Device for edge sealing within at least one opening that has been formed in a component made of fiber composite material as a result of a separation process

Abstract

Device for edge sealing within at least one opening which has been formed in a component (1) made of fiber composite material as a result of a separation process, with a mandrel (5) that can be passed through the respective opening and a sealing element (2) on one end face that rests against a surface of the component (1) when the mandrel (5) is inserted into the opening; and a counter-support (4) which is connected or connectable to the mandrel rests on the opposite surface of the component (1) when the mandrel (5) is inserted into the opening; wherein the outer surface of the mandrel (5) or the outer surface of the counterholder (4) which is inserted into the opening, has a contour and cross-sectional dimension that corresponds to the complementary contour of the sealed opening to be formed at the edges (6) of the respective opening; wherein within the opening, a cavity (3) arranged inside the opening is enclosed by the sealing element (2) on one surface, by the counterholder (4) on the other surface of the component (1) and the outer surface of the mandrel (5) or the outer surface of the counterholder (4) arranged inside the opening and the edge (6) formed by the separation. the cavity (3) can be filled through the interior of the mandrel (5) with a polymeric resin (8) that can be cured as a result of a subsequent energy input; and the pin (5) can be removed from the opening after or during the hardening of the resin (8) and the mandrel (5) can be guided through the respective opening from one side of the component (1) until an elastically deformable sealing element (2) formed from an elastomeric polymer and attached to the front end face of the mandrel (5) in the insertion direction is arranged above the surface of the component (1) and the counterholder (4) rests against the opposite surface of the component (1), wherein with a mechanism the mandrel (5) is movable in the opposite direction after insertion into the opening and arrangement of the sealing element (2) on the corresponding surface of the component (1), so that the end face on which the sealing element (2) is arranged moves in the direction of the surface of the component (1) on which the counterholder (4) touches the component (1), and thereby the sealing element (2) is elastically deformed so that the area with which the sealing element (2) is in contact with the corresponding surface of the component (1) is increased.

Description

[0001] The invention relates to a device for edge sealing within at least one opening which has been formed as a result of a separation process in a component made of fibre composite material.

[0002] Components made of fiber-reinforced plastic composites, thanks to their lightweight construction properties, offer the potential to meet the ever-increasing demands for cost and energy efficiency in mechanical components. However, their separation poses several challenges, both process-related and material-related. In all processes, but especially laser cutting, edge formation leads to exposed fiber ends. Laser cutting is a thermal process. The components of the inhomogeneous fiber-reinforced plastic composites exhibit different characteristic temperatures at which separation can be achieved. The reinforcing fibers have significantly higher melting, sublimation, and decomposition temperatures than the polymer matrix materials in which the reinforcing fibers are embedded.Through thermal conduction effects, thermal energy is transferred from the cutting edge into the fiber composite material. This leads to local thermal decomposition of the polymer matrix surrounding the fibers at the cutting edge and the formation of the so-called heat-affected zone. Depending on the process, material, and cutting parameters, its extent can range from approximately 100 µm to 1 mm.

[0003] Polymers generally tend to absorb water, which impairs their mechanical properties and can lead to delamination. Laser cutting and the inhomogeneous material structure of fiber-reinforced plastic composites result in an irregular polymer edge located behind the edge of the reinforcing fiber ends. This edge has an enlarged surface area. The closely spaced, open ends of the reinforcing fibers also create capillaries, which, under humid or wet environmental conditions, allow liquids, especially water, to accumulate at this edge formed by the thermal separation. These conditions can accelerate liquid or water absorption and should therefore be avoided.

[0004] Carbon fiber-reinforced plastic composites also pose a corrosion problem without appropriate countermeasures. In conjunction with metallic joining partners, galvanic corrosion occurs in the presence of an electrolyte. Aluminum, also an excellent lightweight material, is particularly critical in this regard. The open carbon fiber ends and the metal enter into an electrochemical reaction. Both problems require the sealing of the edges of fiber-reinforced composite components. Polymers are generally electrical insulators and are therefore immune to galvanic corrosion. They are suitable for electrically separating the reactants from each other.

[0005] Holes are frequently recurring geometric elements in joining technology and are predestined for contact between different joining partners.

