Method of repairing composite material element

Abstract

A method of repairing a composite material element (100), the method comprising, upon detecting an internal damaged area (101) within the composite material element (100), injecting a resin (300) into the internal damaged area (101) of the composite material element (100) wherein the method further comprises drilling at least one first non-through hole (200a) and at least one second non-through hole (200b) in the composite material element (100), each non-through hole (200) extends from one face of the composite material element (100) to the internal damaged area (101); and applying a vacuum at the at least one second non-through hole (200b), injecting a resin (300) from the at least one first non-through hole (200a) until the resin (300) at least fills the internal damaged area (101) of the composite material element (100).

Description

Technical Field

[0001] The present invention relates to a method for repairing composite material components, and is particularly applicable to repairing aircraft parts or components made of thermosetting composite materials. The method aims to repair damaged structural parts or components of an aircraft, and allows the mechanical strength of such parts or components to be restored to its initial design requirements.

[0002] The present invention is preferably applicable to the field of manufacturing and maintenance of composite parts / components for transportation applications (such as aircraft). Background Art

[0003] Composite materials forming parts or components of an aircraft often suffer internal damage for various reasons (such as collision with an object).

[0004] These internal damages cannot be detected by visual inspection of the aircraft. However, internal cracks or damages can be detected by non-destructive methods such as ultrasonic inspection methods.

[0005] Internal cracks or damages in composite components of an aircraft may have an impact on structural performance. Therefore, it is crucial to detect and repair these internal damages.

[0006] Currently, adhesive repair involves using grinding or milling processes to machine damaged plies in the area by stepping or scarfing the surface around the damaged part. The step length is usually between 8 and 12 millimeters, and the scarf ratio is usually less than 1:20. Repair patches can be applied to the parent structure using wet lay-up repair, thermo-bonding repair, or pre-cured patch repair methods.

[0007] Wet lay-up repair includes impregnating dry fiber fabrics with laminating resin and then applying them to the cured composite component.

[0008] Thermo-bonding repair is to perform adhesive repair using repair prepreg composite materials and adhesive films.

[0009] For wet lay-up and thermo-bonding scarf repairs, the repair plies are cut to precise dimensions to install the repair laminate, while achieving a defined overlap length in contact with the original laminate along the stepped or scarfed surface. This overlap length is usually about 8 - 12 millimeters.

[0010] In these methods, a curing cycle is applied to cure the repair material. In addition, vacuum pressure must be applied through a vacuum bag to consolidate the repair.

[0011] Heat bonding and wet layup repairs are widely used by airlines for the repair of thermoset composite parts. However, the prepreg composite repair materials used for heat bonding repairs need to be stored under specific temperature conditions and have a limited shelf life, which is considered a major drawback of this repair method. In addition, for wet layup repairs, it may be difficult to control the ratio of the different components used to prepare the repair resin and the impregnation ratio of the dry fibers. Moreover, in most applications, due to the differences in the fiber and resin materials and the curing process of the repair material compared to the parent material, the material properties of the repair material are generally lower than those of the part to be repaired.

[0012] Another drawback of current bonding repair methods (heat bonding and wet layup repairs) is the long time associated with completing the bonding repair. The machining of the damaged plies is the most time-consuming stage and there is a risk of creating new damage. Another time-consuming step is related to the strict repair ply preparation procedures. In addition, the positioning of the uncured plies must be precise to achieve a minimum overlap along the ply edges. Summary of the Invention

[0013] To provide a solution to the above problems, the present invention relates to a method for repairing a composite material element.

[0014] The method for repairing a composite material element (or component) includes, after detecting an internal damage area (such as porosity or material delamination) within the composite material element, injecting a resin into the internal damage area of the composite material element.

[0015] In a novel manner, the method for repairing a composite material element (or component) includes:

[0016] drilling at least one first non-through hole (preferably having a small diameter, such as about 2 mm) and at least one second non-through hole (preferably having a small diameter, such as about 2 mm) in the composite material element, each non-through hole extending from one side of the composite material element to (at least) the internal damage area; and

[0017] applying a vacuum at at least one second non-through hole and injecting resin from at least one first non-through hole until the resin fills at least a portion of the internal damage area of the composite material element. Preferably, the injected resin fills both the internal damage area and the non-through holes.

