Fiberglass reinforcement for corrosion-resistant marine concrete structures. Reliable fiberglass structures How to use fiberglass in everyday life and in construction
Among the many new various structural synthetic materials, the most widely used for the construction of small vessels are fiberglass plastics, consisting of a fiberglass reinforcing material and a binder (most often based on polyester resins). These composite materials have a number of advantages that have made them popular among designers and builders of small craft.
The process of curing polyester resins and obtaining glass-reinforced plastics based on them can occur at room temperature, which makes it possible to manufacture products without heating and high pressure, which, in turn, eliminates the need for complex processes and expensive equipment.
Polyester glass-reinforced plastics have high mechanical strength and are not inferior, in some cases, to steel, while having a much lower specific gravity. In addition, fiberglass has a high damping capacity, which allows the bottom hull to withstand high shock and vibration loads. If the impact force exceeds the critical load, then the damage in the plastic housing, as a rule, is local and does not spread over a large area.
Fiberglass has a relatively high resistance to water, oil, diesel fuel, atmospheric influences. Fiberglass is sometimes used to make fuel and water tanks, and the translucency of the material makes it possible to observe the level of the stored liquid.
Hulls of small vessels made of fiberglass are usually monolithic, which excludes the possibility of water penetration inside; they do not rot, do not corrode, they can be repainted every few years. For sports vessels, it is important to obtain an ideally smooth outer surface of the hull, which has 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; joints of fiberglass parts have a relatively low strength.
Fiberglass based on polyester resins are manufactured at a temperature of 18 - 25 0 C and do not require additional heating. The curing of polyester glass-reinforced plastics proceeds in two stages:
Stage 1 - 2 - 3 days (the material gains approximately 70% of its strength;
Stage 2 - 1 - 2 months (increase in strength up to 80 - 90%).
To achieve the maximum strength of the structure, it is necessary that the content of the binder in fiberglass be minimally sufficient to fill all the gaps of the reinforcing filler with the chain for obtaining 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 bundles, canvases (glass mats, chopped fiber and fiberglass.
The use of woven materials using twisted glass fibers as reinforcing fillers for the manufacture of hulls of boats and yachts from fiberglass is hardly justified both economically and technologically. On the contrary, nonwoven materials for the same purposes are very promising and the volume of their application is growing every year.
The cheapest filling is glass bundles. 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, bundles are used to obtain products where it is necessary to achieve preferential strength in one direction, for example, beams of a set. When building hulls, cut (10-15 mm) bundles are used to seal structural gaps that form when making various kinds of connections.
Chopped glass bundles are also used for the manufacture of hulls of small boats, yachts, obtained by spraying fibers mixed with polyester resin on the appropriate form.
Fiberglass - rolled materials with chaotic laying of glass fibers in the plane of the sheet - are also made from bundles. Scrim-based GRPs have lower strength characteristics than fabric-based GRPs due to the lower strength of the scrims themselves. But fiberglass, cheaper, have a significant thickness at low density, which ensures their good impregnation with a binder.
Layers of fiberglass can be bonded in the transverse direction chemically (using binders) or mechanical stitching. Such reinforcing fillers are laid on a surface with a large curvature easier than fabrics (the fabric forms folds, requires preliminary cutting and adjustment). Hopsts are used mainly in the manufacture of hulls of boats, motor boats, yachts. In combination with glass fabrics, scrims can be used for the manufacture of ship hulls, which are subject to higher strength requirements.
The most important structures are made on the basis of glass fabrics. Most often, satin weave fabrics are used, which provide a higher coefficient of utilization of the strength of the threads in fiberglass.
In addition, in small shipbuilding, fiberglass tow is widely used. It is made from untwisted threads - tows. This fabric has more weight, less density, but also less cost than fabrics made from twisted threads. Therefore, the use of towed fabrics is very economical, taking into account, moreover, the lower labor intensity in the formation of structures. In the manufacture of boats, boats, braided fabric is often used for the outer layers of fiberglass, while the inner layers are laid out from rigid fiberglass. This achieves a reduction in the cost of the structure while simultaneously providing the necessary strength.
