RU2460745C2 - Composition and method of producing binder, prepreg and cellular panel - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: binder contains the following (pts.wt): low-molecular epoxydiane resin 10-20, high-molecular epoxy resin 3-6, bis(N,N'-dimethylcarbamide)diphenyl methane 3-5, epoxy-novolac resin 15-25, tetrabromodiane-based epoxy resin 16-24 and solvent - a mixture of aliphatic alcohol and acetone in ratio 1:2 0-50. The binder is obtained by dispersing bis(N,N'-dimethylcarbamide) in a portion of low-molecular epoxydiane resin. The high-molecular epoxy resin is then fused with the remaining portion of the low-molecular epoxydiane resin, the epoxy-novolac resin and the tetrabromodiane-based resin at 130-150°C, and then mixed at 50-70°C with the obtained dispersion with addition the required amount of solvent. Prepregs are obtained from the binder and a fibre filler. The prepreg is used to make lining in a three-layer panel.

EFFECT: invention enables to obtain binder and a prepreg based on said binder and cellular panels, having self-extinguishing, high mechanical properties with minimum consumption of material, electric power and labour input.

6 cl, 6 tbl, 4 ex

Description

Technical field

The present invention relates to chemistry and technological processes, and more particularly to compositions of epoxy resins and layered products, and can be used in the manufacture of three-layer (sandwich) panels from polymer composite materials (PCM). This invention can find its application, in particular, in the floor panels of aircraft, which consist of composite honeycombs and composite cladding.

State of the art

Cellular panels have found a wide range of applications where high strength with low weight is required. Honeycombs and hard syntactic paste are used as lightweight and durable aggregate in many sandwich designs. Honeycombs are a very popular aggregate due to indicators such as the ratio of high strength to low weight and high resistance to fatigue loads. A wide variety of materials, including metals and composite materials, are used to make honeycomb core.

The skin that adheres to the ends of the honeycomb core can be made from a wide range of materials, including various PCMs. An important point in the molding of any sandwich panel is how the skin adheres to the honeycomb core. Usually, adhesive methods are used to connect the skin to the honeycombs. Adhesives must firmly attach the skin to the honeycomb in order to appropriately distribute the loads from one surface to another and allow the structure to fulfill all the intended loads in accordance with the strength parameters used in the calculation. If the adhesive is weak in terms of performance, then this significantly affects the strength of the panel. Adhesive is one of the critical components of a sandwich panel that uses honeycomb core because the cells have a relatively small contact area at the interface with the skin.

One way to use honeycomb composite sheathing involves preparing a prepreg, which consists of a fibrous filler and an uncured resin. Prepreg is a term from the composite materials industry that refers to fabric, non-woven fabric, tows or rovings that are pre-impregnated with a thermosetting resin and that are ready for the final cure stage. An adhesive film is usually added after curing the prepreg for subsequent bonding to the honeycombs (separate molding) or simultaneously curing the prepreg and the adhesive itself in an assembly with honeycomb (combined molding). The adhesive film can be used as an intermediate layer or as an integral part of the prepreg.

They use various methods of reducing the weight of cellular sandwich panels without reducing the structural strength. One of the methods used to reduce weight is the exclusion of a separate adhesive layer. This problem is solved by the manufacture of casing of prepregs, which are self-adhesive. The binder, which is used in such self-adhesive prepregs, must satisfy two requirements: to ensure high strength of the casing, while at the same time supporting its strong bonding with honeycomb core. Self-adhesive claddings are described in detail and published in European patents EP 0927737 A1 and EP 0819723 A1 and U.S. Pat. Nos. 6,440,257; and 6,508,910.

Cellular sandwich panels are used as floor panels in aircraft fuselages. Floor panels are classified according to their area of use. For example, passenger aircraft typically include four types of floor panels: 1) sub-seat panels, 2) aisle panels, 3) I / O panels and kitchens, 4) heavily loaded panels. Physico-mechanical characteristics of the panels are very dependent on various loads in the process of their use. For example, aisle and sub-seat panels tend to be light and not as strong as kitchen panels or heavily loaded luggage panels, etc.

