DE102017119940A1 - Force application element - Google Patents

Abstract

The present invention relates to a force introduction element (2, 4) for a sandwich structure (1) with a first cover layer (10), with at least one core (13) and with a second cover layer (14) along a longitudinal axis (X), with an insert element (2), wherein the insert element (2) has a contact region (20) for the first cover layer (10), which is formed with the first cover layer (10) to make a planar contact in the direction of the longitudinal axis (X), wherein the insert element (2) is adapted to extend from the abutment region (20) for the first cover layer (10) along the longitudinal axis (X) through the sandwich structure (1). The force introduction element (2, 4) is characterized by a holding element (4) which is designed to produce a planar contact with the second cover layer (14) in the direction of the longitudinal axis (X), wherein the insert element (2) has a contact surface (26). for the holding element (4), which is designed to receive the holding element (4) along the longitudinal axis (X) at a predetermined distance from the abutment region (20) for the first covering layer (10).

Description

The present invention relates to a force introduction element according to the preamble of patent claim 1 and to a sandwich structure with such a force introduction element according to claim 12.

In various technical fields so-called sandwich panels with an intermediate material such as e.g. used with a honeycomb core, which may also be referred to as sandwich structures. Alternatively to a honeycomb core, e.g. also foam or wood can be used. A sandwich panel is understood to mean a sandwich structure usually composed of three layers, which consists of two load-bearing cover layers and a central support core or even core, e.g. in honeycomb form. The support core in honeycomb form is referred to in English as "Honeycomb" (German: honeycomb). Depending on the application, the support core is usually made of cardboard, resin-impregnated paper, fiber-reinforced plastic or thin aluminum foils. The cover layers may consist of cardboard, plastic, fiber composite material or sheet metal. Various material combinations of support core and cover layers are possible. The support core and the cover layers are usually glued together.

The sandwich structure or even the sandwich plate adopts the principle of the double-T-beam for the tensile structure, because the thin cover layers with their large distance to the center plane for a large moment of inertia and thus provide a high bending stiffness while the support core generates shear stiffness and the cover layers continuously supports against bumps and wrinkles. Honeycomb core sandwich panels are mainly found in the technical areas where lightweight construction plays an important role. By way of example, the vehicle construction such as Aerospace, automotive and shipbuilding.

Sandwich structures have by their construction a very high bending and buckling stiffness with a low weight. The core as such is usually very brittle, porous or has a holey structure. Therefore, no large forces, in particular no punctual pressure forces, can be introduced into the core. Thus, it is expedient, forces only on the outer layers or divert.

It is advantageous if, on the one hand, the occurring forces are equally introduced into both cover layers. If multi-layer cover layers are used, the transfer of force to the other should take place in all layers within the laminate of a cover layer.

In order to create fastening possibilities between a sandwich structure and a further component, it is customary to introduce into the sandwich structure so-called force introduction elements, which are also referred to as inserts or sandwich inserts. The force introduction elements can only protrude from one side through the cover layer into the core, penetrate the sandwich structure or be arranged in a passage opening of the sandwich structure. The connection between force application element and sandwich structure can be done in many ways.

In general, drip or sandwiched inserts are known, which are subsequently integrated into "hot bonded inserts", which are integrated during production with foaming adhesive, and "cold bonded inserts" Resin can be poured, can be divided. Both variants use the bonded with foam adhesive or resin interfaces of Sandwichinserts against the core and the outer layers for introducing force into the sandwich structure. Due to the integration into the production, the "hot bonded insert" can be glued to the surface layers during curing. The "cold bonded insert", on the other hand, has no top layer on the top and has no contact with the underlying layers, but has the advantage that the resin offers better force transmission than the soft adhesive foam.

For the design of the force introduction elements usually the load forms normal force to train and / or pressure, shear, bending and torsion are taken into account, the most frequently considered load is the tensile and compressive forces in the normal direction.

The major failures in the known inserts are, firstly, the shear failure of the core around the insert, with short insert geometries caused by the limited shear stiffness of the core, and second, the tensile / compressive failure of the core for very long inserts. caused by the lower compressive strength of the core.

The strength of the foam is a limiting factor in the transmissible force. An already considered approach to circumvent this limitation is the enlargement of the insert diameter and thus the enlargement of the bonding surface. However, this leads to larger and therefore more expensive inserts in terms of manufacturing and assembly costs. Furthermore, large inserts may not be desirable in all applications. Besides, they are large inserts relatively heavy, which is the main disadvantage of sandwich structures, which are mainly used in lightweight construction.

The US 5,093,957 A describes an insert for through holes of sandwich structures, which consists of two components. Both components have a flat area, with which they can rest on one side of the sandwich structure on the respective outer layer from the outside. Facing one another, the two components are formed, so that a component can be introduced into the other component along its common longitudinal axis. In this position, the two components are encapsulated from the outside with respect to the outer layers and the core by means of an epoxy resin. A force transmission between the two cover layers can thus take place along the longitudinal axis only via the epoxy resin but not via the two components of the insert.

From the US 3,564,798 A an insert for through holes of sandwich structures is known, which lies flat against the outside of a first cover layer by means of a flat region on one side of the sandwich structure from the outside and protrudes with its body through a through hole of the sandwich structure. The insert occurs with a threaded area on the second cover layer, so that there placed on the insert a component and can be secured from the outside with a nut. The insert is attached with resin in the core. By tightening the nut, compressive forces can be exerted on the sandwich structure from the flat area of the insert on one side and through the nut or the component from the opposite side, which can impress the sandwich structure.

