View source for Chemistry:Carbon fiber reinforced polymer

{{short description|Light, strong, and rigid composite material}}
[[File:Cfk heli slw.jpg|thumb|upright=0.5|Tail of a radio-controlled helicopter, made of CFRP]]

'''Carbon fiber reinforced polymer''' (American English), '''Carbon fibre reinforced polymer''' (Commonwealth English), or '''carbon fiber reinforced plastic''', or '''carbon fiber reinforced thermoplastic''' ('''CFRP''', '''CRP''', '''CFRTP''', or often simply '''carbon fiber''', '''carbon composite''', or even '''carbon'''), is an extremely strong and light fiber-reinforced plastic which contains [[Chemistry:Carbon fibers|carbon fibers]]. The spelling 'fibre' is typically used outside the US. CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and [[Physics:Stiffness|stiffness]] (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, [[Engineering:Sports equipment|sports equipment]], and an increasing number of consumer and technical applications.<ref name="tool wear"/>

The binding [[Chemistry:Polymer|polymer]] is often a [[Chemistry:Thermosetting polymer|thermoset]] resin such as [[Chemistry:Epoxy|epoxy]], but other thermoset or [[Chemistry:Thermoplastic|thermoplastic]] polymers, such as [[Chemistry:Polyester|polyester]], [[Chemistry:Vinyl ester resin|vinyl ester]], or [[Chemistry:Nylon|nylon]], are sometimes used. The [[Chemistry:Composite material|composite material]] may contain [[Chemistry:Aramid|aramid]] (e.g. [[Chemistry:Kevlar|Kevlar]], [[Chemistry:Twaron|Twaron]]), [[Chemistry:Ultra-high-molecular-weight polyethylene|ultra-high-molecular-weight polyethylene]] (UHMWPE), [[Chemistry:Aluminium|aluminium]], or [[Chemistry:Glass fiber|glass fiber]]s in addition to carbon fibers. The properties of the final CFRP product can also be affected by the type of additives introduced to the binding matrix (resin). The most common additive is [[Chemistry:Silica gel|silica]], but other additives such as rubber and [[Physics:Carbon nanotube|carbon nanotube]]s can be used. The material is also referred to as ''graphite-reinforced polymer'' or ''graphite fiber-reinforced polymer'' (''GFRP'' is less common, as it clashes with glass-(fiber)-reinforced polymer).

==Properties==
CFRP are [[Chemistry:Composite material|composite material]]s. In this case the composite consists of two parts: a matrix and a reinforcement. In CFRP the reinforcement is carbon fiber, which provides the strength. The matrix is usually a polymer resin, such as epoxy, to bind the reinforcements together.<ref>{{cite web |first=Dmitri |last=Kopeliovich |url=http://www.substech.com/dokuwiki/doku.php?id=carbon_fiber_reinforced_polymer_composites |title=Carbon Fiber Reinforced Polymer Composites |url-status=live |archive-url=https://web.archive.org/web/20120514092827/http://www.substech.com/dokuwiki/doku.php?id=carbon_fiber_reinforced_polymer_composites |archive-date=14 May 2012}}. substech.com</ref> Because CFRP consists of two distinct elements, the material properties depend on these two elements.

Reinforcement gives CFRP its strength and rigidity, measured by [[Physics:Stress (mechanics)|stress]] and [[Physics:Elastic modulus|elastic modulus]] respectively. Unlike [[Isotropy|isotropic]] materials like steel and aluminum, CFRP has directional strength properties. The properties of CFRP depend on the layouts of the carbon fiber and the proportion of the carbon fibers relative to the polymer.<ref>{{cite web |title=Basic Properties of Reference Crossply Carbon-Fiber Composite, ORNL/TM-2000/29, Pub57518 |first1=J. M. |last1=Corum |first2=R. L. |last2=Battiste |first3=K. C |last3=Liu |first4=M. B. |last4=Ruggles |date=February 2000 |publisher=Oak Ridge National Laboratory |url=https://info.ornl.gov/sites/publications/Files/Pub57518.pdf |url-status=live |archive-url=https://web.archive.org/web/20161227203159/http://info.ornl.gov/sites/publications/Files/Pub57518.pdf |archive-date=27 December 2016}}</ref> The two different equations governing the net elastic modulus of composite materials using the properties of the carbon fibers and the polymer matrix can also be applied to carbon fiber reinforced plastics.<ref name=":0">{{cite book|title= Mechanical Behavior of Materials|last= Courtney|first= Thomas|publisher= Waveland Press, Inc.|year= 2000|isbn= 1-57766-425-6|location= United States of America|pages= 247–249}}</ref> The following equation,
:<math>E_c = V_mE_m + V_fE_f</math>

is valid for composite materials with the fibers oriented in the direction of the applied load. <math>E_c</math> is the total composite modulus, <math>V_m</math> and <math>V_f</math> are the volume fractions of the matrix and fiber respectively in the composite, and <math>E_m</math> and <math>E_f</math> are the elastic moduli of the matrix and fibers respectively.<ref name=":0"/> The other extreme case of the elastic modulus of the composite with the fibers oriented transverse to the applied load can be found using the following equation:<ref name=":0"/>
:<math>E_c = \left( \frac{V_m}{E_m} + \frac{V_f}{E_f} \right)^{-1}</math>

