Improving the process of repair of the aircraft panels made of composite materials

Business strategy of NAC "Uzbekistan airways technics". Modernization and unification of the fleet, expansion of production capacity for technical servicing of aircraft. Process design aircraft repair of composite panels. Total price of modification.

23.05.2015

Introduction

Uzbekistan is a country with the aviation world renown

The beginning of our aviation became from 90th years.

January 28, 1992 was established by the Decree of the President Islam Karimov Airline as governmental body for civil aviation ensure the development, coordination and implementation of policy in the field of air transport on the territory of the Republic of Uzbekistan.

National airline "Uzbekiston havoyullari" - the state airline of Uzbekistan, providing the needs of the economy and the population in the aviation services (freight, passenger, special aerial work).

The main functions of the airline are to provide quality services to local and international airlines, the research and implementation of new technologies and scientific developments in the field of air transport.

Airline has the status of association, consisting of structural units having the rights of legal persons, and operates on the principles of cost accounting, self-financing and self-sufficiency. NAC Uzbekiston havoyullari is fixed and current assets, independent and consolidated balance sheet, and other accounts in banking institutions in Uzbekistan and abroad.

Later, on the air line out West European Airbus A-310 -300, Boeing - 757 and 767.

Open 14 international routes. Given the charter flights, experts Metropolitan Airport service aircraft with flights to almost all Asian and European countries.

First in world practice was performed trouble-free operation and maintenance of aircraft outside the Republic.

This experience has allowed to start as soon as possible on ships flying the A- 310 - 757 and Boeing 767. So, the airport "Tashkent" got great potential in the international market of aviation services.

Since the mid-90s, with the support of companies "Strabag", "Fox" and the airport Frankfurt - Main, began work on the reconstruction of the global "northern" and "southern" runways, installed the latest lighting system of production "Siemens", thanks what airport was the second category of ICAO.

In 2001 Tashkent airport complex has been completely renovated, which allowed him to become one of the largest and most comfortable, it is equipped with the latest technology and is capable of high-quality service and passengers, almost, all types of aircraft operating in the world.

NAC Uzbekiston havoyullari flies on a regular basis in more than 40 cities in the world - in Europe and Asia, America and Japan. Representation of airlines operating in 25 countries.

Currently NAC fleet consists of western aircraft Boing-757/767, A320, modern liners domestic production of IL-114 -100, as well as cargo aircraft A300-600. For airworthiness and provide the necessary qualifications aircrew airline has its own training complex, in which modern procedural simulators aircraft Boeing-757/767, A320 and unikalny full - light - simulator IL-114-100. In 2016, planned to receive new-generation aircraft Boeing- 787 -8 Dreamliner, in connection with what is being created on the basis of aircraft repair NAC Uzbekistan airways technics first in Central Asia regional workshop of the major elements of aircraft structures made of composite materials. The composite material (composite) - structural (metallic or non-metallic) material, in which there are reinforcing elements in the form of its yarns, fibers or flakes more durable material. Examples of composite materials reinforced plastic Born, carbon, glass fiber bundles or tissues based on them; aluminum reinforced with steel strings, and beryllium. Combining the volume content of components can receive composite materials with the required strength, heat resistance, modulus of elasticity, abrasion resistance, and create a composition with the necessary magnetic, dielectric, radio absorbing and other special properties.

All 11 airports included in the airlines today have international status. In NAC Uzbekiston havoyullari employs more than 14 thousand employees.

Company's business strategy is to implement a program of civil aviation development, providing for the modernization and unification samoleto-motornogo park, construction of new airport complex reconstruction of air traffic control systems, re airfields modern ground equipment, capacity expansion own repair and technical base and the creation of its base training of highly qualified personnel.

In the airline plans - start international airline alliance SkyTeam.

At present, the services of the international airport "Tashkent" resort recognized airlines such as:

* A/K "Lufthansa"

* A/K "Turk Hava Yullari"

* A/c "British Mediterrenien Eyrueys"

* A/K Aziana Eyrlaynz, INC"

* A/K "Korean Air"

The company P.T. GARUDA INDONESIA

* A/c "Iran Air"

* of A/K Transaero

JSC Aeroflot - Russian Airlines

* of A/K Domodedovo Airlines

* A/ B to "Siberia"

* GAOZT "Armenian Airlines"

* A/K "AIR- XENA"

* A/ K "IMEYR"

* FSUE Perm Airlines"

* CON RUE Belavia"

* A / K "Altyn Air"

* SJC "Airlines of Ukraine"

* NU "Turkmen"

* SAC "KAVMINVODYAVIA"

* JSC "Ural Airlines"

* SAC "Pulkovo"

* JSC AIR KAZAKHSTAN

* JSC "Aeroflot-Don"

* SUE A/K "Tatarstan"

* of A/K Krasnoyarsk Airlines

* of Zug "RusAero"

* JSC Streamline OPS

Company A/K East Line and others

Aeronautical engineering is based on the latest scientific and technical achievements in all areas of modern knowledge, being essentially a catalyst for scientific and technological progress in the field of basic sciences (aerodynamics and gas dynamics, mechanics, solid state physics, etc.) and applied research (materials science, instrumentation, electronics, avionics, etc.) Modern aircraft and helicopters are designed and manufactured in accordance with the special requirements safety and extremely harsh environments: multiple repeatable peak loads, forced flight regimes in all-weather and all-climate conditions, extreme temperatures, aerodynamic nature of the external force. For modern civil aviation (main civil and transport planes, planes for local airlines, multi-mission helicopters, etc.) are essential to increase their resource, reducing the impact of aviation on the environment, comfort, and to minimize the size of the aggregates. Solving these problems is possible thanks to a new approach to the choice of structural and functional materials based on the concept of integrated quality aircraft materials. Integrated quality aircraft materials is determined by parameters that are combined into several groups. Among them the most important are: the weight efficiency, manufacturability (including operational), efficiency, maintainability and testability, as well as several others. Weight efficiency is mainly determined by the characteristics of strength, specific strength.

