EP3460114B1 - Branching node for building construction and method for producing the branching node for building construction - Google Patents

Description

The present invention relates to a junction node for building construction and a method for producing the junction node for building construction.

Load-bearing components have to meet high requirements in order to be suitable for building construction. However, the branching nodes known from the prior art can only be produced with great effort or are restricted in terms of their field of application.

Branching nodes known in the prior art are, for example, welded connections with slotted plates or connecting rods (see Figure 1A ). Such branching nodes have an offset of the outer contour. They can be used primarily for connections subject to normal forces, but are designed for little or no torque. In addition, the protruding connections are not visually appealing.

Also known are welded, butt-jointed steel pipes (see Figure 1B ). In principle, the combination of such a structure with concrete would be conceivable for a load-bearing branch node. Such a construction is suitable for removing all types of cutting forces. Complex geometries with elliptical cross-sections in the intersection area are created by the oblique intersection of the pipe cross-sections. The intersection curves are differently curved. This requires the factory prefabrication of the metal parts. In addition, the weld seams must meet high requirements. Accordingly, such structures can only be manufactured by experienced and mechanically well-equipped metal construction companies. This means that the production of such structures is associated with a great deal of effort. In addition, in these structures, the shape of the knot is not that Adjusted the course of forces because there are no fillets between the straight elements. In addition, the design options are severely limited due to the manufacturing process.

Cast steel nodes are known as further node structures, as shown for example in FIG. 1C. Such cast steel nodes meet high aesthetic demands. In addition, the geometry can be adapted to the power flow. However, the production requires high financial investments in molds and casting tools. This only makes economic sense if a number of structurally identical node connections with identical geometries are to be produced. Structures with different node structures made of cast steel nodes can therefore only be realized to a limited extent and are associated with high financial costs.

DE 42 34 979 A1 discloses a tubular braid and apparatus for making same.

WO 03/053679 A1 discloses a ductile hybrid structural fabric.

FR 2 952 653 A1 discloses a closed tubular fibrous member and method of manufacture.

The present invention is based on the object of providing a branching node for building construction, which should be able to be produced with a high degree of freedom of design, and a production method for the branching node.

The object of the present invention is achieved by a method according to claim 1 and a branching node according to claim 11 and by the embodiments characterized in the claims.

1. (A) Bereitstellen eines Flechtkerns, welcher mindestens drei Arme aufweist und eine Verzweigung bildet;
2. (B) Bilden des Geflechts durch Umflechten des Flechtkerns mit einem Flechtmaterial,

wobei das Geflecht im Bereich der Arme mindestens zwei Flechtlagen aufweist.A method of making a braid as described herein includes the steps

1. (A) providing a braided core having at least three arms and forming a bifurcation;
2. (B) forming the braid by braiding the braid core with a braid material,

wherein the braiding has at least two braided layers in the area of the arms.

A braid is created by regularly crossing several strands of a braiding material with corresponding undulation points in the braiding process. The difference to weaving or stitch-bonding is that in braiding the strands of braiding material are not fed at right angles. A fiber orientation (orientation of the strands, braiding angle) of 0/90° is therefore not possible. In contrast to the fabric, the strands in the braid can be crossed +/-45°, for example. An additional difference to stitch-bonding is that in braiding a connection between the strands is achieved by crossing and undulating, whereas in stitch-bonding warp and weft threads lying on top of one another are connected to one another by looping stitch threads. A braid is a product made by braiding.

In step (A) of the method according to the invention, a braided core is provided. After the braid is produced according to the invention by braiding the braid core, the spatial shape of the braid and the fiber composite structure described here and the branching node according to the invention are essentially dictated by the spatial shape of the braid core.

The material from which the braided core is constructed (braided core material) is not subject to any particular restrictions, so that in principle any dimensionally stable material can be used. Inexpensive materials that are easy to process can thus be used, as a result of which the method according to the invention and the product obtained from it are particularly cost-effective. In addition, there is the greatest possible flexibility with regard to the spatial shape of the mesh.

Depending on the braiding material, the braided core can basically be manufactured in any way. Preferably, the braided core consists of an inexpensive material that is easy to process. Examples of this are organic polymers and sand containing minerals (special sand), which can be easily processed by milling, for example. The braided core can also be produced additively, for example through 3D printing.

It is advantageous if the braided core is constructed from a material which can be easily removed after the braiding has been completed. The braided core can be constructed from a material that can be milled, for example. Suitable machinable materials include metal, wood, plastic (preferably one or more organic polymers), specialty sand, and combinations thereof.

The braided core preferably comprises a material which can be dissolved in a fluid, preferably in a liquid, particularly preferably in an organic solvent (e.g. methanol, ethanol, acetone, dichloromethane, isopropanol, methyl ethyl ketone, n-hexane, toluene, diethyl ether, with acetone being preferred) , water and/or a mixture thereof. As a result, step (E) of the method described here for producing a fiber composite structure or of the method according to the invention for producing a branch node can be significantly simplified.