The fracture toughness of carbon fiber reinforced plastics is governed by the following mechanisms: 1) debonding between the carbon fiber and polymer matrix, 2) fiber pull-out, and 3) delamination between the CFRP sheets.<ref name=":1">{{cite book |title=Composite Materials |last=Chawla |first=Krishan |publisher=Springer |year=2013 |isbn=978-0-387-74364-6 |location=United States of America |pages=}}</ref> Typical epoxy-based CFRPs exhibit virtually no plasticity, with less than 0.5% strain to failure. Although CFRPs with epoxy have high strength and elastic modulus, the brittle fracture mechanics present unique challenges to engineers in failure detection since failure occurs catastrophically.<ref name=":1"/> As such, recent efforts to toughen CFRPs include modifying the existing epoxy material and finding alternative polymer matrix. One such material with high promise is [[Chemistry:Polyether ether ketone|PEEK]], which exhibits an order of magnitude greater toughness with similar elastic modulus and tensile strength.<ref name=":1"/> However, PEEK is much more difficult to process and more expensive.<ref name=":1"/>

Despite its high initial strength-to-weight ratio, a design limitation of CFRP is its lack of a definable [[Physics:Fatigue limit|fatigue limit]]. This means, theoretically, that stress cycle failure cannot be ruled out. While steel and many other structural metals and alloys do have estimable fatigue or endurance limits, the complex failure modes of composites mean that the fatigue failure properties of CFRP are difficult to predict and design against. As a result, when using CFRP for critical cyclic-loading applications, engineers may need to design in considerable strength safety margins to provide suitable component reliability over its service life.

Environmental effects such as temperature and humidity can have profound effects on the polymer-based composites, including most CFRPs. While CFRPs demonstrate excellent corrosion resistance, the effect of moisture at wide ranges of temperatures can lead to degradation of the mechanical properties of CFRPs, particularly at the matrix-fiber interface.<ref>{{cite journal|title= Temperature effect during humid ageing on interfaces of glass and carbon fibers reinforced epoxy composites|journal= Journal of Colloid and Interface Science|date= 1 June 2006|pages= 111–117|volume= 298|issue= 1|doi= 10.1016/j.jcis.2005.12.023|pmid= 16386268|first= B. C.|last= Ray|bibcode= 2006JCIS..298..111R}}</ref> While the carbon fibers themselves are not affected by the moisture diffusing into the material, the moisture plasticizes the polymer matrix.<ref name=":1"/> This led to significant changes in properties that are dominantly influenced by the matrix in CFRPs such as compressive, interlaminar shear, and impact properties.<ref>{{Cite journal|last=Almudaihesh|first=Faisel|last2=Holford|first2=Karen|last3=Pullin|first3=Rhys|last4=Eaton|first4=Mark|date=2020-02-01|title=The influence of water absorption on unidirectional and 2D woven CFRP composites and their mechanical performance|url=http://www.sciencedirect.com/science/article/pii/S1359836819346918|journal=Composites Part B: Engineering|language=en|volume=182|pages=107626|doi=10.1016/j.compositesb.2019.107626|issn=1359-8368}}</ref> The epoxy matrix used for engine fan blades is designed to be impervious against jet fuel, lubrication, and rain water, and external paint on the composites parts is applied to minimize damage from ultraviolet light.<ref name=":1"/><ref>{{cite journal|title= Multi-factorial models of a carbon fibre/epoxy composite subjected to accelerated environmental ageing|journal= Composite Structures|date= May 2014|pages= 179–192|volume= 111|doi= 10.1016/j.compstruct.2013.12.028|first1= Enrique|last1= Guzman|first2= Joël|last2= Cugnoni|first3= Thomas|last3= Gmür}}</ref>

The carbon fibers can cause [[Chemistry:Galvanic corrosion|galvanic corrosion]] when CRP parts are attached to aluminum.<ref>{{cite news |url=https://www.stltoday.com/business/local/boeing-looks-at-pricey-titanium-in-bid-to-stem-losses/article_d7e80ffe-dd41-5c67-8f86-8b8d9ae43e34.html |title=Boeing looks at pricey titanium in bid to stem 787 losses |last1=Scott |first1=Alwyn |date=25 July 2015 |website=www.stltoday.com |publisher=Reuters |access-date=25 July 2015 |url-status=live |archive-url=https://web.archive.org/web/20171117145531/http://www.stltoday.com/business/local/boeing-looks-at-pricey-titanium-in-bid-to-stem-losses/article_d7e80ffe-dd41-5c67-8f86-8b8d9ae43e34.html |archive-date=17 November 2017}}</ref>

Carbon Fiber Reinforced Plastics are very hard to machine, and causes significant tool wear. The tool wear in CFRP machining is dependent on the fiber orientation and machining condition of the cutting process. In order to reduce tool wear various types of coated tools are used in machining CFRP and CFRP-metal stack.<ref name="tool wear">{{cite journal |first1=Dinh |last1=Nguyen |first2=Mohammad Sayem Bin |last2=Abdullah |first3=Ryan |last3=Khawarizmi |first4=Dave |last4=Kim |first5=Patrick |last5=Kwon |title=The effect of fiber orientation on tool wear in edge-trimming of carbon fiber reinforced plastics (CFRP) laminates |journal=  Wear|volume=450–451 |year=2020 |issn=0043-1648 |publisher=Elsevier B.V |pages=203213 |doi=10.1016/j.wear.2020.203213}}</ref>

==Manufacture==
[[File:Steinbichler Shearography Honeycomb with CFRP Top Layer Artificial failures that simulate layer- core delaminations Material Top view.jpg|thumbnail|right|Carbon fiber reinforced polymer]]