Estimate the lifetime and durability of aircraft allow the reliability characteristics of the material, such as endurance and resistance to low-cycle fatigue, fatigue crack growth rate, static and cyclic fracture toughness, resistance to stress corrosion cracking, corrosion by stress, exfoliation corrosion and other forms of corrosion, compatibility with other materials, opposition effect Rebinder (adsorption decrease in strength, changes in the mechanical properties of solids due to physico-chemical processes, causing a reduction in the surface, the interfacial energy of the body, manifested in the reduction of strength and fragility occurs, reducing durability; effect PA Rebinder opened in 1928). Reliability of structures is largely determined by the resistance of the metal spread existing fracture (fracture toughness), and not only its emergence.

1. Constructive Part

Aircraft - aerodyne with aerodynamic principles of flight. Despite the variety of types, all aircraft have the same basic units performing similar functions. Such units include wing, fuselage, horizontal and vertical stabilizers, chassis and power plant.

Wing - the bearing surface of the aircraft, designed to create aerodynamic lift, necessary to ensure the flight and maneuver of aircraft in all modes. The wing is a thin-walled shell backed and consists of a frame and cladding; frame - of spars, stringers and walls and ribs. Located on the wing mechanization - slats, flaps, ailerons, spoilers and pylons.

Plumage - is bearing surfaces, which are bodies of stability and controllability of the aircraft. It consists of horizontal and vertical tail.

Fuselage construction being the basis of the aircraft structure combines force with respect to a single entity all its parts.

To facilitate the work on the production and operation of aircraft to devise a system partition on aircraft parts - panel.

Under the panel understood part of the outer surface of the unit or section.

Sheathing forms the outer surface of the wing. From the quality of the wing surface to a certain extent dependent on its aerodynamic characteristics. In modern aircraft primary distribution received tough metal skin, as most fully meets the requirements of aerodynamics, strength, stiffness, mass m. Metal siding often made of sheets. Its thickness varies from 0.5 mm to very few places have loaded the wing tip to 4...6 mm, and even more in highly stressed areas in the root sections.

The most widespread modern airplanes received trim high-strength aluminum alloys. On aircraft flying at high supersonic speeds (M > 2), applies paneling resistant steels and titanium alloys, does not lose its mechanical properties at elevated temperatures under aerodynamic heating design.

Connect the shell plates to each other can be made lap with beveled edge, lap and butt with crossovers. The simplest is the lap joint, but it causes the most drag. Used to reduce the resistance lap joint with beveled edge and lap-joint strike.

Last joint may be made only to thin sheets of a thickness of 0.5... 1 mm. Best aerodynamic relationship and get on the most widely used on modern aircraft is the butt, although here and have to put at least two row riveted joint, whereas in other schemes, you can do single-row suture stitch Rows determined by the current load.

Sheathing joints are carried out by elements of the framework: spars, stringers and ribs. Currently used for fastening cladding countersunk riveting. Holes on the outer surface of the spleen on mortgage countersunk head rivets. When riveting very thin sheets of thickness of 0.5... 0.6 mm holes for mortgage rivet head can be punch. In this case holes are punch or spleen cells and those parts, which is a riveting trim.

Modern airplanes widely used laminated paneling, consisting of two carrier layers interconnected lightweight aggregate. Carriers cladding layers are made mostly of aluminum sheets. The padding may be a cellular, or be constructed of porous corrugated sheet. Honeycomb made from metal foil having a thickness of 0.03... 0.02 mm. Foils are corrugated and are interconnected by gluing, soldering or spot welding.

Type depends on the shape of the comb corrugation. Honeycomb can be made of corrugated and plastic tapes, glued between, a. Porous filler is made of porous plastic materials having a low density. Sheathing with filer corrugated sheet are receptive load whose direction coincides with the direction of the corrugation.

Skin-bearing sheets glued to a placeholder, and metal sheets and can be soldered to a metal filler. In supersonic aircraft wings exposed to the aerodynamic heating of large bearing cladding layers may be fabricated from titanium sheet or sheets of heat-resistant steel, and the honeycomb core - of the same foil material.

Laminated paneling has a number of advantages compared with single-layered. A laminated trim has larger lateral stiffness and consequently, high critical strain. Thus, when the thickness of the carrier layer 5/2 = 1 mm and h = 10 mm, the ratio is 75, and when h = 20 mm - 300. Approximately at the same ratio and the transverse rigidity is increased. For this reason, laminated paneling not need frequent stringer set, can significantly reduce the number of ribs.

Wing with layered plating may be easier with a single-layer lining the wing, supported by stringers. The surface quality of the laminated roof sheathing due to the lack of riveted joints get higher. Laminated paneling has good insulating properties that makes it profitable for its application subject to large aerodynamic heating wings of supersonic aircraft, interior volumes are busy fuel.

But laminated paneling and has major drawbacks. The technology of producing a laminated sheathing complicated complex quality control gluing or soldering carrier layers to a placeholder, difficult repair skin. Great difficulties encountered in the implementation of the joint parts layered skin and its interface with the elements of the power set of wings.

