Method and device for inline quality control of continuously produced fiber composite semi-finished products

Abstract

For inline quality control of continuously produced and conveyed continuous fiber composite semi-finished products (4) in a conveying direction (2), the fiber composite semi-finished product (4) is supported in a first direction (7) of a test axis (5) extending transversely to the conveying direction (2) in two first support areas (8) which have a first support spacing in the conveying direction (2). In a second direction (13) of the test axis (5) extending transversely to the conveying direction (2), opposite to the first direction (7), the fiber composite semi-finished product (4) is supported in a second support area (14) which is arranged in the conveying direction (2) between the two first support areas (8).At least two different relative positions of the first support areas (8) with respect to the second support area (14) are set by relocating at least one of the support areas (8, 14) along the test axis (5) in order to alternately induce at least two different bending stress states of the conveyed fiber composite semi-finished product (4). In the at least two different bending stress states, reaction forces of the fiber composite semi-finished product (4) are measured in the second direction (13) on the second support area (14) and / or in the first direction (7) on the first support areas (8).

Description

TECHNICAL AREA OF INVENTION

[0001] The invention relates to a method for inline quality control of continuously produced and conveyed continuous fiber composite semi-finished products. Furthermore, the invention relates to a device for detecting material properties of continuous test material conveyed in a single direction. This test material can be continuously produced and conveyed continuous fiber composite semi-finished products. STATE OF THE ART

[0002] It is known to additively manufacture fiber composite components using 3D printing from quasi-continuous, interconnected fiber composite semi-finished products. The quality of the fiber composite components produced in this way depends on the quality of the fiber composite semi-finished products used, particularly with regard to the mechanical strength of the fiber composite components. This also applies to fiber composite components produced from quasi-continuous, interconnected fiber composite semi-finished products using other methods.

[0003] Within the manufacturing of quasi-endless, continuous fiber composite semi-finished products, it is known to continuously measure the geometry, color, and temperature of each product. Furthermore, continuous monitoring using micro-CT or acoustic testing is also known. Mechanical properties, such as the Young's modulus, are currently determined on destructively extracted test specimens.

[0004] From DE 10 2016 116 258 A1, a device and a method for stress testing of discs made of a brittle, hard material with two opposing surfaces, in particular glass, which has a defined tensile strength, are known. The element is guided over a roller with each of its surfaces and bent, so that each surface is subjected to tensile stress in the area where the opposite surface is in contact with the roller surface. Furthermore, a tensile force is exerted on the element in the direction of movement, so that both surfaces are under a tensile stress of at least 2 MPa.This tensile stress and the tensile stress that arises from bending over the respective roller on the side surface facing away from the roller are added to a resultant tensile stress, and it is monitored and determined whether the element has a defined breaking strength equal to the resultant tensile stress, or whether the element breaks under the applied resultant tensile stress.

[0005] From DD 16 903 A1, a method and a device for investigating the fatigue resistance of yarns, threads, and monofilaments under bending stress are known. The respective test specimen is guided as an endless strip over several rotating deflection elements while observing a specific tensile stress, and the change in its physical-mechanical properties after a specific test period due to the stress on the test specimen is investigated with regard to its fatigue resistance.

[0006] From EP 1 637 866 A1, a method and a device for bending tests of cards with integrated antennas are known. A bending force is exerted on the card by means of a pressure roller, essentially perpendicular to the conveying plane, wherein the card, during its conveying movement, is subjected to a bending force acting perpendicular to the conveying plane by means of a conveying means, along a conveying path that extends essentially in a conveying plane. The pressure roller, which is sufficiently high in the conveying plane and extends over the entire transverse direction of the card, is continuously subjected to a bending force acting perpendicular to the conveying plane from a front end of the card (in the conveying direction) to a rear end of the card (in the conveying direction). TASK OF INVENTION

[0007] The object of the invention is to demonstrate a method and a device with which further inline control of the quality of continuously produced and conveyed in one conveying direction of continuous fiber composite semi-finished products is possible, which also extends to mechanical properties. SOLUTION

[0008] The object of the invention is achieved by a method with the features of claim 1 and a device with the features of claim 10. The further claims are directed to preferred embodiments of the method and the device according to the invention, with claim 15 being directed to a system with two devices according to the invention connected in series. DESCRIPTION OF THE INVENTION

