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115-445: The BQM-167 was developed and manufactured by Composite Engineering Inc. (now part of Kratos Defense & Security Solutions), and is constructed of carbon fiber and epoxy -based materials. Two prototype targets were built and test flown in 2001. The BQM-167A was selected as the next-generation Air Force subscale aerial target in July 2002. A total of six targets were built for use during

230-409: A linear combination n u + m v , where n and m are integers. And, conversely, each pair of integers ( n , m ) defines a possible position for A2 . Given n and m , one can reverse this theoretical operation by drawing the vector w on the graphene lattice, cutting a strip of the latter along lines perpendicular to w through its endpoints A1 and A2 , and rolling the strip into

345-438: A vacuum bag can be used. A fiberglass, carbon fiber, or aluminum mold is polished and waxed, and has a 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

460-845: A (5,0) SWCNT that should be semiconducting in fact is metallic according to the calculations. Likewise, zigzag and chiral SWCNTs with small diameters that should be metallic have a finite gap (armchair nanotubes remain metallic). In theory, metallic nanotubes can carry an electric current density of 4 × 10 A/cm , which is more than 1,000 times greater than those of metals such as copper , where for copper interconnects , current densities are limited by electromigration . Carbon nanotubes are thus being explored as interconnects and conductivity-enhancing components in composite materials, and many groups are attempting to commercialize highly conducting electrical wire assembled from individual carbon nanotubes. There are significant challenges to be overcome however, such as undesired current saturation under voltage, and

575-1433: A 159 kg (351 lb) internal payload, a 227 kg (500 lb) external payload, and has a 45 kg (99 lb)-capable weapon hardpoint on each wing. The platform is recoverable on land or at sea using a parachute system. In May 2017, the UTAP-22 received the official name Mako . The aircraft costs between $ 2-$ 3 million. . . Data from  • US Air Force - Fact Sheet, BQM-167A  • Kratos Unmanned Systems - Quick Facs, BQM-167A General characteristics Performance Avionics IR and RF Tow Targets; IR and RF Wing Pods; Chaff / Flare Dispensing; Vector & Scalar Scoring Carbon fiber Carbon fiber-reinforced polymers ( American English ), carbon-fibre-reinforced polymers ( Commonwealth English ), carbon-fiber-reinforced plastics , carbon-fiber reinforced-thermoplastic ( CFRP , CRP , CFRTP ), also known as carbon fiber , carbon composite , or just carbon , are extremely strong and light fiber-reinforced plastics that contain carbon fibers . CFRPs can be expensive to produce, but are commonly used wherever high strength-to-weight ratio and stiffness (rigidity) are required, such as aerospace, superstructures of ships, automotive, civil engineering, sports equipment, and an increasing number of consumer and technical applications. The binding polymer

690-401: 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

805-560: A BQM-167 washed ashore in Boynton Beach, Florida after a weapon systems evaluation. On 23 November 2015, Kratos completed the second flight of its self-funded Unmanned Tactical Aerial Platform ( UTAP-22 ), a development of the BQM-167A converted into a low-cost unmanned combat aerial vehicle (UCAV). The test involved collaborative airborne operations with a manned AV-8B Harrier fighter for 94 minutes demonstrating command and control through

920-437: 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. Moreover, the trailing edge, along with the rear bulkhead, empennage , and un-pressurised fuselage are made of CFRP. However, many delays have pushed order delivery dates back because of problems with

1035-515: A chain of bi-connected 4-rings. These structures may not be realizable. The thinnest carbon nanotube proper is the armchair structure with type (2,2), which has a diameter of 0.3 nm. This nanotube was grown inside a multi-walled carbon nanotube. Assigning of the carbon nanotube type was done by a combination of high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy , and density functional theory (DFT) calculations. The thinnest freestanding single-walled carbon nanotube

1150-447: 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

1265-406: A connection between a metallic tube and a semiconducting one would represent a nanoscale heterojunction. Such a junction could therefore form a component of a nanotube-based electronic circuit. The adjacent image shows a junction between two multiwalled nanotubes. Junctions between nanotubes and graphene have been considered theoretically and studied experimentally. Nanotube-graphene junctions form

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1380-462: A core. Applications for CFRPs include the following: The Airbus A350 XWB is built of 53% CFRP including wing spars and fuselage components, overtaking the Boeing 787 Dreamliner , for the aircraft with the highest weight ratio for CFRP, which is 50%. This was one of the first commercial aircraft to have wing spars made from composites. The Airbus A380 was one of the first commercial airliners to have

1495-409: A cylinder so as to bring those two points together. If this construction is applied to a pair ( k ,0), the result is a zigzag nanotube, with closed zigzag paths of 2 k atoms. If it is applied to a pair ( k , k ), one obtains an armchair tube, with closed armchair paths of 4 k atoms. The structure of the nanotube is not changed if the strip is rotated by 60 degrees clockwise around A1 before applying