The use of unidirectional corded fabrics, which have predominant strength in one direction, is very specific. During the formation of ship structures, such fabrics are laid in such a way that the direction of the greatest strength corresponds to the greatest acting stresses. This may be necessary in the manufacture of, for example, spars, when it is necessary to take into account a combination of strength (especially in one direction), lightness, taper, varying wall thickness and flexibility.
Since the main loads on the spars (in particular, on the mast) act mainly along the axes, it is the use of unidirectional bundled fabrics (when the fibers are located along the spars, it provides the required strength characteristics. In this case, it is also possible to manufacture the mast by winding the bundle on a core (wooden, metal etc.), which can subsequently be removed or remain inside the mast.
At present, the so-called three-layer structures with lightweight filler in the middle.
The 3-layer construction consists of two outer load-bearing layers made of thin, strong sheet material, between which is placed a lighter, although less durable aggregate. The purpose of the filler is to ensure the joint work and stability of the bearing layers, as well as to maintain the specified distance between them.
The joint work of the layers is ensured by their connection with the filler and the transfer of the latter forces from one layer to another; the stability of the layers is ensured, since the filler creates an almost continuous support for them; the necessary distance between the layers is maintained due to the sufficient rigidity of the filler.
Compared to traditional single-layer, three-layer construction has increased rigidity and strength, which allows 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), however, they are most widely used when using polymer composite materials that can be used both for carrier 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, they form a hull structure - they also perform a number of others, for example, they impart thermal and sound insulation properties, provide an emergency buoyancy reserve, etc.
Three-layer constructions, due to the absence or reduction of elements of the set, make it possible to more rationally use the internal volumes of the premises, to lay electrical lines and some pipelines in the aggregate itself, and to facilitate the maintenance of 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 provide a good bond between the carrier layers and the filler due to the lack of adhesives with the necessary properties, as well as insufficiently careful adherence to the gluing process. Due to the relatively small thickness of the layers, their damage and water filtration through them, which can spread throughout the 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 which the space between the outer and inner skins is filled with foam in order to ensure buoyancy, strictly speaking, they cannot always be called three-layer, since they do not represent flat or curved three-layer plates with a small thickness of the filler. It is more correct to call such constructions double-sheathed or double-hulled.
It is most expedient to perform three-layer elements of cuttings, bulkheads, etc., which usually have flat, simple shapes. 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 according to the type of filler can be classified in the following way: with a solid filler made of foam plastic, balsa wood; with honeycomb filler made of fiberglass, aluminum foil; box-shaped panels made of polymer composite materials; combined panels (box-shaped with foam). The bearing layers in their thickness can be symmetrical and asymmetrical with respect to the middle surface of the structure.
According to the manufacturing method three-layer structures can be glued, with a foaming filler, molded on special installations.
As the main components for the manufacture of three-layer structures, the following are used: fiberglass grades T - 11 - GVS - 9 and TZHS-O.56-0, glass meshes of various grades; polyester resins marui PN-609-11M, epoxy resins of the ED-20 brand (or other brands with similar properties), foam plastics of the PVC-1, PSB-S, PPU-3s brands; flame retardant laminate.
Three-layer structures are made monolithic or assembled from separate 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: the manufacture or preparation of the carrier layers, the manufacture or preparation of the filler, and the assembly and gluing of the panel.
The carrier layers can be prefabricated or directly during the molding of the panels.
The aggregate can also be applied either in the form of ready-made boards, or foamed by increasing the temperature or by mixing the appropriate components during the manufacturing process of the panels. Honeycomb core is manufactured at specialized enterprises and is supplied in the form of cut slabs of a certain thickness or in the form of honeycomb blocks that require cutting. Tiled foam is cut and processed on carpentry tape or circular saws, thicknessing and other woodworking machines.
The decisive influence on the strength and reliability of sandwich panels is exerted by the quality of gluing of load-bearing joints with filler, which, in turn, depends on the quality of preparation of the surfaces to be glued, the quality of the adhesive layer formed and adherence to gluing conditions. Surface preparation and application of adhesive layers are detailed in the relevant bonding literature.
