Nikhil Bhosale*,Vishnu Pareek are Department of Diploma in Fashion & Clothing Technology and Shrikant Eklahare, Vardhaman chougule are Faculty of Textile Technology, D.K.T.E Society’s, Textile & Engineering Institute, Ichalkaranji-416115, India.
Corresponding Author Email Id:[email protected]
Today, textiles can be seen working at the interdisciplinary level by offering the several technical advantages that may not be accumulated in a single material traditionally known. The technical textile is the most important and huge sector for various product development for many functional applications. Mobiltech (automotive applications such cars, trucks, buses, trains, ships and aerospace) represent the largest single end-use area for technical textiles. Composite materials are one such class of materials that play a important role in aerospace components. They are particularly attractive to aviation and aerospace applications because of their exceptional strength and stiffness-to-density ratios and superior physical properties. Based on the applications, textiles used in aerospace are broadly divided into aircraft textiles and space textiles. The current article focuses on aerospace textiles, various composites application and their application in aviation, aircraft textiles and space textiles.
Technical textiles are the emerging field in India and globally. They are defined as textile materials and products made principally for their functional properties and technical performance and rather than their aesthetic or decorative characteristics. On the basis of the functional, technical performance and end use, technical textiles are classified in to 12 categories namely Agrotech Buildtech, Clothtech , Geotech, Hometech, Indutech (Filtration, cleaning and industrial), Meditech, Mobiltech, Oekotech (Environmental protection), Packtech (Packing materials), Protech, Sportech. This clearly shows us that the technical industry is not a single industry, it caters to a wide gamut of industries right from agriculture to automobiles to construction activities, among others.All these factors offer a convincing reason for the buyers and sellers of technical textiles to keep their focus on India and develop a rational strategy to seize the emerging opportunities. The technical textile market in India was worth Rs417.6 bn (US$10.4 bn) in 2007/08, and this is set to grow to Rs701.5 bn in 2012/13 . Further, as per an internal document prepared by the textile ministry, it is estimated that the technical textile market would grow to Rs.78, 060 Cr. by 2014-15 with an annual growth rate of 14 %. The mobiltech segment’s growth depends largely on the growth of the automotive sector in India, which has been brisk in recent years. India’s mobiltech segment is hence expected to grow at a rate of 17% to US$ 1,870 Million by 2016-17 as per estimates of the Working Group on Textiles and Jute Industry, Ministry of Textiles, Government of India. Aerospace is one of important technical textile subdivision of Mobiltech . Aerospace is compression of Aeronautics and Space flight. Aerospace textile covers special finished products to engineered textiles. It includes the textile containing articles for specific functional necessities to work in aircrafts, space suits, space shuttles, lunar and mars mission, and space transportation. The design, manufacture and applications of textile composites in space and aerospace have become one of the most leading aspects in present-day textiles.
- Space and its Environment
Knowledge about the space and its environmental conditions is a mandatory before entering into developing aerospace textiles. The outer space is very complex and causes numerous health risks. Generally, the outer space environment is space or vacuum surrounds the upper most part of earth and also other objects in universe. In space the pressure is zero where as at sea level in earth the pressure is 101 kilopascals. Due to the absence of external pressure, which in turn helps in balancing the internal pressure of body fluids and gases, it can rip apart fragile tissues such as eardrum and capillaries etc. Further lack of oxygen to the brain leads to immediate unconsciousness in less than 15 seconds. The temperature range found in outer space provides a second major hazard for humans. Electrically charged particle, ultraviolet radiation, and micrometeoroids are the other environmental problems encountered in outer space. Hence, there is a need for a system to determine, detect and prevent certain level of radiations, pressures and temperatures encountered by the astronauts to keep him alive in that environment.
- Aerospace Materials
The most successful materials employed for manufacturing of aerospace textile and structures are composites. A composite is commonly defined as a combination of two or more distinct materials, each of which retains its own distinctive properties, to create a new material with properties that cannot be achieved by any of the components acting alone. Composites are often stronger than conventional materials and weigh less. Composites are formed by commonly incorporate a structural fibre and a plastic, this is known as Fibre Reinforced Plastics, or FRP. The fibre provides the structure and strength to the composite, while a plastic polymer holds the fibre together.