According to a preferred embodiment of the present invention, the braided core is composed of an organic polymer. The organic polymer is preferably foamed, with the foamed organic polymer preferably having closed pores.

A preferred organic polymer is polystyrene. It is particularly preferred that the core is made up of or consists of extruded polystyrene (XPS, ^Styrodur® ) or expanded polystyrene (EPS, ^Styropor® ), XPS being particularly preferred. Polystyrene is very soluble in several organic solvents (e.g. acetone, dichloromethane), which allows step (E) to be carried out simply by dissolving the braided core in the organic solvent.

According to a further preferred embodiment, the braided core is made from a hardened mixture comprising sand, binder and solvent. Preferably the mixture consists of sand, binder and solvent. To suitable Binders include, in particular, water-soluble salts. Because water-soluble binders are used, step (E) of the method described here for producing a fiber composite structure or the method according to the invention for producing a branch node can be significantly simplified. For example, a braided core of a cured mixture can be milled from a blank of the cured mixture. Alternatively, the uncured mixture can be poured into a mold and then cured. Curing can optionally take place under the action of heat. A suitable solvent is, for example, water. A braided core constructed in this way is not dimensionally stable against water, which allows step (E) to be carried out simply by removing the braided core with water.

Statements regarding the spatial shape of the braided core, the spatial shape of the cavity of the fiber composite structure or the spatial shape of the concrete core of the branch node for building construction apply accordingly to the spatial shape of the braided core, the cavity or the concrete core. This means that insofar as one of the three above three spatial forms is described here, the explanations apply correspondingly to the other two. Correspondingly, the statements made herein with regard to the braiding apply equally to the production method according to the invention and the fiber composite structure and the branching node according to the invention.

The shape (spatial shape) of the braided core is not particularly limited as long as it has at least three arms and forms a branch. The simplest case of a branch in three arms is called a bifurcation. In this case, three arms meet in a forking area, as is the case, for example, with a forked branch of a tree. The at least three arms start from a common branching area and extend from there in different directions. The three arms converge in a (single) branching area. The outer end of an arm is the portion of the arm furthest from the branching area. The branching area is the Area in which the at least three arms converge or merge into one another. The face of an arm is that part of the outer end of the arm which is visible in a plan view of the outer end along the arm axis. The axis of an arm runs from the branching area to the outer end of the arm.

The number of arms of the braided core is not particularly limited. For manufacturing reasons, the braided core preferably has 3 to 6, particularly preferably 3 or 4, particularly preferably 3 arms.

The braid has at least two braided layers (m ≥ 2) in the area of the arms. Thus, in the area of the arms, there are two or more braided layers that can be separated from one another. According to the invention, "the braiding has at least two layers in the region of the arms" means that the arms are at least partially braided with two braided layers. Preferably, the arms are completely braided with two layers of braid, apart from the end faces of the braided core.

The braiding preferably has at least one braided layer in the branching area. Due to the manufacturing process, the number of braided layers in the branching area can vary. This means that the braiding can have points with a different number of braided layers in each case in the branching area. According to a preferred embodiment, the braiding has points with m-1, m and m+1 braiding layers in the branching area. For example, the number of braided layers can be 1, 2 and 3 in the case of m=2 at different locations in the branching area. In particular with more than three arms, the number of braided layers in the branching area can have an even greater range of variation. The number of braided layers can be, for example, 1, 2, 3 and 4 at different locations in the branching area, or 1, 2, 3, 4 and 5.

According to a preferred embodiment, the braiding has the same number of braided layers m at every point in the region of the arms. This means that the number of braided layers in the area of the arms m is preferably at every point (at every place) of the mesh in the area of the arms the same (constant).

In step (B), the braided core is braided with a braiding material. Suitable braiding methods and devices for braiding are known to those skilled in the art. According to the invention, the use of a radial braiding machine is particularly suitable, although other braiding devices can also be used.

Suitable braiding materials are known to those skilled in the art. They are usually in the form of strands, ribbons or threads and have a certain flexibility. Suitable braiding materials preferably include glass fibers, aramid fibers, ceramic fibers, basalt fibers, hybrid yarn and/or carbon fibers, carbon fibers being preferred. The braiding material particularly preferably consists of carbon fibers. Furthermore, it is preferred that the braiding material is in the form of a roving (bundle of filaments arranged in parallel). In particular, it is preferred that the braiding material is a carbon fiber roving.

Hybrid yarn contains reinforcing fibers and thermoplastic fibers. The reinforcing fibers are preferably selected from the group consisting of glass fibers, aramid fibers, ceramic fibers, basalt fibers and/or carbon fibers. The thermoplastic fibers comprise a material which can be melted by heat and solidified by cooling. The thermoplastic fibers are preferably constructed from a thermoplastic material, particularly preferably from a thermoplastic organic polymer such as polyethylene and/or polypropylene. With the help of hybrid yarn, a fiber composite structure can be produced from the braid without the need for additional components.

According to a preferred embodiment of the present invention, the thermoplastic fibers are composed of polyamide.

