Fiberglass structures. Manufacturing of fiberglass structures. Strengthening building structures

Basic Concepts
Fiberglass - a system of glass threads knitted with thermosets (irreversible hardening resins).

Mechanisms of Strength—Adhesion between a Single Fiber and a Polymer (resin) adhesion depends on the degree of cleaning of the fiber surface from the sizing agent (polyethylene waxes, paraffin). The sizing is applied at the fiber or fabric manufacturing plant to prevent delamination during transport and technological operations.

Resins are polyester, characterized by low strength and significant shrinkage during hardening, this is their disadvantage. Plus - fast polymerization unlike epoxides.

However, shrinkage and rapid polymerization cause strong elastic stresses in the product and over time the product warps, the warping is insignificant, but thin products gives unpleasant glare to a curved surface - see any Soviet body kit for VAZs.

Epoxies hold their shape much more accurately, are much stronger, but are more expensive. The myth about the cheapness of epoxies is due to the fact that the cost of domestic epoxy resin is compared with the cost of imported polyester resin. Epoxies also benefit from heat resistance.

The strength of fiberglass - in any case, depends on the amount of glass by volume - the most durable with a glass content of 60 percent, however, this can only be obtained under pressure and temperature. IN "cold conditions" it is difficult to obtain durable fiberglass.
Preparation of glass materials before gluing.

Since the process consists of gluing fibers together with resins, the requirements for the fibers being glued are exactly the same as for gluing processes - thorough degreasing, removal of adsorbed water by annealing.

Degreasing, or removal of coupling agent, can be done in BR2 gasoline, xylene, toluene, and their mixtures. Acetone is not recommended due to the binding of water from the atmosphere and "getting wet» fiber surface. As a method of degreasing, you can also use annealing at a temperature of 300-400 degrees. In amateur conditions, this can be done like this: rolled fabric is placed in a workpiece from ventilation pipe or galvanized drainage and is cut into a spiral from an electric stove placed inside the roll; you can use a hair dryer to remove paint, etc.

After annealing, glass materials should not be exposed to air, since the surface of the fiberglass absorbs water.
Some words "craftsmen“The possibility of gluing without removing the sizing agent evokes a sad smile - no one would think of gluing glass over a layer of paraffin. Tales about how "resin dissolves paraffin” is even funnier. Spread the glass with paraffin, rub it, and now try to glue something to it. Draw your own conclusions))

Sticking.
The separating layer for the matrix is ​​the best polyvinyl alcohol in water, applied by spray and dried. It gives a slippery and elastic film.
You can use special waxes or wax mastics silicone-based, but you should always make sure that the solvent in the resin does not dissolve the separating layer by first trying it on something small.

When gluing, lay layer upon layer, rolling with a rubber roller, squeezing out excess resin, remove air bubbles by piercing with a needle.
Guided by the principle - there is always excess resin harmful - resin It only glues glass fibers together, but is not a mold-making material.
if the item high precision, such as a hood cover, it is advisable to introduce a minimum of hardener into the resin and use heat sources for polymerization, for example an infrared lamp or a household "reflector».

After hardening, without removing from the matrix, it is very desirable to heat the product evenly, especially at the stage "gelatinization» resin. This measure will relieve internal stress and the part will not warp over time. Regarding warping - I’m talking about the appearance of glare and not about changing sizes; sizes can change by only a fraction of a percent but still give strong glare. Pay attention to plastic body kits made in Russia - none of the manufacturers "is bothering» result - summer, stood in the sun, there were a couple of frosts in winter and... everything looked crooked... although the new one looked great.
In addition, with constant exposure to moisture, especially in places where there are chips, the fiberglass begins to come out, and gradually, being wetted with water, it simply fringes; sooner or later, water penetrating into the thickness of the material peels off the glass threads from the base (glass adsorbs moisture very strongly)
in a year.

The sight is more than sad, well, you see such products every day. What is made of steel and what is made of plastic is immediately obvious.

By the way, prepregs sometimes appear on the market - these are sheets of fiberglass already coated with resin; all you have to do is put them under pressure and heat them - they will stick together into beautiful plastic. But the technical process is more complicated, although I have heard that a layer of resin with a hardener is applied to prepregs and excellent results are obtained. I didn't do that myself.

These are the basic concepts about fiberglass; make a matrix in accordance with common sense from any suitable material.

