HK1094179B - Force-introduction point in core composites and method for producing said point using reinforcement elements that traverse the thickness of the core composite - Google Patents

Description

Force transmission point in a core composite and method for producing the force transmission point by means of a reinforcement element penetrating in the thickness direction of the core composite

Technical Field

The invention relates to a force transmission point in a core composite and a method for producing a force transmission point in a core composite by means of a reinforcing element penetrating in the thickness direction of the core composite.

Background

The present invention is suitable for transmitting forces and moments into the core composite structure. The core composite structure may preferably consist of a fiber-plastic composite comprising a textile semifinished cover layer (1 and 3, for example, fabric or gauze (Gelege), mat, etc.), a core material (2, for example, a polymeric foam material) and a polymeric matrix material (thermoplastic or thermosetting plastic). The core composite is a layered structure consisting of relatively thin upper and lower cover layers 1, 3 and a relatively thick, low bulk density core layer 2. The core composite structure is substantially very sensitive to locally introduced force or moment loads due to the low tensile (Zugweich) and low compressive (druckweiich) properties of the thinner cover and core materials. It is therefore necessary to transmit forces into the core composite structure in a manner suitable for the load, material and processing technology. The multiaxial load states occurring at the force transmission point can no longer be assumed by the cover layer which is only subjected to surface loads (tensile, compressive, shear forces). The constructional measures required for this purpose at the location of the force transmission depend on the point and direction of action of the force and the resultant of the force. The introduction of the force is therefore usually effected such that local instabilities (e.g. twisting or creasing of the cover layers) do not occur, the core layer and the cover layers are not damaged, and the force-transmitting element is not separated from the core composite structure. The prerequisite for this is that the forces and moments introduced into the core composite structure are distributed as large as possible and uniformly. Thus, all structural measures for introducing forces into the layered structure have in common that they contribute to a reduction of the local stress level by increasing the force introduction area and the cross-sectional area. In addition, in some applications, the low pressure-resistant core material must be replaced by a pressure-resistant material in the region of the force transmission points, so that, for example, the prestress of a threaded connection can be absorbed.

In order to transmit forces and moments into the core composite, additional installed force transmission elements (so-called outer inserts) or inserted force transmission elements (so-called inner inserts) can be used. Furthermore, there is the possibility of removing the core material in the region of the force transmission location and joining the two cover layers together, so that there is a single fiber-plastic composite region without the need for additional force transmission elements. As a further force transmission option for the core composite structure, self-tapping screws or screw inserts and rivets can also be used, but they can only transmit small forces and torques. Force transmission points are always required if forces and moments are to be introduced into or removed from a structure and structural parts are to be connected to one another. Core composite structures of fiber-plastic composites are used, for example, in general in aviation and aerospace, in rail vehicle manufacturing and automotive manufacturing, and in the shipbuilding industry.

All known force transmission elements (outer inserts) for the assembly of core composite structures made of fiber-plastic composites are connected to one of the two cover layers in a material-locking manner. All these solutions for force introduction have the following common disadvantages. The two cover layers are subjected to very different loads, i.e. the cover layer with the mounted outer insert is subjected to a much greater load than the opposite cover layer. This may lead to delamination between the outer insert and the cover layer or between the cover layer and the core layer. Furthermore, the soft tensile and low compression resistant core material is not sufficiently reinforced under the outer insert, thereby subjecting the core material to high loads and possibly causing the core material to fail. In order to avoid failure of the core layer below the outer insert, in some solutions the force-transmitting location area is completely replaced by another material with high mechanical properties.

All known additional embedded force transmission elements (inserts) are connected to the core composite structure in a material-locking manner. The insert can be positioned within the cover layer, between the cover layer and the core layer or within the core material. Due to the purely material-locking connection, locally acting forces or moment loads can cause the insert to detach from the entire core composite structure as a result of adhesive failure, whereby complete failure of the force introduction or delamination between the cover layer and the core layer can occur.

All known force transmission solutions for core composite structures without additional force transmission elements have in common that the core material is first removed or compressed in the region of the force transmission points and the two cover layers are joined together, so that a single reinforcing layer region of fiber-plastic composite is present. A pin connection can then be arranged in the single region. In this case, with all known solutions, failure of the cover layer in the region of the splice or failure of the core outside the region of the splice or delamination between the cover layer and the core layer results, since these regions are free of additional force-locking and material-locking reinforcement of the core composite structure in the thickness direction of the core composite structure.

