METHOD FOR DETERMINING A MIXTURE RATIO

Description

[0001] The invention relates to a method for determining a mixing ratio of a multi-component homogeneous material mixture in the form of a multi-component epoxy resin system flowing in a piping system, by means of a sensor system that touches the material mixture and has at least one sensor with a sensor surface that is contacted by the flowing material mixture to determine the mixing ratio.

[0002] The invention also relates to a method for producing a fiber composite component in which a fiber material is infused with the multi-component matrix material mixture and the infused multi-component matrix material mixture is cured.

[0003] Due to their high strength-to-weight ratio and stiffness, fiber-reinforced composites are indispensable in the aerospace industry and other weight-critical sectors. Fiber-reinforced composites consist primarily of two main components: a fiber material and a matrix material that embeds the fiber material. In the production of fiber-reinforced composite components, the fiber material is typically shaped into the desired component form, and the matrix material is then cured. Curing is almost always achieved through temperature and, if necessary, pressure. During curing, the load-bearing fibers of the fiber material are forced into their predetermined orientation, forming an integral unit with the cured matrix material for load transfer.

[0004] The matrix material, which embeds the fiber material of the fiber-reinforced composite, can already be contained within the fiber material itself (so-called prepregs) or subsequently infused into a fiber preform, built up from dry fiber materials, using an infusion process. A fiber preform is a type of pre-component formed from the fiber material of the fiber-reinforced composite and at least partially reflects the final shape of the fiber-reinforced composite component to be manufactured. The fiber-reinforced composite component is then produced by curing the matrix material embedded within the fiber material of the fiber preform. The fiber preform can therefore be made from either dry fiber material or pre-impregnated fiber materials of a fiber-reinforced composite. Depending on the type of fiber material used, the fiber-reinforced composites used are primarily CFRP (carbon fiber reinforced polymer) and GFRP (glass fiber reinforced polymer).

[0005] There is an effort to use a matrix material when working with dry fiber materials. This matrix material is assembled on-site from several components shortly before infusion into the fiber material. Multi-component epoxy resin systems are suitable for this purpose. The advantage over single-component resin systems is that the material is separated into individual components, particularly a resin component and a hardener component. This significantly delays or even prevents the crosslinking of the matrix material. As a result, the components can be transported and stored with considerably reduced safety restrictions. Storage can take place at elevated temperatures, and the shelf life of the individual components is extended.

[0006] Shortly before the matrix material is infused into the fiber material of the component, the individual components of the matrix system are combined in a predetermined mixing ratio and homogeneously blended. The resulting material mixture is then infused into the fiber material. This combining and blending of the individual components to produce the marine component matrix system can be carried out inline within the process, meaning that the combined components are immediately infused into the component via a piping or hose system.

[0007] A key requirement when using a multi-component matrix system is that the correct mixing ratio can be verified as directly as possible during the process. This is the only way to ensure that the manufactured component was produced with the specified matrix system. This is necessary because the mixing ratio is adjusted during the process itself, during the infusion of the matrix system.

[0008] When analyzing the mixing ratio of multi-component matrix systems, contact sensors are typically used, requiring direct contact with the flowing medium of the matrix system. However, it has been observed that a film of material (resin film) forms directly on these sensors, which must be displaced by the flowing material (resin). If the viscosity of the flowing material is higher, the change in the mixing ratio can be accurately detected by the respective sensor. However, if the viscosity is lower, the change in the mixing ratio can be poorly or not at all detected by the sensor because the low-viscosity, flowing material cannot displace the film of material that has formed directly on the sensor.

[0009] A phase is formed which is correctly analyzed by the sensor, but which is not dependent on temperature (resin). Problems arise when the layer in contact with the sensor cools down compared to the flowing medium. To resolve this issue, a rinsing process would need to take place before the change in the mixing ratio leads to a reduction in the viscosity of the resin mixture.

[0010] In practice, such a change in the mixing ratio during the process cannot be planned. Rather, mixture analysis serves to detect such unintended changes within the framework of quality management. Currently, it can therefore happen that a disruption in the process is not detected by the analysis and a component with an incorrect mixing ratio is not identified as a defective part. Since mechanical and thermal properties also depend on the mixing ratio, this can lead to significant safety compromises. As a consequence, an analysis method that exhibits the aforementioned problems cannot be used in production, and therefore neither can multi-component epoxy resin systems whose individual components have different viscosities.

[0011] US patent 2015 / 0152759 A1 discloses a water separation system for oil tanks to separate water that collects in the oil. The system includes a sensor to detect water in the oil within a pipe.

[0012] A similar approach is revealed in CN113484495A, which aims to detect particles in the fuel supply of a diesel vehicle. Here, too, various sensors are provided, which are to be cleaned using a mechanical cleaning process.

