Composite materials (or composites for short) are engineered materials made from two or more constituent materials with significantly different physical or chemical properties and which remain separate and distinct on a macroscopic level within the finished structure. Materials are physical Substances used as inputs to production or Manufacturing.
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Background
The most primitive composite materials comprised straw and mud in the form of bricks for building construction; the Biblical book of Exodus speaks of the Israelites being oppressed by Pharaoh, by being forced to make bricks without straw being provided. Plywood is a type of Engineered board made from thin sheets of Wood, called plies or veneers Straw is an agricultural By-product, the dry stalk of a Cereal plant after the Grain or Seed has been removed In computer gaming, a MUD ( Multi-User Dungeon, Domain or Dimension) is a multi-player computer game that combines elements of A brick is a block of Ceramic material used in Masonry construction laid using mortar. Etymology According to the Online Etymology Dictionary, the word bible is from Latin biblia, traced from the same word through Medieval Latin and Late Latin Exodus ( Greek: έξοδος eksodos = "departure" is the second book of the Jewish Torah and of the Christian Old Testament. See also History of ancient Israel and Judah According to the Bible, the Israelites were the dominant group living in the Land of Israel. Pharaoh is the title given in modern parlance to the ancient Egyptian kings of all periods Bricks without straw is a phrase which refers to a task which must be done without appropriate resources The ancient brick-making process can still be seen on Egyptian tomb paintings in the Metropolitan Museum of Art[1]. Ancient Egyptian art refers to the style of painting sculpture crafts and architecture developed by the Civilization in the lower Nile Valley from 5000 The Metropolitan Museum of Art is an art museum located on the eastern edge of Central Park, along what is known as Museum Mile in New York City, The most advanced examples perform routinely on spacecraft in demanding environments. The most visible applications pave our roadways in the form of either steel and aggregate reinforced portland cement or asphalt concrete. Portland cement is the most common type of Cement in general usage in many parts of the world as it is a basic ingredient of Concrete, mortar, Stucco Asphalt concrete, normally known simply as Asphalt, is a Composite material commonly used for construction of pavement, Highways and Those composites closest to our personal hygiene form our shower stalls and bath tubs made of fiberglass. Fiberglass (also called fibreglass and glass fibre see Spelling differences) is material made from extremely fine Fibers of Glass. Solid surface, imitation granite and cultured marble sinks and counter tops are widely used to enhance our living experiences.
There are two categories of constituent materials: matrix and reinforcement. At least one portion of each type is required. 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. A synergism produces material properties unavailable from the individual constituent materials, while the wide variety of matrix and strengthening materials allows the designer of the product or structure to choose an optimum combination. Engineered composite materials must be formed to shape. The matrix material can be introduced to the reinforcement before or after the reinforcement material is placed into the mold cavity or onto the mold surface. The matrix material experiences a melding event, after which the part shape is essentially set. Depending upon the nature of the matrix material, this melding event can occur in various ways such as chemical polymerization or solidification from the melted state.
A variety of molding methods can be used according to the end-item design requirements. The principal factors impacting the methodology are the natures of the chosen matrix and reinforcement materials. Another important factor is the gross quantity of material to be produced. Large quantities can be used to justify high capital expenditures for rapid and automated manufacturing technology. Small production quantities are accommodated with lower capital expenditures but higher labor and tooling costs at a correspondingly slower rate. Most commercially produced composites use a polymer matrix material often called a resin solution. There are many different polymers available depending upon the starting raw ingredients. There are several broad categories, each with numerous variations. The most common are known as polyester, vinyl ester, epoxy, phenolic, polyimide, polyamide, polypropylene, PEEK, and others. Polyester is a category of Polymers which contain the Ester Functional group in their main chain Vinyl Ester, or Vinylester, is a resin produced by the esterification of an Epoxy resin with an unsaturated monocarboxylic acid. In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a Properties Thermosetting polyimides are known for thermal stability good chemical resistance excellent mechanical properties and characteristic orange/yellow color A polyamide is a Polymer containing Monomers of Amides joined by Peptide bonds They can occur both naturally examples being Proteins Polypropylene or polypropene ( PP) is a Thermoplastic Polymer, made by the Chemical industry and used in a wide variety of applications Chemical resistance PEEK also exhibits good chemical resistance in many environments including Alkalis The reinforcement materials are often fibers but also commonly ground minerals. The various methods described below have been developed to reduce the resin content of the final product, or the fibre content is increased. As a rule of thumb hand lay up results in a product containing 60% resin and 40% fibre, whereas vacuum infusion gives a final product with 40% resin and 60% fibre content. The strength of the product is greatly dependent on this ratio, so this increase in fibre content results in a dramatically stronger product.
