The textile products are used in automotive, ship, and aircraft. Many coated and reinforced textiles are used in materials for engines such as air ducts, timing belts, air filters, non-wovens for engine sound isolation. A number of materials are also used in the interior of cars. The most obvious are seat covers, safety belts, and airbags but one can find textiles also for the sealing.
Nylon gives strength and its bursting strength is high is used as airbags in cars. Carbon composites are mostly used in the manufacture of airplane parts while carbon fibre is used for making higher-end tires. High tensile polyester is used for making air balloons.
Concealed components are those which help in increasing the efficiency of other operations and give safety to the driver during accidents. Mainly these are not visible in an automobile. They include:
1 Tyre Cords
The tire, a rubber/textile composite (approximately 10% w/w of textile) dates from 1888 when the canvas was the reinforcement used in Dunlop’s first tire. Continuous filament rayon began to be used in the 1930s.
The cords are formed by twisting yarns together to build up a strong cord in two or three separate operations. Twist direction is usually in the same direction for the first two operations and in the reverse direction for the final process.
The car radial tire contains about 4 to 7% of its total weight of textile material; cross-ply tires contain much more, about 21%.70 Radial tires have a steel cord ‘breaker’ layer between the rubber and the textile ply for added resistance to shock.
The materials for tire cord was been changed as the time passed from cotton, rayon nylon, polyester. Thermal instability limitations of polyester can also give rise to problems in tire manufacture, but despite this, polyester is the least expensive material for tire cord, and so it is the most extensively used fibre throughout the world for car tires.
Aramids offer the highest strength-to-weight ratios coupled with high-temperature resistance and are well suited to specialty cars and aircraft. Low shrinkage properties are important because yarn movement when the tire is subject to heat during the vulcanization process or during use could lead to distortions and reduced performance and durability. Due to performance limitations because of difference in the elastic properties of rubber and fibre, it gives poor fibre-rubber bonding.
Kevlar short fibre/rubber dispersions which allow the specialty properties of Kevlar, i.e. high tensile strength, high modulus and thermal and flexural performance are transferred to the rubber. The result is a tire with better resistance to tears and cuts, punctures and actually wear. So far the new technology has been successfully applied to bicycle and motorcycle tires and is under test for cars and other vehicles.
One estimate states that a 35% reduction in rolling resistance of all tires would save 5% of fuel consumed.
A variety of different fabric manufacturing techniques are used; knitting, circular weaving, wrapping, and for high-pressure uses, filament spiraling and braiding. Cotton was first used but he has been replaced with synthetic fibres, which provide higher strength, more durable flex and abrasion resistance and better rot resistance.
For the highest performance of heat and strength, aramid fibres such as Nomex and Kevlar (both DuPont) are used. Automotive hose products include fuel, oil, radiator heaters, hydraulic brakes, power steering, automatic transmission and air conditioning pipes.
Nylon is not generally used in hoses because of its high extensibility but this specific property is useful in the expanding part of power steering hoses.
Cotton was first used but was replaced as soon as synthetic fibre–rubber bonding difficulties were overcome, and now synthetic-fibre specialist high tenacity yarns are used in cord form. High tensile strength, excellent flex resistance, excellent shock resistance and low extensibility are amongst the requirements for a long belt life.
The V-belt is shaped for maximum friction grip as well as high strength with compactness and is composed of cord made from HT yarn such as the Trevira 700 series and rubber, usually chloroprene, covered with a fabric/rubber jacket.
Textile-toothed belts have almost completely replaced chain drives in cars because they are quieter, weigh less, need no lubrication and allow a more compact design. Textile belts are more flexible and smaller pulleys can be used compared to chain drives.
A triggering device sets off explosive chemicals when it senses an accident above 35 km/h is about to occur. These chemicals inflate the bag to restrain and cushion the car occupant from the impact with harder objects. The fabric from which the bag is made must be capable of withstanding the force of the propellant chemicals.
More important, the hot gases must not penetrate the fabric and burn the skin of the car occupant. The earliest airbags were Neoprene (DuPont)-coated, woven nylon 6.6, but lighter and thinner silicone-coated versions soon followed. Later, however, uncoated fabrics have appeared.
There are advantages and disadvantages for each type; coated fabrics are easier to cut and sew with edges less likely to fray and air porosity can be better controlled, whilst uncoated bags are lighter, softer, less bulky and easier to recycle.