[0013] From DE 10 2018 130 953 A1, a method and a device for determining the mixing ratio of a material mixture consisting of two or more components are known. To determine the mixing ratio, a dielectric characteristic value is calculated.

[0014] It is therefore an object of the present invention to provide an improved method for mixture analysis when using multi-component matrix systems, without having to interrupt a process.

[0015] The problem is solved according to the invention by the method for determining a mixing ratio of a flowing, multi-component material mixture according to claim 1. Advantageous embodiments of the invention are found in the corresponding dependent claims.

[0016] According to claim 1, a method for determining the mixing ratio of a flowing, multi-component homogeneous material mixture in the form of a multi-component epoxy resin system, which flows within a piping system (for example, a pipe or a hose), is proposed. For determining the mixing ratio, a contact sensor is provided which is in operative contact with the material mixture flowing in the piping system. The sensor has a sensor surface that is contacted by the flowing material mixture to determine the mixing ratio.

[0017] The flowing material mixture was made from two or more individual components and is therefore a multi-component material mixture.

[0018] According to the invention, a first aspect provides that the material mixture adhering to the sensor surface is removed or reduced by means of a mechanical cleaner through a relative movement between the sensor and / or sensor surface and the cleaner.

[0019] It is therefore proposed that a mechanical cleaner, which is in mechanical contact with the sensor surface, is used to clean the sensor surface by removing or reducing residues of the material mixture adhering to the sensor surface due to a relative movement between the sensor surface and the cleaner.

[0020] This ensures that the sensor surface regularly comes into contact with the material mixture that is actually flowing past the sensor. This prevents residues of the material mixture from remaining on the sensor surface, which could impair the sensor's ability to accurately detect the current mixture ratio. By removing the material mixture adhering to the sensor surface with the mechanical cleaner, the sensor comes into regular contact with the actual material mixture flowing past it, allowing it to determine the current mixture ratio. This enables the early detection of sudden or unexpected changes in the mixture ratio.

[0021] The relative movement between the sensor surface and the mechanical cleaner can occur in such a way that the sensor and its surface are fixed in place, and the mechanical cleaner acts like a wiper, sweeping across the sensor surface and removing any residue of the material mixture adhering to it. Alternatively, the sensor surface and / or the sensor itself can be mounted in a movable manner and move relative to a fixed mechanical cleaner. In this case as well, residues of the material mixture are removed from the sensor surface.

[0022] The mechanical cleaner can be designed and configured to allow flexible contact between the sensor surface and the cleaner, for example, by using a flexible cleaner made of a flexible material such as rubber, caoutchouc, or silicone. Alternatively, the sensor surface or the sensor itself can be designed to be flexible to enable flexible cleaning contact. For this purpose, the sensor can, for example, have a flexible mounting by being attached to a flexible surface.

[0023] The cleaner can be designed similarly to a rubber squeegee. However, a solid metal plunger is also conceivable, which removes or displaces the adhering material mixture through displacement.

[0024] Such a sensor could, for example, be one that determines the mixing ratio based on a dielectric constant measurement (DCT). However, sensors based on ultrasound, refractometry, near-field infrared (NIR), rheometry, and / or imaging sensors are also suitable for determining the mixing ratio.

[0025] According to the invention, a second aspect provides that the sensor with the sensor surface for determining the mixing ratio is provided in such a way that the sensor surface has a non-stick coating.

[0026] This achieves the goal of preventing the material mixture flowing along the sensor surface from adhering to it when the multi-component mixture falls below a certain viscosity threshold. This ensures that the sensor surface remains free of residue from the material mixture, as this residue does not adhere to the non-stick coating.

[0027] Such a non-stick property can be achieved, for example, through a suitable surface structure that creates a lotus effect. A coating with a suitable non-stick agent is also conceivable.

[0028] The first and second aspects of the invention can be presented as alternatives or together in combination.

[0029] According to one embodiment, the material mixture adhering to the sensor surface is removed using a rod-shaped cleaner, a rubber lip cleaner, a sponge cleaner, and / or a scraper cleaner. The scraper can be made of a rigid material, e.g., metal.

[0030] Such a rod-shaped cleaner preferably extends over the entire extent of the sensor surface and can therefore clean the entire sensor surface with a single relative movement.

[0031] According to one embodiment, the cleaner is moved translationally and / or rotationally and / or by vibration to remove the material mixture adhering to the sensor surface.

[0032] In combination with the rod-shaped cleaner, it is therefore advantageous if the rod-shaped cleaner is moved translationally across the entire sensor surface. However, it is also conceivable that the rod-shaped cleaner rotates around its own axis while simultaneously gliding across the sensor surface. Cleaning the sensor surface can also be achieved in combination with vibration and, for example, in conjunction with a translational movement.