Moulding methods
In general, the reinforcing and matrix materials are combined, compacted and processed to undergo a melding event. After the melding event, the part shape is essentially set, although it can deform under certain process conditions. For a thermoset polymeric matrix material, the melding event is a curing reaction that is initiated by the application of additional heat or chemical reactivity such as an organic peroxide. For a thermoplastic polymeric matrix material, the melding event is a solidification from the melted state. For a metal matrix material such as titanium foil, the melding event is a fusing at high pressure and a temperature near the melt point.
For many molding methods, it is convenient to refer to one mold piece as a "lower" mold and another mold piece as an "upper" mold. Lower and upper refer to the different faces of the molded panel, not the mold's configuration in space. In this convention, there is always a lower mold, and sometimes an upper mold. Part construction begins by applying materials to the lower mold. Lower mold and upper mold are more generalized descriptors than more common and specific terms such as male side, female side, a-side, b-side, tool side, bowl, hat, mandrel, etc. Continuous manufacturing processes use a different nomenclature.
The molded product is often referred to as a panel. For certain geometries and material combinations, it can be referred to as a casting. For certain continuous processes, it can be referred to as a profile.
Open moulding
A process using a rigid, one sided mould which shapes only one surface of the panel. The opposite surface is determined by the amount of material placed upon the lower mould. Reinforcement materials can be placed manually or robotically. A robot is a mechanical or Virtual Artificial agent In practice it is usually an electro-mechanical system which by its appearance or movements They include continuous fibre forms fashioned into textile constructions and chopped fibre. Fiber or fibre is a class of Materials that are continuous filaments or are in discrete elongated pieces similar to lengths of thread. A textile is a flexible material comprised of a network of natural or artificial Fibres often referred to as thread or Yarn. The matrix is generally a resin, and can be applied with a pressure roller, a spray device or manually. Resin, not to be confused with Rosin, is a Hydrocarbon Secretion of many Plants particularly coniferous trees. This process is generally done at ambient temperature and atmospheric pressure. Room temperature (also referred to as ambient temperature) is a common term to denote a certain Temperature within enclosed space at which humans are accustomed Two variations of open moulding are Hand Layup and Spray-up.
Vacuum bag moulding
A process using a two-sided mould set that shapes both surfaces of the panel. On the lower side is a rigid mould and on the upper side is a flexible membrane or vacuum bag. A vacuum bag is a bag made of strong rubber-coated fabric or Polymer film open at one end and used to bond or Laminate materials The flexible membrane can be a reusable silicone material or an extruded polymer film. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds Then, vacuum is applied to the mould cavity. This process can be performed at either ambient or elevated temperature with ambient atmospheric pressure acting upon the vacuum bag. Most economical way is using a venturi vacuum and air compressor or a vacuum pump.
Pressure bag moulding
This process is related to vacuum bag moulding in exactly the same way as it sounds. A solid female mould is used along with a flexible male mould. The reinforcement is place inside the female mould with just enough resin to allow the fabric to stick in place. A measured amount of resin is then liberally brushed indiscriminately into the mould and the mould is then clamped to a machine that contains the male flexible mould. The flexible male membrane is then inflated with heated compressed air or possibly steam. The female mould can also be heated. Excess resin is forced out along with trapped air. This process is extensively used in the production of composite helmets due to the lower cost of unskilled labour. A helmet is a form of Protective gear worn on the head to protect it from injuries a variation of the hat Cycle times for a helmet bag moulding machine vary form 20 to 45 minutes, but the finished shells require no further curing if the moulds are heated.