At the junction is necessary to make a connection not only heavily loaded bearing layers of skin, but also padding that ensures their work together. Joint sheathing panels produced at special border. Edging glued or soldered to the supporting skin layers and to a placeholder. The panels, performed using anchor screws, nuts or bolts.

Joint cladding elements with power set wing also produced using fringing. In order to reduce the weight of the layered skin should strive to reduce the number of joints. If the process of the design considerations and can produce long sheathing panel exceeding the length of sheets extending on its carrier layer, the first connecting lining carrier layers using soldering or gluing, and then combine them with a filler.

In the wings of the modern monoblock speed aircraft is widely used siding monolithic panels. This wing almost all senses load weight and trim it constitutes the main part of the mass of the wing. Application of monolithic cladding reduces the weight of the wing due to compliance with the applicable sections sized loads and significantly lower than in the panels with metal cover, the number of connections.

Wings made of monolithic panels have increased torsional rigidity, which is favorable from the viewpoint of aeroelasticity. However, monolithic panels in comparison with the teams have some drawbacks: the complexity of manufacturing large, significant material waste, high cost, difficulty of repair, the worst characteristics of fatigue strength. Monolithic panels produced by milling of plates, compression; rolling, forging and casting. Plates, which are made of milled panel, obtained by hot rolling or forging.

Complex configuration panel is milled in special key-cutting machine tools and machining centers. Panel for more than a simple configuration and can be produced by chemical milling. Curved panels are obtained by milling or flat panel followed by flexible plate or imparting the necessary curvature of the free forging followed by milling to the desired contour.

Compression produced panel of constant cross section parallel longitudinal set. After heat treatment panel is machined molding and final finishing by circumscription. May be prepared by rolling and panels wafer. Before rolling the billet, and the matrix is heated to a hot forging temperature.

Further processing is performed in the panel the same as the processing of the pressed panel. When hot press forming longitudinal and transverse panels and the set thickness of the panel may have a variable cross section along the length, cross sectional shape of trapezoid ribs. Since stamping not possible to get the required dimensional accuracy of the ribs and planking thickness must be calibrated panels or additional machining.

Making panels casting allows you to design with a complex set of power and with a shell thickness significantly less than with other methods for producing panels. Panels made by casting, require less machining. Each of the methods of manufacturing the panels has its own advantages and disadvantages.

Advantages of panels made from milled plates are getting complex configuration panels with variable cross-sections, the relatively high accuracy and surface relative simplicity and low cost used equipment; The disadvantages include a large waste of material (up to-90%). High labor intensity and the worst compared with stamped panels mechanical properties. Advantages pressed panels are their high mechanical properties, low material waste and lower compared to forging power equipment.

The disadvantage is the limited shapes and sizes of panels. The advantages of the panels produced by rolling, it is necessary to take possibility of obtaining much smaller than the molded panels, the thickness of the panel (1 mm or even less), as compared with a hot stamped panels - lower capacity equipment and the comparative simplicity, and hence less tooling costs. A drawback is the limited hot rolled panels geometric shapes in comparison with stamped panels.

Hot stamped panels have almost the same high strength as chipboard panels. When you clone panels provided the desired change in cross-sectional area of ribs and planking thickness obtained low material waste. The major drawback of this method of manufacturing the panels is a lot of power equipment.

So, for the manufacture of panels of aluminum alloy requires a force of 300,000 N per square meter. Therefore, the size limited stamped panels. Most labor and die manufacturing cycle and the inability to obtain the required dimensional accuracy ribs and planking thickness without additional processing are also disadvantages to this method of manufacturing the panels.

Benefits of manufacturing panels cast consist in the possibility of producing large-size panels required, power set, thin skin and necessary in terms of strength change in cross-sectional areas along the length. The advantages of this method of manufacturing the panels should also include low material waste, much greater productivity and low complexity of manufacturing equipment. The main drawback of cast panels - the worst mechanical characteristics.

Currently have proliferated panel made of composite materials. Composite cladding began to use coal - and boroplastics. Panel of composite material allow to obtain high strength and rigid construction of the wing at a significantly lower cost of mass. Panel of KM made as smooth layered skins, skins with stringer reinforcement or sandwich skins with a honeycomb using automated for this purpose production lines.

Smooth laminated panel composed of several layers of tapes of fibers impregnated with a matrix resin stacked on a laying machine with alternating orientation: on the chord (90 ), the chord angle ( 45 ) and perpendicular to the chord (0 ). Stacked layers of skin thus provide the highest strength characteristics of the panel. Next panel pre-crimped and trimmed in the uncured state contour. The panel is placed in a mold is evacuated in an autoclave and cured.

Panel with stringer reinforcement is made of pre-preformatted plating and stringers and their subsequent rejection, during which the sheathing is connected (glued) with stringers.

The process of manufacturing sandwich panel with a transaction involves preforming both skins, making skins in size aggregate, combine all of these elements for bonding - is curing based at an outer skin in a special form, evacuation and abandonment.

Examples of the use of composites in aircraft structures

Material appearance of Russian aircraft production determine more than 120 structural and functional materials, developed in the framework of the presidential program "Development of Russian civil aviationand embedded in the Il-96M, Tu-204, Il-114, Be-200, Tu-last modifications 154, IL-86, and others [10]. Through the use of new aluminum alloys, polymer composites, titanium alloys, structural steels, complex non-metallic materials - paints, adhesives, sealants - provide increased service life products (1.5... 2) resource (1.5 2 times...), fire interior turnaround time during the operation. Structure of consumption of structural materials in aircraft construction is shown in Fig. 1.