[0033] According to the invention, the multi-component material mixture is a multi-component epoxy resin system.

[0034] Such a multi-component epoxy resin system can, for example, be formed as a material mixture from the two individual components epoxy resin and hardener.

[0035] According to one embodiment, the multi-component material mixture is designed to have a viscosity of less than 1000 mPa*s, preferably less than 500 mPa*s, and particularly preferably less than 100 mPa*s, at the desired process temperature. However, it is also conceivable that the multi-component material mixture has a significantly lower viscosity of less than 25 mPa*s, preferably less than 10 mPa*s, and particularly preferably less than 3 mPa*s, at the desired process temperature. It may be particularly preferred if the multi-component material mixture has a viscosity at process temperature that is approximately the viscosity of water at a temperature of 5°C or higher.

[0036] Thus, a low viscosity in combination with a non-stick coating of the sensor surface and / or the mechanical cleaner ensures that residues of the material mixture do not stick and can also be easily removed from the sensor surface by the mechanical cleaner.

[0037] According to one embodiment, it is provided that, depending on the determined mixing ratio, a directional control valve within the piping system is controlled in such a way that, in the case of an insufficient mixing ratio, the material mixture is discharged from the piping system as rejects.

[0038] The directional control valve is positioned in the piping system downstream of the sensor in contact with the material mixture, in the direction of flow. This allows a control unit connected to the sensor to react to an insufficient mixing ratio by moving the directional control valve to a position where the material mixture is discharged from the piping system as rejects. The material mixture is then no longer used for production, for example, it is no longer introduced into the fiber material of a fiber composite component. Conversely, if a sufficient mixing ratio is detected that can be used in production, the directional control valve is moved to a position where the material mixture can be used for production, for example, by infusing it into a fiber material.

[0039] This ensures that, in the event of an incorrect mixing ratio, the material mixture does not contaminate the entire component. This reduces rejects due to poor material mixtures and thus saves costs. Furthermore, the same objective is achieved by the method for producing a fiber composite component according to claim 7, in which a fiber material is infused with a multi-component matrix material mixture and the infused multi-component matrix material mixture is cured. The method comprises the following steps: Providing the individual components of the multi-component matrix material mixture, combining and mixing the individual components to obtain the multi-component matrix material mixture, and infusing the multi-component matrix material mixture into the fiber material, determining a mixing ratio of the flowing multi-component matrix material mixture according to the procedure described above.

[0040] The individual components are provided in a separate, unmixed mold core, i.e., as individual components. Preferably, the individual components are then combined and mixed into the fiber material during infusion, so that the mixing of the individual components occurs inline during the infusion process.

[0041] According to one embodiment, the infusion of the multi-component matrix material mixture is controlled depending on the determined mixing ratio.

[0042] The process can be stopped, for example, if it is determined that the mixing ratio is not within the specified tolerance range. It is conceivable that a valve could be used to stop the infusion once the mixing ratio is again within the specified tolerance range.

[0043] The invention is explained in more detail using the attached figures as examples. They show: Figure 1 schematic representation of a manufacturing plant for the production of a fiber composite component; Figure 2 schematic representation of a sensor with cleaner.

[0044] Figure 1Figure 10 shows a production plant 10 with which a fiber composite component can be manufactured. For this purpose, a mold 11 is provided onto which a fiber material 12 is placed to produce a fiber preform. After the dry fiber material 12 penetrates the mold 11, it is infused with a multi-component matrix system (e.g., a multi-component epoxy resin system) to completely impregnate the fiber material 12. The matrix system is then cured to produce the component.

[0045] The multi-component matrix system is mixed from two individual components during infusion into the fiber material. These components are provided separately as crosslinking material 20 (resin system) and hardener material 21. Using a mixing device 22, the crosslinking material 20 and the hardener material 21 are blended into a common multi-component matrix system, which is then infused into the fiber material 12.

[0046] The multi-component matrix system thus mixed is now fed to the fiber material 12 via a piping system 23 in order to impregnate the fiber material 12 with the multi-component matrix system.

[0047] A first sensor 30 is arranged in the piping system 23, which is designed to determine the mixing ratio of the multi-component matrix system. The sensor 30 is connected to a control unit 40, which is designed to control the plant process of the production plant 10.

[0048] The sensor 30 continuously monitors the mixing ratio of the multi-component matrix system, which flows towards the fiber material 12.

