CN110539895B

CN110539895B - Method for repairing damage of aluminum-sprayed layer on outer surface of composite structure of airplane

Info

Publication number: CN110539895B
Application number: CN201910682710.XA
Authority: CN
Inventors: 孙运刚; 宣善勇; 许光群; 常海洋
Original assignee: State Run Wuhu Machinery Factory
Current assignee: State Run Wuhu Machinery Factory
Priority date: 2019-07-26
Filing date: 2019-07-26
Publication date: 2022-08-30
Anticipated expiration: 2039-07-26
Also published as: CN110539895A

Abstract

The invention relates to a method for repairing damage of an aluminum-sprayed layer on the outer surface of an airplane composite material structure, which comprises the following steps: inspecting the lightning stroke damage area by adopting a visual and ultrasonic method; cleaning the surface of the damaged area and wiping the surface dry; protecting the outline to be repaired by adopting an identification belt and removing the surface layer of the damaged area; carrying out dehumidification treatment on the damaged area; preparing a proper J-338B composite adhesive film according to the size of the damaged area and the thickness of the damaged area which is 15mm larger than the damaged area; bonding and curing the preheated J-338B composite adhesive film in the damaged area; after the solidification is finished, polishing the repair area by using No. 150 abrasive paper; and entrusted to a nondestructive testing department to carry out ultrasonic inspection within 50mm outside the repair area, thereby ensuring the cementing quality. The invention is fast and convenient, can realize the rapid rush repair and restoration capability of internal and external fields, and the carrying of the repair material is convenient; the operability is strong, and common operators who work on the repair of the composite material can undertake the operation.

Description

Method for repairing damage of aluminum-sprayed layer on outer surface of composite structure of airplane

Technical Field

The invention relates to the technical field of aircraft outer surface repair, in particular to a repair method for damage of an aluminum layer sprayed on the outer surface of an aircraft composite material structure.

Background

Compared with metal materials, the composite material has excellent mechanical properties, but also has the defects of poor conductivity, high resistivity and the like. Lightning strikes can cause the ignition of discontinuous conductive parts, and the ablation of materials causes the great reduction of the structural performance and even the failure. The damage of lightning stroke to the composite material structure has the following conditions: (1) the high voltage at the time of lightning strike causes the composite structure to break down. (2) Lightning arcing and sustained current can cause material ablation and burning, fiber breakage, and structural damage. (3) Lightning strike electric arc and continuous heavy current heating are carried out, so that the pressure in the cavity of the composite material structure with the closed cavity is rapidly increased, and the structure is finally damaged. (4) The shock waves and magnetic fields in lightning strikes cause structural damage.

When an airplane is struck by lightning, the parameters influencing the structural damage are mainly 3: residence time of lightning strike attachment point, output of lightning strike charge, and high voltage. The residence time of the lightning strike attachment point is greatly affected by the electrical properties of the surface layer of the structure. The longer the duration of the lightning strike at the attachment point, the greater the amount of power delivered to the structure through the attachment point, and the easier the structure at the attachment point is to ablate or break down. The high voltage value at the time of lightning strike is generally considered to be about 2.0 MV. High voltages mainly cause electrical breakdown of poor conductor materials.

The following lightning protection measures are mainly used:

(1) and (4) protecting the mesh foil. The method is to lay a metal surface layer on the outer surface of the composite material structure, wherein the surface layer can be metal foil, woven or non-woven metal mesh, the woven metal mesh is manufactured by a machine weaving method, and the non-woven metal mesh is manufactured by punching the metal foil.

(2) And (4) surface layer protection. The method is to add some conductive materials into the outer surface coating, such as surface spraying metal materials, or to add metal particles into the spraying materials, or to add metal strips on the surface of the paint layer. After being struck by lightning, the protective layer can rapidly conduct away the electric charge, thereby reducing the probability of organism damage. The disadvantage is that it is disposable and does not provide the ability to continue to protect the damaged area after a lightning strike.

(3) A compound adhesive film protection method. The method combines a surface adhesive film and a conductive metal net into a whole, and the conductive layer mainly comprises 3 types of metal foils, woven metal mesh screens and metal nets. When the lightning protection structure is used, the glue film is paved on the outer surface of the composite material structure, and lightning strike charges are transmitted to the discharging tip of the machine body through the metal net for discharging, so that the lightning strike protection effect is achieved.

