Method for machining and assembling an FRP component, method for manufacturing an FRP component and corresponding tool

Abstract

Method for processing and assembling a fiber-plastic composite component (1, 1'), the method comprising the following steps: a provision step in which the fiber-plastic composite component (1, 1') is provided; a machining step in which a surface section (11, 11') of the component (1, 1'), which is pressed against a mounting surface of another body (2, 2') during intended assembly of the component, is machined in such a way that a roughness of the surface section (11, 11') is increased; and an assembly step in which the component (1, 1') is mounted by a screw or rivet acting immediately and directly on a plastic matrix of the component in such a way that the surface section (11, 11') is pressed by the screw or rivet onto a mounting surface of another body (2, 2').

Description

The invention relates to a method for producing a fiber-plastic composite component.Fiber-plastic composite components (hereinafter LCV components) are generally known in the prior art and are increasingly used in the automobile industry for realizing lightweight constructions.If during assembly it is provided that such LCV components are mounted by a screw connection, structural measures are necessary in order to ensure a permanently reliable screw connection. The reason for this is that the fiber-plastic composite has a strong creep behavior, as a result of which the screw connection can lose its prestressing force, so-called setting.In order that the above-mentioned creep behavior of the fiber-plastic composite does not lead to any loosening or loosening of the screw connection, metal bushes for example are glued into the LCV component at locations intended for the assembly in the prior art.The principle of such a bonded-in metal bushing is that the prestressing force of the screw connection acts on the metal bushing and the force transmission to the LCV component is taken over by the adhesive that secures the bushing.However, the use and bonding of the explained metal bushes leads to an undesired additional weight of the LCV component and to an increase in the necessary production or assembly steps. For example, the surface of the LCV component has to be cleaned before the bonding of the metal bushing, then the adhesive has to be applied and the latter has to be maintained until it cures.In addition, in the case of a faulty adhesive connection, rigidity losses can occur, which lead to stability problems.DE 10 2011 055 625 A1 discloses a motor vehicle axle having a transverse leaf spring, at least one link and a pendulum support connecting the transverse leaf spring and the link. The pendulum support is mounted exclusively in a form-fitting manner between the link and the transverse leaf spring, wherein the pendulum support is fixed exclusively in a form-fitting manner to the transverse leaf spring. For this purpose, the transverse leaf spring has a receiving surface which in turn has a contour. Furthermore, a method for producing a corresponding transverse leaf spring is disclosed.Further prior art is formed by WO 2014 / 184 418 A1, DD 2 43 672 A1 and EP 2 103 416 A2.Against this background, it is an object of the present invention to provide a method for processing and mounting an LCV component which enables easy and simple mounting of the LCV component by means of a clamping connection.This object is achieved by a method according to claim 1. Preferred embodiments are the subject matter of the dependent claims. The invention is defined by the claims, aspects of the invention being set forth below.According to an aspect of the invention, a method for processing and assembling a fiber-plastic composite component as defined in claim 1 comprises a providing step in which the fiber-plastic composite component is provided, a processing step in which a surface portion of the component is processed in such a way that a roughness of the surface portion is increased, and an assembly step in which the component is assembled by a clamping element (screw or rivet) acting directly and directly on a plastic matrix of the component in such a way that the surface portion is pressed by the clamping element preferably directly against an assembly surface of another body.The surface section of the component processed in the processing step is in particular a surface section which is pressed as intended by a screw or a rivet provided with or without a washer to form a clamping connection to the mounting surface of the involved / other body. For example, the surface section is one at which a through opening provided for a screw or rivet connection is formed at the latest in the assembly step. The through hole may be formed in, for example, the providing step or the processing step or the assembling step.The method according to the invention is preferably used / carried out for machining a motor vehicle component.In the method according to the invention, the roughness of the surface section is increased in particular in such a way that the (adhesion) coefficient of adhesion which results for the processed surface section of the LCV component and the mounting surface of the other body is greater than a (adhesion) coefficient of adhesion which results for the corresponding unprocessed surface section and the mounting surface of the other body. This results in the frictional force or static friction being greater at a specific contact pressure acting on the surface section, which is generated by the screw or the rivet provided with or without a washer, compared to the case in which the surface section of the component is unprocessed.By means of the machining and assembly method according to the invention, the component can be assembled in the assembly step by a direct clamping, i.e. by direct setting of a rivet or by a direct screw connection, without using additional elements integrated into the component (on which the rivet or the screw provided with or without a washer acts), such as metal bushes, because, due to the higher roughness or a resulting higher coefficient of friction, a release of the clamping is counteracted by the creep behavior of the FCV component. In other words, the loss of prestressing force or contact force occurring during the service life of the component as a result of its creep behavior can be compensated for by increasing the roughness of the surface section.The method according to the invention in particular leads to the component being produced more cost-effectively and the assembly being able to be carried out more easily, cost-effectively and more quickly.In addition, the weight of the LCV component and the required installation space are not increased by additional elements, such as bushings.Furthermore, roughening the surface section is an easily controllable method step.In addition, when a static friction necessary for a specific application is specified, the necessary contact pressure generated by the clamping element can be reduced by increasing the roughness or the coefficient of friction. A reduced contact pressure has a positive effect on the creep behavior of the LCV component. Smaller clamping elements / screws / rivets could also be used under certain circumstances.The LCV component provided in the provision step can be, for example, an already finished LCV component obtained from a manufacturer.The plastic matrix material forming the matrix of the LCV component can be, for example, a thermosetting plastic or else a thermoplastic.Depending on the intended use of the component, various types of reinforcing fibers can be used, for example inorganic reinforcing fibers (basalt, boron, glass, ceramic and silica fibers), metallic reinforcing fibers (steel, aluminum, copper, generally metal and metal alloy fibers), organic reinforcing fibers (aramid, carbon, polyester, nylon, polyethylene and plexiglass fibers) and natural fibers (wood and flax fibers).In the CFV component, the embedded reinforcing fibers may be present in different lengths, whereby different stiffness and strength properties can be achieved. When using continuous fibers, i.e. reinforcing fibers which pass completely through the LCV component, the highest rigidity or strength values are achieved.The aforementioned reinforcing fibers can have different structures within the component. The continuous fibers can, for example, be woven to form fabrics or be present in the form of laids in which the continuous fibers are arranged in parallel. Other types of reinforcing fiber structures are, for example, knits, braids, mats and nonwovens.In the processing step of the method according to the invention, the roughness of the surface section is preferably increased by producing a defined surface structure on the surface section.The defined surface structure can be, for example, a surface pattern with regular or irregular concave / convex sections. Exemplary shapes are regularly / irregularly arranged pyramids and / or cones