BMD made of fiberglass and ceramics - this was also proposed in the USSR
As is known, combined armor, which involves the use of various metallic and non-metallic elements in protective structures, was actively used in the creation of a number of Soviet main tanks, starting from the T-64 and ending with the T-80. Which, in general, cannot be said about serial vehicles of a much lighter class - BMD and BMP, whose armor, largely for technological reasons, has always been limited to steel and aluminum (separately or in combination).
However, one should not think that the development of combined armor for light armored vehicles in the USSR was not carried out at all - there were projects and proposals on this topic, and some of them looked quite interesting. An example is fiberglass and ceramic armor for the BMD, a detailed description of which was published in 1990. We suggest reading it, since there is no point in retelling the words of the authors if there is an opportunity to read the original.
Use of composite materials for lightweight VGM
In recent years, in our country and abroad, experimental design work on the use of composite materials for armored vehicles has been "completed". Of the foreign works, the most well-known are attempts to create hulls from composite materials for American armored personnel carriers and infantry fighting vehicles. Their goal was to reduce the weight of the vehicles while maintaining a given level of armor protection.
In the USSR, the possibility of creating a hull from composite materials for an airborne combat vehicle (BMD), the hull of which is made of armor materials based on aluminum alloys, was studied. For this vehicle, a hull design based on fiberglass and ceramics was proposed. It was found that for a BMD hull with protective modules made of 15 mm thick fiberglass and 8 mm thick ceramics, while maintaining the weight of the aluminum hull, it is possible to provide full protection from a 7,62 mm armor-piercing bullet from all distances. At the same time, the gain in weight is 32 kg from each square meter of the hull surface. On a model of such a hull, a 25% gain in weight was achieved while simultaneously reducing the damage to the side projections of an armor-piercing 7,62 mm bullet from a distance of 500 m to 0. It turned out that the energy costs for the production of an aluminum hull are 1,5 times less, and a composite hull is half as much as for the production of a steel hull.
The results of full-scale tests of various designs of barriers based on fiberglass with ceramics (Fig. 1) showed that their use for protection against armor-piercing bullets can provide a weight gain of up to 50% compared to equally resistant steel armor. Using these results and the experience of manufacturing a model of a composite hull made it possible to move on to the development of a design, technological processes and the manufacture of experimental samples of the BMD hull. When designing the hull, it was necessary to ensure complete identity of its internal volumes to the aluminum hull sample, to preserve the external contours for the installation of serial external equipment, hydropneumatic suspension, etc. A contact molding method was developed for the fiberglass hull of the vehicle. The technological process for manufacturing the experimental BMD hull is based on the technology used in shipbuilding.
For fiberglass structural elements, fiberglass fabric grade T-11-GVS-9 according to GOST 19170-73 was used, and resin grade PN-609-21M according to OST 6-05-431-78 was used as a binder. Fiberglass elements and structures were molded based on 22 fiberglass layers per 10 mm of thickness. When molding flanges and a set, the design requirements for their thickness were met without taking into account the number of fiberglass layers, but not less than 22 layers per 10 mm. The outer shell can be molded using a single (disassemblable) model. In this case, the manufactured hull is obtained as a single non-disassemblable part. A serious disadvantage of this method is the impossibility of manufacturing a high-quality outer surface, as well as the difficulties in installing the filler when forming the hull. To improve the quality of hull manufacturing, its individual parts (bottom with sides, roof) were formed in matrices with subsequent welding of the parts.
Fig. 1. Bullet resistance when fired at by a B-32 bullet of 7,62 mm caliber (dependence of the limit of conditional damage on the surface density p of protection) of composite armor barriers with a supporting layer made of MPS fiberglass and a face layer made of: 1 - atenite 8 mm thick; 2 - silicon carbide 9 mm; 3 - corundum 7 mm; 4 - ceramics type GMT 8 mm. Note: Vпкп along the X axis is the bullet velocity upon impact with the armor, at which no through holes, breaches, etc. are observed.
The matrix (Fig. 2) is a one-piece rigid base welded from rolled section with removable parts along the sides and in the bow of the hull, with devices for removing the product after molding, for obtaining local contours in areas of sharp changes in the shape of the hull skin, for installing embedded parts, etc.
Fig. 2. General view of the matrix (a) and the ceramic blocks installed in it (b): 1 – upper and lower side blocks
The connection of the fiberglass and metal structures is made with K-153 or EPK glue according to OST 5.9767-79 without filler. To mold the screw connections in areas where there are no special coatings, a paste made of chopped fiberglass, K-153 or EPK epoxy binder is used. Individual parts of the body, manufactured by molding in a matrix, are welded together. With the matrix manufacturing method, the ceramic filler can be placed at the required depth of the fiberglass layer, the outer surfaces of the machine body are of high quality. Depending on the weight of the machine, the type of equipment installed on it, weapons, the speed of movement and the dynamic characteristics of the suspension, various body designs can be used, each of which must ensure strength and rigidity.
The experience gained to date in using various composite materials has made it possible to propose three basic design options for hulls for light-weight VGMs.
A one-piece plastic hull, which is a frameless load-bearing system in which the turret support, engine subframe, bulkheads, suspension mounting devices, etc. are installed using adhesive and threaded connections. Such a hull can be used for light unarmored vehicles, as well as for lightly armored vehicles with suspension (for example, hydropneumatic), which transmits small loads to the hull.
