Machining method, application tool and machining arrangement for changing or repairing a surface area of ​​a workpiece surface of a fiber composite workpiece

Description

[0001] The invention relates to a machining method for modifying or repairing a surface area of ​​a workpiece surface of a fiber composite workpiece. The invention further relates to an application tool and a machining arrangement, each of which is used in the machining method.

[0002] During the assembly of monolithic fiber composite components, excessively deep holes / openings are a common occurrence. Currently used repair methods have long lead times, can require engineering decisions, and thus result in compromises that can be costly.

[0003] Typically, holes that are countersunk too deeply or otherwise not manufactured according to specifications are repaired by inserting a metal sleeve (e.g., made of titanium), heating the repair area, and using oversized bolts (compared to specifications). Alternatively, the holes are sometimes treated and repaired with resin (resin repair).

[0004] Furthermore, minor surface damage of a limited extent can also occur during the use of the fiber composite components, for example due to particle impact.

[0005] US 2019 / 061280A1 discloses a method for repairing damage to a composite component. First, an opening is created in the composite component. Then, resin-impregnated fibers are inserted through the opening, and their ends are spread radially on both sides. The resin is then cured.

[0006] US 2009 / 208691 A1 discloses a method according to the preamble of claim 1 for repairing structural components, in which sleeves are inserted into a previously enlarged hole. The passage created by the sleeves is not further machined.

[0007] US 5 928 448 A discloses a repair method for composites with a ceramic matrix.

[0008] DE 10 2015 101 328 A1 and DE 40 19 744 A1 disclose tools according to the preamble of claim 13 which are used in the repair of composite components.

[0009] US 2007 / 177330A1 discloses a method for repairing a copper grid for lightning protection.

[0010] The invention is based on the objective of creating an improved machining process and suitable devices for its implementation.

[0011] The problem is solved by the subject matter of the independent claims. Preferred further developments are the subject matter of the dependent claims.

[0012] The invention provides a machining method for modifying or repairing a surface area of ​​a workpiece surface of a fiber composite workpiece, wherein the surface area initially does not conform to a design specification and, after modification, conforms to the design specification, comprising the steps: 1.1 Lowering the surface area that is an initial bolt opening, wherein a contact surface and a recess are created by further lowering the initial bolt opening, and 1.2 Applying a fiber composite insert body to the contact surface and fixing the fiber composite insert body to the fiber composite workpiece in the recess, wherein the fiber composite insert body has a pilot opening for positioning and aligning the fiber composite insert body during application and / or fixing, and 1.3 Creating an end bolt opening in the fiber composite insert body according to the design specification, wherein the end bolt opening is created by enlarging the pilot opening.

[0013] It is preferred that, in particular in step 1.1, the contact surface is produced by means of conical countersinking, so that the contact surface has the shape of a conical lateral surface.

[0014] It is preferred that, in particular in step 1.1, the contact surface is generated by means of step sinks, so that the contact surface has the shape of a cylindrical surface.

[0015] It is preferred that, particularly in step 1.2, the positioning and / or fixing is carried out in such a way that the surface area is flat or flush with the workpiece surface.

[0016] It is preferred that, particularly in step 1.2, the fiber composite insert body is positioned concentrically with the recess due to its interaction with the contact surface.

[0017] It is preferred that the fiber composite insert body is conical or frustoconical in shape.

[0018] It is preferred that the fiber composite insert body is cylindrical in shape.

[0019] It is preferred that step 1.2 includes pressing the fiber composite insert body onto the fiber composite workpiece.

[0020] It is preferred that, in particular in step 1.2, the contact surface is cleaned to create an adhesive surface from the contact surface.

[0021] It is preferred that step 1.2 includes bonding the fiber composite insert body to the fiber composite workpiece, in particular at the bonding surface.

[0022] It is preferred that, particularly in step 1.2, the fiber composite insert body projects beyond the workpiece surface in the axial direction of the recess.

[0023] It is preferred that step 1.2 includes removing the fiber composite insert body until it is flat and / or flush with the workpiece surface.

