Application of basalt rock-based materials in the automotive industry

At the present stage of the automotive industry’s development, there is a strong demand for durable, lightweight and non-corroding structural materials and composites, protective coatings, and heat and sound insulation materials. Currently, low-cost glass fibres are the most commonly used in this sector. Carbon fibres are used in a limited number of applications, only where it is economically feasible.

Due to their specific technical characteristics and cost performance, materials made from basalt fibres (BF) have good prospects and can be widely used in the automotive industry. Considerable experience has already been gained in the use of materials and parts made from basalt continuous fibre (BCF) in the automotive industry and other sectors such as aviation, shipbuilding and railway carriage engineering. BCF and BCF-based materials have a number of high technical and operational characteristics.

First, they have a high durability due to the relatively high specific breaking strength of the fibres, significantly exceeding the values for metal (2-2.5 times) and E-glass fibre (1.4-1.5 times). Table 1 presents specific tensile strength data for basalt continuous fibres. These materials also offer a high resistance to external environmental factors and aggressive environments. Basalt fibres are suitable for structures operated in contact with moisture, salt solutions, chemical media, and are not subject to corrosion. Due to their high thermal resistance, basalt fibres can be used to produce non-combustible, high-temperature materials.

The range of temperatures for long-term use of BF is -200°С ~+600°С, and thermal insulation products made from andesite-basalt fibres can be used at temperatures up to 800°С. Basalt materials have good thermal and sound-insulating characteristics and have been widely used in aviation and shipbuilding for a long time. Thermal conductivity data for super-thin basalt fibre materials with a filament diameter of 1 to 3 microns is presented in Table 2.

Table 3 presents the soundproofing characteristics of materials based on super-thin basalt fibre with an elementary fibre diameter of 1 to 3 microns. The hygroscopicity of basalt fibres is 6-8 times lower than that of glass fibre.

Therefore, only basalt-based thermal and sound insulation materials are traditionally used in aircraft and shipbuilding, where a low hygroscopicity is very important. Basalt fibre-based materials also offer a high resistance and durability to vibrations and alternating loads.

BCF shows a high compatibility with other materials (metals, plastics, and adhesives) during the production process. This opens up huge perspectives for the production of a whole range of new composites such as metal-composite materials, honeycomb structures, fibre-reinforced plastics, protective coatings, etc. The high operational qualities of basalt fibre materials and products include high strength and low weight, impact resistance, stability to environmental and aggressive environments, aesthetic appearance and good maintainability and durability.

They are compatible with various processing technologies such as moulding, cold stamping, spraying, drawing and other technologies that do not involve significant energy costs, the so-called “cold technologies”. Positive experience has been accumulated in the application of BCF materials in the automotive industry and a number of related sectors such as aviation, shipbuilding, and car building.

The comparative characteristics of different continuous fibres (glass, carbon, aramid and basalt) used in the production of composite materials are presented in Table 4. The issues related to the use of basalt-based composite, reinforcing, thermal and sound insulating materials, materials for special applications, and protective anticorrosion coatings in the automotive industry are presented below.

BCF-based composite materials and parts
Composite materials are reinforced with 70-80% fibres. Their strength characteristics are mainly determined by the reinforcing fibres, in the form of rovings, chopped strand mats or fabrics. Composites are used for many different car parts such as external parts (bumpers, underbody, hood, fairings, and spoilers), electric drive car bodies, interior decoration elements (such as decorative panels) and body protection elements.

BCF chopped strand mats and basalt fabrics impregnated with binders are used to mass produce complex-shape composite parts such as bumpers and car bodies by vacuum moulding.
For a long time, a number of cars with glass fibre-based composite bodies were mass-produced. But these cars were produced in limited series. BCF offers several advantages over glass fibre, including low hygroscopicity and higher chemical resistance, tensile strength and impact strength.

This is important in the manufacture of car parts with specific safety requirements in the event of collisions and accidents. BCF composites withstand many years of operation in contact with natural factors such as moisture, salt solutions, alkalis and acids.
Composite car bodies made of BCF materials are particularly suitable for electric vehicles as they are more durable, not susceptible to corrosion, electrically insulating, durable in use, and 2.5-3 times lighter than metal. Lightweight composite car bodies make it possible to install additional batteries and to increase the range of electric vehicles. Leading companies such as Volkswagen and BMW have developed BCF-based composite car bodies.

High-pressure cylinders for compressed natural gas
The conversion of car engines from gasoline to compressed natural gas requires the production of high-pressure cylinders for pressures up to 250 bar (kg/cm2).
The test pressure for cylinders is 500 bar. Due to its high breaking strength and resistance to alternating loads, BCF is most suitable for the production of…

This article has been published in the JEC Composites Magazine N°148.

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