The US 3,678,535 A describes an insert for through holes of sandwich structures, which consists of two components. Both components have a flat area, with which they can rest on one side of the sandwich structure on the respective outer layer from the outside. Facing one another, the two components are formed, so that a component can be pressed into the other component along its common longitudinal axis. As a result, the two areal areas of the insert parts can exert pressure forces on the sandwich structure, which can impress the sandwich structure.

The US 4,981,735 A describes an insert for through holes of sandwich structures, which consists of two components. Both components have a flat area, with which they can rest on one side of the sandwich structure on the respective outer layer from the outside. Facing one another, the two components are formed, so that a component can be screwed into the other component along its common longitudinal axis. As a result, the two areal areas of the insert parts can exert pressure forces on the sandwich structure, which can impress the sandwich structure. The DE 10 2012 202 331 A1 describes a comparable insert.

The US 4,170,919 A describes an insert for through holes of sandwich structures, which consists of two components. A first component has a flat region, with which it can rest on one side of the sandwich structure on a first outer layer from the outside. Furthermore, the first component clearly protrudes through a through hole of the sandwich structure and beyond the second cover layer. The first component itself has a through-hole and the cylindrical wall region of the first component has slots in the longitudinal direction in the region with which it projects beyond the second cover layer. The second component is configured to be passed through the through hole of the first component from the side of the second cover layer. In this case, the second component has a head region, which can sit in the longitudinal direction on the edge of the cylindrical slotted edge region of the first component. At the same time, the second component protrudes beyond the first component on the side of the first cover layer, so that the second component can be pulled from there.

Now, another component can be inserted with a through opening on the insert on the side of the second cover layer to rest on the second cover layer. Then, the second component of the insert can be pulled, so that the slotted edge region of the first component bends outwardly, thereby shortening the first component and the further component is clamped on the second cover layer. In this way, the two components of the insert can exert compressive forces on the sandwich structure, which can impress the sandwich structure. The second component of the insert can finally be removed or broken off.

The US 2006 137 294 A1 describes an insert for through holes of sandwich structures, which consists of a component. The insert has on one side a flat area, with which it can rest on one side of the sandwich structure on the outer layer from the outside. To the opposite side of the sandwich structure, the insert projects slightly beyond the top layer with a thin edge. The thin edge can be bent radially outward to a flat area, so that the edge of the through hole of the sandwich structure is pressed by the bent edge of the insert.

It is disadvantageous in the known force introduction elements that they can press through at least one cover layer or even both cover layers of the sandwich structure during their attachment through a passage opening of a sandwich structure and thereby deform. Furthermore, the forces which may result from the assembly of the force introduction element must be borne by the sandwich structure. Another disadvantage is that often the core is claimed because forces are introduced directly into this or the core must selectively absorb pressure forces or even tensile forces. As a result, the cover layer or the cover layers can be damaged.

A further disadvantage is that in the known force introduction elements by the use of resin or foam adhesive in the region of the core, an additional effort in the production arises. This can also increase the mass of the sandwich structure, which is highly undesirable in lightweight construction.

Another disadvantage is that the known force introduction elements are designed to be relatively stiff, so that the cover layers, in particular in the use of fiber plastic layers, shear at moments loads and thus can be damaged and weakened.

An object of the present invention is to provide a force introduction element of the type described above, which can be arranged through a sandwich structure, without depressing at least one cover layer, preferably without both cover layers. Alternatively or additionally, as even as possible a force transmission between the force introduction element and the cover layers should take place. In particular, this should be made possible for multi-layer cover layers. This should preferably be implemented as simply as possible. At least one alternative to known force introduction elements should be provided.

The object is achieved by a force introduction element having the features of patent claim 1 and by a sandwich structure with the features of claim 12. Advantageous developments are described in the subclaims.

Thus, the present invention relates to a force introduction element for a sandwich structure with a first cover layer, with at least one core and with a second cover layer along a longitudinal axis. The force introduction element has an insert element, wherein the insert element has a contact region for the first cover layer, which is designed to produce a planar contact with the first cover layer in the direction of the longitudinal axis. The insert element is further configured to extend from the abutment region for the first cover layer along the longitudinal axis through the sandwich structure.

The force introduction element is characterized in that it further comprises a holding element which is designed to produce a flat contact with the second cover layer in the direction of the longitudinal axis. In this case, the insert element has a contact surface for the retaining element, which is designed to receive the retaining element along the longitudinal axis at a predetermined distance from the abutment region for the first cover layer.

Thus, the force introduction element is formed with its insert element over the contact area for the first cover layer making a planar contact with the first cover layer and with its holding element making a planar contact with the second cover layer. In this way, tensile and compressive forces can be exchanged in the direction of the longitudinal axis between the force introduction element and the two cover layers of the sandwich structure.

In this case, however, an impressions of the outer layers can be prevented by the fact that the holding element and the insert element can support one another on its contact surface such that the predetermined distance, which is thereby defined, can not be undershot. Thus, although tensile and compressive forces can be exchanged in the direction of the longitudinal axis between the force introduction element and the two cover layers of the sandwich structure, the cover layers can not be pressed in this case because the force flow always takes place via the retaining element and the insert element. As a result, mechanical loads can be derived in the direction of the longitudinal axis via the force introduction element and kept away from the sandwich structure. The holding element can in turn serve as a contact surface for a component to be fastened.