[0024] It is preferred that the removal process is carried out in such a way that any coatings on the workpiece surface, particularly in the area surrounding the surface, are indeed captured, especially roughened, but not removed.

[0025] It is preferred that, particularly in step 1.2, the material removal is carried out by grinding.

[0026] It is preferred that a functional coating, in particular lightning protection materials, be restored after step 1.2 and, if applicable, preferably before step 1.3.

[0027] Preferably, the processing procedure includes the following step: Providing the fiber composite insert body by cutting the fiber composite insert body from a fiber composite body.

[0028] It is preferred that the cutting is carried out by drilling into the fiber composite body.

[0029] It is preferred that the fiber composite insert body is cut out in a conical or truncated conical shape.

[0030] It is preferred that the fiber composite insert body is cut out in a cylindrical shape.

[0031] It is preferred that the pilot opening is created during the cutting process.

[0032] It is preferred that the pilot hole is drilled during the cutting process.

[0033] It is preferred that the further lowered exit bolt opening forms the recess.

[0034] It is preferred that the initial bolt opening has an initial countersink depth and the end bolt opening has an end countersink depth, wherein the initial countersink depth and the end countersink depth are each defined relative to a workpiece surface of the fiber composite workpiece.

[0035] It is preferred that the machining process changes the initial countersinking depth to the final countersinking depth, in particular reduces it.

[0036] It is preferred that the machining procedure includes a step 1.4 which involves lowering the end bolt opening to the end countersinking depth.

[0037] It is preferred that, particularly in step 1.2, the fiber composite insert body is positioned concentrically with the exit bolt opening due to its interaction with the contact surface.

[0038] It is preferred that the pilot opening be designed as a through-hole or through-bore.

[0039] It is preferred that the pilot opening be designed as a blind hole or blind bore.

[0040] It is preferred that the pilot opening is positioned concentrically with the exit bolt opening due to the interaction of the fiber composite insert body with the contact surface.

[0041] It is preferred that the pilot opening is aligned parallel to the output bolt opening due to the interaction of the fiber composite insert body with the contact surface.

[0042] It is preferred that, in particular in step 1.3, the production is carried out by means of drilling, especially reaming.

[0043] It is preferred that, in particular in step 1.4, the end countersinking depth is selected such that a bolt intended for the initial bolt opening, which was not flush with the workpiece surface when this bolt was inserted in the initial bolt opening, is now flush with the workpiece surface, particularly within the permissible tolerances, when this bolt is inserted in the end bolt opening.

[0044] It is preferred that, particularly in step 1.2, the fiber composite insert body projects beyond the workpiece surface in the axial direction of the exit bolt opening.

[0045] It is preferred that step 1.2 includes removing the fiber composite insert body until it is flat and / or flush with the workpiece surface.

[0046] The invention therefore provides in particular a machining method for changing, in particular reducing, an initial countersink depth of an initial bolt opening, in particular for a round bolt, of a fiber composite workpiece, preferably designed for an aircraft component or an aircraft, to an end countersink depth of an end bolt opening, wherein the initial countersink depth and the end countersink depth are each defined relative to a workpiece surface of the fiber composite workpiece, comprising the steps: 1.1 Further lowering of the initial bolt opening to create a contact surface; 1.2 Placement of a fiber composite insert body against the contact surface and fixing the fiber composite insert body to the fiber composite workpiece; 1.3 Creation of the end bolt opening at least partially in the fiber composite insert body; and 1.4 Lowering of the end bolt opening to the final countersinking depth.

[0047] This processing method may preferably have one, several or all of the previously described preferred configurations.

[0048] The invention provides an application tool for positioning, aligning and / or pressing a fiber composite insert body onto an adhesive surface of a bolt opening of a fiber composite workpiece, wherein the application tool comprises a support frame designed for planar support of the application tool on a workpiece surface of the fiber composite workpiece, a guide bolt designed for positioning and aligning the fiber composite insert body when the guide bolt engages the fiber composite insert body, and a pressure device designed for applying a pressure force to the fiber composite insert body in the direction of the fiber composite workpiece.