The fineness of the braiding material is not subject to any particular restriction. The braiding material preferably has a tex value of 200 to 4000 tex (1 tex=1 g/1000 m).

According to the invention, it is sufficient to form the braid solely from braiding threads. According to a preferred embodiment, standing threads are used in addition to braiding threads, as a result of which a branching knot with advantageous static properties can be obtained. The ratio of the proportions by weight of the standing threads and braiding threads is preferably from 1:2 to 6:1, particularly preferably 1:2 to 2:1, for example 1:1 if standing threads are present.

It is preferred that the standing threads have a higher Tex value than the braiding threads. The Tex value of the standing threads is particularly preferably at least 400 tex, more preferably at least 800 tex, particularly preferably at least 1600 tex higher than the Tex value of the braiding threads. This minimizes thread-to-thread friction in the braiding process and ensures adequate thread tension.

The braiding threads preferably have a tex value of 200 to 4000 tex. The standing threads preferably have a tex value of 600 to 4000 tex. If the braiding or standing threads have Tex values from the above ranges, a branch knot with particularly advantageous static properties can be provided.

According to the invention, the arrangement of the standing threads in the braid can basically be arbitrary. Preferably, the standing threads extend between the outer ends of the arms and across the bifurcation area. That is, the standing threads preferably run from the outer end of one arm through the branching area to the end of another arm. This arrangement allows the tensile strength of the sheath to be increased, which is advantageous for absorbing moments through a corresponding branch node. In addition, it is possible to introduce standing threads only partially into the braid. In particular, standing threads can only be introduced at selected points of the braid for mechanical stabilization. Equally, for mechanical stabilization in selected areas of the mesh, standing threads can be introduced that have a higher Tex value than the other standing threads of the braid. The above measures make it possible to reinforce selected areas of the braid, which are intended to withstand particularly high loads in the branching node, with standing threads.

According to a preferred embodiment, step (B) comprises a plurality of braiding steps, wherein in each of the braiding steps the braiding direction is from the outer end of one arm to the outer end of a different arm of the braiding core (see Fig figure 2 ). That is, the arms are preferably braided in pairs. As a result, the method according to the invention for producing the mesh can be configured particularly efficiently.

In order to obtain particularly high stability of the fiber composite structure and the branching node, the arms, which are braided around in pairs, are preferably adjacent to one another. Each arm of the braided core is adjacent to at least the two arms that are spatially closest to it. For example, a first arm is adjacent to the two arms to which the first arm forms the two smallest angles of the braid core. The angles of the braided core are formed between the respective longitudinal directions along which the arms extend (arm axes). In case several arms form the same angle to the first arm and this is the smallest of all angles of the braid core, the arm is adjacent to all arms forming said equal and smallest angle to the first arm.

According to the invention, a distinction is made between planar (two-dimensional) and non-planar (three-dimensional, three-dimensional) braided cores (or composite fiber structures/branching nodes). "Even" in this context means that the axes of the arms of the braided core, the fiber composite structure or the branching node lie essentially in one plane. This is not the case with a non-planar braided core. A flat braided core spans a two-dimensional polygon, a non-planar braided core a polyhedron, with the edges of the polygon or polyhedron being formed by the stretches between the end areas of the arms.

According to a preferred embodiment, step (B) comprises at least k braiding steps, wherein in each of the k braiding steps the braiding core is braided from the outer end of one arm to the outer end of a different arm (braiding of the arms in pairs) and k is the number of edges of the represents the polygon or polyhedron spanned by the braided core.

If a flat braided core is braided in the method according to the invention and the arms are braided in pairs, step (B) comprises at least m=n braiding steps, where n represents the number of arms of the braided core and m represents the number of braided layers in the region of the arms.

According to a preferred embodiment, the method according to the invention is characterized in that the number of braiding layers in the area of the arms m is even and step (B) comprises m/2 n braiding steps, where n represents the number of arms of the braiding core, and in each of the m/2 n braiding steps, each starting from the outer end of an arm, which is braided with fewer than m braiding layers, to the outer end of a different arm, which is braided with fewer than m braiding layers, the braiding core is braided with the braiding material . This preferred embodiment of the method according to the invention is particularly suitable for producing a planar branch node.

• (B1) in einem ersten Flechtschritt ein erster Arm und ein davon verschiedener zweiter Arm des Flechtkerns mit dem Flechtmaterial umflochten werden und vom äußeren Ende des ersten Armes zum äußeren Ende des zweiten Armes umflochten wird;
• (B2) in weiteren Flechtschritten jeweils ausgehend vom äußeren Ende des zuletzt umflochtenen Armes zum äußeren Ende eines nicht mit m Flechtlagen umflochtenen Armes umflochten wird; und
• (B3) in einem letzten Flechtschritt ausgehend vom äußeren Ende des zuletzt umflochtenen Armes zum äußeren Ende des ersten Armes umflochten wird.

