Nabi Final

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    Submitted to, Name: S.Mehatab.Nabi

    Dr. Kuruvilla Joseph, ID No: SC11B048

    HOD, Dept. of Chemistry



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    3)Composite materials in aerospace fields

    4)Some more applications


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    The need for the highly effective and efficient material which should be

    concerned with the ecologyconcerned world of finite resources has led

    advanced composites to be one of most important materials in the high

    technology revolution in the world today.

    A composite material typically consists of relatively strong, stiff fibres

    in a tough resin matrix. Wood and bone are natural composite materials:

    wood consists of cellulose fibres in a lignin matrix and bone consists of

    hydroxyapatite particles in a collagen matrix. Better known man-made

    composite materials, used in the aerospace and other industries, are

    carbon- and glass-fibre-reinforced plastic which consist of carbon and

    glass fibres, both of which are stiff and strong, but brittle, in a polymer

    matrix, which is tough but neither particularly stiff nor strong. Very

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    simplistically, by combining materials with complementary properties in

    this way, a composite material with most or all of the benefits is

    obtained with few or none of the weaknesses of the individual

    component materials.

    The primary benefits that composite components can offer are reduced

    weight and assembly simplification. Composite materials are

    particularly attractive to aviation and aerospace applications because of

    their exceptional strength and stiffness-to-density ratios and superior

    physical properties. The increased availability of these light, stiff and

    strong materials has made it possible to achieve a number of milestones

    in Aerospace technology. Nowadays, a significant amount of advanced

    polymer composites is used for military and commercial aircraft and

    satellite components. Usage of such materials will reduce fuel

    consumption, improve efficiency and reduce direct operating costs of

    aircrafts. Composite materials are one such class of materials that play a

    significant role in current and future aerospace components.

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    Composite materials, often shortened to composites or called

    composition materials, are engineered or naturally occurring materials

    made from two or more constituent materials with significantly different

    physical or chemical properties which remain separate and distinct at themacroscopic or microscopic scale within the finished structure.

    Composite is composed of a matrix as a binder (continuous phase)

    containing a filler as reinforcement (discontinuous phase). The matrix

    material surrounds and supports the reinforcement materials by

    maintaining their relative positions. The reinforcements impart their

    special mechanical and physical properties to enhance the matrix

    properties. There should be a definite interface between the matrix and

    reinforcement, usually of zero thickness. The properties of composites

    depend upon those of the individual components and on their interfacial

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    compatibility. The strength of the composite depends on the amount,

    arrangement and type of fiber reinforcement in the resin. These

    composite materials are anisotropic in nature.

    The composites are classified based on the matrix into:

    1) Metal matrix composites

    2) Ceramic matrix composites

    3) Polymer matrix composites

    On the basis of reinforcement, it is classified into:

    1) Particle reinforced composites

    2) Structural composites

    3) Fiber reinforced composites

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    Composites in aerospace field

    Fiberglass composites

    The most extensively used fiber in aerospace field is fiberglass.

    Fiberglass consists of glass fibers embedded in a resin matrix. Main

    properties which led to its popularity is light weight, high strength and

    non metallic properties. In aerospace application, fiberglass composite is

    widely used on aircraft parts that do not have to carry heavy loads or

    work under good stress. Usually, it always used for interior parts such as

    window surrounds and storage compartments, as well as for wing fairing

    and wing fixed trailing edge panels.

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    Fiberglass was first used widely in the 1950s for boats and

    automobiles, and today most cars have fiberglass bumpers covering a

    steel frame. Fiberglass was first used in the Boeing 707 passenger jet in

    the 1950s, where it comprised about two percent of the structure. By the

    1960s, other composite materials became available, in particular boron

    fiber and graphite, embedded in epoxy resins. The U.S. Air Force and

    U.S. Navy began research into using these materials for aircraft control

    surfaces like ailerons and rudders. The first major military production

    use of boron fiber was for the horizontal stabilizers on the Navy's F-14

    Tomcat interceptor. By 1981, the British Aerospace-McDonnell Douglas

    AV-8B Harrier flew with over 25 percent of its structure made of

    composite materials.

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    One of the most common grades of fiberglass is E-type. E is

    representing for electrical because its chemical composition formulate

    an excellent electric insulator. So, it is most favorable application for

    small passenger aircraft parts, aircraft interiors and aircrafts secondary

    parts such as radomes and rocket motor casings. E-glass provides a high

    strength-to-weight ratio, good fatigue resistance, wonderful dielectric

    properties, and retention of 50%, tensile to 600F, excellent chemical

    corrosion and environmental resistance. Fiberglass being a selected

    material in several applications such as corrosion, low volume

    production, very large parts, contoured or rounded parts and any parts

    required high specific strength. By using fiberglass, the parts can be

    modified to obtain the strength and or stiffness as required by tactically

    inserting materials and familiarizing the fiber direction. E-glass also the

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    most economical fiberglass for composite and provide adequate strength

    in almost appliances at a quite low cost.