3.1 Raw Materials Employed
1. Carbon Fibres
It is the material consisting of extremely thin fibres about 0.0002 – 0.0004” in diameter and contains mostly carbon atoms as it is produced as the by-product during the cracking process of crude oil. It is also called as graphite fibre. These fibres have excellent tensile strength, heat resistance and chemical resistance (4). The very first commercial use of carbon fibres is often attributed to Thomas Edison’s carbonization of cotton and bamboo fibres for incandescent lamp filaments (5). However, practical commercial use of carbon fibres for reinforcement applications began in the late 1950s with the pursuit of improved raw materials for the manufacture and design of special utility components of aviation machine, space rockets. Activity increased rapidly during the 1960s and 1970s to improve the performance/price ratio of carbon fibres. Much of this effort focused on evaluation of various precursors, since carbon fibre can be made from almost anything that yields a quality char upon pyrolysis. Donnet and Bansal (6) present a good overview of various researchers’ efforts to evaluate different precursors, including PAN (polyacrylonitrile), pitch, rayon, phenol, lignin, imides, amides, vinyl polymers, and various naturally occurring cellulosic materials. Carbon fibres are available in many of the same formats as glass fibre. These formats include continuous filament spooled fibre, milled fibre, chopped fibre, woven fabrics, felts, veils, and chopped fibre mattes.
2. E- Glass
E- Glass or electrical grade was originally developed for stand-off insulators for electrical wiring. It was later found to have excellent fibre forming capabilities and is used almost exclusively as the reinforcing phase in the material commonly known as fibreglass. Glass is extensively used in modern composites, have high tensile strength, but very brittle and extremely sensitive to cracks and defects. When used in composite plastic matrix protects its surface and prevents crack formation, which produces a strong composite. Glass is also used for its low cost. It comes in different types e.g. A, C, D, E. E-Glass, gives special electrical properties, dimensional stability, moisture resistance and low cost. S-Glass has higher tensile strength, high elastic modulus and better thermal stability but also expensive. It is used in advance composites. C-glass gives chemical resistance. D- Glass is improved form of E-glass.
3. Kevlar fibres
The DuPont Company invented aramid fibres in the 1960’s as part of their continuing research into all types of nylon (polyamide) fibres. DuPont found that by making the polymer highly aromatic (that is, using materials containing many benzene rings) a very stiff and strong fibre could be formed. The chemical structure of Kevlar shows the benzene rings along the polymeric backbone. (See Figure) These materials were called “aramids” from a contraction of their chemical description -aromatic polyamides. They are:
• Heat resistant
• High strength and modulus.
• Good resistance to abrasion.
• Good fabric integrity even at elevated temperatures.
• Corrosion resistance.
Kevlar fibres are known for the ability to provide quality and consistency, which are critical for aerospace applications. Kevlar fabrics are used in containment wraps, which perform the important role in preventing the broken engine blades from damaging the aircraft or entering the compartment of the passengers.
4. Alumina-boria-silica fibres
Nextel is the trade name for Alumina-boria silica fibres. Retain strength Flexibility with little shrinkage even at continuous temperatures up to 2012°F (1100°C).
5. Silicon carbide fibre
These fibres are similar to carbon fibres. Major properties are heat resistance, corrosion resistance, elasticity and withstand temperature as high as 1500°C.
6. Nylon fibre
Nylon 6,6 is made of hexamethylene diamine and adipic acid, which give nylon 6,6 a total of 2 carbons. They are heat resistance, friction resistance and melting point of 256°C (7,8).
B. Matrix Materials
Matrices are the essential material used to embed fibres and hold them in particular positions and orientations in order to provide the composite structural integrity. It is the capability of the matrix to transfer stresses which determines the degree of realization of mechanical properties of fibres and final performance of the resultant composites. Stress-strain behavior and adhesion properties are important properties are important criteria which control the ability of the matrix to transfer stresses. The chemical properties are generally determined by this plastic component.