It is known that a decrease in its total mass is important in the design of any aircraft. It is important to make the panels as light as possible while preserving the various structural characteristics that are required for a particular type of floor panel. Even a small change in the surface (kg / m ² ) density of the floor panel will affect the relative change in the total take-off weight of the aircraft. Thus, it is necessary to make floor panels light in weight and with structural requirements that ensure their use in various types of aircraft and their specific areas.

Known RF patent 2055723 "Multilayer panel", intended for use in the aircraft, ship, automotive, construction, furniture and sports equipment.

A multilayer panel is known that contains outer layers made on the basis of a fibrous semi-finished product and layers of aggregate, for example, honeycomb placed between them, interconnected by adhesiveless thermoforming using thermoplastic binder contained in the form of thermofusible fibers in the structure of the outer layers.

It is known [1] that thermoplastic adhesive joints are not strong enough, therefore, the use of such structures is permissible in the form of finishing material in construction, furniture production, sports equipment. Thermoforming panels based on thermoplastic binders requires high pressures and temperatures, which requires special expensive equipment.

In the aircraft industry for the manufacture of structural elements of the interior of a passenger aircraft, panels from the materials specified in the invention cannot be used because of the high combustibility, heat and smoke during combustion [2], which do not meet the requirements of aviation standards [3].

Known RF patent 1445163 "Method for producing an epoxy composition."

The invention relates to a method for producing an epoxy binder for producing prepregs and polymer composite materials with self-extinguishing properties, in particular, can be used in the manufacture of honeycomb structures. However, the presence of a low molecular weight resin DEG-1 (diglycidyl ether of diethylene glycol) completely excludes the possibility of using prepregs based on this composition in the production of honeycomb structures by the combined molding method. When the temperature rises above 90 ° C, i.e. prior to curing at 125 ± 5 ° С, the binder from the upper skin will drain along the walls of the honeycomb and at the same time, the adhesive strength of this skin to the honeycomb is not sufficient for operation.

Known patent of the Russian Federation 2250830 "Design of a cellular panel."

The invention relates to the aviation industry for the production of various cellular interior panels with self-extinguishing properties, as well as with ends filled with syntactic paste (microspheroplast).

A known design of the honeycomb panel, consisting of the upper and lower skin of organite 7TL-B (0) -2-Sh, glued to the honeycomb core with VK-46 film, while the ends of the panel are filled with paste VPZ-1-55.

The disadvantage of this method is the use of separate molding of the skin and gluing them with honeycomb, while the materials used are limited to 7TL-B (0) -2Sh Organite and VK-46 glue. Such panels have a limited range of applications, extremely expensive due to the use of the above materials. The manufacturing method is multi-cycle, labor-intensive and energy-intensive. In general, the production of such panels is unprofitable, and their use is limited.

Known blanks of floor panels manufactured by ONPP "Technology" according to TU 1-596-417-01 [4]. Honeycomb panels with fiberglass cladding based on fiberglass T-10-80 and adhesive EP-2MK. The disadvantage of these panels is the high mass and low bending strength and extremely high deflection when bending a long beam according to OST 1.90265-78. Prepregs based on the used binder EP-2MK are not technologically advanced in processing (too high stickiness and low viability), and also require a long, high-temperature heat treatment: 4-6 hours at T = 160-170 ° С.

Closest to the proposed invention in technical essence and the achieved result is a composition for producing a binder for prepregs, a method for producing a binder for prepregs, prepreg and the product according to RF2176255 "Composition for producing a binder for prepregs, a method for producing a binder for prepregs, prepreg and product".