1610-606: A desirable material in nanoelectromechanical systems (NEMS) . The retraction force that occurs to telescopic motion is caused by the Lennard-Jones interaction between shells, and its value is about 1.5 nN. Junctions between two or more nanotubes have been widely discussed theoretically. Such junctions are quite frequently observed in samples prepared by arc discharge as well as by chemical vapor deposition . The electronic properties of such junctions were first considered theoretically by Lambin et al., who pointed out that

1725-419: A flurry of excitement and could be credited with inspiring the many scientists now studying applications of carbon nanotubes. Though Iijima has been given much of the credit for discovering carbon nanotubes, it turns out that the timeline of carbon nanotubes goes back much further than 1991. In 1952, L. V. Radushkevich and V. M. Lukyanovich published clear images of 50-nanometre diameter tubes made of carbon in

1840-475: A hollow tube, linearly extended with parallel carbon layer faces near the fiber core. This appears to be the observation of multi-walled carbon nanotubes at the center of the fiber. The mass-produced MWCNTs today are strongly related to the VPGCF developed by Endo. In fact, they call it the "Endo-process", out of respect for his early work and patents. In 1979, John Abrahamson presented evidence of carbon nanotubes at

1955-505: A mold, with epoxy either pre-impregnated into the fibers (also known as pre-preg ) or "painted" over it. High-performance parts using single molds are often vacuum-bagged and/or 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 EPS foam inside the non-cured laid-up carbon fiber. For simple pieces of which relatively few copies are needed (one or two per day),

2070-428: A nanometre-size diameter, that is to say for the discovery of carbon nanotubes. In 1976, Morinobu Endo of CNRS observed hollow tubes of rolled up graphite sheets synthesised by a chemical vapour-growth technique. The first specimens observed would later come to be known as single-walled carbon nanotubes (SWNTs). Endo, in his early review of vapor-phase-grown carbon fibers (VPCF), also reminded us that he had observed

2185-405: A nanotorus is a carbon nanotube bent into a torus (doughnut shape). Nanotori are predicted to have many unique properties, such as magnetic moments 1000 times larger than that previously expected for certain specific radii. Properties such as magnetic moment , thermal stability, etc. vary widely depending on the radius of the torus and the radius of the tube. Graphenated carbon nanotubes are

2300-431: A newly created material combining two previously discovered allotropes of carbon: carbon nanotubes and fullerenes . In this new material, fullerene-like "buds" are covalently bonded to the outer sidewalls of the underlying carbon nanotube. This hybrid material has useful properties of both fullerenes and carbon nanotubes. In particular, they have been found to be exceptionally good field emitters . In composite materials ,

2415-598: A novel radical-initiated thermal crosslinking method to fabricate macroscopic, free-standing, porous, all-carbon scaffolds using single- and multi-walled carbon nanotubes as building blocks. These scaffolds possess macro-, micro-, and nano-structured pores, and the porosity can be tailored for specific applications. These 3D all-carbon scaffolds/architectures may be used for the fabrication of the next generation of energy storage, supercapacitors, field emission transistors, high-performance catalysis, photovoltaics, and biomedical devices, implants, and sensors. Carbon nanobuds are

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2530-432: A number of field applications strengthening concrete, masonry, steel, cast iron, and timber structures. Their use in industry can be either for retrofitting to strengthen an existing structure or as an alternative reinforcing (or prestressing) material instead of steel from the outset of a project. Retrofitting has become the increasingly dominant use of the material in civil engineering, and applications include increasing

2645-497: A path to synthesising them was lacking until 1993, when Iijima and Ichihashi at NEC , and Bethune and others at IBM independently discovered that co-vaporising carbon and transition metals such as iron and cobalt could specifically catalyse SWCNT formation. These discoveries triggered research that succeeded in greatly increasing the efficiency of the catalytic production technique, and led to an explosion of work to characterise and find applications for SWCNTs. The true identity of

2760-422: 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

2875-448: A relatively new hybrid that combines graphitic foliates grown along the sidewalls of multiwalled or bamboo-style CNTs. The foliate density can vary as a function of deposition conditions (e.g., temperature and time) with their structure ranging from a few layers of graphene (< 10) to thicker, more graphite -like. The fundamental advantage of an integrated graphene -CNT structure is the high surface area three-dimensional framework of

2990-720: A single carbon fiber with diameter of 5–7 μm is sealed in a glass capillary. 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 amperometry or fast-scan cyclic voltammetry for detection of biochemical signalling. CFRPs are 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 shells . Amputee athletes such as Jonnie Peacock use carbon fiber blades for running. It