[0049] The invention further provides a machining arrangement comprising a preferred application tool, a fiber composite insert body and a fiber composite workpiece with a recess, in particular a bolt opening, which has an adhesive surface, wherein the support frame engages the fiber composite workpiece, wherein the fiber composite insert body is engaged by the guide bolt in such a way that the fiber composite insert body is partially in the recess and concentric with the recess, wherein the fiber composite insert body is pressed onto the adhesive surface by the pressure device.

[0050] The fiber composite component is preferably used in aircraft components, for example, fuselage components. Its use in boat or vehicle construction, or in the wind energy sector, is also conceivable.

[0051] It should be noted that the numbering of procedural steps used herein is for ease of reference only and does not imply any order.

[0052] The advantages and effects of the methods and devices described herein are explained in more detail below. It should be noted that these advantages and effects do not limit the methods and devices to those described. Furthermore, not all advantages and effects need be realized in every embodiment of the invention.

[0053] This machining process allows for the correction of damage to a fiber composite workpiece (e.g., due to impact) by inserting a fiber composite insert into the damaged area after prior countersinking. This results in a fiber composite workpiece with a flat surface free of holes, bores, and / or countersinks.

[0054] The measures described herein allow the use of the bolts / fasteners nominally intended for the bolt hole even after machining or repairing it. The focus here is on changing or reducing the countersink depth of the bolt holes; in other words, correcting an initial countersink depth to a (desired) final countersink depth.

[0055] Furthermore, this method allows damage to be removed by introducing a countersink, for example a conical or stepped countersink, and the defective material to be replaced by the fiber composite insert.

[0056] The machining process described herein, also known as the cone repair process, can be designed to be so simple that a simple training course may be sufficient to reliably carry out the machining process according to the standards commonly used in aviation.

[0057] The fiber composite workpiece can, for example, be a prepreg material. The fiber composite body from which the fiber composite insert body can be cut out is preferably also a prepreg material.

[0058] Two-component adhesives, which may be epoxy-based, are preferably used to fix the fiber composite insert. The adhesive is preferably selected to allow for rapid curing at normal room temperature. Furthermore, the adhesive may be chosen based on its existing use in the manufacturing of other components, such as connecting clips for fiber composite structures. The standardized availability of the adhesive in prefabricated application devices, such as syringes, is also advantageous.

[0059] A dedicated tool can be used to cut out the fiber composite insert. It can be advantageous to first glue the preferably plate-shaped fiber composite to a substrate, for example made of wood, and only then cut out the fiber composite insert. Tests conducted by the applicant have shown that with such an arrangement, even microscopic surface examination revealed no damage to the material. In particular, no fiber breakout was visible from the cut surface, which only showed minor machining marks.

[0060] Separate cleaning of the fiber composite insert body, especially using an ultrasonic bath, has also proven advantageous.

[0061] Before the machining process, a deviation in the countersink depth may be detected, causing a bolt inserted into the bolt hole to sit too deep below the workpiece surface of the fiber composite workpiece. After removing the bolt, the existing countersink depth can then be increased (preferably by approximately 0.2 mm). The cut surface can then be thoroughly cleaned. Adhesive is applied to the cleaned cut surface. The adhesive can be applied to both parts, i.e., the fiber composite workpiece and the fiber composite insert. The fiber composite insert is inserted into the bolt hole and positioned / aligned. The adhesive cures at room temperature, i.e., without the application of additional heat (however, depending on the adhesive system, local heat treatment may be preferred or necessary). The adhesive is cured, for example, for 2 hours. The amount of adhesive is preferably oversized.

[0062] The fiber composite insert is preferably oversized so that it protrudes beyond the workpiece surface. In this case, the fiber composite insert can be ground down until it is flush with the workpiece surface. During grinding, care is preferably taken not to damage any functional coatings on the fiber composite workpiece. This could include a lightning protection material, for example, in the form of a metal mesh.

[0063] A hole is drilled into the fiber composite insert, or a pre-drilled opening is enlarged, so that the original bolt can be accommodated. Finally, the newly drilled hole is countersunk to the desired depth so that the bolt inserted into the hole is flush with the workpiece surface.

