Carbon-fiber reinforced polymer
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.
[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.
[10][11][12] 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.
[14] 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.
[1] The primary element of CFRPs is a carbon filament; this is produced from a precursor polymer such as polyacrylonitrile (PAN), rayon, or petroleum pitch.
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.
Also, because larger amounts of resin are more difficult to bleed out with wet layup methods, pre-preg parts generally have fewer pinholes.
A recurrent problem is the monitoring of structural ageing, for which new methods are constantly investigated, due to the unusual multi-material and anisotropic[24][25][26] nature of CFRPs.
[29] 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.
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.
[32][33] 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.
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.
In the United States, prestressed concrete cylinder pipes (PCCP) account for a vast majority of water transmission mains.
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.
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.
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.
[41] CFRPs are being used in an increasing number of high-end products that require stiffness and low weight, these include: The key aspect of recycling fiber-reinforced polymers is preserving their mechanical properties while successfully recovering both the thermoplastic matrix and the reinforcing fibers.
When free of vinyl (PVC or polyvinyl chloride) and other halogenated polymers, CFRPs recycling processes can be categorized into four main approaches: mechanical, thermal, chemical, and biological.
Each method offers distinct advantages in terms of material or energy recovery, contributing to sustainability efforts in composite waste management.
This processes imply the recovery of the fibers by the removal of the resin by volatilizing it, leading to by-products such as gases, liquids or inorganic matter [49].
After a shredding step to 6-20 mm size, the composite is introduced into a bed of silica sand, on a metallic mesh, in which the resin will be decomposed into oxidized molecules and fiber filaments.
The matrix is fully oxidized in a second burner operating at approximatively 1,000 °C (1,850 °F) leading to energy recovery and a clean flue gas [50].
The chemical recycling of CFRPs involves using a reactive solvent at relatively low temperatures (below 350°C) to break down the resin while leaving the fibers intact for reuse.
The solvent, often combined with co-solvents or catalysts, penetrates the composite and breaks specific chemical bonds, resulting in recovered monomers from the resin and clean, long fibers with preserved mechanical properties.
It requires specialized equipment capable of handling corrosive solvents, hazardous chemicals, and high temperatures or pressures, especially when operating under supercritical conditions.
As research advances, biological recycling may offer an effective means of reducing plastic composite waste in a sustainable manner [53].
[54] 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.