3105-419: A single-walled carbon nanotube is 2 G 0 , where G 0 = 2 e / h is the conductance of a single ballistic quantum channel . Because of the role of the π-electron system in determining the electronic properties of graphene , doping in carbon nanotubes differs from that of bulk crystalline semiconductors from the same group of the periodic table (e.g., silicon). Graphitic substitution of carbon atoms in

3220-453: A special class of nanotubes because their morphology and properties are similar to those of SWNTs but they are more resistant to attacks by chemicals. This is especially important when it is necessary to graft chemical functions to the surface of the nanotubes ( functionalization ) to add properties to the CNT. Covalent functionalization of SWNTs will break some C=C double bonds , leaving "holes" in

3335-427: A spiral, helical arrangement (chiral tube). In 1987, Howard G. Tennent of Hyperion Catalysis was issued a U.S. patent for the production of "cylindrical discrete carbon fibrils" with a "constant diameter between about 3.5 and about 70 nanometers..., length 10 times the diameter, and an outer region of multiple essentially continuous layers of ordered carbon atoms and a distinct inner core...." Helping to create

3450-516: A tactical data-link , autonomous formation flying with the AV-8B, and transfer of UTAP-22 control between operators in a tactical network and then to an independent control link. The 6.1 m (21 ft)-long turbojet-powered aircraft can travel at Mach 0.91 (693 mph; 1,115 km/h) up to an altitude of 50,000 ft (15,000 m) with a maximum range of 1,400 nmi (1,600 mi; 2,600 km) and an endurance of three hours. It can carry

3565-422: A thermocatalytic disproportionation of carbon monoxide. Using TEM images and XRD patterns, the authors suggested that their "carbon multi-layer tubular crystals" were formed by rolling graphene layers into cylinders. They speculated that via this rolling, many different arrangements of graphene hexagonal nets are possible. They suggested two such possible arrangements: a circular arrangement (armchair nanotube); and

Composite Engineering BQM-167 Skeeter - Misplaced Pages Continue

3680-413: Is also in picometres. (These formulas are only approximate, especially for small n and m where the bonds are strained; and they do not take into account the thickness of the wall.) The tilt angle α between u and w and the circumference c are related to the type indices n and m by: where arg( x , y ) is the clockwise angle between the X -axis and the vector ( x , y ); a function that

3795-440: Is a closed zigzag path that goes around the tube. One says that the tube is of the zigzag type or configuration, or simply is a zigzag nanotube . If the tube is instead encircled by a closed armchair path, it is said to be of the armchair type , or an armchair nanotube . An infinite nanotube that is of one type consists entirely of closed paths of that type, connected to each other. The zigzag and armchair configurations are not

3910-400: Is about 0.43 nm in diameter. Researchers suggested that it can be either (5,1) or (4,2) SWCNT, but the exact type of the carbon nanotube remains questionable. (3,3), (4,3), and (5,1) carbon nanotubes (all about 0.4 nm in diameter) were unambiguously identified using aberration-corrected high-resolution transmission electron microscopy inside double-walled CNTs. The observation of

4025-407: Is available in many programming languages as atan2 ( y , x ). Conversely, given c and α , one can get the type ( n , m ) by the formulas: which must evaluate to integers. If n and m are too small, the structure described by the pair ( n , m ) will describe a molecule that cannot be reasonably called a "tube", and may not even be stable. For example, the structure theoretically described by

4140-451: Is close to the distance between graphene layers in graphite, approximately 3.4 Å. The Russian Doll structure is observed more commonly. Its individual shells can be described as SWNTs, which can be metallic or semiconducting. Because of statistical probability and restrictions on the relative diameters of the individual tubes, one of the shells, and thus the whole MWNT, is usually a zero-gap metal. Double-walled carbon nanotubes (DWNTs) form

4255-409: Is dependent on the fiber orientation and machining condition of the cutting process. To reduce tool wear various types of coated tools are used in machining CFRP and CFRP-metal stack. The primary element of CFRPs is a carbon filament ; this is produced from a precursor polymer such as polyacrylonitrile (PAN), rayon , or petroleum pitch . For synthetic polymers such as PAN or rayon, the precursor

4370-438: Is first 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 ( carbonization ), producing

4485-424: Is in agreement with quantum/atomistic models. Because carbon nanotubes have a low density for a solid of 1.3 to 1.4 g/cm , its specific strength of up to 48,000 kN·m/kg is the best of known materials, compared to high-carbon steel's 154 kN·m/kg. Although the strength of individual CNT shells is extremely high, weak shear interactions between adjacent shells and tubes lead to significant reduction in

4600-518: 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

4715-613: Is most widely used in the "safety cell" 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. Many supercars over the past few decades have incorporated CFRPs extensively in their manufacture, using it for their monocoque chassis as well as other components. As far back as 1971,

