Method for laying a strain gauge fiber

Abstract

To lay a strain gauge fiber (7), the strain gauge fiber (7) is pressed onto an adhesive side (8) of a carrier tape (10) of an adhesive tape (6) coated with the adhesive (9) and then laid on the surface (44) with the adhesive tape (6) and pressed onto the surface (44) so ​​that the strain gauge fiber (7) is fixed with the adhesive (9) between the adhesive tape (6) and the surface (44).

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to a method for laying a strain gauge fiber, wherein the strain gauge fiber is continuously deposited on a surface together with an adhesive and fixed to the surface with the adhesive. Furthermore, the invention relates to a device for carrying out such a method.

[0002] The strain gauge fiber is laid on the surface to measure surface deformations. The surface can be an external surface of an object of interest. It can also be an internal surface, such as a fiber composite part. Additional components of the fiber composite are then applied to the surface and bonded to the surface and the object containing the surface. STATE OF THE ART

[0003] A method of the type described above, which corresponds to the preamble of independent patent claim 1, is known from US 2015 / 0 129 126 A1. A strain gauge fiber is coated with thermoplastic resin and wound onto a spool of a supply reel. For application to the surface, the coated strain gauge fiber is unwound from the spool, guided between two guide rollers, its thermoplastic resin sheath is heated with a heating element, and then pressed onto the surface by a pressure roller rolling over the surface. The strain gauge fiber is fixed by means of the initially softened and then recurved thermoplastic resin.Coating the strain gauge fiber with thermoplastic resin is just as complex as heating the thermoplastic resin to the precise temperature required for the strain gauge fiber to be affixed to the surface after being pressed onto it with the pressure roller by the re-solidifying resin. In particular, varying deposition speeds at which the strain gauge fiber is deposited on the surface carry the risk of failing to achieve the desired fixation of the strain gauge fiber to the surface. OBJECT OF THE INVENTION

[0004] The invention is based on the object of demonstrating a method having the features of the preamble of independent patent claim 1, which can be carried out with little effort and yet securely fixes the strain gauge fiber to the surface even across different deposition speeds. SOLUTION

[0005] The object of the invention is achieved by a method having the features of independent patent claim 1. The subordinate patent claim 11 relates to a device for carrying out the method. The dependent patent claims relate to preferred embodiments of the method and the device. DESCRIPTION OF THE INVENTION

[0006] In a method according to the invention for laying a strain gauge fiber, wherein the strain gauge fiber is continuously laid on a surface together with adhesive and fixed to the surface with adhesive, the strain gauge fiber is first pressed onto an adhesive-coated adhesive side of a carrier tape of an adhesive tape and only then is it laid on the surface with the adhesive tape and pressed against the surface so that it is fixed with the adhesive between the adhesive tape and the surface. The method according to the invention does not involve the complex coating of the strain gauge fiber with a thermoplastic resin. Instead, an adhesive tape is used, which can in particular be a commercially available adhesive tape.The adhesive on the adhesive side of the adhesive tape's carrier tape is first used to fix the strain gauge fiber to the adhesive tape so that it can be placed on the surface in a defined manner using the adhesive and pressed against it. The same adhesive is then used to fix the strain gauge fiber to the surface by securing it between the adhesive tape and the surface. The large contact area between the adhesive tape and the surface guarantees reliable fixation, even though the strain gauge fiber itself is usually not directly bonded to the surface with the adhesive, but rather adheres to the carrier tape via the adhesive, which adheres to the surface on both sides of the strain gauge fiber via the adhesive.It is therefore clear that the strain gauge fiber is pressed onto the adhesive side of the carrier tape at a lateral distance from the edges, so that parts of the carrier tape are glued to the surface on both sides of the strain gauge fiber. Despite the fact that the strain gauge fiber is not directly bonded to the surface, the strain gauge fiber is sufficiently coupled to the surface to allow the strain gauge fiber to detect surface deformations. This is a quite surprising finding, one that was not expected.

[0007] For coupling the strain gauge fiber to the surface, it proves to be advantageous if the strain gauge fiber pressed against the adhesive side extends parallel to a main extension direction of the adhesive tape, so that strains in the carrier tape of the adhesive tape also affect strains in the strain gauge fiber.

