CN113734462B

CN113734462B - Skin maintenance method for sports aircraft

Info

Publication number: CN113734462B
Application number: CN202110645978.3A
Authority: CN
Inventors: 叶杨飞; 翟欢乐; 李笑瑜; 朱莉凯; 杨帆; 李红燕; 刘慎悦
Original assignee: Jiangsu Aviation Technical College
Current assignee: Jiangsu Aviation Technical College
Priority date: 2021-06-10
Filing date: 2021-06-10
Publication date: 2023-08-15
Anticipated expiration: 2041-06-10
Also published as: CN113734462A

Abstract

The invention discloses a skin maintenance method of a moving aircraft. It comprises the following steps: A. polishing and correcting each layer inside and outside the damaged part to be rectangular with rounded transition, wherein the boundary of one layer of carbon fiber or glass fiber surface exposed outside the damaged part is at least 30mm away from the crack to form the required repaired part; B. polishing the surface of the carbon fiber or the glass fiber into a conical repairing and paving area with slightly higher middle and slightly lower periphery by using sand paper; C. and thoroughly cleaning the required repair part by using a solvent, coating epoxy resin on the repair part after the solvent is thoroughly volatilized, and paving a carbon fiber patch. The advantages are that: the problem that the gravity center position of the airplane is influenced due to the fact that the structural weight is changed greatly is avoided. The specific heavy repair area can be formed, so that the repair strength can be effectively ensured, and the problem of secondary damage is avoided. The repairing is simple and quick, time and labor are saved, the repairing cost is low, the repairing can bear the specified strength and rigidity, the economic efficiency is improved, the service life is prolonged, and the repairing cost is greatly shortened.

Description

Skin maintenance method for sports aircraft

Technical Field

The invention relates to an aviation aircraft maintenance technology, in particular to a skin maintenance method of a moving aircraft.

Background

The sport aircraft uses balsawood and other materials as an internal framework, and then adopts a high-strength composite material such as carbon fiber or glass fiber as an engine body skin on the surface. Skin damage is often caused during use, especially the skin of a light sport aircraft is more susceptible to damage, and in general, the following problems exist after skin damage: (1) undermining the good aerodynamic performance of the aircraft. (2) The strength, rigidity and durability of the skin at the damaged part are reduced, and the bearing capacity is reduced. (3) The flying safety can be endangered, so that whether maintenance is carried out is judged according to the damage condition, in the prior art, the damage type is mainly classified into scratch, deformation, crack, broken hole and the like, and the damage type is mainly classified into two main types: scratch, deformation, crack and broken hole.

When slight phenomena such as bulging, pit pressing or scratching occur to certain parts of the skin during scratching and deformation, the occurrence of the phenomena can damage the smooth surface of the skin, so that maintenance is required; the conventional maintenance mode is to supplement resin base at the wound and fill the position.

The crack and broken hole are divided into small cracks<8 cm), middle crack (8-15 cm), large crack>15 cm) when encountering small cracks<8 cm), the original covering repair material is cut into a sheet shape, the patch is cleaned, and the transparent material is used for repairingA contact adhesive adheres the patch to the cover; when a middle crack (8-15 cm) appears, the larger crack must be stitched together with a saddle needle and a firm thread, and then repaired according to the repair step of the small crack; when big cracks appear>15 cm), if the wound is too large, it is necessary to re-produce the skin for replacement of the original skin, which is not in the repair field.

For these types of repairs described above, the following steps are performed:

during repair work, the minimum temperature of room temperature is guaranteed to be above 20 ℃ to ensure proper hardening of the laminate, as higher temperatures accelerate the hardening process. Before starting the repair work, the wound must be cleaned, the wound can be wiped with a desilication cleaner or grease solvent, the repair area thoroughly cleaned, and then the damaged area is ground with 60-80 grit paper and the adjacent coating (polyester gel coating) is removed; the fibrous layer should be visible 30-50mm around the damaged area and, if possible, sufficient damaged laminate should be left as a mold for repair work; wide tapes and sheets (fiberglass, metal plates, etc.) can be used to form the base for lamination if not possible; the sheet must be covered with a release agent (e.g., a wrapping tape) so that it can be removed after lamination, fig. 1 being a schematic view of laminate grinding.

