Method of manufacturing preform element for wind turbine rotor blade

Abstract

A method of manufacturing a preform element for a wind turbine rotor blade is disclosed in which a preform element build material is arranged in a heating device, the preform element build material comprising a fibrous mat arrangement consisting at least of a number of fibrous mats and a binder, in which the preform element build material is heated to melt the binder, and the preform element build material is heated to melt the binder. The preform element is heated to bond the fibrous mats together in order to consolidate the fibrous mat arrangement, and wherein, after heating, at least one piece of information of the preform element is determined at least in some regions in order to assess the degree of consolidation of the fibrous mat arrangement.

Description

Technical Field

[0001] The present invention relates to a method for producing a preformed element for a wind turbine rotor blade, wherein a preformed element building material is arranged in a heating device, the preformed element building material comprising a fiber mat arrangement consisting of at least a plurality of fiber mats and a binder, wherein the preformed element building material is heated to melt the binder and thereby bond the fiber mats together in order to consolidate the fiber mat arrangement. Background Art

[0002] Wind turbine rotor blades consist of a large number of fiber mats made of glass, carbon, or aramid fibers and, if necessary, a core element typically made of wood (such as balsa) or foamed polymer. The fiber mats and core element, as well as any other building elements, are embedded in a resin matrix. This resin is poured into a mold, into which all the blade building elements are arranged.

[0003] Because rotor blades are large items, it is known to use prefabricated preformed elements made from a building material comprising a fiber mat arrangement consisting of at least several fiber mats and a binder. The fiber mats are arranged in a mold along with a non-reactive binder between the fiber mat layers. For example, an epoxy-based binder in powder form is used and pre-applied to one or both sides of each mat, or applied to the fiber mats during the preparation of the fiber mat stack or mat arrangement, or while the fiber mats are being arranged in the mold, possibly with some core elements between them. Once all the preform building materials have been arranged, heat is applied to the arrangement in a heating device, such as a mold, to activate the binder, either melting it or softening it so that it adheres firmly to the fiber mats and core elements. After the binder cures, the fiber mats and core elements are bonded together. Typically, some pressure is applied to the preform building materials before the heating step, for example by placing the entire arrangement under vacuum pressure. Activating the binder and then curing it ultimately bonds all the items together and consolidates the fiber mat arrangement. After curing of the bond, the preformed element is removed from the mold or the heating device and can be used to construct the rotor blade.

[0004] Clearly, the heating process is a necessary step in the manufacturing process of preformed elements. When too little heat is applied to the build material, the binder is insufficiently activated, does not properly adhere to the fiber mats, and thus fails to adequately bond the fiber mats. Because the individual fiber mats are not consolidated and fixed, the preformed element will fall apart when lifted from the mold. On the other hand, if too much heat is applied, the binder migrates into the glass rovings or mat structure, which also makes it difficult to lift the preformed element and creates problems, particularly with respect to resin infusion, later in the manufacturing process of wind turbine rotor blades, where, as mentioned, fluid resin is poured into the mat arrangement of the preformed element. Because the binder has migrated into the fiber mats or rovings, the infusion channels within the structure may become narrow, and proper infusion may not be possible.

[0005] Therefore, there is a process window for the heating cycle to properly activate the adhesive to properly bond the build materials to allow lift and a good infusion process. The process window is generally determined by time and temperature, as well as lift and infusion requirements.

[0006] The thickness distribution of a preform can vary significantly. In some sections, it can be quite thick, for example, 60 mm and above; while at the edges and scarfs, the thickness can drop to a few millimeters, or even to around 1 mm. This makes it difficult to properly heat the preform element, as thicker sections require more heat than thinner ones, while at the same time, overheating of thinner sections must be avoided. Therefore, the heating process and the heat distribution during this process play a significant role in the quality of the preform element, which needs to be as good as possible, as the preform element is merely an intermediate product used later in the manufacturing process of the turbine blade, whose quality also depends on the quality of the preform element. Summary of the Invention

[0007] It is therefore an object of the present invention to provide an improved method for producing a preformed element.

[0008] To achieve this object, the method according to the invention for producing a preformed element for a wind turbine rotor blade is characterized in that after heating, at least one item of information of the preformed element is at least partially determined to assess the degree of consolidation of the fiber mat arrangement.