For gluing carrier layers with honeycomb filler, adhesives of the BF-2 (hot-curing), K-153 and EPK-518-520 (cold-curing) grades are recommended, and with tile foam plastics, adhesives of the K-153 and EPK-518-520 grades. The latter provide a 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 (BF curing time is 2-1 hour).
When foaming foams between the carrier layers, the application of adhesive layers on them, as a rule, is not required. After gluing and the necessary exposure (7-10 days), the panels can be mechanically processed: cutting, drilling, cutting holes, etc.
When assembling structures from three-layer panels, it should be taken into account that at the joints, the panels are usually loaded with concentrated loads and the nodes must be reinforced with special inserts from a material denser than the filler. The main types of joints are mechanical, molded and combined.
When fastening parts, saturation on trex constructions, it is necessary to provide for internal reinforcements in the fastener, especially when using mechanical fasteners. One of the methods of such amplification, as well as the technological sequence of the assembly, are shown in the figure.
A relatively large effect is obtained by the use of fiberglass structures exposed to various aggressive substances that quickly destroy conventional materials. In 1960, about 7.5 million dollars were spent on the manufacture of corrosion-resistant fiberglass structures in the USA alone (the total cost of translucent glass-reinforced plastics produced in 1959 in the USA is approximately 40 million dollars). Interest in corrosion-resistant fiberglass structures is explained, according to firms, primarily by their good economic performance. Their weight is much less than steel or wooden structures, they are much more durable than the latter, they are easy to erect, repair and clean, they can be made on the basis of self-extinguishing resins, and translucent containers do not need water gauge glasses. Thus, a serial container for aggressive environments with a height of 6 m and a diameter of 3 m weighs about 680 kg, while a similar steel container weighs about 4.5 tons. is part of the weight of the steel pipe with the same bearing capacity; although a fiberglass pipe cost 1.5 times more to manufacture, it is more economical than steel, because, according to foreign companies, the service life of such structures made of steel is calculated in weeks, of stainless steel - months, similar structures made of fiberglass are operated without damage for years. Thus, a pipe 60 meters high and 1.5 meters in diameter has been in operation for the seventh year. The previously installed stainless steel pipe lasted only 8 months, and its manufacture and installation cost only half as much. Thus, the cost of the fiberglass pipe paid off after 16 months.
An example of durability in an aggressive environment are also fiberglass containers. Similar containers can be found even in primordially Russian baths, since they are not affected by high temperatures, more information about various high-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, having served 6 times longer than the corresponding metal one; only one repair cost for the last one over a five-year period is equal to the cost of a fiberglass tank. In England, the Federal Republic of Germany and the USA, containers in the form of warehouses and water tanks of considerable height have also found wide distribution. Along with the indicated large-sized products, in a number of countries (USA, England), pipes, air duct sections and other similar elements intended for operation in aggressive environments are serially manufactured from fiberglass.
Construction is an area for which the chemical industry works tirelessly, creating new alloys and materials for the production of various products. One of the most important and promising achievements in this area in recent years can be called the results associated with work on such a composite material as fiberglass. Many engineers and builders call it the material of the future, as it managed to surpass many metals and alloys in its qualities, including alloy steel.
What is fiberglass? This is a composite that has two components: a reinforcing and a binding base. The role of the first is fiberglass, the second is resins of various chemical composition. Variations with the amount of both make it possible to make fiberglass resistant to the conditions of almost any environment. But it should be understood that there is no universal type of fiberglass, each of them is recommended for use in certain operating conditions.
Fiberglass is of interest to designers because the finished product from it appears simultaneously with the material itself. This feature gives a lot of room for imagination, allowing you to manufacture a product with individual physical and mechanical characteristics according to the specified parameters of the client.
One of the most common fiberglass building materials is grating. Unlike steel flooring, it is produced by casting, which gives it such characteristics as low thermal conductivity, isotropy, and of course, like steel materials, strength and durability.