The sandwich structure has, with the first cover layer and with the second cover layer along a longitudinal axis, at least two layers in total, between which a core can be arranged. However, at least one further layer between the two cover layers may also be arranged at least in sections within the one core. In particular, this another layer may be arranged between the two cover layers, so that two cores are formed. Preferably, this may be another layer in the 0 ° -layer in the vertical direction be arranged centrally between the two cover layers, ie in the neutral chamfer.

According to one aspect of the present invention, the contact surface for the holding element of the insert element is formed to terminate flush with the second cover layer along the longitudinal axis, so that the holding element in the direction of the longitudinal axis in planar contact both with the contact surface for the holding element of the insert element as well as with second cover layer can be added. In this way, a direct surface contact between the holding element and the second cover layer can be achieved, so that a flat as possible construction in the direction of the longitudinal axis can be achieved.

According to a further aspect of the present invention, the contact surface for the holding element of the insert element is formed to terminate flush with an adhesive layer of the second cover layer along the longitudinal axis, so that the holding element in the direction of the longitudinal axis in planar contact with both the contact surface for the holding element of the insert element can also be absorbed with the adhesive layer of the second cover layer. In this way, an indirect surface contact between the holding element and the second cover layer can be achieved via an intermediate adhesive layer, so that a cohesive grip of the holding element on the second cover layer can be made possible and still retain the properties and advantages described above.

According to a further aspect of the present invention, the insert element has a connection region to the first cover layer, which is designed to extend along the longitudinal axis as far as the first cover layer. In this way, a region of the insert element can be created, which can be adapted to the contact with the first cover layer. The connection region to the first cover layer is preferably non-rotationally symmetrical. This can e.g. via the geometry or via the contour of the connection area, as will be explained in more detail below.

According to a further aspect of the present invention, the contact region for the first cover layer is part of the connection region to the first cover layer. In this way, the abutment region along the longitudinal axis can be integrated into the first cover layer, so that a protrusion of the insert element along the longitudinal axis beyond the first cover layer can be avoided. Furthermore, the abutment region can be integrated into the first cover layer in such a way that the abutment region of the insert element and the outer surface of the first cover layer are flush with one another so that both elevations and depressions are avoided at this point and a completely smooth outer surface of the sandwich structure is created can.

According to a further aspect of the present invention, the insert element has a spacing region which extends from the connection region to the first cover layer along the longitudinal axis as far as the core of the sandwich structure, the spacer region being at least partially radially smaller than the connection region to the first cover layer , so that the connection region to the first cover layer merges at least in sections with a contact surface into the distance region. In this way, a defined positioning of a spacer can take place via the contact surface, which can be flush with the first cover layer. At the same time, the spacer can be supported both on the contact surface and on the inner surface of the first cover layer in planar contact. As a result, the first cover layer can be enclosed on both sides by the spacer and the abutment region along the longitudinal axis, so that the edge of the first cover layer or the edges of individual layers of the first cover layer can be held and protected against bending etc.

According to a further aspect of the present invention, the insert element has a connection region to the second cover layer, which is designed to extend along the longitudinal axis as far as the second cover layer, wherein the connection region to the second cover layer is preferably non-rotationally symmetrical. As a result, the properties and advantages which have been described in this regard in terms of the connection area to the first cover layer can also be implemented with respect to the second cover layer.

According to a further aspect of the present invention, the connection region to the second cover layer extends along the longitudinal axis with the contact surface for the retaining element. This allows a direct and flush termination between the second cover layer and the holding element, so that both a distance between the second cover layer and the holding element and a depression of the second cover layer can be avoided by the holding element.

According to a further aspect of the present invention, the connection region to the first cover layer is designed to hold the first cover layer, preferably at least one layer of the first cover layer, in a form-fitting manner and / or the connection region to the second cover layer Cover layer is formed to hold the second cover layer, preferably at least one layer of the second cover layer, in a form-fitting manner. The positive connection can be achieved by a non-rotationally symmetrical design of the respective connection region. By a form fit in the circumferential direction about the longitudinal axis around a twisting of the force introduction element relative to the sandwich structure can be avoided or at least made more difficult. As a result, forces in the circumferential direction, ie torsional forces can be transmitted. For example, the contour of the insert element in the connection region to the first cover layer can be oval, elliptical or angular, in particular hexagonal or octagonal, in order to achieve the aforementioned advantages.

According to a further aspect of the present invention, the insert element has at least one securing element, which is designed to permit the holding element to be arranged on the contact surface in a first state and to hold the holding element on the contact surface in a second state. In this way, a possibility to hold the holding element on the contact surface of the insert element and to fix, be created directly by the insert element itself. On the one hand, this can make it possible to hold the holding element in operation without the need to use additional components and, in particular, to provide and assemble them. Additionally or alternatively, the securing of the retaining element by means of securing element can serve to assemble, so that a completion of the sandwich structure, e.g. can be done in an autoclave with secured holding element. Also, the holding member can be made in this manner e.g. serve as a backup for the duration of curing of an adhesive.

For this purpose, preferably form the securing element as a flanged edge, preferably with a material weakening to define a bending point, may be advantageous because a flanging can be made easily, quickly and without additional components and at the same time can be very durable. For this purpose, to define the bending point of the flanged edge by weakening the material may be advantageous in order to predefine a defined holding force and holding position of the flanging edge, which can be reliably reproducible and / or simple.

