materials science Materials science is an interdisciplinary field of researching and discovering materials. Materials engineering is an engineering field of finding uses for materials in other fields and industries. The intellectual origins of materials sci ...

, advanced composite materials (ACMs) are

materials A material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their ge ...

that are generally characterized by unusually high-strength fibres with unusually high

stiffness Stiffness is the extent to which an object resists deformation in response to an applied force. The complementary concept is flexibility or pliability: the more flexible an object is, the less stiff it is. Calculations The stiffness, k, of a ...

, or modulus of elasticity characteristics, compared to other materials, while bound together by weaker

matrices Matrix (: matrices or matrixes) or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the ...

. These are termed "advanced composite materials" in comparison to the

composite material A composite or composite material (also composition material) is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a ...

s commonly in use such as

reinforced concrete Reinforced concrete, also called ferroconcrete or ferro-concrete, is a composite material in which concrete's relatively low tensile strength and ductility are compensated for by the inclusion of reinforcement having higher tensile strength or ...

, or even

concrete Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...

itself. The high-strength fibers are also low

density Density (volumetric mass density or specific mass) is the ratio of a substance's mass to its volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' (or ''d'') can also be u ...

while occupying a large fraction of the

volume Volume is a measure of regions in three-dimensional space. It is often quantified numerically using SI derived units (such as the cubic metre and litre) or by various imperial or US customary units (such as the gallon, quart, cubic inch) ...

. Advanced composites exhibit desirable physical and

chemical properties A chemical property is any of a material property, material's properties that becomes evident during, or after, a chemical reaction; that is, any attribute that can be established only by changing a substance's chemical substance, chemical identit ...

that include light weight coupled with high stiffness ( elasticity), and strength along the direction of the reinforcing fiber, dimensional stability, temperature and chemical resistance, flex performance, and relatively easy processing. Advanced composites are replacing metal components in many uses, particularly in the

aerospace industry Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial, and military applications. Aerospace engineering consists of aeronautics and astr ...

. Composites are classified according to their matrix phases. These classifications are polymer matrix composites (PMCs), ceramic matrix composites (CMCs), and

metal matrix composite In materials science, a metal matrix composite (MMC) is a composite material with fibers or particles dispersed in a metallic matrix, such as copper, aluminum, or steel. The secondary phase is typically a ceramic (such as alumina or silicon carb ...

s (MMCs). Also, materials within these categories are often called "advanced" if they combine the properties of high (axial, longitudinal) strength values and high ( axial, longitudinal) stiffness values, with low weight, corrosion resistance, and in some cases special

electrical Electricity is the set of physical phenomena associated with the presence and motion of matter possessing an electric charge. Electricity is related to magnetism, both being part of the phenomenon of electromagnetism, as described by Maxwel ...

properties. Advanced composite materials have broad, proven applications, in the

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

, aerospace, and sports-equipment sectors. Even more specifically, ACMs are very attractive for aircraft and aerospace structural parts. ACMs have been developed for NASA's Advanced Space Transportation Program, armor protection for Army aviation and the

Federal Aviation Administration The Federal Aviation Administration (FAA) is a Federal government of the United States, U.S. federal government agency within the United States Department of Transportation, U.S. Department of Transportation that regulates civil aviation in t ...

of the USA, and high-temperature shafting for the Comanche helicopter. Additionally, ACMs have a decades-long history in military and government aerospace industries. However, much of the technology is new and not presented formally in secondary or

undergraduate education Undergraduate education is education conducted after secondary education and before postgraduate education, usually in a college or university. It typically includes all postsecondary programs up to the level of a bachelor's degree. For example, ...

, and the technology of advanced composites manufacture is continually evolving. Public domain content from a U.S. government department
Materials created by the federal government
are generally part of the public domain and may be used, reproduced and distributed without permission.

Overview and historical perspective

Manufacturing ACMs is a multibillion-dollar industry worldwide. Composite products range from

skateboard A skateboard is a type of sports equipment used for skateboarding. It is usually made of a specially designed 7–8-ply maple plywood deck and has polyurethane wheels attached to the underside by a pair of skateboarding trucks. The skateboard ...

s to components of the

Space Shuttle The Space Shuttle is a retired, partially reusable launch system, reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. ...

. The industry can be generally divided into two basic segments: industrial composites and advanced composites. Several of the composites-manufacturing processes are common to both segments. The two basic segments are described below.