The primary element of CFRP is a [[Chemistry:Carbon fibers#Synthesis|carbon filament]]; this is produced from a precursor [[Chemistry:Polymer|polymer]] such as [[Chemistry:Polyacrylonitrile|polyacrylonitrile]] (PAN), [[Chemistry:Rayon|rayon]], or petroleum [[Chemistry:Pitch (resin)|pitch]]. For synthetic polymers such as PAN or rayon, the precursor is first [[Engineering:Spinning (polymers)|spun]] into filament yarns, using chemical and mechanical processes to initially align the polymer chains in a way to enhance the final physical properties of the completed carbon fiber. Precursor compositions and mechanical processes used during spinning filament yarns may vary among manufacturers. After drawing or spinning, the polymer filament yarns are then heated to drive off non-carbon atoms ([[Chemistry:Carbonization|carbonization]]), producing the final carbon fiber. The carbon fibers filament yarns may be further treated to improve handling qualities, then wound on to bobbins.<ref>{{cite web |url=http://zoltek.com/carbon-fiber/how-is-carbon-fiber-made/ |title=How is it Made |publisher=Zoltek |access-date=26 March 2015 |url-status=live |archive-url=https://web.archive.org/web/20150319182214/http://www.zoltek.com/carbonfiber/how-is-it-made/ |archive-date=19 March 2015}}</ref> From these fibers, a unidirectional sheet is created. These sheets are layered onto each other in a quasi-isotropic layup, e.g. 0°, +60°, or −60° relative to each other.

From the elementary fiber, a bidirectional woven sheet can be created, i.e. a twill with a 2/2 weave. The process by which most CFRPs are made varies, depending on the piece being created, the finish (outside gloss) required, and how many of the piece will be produced. In addition, the choice of matrix can have a profound effect on the properties of the finished composite.

Many CFRP parts are created with a single layer of carbon fabric that is backed with fiberglass. A tool called a chopper gun is used to quickly create these composite parts. Once a thin shell is created out of carbon fiber, the chopper gun cuts rolls of fiberglass into short lengths and sprays resin at the same time, so that the fiberglass and resin are mixed on the spot. The resin is either external mix, wherein the hardener and resin are sprayed separately, or internal mixed, which requires cleaning after every use.
Manufacturing methods may include the following:

===Molding===
One method of producing CFRP parts is by layering sheets of carbon fiber cloth into a [[Engineering:Molding (process)|mold]] in the shape of the final product. The alignment and weave of the cloth fibers is chosen to optimize the strength and stiffness properties of the resulting material. The mold is then filled with [[Chemistry:Epoxy|epoxy]] and is heated or air-cured. The resulting part is very corrosion-resistant, stiff, and strong for its weight. Parts used in less critical areas are manufactured by draping cloth over a mold, with epoxy either preimpregnated into the fibers (also known as ''[[Chemistry:Pre-preg|pre-preg]]'') or "painted" over it. High-performance parts using single molds are often vacuum-bagged and/or [[Engineering:Autoclave (industrial)|autoclave]]-cured, because even small air bubbles in the material will reduce strength. An alternative to the autoclave method is to use internal pressure via inflatable air bladders or [[Chemistry:Polystyrene|EPS foam]] inside the non-cured laid-up carbon fiber.

===Vacuum bagging===
For simple pieces of which relatively few copies are needed (1–2 per day), a vacuum bag can be used. A fiberglass, carbon fiber, or aluminum mold is polished and waxed, and has a [[Chemistry:Release agent|release agent]] applied before the fabric and resin are applied, and the vacuum is pulled and set aside to allow the piece to cure (harden). There are three ways to apply the resin to the fabric in a vacuum mold.

The first method is manual and called a wet layup, where the two-part resin is mixed and applied before being laid in the mold and placed in the bag. The other one is done by infusion, where the dry fabric and mold are placed inside the bag while the vacuum pulls the resin through a small tube into the bag, then through a tube with holes or something similar to evenly spread the resin throughout the fabric. Wire loom works perfectly for a tube that requires holes inside the bag. Both of these methods of applying resin require hand work to spread the resin evenly for a glossy finish with very small pin-holes.

A third method of constructing composite materials is known as a dry layup. Here, the carbon fiber material is already impregnated with resin (pre-preg) and is applied to the mold in a similar fashion to adhesive film. The assembly is then placed in a vacuum to cure. The dry layup method has the least amount of resin waste and can achieve lighter constructions than wet layup. Also, because larger amounts of resin are more difficult to bleed out with wet layup methods, pre-preg parts generally have fewer pinholes. Pinhole elimination with minimal resin amounts generally require the use of [[Engineering:Autoclave (industrial)|autoclave]] pressures to purge the residual gases out.

===Compression molding===
A quicker method uses a [[Engineering:Compression molding|compression mold]]. This is a two-piece (male and female) mold usually made out of aluminum or steel that is pressed together with the fabric and resin between the two. The benefit is the speed of the entire process. Some car manufacturers, such as BMW, claimed to be able to cycle a new part every 80 seconds. However, this technique has a very high initial cost since the molds require CNC machining of very high precision.

===Filament winding===
For difficult or convoluted shapes, a filament winder can be used to make CFRP parts by winding filaments around a mandrel or a core.