[0008] To implement the method according to the invention, the adhesive tape can be unwound from a supply reel before the strain gauge fiber is pressed onto the adhesive side. The adhesive tape with the pressed-on strain gauge fiber can then be wound onto a reel. To press it onto the surface, the adhesive tape with the pressed-on strain gauge fiber can be unwound from the reel again. In detail, the strain gauge fiber can be pressed locally onto the rear-supported adhesive tape using a pressure roller and / or by longitudinal tension on the strain gauge fiber in order to bond the strain gauge fiber to the adhesive tape in a defined manner. The adhesive tape with the pressed-on strain gauge fiber can be wound onto the reel together with a release tape resting on the adhesive and the strain gauge fiber. This prevents the adhesive from unintentionally adhering to the side of the carrier tape opposite the adhesive side.

[0009] The strain gauge fiber can be placed on the surface together with the adhesive tape using a tape dispenser and pressed against it. A standard adhesive tape dispenser, which is normally used only for unrolling adhesive tape without a strain gauge fiber, can be used for this purpose. However, it is also possible to use a special adhesive tape dispenser, which, for example, uses a particularly soft pressure roller to press the adhesive tape onto the surface, into which the strain gauge fiber can be pressed without damaging it.

[0010] Together with the strain gauge fiber, another strain gauge fiber can be pressed onto the adhesive-coated side of the adhesive tape's backing strip. The tape can then be placed on the surface and pressed against it. In principle, more than two strain gauge fibers can be laid parallel to each other on the surface using the adhesive tape.

[0011] Preferably, the carrier tape of the adhesive tape is a woven carrier tape that is tensile in the longitudinal direction but deformable in the transverse direction in order to be able to lay the strain gauge fiber on the surface not only in straight lines and to still couple it well to the surface.

[0012] In particular, the woven, but also any other resin-permeable carrier tape, allows a resin to be applied to the carrier tape of the adhesive tape pressed against the surface in such a way that the resin penetrates the carrier tape all the way to the surface. When the resin is subsequently cured, it firmly couples the strain gauge fiber to the surface if the adhesive tape's adhesive is insufficient for this purpose.

[0013] The carrier tape and the strain gauge fiber can be integrated into a fiber composite formed on the surface with reinforcing fibers embedded in the resin. This fiber composite can be based, for example, on prepregs or preforms subsequently infiltrated with the resin. In any case, the resin should permeate the carrier tape all the way to the surface, thus surrounding the strain gauge fiber. This couples the strain gauge fiber and the surface to the plastic matrix of the fiber composite formed from the resin.

[0014] A device according to the invention for carrying out the method according to the invention has a first pivot bearing for a supply winding body from which an adhesive tape can be unwound, a second pivot bearing for a winding body onto which the adhesive tape unwound from the supply winding body can be wound together with a strain gauge fiber, a third pivot bearing for a coil body from which the strain gauge fiber can be unwound, a support element arranged between the first pivot bearing and the third pivot bearing on one side and the second pivot bearing on the other side for rearwardly supporting the adhesive tape when the strain gauge fiber is pressed onto an adhesive side of the adhesive tape, and a rotatably mounted guide roller arranged between the third pivot bearing on one side and the support element on the other side, said guide roller having a circumferential groove for laterally guiding the strain gauge fiber relative to the adhesive tape.By simply unwinding the adhesive tape and rewinding it after pressing the strain gauge fiber on, the adhesive tape with the strain gauge fiber can be prepared in wound form for placement on the surface using an adhesive tape dispenser.

[0015] The device according to the invention can include a rotary drive for the winding body and a rotary brake for the spool body. The unwinding of the adhesive tape from the supply winding body is generally sufficiently slowed by the adhesive of the adhesive tape.

[0016] Opposite the support element, a pressure roller can be positioned to press the strain gauge fiber against the adhesive side of the adhesive tape. It is understood that this pressure roller has a surface to which the adhesive of the adhesive tape adheres as little as possible.

[0017] The rotatably mounted guide roller can also have a further circumferential groove for laterally guiding another strain gauge fiber relative to the adhesive tape in order to press several strain gauge fibers parallel to one another onto the adhesive tape and then together with the adhesive tape onto a surface.

[0018] The additional strain gauge fiber can also be unwound from the coil body, or there is another pivot bearing for another coil body from which the additional strain gauge fiber can be unwound.

[0019] Advantageous further developments of the invention emerge from the patent claims, the description and the drawings.