I use dry plaster "rotband"It is processed perfectly, holds the size very accurately, after drying from water it is impregnated with a mixture of 40 percent epoxy resin with a hardener - the rest is xylene, after the resin has cured, such forms can be polished or. very durable and fit perfectly.

How to peel off a product from a matrix?
For many, this simple operation causes difficulties, even to the point of destruction of the form.

It’s easy to peel off - make a hole or several in the matrix before gluing, and seal it with thin tape. After making the product, blow compressed air into these holes one by one - the product will peel off and be removed very easily.

Again, I can say what I use.

Resin - ED20 or ED6
hardening agent - polyethylene polyamine, also known as PEPA.
Thixotropic additive - aerosil (at By adding it, the resin loses its fluidity and becomes jelly-like, very convenient) is added according to the desired result.
The plasticizer is dibutyl phthalate or castor oil, about a percent or a quarter of a percent.
Solvent - orthoxylene, xylene, ethyl cellosolve.
resin filler for surface layers - aluminum powder (hides fiberglass mesh)
fiberglass - asstt, or fiberglass mat.

Auxiliary materials - polyvinyl alcohol, silicone Vaseline KV
Thin polyethylene film is very useful as a separating layer.
It is useful to evacuate the resin after stirring to remove any bubbles.

I cut the fiberglass into the required pieces, then roll it up, place it in a pipe and calcinate the whole thing with a tubular heating element placed inside the roll, it calcinates overnight - it’s so convenient.

Yes, and here's another.
Do not mix epoxy resin with hardener in one container in an amount of more than 200 grams. It will heat up and boil in no time.

Express control of the results - on the test piece, when breaking, the glass threads should not stick out - the plastic break should be similar to the plywood break.
break any plastic from which the body kit is made or pay attention to the broken one - solid rags. This is the result "no» bond between glass and polymer.

Well, little secrets.
It’s very convenient to correct devections such as scratches or sinkholes: apply a drop of epoxy resin to the sink, then stick tape on top as usual (ordinary, transparent), level the surface using the highlights using your fingers or applying something elastic; after hardening, the adhesive tape comes off easily and gives a mirror-like surface. No processing is required.

Solvent reduces the strength of the plastic and causes shrinkage in finished product.
Its use should be avoided if possible.
aluminum powder is added only to the surface layers - it reduces shrinkage very much, the mesh characteristic of plastics appears to me then nothing, the amount reaches the consistency of thick sour cream.
Epoxies are processed worse than polyesters and this is their disadvantage.
the color after adding aluminum powder is not silver but metallic grey.
ugly in general.

The metal fastener glued into the plastic must be made of aluminum alloys or titanium - because... A very thin layer is applied to the embedded product silicone sealant, and fiberglass fabric, previously well annealed, is pressed against it. The fabric should stick but should NOT be soaked through. after 20 minutes, this fabric is moistened with resin WITHOUT SOLVENT and the remaining layers are glued to it. This "combat "technology As a silicone sealant, we used the Soviet KLT75 vibration-resistant compound, which is heat-resistant, frost-resistant, and resistant to salt water. Preparing the metal surface - wash the aluminum alloy in a clean solvent. pickle in a mixture of washing soda and washing powder, heating the solution to a boil, if possible, then dry it in a weak alkali, for example a 5% solution of caustic potassium or soda, with heat. warm up to 200-400 degrees. After cooling, glue in as quickly as possible.

The article talks about what properties fiberglass has and how applicable it is in construction and in everyday life. You will find out what components are needed to make this material and their cost. The article provides step by step videos and recommendations for the use of fiberglass.

Since the discovery of the effect of rapid petrification of epoxy resin under the action of an acid catalyst, fiberglass and its derivatives have been actively introduced into household products and machine parts. In practice, it replaces or supplements exhaustible Natural resources- metal and wood.

What is fiberglass

The operating principle underlying the strength of fiberglass is similar to reinforced concrete, and in appearance and structure it is closest to the reinforced layers of modern “wet” facade finishing. As a rule, the binder - composite, gypsum or cement mortar - tends to shrink and crack, not holding the load, and sometimes not even maintaining the integrity of the layer. To avoid this, a reinforcing component is introduced into the layer - rods, meshes or canvas.

The result is a balanced layer - the binder (in dried or polymerized form) works in compression, and the reinforcing component works in tension. From such layers based on fiberglass and epoxy resin, you can create three-dimensional products, or additional reinforcing and protective elements.