[0009] In the inventive method for inline quality control of continuously produced and conveyed continuous fiber composite semi-finished products, the fiber composite semi-finished product is supported in a first direction of a test axis extending transversely to the conveying direction in two first support areas, which have a first support spacing in the conveying direction. In a second direction of the test axis extending transversely to the conveying direction, opposite to the first direction, the fiber composite semi-finished product is supported in a second support area, which is arranged in the conveying direction between the two first support areas.At least two different relative positions of the first support areas with respect to the second support area are alternately set by relocating at least one of the support areas along the test axis, in order to alternately induce at least two different bending stress states of the conveyed fiber composite semi-finished product. In these at least two different bending stress states, reaction forces of the fiber composite semi-finished product on the second support area in the second direction and / or on the first support areas in the first direction are measured. This allows, for example, the continuous determination of the Young's modulus during the manufacturing of the fiber composite semi-finished product. In particular, if the measured actual values ​​deviate from a corresponding target value, immediate adjustment of manufacturing parameters can be made to ensure quality.Furthermore, a test report can be created and issued directly for the manufactured and inspected fiber composite semi-finished product, i.e., a test report that refers directly to this fiber composite semi-finished product and not to a sample taken destructively from it.

[0010] The measurement in the inventive method is carried out analogously to a 3-point bending test, but with continuously conveyed fiber composite semi-finished product.

[0011] In the method according to the invention, it is preferred if at least one of the support areas is continuously and periodically displaced, for example according to a sine function. If the reaction forces are then measured with such time resolution that a phase shift of the reaction forces relative to the displacement can be detected, a loss modulus of the fiber composite semi-finished product in the direction of the test axis can, for example, be determined, and thus the manufacturing of the fiber composite semi-finished product can be controlled even more thoroughly.

[0012] The periodic deflection of the fiber composite semi-finished product can be used as a forced vibration for structural health monitoring. Particularly large phase shifts between the displacements and the reaction forces occur near the natural frequencies of the bending vibration of the fiber composite semi-finished product between the first support area along the test axis. These phase shifts are strongly dependent on the difference between the excitation frequency and the natural frequency of the bending vibration. This means that variations in the material property natural frequency, in the form of the resulting changes in phase shift, can be detected particularly sensitively at excitations close to the natural frequency.Therefore, it is advantageous if the frequency of the periodic displacement in the method according to the invention is between 0.5 times and 1.5 times the natural frequency of the bending vibration of the fiber composite semi-finished product between the first support areas along the test axis.

[0013] Alternatively or additionally, the at least one support area along the test axis can be periodically shifted at a frequency such that the ratio of the conveying speed of the fiber composite semi-finished product in the conveying direction divided by the frequency is between 0.01 mm or 0.1 mm and 1 mm or 10 mm. This ratio indicates the sampling rate at which the Young's modulus of the fiber composite semi-finished product is determined by the bending test along its main extension direction. This sampling rate is typically in the range of 0.01 mm to 10 mm and preferably in the range of 0.1 mm to 1 mm. When a range of the type “between 0.01 mm or 0.1 mm and 1 mm or 10 mm” is specified here and in the following, including the patent claims, this is intended to mean that although the preferred range is between 0.1 mm and 1 mm, further ranges favorable for defining the invention lie between 0.01 mm and 1 mm and between 0.1 mm and 10 mm.

[0014] Regarding the amplitude of the displacement of at least one of the support areas along the test axis, it is advantageous if, in the bending load condition with the highest bending load, the edge fiber strain of the fiber composite semi-finished product in a plane spanned by the test axis and the conveying direction is between 0.05% and 2%, preferably between 0.3% and 2%. Depending on the fiber composite semi-finished product, this results in different amplitudes of the reaction forces. The edge fiber strain in the specified range ensures that the deflection of the fiber composite semi-finished product is sufficient for an accurately accurate measurement, but that neither the fiber composite semi-finished product is overstressed nor its production and conveying are unduly disrupted.

[0015] In the inventive method, the first support spacing of the first support areas is between 3 and 1,000 times, and preferably between 15 and 100 times, the material thickness of the fiber composite semi-finished product along the test axis. The second support area is preferably arranged centrally between the first support areas, so that the second support spacing of the second support area to the two first support areas is equal.

[0016] The first support distance between the two first support areas and also the two second support distances can be varied in the inventive method for optimal adaptation to a specific fiber composite semi-finished product.

[0017] The method according to the invention can be carried out for at least two different test axes oriented at an angle between 30° and 90°, preferably at an angle between 45° and 90° to each other. This allows for even more thorough quality control of the continuously produced fiber composite semi-finished product.