[0020] The advantages of features and combinations of several features mentioned in the description are merely exemplary and can be effective alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0021] With regard to the disclosure content – ​​not the scope of protection – of the original application documents and the patent, the following applies: Further features can be found in the drawings – in particular the illustrated geometries and the relative dimensions of several components to one another, as well as their relative arrangement and operative connection. The combination of features of different embodiments of the invention or features of different patent claims is also possible, deviating from the chosen references of the patent 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 of different patent 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.

[0022] The number of features mentioned in the patent claims and the description is to be understood as meaning that exactly this 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 reference is made to one strain-gauge fiber, this is to be understood as meaning that exactly one strain-gauge fiber, two strain-gauge fibers, or more strain-gauge fibers are present. The features mentioned in the patent claims may be supplemented by further features or may be the only features present in the subject matter of the respective patent claim.

[0023] The reference signs contained in the patent claims do not represent a limitation of the scope of the subject-matter protected by the patent claims. They serve solely to make the patent claims easier to understand. BRIEF DESCRIPTION OF THE CHARACTERS

[0024] In the following, the invention is further explained and described with reference to preferred embodiments shown in the figures. Fig. 1 shows a device according to the invention when carrying out first steps of a method according to the invention in a side view. Fig. 2 shows the device according to Fig. 1 during the implementation of the first steps of the method according to the invention in a view from above. Fig. 3 shows the implementation of further steps of the method according to the invention with an adhesive tape dispenser in a side view and Fig. 4 shows the implementation of the steps according to Fig. 3 in a top view of the tape dispenser. Fig. 5 is a block diagram of the sequence of another embodiment of the method according to the invention. FIGURE DESCRIPTION

[0025] The Fig. 1 and Fig. The device 1 shown in Figure 2 has a frame 2 which is only shown schematically. A first pivot bearing 3 for a supply winding body 4 is supported on the frame 2, such that the supply winding body 4 is mounted on the frame 2 so that it can rotate about a first axis of rotation 5. An adhesive tape 6 is wound onto the supply winding body 4, which adhesive tape is unwound from the supply winding body 4 in the device 1 in order to press two strain measuring fibers 7 onto an adhesive side 9, coated with adhesive 8, of a carrier tape 10 of the adhesive tape 6, and to then wind the adhesive tape 6 with the pressed-on strain measuring fibers 7 back onto a winding body 11. A second pivot bearing 12 is supported on the frame 2 for the winding body 11, such that the winding body 11 can be rotated about a second axis of rotation 13 parallel to the first axis of rotation 5.A rotary drive 14 in the form of an electric motor 15 is provided for the winding body 11, which rotates the winding body 11 about the second rotational axis 13 to wind up the adhesive tape 6 with the strain gauge fibers 7 pressed onto it. The strain gauge fibers 7 are unwound from a spool body 16, for which a third pivot bearing 17 is supported on the frame 2, so that the spool body 16 can be rotated about a third rotational axis 18, which runs parallel to the first rotational axis 5 and the second rotational axis 13. A rotary brake 18 resists the rotation of the spool body 16. As a result, the strain gauge fibers 7 are subjected to tensile stress as they are unwound from the spool body 16. Between the first pivot bearing 3 and the third pivot bearing 17 on one side and the second pivot bearing 12 on the other side, a support element 20 in the form of a support roller 21 is supported for rearwardly supporting the adhesive tape 6 when pressing the strain gauge fibers 7 onto the frame 2.For this purpose, a fourth pivot bearing 22 with a fourth rotational axis 23 parallel to the other rotational axes 3, 12, and 18 is supported on the frame 2. A pressure roller 24 on the adhesive side 8 of the carrier tape 10 of the adhesive tape 6 is located opposite the support roller 21. The pressure roller presses the strain gauge fibers 7 against the adhesive 9 on the adhesive side 8. For this purpose, it is rotatably mounted in a fifth pivot bearing 25 with a fifth rotational axis 26 parallel to the other rotational axes 3, 12, 18, and 23. The fifth pivot bearing 25 is biased toward the support roller 21 by a spring 27. Between the third pivot bearing 17 on one side and the support element 20 on the other side, a guide roller 30 is provided, which is rotatably mounted on the frame 2 via a sixth pivot bearing 28 with a sixth axis of rotation 29 parallel to the other axes of rotation 3, 12, 18, 23 and 26, and has circumferential grooves 31 and 32 for laterally guiding the strain gauge fibers 7 relative to the adhesive tape 6.

