RU2412053C1 - Method of producing aircraft reticular airframe floor beam from polymer composite materials - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to plastic forming, coiling and jointing, and may be used in aircraft and aerospace engineering. In compliance with proposed method, rubber-like protector with spiral, lengthwise and crosswise grooves is, first, fitted on mandrel. Then, shaping elements are applied onto article workpiece to be thermally treated. Now core is withdrawn from collapsible rubber-like protector. Note here that prepreg unidirectional tapes are wound in protector grooves on the mandrel. The latter is made up of two hollow tubes clamped as-strained by long stud and having flanges arranged on their ends furnished with reverse studs and closed-section protector from rubber-like elastic material.

EFFECT: ease of manufacture, higher precision of article production, improved strength characteristics.

5 dwg

Description

The field of technology.

The invention relates to the field of molding plastics, shaping them by winding and joining, and more particularly, to a method for manufacturing supporting beams of an aircraft floor.

It can be used in aircraft, space technology, shipbuilding and automotive industries, for the manufacture of shell casings in order to increase their strength characteristics and reduce the weight of the structure.

The prior art.

A known method of manufacturing a pipe-shell of a cellular structure from composite materials according to the patent of the Russian Federation 2084343, class. В29С 53/56, В29С 53/82, В32В 3/12, 1997. According to this patent, the mandrel is covered with a rubber-like material with mutually intersecting grooves, intersecting spiral, longitudinal and annular ribbons of unidirectional threads pre-impregnated with a binder to form stiffeners between the crosshairs are laid in grooves, forming elements are applied to the ribbons and heat treated with subsequent removal of the mandrel and rubber-like material. A distinctive feature of the method is that, for the formation of stiffeners, they finish laying the tapes in grooves with the formation of an allowance of rubber-like material above the stiffeners by 0.02-0.3 of their height, and when applying the forming elements, the rubber-like material allowances are elastically deformed by them in the radial direction with the formation of an external protective coating bonded to stiffeners and crosshairs, moreover, ring ribbons of the outer layer are used as forming elements, and the cross The existence of longitudinal and annular ribbons is formed adjacent to the spiral ribbons.

The disadvantage of this invention is that the position of the rubber-like material on the mandrel is not reliable and can be displaced when winding unidirectional tapes. The difficulty is the need to rigidly fix the rubber-like material on the mandrel during winding, but at the same time, so that the proposed mounting option would not create obstacles when removing the mandrel. In addition, if it is necessary to manufacture a beam of rectangular cross section, providing a junction of the grooves will cause great difficulty.

Closest to the proposed invention in technical essence and the achieved effect is the floor beam of the aircraft from PCM according to the patent of the Russian Federation 77842, class. B64C 1/08, B29C 53/56, 2008.

According to this patent, the mesh beam of the rectangular floor contains spiral ribs, longitudinal ribs and transverse ribs, as well as monolithic sections of the woven prepreg. A rectangular mesh floor beam is wound on a winding machine on a special mandrel in layers with a unidirectional prepreg ribbon for ribs and a woven prepreg ribbon for monolithic sections. The winding is performed in layers in the following sequence: spiral ribs, transverse ribs, longitudinal ribs. In this sequence, the first layers of all the ribs are wound, after which, in the places of monolithic sections, one layer of woven fabric is wound. Further, everything is repeated in layers for the second, third, fourth, etc. layers to the formation of a given thickness of the workpiece. The sections of the floor beam between the ribs remain unfilled with material and through holes are formed there. After winding up the workpiece blank, it undergoes a molding operation in a furnace or autoclave under the influence of the temperature, pressure and holding time required by the process, until the curing of the binder is complete.

The disadvantage of this method is that due to the lengthy closed design of the mesh floor beams obtained by winding, the process of removing it from the tool can be very time-consuming or even impossible without damaging the product. In view of the lengthiness of the beam, the floor in the middle of the tooling for the beam fixed in the pins of the winding machine, a deflection is formed, which during winding leads to a decrease in the accuracy of manufacture of the product and, therefore, to a decrease in its quality.

