramid, as well as plant-based materials such as jute or sisal.

[0006] WO 2020 / 160603 A1 discloses a multilayer material that can be used to produce a hollow profile-shaped body in a winding process. The material has a base layer made of paper, cardboard, or a solid polymer made of a natural, particularly plant-based, material, and a layer applied thereto made of a flowing, liquid, or molten natural polymer that bonds to the base layer and hardens. In one disclosed embodiment, the multilayer material can, for example, comprise an outer and an inner layer made of a natural material, a base layer made of paper or cardboard, and a woven layer, wherein the woven layer can comprise, among other fibers, jute, hemp, or sisal.In addition, a layer of a liquid, natural polymer can be arranged between the woven layer and the base layer, which combines with the other layers and causes the curing and solidification of the material or the hollow profile-shaped body.

[0007] The object of the present invention is to provide a hollow body of the type mentioned above which has high strength, is lightweight and environmentally friendly and is suitable for various uses.

[0008] This object is achieved with a hollow body according to claim 1 in that at least the textile layer contains a sheet-like textile structure, in particular a woven, knitted, and / or felted fabric. Preferred embodiments of the hollow body according to the invention are evident from the features of the subclaims.

[0009] A layer is defined by the fact that it can be produced with one or more components, in particular material webs, wherein the multiple components are then already present before the formation of the layer in the composition in which they are used for the production of the layer.

[0010] The base body comprises at least one textile layer which has a sheet-like textile structure.

[0011] The textile layer contains natural fibers. Natural fibers are typically differentiated according to their origin and can be of plant or animal origin. According to the invention, bast fibers, leaf fibers, or fruit fibers—i.e., comparatively thick natural fibers of plant origin—are used. They are characterized by high natural stiffness, which promotes the strength of the hollow body. These natural fibers also easily absorb liquids such as a liquid matrix material or a dye, by means of which the properties of the base body can be influenced. Seed fibers, such as cotton fibers, which also fundamentally belong to the natural fibers of plant origin, are not important for the hollow body according to the invention and, if at all, are contained in the textile layer only in minor quantities.

[0012] According to the invention, the textile layer comprises a sheet-like textile structure made of fibers or threads produced therefrom, which are preferably formed into a sheet-like textile structure by crossing or interlacing or looping. The sheet-like textile structure is capable of very effectively absorbing forces both in the longitudinal direction of the base body and transverse to it. Thus, the textile layer primarily functions as reinforcement and thus significantly influences the strength properties of the hollow body.

[0013] Impregnating at least one of the layers with a matrix material contributes to improved force transfer between the layers. The matrix material thus creates a bond between the adjacent layers. The matrix material creates a bond between the interior of one of the adjacent layers and at least the surface of the adjacent layer. Impregnation, i.e., soaking at least one of the layers with the matrix material, allows loads to be transferred relatively effectively from one layer to the adjacent layer, unlike with adhesive bonding, where only the surfaces of the layers are bonded together.Of course, it's advantageous if not just one of the layers, but both adjacent layers are impregnated with the matrix material, so that the matrix material completely bonds the fibers of both adjacent layers, thus creating an even deeper bond between the adjacent layers. At the same time, impregnation with the matrix material can stiffen a layer, thus increasing its strength.

[0014] In addition, the matrix material provides protection for both the impregnated layer and the surface of the adjacent layer against external environmental influences.

[0015] As a result, the hollow body according to the invention, with at least one hollow profile-shaped base body, which is constructed in multiple layers in the sense of a composite material, has a low dead weight and high strength both in the longitudinal direction and in the transverse direction. The hollow body according to the invention also has good elastic properties. Thus, a base body with the layered structure according to the invention can have a modulus of elasticity of 10,000 N / mm 2 or more can be easily realized.

[0016] The multi-layer structure makes it possible to create hollow bodies through the appropriate selection and combination of individual layers, whose strength, elasticity, weight, and size are tailored to a specific requirement profile. The hollow body can also consist of several, possibly different, base bodies, whereby the base bodies can be connected to each other, for example, in the longitudinal direction or transversely to each other.

[0017] In a particularly preferred embodiment of the invention, the textile structure is a woven fabric. A woven fabric comprises at least two thread systems arranged essentially perpendicular to each other, which allows it to withstand high tensile forces acting in one direction of at least one of the thread systems. The use of a woven fabric contributes significantly to the strength of the hollow body.

[0018] Furthermore, the textile structure can also, but not exclusively, be a warp-knitted fabric, a knitted fabric, and / or felt. The felt can, for example, contain a woven, knitted, or warp-knitted structure or be formed from one.

[0019] Where appropriate, the individual layers can be made of different materials. For example, a layer can contain one or more metal reinforcements, which are incorporated into, inserted into, or attached to the textile structure.

