COMPOSITES BY ALANKAR G. MHATRE FINAL YEAR B.TECH
CONTENTS• Introduction• What are composites?• Composition of composites• Types of composites• Manufacturing and forming methods• Applications• Composites Todays Material of Choice• Properties of composites• Key manufacturers of composite products• References
INTRODUCTION TO COMPOSITES You might be know we all are surrounded by composites in day today life. Everybody comes across composites in his daily life.You might be playing tennis or badminton with a "graphite racket", You might have a "carbon bike" ,your bike breaks are made of composite, several parts of your car body are also made of composites. Def :-A composite is a material made up of two or more different materials that are combined in a way that allows the materials to stay distinct and identifiable. The purpose of composites is to allow the new material to have strengths from both materials.• Composites can be easily found in nature. Wood is an example of a composite . Another natural composite is rock and sand, materials used in concrete.
Properties of composites like stiffness, thermal expansion etc. can be varied continuously over a broad range of values using appropriate fiber , resin and fabrication mechanism. The technical textile material in the composites is the fiber glass, aramid and carbon fiber.• Fibre glass dominates the composites industry as a preferred reinforcement fibre, with a share of around 85%-90%. Other reinforcement fibers like carbon fibre and aramid fibre are sparingly used in India.
WHAT ARE COMPOSITES? Composites are created by combining two or more materials to produce a new material that retains important properties from the original elements . Reinforcing fibers give composites the attributes of high strength and stiffness. In textile composites fibers are surrounded by a choice of polymers that act as a support system. Composites are produced by reinforcing a resin matrix (thermoplastic/thermoset) with fibres like glass fibre, aramid, carbon fibre and/or natural fibres.
A common example of a composite is concrete. It consists of a binder as a cement and a reinforcement as a gravel.
COMPOSITION OF COMPOSITES The individual materials that make up composites are called constituents. Most composites have two constituents, a matrix and reinforcement. Composite materials are usually classified by the type of reinforcement they use. This reinforcement is embedded into a matrix that hold it together. The reinforcement is used to strengthen the composite. Composite properties are best in the direction of the fibers. Perpendicular, or transverse, to the fibers, the matrix properties dominate because load must be transferred by the matrix every fiber diameter.
Reinforcement The reinforcement is usually much stronger and stiffer than the matrix, and that gives the composite its good properties. The matrix hold the reinforcements in an orderly pattern, the matrix also helps to transfer load among the reinforcements. Reinforcements basically come in three forms: particulate, discontinuous fiber, and continuous fiber. PARTICLE AS A REINFORCEMENT:-A particle has roughly equal dimensions in all directions, though it doesnt have to be spherical. Gravel, micro balloons, and resin powder are examples of particulate reinforcements. CONTINUES FIBER AS A REINFORCEMENT:-Reinforcements become fibers when one dimension becomes long compared to others. DISCONTINUES FIBERS AS A REINFORCEMENT: -:Discontinuous reinforcements (chopped fibers, milled fibers, or whiskers) vary in length from a few millimeters to a few centimeters. Most fibers are only a few microns in diameter, so it doesnt take much length to make the transition from particle to fiber.
MATRIX Matrix materials are usually some type of plastic, and these composites are often called reinforced plastics. There are other types of matrices, such as metal or ceramic, but plastics are the most . The two most common plastic matrices are epoxy resins and polyester resins.
TYPES OF COMPOSITES Metal matrix composites (MMC) Ceramic matrix composites (CMC) Polymer matrix composites (PMC)
Metal matrix composites (MMC)• Metal matrix composites (MMCs) are a subgroup of composite materials. Composition:- MMC are made by dispersing a reinforcing material into a metal matrix. The reinforcement surface can be coated to prevent a chemical reaction with the matrix. -- For example, carbon fibers are commonly used in aluminum matrix to synthesize composites showing low density and high strength. However, carbon reacts with aluminum to generate a brittle and water-soluble compound Al4C3 on the surface of the fiber. To prevent this reaction, the carbon fibers are coated with nickel or titanium boride. Matrix:- In structural applications, the matrix is usually a lighter metal such as aluminum, magnesium, or titanium, and provides a compliant support for the reinforcement. In high temperature applications, cobalt and cobalt-nickel alloy matrices are common.
Reinforcement to MMC The reinforcement can be either continuous, or discontinuous.. Discontinuous MMC can be isotropic, and can be worked with standard metalworking techniques, such as extrusion, forging or rolling. In addition, they may be machined using conventional techniques, but commonly would need the use of polycrystalline diamond tooling (PCD).
Continuous reinforcement uses monofilament wires or fibers such as carbon fiber or silicon carbide. One of the first MMC used boron filament as reinforcement. Discontinuous reinforcement uses "whiskers", short fibers, or particles. The most common reinforcing materials in this category are alumina and silicon carbide.
