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. [1] [2] [3] [4]
The binding polymer is often a thermoset resin such as epoxy, but other thermoset or thermoplastic polymers, such as polyester, vinyl ester, or nylon, are sometimes used. [4] 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 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 the reinforcements together. [5] 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 the proportion of the carbon fibers relative to the polymer. [6] 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. [7] The following equation,
is valid for composite materials with the fibers oriented in the direction of the applied load. is the total composite modulus, and are the volume fractions of the matrix and fiber respectively in the composite, and and are the elastic moduli of the matrix and fibers respectively. [7] 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: [7]
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. [8] 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. [8] 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. [8] However, PEEK is much more difficult to process and more expensive. [8]
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 the fatigue failure properties of CFRPs are difficult to predict and design against. 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 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. [9] While the carbon fibers themselves are not affected by the moisture diffusing into the material, the moisture plasticizes the polymer matrix. [8] This led to significant changes in properties that are dominantly influenced by the matrix in CFRPs such as compressive, interlaminar shear, and impact properties. [10] 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. [8] [11]
Carbon fibers can cause galvanic corrosion when CRP parts are attached to aluminum or mild steel but not to stainless steel or titanium. [12]
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. To reduce tool wear various types of coated tools are used in machining CFRP and CFRP-metal stack. [1]
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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 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 the final carbon fiber. The carbon fibers filament yarns may be further treated to improve handling qualities, then wound on to bobbins. [13] 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. [14]
Many CFRP parts are created with a single layer of carbon fabric that is backed with fiberglass. [15] 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. [16] 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:
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 a mold, with epoxy either preimpregnated 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 (1–2 per day), 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 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 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 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 a core.
Applications for CFRPs include the following:
The Airbus A350 XWB is built of 52% CFRP [17] including wing spars and fuselage components, overtaking the Boeing 787 Dreamliner, for the aircraft with the highest weight ratio for CFRP, which is 50%. [18] 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 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 ] Moreover, the trailing edge, along with the rear bulkhead, empennage, and un-pressurised fuselage are made of CFRP. [19] However, many delays have pushed order delivery dates back because of problems with 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 the unusual multi-material and anisotropic nature of CFRPs. [20]
In 1968 a Hyfil carbon-fiber fan assembly was in service on the Rolls-Royce Conways of the Vickers VC10s operated by BOAC. [21]
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. [22] 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" 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. [23]
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. [24] As far back as 1971, the Citroën SM offered optional lightweight carbon fiber wheels. [25] [26]
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 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 pre-stressing) 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 the load capacity of old structures (such as bridges) 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. [27]
Applied to reinforced concrete structures for flexure, 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, 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.
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 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 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 19,000 miles (31,000 km) 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 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 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. [28]
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 pre-stressing materials. Cost remains an issue and long-term durability questions still remain. Some are concerned about 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 a single carbon fiber with diameter of 5–7 μm is sealed in a glass capillary. [29] 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 signaling.
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 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. [30]
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. [31] 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 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. [32] [33]
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. [34]
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 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.
In 2009, Zyvex Technologies introduced carbon nanotube-reinforced epoxy and carbon pre-pregs. [40] Carbon nanotube reinforced polymer (CNRP) 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. [41] CNRP still uses carbon fiber as the primary reinforcement, [42] but the binding matrix is a carbon nanotube-filled epoxy. [43]
A composite material is a material which is produced from two or more constituent materials. These constituent materials have notably dissimilar chemical or physical properties and are merged to create a material with properties unlike the individual elements. Within the finished structure, the individual elements remain separate and distinct, distinguishing composites from mixtures and solid solutions.
Carbon fibers or carbon fibres are fibers about 5 to 10 micrometers (0.00020–0.00039 in) in diameter and composed mostly of carbon atoms. Carbon fibers have several advantages: high stiffness, high tensile strength, high strength to weight ratio, high chemical resistance, high-temperature tolerance, and low thermal expansion. These properties have made carbon fiber very popular in aerospace, civil engineering, military, motorsports, and other competition sports. However, they are relatively expensive compared to similar fibers, such as glass fiber, basalt fibers, or plastic fibers.
Fiberglass or fibreglass is a common type of fiber-reinforced plastic using glass fiber. The fibers may be randomly arranged, flattened into a sheet called a chopped strand mat, or woven into glass cloth. The plastic matrix may be a thermoset polymer matrix—most often based on thermosetting polymers such as epoxy, polyester resin, or vinyl ester resin—or a thermoplastic.