In addition, the winding process involves the presence of allowances at the ends of the beam, which must be removed before removing the product. Thus, the machining process increases the complexity of the product and its cost.

Moreover, there is a high probability of defects in the product due to the fact that during the curing process the prepreg tapes laid in the grooves of the tread are not additionally pressed against each other.

SUMMARY OF THE INVENTION

The objective of the present invention is to develop a complete process for the production of mesh floor beams of rectangular cross-section from PCM, providing high-quality products - with high precision, good strength characteristics.

In addition, the method should provide high adaptability by reducing the number of additional operations.

The problem is solved due to the fact that in the method of manufacturing the beam of the floor of the airframe of an airplane of a net structure from PCM, a rubber-like tread with a system of spiral, longitudinal and transverse grooves is placed on the mandrel. Unidirectional prepreg tapes are wound in grooves of the tread. In addition, forming elements are applied to the product blank. The following steps carry out heat treatment and removing the mandrel from a collapsible rubber-like tread.

The winding of unidirectional prepreg tapes in the grooves of the tread is performed on a mandrel made in the form of two hollow pipes of complex internal section, pulled together (in tension) by a long hairpin. At the ends of the studs are installed flanges equipped with reverse studs. The dorn is equipped with a closed-section tread made of rubber-like elastic material.

This solution to the problem allows you to get a mesh floor beam from high quality PCM, with good strength characteristics using a high-tech method.

The list of drawings.

Figure 1. A section A-A of FIG. 4 is shown.

Figure 2. An end face of a floor beam with a mounted flange is presented.

Figure 3. Presents region B of figure 1.

Figure 4. Accessories for floor beams, assembly drawing.

Fig 5. The area In figure 4.

The implementation of the invention

It is necessary to make a beam of the floor of an airframe of an airfoil of a mesh structure made of PCM containing spiral intersecting tapes connected together by solid sections of woven PCM prepreg laid on top of turns of rectangular cross section. The floor beam is made in the form of a hollow closed mesh structure having a cross-section in the form of a rectangular frame with rounded corners. The floor beam is provided with additional longitudinal and transverse ribs associated with spiral ribs. In addition, in places of future installation of connected parts there are monolithic sections based on woven fibrous filler

The method in accordance with the invention is as follows.

- Install on the ends of the pipes 1, 2 (Figs. 1, 4) flanges 3, 4 using bolt connections 5 (Fig. 3).

- Carry out pulling into a single mandrel hollow pipes 1, 2.

The hollow pipes 1, 2 are put on a long stud 6, the pipes 1, 2 are mutually oriented relative to each other with the help of pins 7 and holes 8 (Fig. 3).

Fasten the pipes oriented relative to each other by tightening the nuts 9 at the ends of the long stud 6, creating a prestressed state in them.

- Apply release agent to the surface of the mandrel.

- Place a protector 10 on the mandrel.

- Dorn with a protector is placed in the cartridges of the winding machine using the pins 11.

- Carry out the process of layerwise winding of the prepreg with filling the grooves of the tread and the formation of the workpiece beams.

The first layer of the prepreg tape is wound using reverse pins in the following sequence: spiral ribs, transverse ribs, longitudinal ribs, then a monolithic section of the floor beam is wound with a woven prepreg. Successively carry out the winding of the second, third, fourth, etc. layers.

- Dorn with the workpiece is removed from the winding machine.

- A vacuum bag is placed on the surface of the workpiece (in the case of molding in an autoclave) or wickel is made with lavsan thread to provide pressure on the workpiece being molded (in the case of molding in a thermal furnace).

- Form the workpiece in an autoclave under the necessary conditions for curing the prepreg. Or they produce molding in a thermal furnace chamber at the temperature conditions necessary for curing the prepreg.

- Remove from an autoclave or thermal furnace chamber.

- Cool at room temperature.

- Free the blank with the mandrel from the vacuum bag or mylar ribbon.

- Carry out the trimming of the endings (technological allowances) in the area of the flanges 3, 4 adjacent to the pipes 1, 2.