The matrix is mostly plastics generally polymers which can be grouped into two categories:
Unsaturated polyester resins have been in use for decades for the production of the glass fibre reinforced plastics for many industrial applications. During recent years, because of better toughness, appropriate stress – strain behaviour, indefinite shelf life and reprocessibilty, engineering thermoplastics are emerging as promising products for matrix materials. The most widely used thermoset resin is epoxy. Epoxy resins are ideal for high temperature applications. They offer versatility, broad range of physical properties, mechanical capabilities and processing conditions. Depending on manufacturing conditions, epoxy resins can provide toughness, chemical and solvent resistance, flexibility, high strength, and hardness, creep and fatigue resistance, good fibre adhesion, heat resistance, and excellent electrical properties. Metal and Ceramics matrix materials are also researched and used for the manufacturing of composites. The metal matrix composites offer higher modulus of elasticity, ductility, and resistance to elevated temperature than polymer matrix composites. But, they are heavier and more difficult to process.
- Application Of Aerospace Textiles
Based on the applications, textiles used in Aerospace are broadly divided into Aircraft Textiles and Space Textiles.
4.1 Aircraft Textiles
The utility of composites in various aircrafts had predominantly increased due to the properties like strength, resistance to heat, chemical and harmful radiations, specific modulus, etc. Though the percentage of usage may vary they vastly improve the strength, performance and fuel economy, which are the credit for the air craft.
The textile articles being used in aircrafts are mainly for the below purposes:
- Wings, Body Parts
- Upholstery fabrics
- Aerodynamic fairings
- Wall covers
- Head set
- Floor carpet / covering
- Seat Cover
A-380 COMPOSITE COMPONENTS
Properties of technical textile for spacecraft are:
- High specific modulus & Strength
- Resistant to chemicals and organic solvents
- Good fatigue.
- Thermal insulated and resistant.
- Impact and stress resistant
- Better dimensional stability& conformability.
- Low flammability & Non-sensitive to harmful radiations.
Most of the US commercial jets have their brakes made from carbon composites as they are the only once, which can withstand the high temperatures generated, if the take off is aborted all of a sudden. Tyre cords of jet aero planes are made up of Nylon 6,6, of thickness 840 D, since they require to withstand strong pressure and frictional heat developed at the time of landing. Kevlar nonwoven felt liners are being used as fire barriers to cover urethane foam seats on all the air craft’s so as to prevent the production of highly toxic cyanide gases, when such foams burn during the accidents. Carbon and other high performance fibres are used in the rocket exhausts and nose cone covers for space shuttle, so as to protect them from heat, air friction during launch and re entry.
4.2 Space Textiles
Clothing used in space craft’s by astronauts is generally named as Space Suit. The environment faced by the astronauts are very complex in space when compared to the earth’s, where the gravitational attraction holds atmosphere comprising a mixture of gases like nitrogen, oxygen, carbon dioxide and thick form of water vapour and this atmosphere protects us from various factors. Thus, there is a need for a system to protect, determine, detect and prevent certain level of radiations, pressures and temperatures encountered by the astronauts to keep him alive in that environment. A space suit is a complex system of equipment, specially designed to protect and keep a person comfortable in the rough environment of outer space.
Some of the Properties of a space suit must possess are the following:
1. Lighter in weight.
2. Flexible in handling.
3. Soft in touch.
4. Comparable in strength with metal.
5. Modifiable in size and shape.
6. Thermal insulated and thermal resistant.
7. Chemical Resistance
A. Design of an Extra Vehicular Mobility Unit (EMU)
An Extra Vehicular Mobility Unit (EMU) was designed by the NASA Engineers. It consists of 14 layers of structures to perform random functions such as thermal resistant, vapour absorbing and impact resistant layers. The inner layers of the suit do activities like cooling and ventilation garment. An EMU consists of wide operations in it like; Drink bag, communication systems, TV camera and lights.
First Layer: It is made up of knitted form of Nylon tricot is lined
Second Layer: Spandex material fabric (a poly-urethane elastic thread) with plastic tubing is laced.
Third Layer: It is a Urethane-coated nylon fabric layer called the pressure bladder layer
Fourth Layer: Over the third layer a pressure-restraining layer made of Dacron, is laced. These two layers are employed to protect the astronauts from pressures balancing both internal and external pressures.
