Process for producing a fiber composite component with reinforced connection section for local force introduction

Abstract

Method for the local reinforcement of a fiber composite component, comprising at least the following steps: - providing a fiber layer (11) of the fiber composite component (10), - folding over a first edge region (22) of the fiber layer (11) and - placing the folded-over first edge region (22) flat onto a connecting section (31) of the fiber layer (11) to be reinforced and arranged adjacent to the edge region (22) to provide a local multi-layer structure, - connecting the folded first edge region (22) to the connecting section (31) for its reinforcement and - folding over at least one second edge region (23) of the fiber layer (11) and - placing the folded-over second edge region (23) flat on a side of the connecting section (31) facing away from the folded-over first edge region (22) or on the folded-over first edge region (22), connecting the folded-over second edge region (23) to the first edge region (22) and / or to the connecting section (31), wherein the method comprises, before the folding step, a step of dividing an end section (21) of the fiber layer (11) into the first (22) and the second edge region (23), in particular a step of dividing by means of cutting, punching or separating.

Description

The invention relates to a fiber composite component having a locally reinforced attachment section and to a method for producing the fiber composite component.Fiber composite components generally have a plastic matrix which is reinforced by means of fibers. Such components are used in particular in aviation, but also to an increased extent in the automobile industry, in order to create particularly light and nevertheless very strong components.In particular, the connection of the fiber composite components to other structures and components presents a particular challenge, since complex load states occur especially in these areas, which require a particular configuration of the fiber architecture. Thus, it is particularly important to prevent hole-bearing effects in the fiber composite component and to influence a setting behavior especially in the region of the connections, which previously have been particularly easily produced due to the fiber material.In this case, compact reinforcing or connecting components, such as struts for a wide variety of applications in a motor vehicle, which are designed as coupling elements, reinforcing components or connecting structures and are used in particularly large numbers, are of particular importance.Complex connections of this type in metal construction are usually preferred, not least in order to meet the complex requirement for functionality and operational stability. However, this choice of material has the disadvantage of a high weight. Alternatively, connections made of fiber composite materials are used, which, however, usually require a complex construction and thus a complicated and particularly expensive production in order to compensate for the material-specific aspects mentioned. In addition, the complex construction requires correspondingly complicated production processes and production plants, which in turn are cost-intensive.DE 40 19 270 A1 relates to a connecting element with eyes for receiving joints, bearings or fastening elements, wherein the eyes are formed by flow drilling, so that solid walls are produced. To increase the torsional rigidity, a reinforcing bead can also be formed in the region of the deformed tube ends.DE 100 60 379 B4 relates to a method for producing multidirectional laid filaments or laid filaments, in particular for reinforcing three-dimensional, thin-walled workpieces made of plastics or resins, wherein a number of endless filaments or laid filaments crossing one another are laid one above the other on a laying base and are subsequently connected to one another.US 3 978 191 A relates to a method of making a folded edge on each side of a flexible sheet material before the sheet material is shaped and cured in an oven to give it a solid form.It is therefore an object of the invention to provide a fiber composite component with a connection which is as simple as possible, can be produced easily and is particularly operationally resistant, and a method for producing the same.This object is achieved by means of a production method according to patent claim 1 and a fiber composite component having the features of patent claim 10.Accordingly, a method for locally reinforcing a fiber composite component is proposed, having at least the following steps:providing a fiber layer of the fiber composite component,folding over a first edge region of the fiber layer; andapplying the folded-over first edge region over a surface area to a connection section of the fiber layer to be reinforced and arranged adjacent to the edge region for providing a local multilayer structure,connecting the folded-over edge region to the connecting portion for reinforcement thereof.The fiber layer is thus folded over in the first edge region and laid on the connection section, so that a material doubling is produced, which represents a local reinforcement in this region, the connection section. Within the scope of this invention, a fiber semi-finished product, such as a woven or laid scrim, is to be understood as comprising one or more fiber layers. As is shown in detail below, this can be configured unidirectionally or multidirectionally depending on the type of semi-finished product. Fibers are understood here to mean all fibers suitable for component reinforcement, preferably carbon fibers, but also glass fibers, aramid fibers or natural fibers.The described method allows particularly simple handling and positioning of the turned-over material by means of the folding-over, since no separate semi-finished fiber product has to be provided and placed. Instead, an already present part of the fiber layer is used.According to a further embodiment, the method may further comprise the further steps:folding over at least one second edge region of the fiber layer; andapplying the folded-over second edge region over a surface of the connecting portion facing away from the folded-over first edge region or onto the folded-over first edge region,connecting the folded-over second edge region to the first edge region and / or to the connecting portion.The second edge region is therefore likewise folded over after the first edge region in order to additionally produce a further reinforcement of the connection section by a third layer of the fiber layer. The folding over of the second edge region can be effected either by folding over onto the same side as the first edge region, such that both edge regions are placed flat one on top of the other, or alternatively by folding over in the opposite direction with respect to the first edge region, in order