- Make dismantling and extraction from the cavity of the pipes of the long studs 6.

- Carry out the capture of the pins 11 in the holders of a device such as a hydraulic cylinder, where they apply the force necessary to connect the hollow pipes.

- Carry out the hollow pipe and remove one of them from the tread, the second pipe is removed from the tread by pushing.

- Free the product from the tread by pushing it inside the product.

- Remove the tread from the product.

Equipment for forming a mesh floor beam (Fig. 1, Fig. 4) consists of two equal hollow pipes 1, 2, tread 10, flange 3, 4.

The hollow pipes 1, 2 are made of steel, have a rectangular cross section identical to the internal section of the net beam of the floor minus the thickness of the tread. Hollow pipes are made with an internal cavity 12 of complex section (Fig. 1). Hollow pipes 1, 2 are mutually oriented due to pins 7 and holes 8 (Figure 2) located at the ends of the pipes opposite the flanges.

Tread 10 - a tread of rectangular closed section made of flexible heat-resistant material, such as silicone rubber. The material for the manufacture of the tread should provide low adhesion to other materials and have thermostability necessary for forming the prepreg of the floor beam according to the passport regimes. The outer surface of the tread 10 is made with a congruent pattern of channels with respect to the pattern of the grid of the floor beam (Fig. 5). The tread is made with spiral channels 13 and 14, has monolithic sections 15, can have transverse channels 16 and longitudinal channels 17. The intersection angle of the spiral grooves is 45 ± 5 ° to the longitudinal axis of the beam, transverse - 90 °, longitudinal - 0 °. The inner surface of the tread is smooth. The cross-section of the tread 10 is performed similarly to the outer section of the hollow pipes 1, 2 with the possibility of longitudinal sliding of the tread along their surface.

Flanges 3, 4 (figure 2) are made of steel. The flanges have a cavity to allow the passage of inside the pipes of a long stud 6 with a thread at the ends for tightening the pipes when assembling the equipment into a single mandrel. The flanges have pins 11 for clamping in the cartridges of a winding machine. Also, the flanges are equipped with four reverse studs 18 at the corners of a rectangular profile to ensure the fixing of the tape during winding, due to which a given pattern of the floor beam mesh is obtained. The lengths of the studs 18 should be sufficient to accommodate the required amount of tape. The diameter of the studs and their location is selected in such a way as to ensure accurate laying of the prepreg ribbon along a given trajectory of the pattern. The flanges are mounted on the ends of the pipes 1,2 using a bolted connection 5.

Proposed by the present invention, the method is as follows.

At the first stage, the mandrel is assembled. On the ends of the pipes 1, 2, install flanges 3, 4 using bolt connections 5. The hollow pipes 1, 2 are put on a long stud 6 with threads at the ends, while orienting them relative to each other using pins 7 and holes 8 located on the ends of the pipes opposite flange. Then they fasten the pipes by tightening the nuts 9 at the ends of the long studs located in the cavity of the pipes, thereby obtaining a single mandrel in a prestressed state.

Release grease is applied to the surface of the mandrel, after which a protector 10 is put on the mandrel.

Dorn with a protector is placed in the pins of the winding machine. Carry out layer-by-layer winding of the mesh floor beam with a unidirectional prepreg ribbon for ribs and a woven prepreg ribbon for monolithic sections. The floor beams are wound using reverse studs - during the winding of each coil when it is turned (reversed) in the opposite direction, the prepreg tape engages for the reverse studs, which prevent the prepreg from slipping. Thus, the presence of reverse studs 18 allows you to reverse the prepreg tape without full coverage of the end face of the mandrel, which increases the utilization of the material. The PCM floor beam is wound as follows.

First, sequential winding of the first layers of all the ribs in any sequence is carried out. Moreover, the selected sequence on the first layer must be observed when winding the remaining layers of ribs. For definiteness, we choose the following winding sequence: spiral ribs, transverse ribs, longitudinal ribs.