[0064] Tests conducted by the applicant, comparing the time required for the method described herein with the conventional method, have shown a significant time saving of approximately 7 hours – almost a full normal working day. If the method described herein is used instead of stock repair, the time saving can be considerably greater.

[0065] Optionally, one or more inspections can be carried out during processing.

[0066] With regard to the processing or application tool, the following advantages are preferably desired: Improving the perpendicularity of the bore axis of the existing cylinder hole relative to the workpiece surface; improving the perpendicularity of the pilot opening in the fiber composite insert body or fiber composite insert cone relative to the workpiece surface; improving the positioning of the cylinder hole area relative to the pilot opening in the fiber composite insert body or fiber composite insert cone; applying a certain pressure to the fiber composite insert body or fiber composite insert cone and the adhesive layer during curing in order to achieve the smallest possible adhesive line thickness and / or to close pores, especially those caused by an excessive amount of adhesive.

[0067] The tool can be manufactured using modern additive manufacturing methods or conventionally. Preferably, the support frame of the application tool is designed as a tripod.

[0068] It should be noted that the concept is explained here primarily using the example of repairing a bolt hole. However, the invention is not limited to this. Through holes can be used instead of blind holes, and vice versa. Furthermore, the countersinking is not limited to conical countersinks; stepped countersinks can also be used. In particular, suitable combinations of these measures can be employed depending on the application. Alternatively or additionally to the bolt hole, surface damage can also be repaired using the method described herein.

[0069] Examples of implementation are explained in more detail with reference to the attached schematic drawings. These show: Fig. 1 a cross-sectional view of an exit bolt opening; Fig. 2 a perspective view of the exit bolt opening; Fig. 3 a cross-sectional view of a further lowered exit bolt opening; Fig. 4 a perspective view of the further lowered exit bolt opening; Fig. 5 a cross-sectional view of the exit bolt opening with fiber composite insert body; Fig. 6 an embodiment of an application tool; Fig. 7 a detailed view of the fiber composite insert body made of Fig. 6 ; Fig. 8 another detailed view of the fiber composite insert body made of Fig. 6 Fig. 9 shows a view of the fiber composite insert body made of Fig. 6from below; Fig. 10 a cross-sectional view with removed fiber composite insert; Fig. 11 a perspective view of a fiber composite workpiece; Fig. 12 a perspective view of another fiber composite workpiece; Fig. 13 a cross-sectional view with inserted bolt; Fig. 14 a perspective view of a fiber composite workpiece; Fig. 15 a perspective view of a fiber composite workpiece made of Fig. 14 ; Fig. 15 a perspective view of a fiber composite workpiece made of Fig. 14 ; Fig. 16 a view relating to the cutting out of the fiber composite insert body; Fig. 17 a view of the in Fig. 16 extracted fiber composite insert body; and Fig. 18 an enlarged view of the cross-sectional area of ​​the extracted fiber composite insert body.

[0070] It will initially be on Fig. 1 and Fig. 2Reference is made to the figures showing a fiber composite workpiece 10. The fiber composite workpiece 10 can, for example, be part of an aircraft component, such as a fuselage panel or a fairing element.

[0071] The fiber composite workpiece 10 has a surface area 11 to be processed. This surface area 11 could, for example, be an exit bolt opening 12. It could also be damage to the fiber composite workpiece 10 caused by impact. The following examples illustrate this with the exit bolt opening 12. However, it is evident that the measures described herein are also suitable for damaged surface areas 11.

[0072] The fiber composite workpiece 10 has the exit bolt opening 12 for a bolt 14. The bolt 14 is, for example, a round bolt and may have a thread.

[0073] The exit bolt opening 12 has an exit countersink 16, for example in cylindrical form. The exit countersink 16 has an exit countersink depth 18. The exit countersink depth 18 is measured from a workpiece surface 20 of the fiber composite workpiece 10. The exit bolt opening 12 is shown here as a blind hole, but could also be a through hole or another type of hole.

[0074] Furthermore, the exit bolt opening 12 has a shaft area 22 for receiving a bolt shaft 24 of the bolt 14. The bolt 14 also includes a bolt head 26, which can be arranged in the exit recess 16.