Stair steps are made of fiberglass grating, however, the whole structure is also made of fiberglass parts: racks, handrails, supports, channels.
Of course, such stairs are very durable, they are not afraid of corrosion and exposure to chemicals. They are easy to transport and install. Unlike metal structures, several people are enough to install them. An additional plus is the ability to choose colors, which increases the visual appeal of the object.
Gangways made of fiberglass have become very popular. Their reliability is due to the same unique characteristics of the composite we are describing. Pedestrian areas equipped with fiberglass gangways do not require special maintenance, their operational capabilities are much higher than those of the same type of metal structures. It is proved that the service life of fiberglass is much longer than the latter and is more than 20 years.
Another high performance offering is the GRP handrail system. All railing parts are very compact and easy to assemble by hand. In addition, there are many variations of the finished structure for the client, as well as the opportunity to carry out his own project.
Due to the dielectric properties of fiberglass, cable channels are produced from it. The isotropy of this material increases the demand for products intended for use in facilities sensitive to electromagnetic vibrations.
In general, it can be noted that the range of fiberglass products is quite wide. Working with him, builders and designers can realize the most fantastic ideas. All designs offered by our company are reliable and durable. The quality of fiberglass forms a relatively high price for it, but at the same time it is the optimal ratio of the advantages of this material and the demand for it. And besides, it is important to understand that the cost of its purchase will pay off in the future due to the reduction in the cost of its transportation, installation and subsequent maintenance.
When choosing structural materials for building and infrastructure construction, engineers often choose different types of fiberglass (FRP) that offer the best combination of strength properties and durability.The widespread industrial use of fiberglass began in the thirties of the last century, but until now its use is often limited by a lack of knowledge about which types of this material are applicable in certain conditions. There are many types of fiberglass, their properties, and therefore the scope of application can vary greatly. In general, the advantages of using this type of material are as follows:
Low specific gravity (80% less than steel)
Corrosion resistance
Low electrical and thermal conductivity
Permeability to magnetic fields
High strength
Ease of maintenanceIn this regard, fiberglass is a good alternative to traditional structural materials - steel, aluminum, wood, concrete, etc. Its use is especially effective in conditions of strong corrosive action, since products made from it last much longer and practically do not require maintenance.
In addition, the use of fiberglass is justified from an economic point of view, and not only because products made from it last much longer, but also because of its low specific gravity. Due to the low specific weight, savings on transportation costs are achieved, as well as simpler and cheaper installation. An example is the use of fiberglass walkways in a wastewater treatment plant, which were installed 50% faster than previously used steel structures.[I] GRP walkway installed on the quay
Although it is impossible to list all the applications of fiberglass in the construction industry, most of them can be summarized in three groups (types): structural elements of structures, gratings and wall panels.
[U] Structural elements
There are hundreds of different types of structural elements made of fiberglass: platforms, walkways, stairs, handrails, protective covers, etc.
[I]GRP ladder[U] Lattice
For the manufacture of fiberglass gratings, both casting and pultrusion can be used. The gratings produced in this way are used as decks, platforms, etc.
[I] GRP grate[U] Wall panels
Fiberglass wall panels are primarily used in less critical areas such as commercial kitchens and bathrooms, but they are also used in specialty areas such as bulletproof screens.The most common fiberglass products are used in the following areas:
Construction and architecture
Tool production
Food and Beverage Industry
Oil and gas industry
Water treatment and water treatment
Electronics and electrical engineering
Construction of swimming pools and water parks
Water transport
Chemical industry
Restaurant and hotel business
power plants
Pulp - paper industry
The medicineWhen choosing a specific type of fiberglass for use in a particular area, it is necessary to answer the following questions:
Will aggressive chemicals be present in the working environment?
What should be the bearing capacity?
In addition, it is necessary to take into account factors such as fire safety, since not all types of fiberglass contain fire retardants.Based on this information, the fiberglass manufacturer, based on the characteristics tables, selects the optimal material. However, it is necessary to make sure that the characteristics tables refer to the materials of this particular manufacturer, since the characteristics of the materials produced by different manufacturers can differ in many ways.