According to a preferred embodiment of the present invention, step (B) comprises the following steps (B1) to (B3), wherein

• (B1) in a first braiding step, a first arm and a different second arm of the braiding core are braided with the braiding material and braided from the outer end of the first arm to the outer end of the second arm;
• (B2) is braided in further braiding steps starting from the outer end of the last braided arm to the outer end of an arm not braided with m braided layers; and
• (B3) is braided in a last braiding step, starting from the outer end of the last braided arm to the outer end of the first arm.

The braiding can be produced particularly easily and quickly by steps (B1) to (B3). In addition, this makes it possible to obtain a fiber composite structure and a branch node that have particularly advantageous mechanical or static properties.

Preferably step (B2) comprises (m/2*n)-2 braiding steps. With regard to step (B2), it is also preferred that the arm not braided with m braiding layers is adjacent to the last braided arm. Additionally or alternatively, the arm not braided with m braided layers is preferably selected from the arms of the braided core with the fewest number of braided layers. That is, the arms are braided evenly in succession (sequentially, "in order"). As a result, a particularly regularly structured braid can be obtained, as a result of which the mechanical stability of the fiber composite structure or the static properties of the branching node can be influenced in a particularly advantageous manner.

If necessary, after step (B), or after each of the individual braiding steps of step (B), protruding braiding material is cut off so that the outer ends or end faces of the arms of the braiding core are exposed/are not braided with braiding material.

The average braiding angle (angle between standing and braiding threads in the braid) is preferably 40° to 80°, particularly preferably 50° to 70°, particularly preferably 55° to 65°, for example 60°. Particularly advantageous static properties of the branching node are observed for these braiding angles.

The mean braiding angle can be determined, for example, as follows: The braiding angle is measured at 10 different points of the braid (5 points in the area of the arms, 5 points in the branching area). The arithmetic mean of the braiding angles of the 10 different points is used as the mean braiding angle.

The braiding angle depends on parameters such as impeller speed, feed speed, braiding core diameter, etc., and can therefore be changed over the component. The braiding angle can be measured, for example, using a set square or optically using a camera at the cylindrical end.

A method for producing a fiber composite structure described here comprises the method for producing a braid and a step of connecting the braid to a matrix and a step (E) of removing the braid core to form a cavity. The fiber composite structure becomes dimensionally stable as a result of the step of connecting to a matrix.

In step (E) the braided core is removed. In principle, this can be done in any way. As already described above, the braided core is preferably dissolved or removed by a fluid (e.g. water or an organic solvent). The above statements in relation to the braided core material apply accordingly to step (E) of the method according to the invention.

When the braided core is removed, a cavity is formed which has largely the same spatial shape as the braided core and the concrete core of the branching node according to the invention. If, as described above, protruding braiding material was removed during or after step (B), the outer ends of the arms of the cavity of the fiber composite structure or the fiber-reinforced plastic structure are exposed at the front. That is, the cavity is externally accessible via the outer ends of its arms (unless integrated into a supporting structure such as a branched strut).

The matrix material constituting the matrix is not subject to any particular restriction. In principle, any material that is suitable for the production of fiber composite materials is suitable as matrix material.

According to a preferred embodiment, a ceramic matrix material is used. In principle, all ceramic matrix materials suitable for the production of fiber composite materials can be used. Examples of suitable materials include silicon carbide and/or alumina based ceramics. A ceramic matrix material is particularly advantageous with regard to fire protection requirements.

According to a further preferred embodiment, the matrix material is a plastic material. In this case, the method for producing a fiber composite structure can also be referred to as a method for producing a fiber-reinforced plastic structure. Suitable plastics that can be used as matrix materials include organic polymers, cured resin compositions, and thermoplastic materials, particularly those thermoplastic materials from which the thermoplastic fibers of the hybrid yarn can be constructed.

According to a preferred embodiment of the present invention, the braiding material comprises hybrid yarn and the inventive method comprises the step of melting the hybrid yarn. In this step, the thermoplastic fibers of the hybrid yarn are melted so that they form the matrix. This is preferably done using pressure, in particular by pressing. As a result, a fiber-reinforced plastic structure can be obtained directly from the mesh without the need for additional components. However, it is also possible to combine the step of melting the hybrid yarn with other measures for connecting the braid to a matrix. With regard to the hybrid yarn and its components, the above statements apply accordingly. The step of fusing the hybrid yarn is not particularly limited. For example, the mesh can be melted by heating it, but also by using ultrasound. After melting, optionally followed by pressing, the mesh is preferably cooled to a temperature below 50° C. and particularly preferably to room temperature (25° C.) so that the thermoplastic material solidifies and thus imparts dimensional stability to the fiber composite structure.

• (C) Einbringen eines duroplastischen Matrixsystems in das Geflecht;
• (D) Vernetzen des duroplastischen Matrixsystems; und
• (E) Entfernen des Flechtkerns unter Bildung eines Hohlraums.

According to a preferred embodiment, the method according to the invention comprises a method for producing a fiber-reinforced plastic structure, comprising the method for producing a mesh and the steps

• (C) introducing a thermosetting matrix system into the braid;
• (D) crosslinking the thermoset matrix system; and
• (E) Removal of the braided core to form a void.