==Applications==
Applications for CFRP include the following:

===Aerospace engineering===
[[File:F-WWCF A350 LBG SIAE 2015 (18953559366).jpg|thumb|right|A composite [[Engineering:Airbus A350|Airbus A350]] with carbon fiber themed livery]]

The [[Engineering:Airbus A350 XWB|Airbus A350 XWB]] is built of 52% CFRP<ref name="presentation">{{cite web |url=http://www.eads.com/xml/content/OF00000000400004/7/19/41508197.pdf |title=Taking the lead: A350XWB presentation |publisher=EADS |date=December 2006 |url-status=unfit |archive-url=https://web.archive.org/web/20090327094646/http://www.eads.com/xml/content/OF00000000400004/7/19/41508197.pdf |archive-date=27 March 2009}}</ref> including wing spars and fuselage components, overtaking the [[Engineering:Boeing 787 Dreamliner|Boeing 787 Dreamliner]], for the aircraft with the highest weight ratio for CFRP, which is 50%.<ref>{{cite web |url=http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_06/article_04_2.html |title=AERO – Boeing 787 from the Ground Up |publisher=Boeing |year=2006 |access-date=7 February 2015 |url-status=live |archive-url=https://web.archive.org/web/20150221075003/http://www.boeing.com/commercial/aeromagazine/articles/qtr_4_06/article_04_2.html |archive-date=21 February 2015}}</ref> This was one of the first commercial aircraft to have wing spars made from composites. The [[Engineering:Airbus A380|Airbus A380]] was one of the first commercial airliners to have a central wing-box made of CFRP; it is the first to have a smoothly contoured wing cross-section instead of the wings being partitioned span-wise into sections. This flowing, continuous cross section optimises aerodynamic efficiency.{{citation needed|date=April 2019}} Moreover, the trailing edge, along with the rear bulkhead, [[Engineering:Empennage|empennage]], and un-pressurised fuselage are made of CFRP.<ref>{{cite web |url=http://www.iccm-central.org/Proceedings/ICCM13proceedings/SITE/PAPERS/paper-1695.pdf |title=Composite Materials in the Airbus A380 – From History to Future |first=Jérôme |last=Pora |publisher=Airbus |year=2001 |access-date=7 February 2015 |url-status=live |archive-url=https://web.archive.org/web/20150206122639/http://www.iccm-central.org/Proceedings/ICCM13proceedings/SITE/PAPERS/paper-1695.pdf |archive-date=6 February 2015}}</ref> However, many delays have pushed order delivery dates back because of problems with the manufacture of these parts. Many aircraft that use CFRP have experienced delays with delivery dates due to the relatively new processes used to make CFRP components, whereas metallic structures have been studied and used on airframes for years, and the processes are relatively well understood. A recurrent problem is the monitoring of structural ageing, for which new methods are constantly investigated, due to the unusual multi-material and anisotropic nature of CFRP.<ref>{{cite document |url=https://infoscience.epfl.ch/record/206768/files/EPFL_TH6422.pdf |first1=Enrique |last1=Guzman |first2=Thomas (dir.) |last2=Gmür |title=A Novel Structural Health Monitoring Method for Full-Scale CFRP Structures |publisher=EPFL PhD thesis |year=2014 |doi=10.5075/epfl-thesis-6422 |url-status=live |archive-url=https://web.archive.org/web/20160625152917/https://infoscience.epfl.ch/record/206768/files/EPFL_TH6422.pdf |archive-date=2016-06-25}}</ref>

In 1968 a ''Hyfil'' carbon-fiber fan assembly was in service on the [[Engineering:Rolls-Royce Conway|Rolls-Royce Conway]]s of the [[Engineering:Vickers VC10|Vickers VC10]]s operated by BOAC.<ref>{{cite journal |url=https://www.flightglobal.com/pdfarchive/view/1968/1968%20-%202107.html?search=rolls-royce%20rb211%20hyfil |title=Engines |journal=Flight International |date=26 September 1968 |url-status=live |archive-url=https://web.archive.org/web/20140814123711/http://www.flightglobal.com/pdfarchive/view/1968/1968%20-%202107.html?search=rolls-royce%20rb211%20hyfil |archive-date=14 August 2014}}</ref>

Specialist aircraft designers and manufacturers [[Company:Scaled Composites|Scaled Composites]] have made extensive use of CFRP throughout their design range, including the first private manned spacecraft Spaceship One. CFRP is widely used in [[Engineering:Micro air vehicle|micro air vehicle]]s (MAVs) because of its high strength to weight ratio.

===Automotive engineering===
{{multiple image
|align= right
|direction= vertical
|image1= Rétromobile 2011 - Citroën SM Rallye du Maroc 1971 - 003.jpg
|width1= 175
|caption1= [[Engineering:Citroën SM|Citroën SM]] that won 1971 Rally of Morocco with carbon fiber wheels
|image2= McLaren F1 in Geneva, Switzerland.jpg
|width2= 175
|caption2= 1996 [[Engineering:McLaren F1|McLaren F1]] – first carbon fiber body shell
|image3= McLaren MP4.jpg
|width3= 175
|caption3= McLaren MP4 (MP4/1), first carbon fiber F1 car.
}}