Composite Engineering BQM-167 Skeeter - Misplaced Pages Continue

4830-413: Is much more difficult to process and more expensive. Despite their high initial strength-to-weight ratios, a design limitation of CFRPs are their lack of a definable 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

4945-604: Is no consensus on some terms describing carbon nanotubes in the scientific literature: both "-wall" and "-walled" are being used in combination with "single", "double", "triple", or "multi", and the letter C is often omitted in the abbreviation, for example, multi-walled carbon nanotube (MWNT). The International Standards Organization typically uses "single-walled carbon nanotube (SWCNT)" or "multi-walled carbon nanotube (MWCNT)" in its documents. Multi-walled nanotubes (MWNTs) consist of multiple rolled layers (concentric tubes) of graphene. There are two models that can be used to describe

5060-409: Is often a thermoset resin such as epoxy , but other thermoset or thermoplastic polymers, such as polyester , vinyl ester , or nylon, are sometimes used. The properties of the final CFRP product can be affected by the type of additives introduced to the binding matrix (resin). The most common additive is silica , but other additives such as rubber and carbon nanotubes can be used. Carbon fiber

5175-498: Is several times stronger and tougher than typical CFRPs and is used in the Lockheed Martin F-35 Lightning II as a structural material for aircraft. CNRP still uses carbon fiber as the primary reinforcement, but the binding matrix is a carbon nanotube-filled epoxy. Carbon nanotube A carbon nanotube ( CNT ) is a tube made of carbon with a diameter in the nanometre range ( nanoscale ). They are one of

5290-646: 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. CFRPs are being used in an increasing number of high-end products that require stiffness and low weight, these include: 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 polyvinyl chloride ) and other halogenated polymers, CFRPs can be thermally decomposed via thermal depolymerization in an oxygen-free environment. This can be accomplished in

5405-442: Is sometimes referred to as graphite-reinforced polymer or graphite fiber-reinforced polymer ( GFRP is less common, as it clashes with glass-(fiber)-reinforced polymer ). CFRP are composite materials . In this case the composite consists of two parts: a matrix and a reinforcement. In CFRP the reinforcement is carbon fiber, which provides its strength. The matrix is usually a thermosetting plastic, such as polyester resin, to bind

5520-401: Is the total composite modulus, V m {\displaystyle V_{m}} and V f {\displaystyle V_{f}} are the volume fractions of the matrix and fiber respectively in the composite, and E m {\displaystyle E_{m}} and E f {\displaystyle E_{f}} are the elastic moduli of

5635-436: 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. CFRPs can also be used 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

5750-412: 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

5865-633: The Citroën SM offered optional lightweight carbon fiber wheels. 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. CFRPs have become a notable material in structural engineering applications. Studied in an academic context as to their potential benefits in construction, CFRPs have also proved themselves cost-effective in

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5980-556: The Journal of Physical Chemistry Of Russia . This discovery was largely unnoticed, as the article was published in Russian, and Western scientists' access to Soviet press was limited during the Cold War . Monthioux and Kuznetsov mentioned in their Carbon editorial: The fact is, Radushkevich and Lukyanovich [...] should be credited for the discovery that carbon filaments could be hollow and have

6095-764: The allotropes of carbon . Two broad classes of carbon nanotubes are recognized: Carbon nanotubes can exhibit remarkable properties, such as exceptional tensile strength and thermal conductivity because of their nanostructure and strength of the bonds between carbon atoms. Some SWCNT structures exhibit high electrical conductivity while others are semiconductors . In addition, carbon nanotubes can be chemically modified. These properties are expected to be valuable in many areas of technology, such as electronics , optics , composite materials (replacing or complementing carbon fibres ), nanotechnology (including nanomedicine), and other applications of materials science . The predicted properties for SWCNTs were tantalising, but

6210-580: The brittle nature of CFRPs, 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 fibers are used for fabrication of carbon-fiber microelectrodes . In this application typically

6325-474: The ductility of the section, greatly increasing the resistance to collapse under dynamic 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

6440-403: The longest carbon nanotubes grown so far, around 0.5 metre (550 mm) long, was reported in 2013. These nanotubes were grown on silicon substrates using an improved chemical vapor deposition (CVD) method and represent electrically uniform arrays of single-walled carbon nanotubes. The shortest carbon nanotube can be considered to be the organic compound cycloparaphenylene , which

6555-470: The 14th Biennial Conference of Carbon at Pennsylvania State University . The conference paper described carbon nanotubes as carbon fibers that were produced on carbon anodes during arc discharge. A characterization of these fibers was given, as well as hypotheses for their growth in a nitrogen atmosphere at low pressures. In 1981, a group of Soviet scientists published the results of chemical and structural characterization of carbon nanoparticles produced by