[0075] As particularly in Fig. 1As can be seen, the bolt head 26 is positioned lower than the workpiece surface 20, so that the bolt 14 is not flush with the workpiece surface 20. The distance between the bolt 14 and the workpiece surface 20 is typically less than 1 mm, but more than the permissible tolerance. The bolt 14 therefore does not conform to a design specification.

[0076] In order to change the initial countersink depth 18 so that the bolt 14 is flush with the workpiece surface 20, the fiber composite workpiece 10 is machined as described below.

[0077] As in Fig. 3 and Fig. 4As shown, the initial bolt opening 12 is further countersunk using a countersink to create a conical countersink 28. The initial countersink 16 (or any damage thereto) can be completely removed. The cone angle is preferably between 90° and 130°. In particular, the cone angle is 100°. Other angles are possible depending on the application.

[0078] The conical countersinking also creates a contact surface 30 for a fiber composite insert body 32, preferably conical or frustoconical in shape. Preferably, the contact surface 30 is cleaned to obtain an adhesive surface 34.

[0079] Furthermore, the conical countersinking creates a recess 33 for the fiber composite insert body 32.

[0080] Then, resin material is applied as adhesive 35 to the bonding surface 34 and a outer surface 36 of the fiber composite insert body 32. The amount of adhesive 35 is preferably excessive to seal any pores on the bonding surface 34 or the outer surface 36. Furthermore, any trapped air bubbles can be carried out of the bonding area. The fiber composite insert body 32 is then, as shown in Figs. 5 to 7 The fiber composite insert body 32 is inserted into the exit bolt opening 12 and placed against the contact surface 30, in particular the adhesive surface 34. The fiber composite insert body 32 can have a pilot opening 38 for positioning and alignment. An application tool 40 can be used for this purpose.

[0081] The application tool 40 has a support frame 42. The support frame 42 is preferably designed as a tripod 44 and can be detachably attached to the fiber composite workpiece 10, for example by means of detachable adhesive connections 46. Vacuum suction cups or magnets can also be used for detachable attachment.

[0082] The application tool 40 further comprises a guide pin 48, which is vertically displaceable and supported on the support frame 40. The guide pin 48 can engage the fiber composite insert body 32 and engage in the pilot opening 38 in order to position the fiber composite insert body 32 concentrically to the exit pin opening 12 and / or align it parallel to the exit pin opening 12.

[0083] The application tool 40 can also have a pressure device 50 by means of which a force can be exerted in the axial direction of the fiber composite insert body 32 towards the fiber composite workpiece 10. In this case, the pressure device 50 comprises an elastic element 52, for example a coil spring 54, the force exerted by which can be adjusted by an adjusting element 56, for example a nut 58.

[0084] In particular, due to the interaction of the fiber composite insert body 32 with the contact surface 30, possibly with the aid of the application tool 40, the fiber composite insert body 32 can be positioned or aligned concentrically with and / or parallel to the exit bolt opening 12.

[0085] The result of this step is particularly evident in Fig. 8 and Fig. 9The fiber composite insert body 32 is preferably designed such that it projects beyond the workpiece surface 20 in the axial direction of the exit bolt opening 12. Furthermore, the excessive amount of adhesive 35 is visible.

[0086] The fiber composite insert body 32 is, as in Figs. 10 to 12 The material is removed, in particular ground down, until the fiber composite insert 32 is flush with the workpiece surface 20. Care is taken to ensure that any functional coating 60 is not removed during this process. The fiber composite inserts 32 are optionally provided with the functional coating 60 and thus integrated. Lightning protection material is one example of a functional coating 60.

[0087] As in Figs. 13 to 15As shown, the pilot opening 38 is enlarged, in particular drilled out, to create an end bolt opening 62. Due to the previously performed positioning and alignment, the end bolt opening 62 is also concentric and parallel to the initial bolt opening 12. It should be noted that this is also possible in principle without the pilot opening 38, but may require more skill.