[0018] The vacuum loading can be applied continuously at a constant value or in an alternating impulse mode (e.g., the "on" and "off" vacuum can be implemented at a given frequency).

[0019] Thanks to the above method, no machining operations need to be performed on the composite material element or component to be repaired. The load-bearing capacity of the composite material element is restored by means of resin injection, and the resin injection is applied by injecting resin through non-through holes (non-penetrating holes), thereby reducing the structural impact of these holes on the structural integrity and load-bearing capacity of the composite material element.

[0020] The method for repairing a composite material element (or component) may include: heating the resin before injecting the resin into the internal damaged area of the composite material element. This operation can reduce the viscosity value of the resin, thereby facilitating the injection process.

[0021] The method for repairing a composite material element (or component) may include: injecting a structural resin into the internal damaged area of the composite material element. The structural resin may be, for example, a two-component epoxy resin such as EPOCAST This feature ensures that most of the load-bearing capacity of the composite material element is restored after the resin injection.

[0022] According to a preferred embodiment of the present invention, the method for repairing a composite material element includes, after injecting resin into the internal damaged area of the composite material element, bonding a repair patch to at least one side (or surface) of the composite material element, and the repair patch includes at least one pre-cured composite material reinforcement ply.

[0023] This feature allows for a higher load-bearing capacity in the case where the resin injection fails to fully restore the full strength of the panel of the composite material element. In addition, since the resin injection will partially or fully restore the mechanical strength of the composite part, using pre-cured reinforcement plies when needed will restore the full component strength with a smaller number of plies (compared to other traditional repair methods), because they are pre-cured plies rather than wet lay-up or thermally bonded repair plies.

[0024] The repair patch may include a plurality of pre-cured reinforcement plies bonded to each other through an adhesive layer.

[0025] An adhesive is used between the pre-cured plies to build the entire patch laminate. The adhesive layer cures simultaneously with the injected resin curing. Thus, the curing of the adhesive and the injected resin is obtained in a "single curing cycle".

[0026] The repair patch may further include an adhesive film located on one side of the repair patch, and the repair patch is configured to adhere to the composite material element (or component).

[0027] The repair patch may include at least one peel ply, and the peel ply is configured to protect at least one side of the pre-cured reinforcement ply.

[0028] Accordingly, a method of repairing a composite material element (or component) may include removing the at least one peel ply from one side of a repair patch before attaching the repair patch to at least one side of the composite material element.

[0029] According to an embodiment of the present invention, each reinforcing prepreg ply of the repair patch is made of the same composite material as the composite material element (or component). In this case, the repair method of the present invention can reuse the scraps (scrapped parts, waste materials, offcuts) of other composite material elements. The repair ply is pre-cured in an autoclave.

[0030] The method may further include smoothing the edges of the repair patch and the transition surface between the repair patch and the repaired composite material element by means of an aerodynamic smoothing material. That is, the method may include smoothing the transition edges between different prepreg plies of the repair patch by using an aerodynamic smoothing material. This feature allows the transition surface between the repair patch and the surface of the repaired composite material element to be smoothed.

[0031] At least one first non-through hole and at least one second non-through hole may extend from the same side of the composite material element to at least the internal damaged area. This embodiment allows for the repair of a composite material element that can only be accessed on one of its sides.

[0032] Conversely, in an alternative embodiment of the method of the present invention, at least one first non-through hole extends from a first side of the composite material element to at least the internal damaged area, while at least one second non-through hole extends from a second side of the composite material element to at least the internal damaged area. This embodiment allows resin to be injected on one side of the composite material element and a vacuum to be applied on the other side of the composite material element. Thus, it facilitates the injection of resin when both sides are accessible for the repair method.