[0009] The present invention proposes implementing quality control after the production of a preformed element. After heating the material, when the preformed element has cooled down to solidify the previously heated and melted binder and thereby consolidate the fiber mat arrangement, at least one information item about the preformed element is determined, based on which the degree of consolidation of the fiber mat arrangement can be determined. This information allows the quality of the bond or the compaction of the preform or fiber mat arrangement to be determined. Thus, it can be determined whether the binder activation was sufficient and whether the bond quality corresponds to the requested bond and consolidation structure. This method allows an assessment of whether the applied heat was too little, too much, or the correct amount, and ultimately, whether the quality of the preformed element corresponds to the requested quality parameters for the further production of the preformed element in a turbine blade.

[0010] This information is determined at least locally at the preform element. Information can be determined at several points distributed across the area of ​​the preform element, in particular at locations where its thickness significantly changes, so that at these different element locations, the corresponding information can be evaluated to determine the local degree of consolidation. This allows the creation of a consolidation distribution or map over the preform element. Of course, the information can also be determined globally, rather than locally, so that the entire preform element can be investigated with respect to the degree of consolidation or the quality of the preform compaction and bonding.

[0011] After performing quality control, it can be determined whether the preformed element meets the quality parameters so that it can be used later in the manufacturing process. If the preformed element is of poor quality, it may not be used to build the blade, which in turn avoids any quality issues during the blade manufacturing process.

[0012] The information determined is preferably density information. During the determination process, information is determined that serves as a measure of the density of the preformed element. If the binder does not bond the fiber mat, consolidation or compaction is poor, the binder has not been properly activated and has not melted. The density or compaction is quite low. On the other hand, if the activation is too strong or too much heat is applied, the binder migrates and the compaction may be too high, resulting in a very high density. Therefore, density information is an appropriate basis for assessing the degree of consolidation.

[0013] As density information on the basis of which the degree of consolidation is determined, the average density distribution in the investigated volume is measured or determined. The average density information is direct information for determining whether the preformed component has been subjected to an appropriate heating cycle. The average density distribution is measured within a defined measurement volume or envelope (e.g. 50–150 mm on a cross-section of the item to be inspected). If it becomes too small, noise will obscure the signal; if it becomes too wide, the significance of the differences will be obscured. The average density distribution allows the degree of consolidation and the component quality to be identified, based on which the preformed component can ultimately be marked as a good component or a reject component.

[0014] As mentioned, determining information, in particular density information or an average density distribution, in some areas of the preformed element allows the creation of a type of information or a local map of the density information. Alternatively, a global information determination can also be carried out.

[0015] Preferably, information, in particular density information or average density distribution, is determined by radiometric measurement using a radiation source and a radiation detector. According to this embodiment, a scan of the preformed element is performed to determine the corresponding information based on the radiation scan. The radiation source applies radiation to the preformed element being produced. The radiation detector provides a corresponding measurement signal, which in turn provides corresponding information on the degree of consolidation. This radiometric measurement is a relatively simple, non-destructive measurement that provides very fast and reliable information from the measured volume or envelope.

[0016] Radiation measurement can be a transmission measurement, in which radiation is transmitted through the preform element. A radiation source is positioned on one side of the preform element, and a radiation detector is positioned on the other side. Alternatively, radiation measurement can be a backscatter measurement. In this embodiment, both the radiation source and the radiation detector are positioned on the same side of the preform element. Radiation is applied to the preform element, and the detector detects the backscattered radiation. Both transmission and backscatter measurements provide corresponding radiation information, which can also be visualized in the form of a graph to intuitively illustrate the density distribution.

[0017] Radiometric measurements can be either X-ray or ultrasonic. Both types of radiometric measurements provide excellent results. To generate X-rays, an electron beam can be accelerated onto an anode target, whereby X-ray radiation is generated when the electrons strike the anode target. Alternatively, radiation can be generated using one of the radioactive isotopes cobalt-60, iridium-192, selenium-75, thallium-170, cesium-137, or ytterbium-169.