to arrange this on the opposite side of the fiber layer.Of course, more than two edge regions can be defined, in particular a third and / or fourth edge region, which are placed one on top of the other and connected to one another in an analogous manner in order to reinforce the connection section with correspondingly additional layers in a multilayer manner.The method can also comprise, before the folding step, a step of dividing an end section of the fiber layer into at least the first and the second edge region, in particular a step of dividing by means of cutting, punching or separating.The end section of the fiber layer is thus separated into the first and second edge regions (or more) for example by means of the aforementioned methods, so that the edge regions can be folded over independently of one another. For example, it is possible to perform the step of separating by means of a hot tool. This is advantageous in particular when the fiber layer is already surrounded by a thermoplastic matrix and this has to be severed together with the fiber layer. More detailed explanations in this respect are described below.Furthermore, the fiber layer may be a unidirectional fiber layer, wherein the dividing step comprises dividing the end portion along the fiber orientation. Preferably, fibers of the unidirectional fiber layer can be oriented along a longitudinal extension of the fiber layer.Unidirectional fibers are particularly suitable for components which are subjected to a tensile stress during their intended use and are thus optimized along the load path and the load direction. This makes it possible to dispense with unnecessary fiber orientations and thus additionally reduce the material outlay and the weight.According to a further embodiment, the folding step comprises folding the first edge region around a first folding edge and / or the second edge region around a second folding edge, wherein the first or second folding edge is oriented such that a fiber orientation of the first or second folded edge region encloses a first angle or a second angle with the fiber orientation of the fiber layer in the connection section. If more than two edge regions are provided, a respective folding over takes place in an analogous manner.This means that a fiber orientation of the folded-over first or second edge region is oriented rotated by the first or second angle to the fiber orientation of the fiber layer. This can be achieved, for example, in such a way that the respective folded edge is oriented at an angle to the fiber orientation of the fiber layer. If, in the case of a unidirectional fiber layer, the angle is preferably chosen to be not equal to 0° or + / -90° with respect to the fiber orientation of the fiber layer, the fiber orientation of the respective edge region is not oriented parallel to the fiber orientation of the fiber layer, so that a particularly advantageous reinforcing effect results due to the different angular positions of the layers lying one on top of the other. An angle of substantially + / - 45° is preferably proposed in order to provide the most optimal possible offset of the angular positions with respect to one another.Of course, a fiber layer having multidirectional fiber orientation may also be used. However, in this case, separating the end section into at least the first and second edge regions requires severing of individual fibers which cross the separating line.According to a preferred embodiment, the fiber composite component comprises a thermoplastic matrix into which the fiber layer is integrated, with the further step:at least local heating of the thermoplastic matrix for folding over the first and / or second edge region.Accordingly, starting from the fiber composite component with thermoplastic matrix and fiber layer integrated therein, the steps of the method are carried out. For this purpose, the thermoplastic matrix is first heated in order to achieve sufficient flexibility of the matrix for folding over the fiber layer. A prefabricated fiber composite component can thus be appropriately processed and thus the local reinforcement can be achieved.In this case, the step of connecting can also comprise a cohesive and / or a force-fit connection, in particular an at least local thermal heating and pressing. In this way, the folded-over first or second edge region is connected to the connection section or the respective other edge region and thus a quasi-isotropic layer structure is produced in the region of the connection section with minimal production effort. In particular by heating and melting the thermoplastic matrix, a cohesive connection of the thermoplastic matrix of the respective edge region to the thermoplastic matrix of the connection section or the respective other edge region can thus be achieved. The heating temperature is thus to be adjusted according to the material properties of the matrix used to ensure mutual connection. A simultaneous or subsequent pressing can additionally support the mutual connection.For example, a fiber composite component can be produced by extrusion or pultrusion as an extruded profile with an integrated fiber layer. After cutting to the desired length, at least one connection section can be reinforced according to the described method. In this way, corresponding fiber composite components can be produced in a particularly advantageous and simple manner and can be locally reinforced.As an alternative to the prefabricated fiber composite component with a thermoplastic matrix and the already integrated fiber layer, it is also possible to prepare first only the fiber layer accordingly in the dry, i.e. in the non-impregnated, state by the method described. In other words, the edge region or regions is folded over in the dry state. Only after the completed preparation of the fiber layer is the integration thereof into the fiber composite component effected by impregnation of the fiber layer.For example, the step of connecting in this case can comprise sewing the respectively folded over first and second edge region and subsequently impregnating the fiber layer with a matrix for producing the fiber composite component. In this case, both a thermoplastic and a thermosetting matrix can be used as the matrix. Of course, other known means for bonding the textile, non-impregnated fibre layer may also be provided.In each of the described cases, the method can comprise a post-processing step, in particular an introduction of recesses or bores into the connection section. Depending on the type and manner of the intended connection to other components, the post-processing step can comprise a deviating post-processing or an attachment of additional connection elements.It is also possible that the method comprises an additional step of wrapping the locally reinforced fiber layer at least in the area of the connection section. In this way, it is