[0018] A device according to the invention is suitable for recording the material properties of virtually any continuous test material conveyed in a conveying direction. It comprises first support devices designed to support the test material in a first direction along a test axis extending transversely to the conveying direction in two first support areas. These first support areas have a first support spacing in the conveying direction. Second support devices of the device are designed to support the test material in a second direction opposite to the first direction along the test axis extending transversely to the conveying direction in a second support area. This second support area is arranged between the two first support areas in the conveying direction.The displacement mechanism of the device according to the invention is designed for alternately setting at least two different relative positions of the first support areas with respect to the second support area by displacing at least one of the support areas along the test axis, in order to alternately bring about at least two different bending stress states of the conveyed test specimen. Measuring devices of the device are designed for measuring reaction forces of the fiber composite semi-finished product in the second direction on the first section area and / or in the first direction on the first support areas in the at least two different bending stress states.

[0019] Preferably, the displacement devices are designed to continuously and periodically displace at least one of the support areas along the test axis, for example according to a sine function. The measuring devices are then designed to measure the reaction forces with time resolution and to detect any phase shift of the reaction forces relative to the displacement.

[0020] The support devices can have at least one support roller in each of the support areas. In addition to the support roller, the support devices can also have a pressure roller, whereby the test specimen can be guided between the support roller and the pressure roller. In this way, dynamic lifting of the test specimen from the support roller can be prevented. Such a pressure roller can also be provided for only some of the support rollers of the support devices.

[0021] The support rollers are rotatably mounted about axes of rotation parallel to each other and perpendicular to the conveying direction. The diameter of the support rollers typically ranges from 5 mm to 300 mm, preferably from 10 mm to 100 mm.

[0022] The displacement devices can be specifically designed to displace the two first support areas together along the test axis, i.e., in the first and second directions, relative to a base of the device. The measuring devices can be designed to measure the reaction forces on the second support area in the second direction. Alternatively, the displacement device can be designed to displace the second support area in both the first and second directions, and the measuring device can be designed to measure the reaction forces on one or both of the first support areas in the first direction. Furthermore, it is possible for the displacement devices to displace the same support area in both the first and second directions on which the measuring devices measure the reaction forces in the corresponding opposite directions.

[0023] Second support distances of the second support area to the two first support areas are preferably equal and each is between 10 mm and 500 mm, preferably between 20 mm and 200 mm.

[0024] A system according to the invention can have two or more devices according to the invention connected one after the other in the conveying direction, the test axes of which are oriented at an angle between 30° and 90°, preferably between 45° and 90° to each other.

[0025] It is also possible to mount the support devices, the displacement devices, and the measuring devices rotatably relative to a base of the device according to the invention in order to vary the orientation of the test axis. The fact that it can also be advantageous if the first support distance and, correspondingly, the second support distances are variable has already been mentioned in connection with the method according to the invention.

[0026] Advantageous further developments of the invention result from the patent claims, the description and the drawings.

[0027] The advantages of features and combinations of features mentioned in the description are merely exemplary and can have an effect alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0028] Regarding the disclosure content—not the scope of protection—of the original application documents and the patent, the following applies: Further features can be derived from the drawings—in particular, the geometries depicted and the relative dimensions of several components to one another, as well as their relative arrangement and functional connection. The combination of features from different embodiments of the invention or from features of different claims is also possible, deviating from the chosen cross-references of the claims, and is hereby encouraged. This also applies to features that are illustrated in separate drawings or mentioned in their description. These features can also be combined with features from different claims.Likewise, features listed in the patent claims may be omitted for further embodiments of the invention, but this does not apply to the independent patent claims of the granted patent.

[0029] The features mentioned in the claims and the description are to be understood, with regard to their number, as meaning that exactly that number or a greater number than the stated number is present, without the need for the explicit use of the adverb "at least". Thus, for example, if a support roller is mentioned, this is to be understood as meaning that exactly one support roller, two support rollers, or more support rollers are present. The features listed in the claims may be supplemented by further features or may be the only features that the subject matter of the respective claim possesses.