[0018] Radiometric measurements, particularly X-ray or ultrasonic measurements, provide information about the preform element being investigated, or average density distribution information. To assess the required information regarding the degree of consolidation or compaction, the measured thickness or information must be processed. According to the present invention, the assessed information, particularly the average density distribution information, is compared with reference information, particularly reference average density distribution information. This reference information can be gathered, for example, by conducting a series of reference tests using a specified heating cycle and several specific or standardized build material arrangements, the required configurations for this particular type of preform element. By conducting these series of reference tests, a database can be created that illustrates how different heating cycles using different materials or material arrangements can lead to different information or average density distribution information or radiometric measurement results. The reference information is then identified or referred to as the preform element quality that meets all requirements. When actual information or measurement results are compared with the reference test results, any deviation from the reference information or reference results indicates a quality difference between the actual preform element and the reference preform element. The reference database can also be used to impose certain criteria for the required consolidation level in order to approve unknown heating cycles. Likewise, reference tests with different preform layer thicknesses or different arrangements of preform building materials can also be used as a reference.

[0019] The method of the present invention achieves quality control by investigating the preformed elements themselves by investigating or scanning the dry preformed elements or fiber mat arrangements before the preformed elements have been cast or poured in resin and thus embedded in the resin matrix of the turbine blade. The investigation or scanning is used to measure the consolidation level of the fiber mat arrangement, which is then correlated with the heating cycle it has been subjected to. Since the quality control is carried out on the preformed elements themselves, precise quality information is at hand in order to identify any preformed elements that do not meet the quality requirements. The present invention therefore ensures that only preformed elements that meet the strict quality requirements are placed in the blade mold and then cast into a blade or blade part. Therefore, a lot of additional repair work on the final cast turbine blade or turbine blade part can be avoided because any possible preformed element defects are caught before the blade building process.

[0020] The invention also relates to a preformed element produced according to the method previously described.

[0021] The present invention also relates to a method for manufacturing a wind turbine rotor blade or rotor blade part. This method is characterized in that several preformed elements produced as described above or according to the previously discussed method are arranged in a manufacturing mold and then resin is infused to form a resin matrix in which the preformed elements are embedded.

[0022] This method for manufacturing blades or blade sections is focused on using only quality-controlled preformed elements that meet the high quality standards set for the preformed element manufacturing method. Thus, the inventive method for manufacturing rotor blades or rotor blade sections ensures that the ultimately produced blades or blade sections will be free of defects caused by low-quality preformed elements or preformed elements that themselves have defects.

[0023] Finally, the invention also relates to a wind turbine rotor blade or rotor blade part manufactured as previously discussed. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Other objects and features of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings. However, the accompanying drawings are only schematic diagrams designed for illustrative purposes and do not limit the present invention. The accompanying drawings show:

[0025] Figure 1 shows a manufacturing scheme which explains the central steps of the method according to the invention for producing a preformed element and the central steps of further processing the produced preformed element to produce a wind turbine blade or blade part,

[0026] Figure 2 is a schematic sketch of a first embodiment for implementing quality control of preformed elements, and

[0027] Figure 3 is a schematic sketch of a second embodiment of the quality control of preformed elements. DETAILED DESCRIPTION

[0028] Figure 1 The central step of the method of the present invention for manufacturing a preformed element for a wind turbine rotor blade or rotor blade portion is shown. In step S1, all preformed component building materials (including a plurality of fiber mats, including glass fiber, carbon fiber or aramid fiber) are arranged or stacked in a preformed component manufacturing mold, which is a heating device because it is suitable for applying heat to the preformed component building materials. The heating device defines the geometry of the final preformed element. In addition to the fiber mats, some core elements can be arranged and sandwiched between the fiber mats. Finally, a binder is provided, which is preferably an epoxy-based binder. It is arranged between the fiber mat layers. The non-reactive binder can be applied in powder form directly to one or both sides of the fiber mat before stacking the individual fiber mats, or applied between the respective fiber mats during stacking of the fiber mats in the heating device. At the end of step S1, all preformed component building materials are arranged in the desired arrangement or stacked in the heating device.