possible, following the reinforcement of the connection section, to provide an additional reinforcement by folding over at least one edge region by wrapping once or several times. The winding can be carried out either in the dry state of the fiber layer before the subsequent impregnation. Alternatively, in the case of a fiber layer already impregnated with a thermoplastic matrix, the winding can be carried out as part of a post-processing. In this case, it is to be ensured that the thermoplastic matrix experiences a corresponding heating in order to enable a cohesive connection of the matrix, for example by fusion.The method described enables a low material usage and particularly high cost efficiency with simultaneously low machine complexity. In addition, it contributes to increased cycle times and thus to a high number of achievable production numbers per unit time.Furthermore, a fiber composite component with a locally reinforced connection section is provided, wherein the fiber composite component comprises an integrated fiber layer, and the fiber layer is formed in multiple layers in the region of the connection section by at least one folded-over edge region of the fiber layer.According to a further embodiment, the fiber composite component is a component extending in a longitudinal direction, in particular an extruded flat profile, a strut, a coupling element, a stiffening element, wherein the connection section is arranged at one end of the fiber composite component. A coupling element is to be understood as a coupling rod, for example.Furthermore, the fiber layer can have a unidirectional fiber orientation and the at least one edge section can be folded over in such a way that its fiber orientation encloses an angle with the fiber orientation of the fiber layer. For example, the unidirectional fiber orientation is aligned substantially in the longitudinal direction of the fiber composite component.The invention is explained below on the basis of an exemplary embodiment with reference to the figures. FIGS. 1 to 5 show intermediate steps of a method for locally reinforcing a fiber composite component in a schematic illustration.FIG. 1 shows a fiber layer 11 for a fiber composite component as the starting element. The fiber layer 11 can either be designed as a "dry", i.e. non-impregnated fiber layer, or integrated in a finished fiber composite component 10 (embodiment shown in dashed lines), which comprises a fiber layer impregnated with a thermoplastic matrix. This finished fiber composite component 10 can be produced, for example, by means of an extrusion method.Within the scope of this invention, a fiber semi-finished product, such as a woven or laid scrim, is to be understood as comprising one or more fiber layers. As will be shown in detail below, these can be configured unidirectionally or multidirectionally depending on the type of semi-finished product. Fibers are understood to be all fibers suitable for component reinforcement, in particular carbon fibers, glass fibers, aramid fibers or natural fibers.In the embodiment shown, the fiber layer is designed as a unidirectional fiber layer, the fibers F of which are oriented along a longitudinal extension L of the fiber layer.FIG. 2 shows a subsequent step of the central division of a first end section 21 of the fiber layer 11 into a first 22 and a second edge region 23. In this case, the unidirectionally embodied fiber layer 11 is separated by section S along the fiber orientation (in this case, this is equal to the longitudinal extension L).Subsequently, the first edge region 22 of the fiber layer 11 is folded over about a first folded edge 27 and the second edge region 23 is folded over about a second folded edge 28. In this case, the first 27 or second folded edge 28 are oriented such that the fiber orientation of the first 22 or of the second folded edge region 23 encloses a first angle α 1 or a second angle α 2 (cf. FIG. 3 ) with the fiber orientation of the fiber layer 11 in the connection section 31, as is illustrated in detail below.For the second end section 24 with the connection section 32, the edge areas 25 and 26 and the folded edges 29 and 30, an analogous procedure can be provided. For the sake of simplicity, however, the following FIGS. 3 to 5 only take into account a reinforcement of the first connection section 31; of course, the explanations for the second connection section 32 apply analogously if necessary.FIG. 3 shows the first connection section 31 after folding over the first edge region 22 and placing it flat on the connection section 31 of the fiber layer 11 to be reinforced and arranged adjacent to the first edge region 22 in order to provide a multilayer structure local in this section. This consists of the fiber layer 11 in the connection section 31 and the edge region 22 which is laid flat and which is likewise part of the fiber layer 11 and thus enables a locally doubled layer structure.Furthermore, the folding over of a second edge region 23 of the fiber layer 11 and a flat placement of the folded over second edge region 23 takes place, depending on the folding-over direction, either on a side of the connection portion 31 facing away from the folded over first edge region 22 or on the first edge region 22 already folded over previously.In addition, the folded-over first edge region 22 and the second edge region 23 are mutually connected to the connection portion 31.In the embodiment shown, the first folded edge 27 and the second folded edge 28 form a respective angle of approximately β1=-45° and β2=+45° with the fiber orientation of the fiber layer in the attachment section. Due to the unidirectional fiber orientation, a fiber orientation of the first or second edge region rotated by the angles α 1 and α 2 is thus obtained with respect to the fiber orientation of the connection section. In this way, a multilayer layer structure is produced, wherein each of the layers has its own angular position, so that particularly effective local reinforcement of the connection section 31 takes place in a particularly simple manner.FIG. 4 shows an optional additional step of wrapping the reinforced connection portion 31. unidirectional fiber material 41 is applied for this purpose essentially transversely (e.g. α3=90°) to the fiber orientation of the fiber layer, whereby the connection portion 31 experiences an additional reinforcement. The additional fiber material can already be impregnated and bonded to the matrix of the fiber composite part in a materially bonded and / or force-locked manner. Alternatively, a non-impregnated fiber material is possible, which is only subsequently impregnated.FIG. 5 shows a likewise optional post-processing step for introducing a recess 51 or bore into the reinforced connection section 31; of course, instead of a bore, recesses of different shapes or other post-processing steps can be carried out.