and / or truncated cones.Preferably, in the provision step, a fiber-plastic composite component is provided, in which an additional fabric element is embedded in a plastic matrix of the component at the surface section. The surface section is processed by removing the additional fabric element, for example by tearing it off. The embedded additional fabric element allows the surface section to be machined at a desired time. Complicated cleaning of the surface section and necessary protective measures for protecting the cleaned surface section can consequently be avoided by removing the additional fabric element only if required.Such an additional fabric element can be, for example, a nylon fabric which is embedded in the plastic matrix of the component during its production.The additional fabric element or the nylon fabric can be removed, for example, by tearing it off. The additional fabric element is preferably only torn off shortly before the assembly step, whereby a clean surface section provided for assembly is formed.If an already finished shaped LCV component is provided in the provision step, it is preferred that the manufacturer of the LCV component embeds the additional fabric element in the plastic matrix at processed surface sections. The assembler can then remove the corresponding additional fabric elements immediately before the assembly step of the component.Alternatively, a production step, for example a resin transfer molding (RTM) or wet pressing method, is preferably carried out before the provision step, in which reinforcing fibers are embedded in a plastic matrix, wherein an additional fabric element is also embedded in the plastic matrix at the surface section. The surface section is subsequently processed by removing the additional fabric element, for example by tearing it off.The through-opening for the screw or the rivet can also be formed, for example, in the production step.Preferably, in the provision step, a fiber-plastic composite component is provided, in which reinforcing fibers are embedded in a thermoplastic matrix. Subsequently, in the processing step, the component is processed on the surface portion by heating the surface portion and pressing a punch on the surface portion.Alternatively, in the processing step, the component is processed on the surface portion by pressing a heated punch onto the surface portion.By heating the surface section and then pressing on the punch or using a heated punch, a necessary (defined) surface structure can be produced very easily and quickly on the surface section.According to a further aspect of the invention, a method for producing a fiber-plastic composite component comprises embedding reinforcing fibers in a plastic matrix and forming the component, wherein the reinforcing fibers are embedded in the plastic matrix in such a way that a roughness of a surface section of the component, which is pressed onto a mounting surface of another body by a clamping element, which preferably acts directly on the component or the plastic matrix of the component, when the component is mounted as intended, is increased compared to a roughness of a surface of the component surrounding the surface section.This production method according to the invention ensures a required roughness of the surface section of the component directly during production.The through hole for the washer-equipped screw or rivet may be formed at the surface portion in the manufacturing process or thereafter.In the production method, the embedding and forming of the component is preferably realized by a resin transfer molding method or a wet pressing method in which the increased roughness of the surface section is achieved.In the RTM process, the reinforcing fibers are introduced dry into a tool intended for production. The tool is then preferably closed pressure-tightly and the plastic matrix material is pumped into the tool in a controlled manner.In the wet pressing method, on the other hand, pre-impregnated reinforcing fibers, for example a woven fabric or laid scrim, are placed into the tool and the component is subsequently shaped by pressing. The superfluous plastic matrix material escapes at the edge of the tool.After curing of the plastic matrix material, the components can be removed from the tool.The manufacturing method can be performed by the tool explained below.The tool has tool molds which, in a closed state, define a cavity which fixes the shape of the component and into which reinforcing fibers and a plastic matrix material can be introduced for forming the component, and which can be opened again for removing the component.The tool molds are designed in such a way that a roughness of a surface section of the component removed from the cavity, which is pressed onto a mounting surface of another body by a clamping element preferably acting directly on the component or the plastic matrix of the component during the intended mounting of the component, is increased compared to a roughness of a surface of the component surrounding the surface section.That is to say, elements which provide for the roughness of the surface section are integrated directly into the tool.Preferred variants of the machining method according to the invention are explained below with reference to the attached drawings. FIG. 1 schematically shows a first variant of the method according to the invention, in which a tempered / heated stamp is pressed onto a thermoplastic matrix of the LCV component to form a defined surface structure. FIG. 2 shows a second variant of the method according to the invention, in which a tear-off fabric is embedded in the plastic matrix during the production of the LCV component and torn off before the assembly in order to form a specific surface roughness.FIG. 1 shows a first variant of the processing method according to the invention, in which an LCV component 1 with a thermoplastic matrix is provided in a first provision step. The LCV component 1 can have been obtained, for example, from a manufacturer.Subsequently, a surface section 11 of the LCV component 1 is machined in a machining step.The LCV component 1 is designed such that it is mounted as intended in an assembly step by a screw connection or a rivet connection provided with or without washers. In this case, it is provided that the surface section 11 of the LCV component 1 is pressed against a mounting surface 21 of another body 2 by the screw or rivet connection and the LCV component 1 is thereby clamped in place.In order to increase the reliability of the clamping connection formed, according to the invention, the surface section 11 of the component 1 is machined in the machining step in such a way that the roughness of the surface section 11 is increased. This is achieved by a tempered / heated punch 3.The tempered / heated stamp 3 is heated to a specific temperature, which depends on the melting temperature of the thermoplastic matrix used of the LCV component 1. When the punch 3 has reached the desired temperature, it is pressed with a force F p onto the surface section 11 of the component 1, whereby the thermoplastic matrix melts at the surface section 11 and a surface structure corresponding to the punch 3 is formed on the surface section 11.If the component 1 is subsequently mounted in the shown mounting step by the surface section 11 being pressed against the mounting surface 21 of the other body 2 involved, the frictional force or static friction between the component 1 and the other body 2 is greater due to the increase in the corresponding (adhesion) coefficient of friction, compared to the case in which the same component 1 is pressed against the other body 2 without the surface section 11 being processed.FIG. 2 shows a second variant of the method according to the invention.In this second variant, an LCV component 1' is provided in the provision step, in which a tear-off fabric (not shown), for example a nylon fabric, was embedded into the plastic matrix during the production of the LCV component 1'.In this method variant, a component 1' can be provided in the provision step, which component has either a thermosetting or thermoplastic matrix.In order to increase the roughness of the surface section 11' of the component 1', which is pressed against a mounting surface 21' of another body 2' during the intended mounting, the user removes the tear-off fabric by removing it by, for example, a jerk-like tearing-off.At the surface portion 11', a defined surface structure remains depending on the structuring of the tear-off fabric.When the component 1' is subsequently assembled in the assembling step by pressing the surface portion 11' against the assembly surface 2%0020́ of the other involved body 2', the frictional force between the component 1' and the other body 2' is larger due to the increase of the corresponding (adhesion) coefficient of friction as compared with the case where the same component 1' is pressed against the other body 2' without the processed surface portion 11'.