The possibility of force introduction solutions for the core composite structure by means of split coverings without additional force transmission elements is disclosed in the publications DE 10002281 a1 and EP 1106341 a 2. However, in these inventions, no structural reinforcement of the core composite body by force-locking and material-locking is achieved inside or outside the region where the cover layers are split, and therefore the resistance between the cover layers and the core layer against delamination (peel strength) is not improved and the core layer is also free from reinforcement. The typical failure characteristics, delamination between the cover layer and the core layer and core failure in the region of the force transmission sites cannot therefore be improved by these two disclosed methods.

In the publication US 005741574a, a method is disclosed how a pin connection can be reinforced by means of a fiber-reinforced structure embedded in a core. This invention involves first embedding the fiber strands within the entire core material. The textile cover is then placed on the core material and is loaded with pressure, whereby the core material is compressed and the threads can be forced into the cover. Impregnation of the core composite structure is then achieved by a liquid thermosetting resin system. Then, a resin-based curing process is performed. A through-hole for the pin connection is embedded in the hardened core composite structure. The fiber threads in the core material can thereby withstand the prestress of the screw connection and prevent the tendency of delamination between the cover layer and the core layer in the region of the force transmission points. In this invention, there is only one cohesive connection and not one non-cohesive and non-positive connection between the fiber strands and the entire core composite structure in the force transmission region, whereby the resistance against delamination between the cover layer and the core layer is only slightly increased in comparison with a non-cohesive and positive connection. Another disadvantage of this invention is that the entire core material of the core composite structure has stitching threads. This means that the force transmission points are not necessarily and additionally reinforced in comparison with the remaining core composite structure, so that the undisturbed core composite structure and the force transmission points are loaded very differently and the lightweight structural potential of the core composite structure is not fully utilized. Furthermore, the core material is open in the region of the through-openings, so that a liquid or gaseous medium can be forced into the core material. These intruding media may negatively alter the properties of the core material and even lead to failure.

In the publication DE 19834772C 2, a method for connecting an additionally inserted force transmission element (insert) is known, which has a fiber-reinforced structure consisting of a single reinforcing layer. The insert is positioned between the individual reinforcing layers and is sewn in the thickness direction of the fiber-reinforced structure by means of sewing threads. The disclosed solution for connecting an insert to a single reinforcing structure consisting of a single reinforcing layer is also applicable to core composite structures. In this case, the insert is inserted between the individual reinforcing layers of one of the two cover layers and is sewn together by means of a sewing thread. Subsequently, both the cover layer comprising the stitched insert and the further cover layer are placed on the core layer. By means of the liquid impregnation process, the cover layer can be wetted with a polymeric matrix material and the adhesive bond between the cover layer and the core layer can be produced, so that a core composite structure of a fiber-plastic composite is obtained. The application of the disclosed invention to the core composite structure only serves as a force-locking and form-locking connection between the inner insert and the cover layer by means of the sewing thread. In this way, neither resistance against delamination between the cover layer and the core layer can be increased in the region of the force transmission points, nor can the low tensile and compressive core material be reinforced, so that both typical failure modes of the core composite structure cannot be improved. A further disadvantage of the invention is that the cover layer on which the insert is located is subjected to a significantly greater load than the other cover layer when forces and moments are introduced into the insert, as a result of which the lightweight structural potential of the core composite is not fully utilized. Furthermore, a force flow from one cover layer to the other through the core material, which has lower mechanical properties than the material of the cover layers and is a weak point in the core composite structure, must be achieved. This can subject the core material to very high loads and trigger failure of the core material. The strength and rigidity of the force transmission site or of the entire core composite structure is thus mainly influenced by the low mechanical properties of the core material.

All the previously known force introduction solutions for core composite structures have in common that the core composite structure is not sufficiently reinforced in the region of the force application points, so that core failures can occur due to excessive tensile, compressive or shear stresses and delamination between the cover layer and the core layer. Furthermore, in all known solutions with additionally mounted or embedded force transmission elements, the force transmission element is not connected to the entire core composite structure in a force-locking and form-locking manner. It is therefore neither possible to prevent a separation of the force transfer element from the core composite structure nor between the cover layer and the core layer or between the force transfer element and the cover layer.