According to a further aspect of the present invention, the abutment region for the first cover layer along the longitudinal axis has a thickness which corresponds to at least one layer of the first cover layer, preferably exactly one layer of the first cover layer, particularly preferably exactly the outermost layer of the first cover layer. As a result, the contact area for the first cover layer can be integrated into the first cover layer without noticeably reinforcing it and increasing it at this point. If the surface of the first cover layer or of a layer of the first cover layer that corresponds to the contact region for the first cover layer is preferably recessed, then the contact region for the first cover layer can be integrated into the first cover layer without actually increasing it. In other words, the contact area for the first cover layer is integrated into the layer of the cover layer, so that a thickening of the first cover layer can be avoided, which could lead to a decrease in strength due to the deflection of the fibers of the layers. In any case, the best possible connection between the contact area for the first cover layer and the first cover layer can be achieved.

The present invention also relates to a sandwich structure with a first cover layer, with at least one core and with a second cover layer, which are arranged along a longitudinal axis, and with at least one force introduction element, preferably a plurality of force introduction elements, as described above. As a result, the properties and advantages of the force introduction element described above can be used in a sandwich structure.

According to one aspect of the present invention, the sandwich structure comprises a spacer, which is arranged at least in sections around a spacing region of the insert element and extends along the longitudinal axis as far as the core of the sandwich structure, the spacer having a first contact surface both with a contact surface the insert element as well as with the first cover layer is in surface contact and or or wherein the spacer is in surface contact with a second contact surface with the second cover layer.

Due to the respective areal contact with the first or second cover layer, the spacer can hold and support the respective cover layer along the longitudinal axis so that its edges can not be bent over. Also fibers of the outer layers can not shear out by moment loads.

Due to the flat contact of the spacer with the contact surface of the insert element forces between the spacer and the insert element can be exchanged and thereby kept away from the first cover layer. This can prevent impressions of the first cover layer.

According to a further aspect of the present invention, the first cover layer and / or or the second cover layer has at least one layer, preferably a fiber-plastic layer, which has an insert around the insert element at least in sections, the insert preferably being non-rotationally symmetrical.

As a result, a reinforcement of the respective cover layer around the insert element can take place. Also, a better connection between the cover layer and the insert element can be achieved by the enlarged contact surface with respect to the cover layer, so that forces can be exchanged by the radial positive connection between insert and insert element. If several layers of a cover layer are present, the insert can be arranged between two layers of a cover layer. Preferably, the surface of the cover layer or a layer of the cover layer is recessed, which corresponds to the insert, so the insert can be integrated into the cover layer without increasing it. As a result, a thickening, as already described above, be avoided. If a cover layer has several layers, then several inserts can be used in different layers, preferably two inserts can be spaced apart from one another by at least one layer of the cover layer. The depositors can be identical or differently formed or aligned.

In this case, the insert non-rotationally symmetrical provided may be advantageous to achieve a positive connection in the circumferential direction. As a result, forces in the circumferential direction about the longitudinal axis, i. Torsionskräfte be replaced, as previously described. For this purpose, the inner contour of a recess of the insert or the insert is adapted to the outer contour of the respective connection region of the insert element.

The insert may have different materials or consist of different materials. Preferably, the insert may consist of a metal or a plastic. If multiple inserts are used, they may consist of the same material or of different materials or have different materials.

The insert may preferably be formed of metal, and more preferably of stainless steel, or of another metal with an anticorrosive coating to prevent corrosion and thus provide a durable insert.

According to a further aspect of the present invention, the contact area for the first cover layer along the longitudinal axis is held with an adhesive layer on the first cover layer and / or the holding element is held along the longitudinal axis with an adhesive layer on the second cover layer. As a result, a direct contact without adhesive layer or an indirect contact via adhesive layer can be made possible. The positioning of the contact surface for the holding element is to be carried out correspondingly along the longitudinal axis, so that the advantages described above can be achieved in both cases.

• 1 eine schematische Schnittdarstellung eines erfindungsgemäßen Krafteinleitungselements gemäß eines ersten Ausführungsbeispiels in einer Sandwichstruktur;
• 2a einen ersten Querschnitt A-A der 1;
• 2b einen zweiten Querschnitt B-B der 1;
• 3 eine Explosionsdarstellung des Krafteinleitungselements der 1 ohne Sandwichstruktur mit Abstandshalter;
• 4 eine Detaildarstellung der 1 in einem ersten Zustand (links) und in einem zweiten Zustand (rechts); und
• 5 eine schematische Schnittdarstellung eines erfindungsgemäßen Krafteinleitungselements gemäß eines zweiten Ausführungsbeispiels in einer Sandwichstruktur.

Two embodiments and further advantages of the invention are explained below in connection with the following figures. It shows:

• 1 a schematic sectional view of a force introduction element according to the invention according to a first embodiment in a sandwich structure;
• 2a a first cross-section AA of the 1 ;
• 2 B a second cross section BB of the 1 ;
• 3 an exploded view of the force introduction element of 1 without sandwich structure with spacer;
• 4 a detailed view of the 1 in a first state (left) and in a second state (right); and
• 5 a schematic sectional view of a force introduction element according to the invention according to a second embodiment in a sandwich structure.