According to the invention, an epoxytriphenol resin, a low molecular weight epoxidian resin, hardeners-dicyandiamide and bis (N, N′-dimethylcarbamide) diphenylmethane in a weight ratio of (50-60) :( 25-35) :( 4-10) are taken to prepare a binder for prepregs : (3-4) :( 4-6) and, possibly, the solvent is a mixture of aliphatic alcohol with acetone in a mass ratio of 3: 5 in an amount of 0-82 (parts by weight).

A method for producing a binder for prepregs, which consists in mixing a pre-prepared paste - a mixture of hardeners crushed to a particle size of 3-5 μm with a part of a molten low molecular weight epoxy resin - followed by combining the paste with an alloy of the remaining part of the low molecular weight epoxy resin, epoxytriphenol resin and high molecular weight epoxy resin and , if necessary, a solvent.

The prepreg contains the proposed epoxy binder and fibrous filler in the ratio (30-42) :( 58-70) wt.%, Respectively. As a filler, glass, carbon, organic tows, ribbons, fabrics and threads, as well as their combinations, are used.

The disadvantage of this composition and manufacturing method is: the absence of flame retardants in the binder composition (products that reduce the combustibility of the material);

the hardener composition requires an increased (about 160 ° C) curing temperature; the content of a large amount of epoxytriphenol and low molecular weight diane gum, having high fluidity at elevated temperatures, makes it impossible to carry out combined molding and gluing of skin with honeycomb core.

Cell panels manufactured using the claimed composition and a prepreg based on it cannot be used in floor structures of aircraft and other vehicles because of their combustibility that does not meet the requirements of AP-25 [3]. Their manufacturing process is possible only by separate molding using an additional adhesive film, which, as mentioned earlier, increases labor intensity, energy consumption, and also reduces production productivity and profitability.

SUMMARY OF THE INVENTION

The objective of this invention is to develop the composition of the binder and prepregs based on it, with a combination of self-extinguishing and self-adhesive properties, for the manufacture by combined molding of honeycomb floor panels with high resistance to bending loads, having reduced energy intensity and high manufacturability.

In addition, products made using a binder, such as honeycomb panels, must be highly technological and fireproof.

Moreover, the binder and production technology of the products must ensure their high quality.

The problem is solved in that:

in the composition and method of manufacturing a binder, prepreg and honeycomb panel, a binder was used including: epoxy resin, high molecular weight epoxy resin, bis (N, N'-dimethyl carbamide) diphenylmethane and solvent - a mixture of aliphatic alcohol and acetone in a ratio of 1: 2, the binder also contains an epoxy resin a resin and an epoxy resin based on tetrabromodian in the following ratio of components (parts by weight)

epoxy resin 15-25 tetrabromodian epoxy 16-24 low molecular weight epoxy resin 10-20 high molecular weight epoxy 3-6 bis (N, N′-dimethylcarbamide) diphenylmethane 3-5 solvent 0-50

in a method for producing a binder for prepregs by mixing the components with preliminary dispersion of bis (N, N'-dimethylcarbamide) in part of a low molecular weight epoxy resin, characterized in that the high molecular weight epoxy resin is first fused with the remaining part of the low molecular weight epoxy resin, an epoxy resin resin at a temperature of 130-150 ° C, and then at a temperature of 50-70 ° C combined with the resulting dispersion with the addition of the required amount of solvent;

in the prepreg, obtained on the basis of an epoxy binder and a fibrous filler in the form of glass, carbon, organic tows, ribbons, fabrics and (or) combinations based on them, the composition according to claim 1 is used as a binder in the following ratio of components (wt.%) :

epoxy binder 28-45

fibrous filler 55-72

and as a fibrous filler, 8/3 satin weave fiberglass from high-modulus aluminosilicate fiber is used;

in a three-layer panel, consisting of the middle layer of polymersotoplast and sheaths of polymer composite material, sheaths are made of the above prepreg, during assembly of the panel before molding, individual sections and edges of the polymersoplast are filled with syntactic paste, which is then cured as part of the panel.