Airbags are typically made from high tenacity multifilament nylon 6.6 in yarn quality fineness’s from 210, 420 to 840 denier although some polyester and even some nylon 6 is used. Nylon 6 is said to minimise skin abrasion because it is softer. It needs to have high tear strength, high
Anti-seam slippage, controlled air permeability (about 10 lm-2min-1) and be capable of being folded up into a confined space for over 10 years without deterioration.
Some tests require 75% property retention after 4000 hours at 90–120°C, the equivalent of 10 years UV exposure and also cold crack resistance down to -40°C. New fibre nylon 4.6 with a melting point of 285 °C has been introduced especially for airbags.
In the USA, FMVSS 208 requires all passenger cars sold during 1997 to have airbags both for the driver and front seat passenger. Worldwide production of airbags was about 43 million units in 1997 and this was expected to grow to 120–200 million units (up to 50000 kg of mainly woven nylon) by the year 2000. Future airbags are likely to be smaller, lighter and more compactable.
5 Air And Fuel Filters
There are about a dozen different kinds of filter used in cars but only about half use textile materials. Paper is used in many applications such as the oil filter and carburetor air filter, although non-wovens are used in some Japanese cars for the latter application.
Recent research has shown that the air quality inside a car can be several times poorer than the air quality outside, especially if the car is driven closely behind another vehicle. This is referred to as the ‘tunnel effect’, the consequence being the same as a car driven through a tunnel. The concentration of exhaust gases inside can be as high as six times or more the level of that on the outside.
In addition to exhaust gases, car occupants are also exposed to windscreen-washer-fluid odor, agricultural odors of fertilizers and manure, industrial fumes, pollen, spores and even viruses and bacteria. Dust particles and pollen can cause allergic reactions and diesel fumes and aromatic hydrocarbons can be even more damaging to health.
Particle size covers the range from 0.001 microns up to 100 microns. Particles in the region of between 2 and 5 microns originate mainly from combustion and industrial processes, i.e. man-made and comprise heavy metals, carbon, and sulfur. Larger particles than this are generally naturally occurring substances including, sand, soil, pollen spores, and bacteria. Large particles are deposited in the nose and upper respiratory passages and the particles that are smaller than 10 microns – the PM10s are mainly deposited in the lower respiratory tracts.
There are three basic ways in which the filters work. The first is by mechanically filtering out solid particles through fine pores in the nonwoven fabric. The second is by imparting an electrostatic charge to the fibre, which then attracts solid particles electrostatically. The third mechanism is by the use of activated carbon which adsorbs gases and is therefore also capable of removing odors.
Activated carbon consists of very small and finely divided particles each with an internal pore structure which presents a very large surface area available for the adsorption of gases. To maximize the effect, activated carbon granules are arranged in the filter to present the maximum surface area and 200 g of the material, in theory, offers a total surface area of 200000m2 available for gas adsorption.
The latest advanced filters combine both mechanical filtering through polypropylene non-woven electret fabric with adsorption by activated carbon. Filter fabric is arranged in a pleated form to provide a maximum surface area with minimum airflow resistance. The adsorption and retention capacity of the filter for odors in a given airflow rate is a measure of the filter’s performance.
The non-woven filter fabric itself must be strong when wet, be odor-free, resistant to micro-organisms and resistant to extremes of temperature. Further improvements in performance, life-span and fan air pressure drop can be expected as more competitors enter this area.
6 Noise And Vibration Dampening
The generation of vehicle interior noise comes from many sources. These sources can be categorized into three types: vehicle noise sources such as engine noise, exhaust noise, and brake noise; road and wind (aerodynamic) noise sources; miscellaneous noise sources such as noises of squeak, rattle, and tizz from interior components and ancillaries.
The sound is propagated through the air and by vibration of the car body and there are three basic mechanisms for reducing it: by absorption, by damping and thirdly by isolation or insulation. In general, a thick piece of material will absorb more sound than a thinner piece of the same material.
There are a number of layers of material and permutations of layers of materials used in noise and vibration damping, see Table 7.2. Density, air porosity, and thickness of the material influence sound absorbency, but actual frequency of the sound waves is also relevant.
When the noise wave reaches the surface of an auto interior part during its propagation by an airborne path, it will become three different components: reflected part, transmitted part and absorbed part. Absorbing the incident noise wave by an acoustic material is an effective way to lower the reflected noise level in the interior noise control engineering.