Claims

Method for processing and mounting a fiber-plastic composite component (1, 1'), wherein the method comprises the following steps: a providing step in which the fiber-plastic composite component (1, 1') is provided; a processing step in which a surface section (11, 11') of the component (1, 1'), which is pressed against a mounting surface of another body (2, 2') when the component is mounted as intended, is processed in such a way that a roughness of the surface section (11, 11') is increased; and an assembly step in which the component (1, 1') is mounted by a screw or a rivet acting directly and directly on a plastic matrix of the component in such a way that the surface section (11, 11') is pressed by the screw or the rivet against an assembly surface of another body (2, 2').Method according to claim 1, wherein in the processing step the roughness of the surface section (11, 11') is increased by producing a defined surface structure on the surface section (11, 11').Method according to claim 1 or 2, wherein in the providing step a fiber-plastic composite component (1, 1') is provided, in which an additional fabric element is embedded in a plastic matrix of the component (1, 1') at the surface section (11'); and in the processing step the surface section (11') is processed by removing the additional fabric element.Method according to claim 1, 2 or 3, wherein before the providing step a manufacturing step, in particular a resin transfer molding (RTM) or wet pressing method, is carried out, in which reinforcing fibers are embedded in a plastic matrix, wherein an additional fabric element is embedded in the plastic matrix at the surface portion; and in the processing step the surface portion (11') is processed by removing the additional fabric element.The method according to claim 3 or 4, wherein in the processing step the surface portion (11') is processed by tearing off the additional fabric element.The method according to claim 1 or 2, wherein in the providing step a fiber-plastic composite component (1) is provided in which reinforcing fibers are embedded in a thermoplastic matrix, and in the processing step the component (1) is processed at the surface portion by heating the surface portion (11) and pressing a punch (3) onto the surface portion (11).The method according to claim 1 or 2, wherein in the providing step a fiber-plastic composite component (1) is provided in which reinforcing fibers are embedded in a thermoplastic matrix, and in the processing step the component (1) is processed at the surface portion (11) by pressing a heated punch (3) onto the surface portion (11).

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