Step (C) is not subject to any particular limitation. It can be introduced, for example, by applying it to the mesh. In principle, the matrix (thermosetting matrix system) can be incorporated or applied in any suitable manner. Examples of suitable incorporation or application processes are manual lamination, dipping, infusion processes and injection processes, with infusion and injection processes being preferred with regard to efficient process management. If the introduction takes place by application, then in step (C) the matrix is applied to the mesh in such a way that the mesh is completely penetrated by the matrix.

The matrix contains one or more resins. In principle, any resin that is suitable for the field of building construction is suitable as the resin. A curable resin composition is preferably used as the thermosetting matrix material. The matrix can include epoxy resins, polyester resins, polyurethanes and/or phenolic resins. In addition, the matrix can contain other components, e.g. B. contain one or more curing agents. For reasons of fire protection, a resin with high flame resistance is preferably used. The matrix preferably contains one or more flame retardants. The matrix particularly preferably consists of one or more (preferably curable) resins, optionally one or more curing agents and optionally one or more flame retardants.

Step (D) is not subject to any particular limitation. In step (D), conditions are applied which lead to the curing of the matrix or the resin composition. For example, this can be done by heating the matrix system or the resin composition or by irradiating the matrix system or the resin composition with electromagnetic radiation (for example UV light), as a result of which the mechanical properties of the resulting fiber-reinforced plastic structure or the branch node are significantly improved. If appropriate, step (D) can also simply consist in the braiding with the matrix system applied thereto or the resin composition applied thereon being stored (left standing), for example for one minute to one day, preferably 1 to 12 hours. Heating or irradiation are also not absolutely necessary. For example, step (D) can be carried out at a temperature of 5 to 50° C., preferably 15 to 30° C., for example at room temperature. Because a matrix system or a resin composition is applied to the mesh (step (C)) and cured (step (D)), the resulting fiber-reinforced plastic structure is dimensionally stable.

With regard to step (E), the above statements apply accordingly.

• (C) Aufbringen einer härtbaren Harzzusammensetzung auf das Geflecht;
• (D) Härten der härtbaren Harzzusammensetzung; und
• (E) Entfernen des Flechtkerns unter Bildung eines Hohlraums.

According to a preferred embodiment, the method according to the invention comprises a method for producing a fiber-reinforced plastic structure, comprising the method for producing a mesh and the steps

• (C) applying a curable resin composition to the braid;
• (D) curing the curable resin composition; and
• (E) Removal of the braided core to form a void.

• (F) Befüllen des von der Faserverbundstruktur umhüllten Hohlraums mit einem Betongemisch; und
• (G) Aushärten des Betongemisches.

In one aspect, the present invention relates to a method for producing a branch node for building construction, comprising the method for producing a fiber composite structure and the steps

• (F) filling of the cavity encased by the fiber composite structure with a concrete mixture; and
• (G) curing of the concrete mix.

Concrete is placed in the cavity by steps (F) and (G). In step (F), compaction measures can optionally be carried out. In step (G) can the concrete mixture can be post-treated if necessary.

If the branching node is to have an (internal) reinforcement, for example a longitudinal reinforcement and/or a connection reinforcement, this can be introduced completely or, in the case of a connection reinforcement, partially into the cavity of the fiber composite structure before step (F). The connection reinforcement is preferably made of a conventional reinforcement material such as steel and is in rod form. Textiles or rovings, for example carbon fiber rovings and/or glass fiber rovings, can be used for reinforcement.

The concrete mix used in step (F) is not particularly limited. Both normal concrete, high strength concrete and ultra high strength concrete can be used. Low-shrinkage, self-compacting concrete is preferably used. The concrete mixture can consist exclusively of concrete. The concrete mixture can contain fibers (particularly steel fibers, plastic fibers, for example polyethylene fibers (PE fibers), carbon fibers and/or glass fibers and optionally other aggregates as additives or additives.

It is preferred that the outer ends of all arms of the fiber composite structure are exposed at the front, ie are not braided with the braiding material. To produce the branching node according to the invention, preferably n-1 arms are boarded up before filling (F). The filling (F) then takes place via the free-standing end of the arm, the outer end of which is not boarded. After filling, any air pockets present in the filled concrete mixture can be removed, for example with the aid of a vibrator, preferably using an internal vibrator.

The branching node according to the invention can be used in a conventional construction in a supporting structure. For this purpose, the existing connection reinforcement of the branch node can be connected to the surrounding parts of the supporting structure. Alternatively, the supporting structure connected to the branching node or parts thereof can be produced in a core-shell construction and the support structure is concreted in whole or in part.

Between steps (F) and (G), the concrete mixture that has been poured in is optionally post-treated under customary conditions. After-treatment can be carried out via the end face(s) of one or more arms that may be exposed. This is possible, for example, if one or more arms do not connect to adjacent components.

In step (G) the poured concrete mixture is cured under usual conditions. If necessary, the casing of the n-1 arms is removed after curing.