Disclosure of Invention

The aim of the invention is to improve the mechanical properties of the force transmission points in the core composite by inserting reinforcing elements in the thickness direction (z direction) of the core composite structure (fig. 1a and 1 b).

In the force transmission position of the core composite according to the invention, the core composite has an upper cover layer, a lower cover layer and a core layer, wherein in the force transmission position the cover layers of the core composite are joined and a force transmission element is provided, and in the force transmission position the core composite structure is reinforced by a reinforcing element penetrating in the thickness direction of the core composite, the force transmission element having one or more flanges.

Preferably, the reinforcement element projects beyond the force transmission point into the core composite structure surrounding the force transmission point.

Preferably, the cover layer consists of a textile semifinished product, the core layer of the core composite consists of a polymeric or natural core material, and the reinforcing element consists of a textile reinforcing structure, and the cover layer, the core layer and the reinforcing element are embedded in a polymeric matrix material.

Preferably, the force transmission element has a hole for receiving the reinforcing element and is connected to the core composite structure in the thickness direction of the core composite structure in the region of the force transmission point by the reinforcing element.

Preferably, the force transfer element is arranged on one of the two cover layers or on both cover layers.

Preferably, the force transfer element is arranged inside one of the two cover layers or inside both cover layers.

Preferably, the force transfer element is arranged between two cover layers and/or penetrates the core material.

Preferably, the force transfer element has one or more projections which bear against one of the cover layers or against the respective cover layer.

The method according to the invention for producing the force transmission point in the core composite described above is characterized in that, in a working step prior to the introduction of the polymeric matrix material, the force transmission element and the core composite structure are sewn to one another in the region of the force transmission point in the thickness direction of the core composite structure by means of textile reinforcing elements introduced by means of sewing technology in the region of the force transmission point.

The method according to the invention for producing the force transmission site in the core composite described above is characterized in that, in a working step prior to the introduction of the polymeric matrix material, the upper cover layer, the core layer and the lower cover layer are sewn to one another outside the region of the force transmission element in the thickness direction of the core composite structure in the region of the force transmission site by means of textile reinforcing elements introduced by means of sewing technology.

The force transfer location described above is used for the construction of a spacecraft, an aircraft, a watercraft or a land craft.

This object is achieved in that the cover layers of the core composite are joined together in the region of the force transmission points in the core composite and a force transmission element is provided, and in addition, the core composite structure is reinforced in the force transmission points by reinforcing elements which penetrate in the thickness direction of the core composite. The upper cladding layer, the core layer and the lower cladding layer are connected in a force-fitting and form-fitting manner by means of the reinforcing element in the region of the force transmission point. Furthermore, the force transmission element can be fixed to the core composite by means of a reinforcing element. Textile reinforcing structures (4, for example sewing threads, fiber bundles, glass strands, etc.) can preferably be used as reinforcing elements. The invention relates to a core composite having cover layers 1 and 3, preferably consisting of a textile semi-finished product (for example a woven, knitted or braided fabric, a mat, etc.), and having a core layer 2, preferably consisting of a polymeric rigid foam material, and optionally a matrix material, preferably consisting of a polymeric material (thermoplastic or thermosetting plastic). The core composite structure may be made by one of many liquid composite forming (LCM) processes, such as resin injection or resin infusion processes. This type of core composite structure is reinforced in the thickness direction by means of a textile reinforcing structure in the force transmission region before impregnation with the polymeric matrix material. The establishment of such a reinforced force transmission location can be accomplished, for example, by industrial sewing techniques. The reinforcement, preferably sewing threads, is introduced in the thickness direction of the core composite, which can be achieved, for example, by means of a sewing needle. The sewing needle penetrates the entire core composite structure and leaves a through-opening for the core material of the rigid polymeric foam material, including the reinforcing structure. The cross-sectional area of the through-opening must be sufficiently large in comparison with the cross-sectional area of the reinforcing structure, so that the reinforcing structure can be wetted with the polymeric matrix material and connected to the core in a form-fitting manner. The stiffening element can have an angle in the xz or yz plane deviating from 0 ° in relation to the z-axis direction in the thickness direction of the core composite structure (fig. 1a and 1b), for example an angle of +/-45 ° between the x-axis and the z-axis and/or between the y-axis and the z-axis being recommended for predominantly shear loads. After the force application point and the complete reinforcement of the core composite structure by the reinforcement structure, the textile cover layers and the through-openings, including the reinforcement structure, are impregnated with the polymeric matrix material in an LCM process, wherein a cohesive connection of the core material to the cover layers is simultaneously achieved. After the hardening of the core composite structure is completed, the textile reinforcing structure, which is wetted with the polymeric matrix material, forms unidirectional fiber-reinforced tension/compression bars within the core material, which serve to reinforce the force-transmitting locations, the core material and the entire core composite. The reinforcement structure here has the effect of increasing the peel strength between the force transfer element and the core composite structure and between the cover layer and the core layer, preventing the force transfer element from separating from the core composite structure, and improving the mechanical properties (strength in the thickness direction and stiffness characteristic) of the core material. The textile reinforcing structure can block or deflect cracks that are present in the critical region of the cover layer and the core layer. This improves the fail-safe properties of the force transmission points of the core composite. By adding the textile reinforcement structure in the region of the force transmission location in the thickness direction of the core composite structure, the compressive and tensile strength perpendicular to the plane of the core composite can be increased, the compressive and tensile stiffness perpendicular to the plane of the core composite can be increased, the compressive strength in the plane of the core composite can be increased, the shear strength and stiffness can be increased and the peel strength between the cover layer and the core layer and between the force transmission element and the cover layer can be increased, compared to known conventional force transmission schemes. Furthermore, the failure properties can be improved by the increased peel strength and by the "crack-blocking function" of the individual reinforcing elements, so that impact damage by force transmission and thus the so-called failure protection properties can be prevented. The force transmission element can be connected to the core composite structure in the correct position by means of industrial sewing techniques. By adding and providing a number of reinforcing elements, the quality reliability of the force transmission point in the core composite can be ensured. A further advantage of the invention is that the reinforcing element can be extended beyond the force transmission point into the core composite structure surrounding the force transmission point, as a result of which greater forces and moments can be introduced into the core composite structure.