[0030] The reference numerals contained in the patent claims do not constitute a limitation of the scope of the subject matter protected by the patent claims. They merely serve the purpose of making the patent claims easier to understand. BRIEF DESCRIPTION OF THE FIGURES

[0031] The invention will now be further explained and described with reference to preferred embodiments shown in the figures. Fig. Figure 1 schematically shows a device according to the invention for carrying out a method according to the invention; and Fig. Figure 2 is a cross-section through a fiber composite semi-finished product, the production of which can be monitored using the method according to the invention. FIGURE DESCRIPTION

[0032] The in Fig. A schematically depicted device 1 serves to record the material properties of a continuous test specimen 3 conveyed in a conveying direction 2. The test specimen 3 is, for example, a fiber composite semi-finished product 4, on which a method for inline quality control is carried out with the device 1 directly after its production in order to immediately modify the production process in the event of undesirable deviations in quality from a specification. In principle, the test specimen 3 can also be any other quasi-continuous test specimen 3 conveyed in the conveying direction 2, for example, a wire, an extruded profile, a rolled web material, or an extruded web material.

[0033] The device 1 records the material properties of the test specimen 3 in a test axis 5. The device 1 has first support devices 6, which are designed to support the test specimen 3 in a first direction 7 of the test axis 5, which extends transversely to the conveying direction 2, in two first support areas 8. In each of the two support areas 8, the first support devices 6 have a support roller 9. The two support rollers 9 are rotatably mounted on a bracket 11 about axes of rotation 10 that are parallel to each other and transverse to the conveying direction 2. Second support devices 12 are designed to support the test specimen 3 in a second direction 13, opposite to the first direction 7, in a second support area 14. The second support devices 12 have a support roller 15 for this purpose. The support roller 15 is rotatably mounted about an axis of rotation 16, which extends parallel to the axes of rotation 10.

[0034] The device 1 further comprises displacement devices 17 for displacing the support 11, and thus the first support areas 8, relative to a base 22 of the device 1 and thus relative to the second support area 14 along the test axis 5. The displacement is carried out in the direction of a double arrow 21 with the aim of alternately inducing at least two different bending stress states of the test specimen 3 between support areas 8 and 14. Measuring devices 18, supported at the base 22, measure reaction forces of the fiber composite semi-finished product in the second direction 13 on the second support area 14 in the different bending stress states. The measuring devices 18 are designed such that measuring the reaction forces on the support roller 15 does not require any significant displacement of the axis of rotation 16.Rather, the axis of rotation 16 is essentially stationary relative to the base 22 of the device 1, relative to which the displacement devices 17 displace the support 11.

[0035] Further measuring devices can, for example, continuously measure the path by which the displacement devices 17 move the support 11 and thus the first support areas 8 relative to the base 22 using a laser distance meter. Preferably, the displacement devices 17 move the first support areas 8 continuously and periodically, in particular according to a sinusoidal function, and the measuring devices 18 measure the displacements and the resulting reaction forces with time resolution in order to detect any phase shifts occurring in between. In this way, the device 1 can be used, in particular, to determine the Young's modulus and the loss moduli of the test specimen 3 in the direction of the test axis 5.

[0036] Fig. Figure 2 shows a section through a test specimen 3 in the form of a fiber composite semi-finished product 4. The fiber composite semi-finished product 4 has a matrix 19 made of a plastic with continuous reinforcing fibers 20 embedded therein. A possible path of the test axis 5 is shown. Several devices 1 can also be used according to Fig. 1 can be connected in series to, for example, record the material properties of the test specimen 3 in two orthogonal test axes 5. REFERENCE MARK LIST 1 Device 2 Direction of conveyance 3 Test items 4 Fiber composite semi-finished products 5 test axes 6 first support devices 7 first direction 8 first support area 9 Support roller 10 Rotation axis 11 bracket 12 second support devices 13 second direction 14 second support area 15 Support roller 16 axis of rotation 17 relocation facilities 18 measuring devices 19 Matrix 20 reinforcing fibers 21 Double Arrow 22 base