A fiber composite structure described here comprises a fiber portion and a matrix portion, wherein the fiber composite structure at least partially encloses a cavity, wherein the cavity has at least three arms and forms a branch; and the fiber portion comprises a braid with at least two braided layers in the area of the arms.

The above statements in relation to the manufacturing process for the mesh and the manufacturing process for the fiber composite structure apply accordingly to the fiber composite structure.

The fiber composite structure is, for example, a fiber-reinforced plastic structure, comprising a fiber portion and a plastic portion, the fiber-reinforced plastic structure at least partially enclosing a cavity, the cavity having at least three arms and forming a branch; and the fiber portion comprises a braid with at least two braided layers in the area of the arms.

The fiber composite structure is obtainable from the process described above for its manufacture.

In a further aspect, the present invention relates to a branching node for building construction, comprising a concrete core, the concrete core having at least three arms and forming a branch; and a fiber composite structure at least partially encasing the concrete core, the fiber portion of which comprises a braid with at least two braided layers in the area of the arms, the end faces of the outer ends of the arms of the concrete core not being encased or covered by the fiber composite structure.

The above statements in relation to the manufacturing method for the braid, the manufacturing method for the fiber composite structure and the manufacturing method for the branching node apply accordingly to the branching node.

The number of braided layers of the fiber composite structure or the braided layers of the branching node in the area of the arms m is not subject to any particular restriction as long as m is at least 2. Because m≧2, the branching node has particularly advantageous static properties. Preferably m is even, for example in the case of a planar fiber composite structure/a planar branch node. m is particularly preferably from 2 to 12, more preferably from 2 to 8, particularly preferably from 2 to 6, for example 2.

The braiding preferably has at least one braided layer in the branching area. Preferably, the number of braided layers is the same at each point of the braid. However, due to the manufacturing process, the number of braided layers in the branching area can vary. This means that the braiding can have points with a different number of braided layers in each case in the branching area. According to a preferred embodiment (level branching node with three arms), the braiding has points with m−1, m and m+1 braiding layers in the branching area. For example, with m=2 (two braided layers in the area of the arms), the number of braided layers can be 1, 2 or 3 at different locations of the branching area. With a more complex structure of the branching node, e.g. B. with more than three arms, the number of braided layers can vary over an even larger range.

The core and skin of the branch node can be load-bearing and non-load-bearing, respectively be. The shell can also serve only as formwork without contributing as reinforcement. The filling material, the concrete, can also only serve as reinforcement for the shell. The shell can also only partially serve as reinforcement. The resistance of the fiber composite structure without additional measures can be given in the cold design, without the resistance of the fiber composite structure also having to be given in the hot design without additional measures.

The branch node according to the invention can have a high load-bearing capacity. The shell of the branch node formed by the fiber composite structure can serve as permanent formwork and at the same time as external reinforcement (external reinforcement). It is possible that compressive forces are mainly carried by the concrete core and tensile forces are absorbed by the shell. The envelope can be designed in such a way that it effectively confines the concrete and leads to an increase in the load-bearing capacity, based on the unconfined strength of the concrete, by establishing a multiaxial state of stress in the concrete. The shell can absorb tensile forces in the circumferential direction and, with sufficient confinement rigidity in the concrete, can cause a multiaxial state of stress by constriction, especially in the case of compressive stress. The shell can also absorb tensile forces in the longitudinal direction, which can arise from moments.

The concrete core is only partially encased by the fiber composite structure. The outer ends of the arms of the concrete core are exposed at the front. This means that the end faces of the outer ends of the arms of the concrete core are not encased or covered by the fiber composite structure, so that the surface of the branching node at the end faces is a concrete surface from which reinforcement or connecting reinforcement may protrude.

The concrete core preferably has fillets in the branching area. The concrete core particularly preferably has no edges in the branching area. In this way, an attractive aesthetic effect of the branch node can be achieved. In addition, the geometry of the branching node can be adapted to the distribution of forces of a load-bearing structure in which the branching node is installed. be adjusted.

The arms of the branch node can have different diameters, lengths, orientations and curves to the other arms. The diameter of an arm is its largest length dimension perpendicular to the arm axis, measured at the outer end of the arm. The arm axes preferably lie in a common plane, at least in the case of three arms. The concrete core is preferably rotationally symmetrical, particularly preferably point-symmetrical. It is also preferred that the cross-sectional areas at the respective outer end of the arms are round and therefore have no corners. The cross-sectional areas can be elliptical, for example, and are preferably circular. The cross-sectional area at the outer end of an arm is the cross-sectional area in plan view of the end face along the axis of the arm.

In a particularly preferred embodiment, the branching node according to the invention has the same diameter of the arms, rounded cross-sectional areas and/or rotational or point symmetry.

There are no particular restrictions on the dimensions of the concrete core. A minimum load-bearing capacity is required for use in buildings, this determines the geometric dimensions and requires an individual design of the component for each application.

The diameters of the arms can range from a few centimeters (e.g. 1 cm) to several hundred centimeters (e.g. 500 cm). The diameters of the at least three arms, independently of one another, are preferably at least 4 cm, preferably at least 8 cm, particularly preferably at least 10 cm. The diameter of the arms is preferably at most 100 cm, particularly preferably at most 20 cm.