[0049] If a mixing ratio is detected that is outside the tolerance range, the production plant 10 can be configured to interrupt or shut off the material flow towards the fiber material 12 in order to prevent the fiber material 12 from being infused with a multi-component matrix system that has an incorrect mixing ratio. Once the error has been corrected and the mixing ratio is again within the tolerance range, the material flow can be resumed or the piping system 30 can be readjusted to allow material flow into the fiber material 12.

[0050] In Figure 1An advantageous further development is shown in which a second sensor 30a is provided in the piping system 23, which is also connected to the control unit 40 and is designed to detect the mixing ratio of the material mixture. A directional control valve 33 is provided in the piping system 23 between the first sensor 30 and the second sensor 30a, which is configured to either allow passage from the mixing device 22 into the fiber material 12 or to discharge the material mixture from the piping system as rejects.

[0051] If the first sensor 30 detects a mixing ratio that the control unit 40 classifies as unacceptable, the entire infusion process can be interrupted. The directional control valve is then adjusted so that the material mixture is diverted from the piping system as reject material. The second sensor 30a, located downstream of the directional control valve in the piping system, monitors the flow of an insufficient material mixture into the component. Only when the first sensor 30 detects an acceptable material mixture can the directional control valve be moved back to a position that allows flow into the fiber material for infusion.

[0052] Figure 2Figure 1 shows a simplified schematic representation of a sensor 30, 30a which has a sensor surface 31, 31a which comes into contact with the multi-component matrix system when the multi-component matrix system is infused into the fiber material 12 or more generally when the multi-component matrix system flows in a fluid channel.

[0053] To remove any residues of the multi-component matrix system from the sensor surface 31, 31a, a rod-shaped cleaner 32 is provided, which is designed to be movable along the sensor surface 31, 31a and thus remove residues of the material mixture. For this purpose, the cleaner 32 can be made of a flexible material, for example, rubber.

[0054] It may be provided that the sensor surface 31, 31a is coated with a non-stick coating in order to largely avoid possible adhesion by utilizing the lotus effect. Reference symbol list

[0055] 10 Production equipment 11 Mold 12 Fiber material 20 First component / crosslinking material / resin 21 Second component / hardener 22 Mixing device 23 Piping system 30 Sensor 31 Sensor surface 32 Mechanical cleaner 33 Directional control valve 34 Rinsing tank 35 Rinsing agent 40 Control unit

Claims

1. Method for determining a mixing ratio of a multi-component homogeneous material mixture flowing in a pipe system (23) in the form of a multi-component epoxy resin system by means of a sensor system contacting the homogeneous material mixture, which has at least one sensor (30) with a sensor surface (31) that is contacted by the flowing material mixture for determining the mixing ratio, characterized in that - a mechanical cleaner (32) is used to remove or reduce the material mixture adhering to the sensor surface (31) by means of a relative movement between the sensor (30) and / or sensor surface (31) and the cleaner (32), and / or - a sensor (30) is provided with a sensor surface (31) that has a non-stick coating.

2. Method according to claim 1, characterized in that the mixture of materials adhering to the sensor surface (31) is removed by means of a rod-shaped cleaner (32), by means of a rubber lip as a cleaner, by means of a sponge as a cleaner, and / or by means of a scraper as a cleaner.

3. Method according to claim 1 or 2, characterized in that the relative movement is effected by moving the sensor (30) and / or by moving the cleaner (32).

4. Method according to one of the preceding claims, characterized in that the cleaner (32) is moved in a translatory and / or rotary and / or vibrating manner to remove the mixture of materials adhering to the sensor surface (31).

5. Method according to one of the preceding claims, characterized in that the multi-component material mixture has a viscosity of less than 1000 mPa*s, preferably less than 500 mPa*s, particularly preferably less than 100 mPa*s at the desired process temperature.

6. Method according to one of the preceding claims, characterized in that, depending on the determined mixing ratio, a directional control valve within the pipe system is controlled in such a way that, if the mixing ratio is insufficient, the material mixture is discharged from the pipe system as waste.

7. Method for producing a fiber composite component, in which a fiber material (12) is infused with a multi-component matrix material mixture and the infused multi-component matrix material mixture is cured, comprising - providing the separate components (20, 21) of the multi-component matrix material mixture, - combining and mixing the separate components (20, 21) to obtain the multi-component matrix material mixture, and - infusing the multi-component matrix material mixture into the fiber material (12), characterized by - determining a mixing ratio of the flowing multi-component matrix material mixture according to the method according to one of claims 1 to 6.

8. Method according to claim 7, characterized in that the infusion of the multi-component matrix material mixture is controlled depending on the determined mixing ratio.

9. Method according to claim 7 or 8, characterized in that, depending on the determined mixing ratio, a directional control valve within the pipe system is controlled in such a way that, if the mixing ratio is insufficient, the multi-component matrix material mixture is not infused into the fiber material.