In order to avoid the need for additional force transmission elements which adversely affect the weight of the core composite structure, the core material can be removed or compressed in the region of the force transmission points, whereby a splicing of the cover layers can be achieved. A further advantage is achieved in that the force transmission element has one or more flanges, as a result of which forces and moments can be transmitted into the core composite structure over a larger surface.

In order to be able to connect the force transmission element in a force-transmitting position in a force-locking and form-fitting manner to the entire core composite structure, the force transmission element has an opening for receiving the reinforcing element. This prevents separation of the force transfer element and increases the peel strength between the force transfer element and the core composite structure. If, due to technical requirements imposed on the structural components of the core composite (for example the hull of a ship in a building), it is necessary to avoid penetration of at least one of the cover layers of the core composite, a force transmission element (so-called outer insert) can be arranged on one or both of the cover layers.

In order to be able to transmit greater forces and moments into the core composite structure, the force transmission element (so-called insert) can also be arranged in one of the two cover layers or in both cover layers. Furthermore, the force transfer element may be positioned between the two cover layers, thereby partially or completely penetrating the core material.

A further advantage can be achieved by the application-dependent geometric and structural design of the force transmission element, i.e. by the force transmission element having one or more projections which bear against the or each cover layer, whereby the introduction of forces and moments can be improved due to the larger lever arm.

The invention provides the possibility of reinforcing the type of force transmission point in the core composite by removing or compressing the core material in the region of the force transmission point and by joining the two cover layers, so that a single fiber-plastic composite region is present. In this case, the upper covering layer 1 is connected to the lower covering layer 3 in the region of the force application point 5 by means of a perforated reinforcing element 4 inserted in the thickness direction of the core composite structure by means of a sewing technique (fig. 1a and 1 b). Furthermore, the reinforcing elements 4 can project beyond the force transmission points 6 into the core composite structure surrounding the force transmission points in order to withstand greater forces and moments and to improve the mechanical properties (fig. 1 c). The reinforced force transfer can be established by one of many LCM processes without force transfer elements for the core composite comprising the cover layers (1 and 3) of the textile semi-finished product, a core material 2 and a polymeric matrix material. In a working step prior to the addition of the polymeric matrix material, the core material is first removed or compressed in the region of the force-application location. The two cover layers are then joined together and the upper cover layer 1, the core material 2 and the lower cover layer 3 are sewn to one another in the force transmission region 5 and, if appropriate, beyond the force transmission region 6 by means of a woven reinforcing structure 4 in the thickness direction of the core composite structure by means of a sewing technique. The core composite structure, including the woven reinforcement structure, is then impregnated with a polymeric matrix material (e.g., a thermoset or thermoplastic) and cured in an LCM process (e.g., a resin injection or resin infusion process).