The material has been used must function like air, being able to prevent noise reflection from incidence surface, and like an energy dispenser capable of dissipating the noise energy entering the material. The principle of noise absorption by these textile materials is generally described by the following mechanisms:
- Heat conduction converted from the sound energy encapsulated in porous areas in the material.
- Viscous losses because of oscillating air flow entering the porous areas of the material.
- Material vibration mainly caused by the noise waves encapsulated in closed porous areas.
A wide range of textile materials, natural fibre, and synthetic fibre nonwovens (felts) with sufficient fabric weight and thickness are suitable for the noise insulation application in automobiles. They are usually incorporated together with décor fabrics, interlinings and substrates into interior parts as a composite backbone after a hot-pressing process.
7 Body Panel Reinforcement In Composites
Composites straddle the textile and plastic industries and can be regarded as a macroscopic combination of two or more materials to produce special properties, which are not present in the separate components. In general terms, the chemical properties are determined by the plastic component, and the physical properties determined by the fibre.
Glass-reinforced plastics (GRP) date from the 1920s and combine high strength with light-weight properties. During the 1960s more advanced fibres became available, carbon and aramid fibres and others which are all many times stiffer than glass but, with the exception of aramids, are brittle and must be used in combination with other materials.
Carbon fibres were first produced at the Royal Aircraft Research Establishment during 1963 in England. There are a number of different varieties and their properties vary significantly depending on the conditions of manufacture. There are very many potential combinations of fibre and plastics, but in actual fact, most composites are based on just three fibres: glass, carbon, and aramid, or a combination of them, in a polyester, epoxy or phenolic resin.
The density of these three resins, which are all thermosetting at about 1.2g/m3, is considerably less than even aluminum. Chemical properties are determined mainly by the fibre component, the chemical and thermal properties mainly by the polymer.
At the present time, the most significant advantage of composites is the replacement of heavier metal with lighter components, which results in fuel savings throughout the life of the vehicle. Actual material cost of composites exceeds that of metal but there are several other significant benefits from their use. These include less bulk, and therefore more useful space, anti-corrosion, dent resistance, and high rigidity and strength.
Composites also allow more design freedom, which means that complex shapes not easily produced in metal, can be more easily achieved. This is especially important in transportation applications where an aerodynamic shape is important.
With such significant fuel savings possible, some analysts believe it is only a matter of time before we see carbon fibres in large volume production cars but there are many technical and commercial problems to overcome first.
Carbon fibres are not as easily processed as polyester or the more common fibres. For low volume production, such as specialist sports cars, goods vehicles, trains and aircraft, composites are feasible, but when largescale mass production is considered, there are at present, prohibitive cost and technical difficulties.
The production of carbon fibres is expected to grow by about 10% annually at least until the year 2001 all over sectors. Disadvantages of composites include susceptibility to impact damage, limited temperature and moisture resistance in some cases and at present limitations on repairability and joining techniques.
Market For Automotive Textile
The automotive textile market size in terms of volume for the year 2011-2015, and forecast of the same for the year 2020. It highlights potential growth opportunities in the coming years, while also reviewing the market drivers, restraints, growth indicators, challenges, market dynamics, competitive landscape, and other key aspects with respect to the automotive textile market.
Asia-Oceania is estimated to be the largest market for automotive textile. China, India, Japan, and South Korea are the main contributors to the automotive textile market in Asia-Oceania.
The global market for automotive textiles will be worth US$31.75 billion in 2024, predicts the latest study from Grand View Research Inc. of San Francisco, California, USA, having risen from a value.
Future Scope And Conclusion
There is a significant potential for profitable application of automotive textiles owing to growing global vehicle production volume and increasing use of textile in vehicles due to growing demand for lighter and more fuel-efficient vehicles.
As composites possess a big role in reducing the weight future possibilities of including nanomaterials as textile reinforcement may be developed.
In the European Community, the ELV Directive expects future vehicles to be designed and manufactured for efficient dismantling, reuse, and recycling at the end of life.
The development of technical fabric incorporating antistatic, antimicrobial, or even self-cleaning attributes into interiors can provide further product convenience and satisfaction to driver and passenger. New opportunities exist for e-textiles or smart materials to provide and react to valuable information; for example, sensors may alert the seat to adjust to occupant’s body size, temperature, and driving alertness.
It is foreseeable that in future the importance of comfort in the car will be even more significant as one of the main factors in the competition between car manufacturers, which will increase the demand for technical textiles for use in car seats, approximately from 3.5 kg per car. Textiles for car seats possess interesting market potential.