[0006] Until now, the edges were sealed manually using thermosetting resin systems. However, this procedure is not suitable for large-scale production. It is time-consuming, and consistent and complete edge coverage cannot be guaranteed, which results in significant quality assurance efforts, especially in automotive and especially aircraft construction.

[0007] DE 10 2009 060 692 A1 describes a method for sealing thermoplastic and thermosetting fiber-reinforced plastic components, at least in sections, along at least one component edge. A smooth edge surface is created by electrostatically coating the component with thermoplastic polymer powder, followed by melting and crosslinking the powder with the polymer matrix of the fiber composite. A disadvantage of this method is that the entire component experiences a temperature increase during melting of the polymer powder. If the component has a thermoplastic polymer matrix, a polymer with a melting temperature significantly lower than that of the matrix material must be selected for edge sealing. Otherwise, the polymer forming the matrix of the component material will melt and be destroyed. Furthermore, edge sealing occurs in two process steps, increasing the complexity of automation.The complete heating of the component to melt the edge coating is also disadvantageous for the process time.

[0008] DE 10 2014 214 031 A1 describes a process in which a thermoplastic semi-finished product is placed on the cut edge of a fiber-reinforced plastic composite component. It is then joined to the fiber-reinforced component either thermoplastically or by ultrasonic welding. However, this process appears disadvantageous for sealing the edges of holes, since accessibility to the strip deposition device and the welding head must be ensured for smaller holes.

[0009] DE 694 03 375 T2 describes a process and device for resin transfer molding (RTM) for manufacturing components from fiber-reinforced plastic composites. In this process, a fiber reinforcement is placed in a mold cavity, surrounded by liquid resin, and then cured. The RTM process requires the use of a catalyzed resin, which is preheated using microwaves to reduce its viscosity before injection into the mold.

[0010] US 3,564,898 A describes a fastening element which is to be fastened to a component formed by two plates.

[0011] DE 10 2008 025 955 B3 concerns an electrical water vapor diffusion-tight connector.

[0012] From DE 10 2008 024 689 A1 a fastening sleeve for anchoring a screw is known.

[0013] A method for producing a component from an organic sheet is disclosed in DE 10 2010 001 634 A1.

[0014] The object of the invention is therefore to provide possibilities for a reliable, simplified sealing of the edges of perforations formed as a result of a separation process, in particular a thermal separation process. The sealing should also be capable of being carried out automatically and should prevent the penetration of liquid into the fiber composite material as well as counteract corrosion.

[0015] According to the invention, this object is achieved with a device having the features of claim 1. Advantageous embodiments and further developments of the invention can be realized with features defined in subordinate claims.

[0016] The device is provided with a mandrel that can be passed through the respective opening, and with a sealing element on one end face that rests against a surface of the component when the mandrel is inserted into the opening. A counterholder rests against the opposite surface of the component, which is connected or connectable to the mandrel when the mandrel has been inserted into the opening. The outer surface of the mandrel or the outer surface of the counterholder, which is inserted into the opening, has a contour and cross-sectional dimension that corresponds to the complementary contour of the sealed opening at the edges of the respective opening.

[0017] Within the opening, a cavity arranged inside the opening is enclosed by the two surfaces, once with the sealing element on one surface, with the counterholder on the other opposite surface of the component and the outer surface of the mandrel or the outer surface of the counterholder arranged within the opening and the edge formed by the separation.

[0018] The cavity can be filled with a polymer resin through the mandrel, which cures upon subsequent energy input. The mandrel can be removed from the opening after or during the resin curing.

[0019] The mandrel or a counterholder can have an outer surface, at least in the area passing through the opening, that has a circular or polygonal shape. Thus, a corresponding fastener, such as a screw or rivet with a circular outer surface, or a square profile with a square outer surface, can be inserted into the opening, which is sealed on the surface with the resin.

[0020] To fill the cavity with resin, the mandrel should be hollow on the inside so that the resin with a suitable viscosity can be filled into the cavity through the mandrel or at least one channel formed in the mandrel via at least one, preferably several, resin outlet openings distributed radially around the circumference of the mandrel. The outlet openings and / or the resin supply system can be closable to control the resin from entering the cavity and prevent it from entering resin-free channels in the mandrel. Suitable closures can be valves or a ring around the mandrel that opens or closes the outlet openings by rotating or sliding in the axial direction.