[0029] In step S2, a certain pressure is applied to the build material arrangement. This can be achieved, for example, by placing a cover layer above the build material arrangement, which seals the arrangement to the heating device or mold, so that a vacuum can be applied below the upper sealing layer, thereby pressing the sealing layer against the heating device, thereby compacting the build material arrangement.

[0030] In step S3, heat is applied to the build material arrangement to soften or melt the binder. The binder adheres to the fiber mat or core element, where it adheres to the fiber mat or core element and securely binds the fiber mat or core element together through a material-to-material bond. Heating is performed using a specific heating cycle defined, for example, by respective heating ramps for increasing and decreasing the temperature and a specific hold time at a given temperature.

[0031] After heating, the heated arrangement is cooled in step S4. This cooling solidifies the binder, which now provides a bonding matrix that firmly connects the fiber mat and the core element together, thereby providing a compacted preformed element. All individual building material items (i.e., the fiber mat and, if present, the core element) are firmly bonded together so that, ideally, no more individual items exist.

[0032] Now, two possibilities for further processing are presented. According to step S5, the preformed element is lifted from the heating device and transported to an investigation arrangement for collecting at least one piece of information about the preformed element, in order to assess the degree of consolidation of the fiber mat arrangement. However, step S5 is not necessary if this information can be collected while the preformed element is still in the heating device or mold. Therefore, step S5 is optional, depending on the location where the investigation can be performed.

[0033] This information collection is performed in step S6. In this step, after heating or curing the binder, at least one piece of information is determined at least locally on the preform element to assess the fiber mat arrangement or the degree of consolidation of the preform building element material. In this step, preferably, a radiometric measurement is performed to collect the corresponding information based on measurement values ​​or signals. This radiometric measurement can be a transmission measurement or a backscatter measurement, wherein X-rays or ultrasound can be used as the scanning radiation. The corresponding information collection can be performed locally only in certain designated areas on the preform element; alternatively, the entire preform element can be scanned over its entire area.

[0034] Thus, the corresponding information provides local information, like local mean density information, which enables a local quality determination, or it provides global information, like global mean density information, which enables a global quality determination.

[0035] The mass information or radiation signal measured by the radiation device allows determination of the average density distribution of the preform arrangement, which describes the degree of consolidation of the bond quality. The scanning of the preform can be based on digital transmission or backscatter measurements. By measuring or determining the average density distribution in the scanned area or within a defined measurement envelope, differences in consolidation of the investigated preform compared to a reference preform are identified. The measurement envelope is defined to correspond to the investigated thickness or cross-section of the preform to be inspected, so as to provide an acceptable signal-to-noise ratio.

[0036] As mentioned, in step S6, information is preferably collected in the form of density information, such as the average density distribution of the scanned area. This information is then processed in step S7. In this step, it is compared with previously collected reference information. This reference information is provided in a database and was collected by conducting a series of reference tests using a specified heating cycle. The database shows how different heating cycles on different materials can lead to different measurement results or information, or average density distribution information. For example, since the exact build material arrangement corresponding to specific requirements, as arranged in step S1, is known, the actual measurement results can be compared using corresponding reference measurements of the same build material arrangement. Ultimately, the comparison shows whether the actual measurement results, such as the density distribution, correspond to the corresponding reference information or reference density distribution, or whether there are any discrepancies. The extent of the discrepancy can be assessed, and ultimately, whether the discrepancy is still acceptable can be determined. Based on this comparison, the preform component can be deemed acceptable in step S8. This preform component can then be used for further processing to construct a turbine blade. Alternatively, if the discrepancy is too great, the preform component is deemed rejectable in step S9 and is not further processed.

[0037] Figure 1 The further processing of the preformed element of the required quality is also shown. Immediately after quality control, or after a certain time, the preformed element is arranged in a blade construction mold together with a number of other qualified preformed elements and the corresponding other blade construction materials in step S10. In this step, the blade construction materials are arranged according to the corresponding requirements so that a specific arrangement, stack, etc. is built in the blade mold. When all the construction materials have been arranged, resin infusion is carried out in step S11. In this step, resin is infused into the blade construction material arrangement, which completely embeds all the blade construction materials. After this infusion, the resin is cured in step S12, so that a single-piece turbine blade or turbine blade section is finally built and removed from the mold in step S13.