[0020] The hollow bodies according to the invention are particularly suitable for the construction of overhead power line masts, lampposts, or wind turbine masts. Use as a chimney or pillar of a supporting structure of a building is also conceivable. Use as a pipe for fluid media of different pressure levels is also possible. For this purpose, the base body of the hollow body can, for example, have an inner protective layer that seals an interior of the base body to the outside, preventing a fluid medium from escaping to the outside or protecting the fluid medium from undesirable external influences.

[0021] The hollow body according to the invention can be manufactured with comparatively low energy consumption and simplicity thanks to the multi-layer structure of the base body, while the use of natural raw materials results in low material costs and high environmental compatibility. Furthermore, due to its low weight, the hollow body is significantly easier and more cost-effective to transport than comparable components made of steel, concrete, or wood. Not only is the transport effort significantly lower due to the weight advantage, but the need for a crane for loading and unloading a transport vehicle, as well as for erecting masts or pillars made from the hollow body according to the invention, is also eliminated.

[0022] The base body preferably has at least one supporting layer. The supporting layer serves, among other things, to evenly transfer the forces acting on the base body to adjacent layers within the base body. In particular, the supporting layer can be designed such that it has a large contact area with at least one adjacent layer whose fibers or threads are comparatively thick or coarse. This is particularly advantageous when the supporting layer is arranged between two textile layers. If the textile layers were directly adjacent to one another, they would have only a comparatively small contact area due to the interlacing or crossing of the filaments of the textile structure, which would allow for lower forces to be transferred between them.However, if the contact area is maximized by a support layer to each of these two layers, significantly higher forces can be transferred between the layers, allowing higher shear forces to be dissipated within the base body. Even if the support layer is only adjacent to one textile layer, it ensures a more even distribution of forces within the textile layer.

[0023] In a preferred embodiment of the hollow body according to the invention, the base body has at least two textile layers and at least one support layer for increased strength, wherein at least one support layer is arranged between two adjacent textile layers to improve force transmission between the layers. For particularly high strength, the base body can in particular have at least three textile layers and at least two support layers. Of course, the base body can also comprise a higher number of textile layers and support layers. Preferably, the base body comprises exactly three textile layers and two support layers, wherein a support layer is arranged between two textile layers, for example when the aim is to provide a hollow body with the load-bearing capacity of a wooden pylon for medium-voltage or telecommunications networks.

[0024] If the base body has two or more textile layers, it is possible for only one of these textile layers to contain a sheet-like textile structure, while other textile layers are formed, for example, by wound filaments. However, to further increase the strength of the hollow body, at least two textile layers, or preferably all textile layers, can contain a sheet-like textile structure. All textile layers can have the same textile structure. Likewise, the textile structure can be at least partially different in at least one textile layer.

[0025] Furthermore, it is preferred if at least one and preferably all support layers contain a sheet-like textile structure. All support layers can have the same textile structure. Likewise, the textile structure in at least one further layer can be at least partially designed differently. The textile structure of one or more support layers can also be the same or different from the textile structure of a textile layer. The textile structure of the support layer(s) is particularly preferably a nonwoven. Less preferred, but equally possible, is the use of paper or cardboard for a support layer. In order to form a large contact area with at least one adjacent layer, it is advantageous if the surface of the textile structure of the further layer is essentially closed, i.e. largely free of stitches or holes.

[0026] Preferably, the base body of the hollow body is formed at least partially from wound layers. At least one of the textile layers and / or the support layers can be wound; particularly preferably, all textile layers and / or all support layers are wound. The use of a known and proven manufacturing process, such as a winding process, ensures that the hollow body can be manufactured with high precision and reproducibility. It is also possible to largely automate the winding process, allowing the hollow body to be manufactured cost-effectively, with consistent quality, and with a high degree of error tolerance.

[0027] Furthermore, it is preferred if at least one outer textile layer is impregnated with a matrix material, so that the hollow body is protected against harmful environmental influences. An outer textile layer is a textile layer that is arranged closest to an outer surface of the base body or forms the outer surface. Preferably, the outer and one inner textile layer, and furthermore preferably all textile layers, are impregnated with a matrix material. An inner textile layer is a textile layer that is arranged closest to an interior space of the base body or forms a surface facing the interior space. Furthermore, it is preferred if at least one of the textile layers and at least one adjacent support layer, preferably all layers, are impregnated with a matrix material and these layers are connected to one another via the matrix material.Accordingly, one of the support layers, and preferably all support layers, is also preferably impregnated with a matrix material. Impregnation of all layers ensures that they are firmly bonded and that the hollow body exhibits high strength and a substantially homogeneous stress distribution, as well as good elastic properties, along its entire length and cross-section.