Autoclave moulding
A process using a two-sided mold set that forms both surfaces of the panel. On the lower side is a rigid mold and on the upper side is a flexible membrane made from silicone or an extruded polymer film such as nylon. Reinforcement materials can be placed manually or robotically. They include continuous fiber forms fashioned into textile constructions. Most often, they are pre-impregnated with the resin in the form of prepreg fabrics or unidirectional tapes. In some instances, a resin film is placed upon the lower mold and dry reinforcement is placed above. The upper mold is installed and vacuum is applied to the mold cavity. The assembly is placed into an autoclave pressure vessel. An autoclave is a pressurized device designed to heat aqueous solutions above their Boiling point at normal atmospheric pressure to achieve sterilization A pressure vessel is a closed container designed to hold gases or liquids at a Pressure different from the ambient Pressure. This process is generally performed at both elevated pressure and elevated temperature. The use of elevated pressure facilitates a high fiber volume fraction and low void content for maximum structural efficiency.
Resin transfer moulding (RTM)
A process using a two-sided mold set that forms both surfaces of the panel. The lower side is a rigid mold. The upper side can be a rigid or flexible mold. Flexible molds can be made from composite materials, silicone or extruded polymer films such as nylon. The two sides fit together to produce a mold cavity. The distinguishing feature of resin transfer molding is that the reinforcement materials are placed into this cavity and the mold set is closed prior to the introduction of matrix material. Resin transfer molding includes numerous varieties which differ in the mechanics of how the resin is introduced to the reinforcement in the mold cavity. These variations include everything from vacuum infusion (see also resin infusion) to vacuum assisted resin transfer molding. This process can be performed at either ambient or elevated temperature.
Other
Other types of molding include press molding, transfer molding, pultrusion molding, filament winding, casting, centrifugal casting and continuous casting. Transfer molding, like Compression molding, is a process where the amount of molding material (usually a Thermoset Plastic) is measured and inserted before Pultrusion is a continuous process of manufacturing of Composite materials with constant cross-section whereby reinforced Fibers are pulled through a Resin Casting is a manufacturing process by which a liquid material is (usually poured into a mold which Continuous Casting (also called Strand Casting is the process whereby molten steel is solidified into a "semifinished" billet bloom or slab for subsequent rolling in the finishing mills
Tooling
Some types of tooling materials used in the manufacturing of composites structures include invar, steel, aluminum, reinforced silicon rubber, nickle, and carbon fiber. Invar®, also known generically as FeNi36 ( 64FeNi in the US is a Nickel Steel Alloy notable for its uniquely low Coefficient Steel is an Alloy consisting mostly of Iron, with a Carbon content between 0 WikipediaNaming Silicone rubber is a Polymer that has a "backbone" of Silicon - Oxygen linkages the same bond that is found in Quartz, Glass Selection of the tooling material is typically based on, but not limited to, the coefficient of thermal expansion, expected number of cycles, end item tolerance, desired or required surface condition, method of cure, glass transition temperature of the material being molded, molding method, matrix, cost and a variety of other considerations. When the Temperature of a substance changes the energy that is stored in the Intermolecular bonds between atoms changes The glass transition temperature, T g is the temperature at which an Amorphous solid, such as Glass or a Polymer, becomes brittle
Mechanics of composite materials
The physical properties of composite materials are generally not isotropic (independent of direction of applied force) in nature, but rather are typically orthotropic (different depending on the direction of the applied force or load). Isotropy is uniformity in all directions Precise definitions depend on the subject area For instance, the stiffness of a composite panel will often depend upon the orientation of the applied forces and/or moments. Panel stiffness is also dependent on the design of the panel. For instance, the fiber reinforcement and matrix used, the method of panel build, thermoset versus thermoplastic, type of weave, and orientation of fiber axis to the primary force.
In contrast, isotropic materials (for example, aluminium or steel), in standard wrought forms, typically have the same stiffness regardless of the directional orientation of the applied forces and/or moments.