The above figures are considered in cylindrical coordinates. It extends a longitudinal axis X in a vertical direction Z , which also as height Z can be designated. Perpendicular to the longitudinal axis X extends a radial direction R away from this.

1 shows a schematic sectional view of a force introduction element according to the invention 2 . 4 according to a first embodiment in a sandwich structure 1 , 2a shows a first cross-section AA of the 1 , 2 B shows a second cross section BB of the 1 , 3 shows an exploded view of the force introduction element 2 . 4 of the 1 without sandwich structure 1 with spacers 3 , 4 shows a detailed representation of the 1 in a first state (left) and in a second state (right). The force introduction element 2 . 4 according to the first embodiment is provided during the manufacture of the sandwich structure 1 to be integrated into these.

The sandwich structure 1 exists along the longitudinal axis X from bottom to top, cf. eg 1 . from a first cover layer 10 , from a core 13 as well as from a second cover layer 14 , The first cover layer 10 is multi-layered and consists of several fiber plastic layers 11 which partially around the force introduction element 2 . 4 around by depositor 12 are replaced. This also applies to the second cover layer 14 which have multiple fiber-plastic layers 15 as well as depositors 16 having. The warehouses 12 . 16 are here as a metal insert 12 . 16 made of stainless steel.

The force introduction element 2 . 4 consists of two components, namely an insert element 2 , which also as an insert 2 or as the centerpiece 2 can be designated, and from a holding element 4 , which also as a cover 4 can be designated.

The insert element 2 is integrally formed and begins, along the longitudinal axis X from bottom to top, cf. eg 1 and 3 , with an investment area 20 for the first cover layer 10 the sandwich structure 1 , The investment area 20 for the first cover layer 10 corresponds in strength to the strength of a fibrous plastic layer 11 the first cover layer 10 so that the investment area 20 of the insert element 2 a fibrous plastic layer 11 , here the lowest or the furthest fiber plastic layer 11 , the first cover layer 10 can replace sections. For this purpose, the investment area extends 20 for the first cover layer 10 radially further than the rest of the insert element 2 ,

The insert element 2 also has a connection area 21 to the first cover layer 10 on, which along the longitudinal axis X is as well formed as the first cover layer 10 , Furthermore, the investment area 20 for the first cover layer 10 Part of the connection area 21 to the first cover layer 10 and closes with this along the longitudinal axis X downwards. The connection area 21 to the first cover layer 10 is cylindrical and thus rotationally symmetrical, see for example 2 B ,

Along the longitudinal axis X at the top closes a cylindrical distance range 22 to the connection area 21 to the first cover layer 10 at. The distance range 22 extends exactly over the height of the core 13 the sandwich structure 1 , Here is the distance range 22 radially lower than the connection area 21 to the first cover layer 10 designed so that the connection area 21 to the first cover layer 10 by means of an edge 23 or level 23 in the distance range 22 merges, creating along the longitudinal axis X from above a contact surface 23 for a spacer 3 is formed, as will be explained below.

At the distance range 22 closes along the longitudinal axis X up a connection area 24 to the second cover layer 14 which is about the height of the second cover layer 14 extends. The connection area 24 to the second cover layer 14 is octagonal shaped, see eg 2a , The connection area 24 to the second cover layer 14 closes along the longitudinal axis X up flush with the outer surface of the second cover layer 14 from. In this case, forms the insert element 2 at this point a contact surface 26 for the holding element 4 out.

At the same time begins with the contact surface 26 for the holding element 4 a graduation area 25 of the insert element 2 , which extends upwardly and is formed radially smaller than the connecting region 24 to the second cover layer 14 , The graduation area 25 has a fuse element 27 in the form of a flanged edge 27 which is in a first state along the longitudinal axis X straight upwards, see eg 4 , left, and in a second state bent radially outward, see eg 4 , right. In order to allow a defined bending, the crimping edge points 27 a material weakening 27a as a bending point 27a on, see eg 4 , Left.

In its interior, the insert element 2 a recess 28 on, which in the two embodiments as a blind hole 28 with internal thread 29 is formed, but for example, a through hole with or without internal thread 29 can be. Alternatively, a stud with or without external thread could be provided which extends radially within the flanged edge 27 along the longitudinal axis X extends upwards. Other structural elements can also be used, depending on the purpose of the sandwich structure 1 a connection of the force introduction element 2 . 4 to allow for other components.

The holding element 4 is integrally formed as a circular disc and can therefore also as a cover 4 be designated. The holding element 4 points along the longitudinal axis X a passage opening 40 on, with the holding element 4 along the longitudinal axis X straight raised flange 27 on the insert element 2 can be put on. The radially inwardly pointing region of the holding element 4 which the passage opening 40 encloses, thereby forms an investment area 41 in the form of an edge 41 or level 41 out, which along the longitudinal axis X flatter than the rest of the holding element 4 is trained. The investment area 41 points along the longitudinal axis X down a first contact surface 42 on which the surface contact with the contact surface 26 of the insert element 2 serves. The investment area 41 also points along the longitudinal axis X to the top one second contact surface 43 on which the contact with the bent flange 27 of the insert element 2 serves. Here is the holding element 4 along the longitudinal axis X formed such that the bent flanging edge 27 so flat on the second support surface 43 of the investment area 41 can rest, so that the bent flange 27 along the longitudinal axis X not up over the retaining element 4 protrudes.