[0026] The winding body 11 with the adhesive tape 6 wound on it with pressed-on strain gauge fibers 7 is removed from the device 1 and inserted into an adhesive tape dispenser, which is inserted into the Fig. 3 and Fig. 4 is shown schematically. The adhesive tape dispenser 33 has a seventh pivot bearing 34 in which the winding body 11 is mounted so as to be rotatable about a seventh axis of rotation 35. Further pivot bearings 36 and 37 are provided in order to mount a further pressure roller 38 and a further support roller 39 on the adhesive tape dispenser 3 so as to be rotatable about further axes of rotation 40 and 41. A handle 42 is provided for handling the adhesive tape dispenser 33. Using the adhesive tape dispenser 33, the adhesive tape 6, with in this case only one previously pressed-on strain gauge fiber 7, is placed on a surface 44 of a body 43 and then pressed against the surface 44 with the support roller 38 so that the strain gauge fiber 7 is fixed to the surface 44 under the adhesive tape 6. The adhesive tape 6 with the pressed-on strain gauge fiber 7 runs between the pressure roller 38 and the support roller 39.

[0027] Fig. 4 shows, on the left, a previously laid section of the adhesive tape 6, which fixes the section of the strain gauge fiber 7 to the surface 44. This fixation is indirect in that the adhesive 9 on the adhesive side 8 of the carrier tape 10 of the adhesive tape 6, on the one hand, bonds the measuring fiber 7 to the carrier tape 10 and, on the other hand, bonds the carrier tape 10 to the surface 44. However, the adhesive 8 can also be present in a certain excess, which leads to the strain gauge fiber 7 also being bonded directly to the surface 44.

[0028] Fig.5 provides an overview of one embodiment of the method according to the invention. The process begins with the unwinding 45 of the adhesive tape 6 from the supply winding body 4 and the unwinding 46 of one or more strain-gauging fibers 7 from the spool body 16. This is followed by the pressing 47 of the strain-gauging fiber(s) onto the adhesive side 8 of the carrier tape 10 of the adhesive tape 6. This is followed by the winding 48 of the adhesive tape 6 with the pressed-on strain-gauging fiber 7 onto the winding body 11. The rewinding 49 of the adhesive tape 6 with the pressed-on strain-gauging fiber 7 from the winding body 11 takes place in the adhesive tape dispenser 33. This is followed by the depositing / pressing 50 of the adhesive tape 6 with the strain-gauging fiber 7 onto the surface 44 using the pressure roller 38 in order to fix the strain-gauging fiber(s) 7 to the surface 44. This can be followed by covering 51 the adhesive tape 6 on the surface 44, for example with preforms or prepregs to form a fiber composite.During infiltration 52, resin for producing the fiber composite penetrates through the preferably woven carrier tape 10 of the adhesive tape 6 into the area of ​​the strain gauge fiber(s) on the surface 44. As the resin cures 53, this results in a plastic matrix of the fiber composite formed from the resin directly bonding the strain gauge fiber(s) to the surface 44. The impregnation of the carrier tape 10 with the resin and the subsequent curing 53 of the resin for directly bonding the strain gauge fiber(s) 7 to the surface 44 can also be performed without forming a fiber composite with additional reinforcing fibers on the surface 44. In any case, the cured resin ensures the firm coupling of the strain gauge fiber(s) 7 to the surface 44, even over extended periods. LIST OF REFERENCE SYMBOLS 1 device 2 frames 3 first pivot bearing 4 supply winding bodies 5 first axis of rotation 6 adhesive tape 7 strain gauge fiber 8 Adhesive side 9 Adhesive 10 carrier tape 11 winding bodies 12 second pivot bearing 13 second axis of rotation 14 Rotary drive 15 Electric motor 16 coil bodies 17 third pivot bearing 18 third axis of rotation 19 Rotary brake 20 support element 21 Support roller 22 fourth pivot bearing 23 fourth axis of rotation 24 Pressure roller 25 fifth pivot bearing 26 fifth axis of rotation 27 spring 28 sixth pivot bearing 29 sixth axis of rotation 30 Leadership role 31 circumferential groove 32 circumferential groove 33 tape dispensers 34 pivot bearings 35 seventh axis of rotation 36 additional pivot bearings 37 additional pivot bearing 38 additional pressure rollers 39 additional support rollers 40 additional rotation axes 41 additional rotation axis 42 Handle 43 bodies 44 Surface 45 by winding 46 Unwind 47 Press 48 Winding 49 Rewinding 50 Place / Press 51 Cover 52 Infiltrate 53 Curing QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 20150129126 A1