The invention allows to produce prepregs with self-adhesive properties, providing high strength and fire safety of the honeycomb panels made from them with minimal materials, energy and labor costs, and the honeycomb panels made according to this invention, with close and even better weight parameters, have higher mechanical properties by the results of special tests conducted for the floor panels of passenger aircraft and characterizing the operational loads perceived by them.

The implementation of the invention

1. According to the invention, as components of an epoxy self-adhesive binder with reduced flammability are used:

- epoxynovolac resins EN-6 and UP-643 (glycidyl ethers of novolacs SF-0121 and SF-0113), manufactured according to TU 2225-11131395-2003;

- an epoxy resin based on tetrabromdian under the brand name UP-631, manufactured according to TU 2225-652-11131395-2008;

- epoxidian resins ED-22, ED-20, manufactured in accordance with GOST 10587-84;

- high molecular epoxy resins: diaplast (TU 2225-386-11131395-97) and E-49P (TU 210-1592-76);

- bis (N, N′-dimethylcarbamide) diphenylmethap - hardener No. 9, TU 2494-480-04872688-2006;

- solvent - a mixture of acetone and aliphatic alcohol (ethyl or isopropyl) in a ratio of 2: 1 to 1: 2.

2. The preparation of the binder is carried out in mechanical mixing mixers with two mixers: high-speed gear (dispersant) and low-speed (frame). The mixer must be equipped with:

a heating jacket, a reflux condenser and a vacuum system, for example, SPEMP-270.03-VK-R70 manufactured by NPP Dispod LLC.

3. Preparation of the prepreg is carried out from fabrics and tapes using mortar technology on vertical-type impregnating machines, for example, UPST-100M, UPST-300, or from rovings and harnesses using melt technology at installations of the type УОЛ-300 manufactured by OJSC SAVMA.

4. For the manufacture of the prepreg according to claim 4, 8/3 satin weave fiberglass is used from high-modulus VMP grade aluminum-magnesium silicate fiber. Fiberglass under the brand name T-10 (VMP) -4C is produced in accordance with TU 5952-183-05786904-04 NPK Term.

5. The middle layer of the three-layer panel is made of medium and high density polymersoplast of domestic or foreign production.

The formation of three-layer panels is carried out in a multi-storey hydraulic press with plates heated by thermal oil.

6. Filling of individual sections of the honeycomb core is carried out with syntactic paste consisting of a non-combustible epoxy binder and glass microspheres, for example, VP3-7M (TR 1.2.924-84 FSUE VIAM). The paste cured in the composition of the three-layer panel is a hard microspheroplastic with a compressive strength of 4.0-5.0 MPa.

Example 1

Hardener 9 (3.0 parts by weight) with ED-20 epoxy resin (6 parts by weight) is dispersed in a mixer with a high-speed gear and low-speed frame mixer to a finely divided state. Stirring is carried out under a vacuum of 0.6 ± 0.1 kgf / cm and a temperature of 50 ± 5 ° C for 60 ± 30 minutes. The resulting adduct is poured into polyethylene jars with a wide lid and stored at a temperature of 20 ± 5 ° C for no more than 3 months or in a refrigerator for up to 1 year.

An ED-20 epoxy resin (4 parts by weight), UP-643 epoxy resin (25 parts by weight), UP-631 bromidine resin (16 parts by weight) are heated at a stirring to 140-150 ° C, add resin E-49 (3.0 parts by weight) in portions and mix for 2-3 hours. The resulting precondensate is cooled to a temperature of 60 ° C, alcohol-acetone mixture 2: 1 is added to the desired concentration (for example, 50 parts by weight) and the previously obtained adduct (9.0 parts by weight), after which the components are mixed for 90 ± 30 min at a temperature of 60 ± 5 ° C.

The resulting binder is cooled to room temperature and poured into tightly closed glass bottles or galvanized jars. The resulting binder is stored at a temperature not lower than 15 ° C and not more than 3 months. to avoid crystallization and precipitation of the resin UP-631.