As an additional element show the 1 and 3 a spacer 3 , which also as a spacer 3 can be designated. The spacer 3 is cylindrical along the longitudinal axis X formed and has a passage opening 30 on, with which of the spacers 3 over the distance range 22 of the insert element 2 can be arranged. The spacer 3 points to this along the longitudinal axis X down a first contact surface 31 on, with the spacer 3 both on the corresponding contact surface 23 of the insert element 2 as well as on the inner surface of the first cover layer 10 can sit up. Along the longitudinal axis X facing upwards is the spacer 3 a second contact surface 32 for a surface contact with the inner surface of the second cover layer 14 on.

The insert element 2 and the retaining element 4 of the force introduction element 2 . 4 be according to the first embodiment of the 1 to 4 during the production of the sandwich structure 1 together with the spacer 3 now used as follows:

First, the insert element 2 with the investment area 20 for the first cover layer 10 placed on a surface of a mold. Then a first fibrous plastic layer 11 the first cover layer 10 with a recess, which is the contour of the contact area 20 for the first cover layer 10 of the insert element 2 corresponds to the insert element 2 placed around on the surface of the mold. This forms the investment area 20 for the first cover layer 10 of the insert element 2 and the first fibrous plastic layer 11 together the first, lowest, outermost layer of the first cover layer 10 ,

Now, a first metal insert 12 along the longitudinal axis X from above over the insert element 2 on the first location 11 the first cover layer 10 placed. The first metal insert 12 has for this purpose a passage opening, which in its circular inner contour of the cylindrical outer contour of the connecting region 21 to the first cover layer 10 of the insert element 2 equivalent. The outer contour of the first metal insert 12 is oval and thus non-rotationally symmetrical. Radially protrudes the first metal insert 12 over the investment area 20 for the first cover layer 10 of the insert element 2 out.

Subsequently, a second fiber plastic layer 11 about the first location 11 the first cover layer 10 placed. The second fibrous plastic layer 11 in this case has a recess, which with respect to their inner contour and orientation of the outer contour and orientation of the first metal insert 12 equivalent. The strength of the first metal insert 12 corresponds to the strength of the second fibrous plastic layer 11 , The second fibrous plastic layer 11 and the first metal insert 12 together form the second layer of the first cover layer 10 ,

Now, a third fiber plastic layer 11 over the second layer of the first cover layer 10 placed. For this purpose, the third fiber plastic layer 11 a recess, which with respect to its inner contour of the cylindrical outer contour of the connecting region 21 to the first cover layer 10 of the insert element 2 equivalent. The third fiber plastic layer 11 forms the third layer of the first cover layer 10 ,

Finally, now a second metal insert 12 which is the first metal insert 12 corresponds, as well as a fourth fiber plastic layer 11 as the fourth layer of the first cover layer 10 on the third layer of the first cover layer 10 placed as described above. In this case, the second metal insert 12 an offset orientation about the longitudinal axis X around the first metal insert 12 on, giving the orientation of the metal insert 12 the chamfer of the fourth fiber plastic layer 11 can be adjusted, see eg 1 For example, in a layer structure of 0 ° of the first metal insert 12 to 90 ° of the second metal insert 12 , The second metal insert closes 12 and thus also the inner surface of the first cover layer 10 along the longitudinal axis X upwards with the connection area 21 for the first cover layer 10 from. This creates a flush transition between the inner surface of the first cover layer 10 and the contact surface 23 for the spacer 3 of the insert element 2 , see eg 1 , In this way, a hybrid material zone of the first cover layer 10 with increased strength and improved connection to the insert element 2 be created.

Now the spacer will be 3 along the longitudinal axis X from above with its passage opening 30 on the insert element 2 plugged, leaving the first contact surface 31 of the spacer 3 both the inner surface of the first cover layer 10 as well as the contact surface 23 for the spacer 3 of the insert element 2 contacted flatly. As a result, on the one hand, the second to fourth layer of the first cover layer 10 between the plant area 20 for the first cover layer 10 of the insert element 2 and the first contact surface 31 of the spacer 3 be held so that the layers of the first cover layer 10 at moment loads not along the longitudinal axis X can shear out. On the other hand, forces can occur between the spacer 3 and the insert element 2 over its contact surface 23 for the spacer 3 be replaced without the first cover layer 10 to charge.

To the spacer 3 is now the core 13 on the inner surface of the first cover layer 10 placed, which has a recess corresponding to the outer contour of the spacer 3 having. The core 13 closes along the longitudinal axis X upwards with the distance range 22 of the insert element 2 from.

Subsequently, the construction of the second cover layer takes place 14 , which is comparable to the first cover layer 10 from fiber-reinforced plastic layers 15 exists, which alternately over the entire surface or with metal inserts 16 are provided. Unlike the connection area 21 to the first cover layer 10 indicates the connection area 24 to the second cover layer 14 However, a non-rotationally symmetrical outer contour in the form of an octagonal outer contour, see for example 2a , so that the inner contours of the fiber-plastic layers 15 and the metal insert 16 the second cover layer 14 are designed accordingly. As a result, in the circumferential direction about the longitudinal axis X around a positive connection between the layers of the second cover layer 14 and the connection area 24 to the second cover layer 14 of the insert element 2 which also provides torsional forces in the circumferential direction about the longitudinal axis X can record around.