[0033] According to the embodiments mentioned in the previous paragraphs, there may be a possibility that each first non-through hole and each second non-through hole are distributed in such a way that the projection of each first non-through hole on the second side of the composite material element does not coincide with the projection of any second non-through hole on the second side of the composite material element, and vice versa. Thus, the non-through holes are distributed such that the second non-through holes are not in front of the first non-through holes.

[0034] The new repair method of the present invention for adhesive repair aims to restore the mechanical strength of the repaired area, reduce the time and cost required to perform the adhesive repair, and the amount of materials used in the repair. This new method also helps to reduce the environmental footprint of the manufacture of parts made of thermosetting composite materials and to lower the supply and storage costs of the repair materials.

[0035] The novel repair patch for reinforced pre-cured laminates is easy to handle and enables an accurate overlap length of 8 to 12 mm. Since the damaged part is not removed by machining the surface, there is no scarf or step in the parent material or at the repair material interface. Surface smoothing can be carried out on the outer laminate to retain a more aerodynamic outer surface without steps.

[0036] The repair material can be the same as or have a similar grade and equivalent fibers and resin to the parent material. Thus, the material properties are equivalent to those of the parent structure.

[0037] It is also possible to select a repair material (pre-cured laminate) different from the original material. The advantage is that it can have a simple stock of pre-cured laminates, which can be used to repair any damaged monolithic parts.

[0038] The repair composite laminate is pre-cured at high temperature and high pressure in a controlled environment (i.e., cured in an autoclave), which means better consolidation of the resin and higher strength properties compared to curing only under vacuum pressure.

[0039] If not equipped with an adhesive layer, the pre-cured repair material has no limitation in terms of storage life.

[0040] The pre-cured composite panel laminates can be manufactured and supplied to users in standard sizes. This means that the composite pre-impregnated scrap material generated during the manufacturing process of composite parts can be reused, thus reducing the environmental footprint associated with the removal and disposal of waste.

[0041] There is no need to remove the damaged area.

[0042] Repair laminates with peel ply on both sides can be provided to prevent surface contamination and ensure that the required surface is ready for the bonding step.

[0043] Using reinforced pre-cured laminates provides a quick repair solution for repairs, offers flexibility and convenience in constructing the repair laminate sequence and achieving the correct positioning of the laminates.

[0044] Using resin injection to consolidate the damaged area reduces the number of reinforced pre-cured repair laminates required to restore the initial strength requirements of the structure.

[0045] The reinforced pre-cured laminates can be obtained from offcuts / laminates (i.e., the ends of the pre-impregnated rolls used in Automatic Tape Lay-up machines), which contributes to the sustainability and recyclability of materials and resources. Description of the Drawings

[0046] To better understand at least one embodiment of the present invention, the following drawings are introduced in a schematic and non-limiting manner.

[0047] Figure 1 : A schematic diagram showing a conventional scarf repair of a composite material element.

[0048] Figure 2 : A schematic diagram showing a composite material element with an internal damaged area.

[0049] Figure 3 : Shows Figure 3 of a composite material element, where a plurality of non-through holes are drilled from both sides of the composite material element until the internal damaged area is reached.

[0050] Figure 4 : Shows Figure 4 of a composite material element, where the internal damaged area and the non-through holes have been filled with resin.

[0051] Figure 5 : Shows Figure 5 of a composite material element, where a repair patch of a reinforced pre-cured ply has been attached to one side of the composite material element.

[0052] Figure 6 : A schematic side view showing a pre-cured repair ply. Peel plies can be added to both sides of the pre-cured ply to prevent surface contamination. Detailed Description of the Invention

[0053] As described above, the present invention relates to a method for repairing a composite material element 100. More specifically, the present invention relates to an adhesive repair method for composite material components.

[0054] Figure 1 A schematic diagram showing a composite material element 100 repaired by a conventional method, where both the damaged or cracked surface of the element 100 to be repaired and the contact surface 501 of the repair ply 500 have been machined or scarfed (e.g., using a grinding or milling process), and the repair ply 500 is cut to precise dimensions to allow the repair ply 500 to be attached to the element 100 to be repaired and achieve a defined overlap length between the contact surface 501 and the element 100 to be repaired along a stepped or scarfed contact surface 501.