CFRPs are extensively used in high-end automobile racing.<ref>{{cite web|title=Red Bull's How To Make An F1 Car Series Explains Carbon Fiber Use: Video|url=http://www.motorauthority.com/news/1087167_red-bulls-how-to-make-an-f1-car-series-explains-carbon-fiber-use-video|work=motorauthority|access-date=11 October 2013|url-status=live|archive-url=https://web.archive.org/web/20130929162005/http://www.motorauthority.com/news/1087167_red-bulls-how-to-make-an-f1-car-series-explains-carbon-fiber-use-video|archive-date=29 September 2013}}</ref> The high cost of carbon fiber is mitigated by the material's unsurpassed strength-to-weight ratio, and low weight is essential for high-performance automobile racing. Race-car manufacturers have also developed methods to give carbon fiber pieces strength in a certain direction, making it strong in a load-bearing direction, but weak in directions where little or no load would be placed on the member. Conversely, manufacturers developed omnidirectional carbon fiber weaves that apply strength in all directions. This type of carbon fiber assembly is most widely used in the "safety cell" [[Engineering:Monocoque|monocoque]] chassis assembly of high-performance race-cars. The first carbon fiber monocoque chassis was introduced in Formula One by McLaren in the 1981 season. It was designed by John Barnard and was widely copied in the following seasons by other F1 teams due to the extra rigidity provided to the chassis of the cars.<ref>{{cite book |first=Alan |last=Henry |title=McLaren: Formula 1 Racing Team |publisher=Haynes |year=1999 |ref=harv |isbn=1-85960-425-0 |url-access=registration |url=https://archive.org/details/mclarenformula1r0000henr }}</ref>

Many [[Engineering:Supercar|supercar]]s over the past few decades have incorporated CFRP extensively in their manufacture, using it for their monocoque chassis as well as other components.<ref>{{cite news |url=https://www.extremetech.com/extreme/162582-bmw-i3-will-bmws-new-ev-finally-be-the-breakthrough-for-carbon-fiber-cars |work=Extreme Tech |title=BMW i3: Cheap, mass-produced carbon fiber cars finally come of age |first=Bill |last=Howard |date=30 July 2013 |access-date=31 July 2015 |url-status=live |archive-url=https://web.archive.org/web/20150731091626/http://www.extremetech.com/extreme/162582-bmw-i3-will-bmws-new-ev-finally-be-the-breakthrough-for-carbon-fiber-cars |archive-date=31 July 2015}}</ref> As far back as 1971, the [[Engineering:Citroën SM|Citroën SM]] offered optional lightweight carbon fiber wheels.<ref>{{cite web |url=http://jalopnik.com/michelin-made-carbon-fiber-wheels-for-citroen-back-in-1-1543922374 |title=Michelin Made Carbon Fiber Wheels For Citroën Back In 1971 |first=Máté |last=Petrány |work=Jalopnik |date=17 March 2014 |access-date=31 July 2015 |url-status=live |archive-url=https://web.archive.org/web/20150518103133/http://jalopnik.com/michelin-made-carbon-fiber-wheels-for-citroen-back-in-1-1543922374 |archive-date=18 May 2015}}</ref><ref>{{cite web |url=http://www.hemmings.com/hmn/stories/2007/04/01/hmn_feature23.html |title=Reinventing the Wheel Leave it to Citroën to bring the world's first resin wheels to market |first=David |last=L:aChance |work=Hemmings |date=April 2007 |access-date=14 October 2015 |url-status=live |archive-url=https://web.archive.org/web/20150906005508/http://www.hemmings.com/hmn/stories/2007/04/01/hmn_feature23.html |archive-date=6 September 2015}}</ref>

Use of the material has been more readily adopted by low-volume manufacturers who used it primarily for creating body-panels for some of their high-end cars due to its increased strength and decreased weight compared with the glass-reinforced polymer they used for the majority of their products.

===Civil engineering===
CFRP has become a notable material in [[Engineering:Structural engineering|structural engineering]] applications. Studied in an academic context as to its potential benefits in construction, it has also proved itself cost-effective in a number of field applications strengthening concrete, masonry, steel, cast iron, and timber structures. Its use in industry can be either for retrofitting to strengthen an existing structure or as an alternative reinforcing (or pre-stressing) material instead of steel from the outset of a project.

[[Earth:Retrofitting|Retrofitting]] has become the increasingly dominant use of the material in civil engineering, and applications include increasing the load capacity of old structures (such as [[Engineering:Bridge|bridge]]s) that were designed to tolerate far lower service loads than they are experiencing today, seismic retrofitting, and repair of damaged structures. Retrofitting is popular in many instances as the cost of replacing the deficient structure can greatly exceed the cost of strengthening using CFRP.<ref>Ismail, N. [https://web.archive.org/web/20120425231749/http://www.najif.net/wp-content/uploads/2007/12/cfrp-paper.pdf "Strengthening of bridges using CFRP composites."] najif.net.</ref>

Applied to reinforced concrete structures for flexure, CFRP typically has a large impact on strength (doubling or more the strength of the section is not uncommon), but only a moderate increase in stiffness (perhaps a 10% increase). This is because the material used in this application is typically very strong (e.g., 3000 MPa ultimate [[Physics:Tensile strength|tensile strength]], more than 10 times mild steel) but not particularly stiff (150 to 250 GPa, a little less than steel, is typical). As a consequence, only small cross-sectional areas of the material are used. Small areas of very high strength but moderate stiffness material will significantly increase strength, but not stiffness.

CFRP can also be applied to enhance shear strength of reinforced concrete by wrapping fabrics or fibers around the section to be strengthened. Wrapping around sections (such as bridge or building columns) can also enhance the ductility of the section, greatly increasing the resistance to collapse under earthquake loading. Such 'seismic retrofit' is the major application in earthquake-prone areas, since it is much more economic than alternative methods.