In case of precipitation, the binder is subjected to stirring again at a temperature of 50-60 ° C until the precipitate completely disappears.

Binder Properties:

The density at 20 ° C is 1.05 ± 0.01 g / cm ² .

Gelling time at 20 ° C for at least 12 minutes

The resulting solution of the proposed binder is impregnated with a woven fibrous filler, followed by removal of the solvent by drying at a temperature of not more than 90 ° C to a residual solvent content of 0.3-2.0 wt.% In the prepreg.

The prepregs thus obtained retain their rheokinetic properties, i.e. viability for further processing at a temperature of no higher than + 25 ° C for at least 3 months and at least 1 year at a temperature of no higher than -8 ° C.

The obtained prepregs are used in the manufacture of honeycomb panels by the method of combined hot pressing. The lower skin is laid out of the prepreg on a metal sheet treated with release grease, a honeycomb core is laid on top of the skin, cut into sheets of a predetermined height, the upper skin and a metal sheet treated with release grease are laid on top of the honeycomb.

The package thus assembled is placed between the heated plates of the hydraulic press. The molding pressure is applied at a rate of 2 to 4 kgf / cm of moldable panel. Pressure curing is carried out at 130 ± 5 ° С for at least 2 hours. Press plates are cooled under pressure to 60 ± 10 ° C, and the finished panels are removed from the press.

Note: It is allowed with a high-quality surface of press plates to process them with a release compound and not to use additional metal sheets (so-called tsulagi).

Depending on the purpose and location in the passenger cabin of the aircraft, the panels are made of 4 types.

Type 1 - a three-layer panel with sheathing of 2 layers of prepreg based on the proposed binder and fiberglass T-10-14, and the content of the binder in the layer adjacent to the honeycombs is 39 ± 3 wt.%, And in the outer layer - 33 ± 3 wt.%. As a filler, sotoplast with a density of 60 to 100 kg / m ^{3 is used} .

Type 2 - a honeycomb panel manufactured similarly to a Type 1 panel, but using a honeycomb with a density of 120 to 155 kg / m ³ .

Type 3 - a honeycomb panel made similarly to type 2, but containing in each skin an additional one layer of prepreg with a binder content of 33 ± 3 wt.%.

Type 4 - a honeycomb panel, manufactured similarly to type 2, but containing in the upper skin an additional 2 layers of prepreg with a binder content of 33 ± 3 wt.%.

The parameters and mechanical properties of the resulting panels are shown in table 1.

Table 1 Metric indicators of honeycomb panels in example 1 Type of Panel Assignment The number of layers in the casing upper / lower Weight 1 m of the panel, kg Panel Thickness, mm I Sub-area 2/2 2.5 ± 0.1 10.15 ± 0.15 II Aisle area 2/2 3.2 ± 0.1 10.15 ± 0.15 III Buffet I / O Area 3/3 4.2 ± 0.1 10.45 ± 0.15 IV Cargo and luggage compartment area 4/2 4.2 ± 0.1 10.45 ± 0.15

Table 3 shows the comparative characteristics of the panels made on the basis of the proposed binder and various fiberglass fabrics. Fiberglass T-10-14 is made of aluminoborosilicate fiber and is also used in floor panels produced by ONPP Technologiya according to TU 1-596-417-01, fiberglass T-10-14 along with fiberglass T-10 (VMP) -4C is offered to use in this invention in example 2.