[0028] For use in a textile layer, jute fibers, kenaf fibers, hemp fibers, and flax fibers are particularly suitable as bast fibers; sisal fibers and abaca fibers are particularly suitable as leaf fibers; and coconut fibers are particularly suitable as fruit fibers. These natural fibers are generally environmentally friendly and available in large quantities. A textile layer can contain either exclusively fibers of one of the aforementioned fiber types or a combination of several of the aforementioned fiber types. For example, when using a woven fabric, the weft and warp threads can each consist of a different fiber type. One advantage of these fiber types is that they are very easy to impregnate. A base body made of solid or massive wood, on the other hand, can only absorb a matrix material comparatively superficially and in small quantities and therefore offers less protection against environmental influences and a shorter durability.

[0029] Sisal fibers are particularly preferred. Sisal fibers have the advantage of containing high levels of cellulose, lignin, and pectin, among other things, and therefore exhibit high tensile strength and stiffness. Furthermore, sisal fibers are naturally resistant to weathering. Sisal fibers also exhibit high resistance to microorganisms, which can be harmful, especially if the hollow body comes into at least partial contact with the soil. Sisal fibers are also inexpensive to obtain.

[0030] To further improve the environmental compatibility of the hollow body according to the invention, at least one of the and preferably all of the support layers can comprise at least natural fibers, but also synthetic fibers such as polyester fibers. The mass ratio of natural fibers to synthetic fibers can preferably be in a range from 2:1 to 1:2, particularly preferably 1:1. It is advantageous if at least one of the support layers comprises at least one carrier material and at least one wooden layer, whereby the strength of the hollow body can be increased. The carrier material and the wooden layer should preferably be firmly bonded to one another before production of the base body in order to prevent the wooden layer from breaking during bending or winding.The wood layer preferably has a thickness of at least 0.4 mm and at most 1.2 mm, in particular at least 0.6 mm and at most 1.0 mm, or particularly preferably at least 0.7 mm and at most 0.9 mm. The wood layer can be a veneer, and the carrier material can be a nonwoven. Furthermore, support layers with two, three, or more wood layers are also possible.

[0031] The matrix material of the hollow body can preferably contain a resin, in particular a phenolic resin, but also water glass or a comparable material. For improved environmental compatibility, the phenolic resin can optionally contain portions of a natural polymer such as lignin or be based entirely on a natural polymer. In addition to ensuring the appropriate strength properties of the hollow body, impregnation with a suitable matrix material also ensures, among other things, that the hollow body is resistant to microorganisms such as fungi, which can cause wood rot such as white rot or brown rot, particularly in soil, and to moisture. This means that the hollow body can be readily deployed and used as a mast or pillar, or as a component thereof, in soils. Furthermore, the hollow body can be exposed to low and high temperatures, for example, in a range of -30 to 100 °C.The hollow body is also largely UV-resistant due to the matrix material and can therefore be exposed to direct sunlight over a period of several years or decades without damage.

[0032] Depending on the use of the hollow body, the base body can, for example, have a circular, oval, rectangular, or polygonal cross-section. Regardless of the shape of the cross-section, the base body can also have a constant cross-section or a variable cross-section over its entire length, for example, a cross-section that tapers at least partially toward at least one of its ends.

[0033] In order to improve the force transmission between individual layers, in a further preferred embodiment of the hollow body, the base body has at least one connecting means which is suitable for engaging in at least one textile layer and / or support layer, so that at least two layers are directly or indirectly coupled to one another by the connecting means.

[0034] Suitable connecting materials can completely take over the function of a support layer and can therefore be used as an alternative.

[0035] The connecting means is preferably a metal strip, in particular a metal fabric strip, which is arranged in sections between two layers in the longitudinal direction of the base body. In this case, the metal strip has in particular at least one, but preferably a plurality of hook-like elements, which can, for example, protrude alternately at certain intervals towards one or each of the two sides of the metal strip and in this way can engage in a material structure of a layer adjacent to one of the two sides of the metal strip. Such a metal strip can, in particular, absorb shear forces occurring between the layers. Additionally or alternatively, the connecting means can also be incorporated into the sheet-like textile structure of a textile layer and / or support layer.

[0036] Clamps can also be used as connecting elements to join two or more layers. Joining two or more layers with clamps is not only useful for supporting the layers against each other, but also to ensure, in a manufacturing process, that the layers fit tightly together when a matrix material cures. The elastic properties and strength of the hollow body can be influenced by the choice of clamp type and the distribution of the clamps across the hollow body in the circumferential and longitudinal directions, and if necessary, also by their position in different levels of the layer composite. Clamps can also be distributed across different levels of the layer composite.So-called greenhouse clamps and, above all, multi-legged clamps such as three- or four-legged clamps with round or polygonal shapes are suitable, for example, with which a very strong press connection can be created between the layers to be joined.