The next step is a maintenance preparation phase; the fibrous web is partly cut, the top layer is smaller than the bottom layer, the fibre direction of each layer is the same as the fibre direction of the lowermost layer, the web layer should overlap the repair area by about 30-50mm, the number of layers required depends on the kind of repair material used and the size of the damage, the repair area is then covered with resin, the largest web layer is placed on the lowermost web layer in the fibre direction, the web layer is then fully saturated with brushes, the further web layer is applied and fully soaked in the same way, the last web layer is not resin coated, sufficient resin is ensured to be absorbed from the lower layer by brush application, finally a PE foil is placed on the repair area and the laminate is allowed to harden, the hardening process can be assisted by even heating (about 60 ℃) e.g. using a heated foil. Once the stiffening process has been completed (the upstanding fibres may be broken) the foil is removed and the repair area sanded to ensure a smooth transition of the edge. The repair area should be a few tenths of a millimeter deeper than the surrounding area. If the area is too deep, the area can be filled, and finally, the repair area is painted to protect the repaired position from oxidation, the new laminated board is paved as shown in fig. 2, and by the existing repair method, the repair area is larger and deeper than the damaged area, so that the structural weight is easy to change greatly, especially when the repair is needed for a plurality of areas, the gravity center position of the aircraft is seriously affected, and in addition, the repair method is complex, labor and time are wasted, the repair cost is high, the strength after repair is insufficient, and the situation of re-damage is easy to occur.

Disclosure of Invention

The invention aims to solve the technical problem of providing a skin maintenance method of a sports aircraft, which is simple and quick to repair, time-saving and labor-saving, low in repair cost, appropriate in repair range and small in structural weight change after repair, so that the gravity center position of the aircraft is not influenced and the repair strength is ensured.

In order to solve the technical problems, the skin maintenance method of the sports aircraft comprises the following steps:

A. taking the damaged part as the center, polishing and correcting each layer inside and outside the skin into a rectangle with rounded transition, and exposing the boundary of one layer of the surface of the skin to form a required repairing part at least 30mm away from the crack;

B. grinding the surface of the skin into a conical repairing and paving area with slightly higher middle and slightly lower periphery by using sand paper;

C. and thoroughly cleaning the required repair part by using a solvent, coating epoxy resin on the repair part after the solvent is thoroughly volatilized, and paving a carbon fiber patch.

Glass beads are added in the coating process of the epoxy resin to enhance the strength and rigidity of the repaired structure.

And (3) after the paving is finished, curing the epoxy resin, polishing and trimming the maintained carbon fiber patch after curing, and finally, performing primary coating and finishing paint.

The epoxy resin is an epoxy resin mixed material, and the epoxy resin mixed material takes the epoxy resin as a main raw material and is added with polysulfide rubber and m-xylylenediamine.

The proportioning method of the epoxy resin mixed material comprises the following steps: the components of the epoxy resin mixed material are added into a container for proportioning, and after mechanical stirring for 5-15 minutes, the repairing operation can be carried out after the mixture is kept still for 3-10 minutes.

In the step B, if the damaged part comprises the composite material layer of the inner layer, cleaning and polishing the damaged composite material layer into a smooth repair area without cracks.

The required repair part is the damaged part of the fuselage, the wing or the tail wing.

The tail includes a horizontal tail and a vertical tail.

The wing includes a main wing, a flap, and an aileron.

The invention has the advantages that:

(1) By polishing the damaged part in a proper area and setting a proper repair part, the proper control of the repair part is ensured on the basis of effectively ensuring the repair quality, so that the problem that the gravity center position of the airplane is influenced due to the large change of the structural weight is avoided.

(2) By the process of polishing the surface of the skin into the conical repair area with slightly higher periphery of the middle and slightly bottom, a specific stress repair area can be formed, so that the repair strength can be effectively ensured, and the problem of secondary damage is avoided.

(3) On the basis of the special treatment means, the required repair part is thoroughly cleaned by the solvent, the epoxy resin is directly coated on the repair part and the carbon fiber patch is paved after the solvent is thoroughly volatilized, the repair method is simple and quick, time and labor are saved, the repair cost is very low, the firmness of the coated epoxy resin and the carbon fiber patch is further ensured by adopting the special treatment means, the overall strength is further improved, the damaged part is repaired to bear the specified strength and rigidity, the economic efficiency is improved, the service life is prolonged, and the repair cost is greatly shortened.

Drawings

FIG. 1 is a schematic view of a conventional grinding configuration for laminate panels;

FIG. 2 is a schematic view of a conventional laminate lay-up;

FIG. 3 is a schematic top view of the skin repair of the moving aircraft of the present invention;

fig. 4 is a schematic view of the front view of the skin repair of the moving aircraft of the present invention.

Detailed Description

The skin maintenance method of the sports aircraft does not comprise the conditions that the structural maintenance difficulty is too high, the economic life of the structural component is exceeded, the navigable state needs to be restored in a short time and the like due to the overlarge damage range and the overlarge damage range of the structural component, and the skin maintenance method of the sports aircraft is further described in detail below with reference to the accompanying drawings and the specific embodiments.