The relationship between forces/moments and strains/curvatures for an isotropic material can be described with the following material properties: Young's Modulus, the Shear Modulus and the Poisson's ratio, in relatively simple mathematical relationships. In Solid mechanics, Young's modulus (E is a measure of the Stiffness of an isotropic elastic material In Materials science, shear modulus or modulus of rigidity, denoted by G, or sometimes S or μ, is defined as the ratio of Shear Poisson's ratio ( ν) named after Simeon Poisson, is the ratio of the relative contraction strain, or transverse strain (normal to For the anisotropic material, it requires the mathematics of a second order tensor and up to 21 material property constants. For the special case of orthogonal isotropy, there are three different material property constants for each of Young's Modulus, Shear Modulus and Poisson's ratio--a total of 9 constants to describe the relationship between forces/moments and strains/curvatures.
Categories of fiber reinforced composite materials
Fiber reinforced composite materials can be divided into two main categories normally referred to as short fiber reinforced materials and continuous fiber reinforced materials. Continuous reinforced materials will often constitute a layered or laminated structure. The woven and continuous fiber styles are typically available in a variety of forms, being pre-impregnated with the given matrix (resin), dry, uni-directional tapes of various widths, plain weave, harness satins, braided, and stitched.
The short and long fibers are typically employed in compression molding and sheet molding operations. These come in the form of flakes, chips, and random mate (which can also be made from a continuous fiber laid in random fashion until the desired thickness of the ply / laminate is achieved).
Failure of composites
Shock, impact, or repeated cyclic stresses can cause the laminate to separate at the interface between two layers, a condition known as delamination. This article is about structural materials For delamination in embryology see Embryogenesis. Individual fibers can separate from the matrix e. g. fiber pull-out.
Composites can fail on the microscopic or macroscopic scale. Microscopic is a term used to describe objects smaller than those that can easily be seen by the naked Eye and which require a lens or Microscope to see Macroscopic is commonly used to describe physical objects that are measurable and observable by the Naked eye. Compression failures can occur at both the macro scale or at each individual reinforcing fiber in compression buckling. Tension failures can be net section failures of the part or degradation of the composite at a microscopic scale where one or more of the layers in the composite fail in tension of the matrix or failure the bond between the matrix and fibers.
Some composites are brittle and have little reserve strength beyond the initial onset of failure while others may have large deformations and have reserve energy absorbing capacity past the onset of damage. The variations in fibers and matrices that are available and the mixtures that can be made with blends leave a very broad range of properties that can be designed into a composite structure. The best known failure occurred when the carbon-fiber wing of the Space Shuttle Columbia fractured when impacted during take-off. Space Shuttle Columbia ( NASA Orbiter Vehicle Designation: OV-102) was the first spaceworthy Space shuttle in NASA 's It led to catastrophic break-up of the vehicle when it re-entered the earth's atmosphere on February 1, 2003.
Examples of composite materials
Fiber reinforced polymers or FRPs include wood (comprising cellulose fibers in a lignin and hemicellulose matrix), carbon-fiber reinforced plastic or CFRP, and glass reinforced plastic or GRP. A fibre-reinforced plastic ( FRP) (also fibre-reinforced polymer) is a Composite material comprising a Polymer matrix reinforced with fibres Wood is hard fibrous lignified structural tissue produced as secondary Xylem in the stems of Woody plants notably trees but also shrubs Cellulose is an Organic compound with the formula, a Polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4 Lignin or lignen is a complex Chemical compound most commonly derived from Wood and an integral part of the secondary Cell walls of Plants A hemicellulose can be any of several Heteropolymers (matrix polysaccharides present in almost all plant cell walls along with Cellulose. Carbon fiber reinforced plastic ( CFRP or CRP) is a very strong light and expensive Composite material or fiber reinforced plastic. Glass-reinforced plastic ( GRP) is a Composite material or Fiber-reinforced plastic made of a Plastic reinforced by fine fibers If classified by matrix then there are thermoplastic composites, short fiber thermoplastics, long fiber thermoplastics or long fiber reinforced thermoplastics. A thermoplastic is a Plastic that Melts to a liquid when heated and freezes to a Brittle, very Glassy state when cooled sufficiently Long fiber reinforced thermoplastics (LFRT are one of the fastest growing materials in the Polymer composites industry There are numerous thermoset composites, but advanced systems usually incorporate aramid fibre and carbon fibre in an epoxy resin matrix. Thermosetting plastics thermosets are Polymer materials that irreversibly cure form Aramid fibers are a class of heat-resistant and strong Synthetic fibers They are used in aerospace and military applications for ballistic rated body armor In Chemistry, epoxy or polyepoxide is a Thermosetting Epoxide Polymer that cures (polymerizes and crosslinks when mixed with a