[0055] Figures 2 to 5 Respectively show the consecutive stages of the repair method of the present invention.

[0056] As Figure 2As shown, when internal damage or cracks occur in the composite material element 100, a conflicting situation arises. Such damage or cracks involve at least one internal cavity of delaminated material being generated inside the composite material element 100.

[0057] The method includes: after detecting an internal damage area 101 or an internal crack in the composite material element 100 (or component) (e.g., by an ultrasonic detection method), drilling a plurality of non-through holes 200 from at least one side 102 (or surface) of the composite material element 100, and each non-through hole 200 extends from one side 102 (or surface) of the composite material element 100 to the internal damage area 101 (or internal crack area) inside the composite material element 100.

[0058] Figure 3 A plurality of non-through holes 200 drilled from each side 102 (or surface) of the composite material element 100 are shown.

[0059] As previously mentioned, the internal damage area 101 typically includes at least one internal cavity where the structure of the composite material has delaminated, forming areas of disbanding between the layers.

[0060] The holes drilled in the composite material element 100 to be repaired are non-through holes 200 (non-penetrating holes) with a small diameter (typically 2 mm in diameter) such that the integrity and structure of the composite material element 100 are not severely affected.

[0061] The method includes injecting resin 300 from at least one first non-through hole 200a and applying a vacuum from at least one second non-through hole 200b.

[0062] By means of the vacuum applied from at least one second non-through hole 200b, air is drawn out from the internal damage area 101, and the resin 300 flows in from at least one first non-through hole 200a, flooding the internal damage area 101 of the composite material element 100 until at least one second non-through hole 200b.

[0063] The vacuum can be applied continuously or in an impulse mode, that is, the vacuum is turned "on" and "off" at a given frequency.

[0064] Figure 4 The internal damage area 101 of the composite material element 100 filled with resin 300 and the non-through holes 200 are shown.

[0065] The resin 300 injected into the internal damage area 101 is a structural resin 300, such as a two-component epoxy resin, such as EPOCAST

[0066] Before injecting the resin 300 into the internal damaged area 101, the resin 300 can be heated to reach a minimum viscosity value, thereby facilitating its injection into the internal damaged area 101.

[0067] Once the resin 300 is injected into the internal damaged area 101 of the composite element 100 and once the resin 300 and the pre-cured ply are cured, the structural properties (resistance and load-bearing capacity) of the composite element 100 will be fully restored.

[0068] As Figure 5 shown, the method may further include adding a repair patch 400 made of at least one composite reinforced pre-cured ply 401 on one side (or surface) of the composite element 100.

[0069] The repair patch 400 may include a plurality of reinforced pre-cured plies 401 located on at least one side (or surface) of the composite element 100, and the pre-cured plies 401 overlap on top of the composite element 100.

[0070] The reinforced pre-cured ply 401 may be made of the same composite material as the element 100 (or component) to be repaired. The reinforced pre-cured ply 401 may be cured by the same curing process (e.g., by autoclave) as the composite (parent material) element 100 or component to be repaired.

[0071] When using a plurality of reinforced pre-cured plies 401, different reinforced pre-cured plies 401 may be bonded to each other by means of an adhesive layer. Different reinforced pre-cured plies 401 are pressed against each other by means of vacuum pressure, and a curing cycle is applied to the adhesive layer.

[0072] The reinforced pre-cured ply 401 can be obtained from scrap / laminates (i.e., the ends of the prepreg rolls used in the tape laying machine), which helps with the sustainability and recyclability of materials and resources.

[0073] Therefore, at least one reinforced pre-cured ply 401 forms a repair patch 400 on top of the element 100 to be repaired. Whether to use a single reinforced pre-cured ply 401 or a plurality of reinforced pre-cured plies 401 may depend on the number of damaged plies of the element 100 (composite component) to be repaired. The repair patch 400 with at least one reinforced pre-cured ply 401 forms at least one step or rung on the surface of the element 100. The thickness of each step depends on the material used for the pre-cured ply. The overlap of each step can vary from 8 to 12 millimeters.