[0037] Depending on the use of the hollow body, it may be useful for the base body to have a decorative layer as the outermost layer, which primarily serves to visually enhance the hollow body. A decorative layer can be particularly, but not exclusively, advantageous if the hollow body is used, for example, as a mast and is installed at least partially above ground. In addition, the decorative layer can also be designed to protect the hollow body from harmful environmental influences, for example. For example, the decorative layer can be formed from a varnish or a film. During production of the hollow body, the decorative layer can also prevent liquid matrix material from escaping from the hollow body to the outside before it hardens.

[0038] It is possible that the hollow body is exposed to different levels of load in different sections. It can therefore be useful for the base body to have at least one additional textile and / or support layer in at least one section along its longitudinal direction. In this way, the strength of the base body can be increased in certain sections in order to absorb different levels of forces at different points. For example, if the hollow body is used as a mast or pillar, it can be attached to the ground or a foundation at one lower end, which can result in higher forces occurring in this section than in other sections of the hollow body. It is also possible for higher forces to occur at the upper end of the mast if additional elements such as a crossbeam are attached there.By arranging additional layers only in sections, costs and weight can be saved compared to arranging such layers along the entire hollow body.

[0039] It can also be advantageous if the hollow body has at least one transponder that is set up to receive and send data. The transponder preferably does not require an external power supply. The transponder can, for example, be set up to store data about the respective hollow body, such as the date of manufacture, a serial number or the material composition, so that this data can be read out in the immediate vicinity during transport or in the case of an installed hollow body, or transmitted over a greater distance. Additionally or alternatively, the hollow body can have sensors and a storage unit for sensor data so that, for example, historical data on ambient temperature, humidity or dynamic loads can be stored. This means that the data can be used to determine whether or when the hollow body needs to be serviced due to wear or should be replaced.

[0040] To protect the hollow body from infestation by pests, especially termites, the base body can be provided with a biocide as a component of one or all layers, between two or more layers, or as an outermost layer. A base body for a hollow body according to the invention can preferably be produced using a method according to claim 20.

[0041] To carry out the process, known spiral winding machines can be used, for example, which are usually used to produce, among other things, tubular paper or cardboard tubes. For this purpose, material webs are continuously wound in a spiral around the longitudinal axis of a stationary winding mandrel, for example, to form one or more layers. The wound, formed layers rotate around the longitudinal axis of the winding mandrel by means of a drive such as a belt drive and can be moved along this axis. As a result of the rotation, the provided material webs are unwound from corresponding devices and continuously wound around the longitudinal axis of the winding mandrel, creating a hollow body in an endless process. Spiral winding processes are also known in which components are wound individually and not endlessly.

[0042] To produce a hollow-profile, multi-layered base body using the method according to the invention, material webs are wound spirally and at a constant angle around a longitudinal axis of a winding mandrel, forming a single layer. The material webs are wound in the order in which the layers of the base body are to be formed, from the inside out, with at least one material web of the innermost layer being wound first. The material web does not have to be wound directly onto the winding mandrel, but can, for example, be wound onto a mold or film enclosing the winding mandrel.

[0043] For the production of the hollow body, it is crucial that the at least one material web of a subsequent layer is not wound until the previous, adjacent layer has already been formed in the area in which the material web of the subsequent layer is wound around the longitudinal axis of the winding mandrel. This means that the material web of the previous layer must have been at least partially wound around the longitudinal axis of the winding mandrel in this area, depending on its width and the width of the material web of the subsequent layer, before the material web of the subsequent layer is wound. Using such a method, a multitude of different layers can be formed for a base body. The method according to the invention also makes it possible to change the size of the base body cross-section depending on the use of the hollow body.To ensure that the base body can develop the required strength properties, a matrix material is incorporated into at least one material web. This matrix material is designed to cure after winding the base body and bond all layers together. For example, the material web can be pre-impregnated in a process prior to the process and prepared and wound with partially cured matrix material as a so-called prepreg. In this case, the not yet cured matrix material can be liquefied before curing. Care must be taken to ensure that the prepreg contains only enough matrix material to allow it to be wound around the longitudinal axis of the winding mandrel without damage.Alternatively or additionally, it is possible for at least one layer, after only this or all layers of the base body have been wound, to be impregnated with a matrix material, for example by introducing the matrix material into the layers under pressure (e.g., pressure impregnation). It is also conceivable for one or all layers to be impregnated using a dipping process.

[0044] To increase the efficiency of the process, it is advantageous if one or more of the material webs for the textile layers are provided as prepregs. Particularly if not all material webs are provided as prepregs, it is advantageous if the prepregs are supersaturated with matrix material. In a process step after winding all material webs, the not yet cured matrix material in the prepregs is then liquefied so that it can diffuse from the prepreg layer(s) into neighboring layers whose material webs were not provided as prepregs, so that ultimately the entire base body is impregnated with the matrix material. For many applications, it will be necessary or at least advisable that all layers are impregnated with the matrix material and that the matrix material is cured at the end of the process.Depending on the requirements profile, it may be sufficient if only some of the layers, for example the innermost and / or the outermost layer, contain a cured matrix material.