Although composites are increasingly used in aircraft construction, the main structural material for a glider are aluminum alloys. In 2000... 2015. their share in the structure of the application is maintained at 50%. The task of increasing reliability, improving crack resistance, improve fatigue properties of the alloy for the fuselage, wing and power set is solved by a significant increase in purity alloys (reduced impurity content of silicon and iron, the amount of excess phases), the development of new modes of heat treatment, improve the quality of semi-finished products.

Figure 1. Structure of consumption of materials in aircraft construction: HTSC materials of high temperature superconductivity; CMC - materials for elastic sensing elements

Due to significant benefits in terms of specific strength and stiffness, exceptional combination of structural, thermal, special properties of composites in a growing volume used in the construction of the aircraft. If the airframe and in the interior of the Tu-204 the scope of application of composites was 14% by weight, the future passenger Airbus (A380 type) it reaches 25%. Application of composites in aircraft construction is illustrated in Fig. 2.

Experience ASTC. Tupolev on the application of organic plastics in previous aircraft for the manufacture of cellular and solid stabilizer panels with operating temperatures above 100C showed their high reliability, especially for maintenance. In the details of the interior and fairings radars used high-tech material sferotekstolit developed at the All-Russian Institute of Aviation Materials (VIAM). Widely used carbon-and glass-fiber manufactured by prepreg technology (layered fillers (glass, carbon fabric) impregnated with thermosetting binder, partially cured. Products used in the production of medium and large size and processed in hydraulic presses with large size plates fitted drawers resins). The floor panels are made of organoplastic combined with the cells based on polymer paper. Fairings for manufacturing radar applied GRP based on epoxy-phenolic binder. In the manufacture of aircraft units of carbon and organic plastics used epoxy universal binder EDT-69H with an operating temperature of 120...130C.

Fig. 2. Use of composite materials in the airframe of the aircraft Tu-204: 1 - Elements of the wing; 2 - pylon; 3 - nacelle (the bow door); 4-IBD; 5 - gear doors; 6 - wing fairing; 7 - elements of feathers: keel stabilizer; 8 - nose fairing; 9 - MAT sash; 10 - Cell panel; 11th floor; 12 - monolithic parts

Fig. 3 shows the use of composites in the airframe far mainline widebody aircraft Il-96-300 (KB them. Ilyushin). The design of the aircraft has been used a large number of composites (1650 kg), which reduced his weight to 520 kg. Feature use of composites in the airframe of the IL-96-300 is that all elements of design are made using hybrid materials. In thin plating on the surface of carbon-impregnated tapes create form for single layer process organic tissue, which provides resistance to erosion and protect the fragile layers of carbon fiber from damage during operation. In more layers organoplastic loaded structures are uniformly distributed over the thickness of the skins (25% of total layers organoplastic number of layers) that provides a higher fracture toughness as compared hybrid construction with carbon-fiber. In addition, applied additional layers of fiberglass, carbon fiber, which are corrosive eliminates contact with aluminum and steel parts. Thus, the reduced complexity of implementation of adjustment and assembly work in the assembly of parts, since in this case the drilling is performed by cutting and fiberglass layers, more manufacturable. Much attention in the production of the IL-96-300 given to the corrosion resistance of composites.

Fig. 3. The use of composite materials in airframe structures IL - 96 - 300: 1 - Elements of the wing; 2 - pylon; 3 - nacelle; 4 - the air intake; 5 - service hatches; 6 - gear doors; 7 - wing fairing, side panel; 8 - honeycombs and monolayer paste; 9 - cell floor; 10 - aft of the wing panel

First time in the Russian practice of creating mainline passenger aircraft airframe airplane Il-96-300 composites are widely used for the elements of the wing, gear doors, pylons, nacelles and other, as well as honeycomb floors, interior. The design uses composite materials (mostly hybrid ugleorganoplastiki) based on universal binder EDT-69H (with the use of epoxy resins KDA. ETF, DP-631U), but not inferior to their foreign counterparts characteristics. In IL-96-300 were widely adopted high-strength film adhesives VC-51 and VC-51A (reinforced), which helped to create highly laminated structural elements, ensuring higher reliability and weight reduction power airframe.

The work performed to modify interior materials - decorative films PDOAZ-25 organita 7TLK, leatherette AIKos, floor material "Abilene-2rubberized fabric 51-ST-1H for flexible pipelines and other FCC allowed to bring them to meet the requirements of "airworthiness life "flammability, smoke production, toxicity.

Designed, developed, implemented, and materials science and technological design and technological solutions for the manufacture of air-conditioning system components made of fiberglass STP-97KP, bins of mikrosferotekstolita MCT-7P; in order to reduce the complexity of manufacturing structures of complex configuration designed knitted filler used in the construction instead of honeycomb; designed molding thermoplastic PA-610 decorative structural purpose, the technology of color components during their manufacture by injection molding using a masterbatch pigments; developed a new flame-retardant multifilament yarn "Togilenare block the fire for fabrics and other materials to ensure mass increase efficiency, reliability and durability, comfort passenger compartments.

On the basis of the synthesis of structurally layout and technological solutions composites are increasingly being used, including the creation of large heavy-duty units in Helicopter KB them. Kamov. Thus, the weight of the composite structures in a helicopter Ka-26 was 6%, the Ka-27 (Ka-32) - 15%, Ka-126 (Ra-226) - 17%, the Ka-50 - 35%, the Ka-62 - 55%. Designed by four generations of the rotor blades made of composites. Currently are manufactured and are in operation blade helicopters Ka-26 and Ka-27 (Ka-32), Ka-50. Application of composites in helicopters KB them. Kamov provides: weight reduction by 15...35% increase in resource 1.5... 3 times, increase vitality, reducing labor and manufacturing cycle helicopter 1.5... 3 times.