Composites can also use metal fibres reinforcing other metals, as in metal matrix composites or MMC. A metal matrix composite (MMC is Composite material with at least two constituent parts one being a Metal. Magnesium is often used in MMCs because it has similar mechanical properties as epoxy. The benefit of magnesium is that it does not degrade in outer space. Ceramic matrix composites include bone (hydroxyapatite reinforced with collagen fibers), Cermet (ceramic and metal) and concrete. Bones are rigid organs that form part of the Endoskeleton of Vertebrates They function to move support and protect the various organs of the body produce Hydroxylapatite, also called hydroxyapatite, is a Mineral. It is a naturally occurring form of calcium Apatite with the formula Ca5(PO43(OH Collagen is the main Protein of Connective tissue in Animals and the most abundant protein in Mammals making up about 50% of the whole-body protein A cermet is a Composite material composed of Ceramic (cer and Metallic (met materials Concrete is a construction material composed of Cement (commonly Portland cement) as well as other cementitious materials such as Fly ash and Slag Ceramic matrix composites are built primarily for toughness, not for strength. Organic matrix/ceramic aggregate composites include asphalt concrete, mastic asphalt, mastic roller hybrid, dental composite, syntactic foam and mother of pearl. Asphalt ( is a sticky black and highly viscous liquid or semi-solid that is present in most crude Petroleums and in some natural deposits sometimes termed asphaltum Asphalt ( is a sticky black and highly viscous liquid or semi-solid that is present in most crude Petroleums and in some natural deposits sometimes termed asphaltum Dental composites, also called white fillings, are a group of restorative materials used in dentistry Syntactic foams are Composite materials synthesized by filling a Metal, Polymer or Ceramic matrix with hollow particles called Microballoons Nacre, also known as mother of pearl, is an organic-inorganic Composite material produced by some Mollusks as an inner shell layer Chobham armour is a special composite used in military applications. Chobham armour is the name informally given to a Composite armour developed in the 1960s at the British Tank research centre on Chobham Common
Additionally, thermoplastic composite materials can be formulated with specific metal powders resulting in materials with a density range from 2 g/cc to 11 g/cc (same density as lead). These materials can be used in place of traditional materials such as aluminum, stainless steel, brass, bronze, copper, lead, and even tungsten in weighting, balancing, vibration dampening, and radiation shielding applications. High density composites are an economically viable option when certain materials are deemed hazardous and are banned (such as lead) or when secondary operations costs (such as machining, finishing, or coating) are a factor.
Engineered wood includes a wide variety of different products such as plywood, oriented strand board, wood plastic composite (recycled wood fiber in polyethylene matrix), Pykrete (sawdust in ice matrix), Plastic-impregnated or laminated paper or textiles, Arborite, Formica (plastic) and Micarta. Engineered wood, also called composite wood, "man made wood" or "manufactured wood" includes a range of derivative Wood products which are Plywood is a type of Engineered board made from thin sheets of Wood, called plies or veneers Oriented strand board, or OSB, or waferboard or Sterling board (UK is an Engineered wood product formed by layering strands (flakes of Wood-plastic composite (commonly abbreviated as WPC) is a non-recyclable Composite material Lumber or Timber made of recycled plastic Pykrete is a Composite material made of approximately 45 percent Sawdust or some other form of Wood pulp (such as paper and 55 percent Ice by Arborite is a brand of Composite material manufactured by the Arborite Company, founded in Canada in 1948 after the initial development of the Formica is a brand of Composite materials manufactured by the Formica Corporation based in Cincinnati, Ohio, United States. Micarta is a composite of Linen or paper fabric in a Thermosetting plastic, originally used in electrical and decorative applications Other engineered laminate composites, such as Mallite, use a central core of end grain balsa wood, bonded to surface skins of light alloy or GRP. Mallite is a type of Laminate Composite material, formerly manufactured by the William Mallinson & Sons company These generate low-weight, high rigidity materials.