Ceramic matrix composites Ceramic matrix composites (CMCs) are a subgroup of composite materials as well as a subgroup of technical ceramics. They consist of ceramic fibers embedded in a ceramic matrix, thus forming a ceramic fiber reinforced ceramic (CFRC) material. The matrix and fibers can consist of any ceramic material, whereby carbon and carbon fibers can also be considered a ceramic material. Generally, CMC names include a combination of type of fiber / type of matrix. For example, C/C stands for carbon-fiber-reinforced carbon (carbon/carbon), or C/ SiC for carbon-fiber-reinforced silicon carbide.
Ceramic compositesREINFORCEMENT- SiC (Silicon carbide)MATRIX-Cu Metal
Polymer Matrix composites Polymer matrix composites are the imp and third subgroup of composites. It is also referred as fibre-reinforced plastics(FRP) In these fibre-reinforced plastics, the plastic is reinforced with fibers to make a light and strong material. The material in which the fibres are embedded, is called the matrix, while the fibres are called the reinforcement. The matrix can basically be any type of plastic: epoxy, polyester, vinyl ester, polypropylene (PP).
Glass fabrics Plain weave glass fabricThe fibres are typically glass, carbon (graphite) or aramid (tradename Kevlar). The fibre reinforcement can take any form: a matof short chopped fibres, a woven fabric, a unidirectionalarrangement of fibres, a braid, a knit.
Manufacturing and forming methods of MMC MMC manufacturing can be broken into three types: solid, liquid, and vapor. Solid state methods:- 1)-Powder blending and consolidation (powder metallurgy):- Powdered metal and discontinuous reinforcement are mixed and then bonded through a process of compaction, degassing, and thermo-mechanical treatment (possibly via hot isostatic pressing (HIP) or extrusion). 2)-Foil diffusion bonding:-Layers of metal foil are sandwiched with long fibers, and then pressed through to form a matrix.
Liquid state methods FOR MMC 1)-Electroplating / Electroforming:- A solution containing metal ions loaded with reinforcing particles is co-deposited forming a composite material. 2)-Stir casting:- Discontinuous reinforcement is stirred into molten metal, which is allowed to solidify. 3)-Squeeze casting:- Molten metal is injected into a form with fibers preplaced inside it. 4)-Spray deposition:- Molten metal is sprayed onto a continuous fiber substrate. 5)-Reactive processing:- A chemical reaction occurs, with one of the reactants forming the matrix and the other the reinforcement.
Vapor deposition Physical vapor deposition: The fiber is passed through a thick cloud of vaporized metal, coating it.
Manufacturing procedures for Ceramic matrix composites1)-Matrix deposition from a gas phase:- Chemical vapor deposition (CVD) is well suited for this purpose. In the presence of a fiber perform, CVD takes place in between the fibers and their individual filaments and therefore is called chemical vapor infiltration (CVI). One example is the manufacture of C/C composites: a C-fiber perform is exposed to a mixture of argon and a hydrocarbon gas (methane, propane, etc.) at a pressure of around or below 100 kPa and a temperature above 1000 °C.
2)-Matrix forming via pyrolysis of C- and Si-containing polymers- Hydrocarbon polymers shrink during paralysis, and upon out gassing form carbon with an amorphous, glass-like structure, which by additional heat treatment can be changed to a more graphite-like structure. Other special polymers, where some carbon atoms are replaced by silicon atoms, the so-called polycarbosilanes, yield amorphous silicon carbide of more or less stoichiometric composition.• Subsequent curing and pyrolysis yield a highly porous matrix, which is undesirable for most applications. Further cycles of polymer infiltration and pyrolysis are performed until the final and desired quality is achieved. Usually five to eight cycles are necessary . The process is called liquid polymer infiltration (LPI), or polymer infiltration and pyrolysis (PIP). Here also a porosity of about 15% is common due to the shrinking of the polymer. The porosity is reduced after every cycle.
APPLICATION OF COMPOSITES• Applications of Métal matrix composites (MMC)–• Carbide drills are often made from a tough cobalt matrix with hard tungsten carbide particles inside.• Some tank armors may be made from metal matrix composites, probably steel reinforced with boron nitride. Boron nitride is a good reinforcement for steel because it is very stiff and it does not dissolve in molten steel.• Honda , Toyotas automobiles has used aluminum metal matrix composite cylinder liners in some of their engines,• Specialized Bicycles has used aluminum MMC compounds for its top of the range bicycle frames for several years. Griffen Bicycles also makes boron carbide-aluminum MMC bike frames, and Univega briefly did so as well.• Some automotive disc brakes use MMC. Modern high-performance sport cars, such as those built by Porsche, use rotors made of carbon fiber within a silicon carbide matrix because of its high specific heat and thermal conductivity.