So that the branching node can be used in building construction, it should have a minimum side length so that it can be attached to surrounding load-bearing elements (adjacent Support members) to be able to be connected. Leg length is the length from the beginning of the axis of the leg along the straight axis of the leg to the extreme edge of the leg. The terms "arm" and "thigh" are synonymous in this context. The connection to surrounding support elements is preferably made via a plug-in or socket connection, which can also be glued and can have mechanical interlocking (torsion lugs, nubs, etc.) and usually requires an overlap. A cylindrical or tubular section (connection area) between the end of the double-curved areas of the branch and the outermost edge of the leg is particularly preferred for these connections. For these types of connection, a length of the cylindrical or tubular section of at least one arm diameter, in particular at least twice the arm diameter, is preferred. The length between two branches is preferably at most 20 m, particularly preferably at most 10 m, for example at most 5 m. Accordingly, the length of an arm of the branch node according to the invention (or the fiber composite structure) is at most 10 m, particularly preferably at most 5 m, for example at most 2.5 m. The length of the connection area for plug and socket connections is preferably at least 4 cm, particularly preferably at least 8 cm, particularly preferably at least 20 cm.

The branch node or the concrete core preferably has reinforcement. Preferably, the reinforcement is connecting reinforcement, by which the branch node can be connected to adjacent support members. As an alternative or in addition to this, a connection to adjacent load-bearing members can be made using built-in steel parts, sleeves, plugs, screw connections, etc. or using glued connections. The adjacent support members can also be connection nodes according to the invention and/or conventional support members.

In order to ensure fire-bearing behavior, the concrete core of the connection node according to the invention can have additional reinforcement, in particular longitudinal reinforcement.

• Figur 1A zeigt einen Rohrknoten mit Schlitzblech und Flanschplatte aus Stahl aus dem Stand der Technik.
• Figur 1B zeigt einen Rohrknoten aus geschnittenen und verschweißten Stahlrohren aus dem Stand der Technik.
• Figur 1C zeigt einen Stahlgussknoten aus dem Stand der Technik.
• Figur 2 zeigt einen Kern zur Herstellung eines erfindungsgemäßen Verzweigungsknoten mit drei Armen (1, 2, 3). Flechtrichtungen sind durch doppelköpfige Pfeile angegeben.

The branching node according to the invention is particularly suitable for use in building construction, in particular in building construction and/or civil engineering. The branch node can be used in support systems such as truss or frame systems.

• Figure 1A shows a tube node with slotted plate and flange plate made of steel from the prior art.
• Figure 1B shows a prior art tube junction made of cut and welded steel tubes.
• Figure 1C shows a cast steel node from the prior art.
• figure 2 shows a core for the production of a branch node according to the invention with three arms (1, 2, 3). Braiding directions are indicated by double-headed arrows.

The present invention is further illustrated by the following non-limiting examples.

examples Example 1 Production of a branch node with a shell made of fiber-reinforced plastic structure

A braided core was milled out of a polystyrene plate with a milling robot. The resulting core had three arms and a point-symmetrical spatial shape (see Fig figure 2 ).

The braided core with a leg diameter of 125 mm and a leg length of 175 cm was braided with a radial braiding machine (144 radial braiders from Herzog) in 3 braiding steps, giving a two-layer braid. As in figure 2 shown, was first in the first braiding step from the outer end of arm 1 to the outer end of arm 2, then in the second braiding step from the outer end of arm 2 to the outer end of arm 3 and finally in the third and final braiding step from the outer end of arm 3 to outer end of the arm 1 braided. After each of the three braiding steps, the ends of the last braided arms were sealed with adhesive tape and excess braiding material was cut off.

Braiding and standing threads were used as braiding material. The braiding threads consisted of a carbon fiber roving with 24 K (fineness of 1600 tex) and the standing threads of a carbon fiber roving with 48 K (fineness of 3200 tex). The carbon fiber rovings were of the " ^Tenax® STS filament yarn" type from Toho Tenax. 72 braiding threads and 72 standing threads (ratio of braiding threads to standing threads by weight = 1:2) were used. The braid angle was about 60°.

A resin composition (two-component epoxy resin composition ^MGS® RIMR 135 with epoxy resin component "RIMR 135" and liquid hardener component "RIMH 137" from Hexion; resin/hardener weight ratio=10/3) was applied to the braided core by hand lamination. The braid was completely penetrated by the resin composition. the Braided core with the epoxy resin composition applied to the braid was cured at room temperature for 24 hours and then tempered at 80° C. for 15 hours.

After cooling to room temperature, the core was removed by dissolving in acetone.

Two of the free-standing (open) arms of the fiber-reinforced plastic structure obtained were then boarded up. The hollow space of the fiber-reinforced plastic structure was filled with concrete (type "119M" from Godel Beton). Air pockets were removed with the help of an internal vibrator and the resulting free volume was filled with concrete. Thereafter, the obtained branch knot was cured for 28 days.