The second cover layer closes 14 along the longitudinal axis X upwards with the connection area 24 to the second cover layer 14 of the insert element 2 from. This creates a flush transition between the outer surface of the second cover layer 14 and the contact surface 26 for the holding element 4 , see eg 1 and 4 ,

Finally, now the holding element 4 with its first contact surface 42 along the longitudinal axis X from above over the crimping edge 27 of the insert element 2 on its contact surface 26 placed. As a result, on the one hand, a planar contact of the underside of the holding element 4 with the outer surface of the second cover layer 14 causes, so that the layers of the second cover layer 14 along the longitudinal axis X between the holding element 4 and the second contact surface 32 of the spacer 3 being held. In this way can also for the second cover layer 14 avoid the layers of the second cover layer 14 at moment loads along the longitudinal axis X can shear out. On the other hand, at the same time a surface contact between the holding element 4 and the insert element 2 over its contact surface 26 for the holding element 4 achieved through the forces can be exchanged without the sandwich structure 1 to load and depress.

To the holding element 4 to hold in this position now becomes the flanging edge 27 of the insert element 2 bent radially outwards, cf. eg 1 and 4 , left and right. This allows the holding element 4 easy, fast and secure to be fixed for mounting, allowing the force application element 2 . 4 also held in the non-cured state of the sandwich structure and the sandwich structure 1 can be handled. In this case, also the required assembly forces on the contact surface 26 for the holding element 4 be routed without the sandwich structure 1 to load and depress.

In this way, a force introduction element 2 . 4 as well as a sandwich structure 1 be created, which the exchange of forces between the force application element 2 . 4 and the sandwich structure 1 can allow without the sandwich structure 1 this burdened, pressed and thus damaged. Also, a secure hold of the insert element 2 opposite the two cover layers 10 . 14 be achieved.

5 shows a schematic sectional view of a force introduction element according to the invention 2 . 4 according to a second embodiment in a sandwich structure 1 , The sandwich structure 1 in this case only has several fiber-plastic layers 11 . 15 per cover layer 10 . 14 but no metal inserts on.

The force introduction element 2 . 4 According to the second embodiment is provided, subsequently in a drilled through hole of a cured sandwich structure 1 to be used, which is cylindrical in the second embodiment, but could also be angular, oval, elliptical, star-shaped or the like.

The investment area is corresponding 20 for the first cover layer 10 formed along the longitudinal axis X from below against the outer surface of the first cover layer 10 abut and over an adhesive layer 5 to be connected to this materially. In the further course along the longitudinal axis X upwards follows a connection area 21 to the first cover layer 10 which, unlike the first embodiment, the investment area 20 for the first cover layer 10 not included, but otherwise as in the first embodiment is formed. The connection area 21 to the first topcoat 10 goes steplessly into a cylindrical distance range 22 as well as in a cylindrical connection area 24 to the second cover layer 14 above. The connection area 24 to the second cover layer 14 protrudes over the outer surface of the second cover layer 14 in the measure of the local adhesive layer 5 in addition, leaving the holding element 4 at the same time on the corresponding contact surface 26 of the insert element 2 as well as on the adhesive layer 5 can be placed.

Also in this case, a force introduction element 2 . 4 as well as a sandwich structure 1 be created, which the exchange of forces between the force application element 2 . 4 and the sandwich structure 1 can allow without the sandwich structure 1 this burdened, pressed and thus damaged. Also can over the adhesive layers 5 a secure hold of the insert element 2 opposite the two cover layers 10 . 14 be achieved. Furthermore, by varying the distance between the plant area 20 for the first cover layer 10 and the contact surface 26 of the insert element 2 the thickness of the adhesive layers 5 with deformed flanged edge 27 be set defined and reproducible.

LIST OF REFERENCE NUMBERS

A-A

first cross-section

B-B

second cross section

R

radial direction

X

longitudinal axis

Z

vertical direction; height

1

sandwich structure

10

first (multilayer) topcoat

11

Fiber-plastic layers of the first cover layer 10

12

(Metal) insert of the first cover layer 10

13

core

14

second (multilayer) topcoat

15

Fiber-plastic layers of the second cover layer 14

16

(Metal) insert the second cover layer 14th

2

Insert element; insert; Zentralstück

20

Investment area for first cover layer 10 of the sandwich structure 1; flat bundle

21

Connecting region to the first cover layer 10

22

distance range

23

Contact surface for spacers 3; Edge or step of the distance range 22

24

Connecting region to the second cover layer 14

25

termination region

26

Contact surface for retaining element 4; Edge or step of the termination area 25

27

Fuse element; flanging

27a

Material weakening of the securing element 27; bend

28

recess; Blind hole

29

inner thread

3

Spacer; spacer

30

Through opening

31

first contact surface

32

second contact surface

4

Holding member; cover plate

40

Through opening

41

Investment area, edge or step of the holding element. 4

42

first contact surface for contact surface 26 of the insert element 2

43

second bearing surface for securing element 27 of the insert element. 2

5

adhesive layers

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 5093957A [0011]
• US 3564798A [0012]
• US 3678535 A [0013]
• US 4981735 A
• DE 102012202331 A1 [0014]
• US 4170919A [0015]
• US 2006137294 A1 [0017]

Claims (15)