After winding the first layer of spiral ribs, a first layer of longitudinal ribs and then a first layer of transverse ribs are wound. After that, in places of monolithic sections, one layer of woven prepreg is wound.

The formation of the first layer of spiral ribs occurs over several revolutions of the winding machine, until the first layers of all spiral ribs are formed. Upon completion of the formation of the first layer of spiral ribs, the prepreg tape is cut and proceed to winding the transverse ribs.

The first layer of the first transverse rib is formed in one revolution of the mandrel, after which the prepreg tape is cut and the first layer of the next transverse rib is also formed, etc. until the formation of the first layers of all transverse ribs.

The first layers of longitudinal ribs are wound in pairs. The winding of the first layer is started from the zone of one of the technological allowances, the winding of the longitudinal rib layer in the part zone is continued until the prepreg tape enters the technological allowance zone from the opposite side of the mandrel. Here, the mandrel prepreg is bent around the tape and returned to the part zone at the bottom of the mandrel. Then, the winding of the lower rib symmetrically located to the first longitudinal rib continues to the entrance to the technological allowance zone, from where the winding of the longitudinal rib layer begins. Here the prepreg tape is cut off. In the same way, the following pair of longitudinal ribs is wound until the completion of the winding of all the first layers of longitudinal ribs.

Then the first layers of monolithic sections are wound with a woven prepreg. The pattern of their formation is similar to the pattern of formation of transverse ribs. The difference is that the woven prepreg ribbon coincides with the width of the monolithic section, and when it is wound, the woven prepreg intersects not only with all the ribs in this zone, but also with the interlacing of these ribs. Further, everything is also repeated in layers, i.e. the second layers of spiral, transverse, longitudinal ribs and monolithic sections are successively laid on the first layers of spiral, transverse, longitudinal ribs and monolithic sections, respectively, then the third, fourth layers, etc. to the formation of a given thickness of the part.

Winding is performed on a winding machine type NMKE 442129.003.

After the winding process is completed, the mandrels with the workpiece are removed from the winding machine and placed in a vacuum bag (in the case of molding in an autoclave) or lavsan tapes are wound along geodetic lines (for molding in an oven).

The workpiece is placed in an autoclave (thermal furnace), where molding is performed under the temperature and pressure conditions necessary for curing the binder.

After the molding process is completed, the equipment with the cured workpiece is removed from the autoclave (thermal furnace) and cooled at room temperature. The mandrel with the workpiece is freed from the vacuum bag (lavsan tapes).

The last step is the removal of the product from the mandrel.

Cutting of the endings (technological allowances) in the area of the end face of the flanges 3, 4, adjacent to the pipes 1, 2. Carry out the dismantling of the long stud 6, remove it from the cavity of the mandrel 12. Carry the pins 11 in the holders of the device type hydraulic cylinder, where they apply force necessary to connect the hollow pipes and remove one of them from the tread, the second pipe is removed from the tread by pushing it from the surface of the pipe using a special device. They release the product from the tread by pushing it inside the floor beam, pressing on the tread, after which the tread is removed from the cavity of the product.

In this way, a mesh closed structure is obtained that forms a single floor beam structure.

The inventive method has a low complexity due to high-tech operations of removal of the product, the absence of machining operations. In addition, the method allows to obtain products of high quality, with high accuracy and good strength characteristics due to the accuracy of winding, due to the complex-lightweight design of the mandrel, the presence of reverse studs and the accuracy of the tread pattern.

Claims (1)

A method of manufacturing a mesh beam of a plane-structure aircraft glider from polymer composite materials, comprising placing a rubber-like tread on a mandrel with a system of spiral, longitudinal and transverse grooves, winding unidirectional prepreg tapes in the grooves of the protector, applying forming elements to the product blank, heat treatment, followed by removing the mandrel from a collapsible rubber-like tread, characterized in that the winding of unidirectional prepreg tapes in the grooves of the tread is made on the mandrel, in the form of two hollow pipes, strained in tension by a long stud, with flanges mounted on the ends, equipped with reverse studs and a closed-section protector made of rubber-like elastic material.

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