Thus, uniform rotor blades of helicopters Mi-17 and Mi-38 made of composite materials with the planned flight hours 5000 h of material cost and complexity of manufacturing in mass production have equal performance with similar production costs of all-metal blades with a flight resource 2500 hrs

Given the superior performance properties, qualities (reduced vibration, increased load capacity of 300 kg, increased survivability and reliability), increase flight hours for blades made of composites to 5000 h and above, the development of production of rotor blades made of composites at the Kazan helicopter plant is economically effective measure for the modernization of the Mi-17 and an important direction in the development of production of the Mi-38. Compared with helicopters Mi-8, Mi-17 Mi-38 provides for a further significant increase in the use of composites in the fuselage, fin, stabilizer, and other elements of the design of the helicopter.

The design of the AN-124 "Ruslanis widely used polymer-based composite materials and high-strength high-modulus carbon, glass and organic fillers in excess of their foreign counterparts. (Fig. 4). European consortium "Airbus Industriein the Airbus A380 composite materials used for engine nacelles, wing skins and tail (Fig. 4). Composite materials, designs Application of KM used in aircraft An-124 aircraft A 380 "Airbus Industrie"

Fig. 4. The use of composites in the construction of passenger aircraft

Increased use of composites in aviation, especially in military aircraft occurs mainly through the expansion of the scope of their use in the main parts of the airframe: the tail, wing, fuselage, helicopter important trend is the use of composites for the production of drive shafts and blades main and tail rotor. In addition, they are used for the manufacture of radar fairings, interior panels, ceiling, ducts, fuel tanks, armor protection for the team and the most vulnerable parts of aircraft and helicopters, etc.

However, it should be noted that the introduction of composites in aircraft structures bearing elements, especially heavy civil, at the first stage was carried out with extreme caution, limited mostly weak and moderate details. The reason - lack of confidence in the operational reliability of new materials, related primarily to the limited amount of experimental studies and field tests. The gradual accumulation of experimental data on the performance properties of the composites, as well as experience in the development and operation of various types of composite structures and improvement of their quality control has led to the fact that to date there is a large number of aircraft such as the DC-10, "Boeing-727", -737, -747, -757, -767, A-310, etc., as well as helicopters, Sikorsky S-76, Sikorsky SH-53D and others, which designs, including vital important, composites have been used.

Fig. 5 gives examples of the use of composites for aircraft "Boeing 767". Total weight of the aggregates composites pas airplane, "Boeing-767" is 1534.5 kg, which reduced the weight of the aircraft by 813 kg. Another example - MD -100 aircraft company "McDonnell Douglas" in the construction of which was used around 6950 kg of composite materials.

Fig. 5. The scheme of composite materials in the construction of a Boeing-767: 1 - wall spar; 2 - fixed rear panel; 3 - spoiler; 4 - aileron internal; 5 - ending keel; 6 - Rudder: 3 - elevator; 9 - facing the cargo compartment; 10 - wing fairing; 11 - fairing exhaust system, flaps; 12-trim upper and lower wing stringers: 13 - external aileron; 14 - Cabin gondola

In most cases the replacement of metal alloys in detail for composites has resulted not only to reduce the structural mass (up to 20-40% as compared with metal analogues), but also to reduce their costs.

Composite body parts plating engines

Thin-walled body parts easy load aircraft engines are the most promising in terms of use of polymeric composite materials. Easy access for periodic visual inspection, diagnosis, and replace them if necessary, ensure reliable operation during the operation of the propulsion system. In a composite performance of body parts have a mass of 20...5% less than metal counterparts. Currently in mass production are the following components of the PS-90A: with sound-absorbing casing nozzle contour nozzle fairing and rear cowl reversing device that reduce engine weight by 21kg. During the implementation phase and experienced mining are: aperture, body suspension, power building, housing the valves, external fairing reversing device, sound-absorbing panel with circuit inside the housing 1, cowl, hood, housing, providing additional engine weight reduction by 39 kg. At the design stage are: the fan housing, paddle rectifiable grille reversing device, a power strip with a planned win by weight to 63 kg.

Thus, the total weight reduction PS-90A engine when using composite parts is about 123 kg. This leads to an increase in payload for medium-haul aircraft TU-204, equipped with two PS-90A engines to 246 kg and for haul aircraft type IL-96-300 four-engine 492 kg. The obvious advantage of composites has led to what is now creating a new PS-90A12 at the design stage requirements laid perform a number of body parts from composite materials. Molding composite body parts is carried out by hand lay on the mandrel variously oriented layers of glass and karboprepreg. Most of the parts are performed entirely from composites, although some constructive solutions provides for the use of metal flanges that can be subsequently replaced with flanges made of composite materials as mining past.

In the general case, the body parts of aircraft engine complex system of concentrated and distributed loads, the main ones are: the internal pressure, tensile load of gas forces and resultant inertial forces applied at the center of mass construction. In addition, the individual components may be exposed to excessive external pressure, the incident exposed the outer flow and compressive forces arising when assembling aircraft engine casing design. Most loaded elements are parts with flange mountings that are considered structural variants made of the same materials as the items themselves and make them one. According to the requirements specification flanges must ensure secure mounting in the temperature range from -60C to 100C under the action of inertial forces with overdrive 5733g and vibration loads with a frequency of 5 Hz to 200 Hz, the amplitude of vibration acceleration to 3,5 g, and have the resources 25 000 hours of work over a period of 10 years. Currently being developed methods of calculating composite flanges for strength, allowing to predict resource body parts in which they are used.