(4) Adding nano conductive material to protect. For lightning strike protection, one possible approach is to provide sufficient conductivity by changing the non-conductive material to a conductive material, and thus lightning strike protection can be achieved by adding a nano-conductive material to the composite matrix, the material so produced also being referred to as a nanocomposite. The added nano conductive materials are mainly of 3 types, and are respectively one-dimensional materials such as carbon nano tubes, two-dimensional materials such as graphene sheets, and three-dimensional materials such as surface copper coating particles. The advantages and disadvantages of the different lightning protection methods are summarized in table 1 below.

TABLE 1 lightning protection advantages and disadvantages

At present, the protection form of spraying an aluminum layer on a repaired composite material is mainly a surface layer protection method, and a flame aluminum spraying process is adopted to enable the outer surface to be a conductive metal layer so as to achieve the lightning stroke protection effect. However, on-machine inspection and external field service processes find that the aluminum-sprayed layer of the composite material structural part is damaged in different degrees, so that the surface conductivity of the composite material structure is greatly reduced, and the composite material part cannot be protected continuously.

Disclosure of Invention

Aiming at the damage of the aluminum layer sprayed on the surface of the composite material component of the airplane, the invention provides a method for repairing the damage of the aluminum layer sprayed on the outer surface of the composite material structure of the airplane, so as to recover and even improve the lightning stroke protection capability of the airplane.

The technical problem to be solved by the invention is realized by adopting the following technical scheme:

the method for repairing the damage of the aluminum spraying layer on the outer surface of the composite material structure of the airplane is characterized by comprising the following steps: the method comprises the following specific steps:

A. inspecting the lightning stroke damage area by adopting a visual and ultrasonic method;

B. cleaning the surface of the damaged area and wiping the surface dry;

C. protecting the outline to be repaired by adopting an identification belt and removing the surface layer of the damaged area;

D. dehumidifying the damaged area;

E. preparing a proper J-338B composite adhesive film according to the size of the damaged area, wherein the size is 15mm larger than the damaged area, and performing preheating treatment on the composite adhesive film for 1min at the temperature of not higher than 80 ℃ by using a hair drier;

F. bonding and curing the preheated J-338B composite adhesive film in the damaged area;

G. after the curing is finished, polishing the repair area by using No. 150 abrasive paper to ensure that the edge of the repair area is in smooth transition;

H. and entrusted to a nondestructive testing department to carry out ultrasonic inspection within 50mm outside the repair area, thereby ensuring the cementing quality.

Further, the specific steps of cleaning the repaired surface in the step B are as follows:

s1, absorbing all dust on the damaged surface by using an industrial dust collector;

s2, using two clean rags without velvet, wetting one rag with solvent (acetone or chloroform) to wipe the repairing area, and wiping the other rag with the solvent immediately before the solvent is volatilized;

and S3, repeating the operation until the cloth wiping the damaged area is not dirty.

Further, the following operations are required before removing the surface layer of the damaged area in the step C:

removing dirt on the surface layer of the damaged area;

secondly, grinding the damaged area by using 80 # sand paper and 150# sand paper in a grading way to expose the metal luster of the aluminum spraying layer;

and (III) sucking the grinding dust by using an industrial dust collector, cleaning by using a solvent, and drying according to requirements.

Further, the specific steps of the dehumidification treatment of the damaged area in the step D are as follows:

a. applying a controlled heat source to the area to be repaired;

b. placing a sealing rubber strip in the whole area to be repaired, and sealing the whole area to be repaired by using a vacuum bag material;

c. drawing a vacuum of at least 0.05 MPa;

d. drying the repair area for at least 1h at a temperature of (60-80) DEG C.

Further, the step F of adhering and curing the adhesive film to the damaged area includes the following specific steps:

(1) laying the preheated adhesive film according to the size of the marked damage area, and scraping and compacting by using a scraper;

(2) then assembling the repair laying layer, the isolation cloth, the drainage layer, the air-permeable felt, the pressure plate, the air suction layer, the electric blanket and the insulating layer into a vacuum bag in sequence;

(3) curing is carried out according to a curing procedure.