For the introduction of forces and moments, a force-transmitting element (outer insert, 7) can also be used, which is attached to the core composite structure (fig. 2a and 2 b). The outer insert is placed on one of the two cover layers (fig. 2a to 2f) or on both cover layers (fig. 2g) and is connected to the entire core composite structure in the thickness direction of the core composite structure in the region of the force transmission points by means of the reinforcing element 4. For accommodating the stiffening element, the outer insert has a bore 8. The outer insert can have a laterally projecting collar 9 (fig. 2c) which is arranged on the upper cover layer 1 or the lower cover layer 3 and likewise has openings 8 for receiving the reinforcing elements. For better transmission of forces and moments, the reinforcing elements 4 can be inserted into the core composite structure in the thickness direction of the core composite structure beyond the flange of the outer insert or outer insert 10 (fig. 2 d). Furthermore, the flange of the outer insert can have one or more projections 11 (fig. 2e and 2f) in order to better transmit forces and moments into the core composite structure. In a working step prior to the introduction of the polymeric matrix material, the outer insert part 7 and the core composite structure are sewn to one another in the force transmission region by the textile reinforcing structure 4 in the thickness direction of the core composite structure by means of industrial sewing techniques. The cover layers, core layer and textile reinforcing structure are then impregnated with a polymeric material and cured by an LCM process.

The force transmission point with a force transmission element (insert, 12) inserted into the core composite structure can thus be reinforced in that the upper cover layer 1, the core material 2 and the lower cover layer 3 are connected to one another outside the region of the inner insert by means of the reinforcing element 4 in the thickness direction of the core composite structure (fig. 3a and 3 b). A method for producing a force transmission point for a core composite comprising cover layers 1 and 3 of a textile semifinished product, a core material 2 and a polymeric base material by means of an inserted force transmission element 12, wherein, in a working step prior to the addition of the polymeric base material, the upper cover layer 1, the core material 2 and the lower cover layer 3 are sewn to one another outside the force transmission point by means of a textile reinforcing structure 4 inserted in the thickness direction of the core composite structure by means of a sewing technique. After the reinforcing structure is added, the core composite structure is impregnated with a polymeric material and allowed to harden in one of the possible LCM processes.

The insert 12 can also be connected to the core composite structure in the thickness direction thereof by means of the reinforcing element 4 (fig. 4a and 4 b). For this purpose, the insert has a hole 13 for receiving a reinforcing element. Furthermore, the insert can have a laterally projecting flange 14 (fig. 4c), which can be located inside the cover layers 1 and 3, in the core layer (2, fig. 4c) or between the cover layers and the core layer, and has holes 13 for receiving the textile reinforcing structure. The insert can also have two laterally projecting, spaced-apart flanges 14 (fig. 4d), which can be arranged inside the two cover layers (1 and 3), in the core layer (2, fig. 4d) or between the cover layers 1 and 3 and the core layer 2, and have holes 13 for receiving the reinforcing elements. For better transmission of forces and moments, the reinforcing elements 4 can be inserted into the core composite structure in the thickness direction of the core composite structure beyond the inner insert 12 or the flange 14 of the inner insert by 15 (fig. 4 e). To better transmit forces and moments into the core composite structure, the flange of the insert can have one or more extensions 16 (fig. 4f and 4 g). A method for producing a force transmission point for a core composite comprising cover layers 1 and 3 of a textile semifinished product, a core material 2 and a polymeric base material by means of an interposed force transmission element 12, wherein the insert is sewn to the core composite by means of a textile reinforcing structure 4 inserted in the thickness direction of the core composite by means of a sewing technique in a working step prior to the addition of the polymeric base material. After the reinforcing structure is added, the core composite structure, including the reinforcing structure and the insert, is impregnated with a polymeric material and allowed to harden in one of the possible LCM processes.