[0074] The repair patch 400 includes an adhesive or a laminated resin film 403 on at least one of its surfaces (i.e., on one surface of the reinforcing pre-cured ply 401), such that the repair patch 400 is configured to adhere to the element 100 (or component) to be repaired.

[0075] The repair patch 400 may include a release ply 402 to protect the adhesive or the laminated resin film 403, as Figure 6 shown.

[0076] The method may further include using aerodynamic surface smoothing to smooth the edges of the repair patch 400 to achieve enhanced smoothness of the transition surface between the repair patch plies 401.

Claims

1. A method for repairing a composite material component (100), the method comprising: After detecting an internal damaged area (101) in the composite material component (100), injecting resin (300) into the internal damaged area (101) of the composite material component (100), wherein the method comprises: Drilling at least one first non-through hole (200a) and at least one second non-through hole (200b) in the composite material component (100), each non-through hole (200) extending from one side of the composite material component (100) to at least the internal damaged area (101); and A vacuum is applied at the at least one second non-through hole (200b), and the resin (300) is injected from the at least one first non-through hole (200a) until the resin (300) fills at least a portion of the inner damaged area (101) of the composite component (100).

2. The method for repairing a composite material component (100) according to claim 1, characterized in that: The method comprises heating the resin (300) before injecting the resin (300) into the internal damaged area (101) of the composite component (100).

3. The method for repairing a composite material component (100) according to claim 1 or 2, characterized in that: The resin (300) injected into the internal damaged area (101) of the composite component (100) is a structural resin (300).

4. The method for repairing a composite material component (100) according to claim 3, characterized in that: The resin (300) is a two-component epoxy resin.

5. Method for repairing a composite material element (100) according to any one of the preceding claims, characterized in that The method comprises: after injecting the resin (300) into the internal damaged area (101) of the composite component (100), bonding a repair patch (400) to at least one side of the composite component (100), the repair patch (400) comprising at least one composite reinforced pre-cured ply (401).

6. The method for repairing a composite material component (100) according to claim 5, characterized in that: The repair patch (400) comprises a plurality of reinforced pre-cured plies (401) bonded to each other by means of an adhesive layer.

7. The method for repairing a composite material component (100) according to claim 5 or 6, characterized in that: The repair patch (400) includes an adhesive film on one side of the repair patch (400), and the repair patch is configured to be adhered to the composite component (100).

8. A method for repairing a composite material element (100) according to any one of claims 5 to 7, characterized in that: The method includes: before attaching the repair patch (400) to at least one side of the composite component (100), removing at least one peel ply (402) from one side of the repair patch (400), the at least one peel ply (402) being configured to protect the at least one reinforcing pre-cured ply (401).

9. A method for repairing a composite material element (100) according to any one of claims 5 to 8, characterized in that: Each reinforced pre-cured ply (401) of the repair patch (400) is made of the same composite material as the element (100).

10. A method for repairing a composite material element (100) according to any one of claims 5 to 9, characterized in that: The method comprises: smoothing the edge of the repair patch (400) and the transition surface between the repair patch (400) and the repaired composite component (100) by means of an aerodynamic smoothing material.

11. Method for repairing a composite material element (100) according to any one of the preceding claims, characterized in that The at least one first non-through hole (200a) and the at least one second non-through hole (200b) both extend from the same face of the composite element (100) to at least the internal damaged region (101).

12. Method for repairing a composite material element (100) according to any one of claims 1 to 10, characterized in that: The at least one first non-through hole (200a) extends from the first side of the composite element (100) to at least the internal damaged area (101), and the at least one second non-through hole (200b) extends from the second side of the composite element (100) to at least the internal damaged area (101).

13. The method for repairing a composite material component (100) according to claim 12, characterized in that: Each first non-through hole (200a) and each second non-through hole (200b) are distributed in such a manner that a projection of each first non-through hole (200a) on the second surface of the composite element (100) does not overlap with a projection of any second non-through hole (200b) on the second surface of the composite element (100), and vice versa.

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