If a column is circular (or nearly so) an increase in axial capacity is also achieved by wrapping. In this application, the confinement of the CFRP wrap enhances the compressive strength of the concrete. However, although large increases are achieved in the ultimate collapse load, the concrete will crack at only slightly enhanced load, meaning that this application is only occasionally used. Specialist ultra-high modulus CFRP (with tensile modulus of 420 GPa or more) is one of the few practical methods of strengthening cast-iron beams. In typical use, it is bonded to the tensile flange of the section, both increasing the stiffness of the section and lowering the [[Physics:Neutral axis|neutral axis]], thus greatly reducing the maximum tensile stress in the cast iron.

In the United States, pre-stressed concrete cylinder pipes (PCCP) account for a vast majority of water transmission mains. Due to their large diameters, failures of PCCP are usually catastrophic and affect large populations. Approximately {{convert|19000|mi}} of PCCP have been installed between 1940 and 2006. Corrosion in the form of hydrogen embrittlement has been blamed for the gradual deterioration of the pre-stressing wires in many PCCP lines. Over the past decade, CFRPs have been utilized to internally line PCCP, resulting in a fully structural strengthening system. Inside a PCCP line, the CFRP liner acts as a barrier that controls the level of strain experienced by the steel cylinder in the host pipe. The composite liner enables the steel cylinder to perform within its elastic range, to ensure the pipeline's long-term performance is maintained. CFRP liner designs are based on strain compatibility between the liner and host pipe.<ref>{{cite journal |last=Rahman |first=S. |date=November 2008 |title=Don't Stress Over Prestressed Concrete Cylinder Pipe Failures |journal=Opflow Magazine |pages=10–15 |url=http://www.awwa.org/publications/opflow/abstract/articleid/18373.aspx|volume=34|issue=11|doi=10.1002/j.1551-8701.2008.tb02004.x |url-status=live |archive-url=https://web.archive.org/web/20150402142138/http://www.awwa.org/publications/opflow/abstract/articleid/18373.aspx |archive-date=2 April 2015}}</ref>

CFRP is a more costly material than its counterparts in the construction industry, glass fiber-reinforced polymer (GFRP) and aramid fiber-reinforced polymer (AFRP), though CFRP is, in general, regarded as having superior properties. Much research continues to be done on using CFRP both for retrofitting and as an alternative to steel as a reinforcing or pre-stressing material. Cost remains an issue and long-term durability questions still remain. Some are concerned about the brittle nature of CFRP, in contrast to the ductility of steel. Though design codes have been drawn up by institutions such as the American Concrete Institute, there remains some hesitation among the engineering community about implementing these alternative materials. In part, this is due to a lack of standardization and the proprietary nature of the fiber and resin combinations on the market.

===Carbon-fiber microelectrodes===
Carbon fibers are used for fabrication of carbon-fiber [[Biology:Microelectrode|microelectrode]]s. In this application typically a single carbon fiber with diameter of 5–7 μm is sealed in a glass capillary.<ref>{{cite journal |first1=Carolyn M. |last1=Pike |first2=Chad P. |last2=Grabner |first3=Amy B. |last3=Harkins |title=Fabrication of Amperometric Electrodes|journal=Journal of Visualized Experiments|date=4 May 2009|issue=27|doi=10.3791/1040|pmc=2762914 |pmid=19415069}}</ref> At the tip the capillary is either sealed with epoxy and polished to make carbon-fiber disk microelectrode or the fiber is cut to a length of 75–150 μm to make carbon-fiber cylinder electrode. Carbon-fiber microelectrodes are used either in [[Biology:Amperometry|amperometry]] or [[Physics:Fast-scan cyclic voltammetry|fast-scan cyclic voltammetry]] for detection of biochemical signaling.

===Sports goods===
[[File:Carbon Fiber and Kevlar Canoe.jpg|thumb|A carbon-fiber and Kevlar canoe (Placid Boatworks Rapidfire at the Adirondack Canoe Classic)]]

CFRP is now widely used in sports equipment such as in squash, tennis, and badminton racquets, sport kite spars, high-quality arrow shafts, hockey sticks, fishing rods, surfboards, high end swim fins, and rowing [[Engineering:Racing shell|shells]]. Amputee athletes such as Jonnie Peacock use carbon fiber blades for running. It is used as a shank plate in some basketball sneakers to keep the foot stable, usually running the length of the shoe just above the sole and left exposed in some areas, usually in the arch.

Controversially, in 2006, cricket bats with a thin carbon-fiber layer on the back were introduced and used in competitive matches by high-profile players including Ricky Ponting and Michael Hussey. The carbon fiber was claimed to merely increase the durability of the bats, but it was banned from all first-class matches by the ICC in 2007.<ref>{{cite web |url=https://netcomposites.com/news/2006/october/03/icc-and-kookaburra-agree-to-withdrawal-of-carbon-bat/|title=ICC and Kookaburra Agree to Withdrawal of Carbon Bat|publisher=NetComposites|date=19 February 2006|access-date=1 October 2018}}</ref>