The invention has the beneficial effects that:

compared with the traditional restoration of the repair of the sprayed aluminum layer, the repair technology of the composite adhesive film patching provided by the invention has the following advantages that: firstly, the repair is rapid and convenient, the traditional repair of the damage of the aluminum spraying layer is only suitable for in-plant repair, the equipment requirement is high, the composite adhesive film patching repair technology can realize the rapid repair and repair capability of an internal and external field, and the repair material is convenient to carry; secondly, the operability is strong, the traditional damage repair of the aluminum spraying layer has higher requirements on the technical capability and experience level of operators, the technique of the repair of the composite adhesive film patch is simple and mature, and common operators engaged in the repair work of the composite material can undertake the repair.

Drawings

The invention is further illustrated with reference to the following figures and examples:

FIG. 1 is a schematic flow diagram of the present invention;

FIG. 2 is a schematic view of the vacuum bag package of the present invention;

FIG. 3 is a temperature-time diagram of the curing process of the present invention;

FIG. 4 is a schematic diagram of the current components of the present invention;

FIG. 5 is a schematic view of a lightning zone distribution of an aircraft according to the present invention;

FIG. 6 is a schematic view of lightning strike visual damage prior to repair in accordance with the present invention;

FIG. 7 is a schematic view of lightning strike visual damage after repair in accordance with the present invention;

FIG. 8 is a schematic view of a 50mm by 50mm damaged surface repairing lightning strike visual damage in accordance with the present invention;

FIG. 9 is a schematic view of a 100mm by 100mm damaged surface repairing lightning strike visual damage in accordance with the invention;

FIG. 10 is a schematic view of a 200mm by 200mm damaged surface repairing lightning strike visual damage in accordance with the invention;

FIG. 11 is a schematic view of a lightning damage before aluminum spraying by the ultrasonic detector C according to the present invention;

FIG. 12 is a schematic view of the ultrasonic detector C according to the present invention showing the damage caused by lightning after aluminum spraying;

FIG. 13 is a schematic view of an ultrasonic C-scan of a 50mm by 50mm paved area lightning damage in the present invention;

FIG. 14 is a schematic ultrasonic C-scan of a 100mm by 100mm paved area lightning damage in the present invention;

FIG. 15 is a schematic view of an ultrasonic C-scan of a 200mm by 200mm paved area for lightning damage in the present invention;

FIG. 16 is a distribution diagram of the damaged area after the repair of the metal mesh in the present invention.

Detailed Description

In order to make the technical means, the creation characteristics, the achievement purposes and the effects of the invention easy to understand, the invention is further explained in the following by combining the attached drawings and the embodiments.

As shown in fig. 1 to 16, a method for repairing damage of an aluminum layer sprayed on an outer surface of an aircraft composite structure includes the following steps:

A. nondestructive testing and related professionals adopt visual and ultrasonic methods to inspect a lightning stroke damage area, determine a damage part and a damage size, analyze the damage degree and make correct evaluation.

B. The surface of the damaged area is cleaned and wiped dry (not allowed to evaporate naturally).

The specific steps for cleaning the surface of the damaged area are as follows:

and S3, repeating the operation until the cloth for wiping the damaged area is not dirty.

specifically, the contour to be repaired is firstly attached by using the identification tape, which is beneficial to protecting the surrounding undamaged area and protruding the repair part; the surface layer is then removed, which facilitates determination of the type of damage, enhancement of the adhesive force, and restoration of friction at the threaded joint.

The specific steps for removing the surface layer are as follows:

1) before the surface protective coating is removed, hot water, detergent or solvent is used for scrubbing possible oil stains, attached dust and sediments (such as water alkali, salt and the like) on the surface of the composite material part, and after the dirt on the surface is removed, the protective coating in a repair area can be removed;

2) using 80 # sand paper and 150# sand paper to polish the surface damage layer of the repair area in a fractional way; polishing 15mm outside the damaged area to expose the metal luster of the aluminum spraying layer;

3) generally, a manual or pneumatic grinding method is used for removing the aluminum sprayed layer on the surface, 80 # abrasive paper is used for removing all the finish paint and most of the primer, 150# abrasive paper is used for removing the residual primer, and the fibers are not allowed to be damaged in the grinding process, so that the surface and the edge of the laminated board cannot be damaged; in addition, the use of chemical strippers and sand blowers to remove the surface layer is not allowed because they attack the resin or cause surface delamination by impact.