[0088] The end bolt opening 62 is now countersunk to create an end countersink 64. The end countersink 64 has an end countersink depth 66 such that the bolt 14, when inserted into the end bolt opening, is flush with the workpiece surface 20.

[0089] The following will be based on Figs. 16 to 18 explains in more detail how the fiber composite insert body 32 can be manufactured.

[0090] First, a fiber composite body 68 can be provided, which is preferably made of the same material as the fiber composite workpiece 10.

[0091] A fiber composite cutting tool 70 is used to cut out the fiber composite insert body 32 from the fiber composite body 68. The fiber composite cutting tool 70 preferably has a central drill section 72 and a cutting head 74. During cutting, the drill section 72 forms the pilot opening 38, while the cutting head 74 forms the cylindrical surface 36 of the fiber composite insert body 32.

[0092] The fiber composite insert body 32 can be cleaned using an ultrasonic bath and then used.

[0093] In Fig. 18 The cut surface or surface 36 is shown in more detail. As can be seen, no fibers protrude from the cut surface and only minor machining marks are visible.

[0094] Therefore, to reduce the cycle time when repairing excessively deep countersunk bolt holes in fiber-reinforced composite workpieces, it is proposed to insert a fiber-reinforced composite insert into the excessively deep bolt hole. The insert is bonded to the fiber-reinforced composite workpiece. A new bolt hole is drilled into the insert and subsequently countersunk to the correct depth. A three-legged application tool can be used in this process to correctly position and align the fiber-reinforced composite insert and press it firmly against the fiber-reinforced composite workpiece while the adhesive cures.

[0095] The measures described herein can significantly reduce the processing or repair time for excessively deep-countersunk bolt holes in fiber composite workpieces – by almost up to 7 hours per bolt hole. Furthermore, the procedure is easy to learn and can therefore be reliably performed by more workers than before. Reference symbol list:

[0096] 10 Fiber composite workpiece 11 Surface area 12 Exit bolt opening 14 Bolt 16 Exit countersink 18 Exit countersink depth 20 Workpiece surface 22 Shank area 24 Bolt shank 26 Bolt head 28 Conical countersink 30 Contact surface 32 Fiber composite insert body 33 Recess 34 Adhesive surface 35 Adhesive 36 Sheath surface 38 Pilot opening 40 Application tool 42 Support frame 44 Tripod 46 Adhesive bond 48 Guide bolt 50 Pressure device 52 Elastic element 54 Coil spring 56 Adjustment element 58 Nut 60 Functional coating 62 End bolt opening 64 End countersink 66 End countersink depth 68 Fiber composite body 70 Fiber composite cutting tool 72 Drill section 74 Cutting head

Claims

1. Machining method for changing or repairing a surface location (11) of a workpiece surface (20) of a fibre-composite workpiece (10), wherein the surface location (11) initially does not correspond to a design specification, and corresponds to the design specification after the change, having the steps: 1.1 countersinking the surface location (11) which is an initial bolt opening (12), for creating a contact surface (30) and a depression (33), wherein the contact surface (30) is created by further countersinking of the initial bolt opening (12); 1.2 applying a fibre-composite insert body (32) to the contact surface (30), and fixing the fibre-composite insert body (32) to the fibre-composite workpiece (10) in the depression (33), wherein the fibre-composite insert body (32) has a pilot opening (38) for positioning and orienting the fibre-composite insert body (32) during applying and / or fixing; characterized in that the method comprises the following step: 1.3 creating a final bolt opening (62) in the fibre-composite insert body (32) according to the design specification, wherein the final bolt opening (62) is created by enlarging the pilot opening (38).

2. Machining method according to Claim 1, characterized in that, in step 1.2, the fibre-composite insert body (32) is positioned concentrically with the depression (33) due to the interaction with the contact surface (30).

3. Method according to either of the preceding claims, characterized in that step 1.2 comprises: - pressing the fibre-composite insert body (32) against the fibre-composite workpiece (10); and / or - adhesively bonding the fibre-composite insert body (32) to the fibre-composite workpiece (10).