2. Technological part

2.1 Repair process design

From polymeric composite materials

Repair in a production environment is to restore the exiting characteristics of the aggregates. To provide high quality repair need to perform complex preparatory work ensured opting temperature and humidity conditions in the room (the temperature below +18C, relative humidity up to 75%).

In preparation for the elimination of a particular defect should:

determine the damage zone;

define the boundary of damage;

determine the thickness of the skin, its composition and the type of aggregate in the repair area;

select appropriate working methods, equipment, tooling, ma-

forced ones;

learn the rules of work safety.

Before carrying out repair work area must be cleared of contamination at 350 mm from the edge all around the defect. Installing patches on the repaired zone can be performed on two schemes: pasting pre-manufactured lennyh forming patches and patches of prepreg layers in specially cut.

Mr. recess in the hull with partial replacement (if necessary) the aggregate. The second scheme is more desirable because it allows you to recover up to 91% of the original strength. [14]

To determine the suitability of aggregates from PC to operate all available on these defects, as well as repairs made must be applied to the circuit units, indicating the approximate contour defect, its type, size, and distance to the edge of the unit. Scheme retained for the life of the units.

Technological process of repair of units begins with the implementation operation markup defective areas, which is carried out with graphite pencils, colored bars on LCP. Next, the layout of the repaired area of the unit, which is limited to smooth lines with a minimum radius of curvature of 10 mm. The contour of the cut portion is spaced at least 8.10 mm from damage. Conducting further processing steps depends on the type of defect, so we will consider perform repairs all types of defects according to the classification [14] as shown in Table. 1

2.2 Removing scratches

Removing scratches in the matrix, which do not affect the filler produced by applying an adhesive trowel VC-9 (or VC-27) on the pre-treated with fine sandpaper defective portion width of 5 mm to the full depth scratches. On the area of repair is rolled film of Teflon, set plate thickness 0.3-0.5 mm, and the load carried by the adhesive curing regimes listed in Table 2. Eliminating shallow scratches (depth less than 25% of the planking thickness) according to the following technologies:

removed from sanding paint repair zones with-According markup;

processed with fine sandpaper section width of 10-15 mm;

All scratch length at half its depth;

sanded with sandpaper scratch the entire depth with a width about 5 mm and 25-30 mm zone circle scratches. After a clean, dry brush the dust from the defective area;

manufactured and glued (create form) 1-2 layers of prepreg (You can use fiberglass impregnated with glue VC-9 or VC-27 without filler), depending on the depth of the scratch. Prepreg overlap in both directions from scratch at least 60 mm;

The form are create plies of prepreg technology will be discussed later when describing the process of repair peeling skin from honeycomb holes and partial replacement of units with plating.

Eliminating deep scratches made similarly eliminate friction communities.

2.3 Eliminating bundles

Technological process of removing skin bundles depends on place of its discovery. Bundle can be on the perimeter or on the field plating.

Upon detection of the bundle perimeter trim it eliminates after-as follows. Originally cleared defect from the old binder sandpaper or a thin plate with notches. Glue are spew or binder with a syringe (if necessary can be heated to a temperature of 40-50C), tightly compressed area repair manually. Removing excess binder or adhesive cloth soaked in acetone, going technological package of release film (PTFE, polypropylene), heater, thermocouple, tsulagi, heat insulator. On the opposite side contains (a face) and sponge rubber on top of it a metal plate. Installed with a calibrated tightening clamps and performed the appropriate mode of curing the binder or glue.

Elimination of bundles in the field of skin-drills openings in the repair area (Fig. 6). In a nut-holes are eyelets previously degreased in acetone and gasoline. Drying after treatment each solvent for at least 15 min at room temperature. Before screw and piston assembly daubed glue (eg VC-9). Excess adhesive removed carefully. The length of the screw must be less than the height for the cell-filler in the repair area. Through the holes in the nut - Pistone zashpritsovyvaetsya glue and set screw. Conducted mode adhesive curing.

Figure 6. Repair installation bundles with nuts-pistons

1 - the repaired unit; 2 - glue zashpritsovanny zone in repair;

3 - screw installed in the nut-cap; 4 - Exfoliate trim;

5 - nut-cap; 6 - bundle

2.4 Eliminating delaminations

In sandwich constructions from composite honeycomb possible detachment following:

peeling skin from the honeycomb;

delamination of honeycomb from the frame;

peeling skin from the carcass.

Technological methods to address these different scalings from each other, so we consider separately each kind of peeling. But common process step prior to any type of decoration, is the removal of moisture from the cellular structures, as will be discussed nor-same.

2.5 Moisture removal of cell structures

Moisture accumulates in the field unit, wherein there are mechanical-damage firmed, as well as in areas near the sites of assembly and linkage joints with ribs style Farmhouse. After the control for the presence of moisture in the aggregate, in the zones where it has been detected, and also in areas of mechanical damages and delamination of the complex of operations to remove moisture. Technological methods and equipment are slightly different from each other no matter what zone removes moisture (Cabin - honeycomb; skeleton - Honeycomb). Moisture removal zone "frame - honeycombcracked technological holes in parts of the framework and the presence of the anchor or anchor retaining nuts in the frame through their holes pierced or drilled foamable adhesive composition in the cells at a depth of not more than 10 mm (hole diameter is 2-2.5 mm). Moisture removal zone Cabin - honeycomb reams holes 3.6 s 3.8 mm staggered pitch of 60 mm. Technological holes and anchor nuts installed fittings (Fig. 7) for connection to a vacuum system. Connections to the unit are fixed by using a sealant (VIKSINT Y-2-28, VGO-1 etc.) or rubber O-rings. Connections may be made of transparent materials for visual observation of the process of removing moisture.