6670-509: The CNTs coupled with the high edge density of graphene. Depositing a high density of graphene foliates along the length of aligned CNTs can significantly increase the total charge capacity per unit of nominal area as compared to other carbon nanostructures. Cup-stacked carbon nanotubes (CSCNTs) differ from other quasi-1D carbon structures, which normally behave as quasi-metallic conductors of electrons. CSCNTs exhibit semiconducting behavior because of

6785-443: The angle α between u and w , which may range from 0 to 30 degrees (inclusive both), is called the "chiral angle" of the nanotube. From n and m one can also compute the circumference c , which is the length of the vector w , which turns out to be: in picometres . The diameter d {\displaystyle d} of the tube is then c / π {\displaystyle c/\pi } , that

6900-430: The atom A will end up on opposite edges of the strip, over two atoms A1 and A2 of the graphene. The line from A1 to A2 will correspond to the circumference of the cylinder that went through the atom A , and will be perpendicular to the edges of the strip. In the graphene lattice, the atoms can be split into two classes, depending on the directions of their three bonds. Half the atoms have their three bonds directed

7015-445: The attached fullerene molecules may function as molecular anchors preventing slipping of the nanotubes, thus improving the composite's mechanical properties. A carbon peapod is a novel hybrid carbon material which traps fullerene inside a carbon nanotube. It can possess interesting magnetic properties with heating and irradiation. It can also be applied as an oscillator during theoretical investigations and predictions. In theory,

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7130-430: The basis of pillared graphene , in which parallel graphene sheets are separated by short nanotubes. Pillared graphene represents a class of three-dimensional carbon nanotube architectures . Recently, several studies have highlighted the prospect of using carbon nanotubes as building blocks to fabricate three-dimensional macroscopic (>100 nm in all three dimensions) all-carbon devices. Lalwani et al. have reported

7245-426: The brittle fracture mechanics presents unique challenges to engineers in failure detection since failure occurs catastrophically. 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 PEEK , which exhibits an order of magnitude greater toughness with similar elastic modulus and tensile strength. However, PEEK

7360-455: The carbon in an arc discharge. Thess et al. refined this catalytic method by vaporizing the carbon/transition-metal combination in a high-temperature furnace, which greatly improved the yield and purity of the SWNTs and made them widely available for characterization and application experiments. The arc discharge technique, well known to produce the famed Buckminsterfullerene , thus played a role in

7475-407: 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

7590-554: The covalent sp bonds formed between the individual carbon atoms. In 2000, a multiwalled carbon nanotube was tested to have a tensile strength of 63 GPa (9,100,000 psi). (For illustration, this translates into the ability to endure tension of a weight equivalent to 6,422 kilograms-force (62,980 N; 14,160 lbf) on a cable with cross-section of 1 mm (0.0016 sq in)). Further studies, such as one conducted in 2008, revealed that individual CNT shells have strengths of up to ≈100 GPa (15,000,000 psi), which

7705-562: The degenerate point (the point where the π [bonding] band meets the π* [anti-bonding] band, at which the energy goes to zero) is slightly shifted away from the K point in the Brillouin zone because of the curvature of the tube surface, causing hybridization between the σ* and π* anti-bonding bands, modifying the band dispersion. The rule regarding metallic versus semiconductor behavior has exceptions because curvature effects in small-diameter tubes can strongly influence electrical properties. Thus,

7820-409: The desired component. 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. For difficult or convoluted shapes, a filament winder can be used to make CFRP parts by winding filaments around a mandrel or

7935-421: The directions of u and w , may range from 0 (inclusive) to 60 degrees clockwise (exclusive). If the diagram is drawn with u horizontal, the latter is the tilt of the strip away from the vertical. A nanotube is chiral if it has type ( n , m ), with m > 0 and m ≠ n ; then its enantiomer (mirror image) has type ( m , n ), which is different from ( n , m ). This operation corresponds to mirroring

8050-402: The discoverers of carbon nanotubes is a subject of some controversy. A 2006 editorial written by Marc Monthioux and Vladimir Kuznetsov in the journal Carbon described the origin of the carbon nanotube. A large percentage of academic and popular literature attributes the discovery of hollow, nanometre-size tubes composed of graphitic carbon to Sumio Iijima of NEC in 1991. His paper initiated

8165-514: The discoveries of both multi- and single-wall nanotubes, extending the run of serendipitous discoveries relating to fullerenes. The discovery of nanotubes remains a contentious issue. Many believe that Iijima's report in 1991 is of particular importance because it brought carbon nanotubes into the awareness of the scientific community as a whole. In 2020, during an archaeological excavation of Keezhadi in Tamil Nadu , India , ~2600-year-old pottery