D. Dehumidifying the damaged area;

the specific operation steps are as follows:

a. applying a controlled heat source (e.g., using a hair dryer, radiant lamp, or electric blanket, etc.) to the repair area;

b. placing a sealing rubber strip in the whole repair area, and sealing the whole area by using a vacuum bag material;

c. drawing a vacuum of at least 0.05 MPa;

d. heating, and drying the repair area for at least 1h at the temperature of (60-80) DEG C.

E. Preparing a proper J-338B composite adhesive film according to the size of the damaged area, wherein the size of the damaged area is 15mm larger than the damaged area, and performing preheating treatment on the J-338B composite adhesive film for 1min at the temperature of not higher than 80 ℃ by using a hair drier;

the concrete bonding and curing steps are as follows:

(1) laying the preheated J-338B composite adhesive film according to the size of the marked damage area, and scraping and compacting by using a scraper;

(2) assembling vacuum bags according to the laying sequence of FIG. 2;

(3) finally, the curing procedure of fig. 3 is followed.

H. and entrusted to a nondestructive examination department to carry out ultrasonic examination within 50mm outside the repair area so as to ensure the gluing quality.

After repairing the damage of the aluminum-sprayed layer by the J-338B composite adhesive film, the outer surface of the airplane needs to be inspected for the effect by an effect verification method.

The specific process is as follows:

and (3) carrying out lightning stroke test on the test piece according to the airplane lightning protection requirement and test method of HB6129, wherein the test piece has 4 current components A, B, C, D. The current components A, B, C, D each simulate different current characteristics of the natural lightning discharge process, as shown in FIG. 4, which are all used to determine the direct effect of lightning.

Component a-initial peak current; the peak value of the component A is 200KA + -10%, and the duration is 500 us.

Component B-intermediate current; the average amplitude of component B is 2KA ± 10%, the maximum duration is 5 ms.

Component C — the persistent current; the component C transfers charge 200C + -20% at a time of (0.25-1) s, and the average current amplitude is (200-800) A.

Component D-repetitive discharge current; the peak value of the component D is 100KA + -10%, and the duration is 500 us.

Referring to the distribution of the airplane thunderbolt area in FIG. 5, most areas of the airplane body and part attachments belong to the area 2A, so that the current component is B, C, D waveforms by adopting a structural direct effect test (2A) test method.

As can be seen from FIGS. 6 and 7, the test piece before repair falls off with the sprayed aluminum layer, the resin matrix thermally degrades, and a small amount of surface fiber splitting is accompanied; after the J-338B composite adhesive film is repaired, the damage mode is obviously changed, only the composite adhesive film is damaged, the repair patch is invalid, and the composite material matrix has no obvious visual damage.

As can be seen from fig. 8 to 10, the central damage profile and area are almost the same after three area specifications are visually observed, but the film base material is yellowed or even blackened around the damage center, thermal degradation occurs to the film resin base, and spread in a fan shape along the lightning strike attachment point. A small amount of base materials turn yellow at the lap joint part and the edge of the test piece, because the resistance at the lap joint part changes suddenly, the base materials are damaged due to the change of the current, and the fiber splitting damage does not occur.

FIGS. 11 and 12 are schematic diagrams of the ultrasonic detector C for scanning damage caused by lightning before and after aluminum spraying. The ultrasonic detector adopts a model Rapidscan2 of an ultrasonic C-scan imaging system in a factory, and the scanning principle is based on the principle that ultrasonic waves can be reflected between different media. In the process of transmitting ultrasonic waves through a medium, if the ultrasonic waves encounter substances or phase interfaces with different elastic coefficients or densities, reflected waves are generated, and the intensity of the reflected waves is different due to different material densities. The signal acquisition system processes different signals, and internal information of the object to be detected can be obtained on the premise of not damaging a sample. The material to be detected with air holes, cracks, cavities and delaminations inside can be obtained by a nondestructive testing method.