Claims

[1] Method for inline control of the quality of continuously produced and conveyed in a conveying direction (2) coherent fiber composite semi-finished product (4) as test material (3) with the steps - supporting the fiber composite semi-finished product (4) in a first direction (7) of a test axis (5) running transversely to the conveying direction (2) in two first support areas (8) which have a first support distance in the conveying direction (2), - supporting the fiber composite semi-finished product (4) in a second direction (13) of the test axis (5) running transversely to the conveying direction (2) opposite to the first direction (7) in a second support region (14) which is arranged in the conveying direction (2) between the two first support regions (8), - alternately adjusting at least two different relative positions of the first support regions (8) relative to the second support region (14) by displacing at least one of the support regions (8, 14) along the test axis (5) in order to alternately bring about at least two different bending load states of the conveyed fiber composite semi-finished product (4), and - measuring reaction forces of the fiber composite semi-finished product (4) in the second direction (13) on the second support region (14) and / or in the first direction (7) on the first support regions (8) in the at least two different bending load states. [2] Method according to claim 1, wherein the at least one of the support regions (8, 14) is continuously and periodically displaced along the test axis (5). [3] The method of claim 2, wherein the reaction forces are measured in a time-resolved manner to detect a phase shift relative to the displacement. [4] Method according to claim 2 or 3, wherein the at least one of the support regions (8, 14) is periodically displaced along the test axis (5) at a frequency which is between 0.5 times and 1.5 times a natural frequency of a bending vibration of the fiber composite semi-finished product (4) between the first support regions (8) along the test axis (5). [5] Method according to one of claims 2 to 4, wherein the at least one of the support regions (8, 14) is periodically displaced along the test axis (5) at a frequency such that a quotient of a conveying speed of the fiber composite semi-finished product (4) in the conveying direction (2) divided by the frequency is between 0.01 mm or 0.1 mm and 1 mm or 10 mm. [6] Method according to one of the preceding claims, wherein the at least one of the support regions (8, 14) is displaced along the test axis (5) such that in the bending load state with the greatest bending load, an edge fiber elongation of the fiber composite semi-finished product (4) in a plane spanned by the test axis (5) and the conveying direction (2) results between 0.05% or 0.3% and 2%. [7] Method according to one of the preceding claims, wherein the first support distance is between 3 times or 15 times and 100 times or 1000 times a material thickness of the fiber composite semi-finished product (4) along the test axis (5). [8] Method according to one of the preceding claims, wherein second support distances of the second support region (14) to the two first support regions (8) are equal. [9] Method according to one of the preceding claims, wherein the steps are carried out for at least two different test axes (5) which are oriented at an angle between 30° or 45° and 90° to each other. [10] Device (1) for detecting material properties of a coherent fiber composite semi-finished product (4) conveyed in a conveying direction (2) as a test material (3) with - first support devices (6) which are designed to support the test material (3) in a first direction (7) of a test axis (5) extending transversely to the conveying direction (2) in two first support regions (8), wherein the first support regions (8) have a first support distance in the conveying direction (2), - second support devices (12) which are designed to support the test material (3) in a second direction (13) of the test axis (5) running transversely to the conveying direction (2) in a second support region (14) opposite to the first direction (7), wherein the second support region (14) is arranged between the two first support regions (8) in the conveying direction (2), - displacement devices (17) which are designed to alternately adjust at least two different relative positions of the first support regions (8) relative to the second support region (14) by displacing at least one of the support regions (8, 14) along the test axis (5) in order to alternately bring about at least two different bending load states of the conveyed test material (3), and - measuring devices (18) which are designed to measure reaction forces of the test material (3) in the second direction (13) on the second support region (14) and / or in the first direction (7) on the first support regions (8) in the at least two different bending load states. [11] Device (1) according to claim 10, wherein the displacement devices (17) are designed to continuously and periodically displace the at least one of the support regions (8, 14) along the test axis (5), and wherein the measuring devices (18) are designed to measure the reaction forces in a time-resolved manner and to detect a phase shift of the reaction forces with respect to the displacement. [12] Device (1) according to claim 10 or 11, wherein the support devices (6, 12) in each of the support areas (8, 14) have at least one support roller (9, 15), wherein the support rollers (9, 15) are rotatably mounted about axes of rotation (10, 16) parallel to one another and extending transversely to the conveying direction (2), and wherein diameters of the support rollers (9, 15) are between 5 mm or 10 mm and 100 mm or 300 mm. [13] Device (1) according to one of claims 10 to 12, wherein the displacement devices (17) are designed to displace the two first support regions (8) together in the first and second directions (13), and wherein the measuring devices (18) are designed to measure the reaction forces on the second support region (14) in the second direction (13). [14] Device (1) according to one of claims 10 to 13, wherein second support distances of the second support region (14) to the two first support regions (8) are equal and are each between 10 mm or 20 mm and 200 mm or 500 mm. [15] System with two devices (1) according to one of claims 10 to 14 connected one after the other in the conveying direction (2), wherein their test axes (5) are oriented at an angle between 30° or 45° and 90° to each other.

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