The unit is placed in the drainage layer of the fabric and was collected by vacuum bag (Fig. 8). Assembled technology package is placed in a heat chamber or bottom heating system installed. Created under the bag, in the defective area, depression 0 OZMPa (0.3 kgf / cm) and temperature rises in the area Repair to (90 5)C at a rate of 2 degrees per minute. Maintained under discharge unit and heating for 6...8 h, removing the vacuum unit is cooled to 40C. Re-verified by the unit for the presence of moisture. When re-evaporation of moisture detection moisture persists, and in its absence you can start to repair the unit.

Figure 7. Installation fittings in the frame and trim parts to remove Moisture: a) a frame assembly; b) in the casing

1 - socket to remove moisture; 2 - rubber gasket; 3 - wall spar; 4 - foamable composition; 5 - honeycomb; 6 - anchor nut; 7 - axis; 8 - sealant; 9 - a nut; 10 - sheathing with a hole

Fig. 8. Shema connect vacuum pump to remove moisture and

1 - connection to a vacuum tube (or ejector) pump; 2 - standard elements (cross, tee) 3 - fitting attached to the opening in the defective area; 4 - vacuum bag; 5 - drainage layer; 6 - repaired unit; 7 - tube for sucking water vapor; 8 - fitting, mounted on a vacuum bag; 9 - a tube that can be connected, converging to the vacuum pump

2.6 Troubleshooting peeling skin from honeycomb

Delamination of honeycomb paneling on units without testing oping acoustic and vibration loads and without special destination, eliminating zashpritsovkoy glue defect installing caps made of aluminum alloy (if sheathing of fiberglass) or titanium (Fig. 9).

Holes zashpritsovku glue and install plugs drilled staggered at 20 mm, if the defect is 40 mm wider. Drilling depth of 3-5 mm. After drilling is removed from the treatment zone vacuuming dust and shavings

Figure 9. Repair peeling with installing plugs type "Screw": 1 - the repaired unit; 2 - adhesive in the area zashpritsovanny repair; 3 - stub; 4 - the opening in the wall of cells for wicking glue

When repairing units in the zone of possible contamination from heated gases from engine, zashpritsovka made using adhesives having improved heat resistance.

Plugs into the aircraft parking conditions can only be installed bottom surface, as their installation is carried out simultaneously with zashpritsevkoy glue defect. If necessary, install the plugs on the upper surfaces of the unit it must be removed from the aircraft. To ensure uniform and complete distribution of glue over the entire surface of the defect between the skin and honeycomb core runs drenazhirovanie wall honeycomb special device (Fig. 10). The openings in the walls of cells should have a circular shape and positioned at a distance of 0.5... 1.5 mm from the drilled casing.

Figure 10. Drainage scheme honeycomb before zashpritsovkoy glue: 1 - a device for drenazhirovaniya; 2 - honeycomb; 3 - sheathing repaired unit; 4 - hole; 5 - Drainage channels in Honeycomb

Prepared to install plug in unit (shortened degreased) produced zashpritsovka glue into the hole in the unit. For repair mainly used pasty adhesives type VC-9, VC-27. They have high viscosity, and discharge them in a special unit be used syringes. The largest application found a syringe with a screw rod, providing pumping cold pasty adhesives (Fig. 11). It is filled with freshly prepared adhesive, then the tip of a syringe inserted into the hole defects glue squeezed by turning the handle. Zashpritsovka glue stops when a sharp increase in pressure (force) extrusion or when the glue from adjacent holes. After work syringe should be carefully washed from the glue residue.

Immediately after zashpritsovki placed in the hole plug, not up-blowing straight. Adhesive flash removed c / b cloth soaked in acetone.

Figure 11. Syringe with a screw rod: 1 - the handle; 2 - screw rod; 3 - union nut; 4 - the case syringe; 5 - piston; 6 - tip

Head caps reinforced adhesive tape and adhesive curing mode is provided. If necessary, heating the repair area is placed on the heater bag and the process is going to the air bag to provide a pressure of 0.05... 0.1 MPa (0.5 L.., 0 kgf / cm), and curing of the adhesive is carried out according to modes specified in Table 2. Processing methods for heating repair zones are discussed in "heating repair zones."

After the curing of the adhesive regime visually monitored installation quality plugs. Availability bundles and controlled delamination flaw or tapping.

Delamination of honeycomb paneling on special units destination (units of the wing, empennage assemblies, gear doors, etc.) must be repaired by removing a plating zone defect with subsequent molding of the prepregs and adhesive film, and if necessary (eg, the presence of corrosion damage of metal honeycomb or damage) perform the replacement honeycomb. Technological process of restoring the defective skin is complex and responsible, so it will be discussed in next section.

2.7 Restoring skin prepreg while gluing it to Honeycomb

After performing partitioning defective area on the unit produced Remove defective plating. Removing the defective skin is made using carbide end mills with a diameter of 5-g 12 mm and above by lilnyh cars mod. SM21-1000-9, as well as diamond wheels, installed lennyh on special pneumatic cutting machines. Device for machining equipped with built-in vacuum cleaners RMB using ejector type devices operating on compressed air and creating vacuum of about 0.03 mPa for removing dust in the process.