Table 3 A comparative level of elastic-strength characteristics of samples of cellular floor panels based on the proposed binder of various fiberglass fabrics in comparison with the requirements of aircraft manufacturers. Panel Type Fiberglass Cladding The fracture force when punching the skin, N Deflection when bending a long beam, 450 N, mm Customer requirements Actual according to the invention Customer requirements Actual according to the invention one T-10-14 Example 1 1200-2200 1380 18.0-12.0 16.7 T-10 (VPM) Example 2 2610 12.8 2 T-10-14 Example 1 2000-3000 2080 16.0-10.0 16,0 T-10 (VPM) Example 2 3300 10.0 3 T-10-14 Example 1 2500-3500 2210 10.0-7.0 10.5 T-10 (VPM) Example 2 3720 6.7

Example 2

Analogously to example 1, produce a 60% solution of epoxy binder in the following ratio of components, parts by weight:

epoxynolac resin EN-6 eighteen epoxy resin ED-22 16 bromidian resin UP-631 eighteen high molecular weight diane resin - diaplast four hardener 9 four alcohol-acetone mixture 1: 1 40

Storage of the binder is carried out analogously to example 1.

Using the obtained binder, prepregs are made on the basis of fiberglass T-10 (VMP) -4C. The properties of the obtained prepregs are shown in table 4.

Table 4 The effect of qualitative indicators of the prepreg on the separation force of 2-layer casing based on it from the honeycomb core PSP-1-2,0-144 Fiberglass brand The binder content in the prepreg wt.% Prepreg stickiness The force of separation of the skin from cells, MPa Note T-10 (VMP) -4C 32 ± 1 Low 3.24 Bonding failure 36 ± 1 Satisfying 3.86 Mixed destruction, gluing + honeycomb 42 ± 1 High 4.32 Sotoplast destruction

From the obtained prepregs, honeycomb panels are made according to the technology described in paragraph 1. In contrast to item 1, before laying the prepreg of the upper skin, individual sections of the honeycomb according to the drawing on the panel according to the templates are filled with syntactic paste, for example VP3-7M, then the manufacturing process continues according to technology of item 1.

Depending on the purpose of the panel, three types are made:

Type 1 - with sheathing of 2 layers of a prepreg based on fiberglass T-10 (VMP) -4C, containing 36 ± 3% binder and polymer-plastic with a density of 95 ± 10 kg / m and a height of 10 ± 1 mm.

Type 2 - a honeycomb panel similar to a panel of type 1 with a honeycomb core with a density of 145 ± 15 kg / m.

Type 3 - a honeycomb panel similar to type 2, containing 3 layers of prepreg in the skin.

The properties of the honeycomb panels obtained in example 2 are shown in table 3.

Example 3

In the mixer-dispersant of a small capacity of 2-10 l load 4.5 wt.h. diaplast and 10 parts by weight resin ED-22, with stirring, bring the temperature to 140 ± 5 ° C and continue to mix at this temperature for 30-90 minutes until a homogeneous precondensate is formed. The speed of rotation of the dispersant is 50-1000 rpm, the frame mixer is 10-15 rpm.

In the mixer-dispersant of a larger volume of 30-100 l load 3.5 wt.h. hardener No. 9 and 18 parts by weight resin UP-631, add 30 wt.h. solvent - a mixture of acetone with alcohol in a ratio of 2: 1 and produce dispersion at normal temperature for 30-60 minutes The speed of rotation of the dispersant 1000-3000 rpm, frame mixer - 10-40 rpm

The previously prepared precondensate is added to the resulting suspension, the small mixer is washed with a solvent residue of 10 m.h. and the wash solution is poured into a large mixer. Bring the temperature to 60 ± 5 ° C, add 24 wt.h. resins EN-6 and mix for 60-120 minutes to obtain a stable binder solution.

Storage and use of the obtained binder is carried out analogously to examples 1 and 2.

Example 4

Analogously to example 1, a binder melt is obtained without adding a solvent in the following ratio of components, parts by weight:

epoxynolac resin EN-6 fifteen epoxy resin ED-22 twenty bromidian resin UP-631 24 high molecular weight diane resin - diaplast 6 hardener 9 5 alcohol-acetone mixture 1: 2 0

Hot-melt (melt) binder is stored in a tightly closed container with a wide neck for 3 months at room temperature and up to one year in a refrigerator.

