For a long period in its development, human society used a limited range of materials for its needs: wood, stone, fibers of plant and animal origin, burnt clay, glass, bronze, iron. Industrial revolution of the 18th century especially the creation of steam engines and the appearance at the end of the 19th century. internal combustion engines, electric machines and automobiles, complicated and differentiated the requirements for the materials of their parts, which began to work under complex alternating loads, elevated temperatures, etc.
The basis of structural materials is metal alloys based on iron, copper, tin, and lead. Further development of technology, when the main requirement for structural materials was high specific strength, presented new requirements. Low-alloy steels, aluminum, titanium and magnesium alloys, and heat-resistant alloys based on nickel and cobalt are widely used.
To achieve these goals, light metals (Al, Mg, Be) and their alloys, metal and non-metal composites, metal foams, ceramics, and intermetallics should be widely used.
New composite materials based on carbon fibers are widely used in the automotive industry.
Carbon fiber materials have a number of unique characteristics and properties and have the best value for money. The most important advantage of carbon fiber is its extremely light weight and high strength. CFRP is 5 times lighter than steel and 1.8 times lighter than aluminum.
Nowadays, carbon fiber materials are used to create almost any car assembly. Composite materials and products based on continuous fibers and reinforcing fabrics are widely used for the production of external car parts. Most often, bumpers, fairings, spoilers are made of them; interior trim elements of the car: torpedo, interior decorative panels; elements of protection of the car body, the bottom of the car.
Along with CFRP, a composite material such as fiberglass is used in the automotive industry. It is widely used in the production of external body panels (front and rear) of buses, trolley buses, interior elements, aerodynamic contours, wheel arch liners, car bumpers, roof racks, dashboards. The popularity of the use of fiberglass is due to its higher physical and mechanical properties in comparison with other types of thermoplastics and plastics. This is both higher strength and scratch resistance; constancy of the structure of the material at low and high temperatures; relatively low weight of fiberglass products; resistance to vibration loads and shocks.
The advantages of ceramic composites are primarily determined by the properties of the matrix. Ceramic matrices provide the highest operating temperatures for composite materials. Ceramics is chemically and thermally resistant material, has a high level of compressive strength properties.
The disadvantage of the absolute majority of ceramic materials is a very low level of crack resistance. Attempts to bring ceramics closer to metallic materials have led to the development of cermets, i.That is, materials with a combined matrix obtained from powders (more than 50% is ceramics, and the rest is metal). It is more efficient to introduce metal into the ceramic matrix in the form of fibers rather than powder. Most often, tungsten, molybdenum, niobium, and steel fibers are used to harden ceramics. Metal fibers are more ductile than ceramics. They perceive a significant part of the load, restrain the development of cracks in the composite, and perform the function of structural elements that increase the fracture toughness and heat resistance of materials.
The main factor limiting the use of metal fibers in ceramic composites is their increased tendency to oxidation at high operating temperatures.
Therefore, ceramic fibers are often used as reinforcing elements in ceramic composites. The advantages of this type of fibers are as follows: a small difference in the elastic moduli and thermal expansion coefficients of the materials of the fibers and matrix; chemical affinity of composites components; heat resistance of ceramic fibers. Effective reinforcing elements of the ceramic type in composite materials are silicon carbide fibers, carbon fibers. Borosilicate, aluminosilicate, lithium silicate glasses can serve as matrices in carbon-ceramic materials.
Intermetallic compounds are a new class of materials (chemical compounds of metals), which in their structure occupy an intermediate position between metals and ceramics. They have a complex crystal structure with up to 30% covalent bonds in interatomic bonds, which determines their physical and mechanical properties: high heat resistance, low density and flammability in oxygen, high wear resistance. Intermetallic alloys are called next generation materials because of their inherent shape memory effect. This effect is manifested in the fact that after giving the sample a certain shape at an elevated temperature, it is given a new shape by plastic deformation at a lower temperature, and after heating, the original shape of the sample (part) is restored.
To date, more than 100 shape memory alloys are known. However, of this total number, only the NiTi intermetallic compound and alloys with alloying elements based on it have found the greatest practical application.
The NiTi intermetallic compound deforms well in hot and cold conditions. All kinds of semi-finished products can be obtained from it: sheets, tape and foil of various thicknesses, rods, wire of various sections, pipes. These semi-finished products can be obtained with different temperatures of shape recovery: from -100; -180 C to +60, +120 C. In addition, titanium nickelide has a high damping capacity, good wear and corrosion resistance.
The main application of NiTi intermetallic compounds and alloys based on it is associated with instrumentation and mechanical engineering, medicine, and intermetallic alloys based on Ti compounds
New materials in the modern automotive industry
The fundamental task of modern car manufacturers is to reduce the weight of the car. Duralumin bodies have already reached the level of mass production, although so far only on expensive models (Audi, Jaguar). Many parts of the chassis are made of aluminum instead of steel, as well as lighter components. But the struggle with the weight of the car continues and even reaches a new level in connection with the tightening of requirements for efficiency and environmental friendliness.
Aluminum in this struggle, naturally, takes the leading place. Specifically “for now”, because there are also more attractive materials with the highest mechanical properties, but even more lightweight.The leading automotive companies and component manufacturers are engaged in their development in mass production.
The problem of lowering weight is further complicated by the fact that cars, due to impartial circumstances, are becoming more complex and, accordingly, more languid. New lightweight construction materials are designed to make up for weight, including new components, and active and passive safety systems, a decrease in the level of toxicity, and a constant increase in the level of comfort.
The 1988 Volkswagen Golf 1.6 Diesel weighed 920 kg. Golf currently in production – 1320 kg. But this is not unusual. Over the past 20-plus years, cars have generally become significantly heavier, despite the increasingly extensive use of aluminum, light alloys and plastics. All new and new systems mentioned above find application in the following models (in comparison with the past). For example, the same Golf of 1988 did not have a number of fundamental units and components in the serial production, such as power steering, air conditioner, airbags, a filter for capturing hard particles during combustion. This naturally means increasing the weight of the car.