8280-602: The effective strength of multiwalled carbon nanotubes and carbon nanotube bundles down to only a few GPa. This limitation has been recently addressed by applying high-energy electron irradiation, which crosslinks inner shells and tubes, and effectively increases the strength of these materials to ≈60 GPa for multiwalled carbon nanotubes and ≈17 GPa for double-walled carbon nanotube bundles. CNTs are not nearly as strong under compression. Because of their hollow structure and high aspect ratio, they tend to undergo buckling when placed under compressive, torsional, or bending stress. On

8395-550: The fatigue failure properties of CFRPs are difficult to predict and design against; however emerging research has shed light on the effects of low velocity impacts on composites. Low velocity impacts can make carbon fibre polymers susceptible to damage. As a result, when using CFRPs 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

8510-401: The final carbon fiber. The carbon fibers filament yarns may be further treated to improve handling qualities, then wound onto bobbins . 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

8625-474: The flight performance demonstration (FPD) phase with its first flight 8 December 2004. A total of 13 FPD launches were made into March 2006. First acceptance testing was completed in August 2006, then pre-operational testing consisted of 13 test flights using production targets from August 2006 - June 2007. The first BQM-167 air-to-air missile live-fire mission took place 7 February 2007. Initial Operational Capability

8740-495: The following: One method of producing CFRP parts is by layering sheets of carbon fiber cloth into a 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 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

8855-415: The form of hydrogen embrittlement has been blamed for the gradual deterioration of the prestressing wires in many PCCP lines. Over the past decade, CFRPs have been used 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

8970-399: The hypothetical reconstruction above. Such a rotation changes the corresponding pair ( n , m ) to the pair (−2 m , n + m ). It follows that many possible positions of A2 relative to A1 — that is, many pairs ( n , m ) — correspond to the same arrangement of atoms on the nanotube. That is the case, for example, of the six pairs (1,2), (−2,3), (−3,1), (−1,−2), (2,−3), and (3,−1). In particular,

9085-583: The initial excitement associated with carbon nanotubes were Iijima's 1991 discovery of multi-walled carbon nanotubes in the insoluble material of arc-burned graphite rods; and Mintmire, Dunlap, and White's independent prediction that if single-walled carbon nanotubes could be made, they would exhibit remarkable conducting properties. Nanotube research accelerated greatly following the independent discoveries by Iijima and Ichihashi at NEC and Bethune et al. at IBM of methods to specifically produce single-walled carbon nanotubes by adding transition-metal catalysts to

9200-504: The length of the carbon-carbon bonds is fairly fixed, there are constraints on the diameter of the cylinder and the arrangement of the atoms on it. In the study of nanotubes, one defines a zigzag path on a graphene-like lattice as a path that turns 60 degrees, alternating left and right, after stepping through each bond. It is also conventional to define an armchair path as one that makes two left turns of 60 degrees followed by two right turns every four steps. On some carbon nanotubes, there

9315-440: The load capacity of old structures (such as bridges, beams, ceilings, columns and walls) 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. Applied to reinforced concrete structures for flexure,

9430-419: The manufacture of these parts. Many aircraft that use CFRPs 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 decades, 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

9545-568: The matrix and fibers respectively. 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 equation: The fracture toughness of carbon fiber reinforced plastics is governed by the mechanisms: 1) debonding between the carbon fiber and polymer matrix, 2) fiber pull-out, and 3) delamination between the CFRP sheets. 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,

9660-619: The matrix in CFRPs such as compressive, interlaminar shear, and impact properties. 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. Carbon fibers can cause galvanic corrosion when CRP parts are attached to aluminum or mild steel but not to stainless steel or titanium. Carbon Fiber Reinforced Plastics are very hard to machine, and cause significant tool wear. The tool wear in CFRP machining

9775-433: 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

9890-454: The much more resistive nanotube-to-nanotube junctions and impurities, all of which lower the electrical conductivity of the macroscopic nanotube wires by orders of magnitude, as compared to the conductivity of the individual nanotubes. Because of its nanoscale cross-section, electrons propagate only along the tube's axis. As a result, carbon nanotubes are frequently referred to as one-dimensional conductors. The maximum electrical conductance of

10005-547: The nanotube wall by boron or nitrogen dopants leads to p-type and n-type behavior, respectively, as would be expected in silicon. However, some non-substitutional ( intercalated or adsorbed) dopants introduced into a carbon nanotube, such as alkali metals and electron-rich metallocenes , result in n-type conduction because they donate electrons to the π-electron system of the nanotube. By contrast, π-electron acceptors such as FeCl 3 or electron-deficient metallocenes function as p-type dopants because they draw π-electrons away from

10120-647: The need to re-true a wheel and the reduced mass reduces the moment of inertia of the wheel. CFRP spokes are rare and most carbon wheelsets retain traditional stainless steel spokes. CFRPs also appear 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. The fire resistance of polymers and thermo-set composites