A combined body (Fig. 3, a) made of plastic, but with a metal bottom. Its plastic part and the bottom are connected by a transition device using adhesive and threaded connections or welding. It can be used for VGM or wheeled vehicles weighing more than 10 tons.
A plastic body reinforced with a metal frame (Fig. 3, b). It can be used for light armored vehicles. In addition to the contact molding method, other methods of manufacturing plastic bodies can be used depending on the production program, requirements for the quality of the material and design, and the possibilities of ensuring the technological process.
All three design schemes of the hull considered here can be produced by the contact molding method. However, it does not ensure the stability of the mechanical properties of the material, is very labor-intensive and therefore can be used only for limited production programs and in experimental design work.
Fig. 3. Schemes of combined (a) and plastic hulls reinforced with a metal frame: 1 – upper part of the hull (made by winding); 2, 3 – bow and stern parts of the hull (made by contact molding or pressing); 4 – lower (metal) part of the hull; 5 – connecting unit; 6 – metal frame
A well-known method of manufacturing body parts is pressing, which makes it possible to obtain 2nd and 3rd body variants, but requires unique pressing equipment.
The winding method also requires special equipment and complex tooling, and does not ensure the production of all parts of the hull. In this case, the front and rear parts of the hull must be produced either by pressing or contact molding. The winding method can be used to produce the 1st and 2nd variants of the design schemes (see Fig. 3, a, b). It is used to produce only the middle (tubular) part of the hull, which is cut along the diametrical plane into two identical parts; each of them becomes the upper half of the hull. The remaining parts 2, 3 (see Fig. 3, b) are made by contact molding or pressing.
The schemes of fiberglass and combined hulls manufactured for the running model of the VGM have been developed (Fig. 4). The upper part of the latter is made of fiberglass by the method of contact molding in a matrix with an external ceramic layer. The connection of the upper 1 and lower (metal) 2 parts of the hull is carried out using a special transition device 3.
In order to ensure the specified strength and rigidity, the one-piece plastic hull of the BMD with the minimum possible weight is made entirely of fiberglass in the form of a frameless load-bearing system. The shell material is cold-curing fiberglass based on T11-PVS-9 fiberglass and PN-609-21M polyester resin. PKhZ-1 foam plastic is used as a filler in the cross beams. The hull shell is 15 mm thick, the front and front side parts are 30 mm thick, which meets the requirements for bulletproof resistance. The upper part of the hull was molded in a matrix on two wooden punches (upper and lower) using standard technology. The turret support, engine underframe, bulkheads and other integral elements are installed in the hull using adhesive joints.
The use of composite materials in the manufacture of hulls and turrets of light vehicles allows for an additional reduction in the vehicle's visibility and the likelihood of being hit. rockets with homing heads and mines armed by a magnetic field, as well as a behind-the-armor dose of penetrating radiation. At the same time, it is possible to increase the accuracy of fire by reducing the level of noise and vibration.
The operational advantages of using composite materials include:
1. No need for frequent cleaning and painting of body elements, as well as a reduction (or complete elimination) of work related to eliminating the consequences of corrosion;
2. Reduced likelihood of cracks from impacts;
3. Simplification of repairs during operation; improvement of ergonomic indicators (lower noise level, vibration, easier thermal conditions).
Fig. 4. General view of the combined hull for the running model of the VGM
Due to the listed advantages, making the hull and turret from fiberglass is more cost-effective than from metal.
Technological advantages of using composite materials include:
Significant reduction in energy costs;
The ability to manufacture housing structures of virtually any shape with higher surface quality and lower labor intensity than structures made from traditional materials;
Reduced labor intensity (if, for example, the production of a metal case requires special equipment, electric and gas welding equipment, stamps, presses, highly skilled workers and specialists, then the production of a plastic case requires only a warm room, tooling and relatively low-skilled molders);
Use of cheaper materials (mass-produced ceramic plates based on corundum cost 9 thousand rubles per 1 ton; 0,4 tons of such plates are used for one body).
The disadvantages of composite materials include a low modulus of elasticity, as well as low strength of the connection of structural elements to each other.
The use of composite materials for the manufacture of main battle tank hulls and turrets is very problematic. At this stage of tank development, protection from armor-piercing subcaliber projectiles is mainly provided by the steel component of the combined armor. However, it is possible to widely use composite materials in the construction of main battle tank hulls and turrets as a "package" for ceramic filler installed in barriers, for the manufacture of add-on protective modules with ceramics. They can also be used in the construction of the engine-transmission compartment roof, hull hatches, compartment walls, and rear hull and turret parts.
If some elements of the tank's internal equipment are moved to the fenders (for example, batteries, a filter and ventilation unit, an autonomous power unit), the latter can be reliably protected from shell fragments and bullets by screens made of composite materials.
Output. The use of composite materials for light armored vehicles will reduce their weight while maintaining a given level of armor protection or increase the level of protection while maintaining weight and will provide some reduction in the probability of damage, as well as improvement of the operational and production-technological performance of the vehicles.
Source:
"Use of Composite Materials for Light Armored Vehicles". A. V. Kozlov, O. M. Lazebnik, A. F. Misyuk, B. I. Bobrov. Bulletin of Armored Vehicles No. 4 for 1990.
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