[0045] To further increase process efficiency, it is advisable if the material web of a subsequent layer is wound essentially at the same time and in the same area as the material web of a previous layer. This means that the material web of a subsequent layer is wound immediately when the previous material web is sufficiently developed in the corresponding, common area. An insignificant time offset in the winding of the material webs occurs at most during start-up of the winding machine, when no material web has yet been wound. Preferably, all material webs are wound simultaneously in the same area. For this purpose, the material webs can be wound simultaneously, at least partially overlapping one another.

[0046] Preferably, the material web of one layer is wound parallel to the joint. This means that the edges of one turn are wound parallel to the edges of the adjacent turn, so that a continuous joint is formed in one layer. It is generally advantageous to wind a material web in such a way that the width of the joint is minimal. For the strength of the hollow body, it is advantageous if the material web of a subsequent adjacent layer is wound in such a way that it covers the joint formed in the previous layer. In particular, the material web can be aligned centrally to the joint so that it covers the joint evenly on both sides.

[0047] To ensure the required strength of the hollow body, at least one material web can be wound under tensile stress around the longitudinal axis of the winding mandrel, thereby building up a certain pressure within the base body that influences the strength of the consolidated hollow body. The tensile stress with which the material webs are wound can vary from material web to material web.

[0048] To prevent the material webs of the layers from separating from each other, at least one connecting element can be provided on at least one material web or between a previous layer and a subsequent layer. This connecting element is suitable for coupling the formed layers together in the sense of pre-strengthening before the matrix material hardens. It is essential that the connecting element is suitable for connecting the layers to each other in such a way that a pressure developed in the base body is maintained for a certain period of time, for example, until the matrix material hardens.

[0049] In particular, the bonding agent can be an adhesive, for example a so-called hot-melt adhesive, which is applied at least partially to the material web of a subsequent layer before winding, thereby bonding it to the previous layer. The adhesive can be applied to the material web in a serpentine pattern and at specific intervals.

[0050] Alternatively or in addition, a thread coated with an adhesive, such as a hot-melt adhesive, can be used as a connecting means. This thread is wound at specific intervals between two layers. Such a thread can also be incorporated into the textile structure of a layer. Before or immediately after winding, the adhesive in the thread is heated, which liquefies it and then hardens, so that the adjacent layers adhere to one another. It is essential that the adhesive is suitable for bonding two layers immediately after winding, so that they cannot separate from one another as soon as the tensile stress is no longer applied to the material webs.

[0051] In yet another alternative, a metal band, in particular a metal mesh band, can be used as the connecting means, which is designed to absorb shear forces occurring between two layers and thus prevent the layers from spontaneously detaching. For this purpose, the metal band can be provided with barbs on one or both sides that engage with the adjacent layer. The metal band can also be designed to hold adjacent layers together during winding and in the subsequent production process, so that the layers lie closely against one another, particularly during the curing of the matrix material. To achieve this, clamps such as greenhouse clamps and multi-legged clamps such as three- or four-legged clamps with round or polygonal shapes can be used as an alternative or in addition to this.

[0052] In a further embodiment of the method according to the invention, it is also possible for the pressure built up by the tensile stress on the material webs during winding in the base body to be secured with a sheathing layer. The sheathing layer can in particular be a film made of a synthetic polymer, for example a silicone-coated polyurethane film, and / or a nonwoven fabric, preferably a thread-reinforced nonwoven fabric, which can be removed again as required after the matrix material has hardened. The sheathing layer can also be designed such that, after being detached from the base body, it leaves behind a smooth, outer surface of the hollow body. The sheathing layer can also have a protective function against possible damage during transport or installation of the hollow body. In another embodiment, the sheathing layer can also remain a permanent component of the base body and serve, for example, as a decorative or protective layer.

[0053] In order for the at least one material web to be wound with a specific tensile stress, a counter-pressure body can preferably be formed from an innermost layer of the base body containing paper or cardboard. The innermost layer can preferably be wound around the longitudinal axis of the winding mandrel before the other layers. To ensure the required strength of the counter-pressure body, it can, for example, consist of several layers, with the individual layers being bonded to one another by an adhesive. It is essential that the innermost layer formed from the counter-pressure body has such high strength when the other material webs are wound under a specific tensile stress that it is not compressed by the applied tensile stress.The innermost layer of paper or cardboard also has the advantage that it can be easily removed from the winding mandrel without leaving any residue, preventing the winding mandrel from sticking to any of the remaining material webs. Depending on the use of the hollow body, the counterpressure body can remain in the base body after the process as a so-called permanent formwork or be removed from it.