10235-419: The only structures that a single-walled nanotube can have. To describe the structure of a general infinitely long tube, one should imagine it being sliced open by a cut parallel to its axis, that goes through some atom A , and then unrolled flat on the plane, so that its atoms and bonds coincide with those of an imaginary graphene sheet—more precisely, with an infinitely long strip of that sheet. The two halves of

10350-463: The other hand, there is evidence that in the radial direction they are rather soft. The first transmission electron microscope observation of radial elasticity suggested that even van der Waals forces can deform two adjacent nanotubes. Later, nanoindentations with an atomic force microscope were performed by several groups to quantitatively measure the radial elasticity of multiwalled carbon nanotubes and tapping/contact mode atomic force microscopy

10465-423: The pair (1,0) (the limiting "zigzag" type) would be just a chain of carbons. That is a real molecule, the carbyne ; which has some characteristics of nanotubes (such as orbital hybridization, high tensile strength, etc.) — but has no hollow space, and may not be obtainable as a condensed phase. The pair (2,0) would theoretically yield a chain of fused 4-cycles; and (1,1), the limiting "armchair" structure, would yield

10580-401: The pairs ( k ,0) and (0, k ) describe the same nanotube geometry. These redundancies can be avoided by considering only pairs ( n , m ) such that n > 0 and m ≥ 0; that is, where the direction of the vector w lies between those of u (inclusive) and v (exclusive). It can be verified that every nanotube has exactly one pair ( n , m ) that satisfies those conditions, which is called

10695-494: 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. While the carbon fibers themselves are not affected by the moisture diffusing into the material, the moisture plasticizes the polymer matrix. This leads to significant changes in properties that are dominantly influenced by

10810-436: The proportion of the carbon fibers relative to the polymer. 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. The equation: is valid for composite materials with the fibers oriented in the direction of the applied load. E c {\displaystyle E_{c}}

10925-414: The reinforcements together. Because CFRPs consist of two distinct elements, the material properties depend on these two elements. Reinforcement gives CFRPs their strength and rigidity, measured by stress and elastic modulus respectively. Unlike isotropic materials like steel and aluminum, CFRPs have directional strength properties. The properties of a CFRP depend on the layouts of the carbon fiber and

11040-649: 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

11155-437: The same class. Let u and v be two linearly independent vectors that connect the graphene atom A1 to two of its nearest atoms with the same bond directions. That is, if one numbers consecutive carbons around a graphene cell with C1 to C6, then u can be the vector from C1 to C3, and v be the vector from C1 to C5. Then, for any other atom A2 with same class as A1 , the vector from A1 to A2 can be written as

11270-404: The same way, and half have their three bonds rotated 180 degrees relative to the first half. The atoms A1 and A2 , which correspond to the same atom A on the cylinder, must be in the same class. It follows that the circumference of the tube and the angle of the strip are not arbitrary, because they are constrained to the lengths and directions of the lines that connect pairs of graphene atoms in

11385-546: The section, both increasing the stiffness of the section and lowering the neutral axis , thus greatly reducing the maximum tensile stress in the cast iron. In the United States, prestressed 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 19,000 miles (31,000 km) of PCCP were installed between 1940 and 2006. Corrosion in

11500-502: The stacking microstructure of graphene layers. Many properties of single-walled carbon nanotubes depend significantly on the ( n , m ) type, and this dependence is non- monotonic (see Kataura plot ). In particular, the band gap can vary from zero to about 2 eV and the electrical conductivity can show metallic or semiconducting behavior. Carbon nanotubes are the strongest and stiffest materials yet discovered in terms of tensile strength and elastic modulus . This strength results from

11615-709: 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. CFRPs are more costly materials than commonly used their counterparts in the construction industry, glass fiber-reinforced polymers (GFRPs) and aramid fiber-reinforced polymers (AFRPs), though CFRPs are, in general, regarded as having superior properties. Much research continues to be done on using CFRPs both for retrofitting and as an alternative to steel as reinforcing or prestressing materials. Cost remains an issue and long-term durability questions still remain. Some are concerned about

11730-429: 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. In 2009, Zyvex Technologies introduced carbon nanotube-reinforced epoxy and carbon pre-pregs . Carbon nanotube reinforced polymer (CNRP)

11845-494: The structure on the nanotube and thus modifying both its mechanical and electrical properties. In the case of DWNTs, only the outer wall is modified. DWNT synthesis on the gram-scale by the CCVD technique was first proposed in 2003 from the selective reduction of oxide solutions in methane and hydrogen. The telescopic motion ability of inner shells, allowing them to act as low-friction, low-wear nanobearings and nanosprings, may make them