A CFRP [[Engineering:Bicycle frame|bicycle frame]] weighs less than one of steel, [[Chemistry:Aluminum|aluminum]], or [[Chemistry:Titanium|titanium]] having the same strength. The type and orientation of the carbon-fiber weave can be designed to maximize stiffness in required directions. Frames can be tuned to address different riding styles: sprint events require stiffer frames while endurance events may require more flexible frames for rider comfort over longer periods.<ref>{{cite web |url=http://www.lookcycle.com/en/technologies/carbon-technology/ |title=Carbon Technology |publisher=Look Cycle |access-date=30 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20161130050211/http://www.lookcycle.com/en/technologies/carbon-technology/ |archive-date=30 November 2016}}</ref> The variety of shapes it can be built into has further increased stiffness and also allowed [[Physics:Aerodynamics|aerodynamic]] tube sections. CFRP [[Engineering:Bicycle fork|forks]] including suspension fork crowns and steerers, [[Engineering:Bicycle handlebar|handlebars]], [[Engineering:Seatpost|seatpost]]s, and [[Engineering:Crankset|crank arm]]s are becoming more common on medium as well as higher-priced bicycles. CFRP [[Engineering:Bicycle wheel|rims]] remain expensive but their stability compared to aluminium reduces the need to re-true a wheel and the reduced mass reduces the [[Physics:Moment of inertia|moment of inertia]] of the wheel. CFRP spokes are rare and most carbon wheelsets retain traditional stainless steel spokes. CFRP also appears increasingly in other components such as derailleur parts, brake and shifter levers and bodies, cassette sprocket carriers, suspension linkages, disc brake rotors, pedals, shoe soles, and saddle rails. Although strong and light, impact, over-torquing, or improper installation of CFRP components has resulted in cracking and failures, which may be difficult or impossible to repair.<ref>{{cite journal |url=http://bicycling.com/blogs/boulderreport/2012/01/16/the-perils-of-progress/ |title=The Perils of Progress |journal=Bicycling Magazine |access-date=16 February 2013 |date=16 January 2012 |url-status=dead |archive-url=https://web.archive.org/web/20130123184259/http://bicycling.com/blogs/boulderreport/2012/01/16/the-perils-of-progress/ |archive-date=23 January 2013 }}</ref><ref>{{cite web |url=http://www.bustedcarbon.com/ |title=Busted Carbon |access-date=30 November 2016 |url-status=live |archive-url=https://web.archive.org/web/20161130174553/http://www.bustedcarbon.com/ |archive-date=30 November 2016}}</ref>

===Other applications===
The fire resistance of polymers and thermo-set composites is significantly improved if a thin layer of carbon fibers is moulded near the surface because a dense, compact layer of carbon fibers efficiently reflects heat.<ref>{{cite journal |first1=Z. |last1=Zhao |first2=J. |last2=Gou |title=Improved fire retardancy of thermoset composites modified with carbon nanofibers|journal= Sci. Technol. Adv. Mater. |volume=10|issue=1 |year=2009|page= 015005 |doi=10.1088/1468-6996/10/1/015005 |bibcode=2009STAdM..10a5005Z|pmc=5109595 |pmid=27877268}}</ref>

CFRP is being used in an increasing number of high-end products that require stiffness and low weight, these include:
*Musical instruments, including violin bows; guitar picks, necks (carbon fiber rods), and pick-guards; drum shells; bagpipe chanters; and entire musical instruments such as Luis and Clark's carbon fiber cellos, violas, and violins; and Blackbird Guitars' acoustic guitars and ukuleles; also audio components such as turntables and loudspeakers.
*Firearms use it to replace certain metal, wood, and fiberglass components but many of the internal parts are still limited to metal alloys as current reinforced plastics are unsuitable.
*High-performance drone bodies and other radio-controlled vehicle and aircraft components such as helicopter rotor blades.
*Lightweight poles such as: tripod legs, tent poles, fishing rods, billiards cues, walking sticks, and high-reach poles such as for window cleaning.
*Dentistry, carbon fiber posts are used in restoring root canal treated teeth.
*Railed train [[Engineering:Bogie|bogie]]s for passenger service. This reduces the weight by up to 50% compared to metal bogies, which contributes to energy savings.<ref>{{cite news |url=http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/carbon-fibre-reinforced-plastic-bogies-on-test.html |title=Carbon fibre reinforced plastic bogies on test |work=Railway Gazette |date=7 August 2016 |access-date=9 August 2016 |url-status=live |archive-url=https://web.archive.org/web/20160808152345/http://www.railwaygazette.com/news/traction-rolling-stock/single-view/view/carbon-fibre-reinforced-plastic-bogies-on-test.html |archive-date=8 August 2016}}</ref>
*Laptop shells and other high performance cases.
*Carbon woven fabrics.<ref>{{cite journal|last1=Lomov|first1=Stepan V.|last2=Gorbatikh|first2=Larissa|last3=Kotanjac|first3=Željko|last4=Koissin|first4=Vitaly|last5=Houlle|first5=Matthieu|last6=Rochez|first6=Olivier|last7=Karahan|first7=Mehmet|last8=Mezzo|first8=Luca|last9=Verpoest|first9=Ignaas|title=Compressibility of carbon woven fabrics with carbon nanotubes/nanofibres grown on the fibres|journal=Composites Science and Technology|date=February 2011|volume=71|issue=3|pages=315–325|doi=10.1016/j.compscitech.2010.11.024}}</ref><ref>{{cite news|last1=Hans|first1=Kreis|title=Carbon woven fabrics|url=https://compositesplaza.com/products/carbon/carbon-woven-fabrics|access-date=2 January 2018|work=compositesplaza.com|date=2 July 2014|language=en|archive-url=https://web.archive.org/web/20180702122309/https://compositesplaza.com/products/carbon/carbon-woven-fabrics|archive-date=2 July 2018|url-status=dead}}</ref>
*Archery, carbon fiber arrows and bolts, stock, and rail.
*As a filament for the 3D fused deposition modeling printing process, carbon fiber-reinforced plastic (polyamide-carbon filament) is used for the production of sturdy but lightweight tools and parts due to its high strength and tear length.<ref>{{cite web |url=https://evo-tech.eu/filamente/polyamid-cf |title=Polyamid CF Filament - 3D Druck mit EVO-tech 3D Druckern |trans-title=Polyamide CF Filament - 3D printing with EVO-tech 3D printers |publisher=EVO-tech |location=Austria |language=German |access-date=4 June 2019}}</ref>
*District heating pipe rehabilitation, using CIPP method.