Drawings

The invention is described below by means of 13 embodiments, in which:

FIG. 1a shows a bottom view of the first embodiment;

FIG. 1b shows a cross-sectional view along line A-A in FIG. 1 a;

FIG. 1c shows a cross-sectional view along the line A-A in FIG. 1a, with a second variant for implementing the stiffening element;

FIG. 2a shows a top view of a third embodiment;

FIG. 2B shows a cross-sectional view along line B-B in FIG. 2 a;

FIG. 2c shows a cross-sectional view along line B-B in FIG. 2a, with a further variant for constructing the outer insert;

FIG. 2d shows a cross-sectional view along the line B-B in FIG. 2 a;

FIG. 2e shows a top view of the sixth embodiment;

FIG. 2f shows a cross-sectional view along the line C-C in FIG. 2 e;

FIG. 2g shows a top view of the seventh embodiment;

FIG. 2h shows a cross-sectional view along line D-D in FIG. 2 g;

FIG. 3a shows a top view of an eighth embodiment;

FIG. 3b shows a cross-sectional view along line E-E in FIG. 3 a;

FIG. 4a shows a top view of a ninth embodiment;

FIG. 4b shows a cross-sectional view along the line F-F in FIG. 4 a;

FIG. 4c shows a cross-sectional view along line F-F in FIG. 4a with another variation for constructing an interposer;

FIG. 4d shows a cross-sectional view along line F-F in FIG. 4a with another variation for constructing an interposer;

FIG. 4e shows a cross-sectional view along line F-F in FIG. 4a with one force transfer element (12, insert) embedded in the core composite structure;

FIG. 4f shows a top view of the thirteenth embodiment;

fig. 4G shows a cross-sectional view along the line G-G in fig. 4 f.

Detailed Description

Fig. 1a shows a bottom view of a first exemplary embodiment, comprising a force transmission site in a core composite with split cover layers 1 and 3, a core material 2 removed in the force transmission region and a reinforcing element 4 penetrating in the thickness direction of the core composite in the region of the force transmission site 5.

Fig. 1b shows a cross-sectional view along the line a-a in fig. 1 a.

Fig. 1c shows a section along the line a-a in fig. 1a with a second variant for the implementation of a stiffening element, wherein the stiffening element 4 projects beyond the force transmission point 6 into the core composite structure surrounding the force transmission point.

Fig. 2a shows a top view of a third exemplary embodiment with a force transmission element (7, outer insert: Onsert) which is placed on the upper covering layer 1 of the core composite structure and which is connected in the region of the force transmission points to the entire core composite structure in the thickness direction of the core composite structure via the reinforcing element 4 and has openings 8 for receiving the reinforcing element 4.

Fig. 2B shows a cross-sectional view along the line B-B in fig. 2 a.

Fig. 2c shows a section along the line B-B in fig. 2a, with a further variant for forming an outer insert with a laterally projecting collar 9 (fig. 2B) which is arranged on the upper covering layer 1 and likewise has openings 8 for receiving the reinforcing elements.

Fig. 2d shows a section along the line B-B in fig. 2a with a further variant for the implementation of a reinforcing element, which reinforcing element 4 projects beyond the force transmission point 10 into the core composite structure surrounding the force transmission point.

Fig. 2e shows a top view of a sixth exemplary embodiment with a force-transmitting element (7, outer insert) which is placed on the upper cover layer of the core composite structure and has an extension 11 in order to better transmit forces and moments into the core composite structure.

Fig. 2f shows a cross-sectional view along the line C-C in fig. 2 e.

Fig. 2g shows a top view of a seventh exemplary embodiment with two force transmission elements (7, outer inserts) which are placed on the upper cover layer 1 and the lower cover layer 3 of the core composite structure and which are connected in the region of the force transmission points to the entire core composite structure in the thickness direction of the core composite structure via the reinforcing elements 4 and have openings 8 for receiving the reinforcing elements 4.

Fig. 2h shows a cross-sectional view along the line D-D in fig. 2 g.

Fig. 3a shows a top view of an eighth exemplary embodiment with a force transmission element (12, Insert) embedded in the core composite structure, wherein the Insert is arranged between the two cover layers 1 and 3 inside the core material 2 of the core composite structure, and the upper cover layer 1, the core material 2 and the lower cover layer 3 are connected to one another outside the area of the Insert by means of a reinforcing element 4 in the thickness direction of the core composite structure.

Fig. 3b shows a cross-sectional view along the line E-E in fig. 3 a.

Fig. 4a shows a top view of a ninth exemplary embodiment with a force transmission element (12, insert) embedded in the core composite structure, wherein the insert is arranged between the two cover layers 1 and 3 in the core material 2 of the core composite structure and has a hole 13 for receiving the reinforcing element 4 and is connected to the core composite structure in the thickness direction of the core composite structure by means of the reinforcing element.