Industrial composites

The industrial-composites industry has been in place for over 40 years in the U.S. This large industry uses various

resin A resin is a solid or highly viscous liquid that can be converted into a polymer. Resins may be biological or synthetic in origin, but are typically harvested from plants. Resins are mixtures of organic compounds, predominantly terpenes. Commo ...

systems including

polyester Polyester is a category of polymers that contain one or two ester linkages in every repeat unit of their main chain. As a specific material, it most commonly refers to a type called polyethylene terephthalate (PET). Polyesters include some natura ...

epoxy Epoxy is the family of basic components or Curing (chemistry), cured end products of epoxy Resin, resins. Epoxy resins, also known as polyepoxides, are a class of reactive prepolymers and polymers which contain epoxide groups. The epoxide fun ...

, and other specialty resins. These materials, along with a

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

or curing agent and some type of fiber reinforcement (typically glass fibers), are used in the production of a wide spectrum of industrial components and consumer goods: boats, piping, auto bodies, and other parts and components.

Advanced composites

The advanced-composites industry is characterized by the use of expensive, high-performance resin systems and high-strength, high-stiffness fiber reinforcement. The aerospace industry, including

military A military, also known collectively as armed forces, is a heavily armed, highly organized force primarily intended for warfare. Militaries are typically authorized and maintained by a sovereign state, with their members identifiable by a d ...

and commercial aircraft of all types, is the major customer for advanced composites. These materials have also been adopted for use by the sporting-goods suppliers who sell high-performance equipment to the

golf Golf is a club-and-ball sport in which players use various Golf club, clubs to hit a Golf ball, ball into a series of holes on a golf course, course in as few strokes as possible. Golf, unlike most ball games, cannot and does not use a standa ...

tennis Tennis is a List of racket sports, racket sport that is played either individually against a single opponent (singles (tennis), singles) or between two teams of two players each (doubles (tennis), doubles). Each player uses a tennis racket st ...

fishing Fishing is the activity of trying to catch fish. Fish are often caught as wildlife from the natural environment (Freshwater ecosystem, freshwater or Marine ecosystem, marine), but may also be caught from Fish stocking, stocked Body of water, ...

, and

archery Archery is the sport, practice, or skill of using a Bow and arrow, bow to shooting, shoot arrows.Paterson ''Encyclopaedia of Archery'' p. 17 The word comes from the Latin ''arcus'', meaning bow. Historically, archery has been used for hunting ...

markets; as well as in the swimming pool industry with composite wall structures. While aerospace is the predominant market for advanced composites today, the industrial and automotive markets will increasingly see the use of advanced composites toward the year 2000. At present, both manual and automated processes are employed in making advanced-composite parts. As automated processes become more predominant, the costs of advanced composites are expected to decline to the point at which these materials will be used widely in electronic, machinery, and surface-transportation equipment. Suppliers of advanced composite materials tend to be larger companies capable of doing the

research and development Research and development (R&D or R+D), known in some countries as OKB, experiment and design, is the set of innovative activities undertaken by corporations or governments in developing new services or products. R&D constitutes the first stage ...

necessary to provide the high-performance resin systems used in this segment of the industry. End-users also tend to be large, and many are in the aerospace businesses.

Limitations

Despite their strength and low weight, composites have not been a miracle solution for aircraft structures. Composites are typically difficult to inspect for flaws. Some of them absorb moisture. Most importantly, they can be prohibitively expensive, primarily because they are labor-intensive and often require complex and expensive fabrication machines. Aluminium, by contrast, is easy and inexpensive to manufacture and repair; for example, in a minor collision, an aluminium component can often be hammered back into its original shape, whereas a crunched fiberglass component will likely have to be completely replaced. Public domain content (see above reference) Aluminium has a relatively high fracture toughness, allowing it to undergo large amounts of plastic deformation before failure. Composites, on the other hand, are less damage-tolerant and undergo much less plastic deformation before failure. An airplane made entirely from aluminium can be repaired almost anywhere. This is not the case for composite materials, particularly as they use different and more exotic materials. Because of this, composites will probably always be used more in military aircraft, which are constantly being maintained, than in commercial aircraft, which have to require less maintenance. Aluminium still remains a remarkably useful material for aircraft structures, and metallurgists have worked hard to develop better aluminium alloys, such as aluminium-lithium alloys.

External links

*Buckland, Peter G
Advanced composite materials with application to bridges
September 30, 1991. *Oak Ridge National Laboratory

Vol. 33, No. 3, 2000. *Worldwide Composites Search Engin

Large database of companies involved in composite materials.

References