Fiberglass Components

Reinforcing component*. For the manufacture of household and auxiliary building elements, three types of reinforcing material are usually used:

1. Fiberglass mesh. This is a fiberglass mesh with a cell size from 0.1 to 10 mm. Since epoxy mortar is an aggressive medium, impregnated mesh is highly recommended for products and building structures. The mesh cell and thread thickness should be selected based on the purpose of the product and the requirements for it. For example, for reinforcing a loaded plane with a fiberglass layer, a mesh with a cell size of 3 to 10 mm, a thread thickness of 0.32-0.35 mm (reinforced) and a density of 160 to 330 g/cubic meter is suitable. cm.
2. Fiberglass. It's more perfect view fiberglass bases. It is a very dense mesh made of “glass” (silicon) threads. It is used to create and repair household products.
3. Fiberglass. It has the same properties as clothing material - soft, flexible, pliable. This component is very diverse - it differs in tensile strength, thread thickness, weaving density, special impregnations - all these indicators significantly affect the final result (the higher they are, the stronger the product). The main indicator is density, ranging from 17 to 390 g/sq. m. This fabric is much stronger than even the famous military cloth.

* The types of reinforcement described are also used for other work, but the product data sheet usually indicates their compatibility with epoxy resin.

Table. Prices for fiberglass (using the example of Intercomposite products)

Astringent. This is an epoxy solution - resin mixed with a hardener. Separately, the components can be stored for years, but when mixed, the composition hardens from 1 to 30 minutes, depending on the amount of hardener - the more of it, the faster the layer hardens.

Table. The most common grades of resin

Popular hardeners:

1. ETAL-45M - 10 cu. e./kg.
2. XT-116 - 12.5 cu. e./kg.
3. PEPA - 18 USD e./kg.

An additional chemical component is a lubricant, which is sometimes applied to protect surfaces from penetration of epoxy (for mold lubrication).

In most cases, the master studies and selects the balance of components independently.

How to use fiberglass in everyday life and in construction

In private, this material is most often used in three cases:

• for repairing rods;
• for equipment repair;
• for strengthening structures and planes and for sealing.

Repair of fiberglass rods

To do this, you will need a fiberglass sleeve and a high-strength resin grade (ED-20 or equivalent). The technical process is described in detail in this article. It is worth noting that carbon fiber is much stronger than fiberglass, which means that the latter is not suitable for repairing impact tools (hammers, axes, shovels). At the same time, it is quite possible to make a new handle or handle for equipment from fiberglass, for example, the wing of a walk-behind tractor.

Helpful advice. You can improve your tool with fiberglass. Wrap the handle of a working hammer, axe, screwdriver, saw with impregnated fiber and squeeze it in your hand after 15 minutes. The layer will ideally take the shape of your hand, which will significantly affect the ease of use.

Equipment repair

The tightness and chemical resistance of fiberglass allows you to repair and seal the following plastic products:

1. Sewer pipes.
2. Construction buckets.
3. Plastic barrels.
4. Rain tides.
5. Any plastic parts of tools and equipment that do not experience heavy loads.

Repair using fiberglass - step-by-step video

“Homemade” fiberglass has one irreplaceable property - it is precisely processed and maintains rigidity well. This means that from canvas and resin you can restore a hopelessly damaged plastic part, or make a new one.

Strengthening building structures

Fiberglass in liquid form has excellent adhesion to porous materials. In other words, it adheres well to concrete and wood. This effect can be realized by installing wooden lintels. A board on which liquid fiberglass is applied acquires an additional 60-70% strength, which means that a board twice as thin can be used for a lintel or crossbar. If strengthened with this material door frame, it will become more resistant to loads and distortions.

Sealing

Another method of application is sealing stationary containers. Reservoirs, stone cisterns, swimming pools covered with fiberglass on the inside are becoming increasingly positive properties plastic dishes:

• insensitivity to corrosion;
• smooth walls;
• continuous monolithic coating.

At the same time, the creation of such a coating will cost about 25 USD. e. for 1 sq. m. Real tests of products from one of the private mini-factories eloquently speak about the strength of the products.

Video: testing fiberglass

Of particular note is the possibility of repairing the roof. With a properly selected and applied epoxy compound, you can repair slate or tiles. With its help, you can model complex translucent structures made of plexiglass and polycarbonate - canopies, street lamps, benches, walls and much more.