Claims

Method for locally reinforcing a fibre composite component, having at least the following steps: - providing a fibre layer (11) of the fibre composite component (10), - folding over a first edge region (22) of the fibre layer (11) and - covering the folded over first edge region (22) over a surface area on a connection section (31) of the fibre layer (11) to be reinforced and arranged adjacent to the edge region (22), in order to provide a local multilayer structure, - connecting the folded over first edge region (22) to the connection section (31) for reinforcing it, and - folding over at least one second edge region (23) of the fibre layer (11) and - covering the folded over second edge region (23) over a surface area on a side of the connection section (31) facing away from the folded over first edge region (22) or on the folded over first edge region (22), Connecting the folded-over second edge region (23) to the first edge region (22) and / or to the connection portion (31), wherein the method comprises, before the folding-over step, a step of dividing an end portion (21) of the fibre layer (11) into the first (22) and the second edge region (23), in particular a step of dividing by means of cutting, punching or separating.The method of claim 1, wherein the fiber layer (11) is a unidirectional fiber layer and the dividing step comprises dividing the end portion (21) along the fiber orientation.Method according to claim 2, wherein fibers (F) of the unidirectional fiber layer are oriented along a longitudinal extension (L) of the fiber layer (11).Method according to one of Claims 1 to 3, wherein the folding step comprises folding over the first edge region (22) about a first folding edge (27) and / or the second edge region (23) about a second folding edge (28), wherein the first (27) or second folding edge (28) is oriented such that a fibre orientation of the first (22) or the second folded edge region (23) encloses a first angle (α1) or a second angle (α2) with the fibre orientation of the fibre layer (11) in the connection section (31).Method according to one of Claims 1 to 4, wherein the fiber composite component (10) comprises a thermoplastic matrix into which the fiber layer (11) is integrated, with the further step: - at least local heating of the thermoplastic matrix in order to fold over the first (22) and / or second edge region (23).Method according to claim 5, wherein the step of connecting comprises a cohesive and / or a force-fit connection, in particular an at least local thermal heating and pressing.Method according to one of Claims 1 to 4, wherein the step of connecting comprises sewing the respectively folded-over first (22) or second edge region (23) and a subsequent impregnation of the fiber layer (11) with a matrix for producing the fiber composite component (10).Method according to one of Claims 1 to 7, wherein the method comprises a post-processing step, in particular an introduction of recesses (51) or bores into the connection section (31).Method according to any one of claims 1 to 8, wherein the method comprises an additional step of wrapping the locally reinforced fibre layer (10) at least in the region of the attachment portion (31).Fibre composite component with a locally reinforced connection section, wherein the fibre composite component (10) comprises an integrated fibre layer (11), characterised in that the fibre layer (11) is formed in multiple layers in the region of the connection section (31) by at least two folded-over edge regions (22, 23) of the fibre layer (11).Fiber composite component according to claim 10, characterised in that the fiber composite component (10) is a component extending in a longitudinal direction (L), in particular an extruded flat profile, a strut, a coupling element, a stiffening element, wherein the connection section (31) is arranged at one end of the fiber composite component (10).Fiber composite component according to claim 10 or 11, characterised in that the fiber layer (11) has a unidirectional fiber orientation, in particular a fiber orientation aligned substantially in the longitudinal direction (L) of the fiber composite component (10), and the at least one edge section (22, 23) is folded over in such a way that its fiber orientation encloses an angle (α1, α2) with the fiber orientation of the fiber layer (11).

Images