[0054] Alternatively, a counterpressure body can also be formed, for example, by a support layer with at least one layer of wood as the innermost layer.

[0055] Especially when the counterpressure body remains as permanent formwork in the hollow body, but not only in such cases, it can be useful to connect the first and subsequent wound layers to the counterpressure body using fasteners such as the clamps described above. This can serve to stabilize the shape of the base body during curing by ensuring that the wound layers are not only in contact with each other, but also with the shaping counterpressure body. This can be advantageous not only when using pre-impregnated material webs (prepregs), but also when immersing the base body after all material webs of the base body have been wound.

[0056] Particularly in the case of immersion or pressure impregnation, the counter-pressure body also has the advantage that excess matrix material absorbed by the material webs can be specifically pressed out of the base body, for example by rolling using several rollers arranged around the base body, between which the base body is rotated.

[0057] During the production of the hollow body, gases can be generated, particularly when the matrix material hardens in the base body. To prevent damage to the base body from gases, at least the material forming the outermost and / or innermost layer of the base body can be permeable to such an extent that any gases generated can escape into the environment. For this purpose, for example, an inner paper or cardboard layer serving as a permanent formwork or a non-permeable cladding layer would have to be perforated. Care must be taken to ensure that liquid matrix material does not escape from the base body through the permeable layer.

[0058] Furthermore, it is preferred if the base body is wound in an endless process and cut to a specific, freely selectable length after the matrix material has hardened.

[0059] The matrix material of the impregnated material webs cures at a temperature suitable for the matrix material. The base body is exposed to the corresponding temperature for the entire duration, for example, in a convection oven. Depending on the matrix material, curing can additionally or alternatively be carried out using UV light. Furthermore, a uniform distribution of the matrix material in the base body can be promoted by rotating the base body around its longitudinal axis during curing using a suitable device, such as a so-called revolver drum.

[0060] In the following, possible embodiments of the hollow body are explained in more detail using figures.

[0061] It shows

[0062] Fig. 1a: the layer structure of a first embodiment of a hollow body according to the invention;

[0063] Fig. 1b: a cross-section of the hollow body of the first embodiment;

[0064] Fig. 2a: the layer structure of a second embodiment of a hollow body according to the invention;

[0065] Fig. 2b: a cross section of the hollow body of the second embodiment;

[0066] Fig. 3a: the layer structure of a third embodiment of a hollow body according to the invention;

[0067] Fig. 3b: a cross-section of the hollow body of the third embodiment; Fig. 4a: the layer structure of a fourth embodiment of a hollow body according to the invention;

[0068] Fig. 4b: a cross section of the hollow body of the fourth embodiment;

[0069] Fig. 5a: the layer structure of a fifth embodiment of a hollow body according to the invention;

[0070] Fig. 5b: a cross section of the hollow body of the fifth embodiment.

[0071] Figures 1a and 1b show a first embodiment of the hollow body 1 according to the invention, wherein Figure 1a schematically shows the structure of the individual layers and Figure 1b shows a section transverse to the longitudinal direction of the hollow body. The hollow body comprises precisely one base body 6 with a circular cross-section, which has an interior space 2 in the center, which is surrounded by several wound layers. As the innermost layer, the hollow body has a first textile layer 3, which contains a fabric as a flat, textile structure. The outermost layer is a second textile layer 4, which also contains a fabric. The fabric of the textile layers 3, 4 consists of sisal fibers and has a gross weight of, for example, 950 g / m 2and a thickness of, for example, originally 2.3 mm, although this can increase in an impregnated and cured layer. Between the first textile layer 3 and the second textile layer 4 there is a support layer 5 which contains a fleece with natural and synthetic fibers. All layers are each wound with a material web. In addition, the material webs of the layers are impregnated with a phenolic resin and bonded to one another to form the solidified base body 6. The thickness of the individual layers and the ratio of the layer thicknesses to the diameter of the interior space 2 are shown merely as examples and can be adapted as desired. Such a hollow body 1 can be used, for example, as a power or telecommunications mast.

[0072] Figures 2a and 2b show a second embodiment of the hollow body 1 according to the invention, which differs from the first embodiment in that the base body 6 has, as its innermost layer, a counter-pressure body 7 wound from cardboard, which remains in the base body 6 after its manufacture.

[0073] Figures 3a and 3b show a third embodiment of the hollow body 1 according to the invention, which differs from the first embodiment in that the base body 6 has a third textile layer 8 comprising a woven fabric and a second supporting layer 9 comprising a nonwoven fabric. In this case, one of the supporting layers 5, 9 is arranged between two textile layers 3, 4, 8. A hollow body 1 with such a layered structure has greater strength than the hollow body 1 of the first embodiment.