As we found out, fiberglass is becoming a simple and understandable repair and construction material that is convenient to use in everyday life. With developed skill, you can create interesting products from it right in your own workshop.

Fiberglass profiles are visually known, standard profiles designed for various applications in construction and design, made of fiberglass.

Having the same external parameters as profiles from traditional materials, profiled fiberglass, has a number of unique characteristics.

Fiberglass profiles have one of the highest strength-to-weight ratios of any structural product, as well as excellent corrosion resistance. The products are highly resistant to ultraviolet radiation, a wide range of operating temperatures (-100°C to +180°C), as well as fire resistance, which allows the use of this material in various areas of construction, especially when operating in areas dangerous voltage, and in the chemical industry.

PRODUCTION OF GLASS PLASTIC PIPES AND PROFILES

The profiles are manufactured using the pultrusion method, a feature of the technology that This consists of continuous drawing of roving made of filament threads, pre-impregnated with a multicomponent system based on binders of various resins, hardeners, thinners, fillers, and dyes.

The fiberglass is impregnated with resin and then passed through a heated die of the desired shape, in which the resin hardens. The result is a profile of a given shape. Fiberglass profiles are reinforced on the surface with a special non-woven fabric (mat), thanks to which the products acquire additional rigidity. The profile frame is covered with fleece impregnated with epoxy resin, which makes the product resistant to ultraviolet radiation.

A feature of pultrusion technology is the production of straight products with a constant cross-section along the entire length.

The cross-section of the fiberglass profile can be any, and its length is determined in accordance with the wishes of the customer.

FRP structural profile comes in a wide range of shapes including I-beam, equal-flange, equal-flange, square pipe, round pipe, as well as a corner for laying when concreting the most different sizes, which can be used instead of a traditional metal corner, which is subject to rapid destruction from rust.

Most often, a fiberglass profile is made of orthophthalic resin.

Depending on the operating conditions, it is possible to produce profiles from other types of resins:

• - vinylester resin: intended for use in conditions where high corrosion resistance is required from the material;

- epoxy resin: has special electrical properties, making products made from it optimal for use in hazardous voltage areas;

- acrylic resin : products made from it have low smoke emission in case of fire.

GLASS PLASTIC PROFILES STALPROM

In our company you can purchase standard and non-standard fiberglass profiles of any size according to your wishes and requirements. The main list of fiberglass profiles is as follows:

	Corner The dimensions of this material may vary. They are used in almost all fiberglass structures. Structurally, they are used in fiberglass staircases, lighting installations, in the bases of bridges, and transitions made of fiberglass flooring. Corner symbol: a – width, b – height, c – thickness.
	C-profile (C-profile) Due to their corrosion resistance, fiberglass C-profiles are used primarily in the chemical industry. Symbol for C-shaped profile: a – width, b – height, c – opening width, d – thickness.
	Fiberglass beam Can be used either as a part of an integrated solution, or as an independent structure (fiberglass railings). Beam symbol: a – width, b – height.
	I-beams Fiberglass I-beams are most often used as load-bearing structures, which cover large spans and are capable of carrying various loads. I-beams are optimal constructive solution as a basis for fiberglass flooring, staircases, lighting installations, walkways, etc. I-beam symbol: a – width, b – height, c – thickness.
	Profile "Hat" Used as an insulating profile mainly in the electronics industry. Profile symbol: a – width, b – size of the upper part of the profile, c – thickness.
	Rectangular pipes The products are capable of bearing both vertical and horizontal loads. Pipe designation: a – width, b – height, c – wall thickness.
	Fiberglass rod is used as fiberglass antenna, sun umbrellas, profiles in model making, etc. Bar symbols: a – diameter.
	Taurus They are used as additional structures in fiberglass walkways, stages, load-bearing surfaces, etc. Brand symbols: a – height, b – width, c – thickness.
	Round pipe Such fiberglass pipes are not used in structures with internal pressure. Pipe symbols: a – outer diameter, b – internal diameter.
	Intended for use as the basis of a structure, such as a staircase, staircase or work platform, gangway. Channel symbols: a – width, b – height, c/d – wall thickness.
	Z-profile (Z-profile) Designed for use in gas cleaning facilities. Profile legend: a – width of the upper part of the profile, b – height, c – width of the lower part of the profile.
	The dimensions of this material may vary. They are used in almost all fiberglass structures.