11960-512: The structures of multi-walled nanotubes. In the Russian Doll model, sheets of graphite are arranged in concentric cylinders, e.g., a (0,8) single-walled nanotube (SWNT) within a larger (0,17) single-walled nanotube. In the Parchment model, a single sheet of graphite is rolled in around itself, resembling a scroll of parchment or a rolled newspaper. The interlayer distance in multi-walled nanotubes

12075-413: The tube's type . Conversely, for every type there is a hypothetical nanotube. In fact, two nanotubes have the same type if and only if one can be conceptually rotated and translated so as to match the other exactly. Instead of the type ( n , m ), the structure of a carbon nanotube can be specified by giving the length of the vector w (that is, the circumference of the nanotube), and the angle α between

12190-406: The tubular axis. For a given ( n , m ) nanotube, if n = m , the nanotube is metallic; if n − m is a multiple of 3 and n ≠ m, then the nanotube is quasi-metallic with a very small band gap, otherwise the nanotube is a moderate semiconductor . Thus, all armchair ( n = m ) nanotubes are metallic, and nanotubes (6,4), (9,1), etc. are semiconducting. Carbon nanotubes are not semimetallic because

12305-447: The unrolled strip about the line L through A1 that makes an angle of 30 degrees clockwise from the direction of the u vector (that is, with the direction of the vector u + v ). The only types of nanotubes that are achiral are the ( k ,0) "zigzag" tubes and the ( k , k ) "armchair" tubes. If two enantiomers are to be considered the same structure, then one may consider only types ( n , m ) with 0 ≤ m ≤ n and n > 0. Then

12420-702: The unusual multi-material and anisotropic nature of CFRPs. In 1968 a Hyfil carbon-fiber fan assembly was in service on the Rolls-Royce Conways of the Vickers VC10s operated by BOAC . Specialist aircraft designers and manufacturers Scaled Composites have made extensive use of CFRPs throughout their design range, including the first private crewed spacecraft Spaceship One . CFRPs are widely used in micro air vehicles (MAVs) because of their high strength-to-weight ratio. CFRPs are extensively used in high-end automobile racing. The high cost of carbon fiber

12535-407: The use of autoclave pressures to purge the residual gases out. A quicker method uses a compression mold , also commonly known as carbon fiber forging. This is a two (male and female), or multi-piece mold, usually made out of aluminum or steel and more recently 3D printed plastic. The mold components are pressed together with the fabric and resin loaded into the inner cavity that ultimately becomes

12650-422: The use of CFRPs typically has a large impact on strength (doubling or more the strength of the section is not uncommon), but only moderately increases stiffness (as little as 10%). This is because the material used in such applications is typically very strong (e.g., 3 GPa ultimate tensile strength , more than 10 times mild steel) but not particularly stiff (150 to 250 GPa elastic modulus, a little less than steel,

12765-441: Was achieved in 2008. Each target cost US$ 570,000. The 82nd Aerial Targets Squadron operates and maintains the target at Tyndall Air Force Base , Florida . The drone is land-launched using a rocket-assisted takeoff and launched from a rail system, and recovered on land or sea using a parachute system. After assessment and refurbishment, the drone is placed back into service. The USAF has had 37 in inventory. On 19 March 2021,

12880-411: Was also performed on single-walled carbon nanotubes. Their high Young's modulus in the linear direction, of on the order of several GPa (and even up to an experimentally-measured 1.8 TPa, for nanotubes near 2.4 μm in length ), further suggests they may be soft in the radial direction. Unlike graphene, which is a two-dimensional semimetal , carbon nanotubes are either metallic or semiconducting along

12995-955: Was claimed to merely increase the durability of the bats, but it was banned from all first-class matches by the ICC in 2007. A CFRP bicycle frame weighs less than one of steel, aluminum, or 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. The variety of shapes it can be built into has further increased stiffness and also allowed aerodynamic tube sections. CFRP forks including suspension fork crowns and steerers, handlebars , seatposts , and crank arms are becoming more common on medium as well as higher-priced bicycles. CFRP rims remain expensive but their stability compared to aluminium reduces

13110-418: Was discovered whose coatings appear to contain carbon nanotubes. The robust mechanical properties of the nanotubes are partially why the coatings have lasted for so many years, say the scientists. The structure of an ideal (infinitely long) single-walled carbon nanotube is that of a regular hexagonal lattice drawn on an infinite cylindrical surface, whose vertices are the positions of the carbon atoms. Since

13225-486: Was synthesized in 2008 by Ramesh Jasti . Other small molecule carbon nanotubes have been synthesized since. The highest density of CNTs was achieved in 2013, grown on a conductive titanium -coated copper surface that was coated with co-catalysts cobalt and molybdenum at lower than typical temperatures of 450 °C. The tubes averaged a height of 380 nm and a mass density of 1.6 g cm . The material showed ohmic conductivity (lowest resistance ~22 kΩ). There

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