[0038] Figure 2A schematic diagram shows the principle of quality control for a produced preformed element 1. The preformed element has a specific geometry and a specific size. As mentioned, it is produced according to the previous method in steps S1-S4. In this diagram, the preformed element has two longitudinal edge sections 2, 3 with significantly varying thicknesses. The thickness of the rest of the preformed element may be somewhat uniform, but even then, some variation may exist.

[0039] The figure also shows an investigation arrangement 4, which includes a radiation device 5 having a radiation source 6 and a radiation detector 7. The radiation source is, for example, an X-ray source that emits X-ray radiation 8. The detector 7 is adapted to receive the X-ray radiation 8 and provide corresponding detection signals. A control device 9 is provided that controls both the radiation source 6 and the detector 7 and processes the detection signals received from the detector 7. A monitor 10 can be used to display the corresponding investigation results, or even to display corresponding radiation images created based on the detection signals from the radiation detector 7, which can be visually analyzed.

[0040] The radiation device 5 is a transmission device. Radiation 8 is transmitted through the preformed element. Detectors 7 detect the transmitted radiation and provide transmission signals to a control device 9, which processes these signals to evaluate information or density information and further evaluate information about the degree of consolidation of the preformed element.

[0041] In order to scan a specific local area or in order to perform an overall scan, both the radiation source 6 and the radiation detector 7 can be moved in the longitudinal and transverse direction of the preform element 1 .

[0042] Figure 3 Another embodiment of the survey arrangement 4 is shown. Figure 2 The radiation device 5 also includes a radiation source 6, such as an X-ray radiation source, and a radiation detector 7 for detecting specific radiation. The radiation source 6 emits radiation 8, such as X-ray radiation, toward the preform element 1. The radiation is backscattered from the preform element 1 and received by the detector 7. Since backscatter measurements are performed in this embodiment, both the radiation source 6 and the radiation detector 7 are arranged on the same side of the preform element 1. This allows investigations to be performed from only one side, even in a mold or heating device that previously produced the preform element 1.

[0043] Likewise, the control device 9 receives and processes the respective detector signal, for example comparing it with reference information, in order to determine the respective degree of consolidation and thus the quality of the preformed element 1. The determination result can then likewise be displayed at the monitor 10.

[0044] While the present invention has been described in detail with reference to the preferred embodiments, the present invention is not limited to the disclosed examples, and those skilled in the art will be able to devise other variations based on the disclosed examples without departing from the scope of the present invention.

Claims

1. A method for producing a preformed element for a wind turbine rotor blade, wherein: A preformed element building material is arranged in a heating device, the preformed element building material comprising a fiber mat arrangement consisting of at least a plurality of fiber mats and a binder, wherein the preformed element building material is heated to melt the binder, thereby bonding the fiber mats together to consolidate the fiber mat arrangement, characterized in that after heating, at least one information of the preformed element (1) is at least partially determined to evaluate the degree of consolidation of the fiber mat arrangement.

2. The method according to claim 1, characterized in that The information is density information.

3. The method according to claim 2, characterized in that The density information is the average density distribution.

4. The method according to any one of the preceding claims, characterized in that The information, in particular the density information or the average density distribution, is determined in regions of the preform element (1) or over the entire preform element (1).

5. The method according to any one of the preceding claims, characterized in that The information, in particular the density information, is determined by radiometric measurement using a radiation source (6) and a radiation detector (7).

6. The method according to claim 5, characterized in that The radiation measurement is a transmission measurement or a backscatter measurement.

7. The method according to claim 5 or 6, characterized in that The radiation measurement is X-ray measurement or ultrasound measurement.

8. The method according to any one of the preceding claims, characterized in that The evaluated information, in particular density information, is compared with reference information, in particular reference density information.

9. A preformed element (1) produced according to the method according to any one of the preceding claims.

10. A method for producing a wind turbine rotor blade or a rotor blade part, characterized in that Several preformed elements (1) according to claim 9 are arranged in a manufacturing mould and then resin is infused to build up a resin matrix in which the preformed elements are embedded.

11. A wind turbine rotor blade or rotor blade part manufactured according to the method of claim 10.

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