==Disposal and recycling==
CFRPs have a long service lifetime when protected from the sun. When it is time to decommission CFRPs, they cannot be melted down in air like many metals. When free of vinyl (PVC or [[Chemistry:Polyvinyl chloride|polyvinyl chloride]]) and other halogenated polymers, CFRPs can be thermally decomposed via [[Chemistry:Thermal depolymerization|thermal depolymerization]] in an oxygen-free environment. This can be accomplished in a refinery in a one-step process. Capture and reuse of the carbon and monomers is then possible. CFRPs can also be milled or shredded at low temperature to reclaim the carbon fiber; however, this process shortens the fibers dramatically. Just as with downcycled paper, the shortened fibers cause the recycled material to be weaker than the original material. There are still many industrial applications that do not need the strength of full-length carbon fiber reinforcement. For example, chopped reclaimed carbon fiber can be used in consumer electronics, such as laptops. It provides excellent reinforcement of the polymers used even if it lacks the strength-to-weight ratio of an aerospace component.

==Carbon nanotube reinforced polymer (CNRP)==
In 2009, [[Company:Zyvex Technologies|Zyvex Technologies]] introduced carbon nanotube-reinforced epoxy and carbon [[Chemistry:Pre-preg|pre-preg]]s.<ref>{{cite press release|title=Zyvex Performance Materials Launch Line of Nano-Enhanced Adhesives that Add Strength, Cut Costs |url=http://www.zyvextech.com/www/dcms/files/data-sheets/epovex-adhesive-pr.pdf |publisher=Zyvex Performance Materials |date=9 October 2009 |access-date=26 March 2015 |url-status=dead |archive-url=https://web.archive.org/web/20121016170430/http://www.zyvextech.com/www/dcms/files/data-sheets/epovex-adhesive-pr.pdf |archive-date=16 October 2012}}</ref> [[Physics:Carbon nanotube|Carbon nanotube]] reinforced polymer (CNRP) is several times stronger and tougher than CFRP and is used in the [[Engineering:Lockheed Martin F-35 Lightning II|Lockheed Martin F-35 Lightning II]] as a structural material for aircraft.<ref>{{cite journal |last=Trimble |first=Stephen |date=26 May 2011 |url=http://www.flightglobal.com/articles/2011/05/26/357223/lockheed-martin-reveals-f-35-to-feature-nanocomposite.html |title=Lockheed Martin reveals F-35 to feature nanocomposite structures |journal=Flight International |access-date=26 March 2015 |url-status=live |archive-url=https://web.archive.org/web/20110530213822/http://www.flightglobal.com/articles/2011/05/26/357223/lockheed-martin-reveals-f-35-to-feature-nanocomposite.html |archive-date=30 May 2011}}</ref> CNRP still uses carbon fiber as the primary reinforcement, but the binding matrix is a carbon nanotube-filled epoxy.<ref>{{cite web|url=http://www.zyvextech.com/www/dcms/files/data-sheets/arovex-msds.pdf |title=AROVEX™ Nanotube Enhanced Epoxy Resin Carbon Fiber Prepreg – Material Safety Data Sheet |publisher=Zyvex Performance Materials |date=8 April 2009 |access-date=26 March 2015 |url-status=dead |archive-url=https://web.archive.org/web/20121016170251/http://www.zyvextech.com/www/dcms/files/data-sheets/arovex-msds.pdf |archive-date=16 October 2012}}</ref>

==See also==
*{{annotated link|Chemistry:Carbon fibers}}
*{{annotated link|Chemistry:Composite repair}}
*{{annotated link|Biology:Mechanics of Oscar Pistorius's running blades}}
*{{annotated link|Chemistry:Reinforced carbon–carbon}}

==References==
{{Reflist|30em}}

==External links==
*[https://www.carbonfiber.gr.jp/english/ Japan Carbon Fiber Manufacturers Association (English)]
*[https://web.archive.org/web/20070823130728/http://www.vtnews.vt.edu/story.php?relyear=2005&itemno=1074 Engineers design composite bracing system for injured Hokie running back Cedric Humes]
*[https://www.flightglobal.com/pdfarchive/view/1968/1968%20-%202417.html The New Steel] a 1968 ''Flight'' article on the announcement of carbon fiber
*[https://www.flightglobal.com/pdfarchive/view/1971/1971%20-%201784.html Carbon Fibres – the First Five Years] A 1971 ''Flight'' article on carbon fiber in the aviation field

{{DEFAULTSORT:Carbon Fiber-Reinforced Polymer}}
[[Category:Aerospace materials]]
[[Category:Carbon forms]]
[[Category:Composite materials]]
[[Category:Fibre-reinforced polymers]]
[[Category:Synthetic fibers]]

{{Sourceattribution|Carbon fiber reinforced polymer|1}}