[0021] The cavity should be filled as completely as possible. To fill it, the resin can be injected into the cavity at increased pressure.

[0022] The mandrel can be guided from one side of the component through the respective opening until an elastically deformable sealing element attached to the front end of the mandrel in the insertion direction is arranged above the surface of the component and the counterholder rests against the opposite surface of the component. For this purpose, the counterholder can be formed as a separate part on the mandrel or can be attached to the mandrel. This is advantageous if the counterholder cannot or should not be positioned and held on the corresponding surface of the component using a separate manipulator. Otherwise, the counterholder can be attached to the mandrel by means of a clamp connection, which is preferably self-locking.The connection can also be achieved force-fitting by means of a suitable fit and / or form-fitting by means of suitable surface contours on the outer surface of the mandrel and the inner surface of the opening formed in the counterholder into which the mandrel can be inserted.

[0023] In one alternative, a mechanism is used to move the mandrel in the opposite direction after it has been inserted into the opening and the sealing element has been positioned on the corresponding surface of the component, so that the end face on which the sealing element is positioned moves toward the surface of the component where the counterholder touches the component, thereby elastically deforming the sealing element. The deformation of the sealing element increases the area with which the sealing element is in contact with the corresponding surface of the component, and the cavity can thus be securely sealed at this surface, preventing any leakage of uncured resin there.

[0024] The mechanism for moving the mandrel in the opposite direction can be a screw connection between the mandrel and the counterholder, a linear drive, a pneumatic piston drive, a hydraulic piston drive or a rack and pinion drive.

[0025] It is advantageous to create a vacuum in the cavity that is lower than the ambient pressure before and / or during resin filling. This can be achieved by connecting it to a vacuum pump or compressor. The connection can also be made through the interior of the mandrel, preferably via a separate channel that opens into the cavity.

[0026] The sealing element is made of an elastomeric polymer such as silicone rubber, silicone elastomer, natural rubber or vulcanizate. A thermosetting resin, in particular epoxy resin, can preferably be used as the resin.

[0027] The device according to the invention is suitable for sealing edges at perforations in components made of fiber-reinforced composite materials with a polymeric material matrix. This is particularly necessary for laser-cut edges. However, the invention is suitable for all untreated edges on fiber-reinforced composite materials with exposed fiber ends. The respective fiber-reinforced composite material can, in particular, be continuous-fiber-reinforced or short-fiber-reinforced plastics with oriented or unoriented fiber layers and a thermoplastic or thermosetting polymer matrix. The reinforcing fibers can be made of carbon, glass, aramid, polyamide, or natural fibers, such as hemp and flax.

[0028] The device can be inserted into an opening (bore) with the assistance of a centering device, which should be integrated into the device. By actuating a mechanism from one side, the cavity formed on the side of the component on which the sealing element has been placed after insertion into the opening can be closed with the sealing element, which preferably deforms elastically in the process. The sealing element should be made of an elastomeric plastic. Silicone appears particularly suitable because it does not adhere to the polymeric, preferably thermosetting, resin used for sealing. The force required for closing should be maintained while the cavity is filled with the resin, thus maintaining the seal of the cavity during the pouring of the liquid resin used for sealing.

[0029] A negative pressure compared to the ambient pressure, especially a vacuum, should be created in the cavity. This reduced internal pressure can be used to fill the cavity with the resin and, if necessary, also the capillaries between the fiber ends. The resin can be pressurized during injection. The resin can be a thermoset that cures using energy in the form of elevated temperature, ultraviolet light, or infrared light. The resin can be single-component or multi-component. The preferred variant should be a single-component resin (eliminating the need for duplicate supply lines and a mixing device) that cures under ultraviolet light. Suitable resins are available that allow cycle times of just a few seconds. Depending on the type of resin used, the device can be equipped with a heating element or a radiation source of sufficient intensity and a corresponding wavelength to cure the resin.After the curing cycle, the device can be opened and removed from the sealed aperture.

[0030] The device enables the automated, machine-based sealing of edges at perforations in fiber-reinforced plastic components. Perforations / holes are frequently recurring features on components that can and should be used for joining with other components. A short sealing cycle time is therefore a competitive advantage.

[0031] An alternative solution for edge sealing requires only one-sided access to the hole / drilled hole. This is particularly advantageous when machining large-surface shell components, as it eliminates manual effort.