Among the many new and varied structural synthetic materials, the most widely used for the construction of small ships are fiberglass plastics, consisting of fiberglass reinforcing material and a binder (most often based on polyester resins). These composite materials have a number of advantages that make them popular among designers and builders of small ships.

The process of curing polyester resins and producing fiberglass plastics based on them can occur at room temperature, which makes it possible to manufacture products without heat and high pressure, which, in turn, eliminates the need for complex processes and expensive equipment.

Polyester fiberglass plastics have high mechanical strength and, in some cases, are not inferior to steel, while having a much lower specific gravity. In addition, fiberglass plastics have a high damping capacity, which allows the boat hull to withstand large shock and vibration loads. If the impact force exceeds the critical load, then the damage in the plastic case is, as a rule, local and does not spread over a large area.

Fiberglass has a relatively high resistance to water, oil, diesel fuel, atmospheric influences. Fuel and water tanks are sometimes made from fiberglass, and the translucency of the material allows one to observe the level of the stored liquid.

The hulls of small ships made of fiberglass are usually monolithic, which eliminates the possibility of water penetrating inside; they do not rot, do not corrode, and can be repainted every few years. For sports boats, it is important to be able to obtain a perfectly smooth outer surface of the hull with low friction resistance when moving in water.

However, as a structural material, fiberglass also has some disadvantages: relatively low rigidity, a tendency to creep under constant loads; connections of fiberglass parts have relatively low strength.

Fiberglass plastics based on polyester resins are manufactured at temperatures of 18 - 25 0 C and do not require additional heating. Curing of polyester fiberglass takes place in two stages:

Stage 1 – 2 – 3 days (the material gains approximately 70% of its strength;

Stage 2 – 1 – 2 months (increasing strength to 80 – 90%).

To achieve maximum structural strength, it is necessary that the binder content in fiberglass is minimally sufficient to fill all the gaps of the reinforcing filler with the chain to obtain a monolithic material. In conventional fiberglass, the binder-filler ratio is usually 1:1; in this case, the total strength of glass fibers is used by 50 - 70%.

The main reinforcing fiberglass materials are strands, canvases (glass mats, chopped fiber and glass fabrics.

The use of woven materials using twisted glass fibers as reinforcing fillers for the manufacture of fiberglass hulls of boats and yachts is hardly justified both economically and technologically. On the contrary, nonwoven materials for the same purposes are very promising and the volume of their use is growing every year.

The cheapest type of material is glass strands. In the bundle, glass fibers are arranged in parallel, which makes it possible to obtain fiberglass with high tensile strength and longitudinal compression (along the length of the fiber). Therefore, strands are used to produce products where it is necessary to achieve predominant strength in one direction, for example, frame beams. When constructing buildings, cut (10 - 15 mm) strands are used to seal structural gaps formed when making various types of connections.

Chopped glass strands are also used for the manufacture of hulls of small boats and yachts, obtained by spraying fibers mixed with polyester resin onto an appropriate mold.

Fiberglass - roll materials with chaotic laying of glass fibers in the plane of the sheet - also made from strands. Fiberglass plastics based on canvas have lower strength characteristics than fiberglass plastics based on fabrics due to the lower strength of the canvases themselves. But fiberglass, cheaper, has a significant thickness with low density, which ensures their good impregnation binder.

Layers of fiberglass can be bonded in the transverse direction chemically (using binders) or mechanical stitching. Such reinforcing fillers are laid on surfaces with a large curvature more easily than fabrics (fabric forms folds and requires preliminary cutting and adjustment). Hopsts are used primarily in the manufacture of hulls of boats, motorboats, and yachts. In combination with fiberglass fabrics, canvases can be used for the manufacture of ship hulls, which are subject to higher strength requirements.

The most responsible structures are made on the basis of fiberglass. Most often, satin weave fabrics are used, which provide a higher utilization rate of the strength of the threads in fiberglass.

In addition, fiberglass tow is widely used in small shipbuilding. It is made from untwisted threads - strands. This fabric has greater weight, lower density, but also lower cost than fabrics made from twisted threads. Therefore, the use of rope fabrics is very economical, taking into account, moreover, the lower labor intensity when molding structures. In the manufacture of boats and boats, rope fabric is often used for the outer layers of fiberglass, while the inner layers are made of hard fiberglass. This achieves a reduction in cost of the structure while simultaneously ensuring the necessary strength.