Fifth Layer: Above those two layers, a thin liner of nylon coated with Neoprene Nylon Ripstop is placed.
Sixth To Twelfth Layer: Followed by a series of 7 layers, thermal micrometeoroid garment of aluminized Mylar laminated with Dacron. These 7 layers are thermal insulated, protecting the astronaut from heat phenomenon and impact resistant protecting from meteoroids.
Thirteenth and Fourteenth Layer: The final or the outer layer of space suit, which is exposed to various radiations, is made of a blend of Goretex, Kevlar and Nomex materials (9,10).
B. G- Suit
A g-suit, or the more accurately named anti-g suit, is a flight suit worn by aviators and astronauts who are subject to high levels of acceleration force (g). Generally, a g-suit is composed of inflatable bladders, containing air or liquid that can be pressurized using a g-sensitive valve and held firm to legs and abdomen under higher values of g (gravitational force). The principle desired function of g-suit is to resist the blood draining from brain and upper body parts to legs of aviators. The initial effect of blood pooling in lower parts is a reduced level of vision termed as grey- out (= browning of scene) called g-induced loss of consciousness (g- LOC). Black-out and g-LOC has caused a number of fatal aircraft accidents (11).
It is effectively contributing in aerospace motion for men and materials. Parachutes help the safe decent of person or material from aerospace to ground surface. Generally, a parachute composes of thin lightweight fabric, supporting tapes and suspension lines. Nylon, polyester, Kevlar and Nomex fibre types are used in fabric for parachute. It is flexible and weather resistance.
- Safety And Environmental Factors
5.1 Safety systems
Safety systems are inevitable for all aircrafts. The safety systems while ensuring safety of the aircraft / aircrew / traveler, do not directly contribute towards operational capability of the aircraft. Their addition into the aircraft thus brings a weight overhead and it is a challenging task for the designer to minimize their weights. Fabrics are now universally and extensively used in the design of safety system of aircraft due to their light weight and a host of other favorable properties. Eg: Life Jackets, Survival Packs.
5.2 Environment or Protective system
Fabrics are also used in other aerospace application like, protective systems viz; flying clothing, fire proof/ fire retardant zones, pressure suits etc and environment systems viz; passenger seats, cabin upholstery, pressure suits, camouflage covers.
Aerospace textiles are the one of most important sector which is mainly built to safe guard the life of an aerospace traveler. The ultimate aim of the Aerospace textiles is to protect the human body from a disaster or from the high rays in the upper layer of the atmosphere and spaces. The development of these textiles is a great boon to the present-day textile industry. Presently, these kinds of textiles are making a significant contribution to the increasing market for textiles. Although a lot of aerospace programmes have started using advanced composites, lesser industries are aware of the development in this ever-growing area of composite technology. This is due to lack of access to this technology and non implementation of the locally manufacturing composites at a reasonable cost. There is lot of scope for research and development in aerospace textiles and also for horizontal and vertical growth in aerospace textiles to save the life.
Prof. Shrikant Eklahare is a Faculty of Textile Finishing, D.K.T.E Society’s, Textile & Engineering Institute and UDCT (University Department of Chemical Technology) Maharashtra, India.
Prof. Vardhaman chougule is the Faculty of Textile Technology, D.K.T.E Society’s, Textile & Engineering Institute Ichalkaranji-416115, India.
The authors wish to thank the Shahanawaj Mujawar , Avadhut Rane, Abhi Kamble and Bajirao Jadhav for their continuous support.
4. Paul J. Walsh, ASM Handbook, Composites, 21, 2001, Pg. 35-40.
5. T. Edison, U.S. Patent 223,898, 1880
6. J.B. Donnet and R.C. Bansal, Carbon Fibres, 2nd ed., Marcel Dekker, 1990
7. https://www.fibre2fashion.com/industry-article/25/2473/application-of-composites-in-aerospace-textiles1.asp published on March 19, 2010.
8. M.V.Ragavendra Pavan, Karthik Macharla, Dr. J.Hayavadana, The Indian Textile Journal, March, March 2009, Pg.71-77
9. Nicole C. Jordan, Joseph H. Saleh, Dava J. Newman, Acta Astronautica, 59 (12), 2006, Pg 1135–1145.