A typical composites material construction for helicopter blade
Applications Of ceramic matrix composites• Heat shield systems for space vehicles, which are needed during the re-entry phase, where high temperatures, thermal shock conditions and heavy vibration loads take place.• Components for high-temperature gas turbines such as combustion chambers, and turbine blades.• Components for burners, flame holders, and hot gas ducts, where the use of oxide CMCs has found its way.• Disks breaks and brake system components, which experience extreme thermal shock .
Applications of FRP or PMC• Fibre-reinforced plastics are best suited for any design program that demands weight savings, precision engineering, finite tolerances, and the simplification of parts in both production and operation. A moulded polymer artefact is cheaper, faster, and easier to manufacture than cast aluminum or steel artefact, and maintains similar and sometimes better tolerances and material strengths.• Overall reduction in production and operational costs, economy of parts results in lower production costs and the weight savings create fuel savings that lower the operational costs of flying the aero plane.
Design considerations PMC IN AIRCRAFT PARTS LIGHT WEIGHT
APPLICATION PMC IN RAILWAYS For passenger coach components. Components of coaches are generally made of glass fibre reinforced with polyesters/epoxies, phenolic resins.
Minardi Formula 1All Formula One race cars have a carbonfibre monocoque structure that protectsthe driver for all crashes.
BMC frame with carbon/epoxy pre-pregOne of the most well-known composite applications insports is the so-called "carbon bike". The frame consistsof carbon fibre-reinforced epoxy which makes theframe very stiff and lightweight.
BMW M6 with carbon fibre roofIn automotive applications, composites are all around us. Just asin sports applications, weight reduction is pushing the designers touse more and more composites. The examples are numerous.
Composites Todays Material of Choice It gives lower manufacturing costs, composite material continues to penetrate new markets and applications. For industries that traditionally use assemblies made from more traditional options such as steel, wood or concrete, composites offer a dynamic alternative – especially for those products that are difficult to assemble or costly to manufacture as a result of increasing steel pieces. Glass fibre as reinforcement dominates the sector of composites material with a share of 85-90%.• Composites are created by combining two or more materials to produce a new material that retains important properties from the original elements. Reinforcing fibers give composites the attributes of high strength and stiffness which in the industrial arena translates to high performance. These fibers are surrounded by a choice of polymers that act as a support system, transferring load between fibers and protecting the fibers from the operating environment.The burgeoning infrastructure sectors project involving highways, bridges, airports, buildings, and construction, power generation and transmission, telecommunications are expected to provide an impetus to the composites industry in India.
Composites can also deliver reduced manufacturing/assembly costs. Since liquid resin can flow into any shape, products with complex shapes can be made at a lower cost when compared to conventional methods using traditional materials.• Typically, complex shapes of metals or wood require labor intensive assembly of multiple pieces to create the product. Composites can provide ultimately the lowest cost alternative. The lower cost of unitized composite parts is particularly attractive for customers that purchase products assembled from many metallic pieces or have difficult-to-form shapes.
Properties of composite products Tensile strength of composites is four to six times greater than that of conventional materials like steel, aluminium etc. Improved torsion stiffness and impact properties . Higher fatigue endurance limit (up to 60% of the ultimate tensile strength) 30-45% lighter than aluminium structures designed for the same functional requirements . Lower embedded energy . Composites are less noisy while in operation and provide lower vibration transmission Composites are more versatile and can be tailored to meet performance needs and complex design requirements
Long life offers excellent fatigue, impact, environmental resistance and reduced maintenance. Composites enjoy reduced maintenance cost Composites exhibit excellent corrosion resistance and fire retardant capability Improved appearance with smooth surfaces and readily incorporable integral decorative melamine are other characteristics of composites• Composite parts can eliminate joints/fasteners, providing part simplification and integrated design. 25% reduction in weight 95% reduction in components by combining parts and forms into simpler moulded parts.
Key manufacturers of composite products:- 1. Saertex India – Saertex India is 100% subsidiary of Saertex. Saertex, is a major player in the stitch-bonded fabric segment. The company has six manufacturing facilities across the globe and the Indian facility at Pune is the seventh. Saertex India has production capacity of around 10,000 – 11,000 MT of composite fabric. Additionally, Saertex has 12 MT production.capacity for specialty fibres. Saertex is one of major suppliers of composite material for windmill blade fabrication. Saertex plans to enter automotive sector for development of composite based vehicle bodies (three- wheelers, buses and cars).
2.) DSM Engineering Plastics – DSM is one of the major players in high-performance composites. -DSM had a capacity of 7,000 MT in 2007 which was expected to scale up to 20,000 MT. 3) Kemrock Industries – Kemrock Industries has composite production capabilities like Pultrusion, Resin Transfer Moulding, Compression Moulding, Vaccum Resin Transfer Moulding, Centrifugal Casting, Filament Winding etc. for fibre-glass reinforced composites.• comprehensive dough moulding composites based manufacturing facility for specialty resins.