4. Machining method according to one of the preceding claims, characterized in that, in step 1.2, the fibre-composite insert body (32) protrudes in the axial direction of the depression (33) beyond the workpiece surface (20), wherein step 1.2 comprises removing the fibre-composite insert body (32) until it is flat and / or flush with the workpiece surface (20).

5. Machining method according to Claim 4, characterized in that removing is carried out in such a way that any coatings (60) of the workpiece surface (20) are included, in particular roughened, but not removed.

6. Machining method according to Claim 4 or 5, characterized in that, in step 1.2, the removing is carried out by means of grinding.

7. Machining method according to one of the preceding claims, in that, after step 1.2 and, if present, preferably before step 1.3, a functional coating (60), in particular lightning protection materials, are restored.

8. Machining method according to one of the preceding claims, characterized by the step: - providing the fibre-composite insert body (32) by cutting out or by drilling out the fibre-composite insert body (32) from a fibre-composite body (68).

9. Machining method according to one of Claims 1 to 8, characterized in that, in step 1.2, - the fibre-composite insert body (32) is positioned concentrically with the initial bolt opening (12) due to the interaction with the contact surface (30); and / or - the pilot opening (38) is positioned concentrically with the initial bolt opening (12) and / or is oriented parallel to the initial bolt opening (12) due to the interaction of the fibre-composite insert body (32) with the contact surface (30); and / or - the fibre-composite insert body (32) protrudes in the axial direction of the initial bolt opening (12) beyond the workpiece surface (20), wherein step 1.2 comprises removing the fibre-composite insert body (32) until it is flush with the workpiece surface (20).

10. Machining method according to one of Claims 1 to 9, characterized in that, in step 1.3, creating takes place by means of drilling, in particular reaming.

11. Machining method according to one of Claims 1 to 10, characterized in that the initial bolt opening (12) has an initial countersunk depth (18) and the final bolt opening (62) has a final countersunk depth (66), wherein the initial countersunk depth (18) and the final countersunk depth (66) are each defined relative to a workpiece surface (20) of the fibre-composite workpiece (10), wherein the machining method changes, in particular reduces, the initial countersunk depth (18) to the final countersunk depth (66), and comprises a step 1.4 comprising countersinking the final bolt opening (62) to the final countersunk depth (66).

12. Machining method according to Claim 11, characterized in that, in step 1.4, the final countersunk depth (66) is selected such that a bolt (14), which is intended for the initial bolt opening (12) and was not flush with the workpiece surface (20) when this bolt (14) was inserted into the initial bolt opening (12), this bolt (14) is now flush with the workpiece surface (20), when this bolt (14) is inserted into the final bolt opening (62).

13. Application tool (40), in particular for use in a machining method according to one of the preceding claims, wherein the application tool (40) is designed for positioning, orienting and pressing a fibre-composite insert body (32) onto an adhesive surface (34) of a bolt opening (12) of a fibre-composite workpiece (10), wherein the application tool (40) comprises a support frame (42) which is designed for the flat support of the application tool (40) on a workpiece surface (20) of the fibre-composite workpiece (10), characterized in that the application tool comprises a guide bolt (48), which is designed for positioning and orienting the fibre-composite insert body (32) and which is supported vertically displaceably on the support frame (40), and a pressing device (50), which is designed for applying a pressing force to the fibre-composite insert body (32) in the direction of the fibre-composite workpiece (10), wherein the guide bolt (48) is designed to grasp the fibre-composite insert body (32) and to engage in the pilot opening (38) in such a way that the fibre-composite insert body (32) can be positioned concentrically to the initial bolt opening (12) and / or can be oriented parallel to the initial bolt opening (12).

14. Machining arrangement comprising an application tool (40) according to Claim 14, a fibre-composite insert body (32) and a fibre-composite workpiece (10) having a bolt opening (12) which has an adhesive surface (34), wherein the support frame (42) grasps the fibre-composite workpiece (10), wherein the fibre-composite insert body (32) is grasped by the guide bolt (48) such that the fibre-composite insert body (32) is arranged partially in the bolt opening (12) and concentrically with the bolt opening (12), wherein the fibre-composite insert body (32) is pressed by the pressing device (50) onto the adhesive surface (34).