Binder Properties:

Kinematic viscosity at 20 ° C (3-4) * 10 ⁴ MPa Kinematic viscosity at 70 ° C (0.8-1.2) * 10 ⁴ MPa Gelatinization time at 120 ° C not less than 12 min

The resulting binder is used to obtain a unidirectional prepreg, for example, based on glass roving ECB 1260N-78 or RVMPN-1260-78 on a horizontal impregnation machine.

The binder molten in a spunbond device is poured through a slotted gap onto a transporting release liner, combined with fibrous material and alternately (2-3 cycles) is heated on a heated table and rolled in hot calendars, then the prepreg thus obtained is cooled and wound into rolls.

The high bonding strength of the casing with honeycomb in all the examples (tables 2,4,6), which in most cases leads to the destruction of the latter, is achieved due to the optimal ratio of the binder with high viscosity epoxy resin and high molecular weight epoxy with low molecular weight low viscosity epoxy resin and obtained on the basis of the proposed binder, the so-called self-adhesive prepregs.

The properties of the obtained prepregs are shown in table 5.

Table 5 Properties of unidirectional prepregs based on glass roving and melt binder The binder content, wt.% Weight 1 m ² , g Thickness mm Appointment EC13-1260N-78 28 ± 2 250 ± 10 0.22 ± 0.1 Outer layers 55 ± 2 130 ± 10 0.18 ± 0.1 Inner layers RVPN- 28 ± 2 270 ± 10 0.22 ± 0.1 Outdoor 1260-78 Layers 55 ± 2 150 ± 10 0.18 ± 0.1 Inner layers

From the obtained prepregs, honeycomb panels are made in the same way as in claim 1. The properties of the resulting panels are shown in table 6.

Table 6 Properties of three-layer panels based on unidirectional prepregs (shown for type 2). Brand roving The binder content in the casing, outer / inner
Nya, wt.% The force of separation of the skin of cells, MPa The force of punching the sheathing with an incenter, diam. 12 mm, N ESB131260N-78 28/55 4.08 (cell destruction) 2150 RVMPN-1260-78 28/55 4.14 (cell destruction) 3180

Use, effectiveness.

The proposed binder is universal, that is, it can be used to obtain prepregs for solution and melt technologies; based on textile and unidirectional fibrous fillers made of fibers of various nature glass-, organo-, and carbon, as well as their combinations (hybrid prepregs).

The invention allows the production of prepregs with self-adhesive properties, providing high strength and fire safety of the honeycomb panels made from them with minimal consumption of materials, electricity and labor.

Cell panels made according to this invention with close and even better weight parameters have higher mechanical properties according to the results of special tests carried out for the floor panels of passenger aircraft and characterizing the operational loads perceived by them.

The proposed binder, prepreg and honeycomb panels can be made from components of domestic production, which, with equal technical parameters with foreign analogues, can reduce the cost of their production.

Cellular panels made of prepregs based on a binder of the fire safety proposed in this invention comply with AP-25 and NLGS standards.

The present invention solves the problem of creating new aviation structures, materials and technologies, in particular, can be used in the manufacture of the passenger compartment floor panel, which is a panel comprising a polymer honeycomb core and cladding of self-extinguishing fiberglass epoxy based on a self-adhesive binder and fibrous filler in the form fabrics or rovings.

The panels are manufactured using prepreg adhesiveless technology for combined bonding, that is, a package of honeycomb core with prepreg casing based on fibrous filler and an epoxy modified self-extinguishing binder is formed. The assembled package is placed between the heated plates of the hydraulic press and is molded at a pressure of 2 to 4 kgf / cm according to the temperature regime set for the developed binder.

The fire safety of the panels (compliance with the requirements of AP-25) is achieved by the introduction of tetrabromodian based epoxy resin binder.

To prevent the binder from swelling from the upper casing over the honeycomb to the lower one and to increase the bonding strength of the upper casing with the honeycombs, the content of the low molecular weight epoxy resin is reduced in the composition of the binder, and instead of the epoxytriphenol resin, a high viscosity epoxy resin is added to the binder.