The use of unidirectional rope fabrics, which have predominant strength in one direction, is very specific. When molding ship structures, such fabrics are laid so that the direction of greatest strength corresponds to the greatest effective stresses. This may be necessary in the manufacture of, for example, a spar, when it is necessary to take into account the combination of strength (especially in one direction), lightness, taper, varying wall thickness and flexibility.

Nowadays, the main loads on the spar (in particular, on the mast) act mainly along the axes; it is the use of unidirectional tow fabrics (when the fibers are located along the spar that provides the required strength characteristics. In this case, it is also possible to manufacture the mast by winding the tow onto a core (wooden, metal etc.), which can subsequently be removed or remain inside the mast.

Currently, the so-called three-layer structures with lightweight filler in the middle.

Tpex-layer construction consists of two outer load-bearing layers made of durable sheet material of small thickness, between which is placed a lighter, although less durable aggregate. Provide the purpose of the filler working together and stability of the load-bearing layers, as well as maintaining the specified distance between them.

The joint operation of the layers is ensured by their connection with the filler and the transfer of forces from one layer to another by the latter; the stability of the layers is ensured, since the filler creates almost continuous support for them; the required distance between layers is maintained due to sufficient rigidity of the filler.

Compared to traditional single-layer ones, the three-layer structure has increased rigidity and strength, which makes it possible to reduce the thickness of shells, panels and the number of stiffeners, which is accompanied by a significant reduction in the weight of the structure.

Three-layer structures can be made from any materials (wood, metal, plastics), but they are most widely used when using polymer composite materials, which can be used both for load-bearing layers and for filler, and their connection to each other is ensured by gluing.

In addition to the possibility of reducing weight, three-layer structures have other positive qualities. In most cases, in addition to their main function of forming a hull structure, they also perform a number of others, for example, they impart thermal and sound insulation properties, provide a reserve of emergency buoyancy, etc.

Three-layer structures, due to the absence or reduction of set elements, make it possible to more rationally use the internal volumes of the premises, lay electrical routes and some pipelines in the core itself, and make it easier to maintain cleanliness in the premises. Due to the absence of stress concentrators and the elimination of the possibility of fatigue cracks, three-layer structures have increased reliability.

However, it is not always possible to ensure a good bond between the load-bearing layers and the filler due to the lack of adhesives with the necessary properties, as well as insufficient careful adherence technological process gluing. Due to the relatively small thickness of the layers, their damage and filtration of water through them, which can spread throughout the entire volume, are more likely.

Despite this, three-layer structures are widely used for the manufacture of hulls of boats, boats and small vessels (10 - 15 m long), as well as the manufacture of separate structures: decks, superstructures, deckhouses, bulkheads, etc. Note that the hulls of boats and boats, in of which the space between the outer and internal cladding filled with polystyrene foam to ensure buoyancy, strictly speaking, they cannot always be called three-layer, since they are not flat or curved three-layer plates with a small thickness of the filler. It is more correct to call such structures double-sheathed or double-hulled.

It is most advisable to make elements of deckhouses, bulkheads, etc., which usually have flat, simple shapes, in a three-layer design. These structures are located in the upper part of the hull, and reducing their mass has a positive effect on the stability of the vessel.

The currently used three-layer ship structures made of fiberglass can be classified according to the type of filler as follows: with a continuous filler made of polystyrene foam, balsa wood; with honeycomb core made of fiberglass, aluminum foil; box-shaped panels made of polymer composite materials; combined panels (box-shaped with polystyrene foam). The thickness of the load-bearing layers can be symmetrical or asymmetrical relative to the middle surface of the structure.

By manufacturing method three-layer structures can be glued, with a foaming filler, molded on special installations.

The main components for the manufacture of three-layer structures are: glass fabrics of the T – 11 – GVS – 9 and TZhS-O,56-0 brands, fiberglass meshes of various brands; polyester resins marui PN-609-11M, epoxy resins grade ED - 20 (or other grades with similar properties), foam plastics grades PVC - 1, PSB - S, PPU-3s; fire-resistant laminated plastic.

Three-layer structures are made monolithic or assembled from individual elements(sections) depending on the size and shape of the products. The second method is more universal, as it is applicable to structures of any size.