Typical products
Composite materials have gained popularity (despite their generally high cost) in high-performance products that need to be lightweight, yet strong enough to take harsh loading conditions such as aerospace components (tails, wings, fuselages, propellers), boat and scull hulls, bicycle frames and racing car bodies. This article is about the field of research and industry for the corporation see The Aerospace Corporation Aerospace comprises the Empennage émpənij is an Aviation term used to describe the Tail portion of an Aircraft. WING "ESPN 1410" is a commercial AM radio station in Dayton Ohio operating with 5000 watts at 1410 kHz with studios offices and transmitter located on David The fuselage (from the French fuselé "spindle-shaped" is an Aircraft 's main body section that holds crew and passengers or Cargo A propeller is essentially a type of fan which transmits power by converting Rotational motion into Thrust for propulsion of a vehicle such as an Scull redirects here The head bone is spelled " Skull " The bicycle, cycle, or bike is a pedal-driven, human-powered vehicle with two wheels attached to a frame, one behind Auto racing (also known as automobile racing, motor racing or car racing) is a Motorsport involving Racing Cars It Other uses include fishing rods and storage tanks. A fishing rod or a fishing pole is a Tool used to catch fish, usually in conjunction with the Sport of Angling, can also be used in A storage tank is a container usually for holding liquids sometimes for compressed gases (gas tank The new Boeing 787 Dreamliner structure including the wings and fuselage is composed of over 50 percent composites. The Boeing Company is a major Aerospace and defense corporation originally founded by William E WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout
Carbon composite is a key material in today's launch vehicles and spacecrafts. It is widely used in solar panel substrates, antenna reflectors and yokes of spacecrafts. It is also used in payload adapters, inter-stage structures and heat shields of launch vehicles.
See also
- Alloy
- Fibre
- Polymer
- Thermoplastic
- Thermoset
- Reinforced concrete
- Fiber reinforced concrete
- Short Fiber Reinforced Blends
- Aluminium composite panel
- American Composites Manufacturers Association
References
Further reading
- Autar K. An alloy is a Solid solution or Homogeneous mixture of two or more elements, at least one of which is a Metal, which itself has Fiber or fibre is a class of Materials that are continuous filaments or are in discrete elongated pieces similar to lengths of thread. A polymer is a large Molecule ( Macromolecule) composed of repeating Structural units typically connected by Covalent Chemical bonds A thermoplastic is a Plastic that Melts to a liquid when heated and freezes to a Brittle, very Glassy state when cooled sufficiently Thermosetting plastics thermosets are Polymer materials that irreversibly cure form Reinforced concrete is Concrete in which reinforcement bars (" Rebars quot or fibers have been incorporated to strengthen a material that would otherwise be Fiber reinforced concrete (FRC is Concrete containing fibrous material which increases its structural integrity Short Fiber Reinforced Blends are partial case of ternary composites i Aluminium Composite Panel (ACP is a widely-used term describing flat panels that consist of a non-aluminium core bonded between two Aluminium sheets The American Composites Manufacturers Association (ACMA is the world's largest Trade association serving the composites industry Kaw (2005). Mechanics of Composite Materials, 2nd edition, CRC. ISBN 0-84-931343-0.
- Handbook of Polymer Composites for Engineers By Leonard Hollaway Published 1994
Woodhead Publishing
External links
- Composite material key concepts
- Distance learning course in polymers and composites
- Composite Sandwich Structure of Minardi F1 Car
- Teaching support materials for the University of Plymouth composites degree
- Platform for integrated simulation of composite real-life behaviour
Dictionary
composite material
-noun
- Any engineered material composed of two radically different materials in a tightly bonded matrix and having properties significantly different from either constituent
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