[0032] Automated edge sealing of perforations / drilled holes with short cycle times can counteract the corrosion problem in carbon fiber-reinforced plastic components. Open edges can reduce fluid and water absorption in general fiber-reinforced plastic composites, which can also reduce the resulting risk of delamination.

[0033] During the formation of the seal, a ring-shaped component or one adapted to the inner contour of an opening (unreinforced plastic, reinforced plastic, ceramic, corrosion-free metal) can be inserted into the opening / bore and adhesively bonded to the edge using the injected resin. Such a component can form a centering device. After filling with the resin, a component remaining in the opening / bore, particularly a ring, can form the edge seal together with the sealing resin. This also allows for further improvement of the edge seal and the achievement of adjustable surface properties of the opening edge (friction coefficients, fits, surface roughness, and any type of surface functionalization).

[0034] If the hole is accessible from both sides, the fixture can be designed as a type of pliers. This is possible, for example, with openings / holes located at the edges of components.

[0035] With the invention, a uniform, flat edge condition can be achieved in the openings / bores machined in this way.

[0036] The invention will be explained in more detail below by way of example. The features visible and explained in the individual figures can be combined with one another independently of the respective example or the representation in the respective figure.

[0037] Showing: Fig. 1 a perspective sectional view through an example of a device according to the invention and Fig. 2a to 2b are sectional views of an example of a device according to the invention, each in a state during edge sealing.

[0038] In the Fig. In the example of a device according to the invention shown in Figure 1, a sealing element 2 made of silicone is attached to a mandrel 5 on one end face. The mandrel 5 is guided through a bore as an opening with the other end face facing forward, so that the sealing element 2 rests against one surface of the component 1 and the contact area between the surface of the component 1 and the sealing element 2 is larger than the free cross-section of the bore as an example of an opening.

[0039] From the opposite side, a counterholder 4 is pushed onto the mandrel 5, which has a flange-like extension that is supported on the surface of the component 1 opposite the sealing element 2 and also covers the bore as an opening.

[0040] In this example, the mandrel 5 has an inner diameter that is significantly smaller than the inner diameter of the bore. Above the flange-like extension of the counter-holder 4 there is a cylindrical region which, in the position shown of the mandrel 5 and counter-holder 4, is arranged within the bore. The cylindrical region has an outer diameter that is smaller than the inner diameter of the bore as an opening, so that a cavity is formed there between the edge 6 and the outer surface of the counter-holder 4, which cavity can be filled with a resin 8 in a form not shown. After filling the cavity 3, which is sealed on the surfaces of the component 1 with the sealing element 2 and the flange-like extension of the counter-holder 4, the resin 8 can be cured by applying energy using UV radiation.

[0041] After sufficient curing of the resin 8, the counterholder 4 can be removed from one side and the mandrel 5 from the other side of the component 1 and a component 1 with edge 6 sealed with resin 8 can be obtained, as is also shown in Fig. 2d is shown.

[0042] In this example, the counterholder 4 can be made of a hard rubber material, so that the mandrel 5 and the counterholder 2 can be connected to each other in a force-fitting manner if the outer diameter of the mandrel 5 and the inner diameter 4 into which the mandrel 5 is inserted have corresponding diameters. The inner diameter of the counterholder 4 should be smaller than the outer diameter of the mandrel 5. To facilitate sliding the counterholder 4 onto the mandrel 5, a bevel can be formed on the bore through the counterholder 4 and the front face of the mandrel 5.

[0043] In the Fig. In the example shown in Figures 2a to 2d, a mandrel 5, to one end of which an elastically deformable sealing element 2 made of silicone is attached, is inserted from one side into a bore as an opening with the sealing element 2 leading. The insertion takes place in such a way that at least the larger part of the sealing element 2 protrudes beyond the opposite surface of the component 1. In addition, a counter-holder 4 fixed to the mandrel 5 touches the surface of the component 1 on the side from which the mandrel 5 has been inserted. This process is indicated by the vertically upward-pointing arrow in Figure 2. Fig. 2a. Before and during insertion into the bore, the sealing element 2 has an outer diameter that allows for easy insertion into the bore.