The manufacturing technology of three-layer panels consists of three independent processes: production or preparation of load-bearing layers, production or preparation of filler and assembly and gluing of panels.

The load-bearing layers can be prepared in advance or directly during the formation of the panels.

The aggregate can also be applied either in the form of finished boards or foamed by increasing the temperature or by mixing the appropriate components during the production of the panels. Honeycomb core is manufactured at specialized enterprises and supplied in the form of cut slabs of a certain thickness or in the form of honeycomb blocks that require cutting. Tile foam is cut and processed on carpentry band saws or circular saws, thickness planers and other woodworking machines.

The decisive influence on the strength and reliability of three-layer panels is exerted by the quality of gluing of the load-bearing joints with the filler, which, in turn, depends on the quality of the preparation of the bonded surfaces, the quality of the resulting adhesive layer and adherence to gluing conditions. The operations of preparing surfaces and applying adhesive layers are discussed in detail in the relevant literature on gluing.

For gluing load-bearing layers with honeycomb core, adhesives of the BF-2 (hot-curing), K-153 and EPK-518-520 (cold-curing) brands are recommended, and with tile foams, adhesives of the K-153 and EPK-518-520 brands are recommended. The latter provide higher bonding strength than BF-l glue and do not require special equipment to create the required temperature (about 150 0 C). However, their cost is 4 - 5 times higher than the cost of BF - 2 glue, and the curing time is 24 - 48 hours (curing time of BF - 2 - 1 hour).

When foaming foam plastics between the load-bearing layers, applying adhesive layers on them, as a rule, is not required. After gluing and the necessary exposure (7 - 10 days), mechanical processing of the panels can be carried out: trimming, drilling, cutting holes, etc.

When assembling structures from three-layer panels, it should be taken into account that in the joints the panels are usually loaded with concentrated loads and the joints must be reinforced with special inserts made of a material that is denser than the filler. The main types of connections are mechanical, molded and combined.

When fastening saturation parts on three-piece structures, it is necessary to provide internal reinforcements in the fastener, especially when using mechanical fasteners. One of the methods of such strengthening, as well as the technological sequence of the unit, is shown in the figure.

A relatively large effect is achieved by using fiberglass structures exposed to various aggressive substances that quickly destroy ordinary materials. In 1960, about $7.5 million was spent on the production of corrosion-resistant fiberglass structures in the USA alone (the total cost of translucent fiberglass plastics produced in the USA in 1959 was approximately $40 million). Interest in corrosion-resistant fiberglass structures is explained, according to companies, primarily by their good economic performance. Their weight is much less than steel or wooden structures, they are much more durable than the latter, easy to erect, repair and clean, can be made on the basis of self-extinguishing resins, and translucent containers do not require water meter glasses. Thus, a serial tank for aggressive environments with a height of 6 m and a diameter of 3 m weighs about 680 kg, while a similar steel tank weighs about 4.5 tons. The weight of an exhaust pipe with a diameter of 3 m and a height of 14.3 m intended for metallurgical production, forms part of the weight steel pipe with the same load-bearing capacity; Although a fiberglass pipe was 1.5 times more expensive to manufacture, it is more economical than steel, since, according to foreign companies, the service life of such structures made of steel is calculated in weeks, from of stainless steel- for months, similar structures made of fiberglass have been in operation for years without damage. Thus, a pipe with a height of 60 m and a diameter of 1.5 m has been in operation for seven years. The previously installed stainless steel pipe lasted only 8 months, and its production and installation cost only half as much. Thus, the cost of a fiberglass pipe paid for itself within 16 months.

An example of durability in conditions aggressive environment There are also containers made of fiberglass. Such containers can be found even in traditional Russian baths, since they are not influenced by high temperatures, more information about various quality equipment for baths can be found on the website http://hotbanya.ru/. Such a container with a diameter and height of 3 m, intended for various acids (including sulfuric), with a temperature of about 80 ° C, is operated without repair for 10 years, serving 6 times longer than the corresponding metal one; the repair costs alone for the latter over a five-year period are equal to the cost of a fiberglass container. In England, Germany and the USA, containers in the form of warehouses and water tanks of considerable height are also widespread. Along with the indicated large-sized products, in a number of countries (USA, England), pipes, sections of air ducts and other similar elements intended for operation in aggressive environments are mass-produced from fiberglass.