    Carbon fiber composites

    Carbon fiber (Graphite fiber) is an extremely strong thin fiber about

    0.0050.010 mm in diameter and composed mostly of carbon atoms. It

    is produced from the pitch, which is produced as a byproduct during the

    cracking process of crude oil. It is known for its excellent tensilestrength, heat resistance and chemical rsistance. Carbon fiber

    reinforced plastics (CFRP) are stiffer than fiberglass. Typically, CFRP

    has a modulus of the order of three times that of GRP, one and a half

    times that of a Kevlar composite and twice that of aluminum alloy. Its

    strength is three times that of aluminum alloy, approximately the same

    as that of fiberglass, and slightly less than that of Kevlar composites.

    Aerospace CFRP does, however, suffer from some disadvantages. It is

    a brittle material and therefore does not yield plastically in regions of

    high stress concentration. Its strength is reduced by impact damage

    which may not be visible and the epoxy resin matrices can absorb

    moisture over a long period which reduces its matrix dependent

    properties, such as its compressive strength; this effect increases with

    increase of temperature.

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    (NASA) for use in aircraft parts. Temperatures as high as 1650C are

    anticipated for the turbine inlets of a conceptual engine based on

    preliminary calculations. In order for materials to withstand such

    temperatures, the use of Ceramic Matrix Composites (CMCs) is

    required. The use of CMCs in advanced engines will also allow an

    increase in the temperature at which the engine can be operated, leading

    to increased yield. Although CMCs are promising structural materials,

    their applications are limited due to lack of suitable reinforcement

    materials, processing difficulties, lifetime and cost.

    Spider silk fibers

    Spider silk is another promising material for composite material usage.

    Spider silk exhibits high ductility, allowing stretching of a fiber up to

    140% of its normal length. Spider silk also holds its strength at

    temperatures as low as -40C. These properties make spider silk ideal

    for use as a fiber material in the production of ductile composite

    materials that will retain their strength even at abnormal temperatures.

    Ductile composite materials will be beneficial to an aircraft in parts that

    will be subject to variable stresses, such as the joining of a wing with the

    main fuselage. The increased strength, toughness and ductility of such a

    composite will allow greater stresses to be applied to the part or joining

    before catastrophic failure occurs.

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    Synthetic spider silk based composites will also have the advantage that

    their fibers will be biodegradable.

    Hybrid composite steel sheets

    Another promising material can be stainless steel constructed with

    inspiration from composites and nanontech-fibers and plywood. The

    sheets of steel are made of same material and is able to handle and tool

    exactly the same way as conventional steel. But is some percent lighter

    for the same strengths. This is especially valuable for vehicle

    manufacturing. Patent pending, Swedish company Lamera is a spinoff

    from research within Volvo Industries.
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    Honeycomb structures are natural or man-made structures that have the

    geometry of a honeycomb to allow the minimization of the amount of used

    material to reach minimal weight and minimal material cost. Honeycomb

    shaped structure provides a material with minimal density and relative high

    out-of-plane compression properties and out-of-plane shear properties

    There are three types of honeycomb structures:

    1)Fiber glass 2)aluminum 3)Graphite Honeycomb stuctures.

    This is structure of Aluminum Honeycomb structure.

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    Some applications by famous companies

    The structural complexity of a Sea King helicopter rotor blade is

    considerable. It incorporates CFRP, GRP, stainless steel, a honeycomb

    core and foam filling. An additional advantage of the use of composites

    for helicopter rotor blades is that the moulding techniques employed

    allow variations of cross-section along the span, resulting in substantial

    aerodynamic benefits. This approach is being employed in the

    fabrication of the main rotor blades of the GKN Westland Helicopters

    EH 101.

    A composite (fiberglass and aluminum) is used in the tail assembly of

    the Boeing 777 while the leading edge of the Airbus A310-300 and

    A320 fin assembly is of conventional reinforced glass fiber construction,

    reinforced at the nose to withstand bird strikes. A complete composite

    airframe was produced for the Beechcraft Starship turboprop executive

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    aircraft which, however. was not a commercial success due to its canard

    configuration causing drag and weight penalties.

    FUTURE USESThe environmental case for developing our understanding and

    increasing our exploitation of composites is compelling .The Stern

    Review, 2006,identified that 1.6% of globalgreenhouse gas emissions

    come from aviation but that the demand for air travel will rise with our

    income.To combat the environmental threat that aviation poses, the

    Advisory Council for Aeronautical Research in Europe in 2002 laid out

    targets to reduce the emission of CO2 (animport and greenhouse gas)

    from an aircraft by 50% by 2020

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    Due to their reduced weight and almost the same strength, composite

    materials have an advantage over conventional metallic materials.

    Although, currently it is expensive to fabricate composites, research is

    being done to reduce initial implementation costs and address the issue

    of non-biodegradability of current composites. If those few limitations

    are overcome, then definitely composites are going to replace heavy

    metals and become materials for the future.