A force introduction element (2, 4) for a sandwich structure (1) having a first cover layer (10), with at least one core (13) and with a second cover layer (14) along a longitudinal axis (X), with an insert element (2) the insert element (2) has a contact region (20) for the first cover layer (10), which is designed to produce a planar contact with the first cover layer (10) in the direction of the longitudinal axis (X), wherein the insert element (2) is formed in that it extends through the sandwich structure (1) from the contact area (20) for the first covering layer (10) along the longitudinal axis (X), characterized by a holding element (4) which is formed with the second covering layer (14). to produce a planar contact in the direction of the longitudinal axis (X), wherein the insert element (2) has a contact surface (26) for the holding element (4), which is formed, the holding element (4) along the longitudinal axis (X) in a predetermined n distance to the contact area (20) for the first cover layer (10) record. Force introduction element (2, 4) according to Claim 1 , characterized in that the abutment surface (26) for the retaining element (4) of the insert element (2) is designed to be flush with the second cover layer (14) along the longitudinal axis (X) so that the retaining element (4) moves in the direction of Longitudinal axis (X) in planar contact with both the contact surface (26) for the holding element (4) of the insert element (2) and with the second cover layer (14) can be accommodated. Force introduction element (2, 4) according to Claim 1 , characterized in that the abutment surface (26) for the holding element (4) of the insert element (2) is designed to terminate flush with an adhesive layer (5) of the second covering layer (14) along the longitudinal axis (X), so that the holding element (14) 4) in the direction of the longitudinal axis (X) in planar contact with both the contact surface (26) for the holding element (4) of the insert element (2) and with the adhesive layer (5) of the second cover layer (14) can be accommodated. Force introduction element (2, 4) according to one of the preceding claims, characterized in that the insert element (2) has a connection region (21) to the first cover layer (10), which is formed along the longitudinal axis (X) as far as the extend first cover layer (10), wherein the connecting region (21) to the first cover layer (10) is preferably formed non-rotationally symmetrical. Force introduction element (2, 4) according to Claim 4 , characterized in that the abutment region (20) for the first cover layer (10) is part of the connection region (21) to the first cover layer (10). Force introduction element (2, 4) according to Claim 4 or 5 , characterized in that the insert element (2) has a spacing region (22) which extends from the connection region (21) to the first cover layer (10) along the longitudinal axis (X) as far as the core (13) of the sandwich structure (1 ), wherein the distance region (22) is at least partially radially smaller than the connection region (21) to the first cover layer (10), so that the connection region (21) to the first cover layer (10) at least partially with a contact surface (23) in the distance range (22) passes. Force introduction element (2, 4) according to one of the preceding claims, characterized in that the insert element (2) has a connection region (24) to the second cover layer (14), which is formed along the longitudinal axis (X) as far as the Second cover layer (14) to extend, wherein the connecting portion (24) to the second cover layer (14) is preferably formed non-rotationally symmetrical. Force introduction element (2, 4) according to Claim 7 , characterized in that the connecting region (24) to the second cover layer (14) along the longitudinal axis (X) with the contact surface (26) for the holding element (4) closes. Force introduction element (2, 4) according to one of Claims 4 to 8th , characterized in that the connection region (21) to the first cover layer (10) is designed to hold the first cover layer (10), preferably at least one layer (11) of the first cover layer (10) in a form-fitting manner, and / or that the connection region (24) is formed to the second cover layer (14), the second cover layer (14), preferably at least one layer (15) of the second cover layer (14) to hold a form fit. Force introduction element (2, 4) according to one of the preceding claims, characterized in that the insert element (2) has at least one securing element (27) which is designed to arrange the holding element (4) on the contact surface (26) in a first state. to allow and in a second state holding the holding element (4) on the contact surface (26), wherein the securing element (27) is preferably designed as a flanged edge (27), preferably with a material weakening (27a) for defining a bending point. Force introduction element (2, 4) according to one of the preceding claims, characterized in that the abutment region (20) for the first cover layer (10) along the longitudinal axis (X) has a thickness which at least one layer (11) of the first cover layer (10 ), preferably exactly one layer (11) of the first cover layer (10), particularly preferably exactly the outermost layer (11) of the first cover layer (10) corresponds. Sandwich structure (1), with a first cover layer (10), at least one core (13), and a second cover layer (14), which are arranged along a longitudinal axis (X), and at least one force introduction element (2, 4), preferably a plurality of force introduction elements (2, 4), according to one of the preceding claims. Sandwich structure (1) after Claim 12 characterized by a spacer (3) arranged at least in sections around a spacing region (22) of the insert element (2) and extending along the longitudinal axis (X) as far as the core (13) of the sandwich structure (1), wherein the spacer (3) with a first contact surface (31) with both a contact surface (23) of the insert element (2) and with the first cover layer (10) is in surface contact, and / or wherein the spacer (3) with a second contact surface (32) with the second cover layer (14) is in surface contact. Sandwich structure (1) after Claim 12 or 13 , characterized in that the first cover layer (10) and / or the second cover layer (14) at least one layer (11, 15), preferably a fiber plastic layer (11, 15), which at least partially around the insert element (2) around an insert (12, 16), wherein the insert (12, 16) is preferably non-rotationally symmetrical. Sandwich structure (1) according to one of Claims 12 to 14 , characterized in that the abutment region (20) for the first cover layer (10) along the longitudinal axis (X) with an adhesive layer (5) on the first cover layer (10) is held, and / or that the holding element (4) along the Longitudinal axis (X) with an adhesive layer (5) on the second cover layer (14) is held.

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