In materials science, a thermosetting polymer, often called a thermoset, is a polymer that is obtained by irreversibly hardening ("curing") a soft solid or viscous liquid prepolymer (resin). Curing is induced by heat or suitable radiation and may be promoted by high pressure or mixing with a catalyst. Heat is not necessarily applied externally, and is often generated by the reaction of the resin with a curing agent. Curing results in chemical reactions that create extensive cross-linking between polymer chains to produce an infusible and insoluble polymer network.
Lamination is the technique/process of manufacturing a material in multiple layers, so that the composite material achieves improved strength, stability, sound insulation, appearance, or other properties from the use of the differing materials, such as plastic. A laminate is a permanently assembled object created using heat, pressure, welding, or adhesives. Various coating machines, machine presses and calendering equipment are used.
Fibre-reinforced plastic is a composite material made of a polymer matrix reinforced with fibres. The fibres are usually glass, carbon, aramid, or basalt. Rarely, other fibres such as paper, wood, boron, or asbestos have been used. The polymer is usually an epoxy, vinyl ester, or polyester thermosetting plastic, though phenol formaldehyde resins are still in use.
Filament winding is a fabrication technique mainly used for manufacturing open (cylinders) or closed end structures. This process involves winding filaments under tension over a rotating mandrel. The mandrel rotates around the spindle while a delivery eye on a carriage traverses horizontally in line with the axis of the rotating mandrel, laying down fibers in the desired pattern or angle to the rotational axis. The most common filaments are glass or carbon and are impregnated with resin by passing through a bath as they are wound onto the mandrel. Once the mandrel is completely covered to the desired thickness, the resin is cured. Depending on the resin system and its cure characteristics, often the mandrel is autoclaved or heated in an oven or rotated under radiant heaters until the part is cured. Once the resin has cured, the mandrel is removed or extracted, leaving the hollow final product. For some products such as gas bottles, the 'mandrel' is a permanent part of the finished product forming a liner to prevent gas leakage or as a barrier to protect the composite from the fluid to be stored.
A biocomposite is a composite material formed by a matrix (resin) and a reinforcement of natural fibers. Environmental concern and cost of synthetic fibres have led the foundation of using natural fibre as reinforcement in polymeric composites. The matrix phase is formed by polymers derived from renewable and nonrenewable resources. The matrix is important to protect the fibers from environmental degradation and mechanical damage, to hold the fibers together and to transfer the loads on it. In addition, biofibers are the principal components of biocomposites, which are derived from biological origins, for example fibers from crops, recycled wood, waste paper, crop processing byproducts or regenerated cellulose fiber (viscose/rayon). The interest in biocomposites is rapidly growing in terms of industrial applications and fundamental research, due to its great benefits. Biocomposites can be used alone, or as a complement to standard materials, such as carbon fiber. Advocates of biocomposites state that use of these materials improve health and safety in their production, are lighter in weight, have a visual appeal similar to that of wood, and are environmentally superior.
Sheet moulding compound (SMC) or sheet moulding composite is a ready to mould glass-fibre reinforced polyester material primarily used in compression moulding. The sheet is provided in rolls weighing up to 1000 kg. Alternatively the resin and related materials may be mixed on site when a producer wants greater control over the chemistry and filler.
Filler materials are particles added to resin or binders that can improve specific properties, make the product cheaper, or a mixture of both. The two largest segments for filler material use is elastomers and plastics. Worldwide, more than 53 million tons of fillers are used every year in application areas such as paper, plastics, rubber, paints, coatings, adhesives, and sealants. As such, fillers, produced by more than 700 companies, rank among the world's major raw materials and are contained in a variety of goods for daily consumer needs. The top filler materials used are ground calcium carbonate (GCC), precipitated calcium carbonate (PCC), kaolin, talc, and carbon black. Filler materials can affect the tensile strength, toughness, heat resistance, color, clarity, etc. A good example of this is the addition of talc to polypropylene. Most of the filler materials used in plastics are mineral or glass based filler materials. Particulates and fibers are the main subgroups of filler materials. Particulates are small particles of filler that are mixed in the matrix where size and aspect ratio are important. Fibers are small circular strands that can be very long and have very high aspect ratios.