[0044] Subsequently, a movement of a part inside the mandrel 5 in the opposite direction, which is associated with the Fig. 2a, is illustrated by the arrow pointing vertically downwards. This results in a deformation of the sealing element 2 and the bore on this surface of the component 1 is closed, as shown in Fig. 2b can be removed. Between the outer surface of the mandrel 5, the edge 6 within the opening and the counterholder 4, there is a cavity 3 which is closed towards one surface by the sealing element 2 and on the other surface of the component 1 by the counterholder 4.

[0045] A resin 8 is poured into this cavity 3 through the interior of the mandrel 5 via an outlet opening 7. The fiber ends exposed during the cutting process and the edge 6 are sealed with the resin. The resin 8 is cured by the introduction of energy. This process is described in Fig. 2c.

[0046] Following curing, the interior of the mandrel 5 can be moved vertically upwards again, whereupon the deformation of the sealing element 2 is returned to its original state due to elasticity. As a result, the sealing element 2 has dimensions, as before and during insertion into the bore, with which the sealing element 2 can be withdrawn with the mandrel 5 from the bore provided with the resin seal 8 on the edge 6, without damaging the edge seal formed with the resin 8 in the bore. The device can therefore, as can be seen from Fig. 2d, separated from component 1 and reinserted.

[0047] In this example, too, the filling of the cavity 3 with the resin 8 can be supported by an internal pressure in the cavity 3 that is reduced compared to the ambient pressure, as has already been explained.

Claims

[1] Device for edge sealing within at least one opening formed as a result of a separation process in a component (1) made of fibre composite material, with a mandrel (5) which can be guided through the respective opening and on one end face a sealing element (2) which bears against a surface of the component (1) when the mandrel (5) is inserted into the opening; and a counterholder (4) which is connected or connectable to the mandrel rests on the opposite surface of the component (1) when the mandrel (5) is inserted into the opening; wherein the outer surface of the mandrel (5) or the outer surface of the counter-holder (4), which is introduced into the opening, has a contour and cross-sectional dimension which corresponds to the complementary contour of the sealed opening at the edges (6) of the respective opening; wherein within the opening on both surfaces, a cavity (3) arranged inside the opening is enclosed by the sealing element (2) on one surface, by the counterholder (4) on the other surface of the component (1) and by the outer circumferential surface of the mandrel (5) or by the outer circumferential surface of the counterholder (4) arranged inside the opening and by the edge (6) formed by the separation, and the cavity (3) can be filled through the interior of the mandrel (5) with a polymer resin (8) which can be cured as a result of a subsequent energy input; and the mandrel (5) can be removed from the opening after or during the curing of the resin (8) and the mandrel (5) can be guided from one side of the component (1) through the respective opening until an elastically deformable sealing element (2) made of an elastomeric polymer, which is fastened to the front end face of the mandrel (5) in the direction of insertion, is arranged above the surface of the component (1) and the counterholder (4) rests on the opposite surface of the component (1), wherein with a mechanism of the mandrel (5) after insertion into the opening and arrangement of the sealing element (2) on the corresponding surface of the component (1) is movable in the opposite direction, so that the end face on which the sealing element (2) is arranged moves in the direction of the surface of the component (1) on which the counter-holder (4) touches the component (1), and in the process the sealing element (2) is elastically deformed such that the area with which the sealing element (2) is in contact with the corresponding surface of the component (1) is enlarged. [2] Device according to the preceding claim, characterized by that the counter-alter (4) is formed as a separate part on the mandrel (5) or is attached to the mandrel (5). [3] Device according to one of the preceding claims, characterized bythat the mechanism for moving the mandrel (5) in the opposite direction is a screw connection between the mandrel (5) and the counterholder (4), a linear drive, a pneumatic piston drive, a hydraulic piston drive or a rack and pinion drive. [4] Device according to one of the preceding claims, characterized by that a reduced negative pressure compared to the ambient pressure can be set in the cavity (3) before and / or during filling with the resin (8). [5] Device according to one of the preceding claims, characterized by that a thermosetting resin is used as the resin (8). [6] Device according to one of the preceding claims, characterized by that a component which is ring-shaped or adapted to the inner contour of an opening can be inserted into an opening and can be adhesively connected to the edge by means of the introduced resin (8). [7] Device according to the preceding claim, characterized bythat the component forms a centering device.

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