Fig. 4b shows a cross-sectional view along the line F-F in fig. 4 a.

Fig. 4c shows a sectional view along the line F-F in fig. 4a, with a further variant for the construction of an insert which has a laterally projecting collar 14 which bears against the upper cladding layer 1 and has openings 13 for receiving the reinforcing elements 4 and is connected to the core composite structure in the thickness direction of the core composite structure by means of the reinforcing elements.

Fig. 4d shows a sectional view along the line F-F in fig. 4a, with a further variant for the construction of an insert which has two laterally projecting flanges 14 which bear against the upper cover layer 1 and the lower cover layer 3 and which has openings 13 for receiving the reinforcing elements 4 and which is connected to the core composite structure in the thickness direction of the core composite structure by means of the reinforcing elements.

Fig. 4e shows a sectional view along the line F-F in fig. 4a, with a further variant for the construction of the reinforcement element, in which the reinforcement element 4 projects beyond the force transmission point 15 into the core composite structure surrounding the force transmission point.

Fig. 4f shows a plan view of a thirteenth exemplary embodiment with a force transmission element (12) embedded in the core composite structure, the insert having a laterally projecting collar 14 with an extension 16 for better transmission of forces and moments into the core composite structure and resting against the upper cladding layer 1, having a bore 13 for receiving the reinforcing element 4 and being connected to the core composite structure in the thickness direction of the core composite structure by means of the reinforcing element.

Fig. 4G shows a cross-sectional view along the line G-G in fig. 4 f.

Claims (11)

1. A force transmission point in a core composite, characterized in that the core composite has an upper cover layer (1), a lower cover layer (3) and a core layer (2), in which force transmission point the cover layers (1, 3) of the core composite are joined and a force transmission element (7, 12) is provided, and in which force transmission point the core composite structure is reinforced by a reinforcing element (4) penetrating in the thickness direction of the core composite, the force transmission element (7, 12) having one or more flanges (9, 14).

2. Force transmission site in a core composite according to claim 1, characterized in that the reinforcement element (4) extends beyond the force transmission site into the core composite structure surrounding the force transmission site.

3. Force transmission site in a core composite according to claim 1 or 2, characterized in that the cover layers (1, 3) consist of textile semi-finished products, the core layer (2) of the core composite consists of polymeric or natural core material, and the reinforcement element (4) consists of a textile reinforcement structure, and that the cover layers, core layer and reinforcement element are embedded in a polymeric matrix material.

4. A force transmission location in a core composite according to claim 1 or 2, characterised in that the force transmission element has holes (8, 13) for accommodating the reinforcement element (4) and is connected to the core composite structure in the thickness direction of the core composite structure by the reinforcement element in the region of the force transmission location.

5. Force transmission site in a core composite according to claim 1 or 2, characterized in that the force transmission element is arranged on one of the two cover layers (1, 3) or on both cover layers (1, 3).

6. Force transmission site in a core composite according to claim 1 or 2, characterized in that the force transmission element is arranged inside one of the two cover layers (1, 3) or inside both cover layers (1, 3).

7. A force transmission location in a core composite according to claim 3, characterised in that the force transmission element is arranged between two cover layers (1, 3) and/or penetrates the core material (2).

8. A force transfer location in a core composite according to claim 1 or 2, characterized in that the force transfer element has one or more protrusions (11, 16) abutting against one of the cover layers (1, 3) or against each cover layer.

9. A method for producing a force transmission site in a core composite according to any one of claims 1 to 8, characterized in that in a working step prior to the introduction of the polymeric matrix material, in the region of the force transmission site, the force transmission element (7, 12) and the core composite structure are sewn to one another in the thickness direction of the core composite structure by means of textile reinforcing elements (4) introduced by means of sewing technology.

10. A method for producing a force transmission site in a core composite according to any one of claims 1 to 8, characterized in that, in a working step prior to the introduction of the polymeric matrix material, the upper (1), core and lower (3) cover layers are sewn to one another outside the region of the force transmission element in the thickness direction of the core composite structure by means of textile reinforcing elements (4) introduced by means of sewing technology in the region of the force transmission site.

11. Use of a force transfer location according to any one of claims 1 to 8 for the construction of a spacecraft, an aircraft, a watercraft or a land craft.