Fiber volume ratio is an important mathematical element in composite engineering. Fiber volume ratio, or fiber volume fraction, is the percentage of fiber volume in the entire volume of a fiber-reinforced composite material. When manufacturing polymer composites, fibers are impregnated with resin. The amount of resin to fiber ratio is calculated by the geometric organization of the fibers, which affects the amount of resin that can enter the composite. The impregnation around the fibers is highly dependent on the orientation of the fibers and the architecture of the fibers. The geometric analysis of the composite can be seen in the cross-section of the composite. Voids are often formed in a composite structure throughout the manufacturing process and must be calculated into the total fiber volume fraction of the composite. The fraction of fiber reinforcement is very important in determining the overall mechanical properties of a composite. A higher fiber volume fraction typically results in better mechanical properties of the composite.
Three-dimensional composites use fiber preforms constructed from yarns or tows arranged into complex three-dimensional structures. These can be created from a 3D weaving process, a 3D knitting process, a 3D braiding process, or a 3D lay of short fibers. A resin is applied to the 3D preform to create the composite material. Three-dimensional composites are used in highly engineered and highly technical applications in order to achieve complex mechanical properties. Three-dimensional composites are engineered to react to stresses and strains in ways that are not possible with traditional composite materials composed of single direction tows, or 2D woven composites, sandwich composites or stacked laminate materials.
In materials science, advanced composite materials (ACMs) are materials that are generally characterized by unusually high strength fibres with unusually high stiffness, or modulus of elasticity characteristics, compared to other materials, while bound together by weaker matrices. These are termed "advanced composite materials" in comparison to the composite materials commonly in use such as reinforced concrete, or even concrete itself. The high strength fibers are also low density while occupying a large fraction of the volume.
Tailored fiber placement (TFP) is a textile manufacturing technique based on the principle of sewing for a continuous placement of fibrous material for composite components. The fibrous material is fixed with an upper and lower stitching thread on a base material. Compared to other textile manufacturing processes fiber material can be placed near net-shape in curvilinear patterns upon a base material in order to create stress adapted composite parts.
A void or a pore is three-dimensional region that remains unfilled with polymer and fibers in a composite material. Voids are typically the result of poor manufacturing of the material and are generally deemed undesirable. Voids can affect the mechanical properties and lifespan of the composite. They degrade mainly the matrix-dominated properties such as interlaminar shear strength, longitudinal compressive strength, and transverse tensile strength. Voids can act as crack initiation sites as well as allow moisture to penetrate the composite and contribute to the anisotropy of the composite. For aerospace applications, a void content of approximately 1% is still acceptable, while for less sensitive applications, the allowance limit is 3-5%. Although a small increase in void content may not seem to cause significant issues, a 1-3% increase in void content of carbon fiber reinforced composite can reduce the mechanical properties by up to 20%
Thermoplastics containing short fiber reinforcements were first introduced commercially in the 1960s. The most common type of fibers used in short fiber thermoplastics are glass fiber and carbon fiber . Adding short fibers to thermoplastic resins improves the composite performance for lightweight applications. In addition, short fiber thermoplastic composites are easier and cheaper to produce than continuous fiber reinforced composites. This compromise between cost and performance allows short fiber reinforced thermoplastics to be used in myriad applications.
Carbon fiber testing is a set of various different tests that researchers use to characterize the properties of carbon fiber. The results for the testing are used to aid the manufacturer and developers decisions selecting and designing material composites, manufacturing processes and for ensured safety and integrity. Safety-critical carbon fiber components, such as structural parts in machines, vehicles, aircraft or architectural elements are subject to testing.
Transfer molding is a manufacturing process in which casting material is forced into a mold. Transfer molding is different from compression molding in that the mold is enclosed rather than open to the fill plunger resulting in higher dimensional tolerances and less environmental impact. Compared to injection molding, transfer molding uses higher pressures to uniformly fill the mold cavity. This allows thicker reinforcing fiber matrices to be more completely saturated by resin. Furthermore, unlike injection molding the transfer mold casting material may start the process as a solid. This can reduce equipment costs and time dependency. The transfer process may have a slower fill rate than an equivalent injection molding process.
CFSMC, or Carbon Fiber Sheet Molding Compound, is a ready to mold carbon fiber reinforced polymer composite material used in compression molding. While traditional SMC utilizes chopped glass fibers in a polymer resin, CFSMC utilizes chopped carbon fibers. The length and distribution of the carbon fibers is more regular, homogeneous, and constant than the standard glass SMC. CFSMC offers much higher stiffness and usually higher strength than standard SMC, but at a higher cost.
In materials science, a polymer matrix composite (PMC) is a composite material composed of a variety of short or continuous fibers bound together by a matrix of organic polymers. PMCs are designed to transfer loads between fibers of a matrix. Some of the advantages with PMCs include their light weight, high resistance to abrasion and corrosion, and high stiffness and strength along the direction of their reinforcements.
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