[0074] Figures 4a and 4b show a fourth embodiment of the hollow body xl according to the invention, which differs from the first embodiment in that the base body 6 has, as its outermost layer, a decorative layer 11 adjacent to the second textile layer 4. Furthermore, the base body 6 has, as its innermost layer, a protective layer 10 adjacent to the first textile layer 3, which is designed, among other things, to prevent a fluid medium from escaping from the interior 2. Such a hollow body can be used, for example, in civil engineering as a pipe for liquids or gases.

[0075] Figures 5a and 5b show a fifth embodiment of the hollow body 1 according to the invention, in which a metal fabric band 12 is arranged between the first textile layer 3 and the support layer 5, as well as between the second textile layer 4 and the support layer 5. Two rows of holes 13 are punched into the metal fabric band 12, at the edges of which several hook-like elements 14 protrude. Two holes 13 arranged one above the other in Figure 5a form a pair. The hook-like elements 14 of adjacent pairs protrude alternately to opposite sides of the metal fabric band 12. The hook-like elements 14 engage the adjacent layers and serve to absorb shear forces between the layers of the base body 6 during production before the matrix material hardens, so that the tensile stress in the layers is essentially maintained.The metal mesh band 12 does not have to extend completely along the length of the base body 6, but can only be inserted in sections, as indicated in Figure 5a.

[0076] The hollow body 1 according to the invention is not limited to the layer combinations shown in the exemplary embodiments, but can have any other layer combinations and number of layers. Reference numerals

[0077] Hollow body interior first textile layer second textile layer support layer base body counter pressure body third textile layer second support layer

[0078] Protective layer Decorative layer Metal mesh tape Holes Hook-like elements

Claims

Patent claims 1. Hollow body (1), in particular for a mast, pillar or pipe, comprising at least one hollow profile-shaped base body (6) with at least two layers, at least one of which is a textile layer (3, 4, 8) containing natural fibers selected from the group consisting of bast fibers, leaf fibers and fruit fibers or a combination thereof, wherein at least one of the layers is impregnated with a matrix material, characterized in that at least the textile layer (3, 4, 8) contains a planar textile structure, in particular a woven, knitted, crocheted and / or felted fabric.

2. Hollow body according to claim 1, characterized in that one of the at least two layers is a support layer (5, 9) adjacent to the textile layer (3, 4, 8).

3. Hollow body (1) according to claim 2, characterized in that the base body (6) has at least two textile layers and at least one support layer (5), wherein the support layer (5) is preferably arranged between the textile layers (3, 4).

4. Hollow body (1) according to claim 3, characterized in that the base body (6) has at least three textile layers (3, 4, 8) and at least two support layers (5, 9), preferably exactly three textile layers (3, 4, 8) and two support layers (5, 9), wherein a support layer (5, 9) is arranged between each pair of textile layers (3, 4, 8).

5. Hollow body (1) according to one of claims 3 or 4, characterized in that at least one and preferably all textile layers (3, 4, 8) contain a woven fabric as a planar textile structure.

6. Hollow body (1) according to one of claims 2 to 5, characterized in that at least one and preferably all support layers (5, 9) contain a planar textile structure, in particular a nonwoven fabric.

7. Hollow body (1) according to one of the preceding claims, characterized in that at least one of the textile layers (3, 4, 8) and / or the support layers (5, 9), preferably all textile layers (3, 4, 8) and / or all support layers (5, 9), are wound.

8. Hollow body (1) according to one of the preceding claims, characterized in that at least one outer layer, preferably the outermost and the innermost, and / or at least one textile layer and at least one adjacent support layer and particularly preferably all layers are impregnated with a matrix material.

9. Hollow body (1) according to one of the preceding claims, characterized in that the natural fibers of at least one of the textile layers (3, 4, 8) and preferably of all textile layers (3, 4, 8) are selected from the group consisting of sisal fibers, jute fibers, coconut fibers, kenaf fibers, abaca fibers, hemp fibers and flax fibers or a combination thereof, wherein the natural fibers are preferably sisal fibers.

10. Hollow body (1) according to claim 2 or one of the claims relating thereto, characterized in that at least one of the support layers (5, 9) and preferably all support layers (5, 9) contain at least natural fibers and / or synthetic fibers, wherein the mass ratio of natural fibers to synthetic fibers is preferably in the range of 1 to 2 to 2 to 1, particularly preferably 1 to 1.

11. Hollow body (1) according to claim 2 or one of the claims relating thereto, characterized in that at least one of the support layers (5, 9) comprises at least one carrier material and at least one layer of wood, wherein the carrier material and the layer of wood are preferably joined together in a material-bonded manner before the manufacture of the base body (6).

12. Hollow body (1) according to claim 11, characterized in that the wood layer has a thickness of at least 0.4 mm and at most 1.2 mm, in particular at least 0.6 mm and at most 1.0 mm or particularly preferably at least 0.7 mm and at most 0.9 mm and is in particular a wood veneer.