Comparative Example: Production of a branch node without a shell made of fiber-reinforced plastic

A concrete branch node was fabricated without a fiber reinforced plastic sheath. Apart from the missing shell, the same parameters as in example 1 were chosen.

Example 2: comparison

The branch nodes obtained from Example 1 and the Comparative Example were each subjected to a bending test by standing, vertically loading the branch on one leg in the plane of the branch and holding it at two ends opposite to the direction of the force. There was no restraint in the horizontal direction, which means that two legs were subjected to bending loads. The test force measured in the test stand for Example 1 was 753.7 kN. Only 51.1 kN were measured for the comparative example. The results are summarized in Table 1 below. Table 1: Test force of example 1 and the comparative example test force example 1 753.7 kN comparative example 51.1kN

In further tests, the compressive load-bearing capacity and the increase in load-bearing capacity due to the confinement effect were also examined. These tests also confirmed the excellent mechanical properties of the branch node of Example 1.

The present invention enables the production of branch nodes with individual geometries and high quality of the surface of the branch node. In contrast to the production of cast steel nodes, the production costs are independent of the number of pieces produced, since the time-consuming use of casting molds is no longer necessary.

The shell (fiber composite structure) of the branching node greatly increases its mechanical resilience. In particular, by adapting the arrangement of the braiding material (internal geometry), filigree branching nodes that are precisely adapted to the individual load situation can be provided. In addition, a high level of material efficiency is achieved. By suitably adapting the spatial shape of the branching node or the concrete core (outer geometry), such as the preferred fillets between the legs, the outer and inner geometry can be adjusted according to the flow of forces. Through the synergistic interaction of the inner and outer geometry of the branching node according to the invention, a high load-bearing capacity can be achieved even with a slim and light construction of the branching node, as a result of which material can be saved.

Claims (11)

1. Method for producing a branching node for building construction, comprising the following steps:

   (A) providing a braid core, which has at least three arms (1, 2, 3) and forms a branch,

   (B) forming a braid by overbraiding the braid core with a braiding material, wherein the braid in the region of the arms (1, 2, 3) has at least two braid layers,

   connecting the braid to a matrix,

   (E) removing the braid core to form a cavity, resulting in a fibre-composite structure,

   (F) filling the cavity enclosed by the fibre-composite structure with a concrete mixture, and

   (G) curing the concrete mixture.
2. Method according to claim 1, wherein the braid core provided in step (A) is constructed from a millable material or comprises a material which is soluble in a liquid.
3. Method according to claim 1 or 2, wherein the braid core provided in step (A) is produced from a cured mixture comprising sand, binder and solvent.
4. Method according to one of claims 1 to 3, wherein step (B) comprises a number of braiding step, wherein in each of the braiding steps, the braiding direction runs from the outer end of one arm (1, 2, 3) to the outer end of a different arm (1, 2, 3) of the braid core.
5. Method according to one of claims 1 to 4, wherein the number of braid layers in the region of the arms (1, 2, 3) m is an even number and step (B) comprises m/2•n braiding steps, wherein n denotes the number of arms (1, 2, 3) of the braid core, and in each of the m/2•n braiding steps, in each case from the outer end of one arm (1, 2, 3) that is overbraided with less than the m braid layers to the outer end of a different arm (1, 2, 3) that is overbraided with less than the m braid layers, the braid core is overbraided with the braiding material.
6. Method according to claim 5, wherein step (B) comprises the following steps (B1) to (B3), wherein

   (B1) in a first braiding step, a first arm (1) and a different, second arm (2) of the braid core are overbraided with the braiding material and overbraiding is carried out from the outer end of the first arm (1) to the outer end of the second arm (2);

   (B2) in further braiding steps, overbraiding is carried out in each case from the outer end of the most recently overbraided arm (2) to the outer end of an arm (3) that has not been overbraided with m braid layers; and

   (B3) in a final braiding step, overbraiding is carried out from the outer end of the most recently overbraided arm (3) to the outer end of the first arm (1).
7. Method according to one of claims 1 to 6, wherein the braiding material comprises braiding yarns and filler yarns.
8. Method according to one of claims 1 to 7, wherein the braiding material comprises glass fibres, carbon fibres, basalt fibres, hybrid yarn, ceramic fibres and/or aramid fibres.
9. Method according to claim 8, wherein the braiding material comprises hybrid yarn, wherein the hybrid yarn contains reinforcing fibres and thermoplastic fibres.
10. Method according to one of claims 1 to 9, further comprising the following steps:

    (C) introducing a thermoset matrix system into the braid; and

    (D) crosslinking the thermoset matrix system.
11. Branching node for building construction, comprising a concrete core, wherein the concrete core has at least three arms (1, 2, 3) and forms a branch; and a fibre-composite structure partially enclosing the concrete core, the fibre component of which comprises a braid that is connected to a matrix and has at least two braid layers in the region of the arms (1, 2, 3), wherein the front faces of the outer ends of the arms (1, 2, 3) of the concrete core are not enclosed or covered by the fibre-composite structure.

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