As can be seen from FIG. 11, the color of the central area of the test piece without aluminum spraying is completely white, which indicates that the test piece cannot transmit waves, the fiber is seriously split, and the surface layer completely fails; in contrast, as can be seen in FIG. 12, after aluminizing, the area color spreads out as white spots, the damage pattern changes, transitioning from complete fiber splitting to surface resin ablation with a small amount of fiber splitting.

FIGS. 13 to 15 are schematic ultrasonic C-scan diagrams of lightning stroke damages of three different overlay areas of 50mm × 50mm, 100mm × 100mm and 200mm × 200mm, pixels are converted by Photoshop to calculate the size of the damaged area in the photo, and as shown in FIG. 16, after the repairing of the metal mesh, the damaged area of 50mm × 50mm is changed from the original 91mm ² (test piece for aluminum spraying) reduction to 42mm ² The surface of the composite material structural member is sprayed with aluminum and paved with the metal mesh, so that the non-conducting condition of the composite material can be effectively solved, and further the damage of lightning stroke to the composite material structure is reduced. Repairing 50mm x 50mm (42 mm) in comparison with different sizes ² )、100mm×100mm(26.6mm ² )、200mm×200(28.7mm ² ) mm, the size of the polished area is larger than 100mmThe repairing effect is obvious.

As shown in table 2 below, the case of the aluminum-sprayed layer repair;

TABLE 2 repair recovery Performance index

Therefore, in conclusion, the problem of damage of the aluminum spraying layer on the outer surface of the composite material structure of the airplane is solved by using the composite adhesive film patching and repairing technology, the outfield first-aid repair efficiency is improved, the safety of the airplane is ensured, and the composite adhesive film patching and repairing technology has high economic benefit.

The foregoing shows and describes the general principles, essential features, and advantages of the invention. It will be understood by those skilled in the art that the present invention is not limited to the embodiments described above, which are merely illustrative of the principles of the invention, but that various changes and modifications may be made without departing from the spirit and scope of the invention, which fall within the scope of the invention as claimed. The scope of the invention is defined by the appended claims and equivalents thereof.

Claims

1. A method for repairing damage of an aluminum spraying layer on the outer surface of an airplane composite material structure is characterized by comprising the following steps: the method comprises the following specific steps:

B. cleaning the surface of the damaged area and wiping the surface dry;

specifically, the specific steps of cleaning the surface of the damaged area in the step B are as follows:

s2, using two clean rags without velvet, one is soaked by solvent, wiping the repair area until no solvent is sprayed, and immediately wiping the repair area by another piece of dry cloth before the solvent is volatilized;

s3, repeating the operation until the cloth for wiping the damaged area is not dirty;

specifically, the following operations are required before removing the surface layer of the damaged area in the step C:

removing dirt on the surface layer of the damaged area;

secondly, polishing the damaged area by using No. 80 and No. 150 abrasive paper in a grading way to expose the metal luster of the aluminum spraying layer;

thirdly, sucking the grinding dust by using an industrial dust collector, cleaning by using a solvent, and drying according to requirements;

D. dehumidifying the damaged area;

E. preparing a proper J-338B composite adhesive film according to the size of the damaged area, wherein the size of the damaged area is 15mm larger than the damaged area, and performing preheating treatment on the composite adhesive film for 1min at the temperature of not higher than 80 ℃ by using a hair drier;

specifically, the step F of adhering and curing the adhesive film to the damaged area includes the following steps:

curing according to a curing program;

2. The method for repairing the damage of the aluminum-sprayed layer on the outer surface of the composite material structure of the airplane as claimed in claim 1, wherein the method comprises the following steps: the specific steps of the dehumidification treatment of the damaged area in the step D are as follows:

a. applying a controlled heat source to the area to be repaired;

c. drawing a vacuum of at least 0.05 MPa;

d. drying the repair area for at least 1h at a temperature of 60-80 ℃.

3. The method for repairing the damage of the aluminum-sprayed layer on the outer surface of the composite material structure of the airplane as claimed in claim 1, wherein the method comprises the following steps: the solvent in step S2 is acetone or chloroform.