13. Hollow body (1) according to claim 11 or 12, characterized in that the carrier material is a nonwoven fabric.

14. Hollow body (1) according to one of the preceding claims, characterized in that the matrix material contains a resin, in particular a phenolic resin, and / or water glass. A hollow body (1) according to any one of the preceding claims, characterized in that the base body (6) has a circular, oval, rectangular, or polygonal cross-section. A hollow body (1) according to any one of the preceding claims, characterized in that the base body (6) has a constant cross-section or a cross-section that tapers at least partially conically towards at least one end of the base body (6). A hollow body (1) according to any one of the preceding claims, characterized in that the base body (6) has at least one connecting element suitable for engaging in at least one of the layers, wherein the connecting element is, in particular, a metal strip with hook-like elements (14) arranged on one or both sides.Hollow body (1) according to claim 17, characterized in that the connecting element is incorporated into the planar textile structure of at least one textile layer (3, 4, 8) and / or a support layer (5, 9). Hollow body (1) according to any one of the preceding claims, characterized by clamps as connecting elements for joining two or more layers. Hollow body (1) according to any one of the preceding claims, characterized by a decorative layer (11) as the outermost layer. Hollow body (1) according to any one of the preceding claims, characterized in that the base body (6) has, section by section, at least one additional textile layer (3, 4, 8) and / or a support layer (5, 9) along its longitudinal direction.Method for producing a multilayer base body (6) for a hollow body (1) according to one of the preceding claims, characterized by the following method steps: a) providing material webs for at least one textile layer (3, 4, 8) containing natural fibers selected from the group consisting of bast fibers, leaf fibers and fruit fibers or a combination thereof, and at least one support layer (5, 9);. b) Spiral winding of at least one web of material around a longitudinal axis of a winding mandrel to form a layer of the base body (6); c) Spiral winding of at least one web of material to form a subsequent layer in an area where a previous, adjacent layer has already been formed; d) Repeating step c) until all layers of the base body (6) to be wound have been formed, the layers comprising at least one textile layer (3, 4, 8) and optionally at least one support layer (5, 9); e) Curing of a liquid and / or liquefied matrix material introduced into at least one of the webs of material such that a solidified base body (6) is formed.

23. Method according to claim 22, characterized in that at least one material web for a textile layer (3, 4, 8), preferably the material webs for all textile layers (3, 4, 8), are pre-impregnated.

24. Method according to claim 22 or claim 23, characterized in that the material web of a subsequent layer is wound substantially simultaneously and in the same area as the material web of a previous layer.

25. Method according to one of claims 22 to 24, characterized in that the material web of a layer is wound parallel to the joint.

26. Method according to claim 25, characterized in that the material web of a subsequent adjacent layer is wound in such a way that it covers the joint formed in the previous layer, wherein the material web is wound in particular centrally to the joint.

27. Method according to one of claims 22 to 26, characterized in that at least one connecting means is provided on at least one material web or between a previous layer and a subsequent layer, which is suitable for coupling at least two layers together before the matrix material has hardened.

28. Method according to claim 27, characterized in that the bonding agent is an adhesive which is applied at least partially to the material web of a subsequent layer before winding.

29. Method according to claim 27 or 28, characterized in that the connecting means is a thread coated with an adhesive, which is wound section by section between two layers and / or incorporated into a planar textile structure of one of the layers.

30. Method according to one of claims 27 to 29, characterized in that the connecting means is a metal strip which is arranged to absorb shear forces occurring between two layers.

31. Method according to one of claims 27 to 30, characterized in that the connecting means is a clamp for joining at least two adjacent layers.

32. Method according to one of claims 22 to 31, characterized in that the base body (6) has a sheath layer which in particular contains a synthetic polymer and / or a nonwoven fabric, preferably a thread-reinforced nonwoven fabric, wherein the sheath layer serves to maintain a pressure built up by the material web wound under a certain tensile stress in the base body (6) and wherein the sheath layer is preferably detachable from the base body (6) after the matrix material has hardened.

33. Method according to one of claims 22 to 32, characterized in that an innermost layer of the base body (1) contains paper or cardboard and forms a counter-pressure body (7), wherein the innermost layer is preferably wound around the longitudinal axis of the winding mandrel before the other material webs in such a way that the counter-pressure body (7) is hardened until the other material webs are wound.

34. Method according to one of claims 22 to 33, characterized in that at least the outermost and / or the innermost layer of the base body (6) is diffusion-open in such a way that gases generated in the method can escape from the base body (6).

35. Method according to one of claims 22 to 34, characterized in that the base body (6) is wound in a continuous process and cut to a specific length after the matrix material has hardened.

36. Method according to one of claims 22 to 35, characterized in that the fully wound base body (6) is coated with a matrix material The material is dip-impregnated and then excess matrix material is squeezed out of the layers, preferably by rolling.

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