For good bonding to the honeycomb core, the prepreg layers adjacent to the honeycomb core may contain a binder amount of 39 ± 3%, and the binder content is reduced to 33 ± 3% in the outer layers to increase the flexural rigidity of the panel.

To increase the resistance of the panels to water absorption and to strengthen them at the points of contact with the power elements of the airframe, as well as to place fasteners, individual sections and ends of the panels can be filled before molding with non-combustible syntactic paste based on glass microspheres.

The paste is filled into the honeycomb core cells before assembling the bag with the prepreg casing, which ensures a good fit and gluing of the casing on the paste-filled sections of the panel. Due to the fact that the filler is inside the cells of the honeycomb, its chipping from the panel is prevented during machining and operation.

Thanks to the technology used for pre-filling syntactic paste into honeycomb core cells and the technology of combined molding of skins and gluing them with honeycomb, the laboriousness of the panel manufacturing process, production cycle and cost are reduced due to the absence of expensive glue, a number of auxiliary materials used for separate molding, energy costs for production and , accordingly, the cost of the resulting panel.

Sources used

1. Kardashov D.A. Petrova A.P. Polymer adhesives. Creation and application. - M.: Chemistry, 1983.

2. Kopylov VV Novikov S.N. Oksentievich L.A. et al. / Ed. A.N. Pravednikova Polymeric materials with reduced combustibility. - M.: Chemistry, 1986. 224 p.

3. AP-25. Aviation Rules. Part 25.

4. TU 1-596-417-11 blanks of floor panels

5. V.A. Bobylev. Special epoxy resins for adhesives and sealants. Adhesives, sealants, technologies, No. 5, 2005

6. OST 1.90265-78 Plastics. Method for determining the bending strength of three-layer materials with honeycomb core.

7. TR 1.2.924-84 Preparation and use of polymer aggregates - VPZ-7 and VPZ 7M spheroplasts.

Claims (6)

1. The composition for producing a binder for the prepreg, containing epoxidian low molecular weight resin, high molecular weight epoxy resin, bis (N, N′-dimethylcarbamide) diphenylmethane and a solvent - a mixture of aliphatic alcohol and acetone in a ratio of 1: 2, characterized in that it also contains epoxynolac resin and an epoxy resin based on tetrabromodian in the following ratio of components, parts by weight:
epoxy resin 15-25 tetrabromodian epoxy 16-24 low molecular weight epoxy resin 10-20 high molecular weight epoxy 3-6 bis (N, N′-dimethylcarbamide) diphenylmethane 3-5 solvent 0-50 2. A method of producing a binder for prepregs by mixing the components according to claim 1 with preliminary dispersion of bis (N, N′-dimethylcarbamide) in the part of the low molecular weight epoxy resin, characterized in that the high molecular weight epoxy resin is first alloyed with the remaining part of the low molecular weight epoxy resin, epoxy resin , an epoxy resin based on tetrabromodian at a temperature of 130-150 ° C, and then at a temperature of 50-70 ° C is combined with the obtained dispersion with the possible addition of the required amount of vitorite. 3. The prepreg, obtained on the basis of an epoxy binder and a fibrous filler in the form of glass, carbon, organic strands of tapes, fabrics and / or combinations based on them, characterized in that the composition according to claim 1 is used as a binder in the following ratio of components, wt .%:
epoxy binder 28-45 fiberfill 55-72 4. The prepreg according to claim 3, characterized in that an 8/3 satin weave fiberglass of high modulus aluminosilicate fiber is used as the fibrous filler. 5. A three-layer panel consisting of a middle layer of polymersotoplast and casing made of a polymer composite material, characterized in that the casing is made of prepreg according to one of claims 3 and 4. 6. The three-layer panel according to claim 5, characterized in that during assembly of the panel prior to molding, the individual sections and edges of the polymers are filled with syntactic paste, which is then cured as part of the panel.