As shown in the figure, the skin maintenance method of the moving aircraft is suitable for the moving aircraft adopting carbon fiber or glass fiber as the skin, the repairable part is the damaged part of the fuselage, the wings or the tail wing, the tail wing comprises a horizontal tail wing and a vertical tail wing, and the horizontal tail wing comprises a horizontal stabilizer and an elevator; the vertical tail also includes a vertical stabilizer and a rudder; the wing includes main wing, flap and aileron, it can be seen that the repair part in this embodiment is composed of a composite material board 1 of the bottom layer, a primer layer 2 on the composite material board, and a high-strength fiber surface layer 3 on the primer layer, and the high-strength fiber surface layer has a crack region 4, and the skin repair method of the sport aircraft in this embodiment includes the following steps:

A. the damaged part is taken as the center, each layer (the composite material plate surface 1 and the high-strength fiber surface layer 3) inside and outside the skin is polished and corrected into a rectangle 5 with rounded corner transition, the radius of the rounded corner is larger than 12mm, and the boundary of the exposed high-strength fiber surface layer is at least 25mm away from the crack, so that the required repaired part is formed, the stress on the damaged part of the skin is reduced for better stress of the structure, and meanwhile, the strength is improved;

B. polishing the high-strength fiber surface layer into a conical repairing and paving area with slightly higher middle and slightly lower periphery by using sand paper, and cleaning and polishing the damaged composite material layer into a smooth repairing area without cracks if the damaged part comprises the composite material layer (light filling material) of the inner layer;

C. thoroughly cleaning the required repair part by using a solvent, coating epoxy resin on the repair part after the solvent is thoroughly volatilized, and paving a carbon fiber patch 6;

D. and (3) after the epoxy resin is cured, polishing and trimming the maintained carbon fiber patch (polishing the edge to be flat as shown in fig. 4), and finally, priming and finishing.

Furthermore, the glass beads 7 are added in the coating process of the epoxy resin, and the main function is still to ensure that the stress of the structure is stable so as to enhance the strength and the rigidity of the repaired structure.

The epoxy resin may be an epoxy resin mixed material, which uses epoxy resin as a main raw material and is added with polysulfide rubber, m-xylylenediamine and glass beads, that is, the epoxy resin mixed material is added with glass beads to improve the adhesiveness of the resin, and the auxiliary material after the polysulfide rubber and m-xylylenediamine are proportionally added to improve the elasticity of the coating, so that the coating can form mechanical properties similar to those of an original skin.

The mixture ratio of the composite material (containing glass beads) of the room temperature curing epoxy resin in the invention is as follows:

material name	Proportioning parts
		E-51 epoxy resin	100
201 polysulfide rubber	20
		Glass bead (20 um)	50
M-xylylenediamine	22

The proportioning process comprises the following steps:

under the room temperature environment, the humidity is in the range of 60-90%, the component materials are slowly added into a container for proportioning, after mechanical stirring for 10 minutes, the repairing operation can be carried out after standing for 5 minutes, and the epoxy resin for repairing needs to be used within 30 minutes after proportioning.

Claims

1. A method of repairing a skin of a moving aircraft, comprising the steps of:

A. taking the damaged part as the center, polishing and correcting each layer inside and outside the skin into a rectangle with rounded transition, and forming a required repaired part by exposing the boundary of one layer of carbon fiber or glass fiber surface of the outer layer of the skin to be at least 30mm away from the crack;

C. thoroughly cleaning the required repair part by using a solvent, coating epoxy resin on the repair part after the solvent is thoroughly volatilized, and paving a carbon fiber patch;

after the paving is finished, curing the epoxy resin, polishing and trimming the maintained carbon fiber patch after curing, and finally, performing primary coating and finishing paint;

the epoxy resin is an epoxy resin mixed material, and the epoxy resin mixed material takes the epoxy resin as a main raw material and is added with polysulfide rubber and m-xylylenediamine; glass beads are also added into the epoxy resin mixed material;

the epoxy resin mixed material comprises the following components in percentage by weight: 100 parts of E-51 epoxy resin, 20 parts of 201 polysulfide rubber, 50 parts of glass beads (20 mu m) and 22 parts of m-xylylenediamine.

2. A method of repairing a skin of a moving aircraft according to claim 1, wherein: the proportioning method of the epoxy resin mixed material comprises the following steps: the components of the epoxy resin mixed material are added into a container for proportioning, and after mechanical stirring for 5-15 minutes, the repairing operation can be carried out after the mixture is kept still for 3-10 minutes.

3. A method of repairing a skin of a moving aircraft according to claim 1, wherein: in the step B, if the damaged part comprises the composite material layer of the inner layer, cleaning and polishing the damaged composite material layer into a smooth repair area without cracks.

4. A method of repairing a skin of a moving aircraft according to claim 1, wherein: the required repair part is the damaged part of the fuselage, the wing or the tail wing.

5. A method of repairing a skin of a moving aircraft according to claim 4, wherein: the tail includes a horizontal tail and a vertical tail.

6. A method of repairing a skin of a moving aircraft according to claim 4, wherein: the wing includes a main wing, a flap, and an aileron.