When working with the cutting tool systematically, at least 1 time in 20 minutes of continuous operation, verified tool sharpening. Blunting of the cutting edges - is not more than 0.15 mm. On the surface of the fillet radius edge may be formed which are removed by abrasive grinding wheels type PP bunch "K- ceramic, grain 50.40.

To obtain the desired fillet radius selected following the appropriate diameter. During work on the circle can build-up of dark color ("salting"), which is removed by abrasive cleaning bars.

For the preparation of diamond tools for work performed his autopsy diamond grains on the cutting surface by etching in 10% aqueous ferric chloride solution for 20-25 minutes or performed an autopsy diamond grinding grain bars type BKV, BP on keramicheskih bundles with silicon carbide abrasive grain green 63C, grain nistostyu 16 cm hardness at working speed.

To ensure a high connection strength restorable plating thickness exceeding 0.4 mm performed bevel angle 1-3 it around the perimeter. Tenderloin bevels in the skin is made using pneumatic machines and abrasive wheels (Fig. 12). To ensure a given azimuth angle on the surface strengthened Pneumatic clamps of a soft material, the thickness of which is determined by the formula:

where h - thickness of the clamp;

L - distance from the end of the abrasive wheel to clamp;

R - radius of the circle abrasive wheel;

R - radius of the circumference of the body Pneumatic.

Figure 12. Ensuring a given azimuth angle and cover: 1 - pnevmomashinka; 2 - Handle trim; 3 - additional emphasis; 4 - grinding wheel; 5 - inner edge of the cut in the skin

When the bevel is not allowed offset from the inner edgeholes in the hull. For more accurate processing bevels desirable surface drill strengthen more stops.

After removal of the defective skin condition is checked for cell-filler. Special attention is paid to the presence of traces of corrosion damage of aluminum honeycomb, no damage ends faces of honeycomb cells, breaks in cellular docking sites for-filler, etc. For non-compliance requirements for cell zapolnitelyu5ego removed. To do this, cut out the damaged section with a knife honeycomb, cutting line as possible should be a simple form we. When using metallic honeycomb Packer on the line side surface in the recess sotobloka according to Figure 13.

Figure 13. Stitching faces metallic honeycomb: 1-unit repaired; 2-line; 3 - plate

Removed from the surface opposite the remains of plating cell filler, foaming and film adhesives careful not to damage trim.

The work on removal of moisture (whether there was a time-sealing machine), because in the non-metallic parts in the process of exploitation ed out incandescent or medical reflectors. The distance from the heating device to repair zones selected for the requirement of a surface temperature of 60-70C and the heating time is calculated from the rate of 1 hour for each 0.3 mm thick cladding material.

Additional work to replace the damaged honeycomb lie in the selection and fitting of honeycomb and its subsequent gluing the defective area. Selection honeycomb depends of what material it is made of (aluminum fillers, PSP or cell MTP).

When replacing the metal honeycomb increases the size of the workpiece on the amount of 5-8 mm podmyataya, and for non-metallic honeycomb podmyatie not performed, and the size of the workpiece corresponds strictly circuit remote site. Also, take into account the direction in which the sheets of foil, paper or glass in sotobloke repaired. At repair units height wedge insert cells taken 1-2 mm is greater than the height of the removed portion (for subsequent fitting), and to panels fixed height height equal to the height of cellular insert removed trolled or more aggregate thickness skin removed. Honeycomb CAP and MTP are dried before use at 110C for 1 hour.

After fitting insert cell block is performed degreasing surfaces to be bonded, and only degreased metal surface and the honeycomb core of aluminum alloy. Degreasing

Honeycomb is made in a special bath of pure stiff hair brush, dipped in gasoline, then in acetone, and drying the solvent after each treatment at least 15 minutes. Degreased and also on the lateral surface of the metal honeycomb core unit repaired, glued to insert cells.

Workpiece is cut and glue film is rolled into the zone of repair a face by removing the original protective paper, and after stitching protective ing a polyethylene film and the side surface of honeycomb inserting the expandable adhesive film is rolled UTC-3. Setting sotozapolnitelya insertion into the defective area is warmed through the honeycomb core with the adhesive film using the reflector to a temperature of 50-60C, and the maximum cell pressed into the adhesive by pressing the hand. Not allowed aggregate crushing insert. Fixed insert tape, placing it on the paneling crosswise. If the unit has a complex circuit or significant size of the defect, it is desirable to pre-glued honeycomb, check his protruding above the surface of the unit, and if it observed, then remove pursuant to Section 7.13. After preparatory work on gluing and fitting insertion sotobloka can proceed to making patches of individual layers of the prepreg. For the manufacture of the patch used as a pre-fabricated prepreg binder and an adhesive prepreg made of film adhesives, or hot curing adhesives, cold-curing paste. Producing prepregs tie-treated in special courses on manufacturing technology of PCM, and we consider the production of prepreg adhesives directly on-site repairs. For the manufacture of prepregs used dry carbon tape, glass and organotkani, transcribed film adhesives VC-36, VC-41 or VC-51 with a ratio of tape layers (Tissue) and the adhesive film 2-1. The resulting prepreg is laid out on the repaired unit through a layer of adhesive film and molded plastics for curing mode (see Table 2). Modes curing prepreg curing regimes correspond adhesives used to manufacture them. Perhaps obtain a prepreg by hot melt adhesive on the corresponding dry cloth or tape, and tape molding, appropriate tissue glue, by laying cloth tape and an adhesive film between the film layers (Polypropylene or PTFE). Crimping mode:




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