[0003]

Claims

[1] Method for laying a strain gauge fiber (7), wherein the strain gauge fiber (7) is continuously laid on a surface (44) together with adhesive (9) and fixed to the surface (44) with the adhesive (9), characterized by that the strain gauge fiber (7) is pressed onto an adhesive side (8) of a carrier tape (10) of an adhesive tape (6), coated with the adhesive (9), and is then placed on the surface (44) with the adhesive tape (6) and pressed onto the surface (44) so ​​that it is fixed with the adhesive (9) between the adhesive tape (6) and the surface (44). [2] Method according to claim 1, characterized by that the strain gauge fiber (7) pressed onto the adhesive side (8) extends parallel to a main extension direction of the adhesive tape (6). [3] Method according to claim 1 or 2, characterized bythat the adhesive tape (6) is unwound from a supply winding body (4) before the strain gauge fiber (7) is pressed onto the adhesive side (8), that the adhesive tape (6) with the pressed-on strain gauge fiber (7) is wound onto a winding body (11) and that the adhesive tape (6) with the pressed-on strain gauge fiber (7) is unwound again from the winding body (11) for pressing onto the surface (44). [4] Method according to claim 3, characterized by that the strain gauge fiber (7) is pressed locally onto the rear-supported adhesive tape (6) by means of a pressure roller (24) and / or by means of a longitudinal tension of the strain gauge fiber (7). [5] Method according to claim 3 or 4, characterized by that the adhesive tape (6) with the pressed-on strain gauge fiber (7) is wound onto the winding body (11) together with a separating tape lying on the adhesive (9) and the strain gauge fiber (7). [6] Method according to one of the preceding claims, characterized bythat the strain gauge fiber (7) with the adhesive tape (6) is placed on the surface (44) using an adhesive tape dispenser (33) and pressed onto the surface (44). [7] Method according to one of the preceding claims, characterized by that together with the strain gauge fiber (7) a further strain gauge fiber (7) is pressed onto the adhesive side (8) of the carrier tape (10) of the adhesive tape (6) coated with the adhesive (9) and is then placed on the surface (44) with the adhesive tape (6) and pressed onto the surface (44). [8] Method according to one of the preceding claims, characterized by that the carrier tape (10) is woven. [9] Method according to one of the preceding claims, characterized by that a resin is applied to the carrier tape (10) of the adhesive tape (6) pressed onto the surface (44), wherein the resin impregnates the carrier tape (10) up to the surface (44) and is then cured. [10] Method according to claim 9, characterized by that a fiber composite with reinforcing fibers embedded in the resin is formed on the surface (44) above the adhesive tape (6). [11] Device for carrying out the method according to one of the preceding claims with - a first pivot bearing (3) for a supply winding body (4) from which an adhesive tape (6) can be unwound, - a second pivot bearing (12) for a winding body (11) onto which the adhesive tape (6) unwound from the supply winding body (4) can be wound together with a strain gauge fiber (7), - a third pivot bearing (17) for a coil body (16) from which the strain gauge fiber (7) can be unwound, - a support element (20) arranged between the first pivot bearing (3) and the third pivot bearing (17) on one side and the second pivot bearing (12) on the other side for supporting the adhesive tape (6) from behind when the strain gauge fiber (7) is pressed onto an adhesive side (8) of the adhesive tape (6) and - a rotatably mounted guide roller (30) arranged between the third pivot bearing (17) on one side and the support element (20) on the other side, with a circumferential groove (31) for laterally guiding the strain gauge fiber (7) relative to the adhesive tape (6). [12] Device according to claim 9, characterized by that a rotary drive (14) for the winding body (11) and a rotary brake (19) for the coil body (16) are provided. [13] Device according to claim 9 or 10, characterized by that a pressure roller (24) for pressing the strain gauge fiber (7) onto the adhesive side (8) of the adhesive tape (6) is located opposite the support element (20). [14] Device according to claim 9, 10 or 11, characterized by that the rotatably mounted guide roller (30) has a further circumferential groove (32) for laterally guiding a further strain gauge fiber (7) relative to the adhesive tape (6). [15] Device according to claim 12, characterized by that the further strain gauge fiber (7) can also be unwound from the coil body (16) or that a further rotary bearing is provided for a further coil body from which the further strain gauge fiber (7) can be unwound.