What are composite materials?
Composite materials (also referred to as composition materials, or simply composites) are materials formed by combining two or more materials with different properties to produce an end material with unique characteristics. These materials do not blend or dissolve together but remain distinct within the final composite structure. Composite materials can be made to be stronger, lighter or more durable than traditional materials due to properties they gain from combining their different components.
Most composites are made up of two materials - the matrix (or binder) surrounds a cluster of fibers or fragments of a stronger material (reinforcement). A common example of this structure is fiberglass, which was developed in the 1940’s to be the first modern composite and is still in widespread use. In fiberglass, fine fibers of glass, which are woven into a cloth of sorts, act as the reinforcement in a plastic or resin matrix.
While composite materials are not a new concept (for example, mud bricks, made from dried mud embedded with straw pieces, have been around for thousands of years), recent technologies have brought many new and exciting composites to existence. By careful selection of matrix and reinforcement (as well as the best manufacturing process to bring them together) it is possible to create significantly superior materials, with tailored properties for specific needs. Typical composite materials include composite building materials like cement and concrete, different metal composites, plastic composites and ceramic composites.
How are composite materials made?
The three main factors that help mold the end composite material are the matrix, reinforcement and manufacturing process. As matrix, many composites use resins, which are thermosetting or thermosoftening plastics (hence the name ‘reinforced plastics’ often given to them). These are polymers that hold the reinforcement together and help determine the physical properties of the end composite.
Thermosetting plastics begin as liquid but then harden with heat. They do not return to liquid state and so they are durable, even in extreme exposure to chemicals and wear. Thermosoftening plastics are hard at low temperatures and but soften with heat. They are less commonly used but possess interesting advantages like long shelf life of raw material and capacity for recycling. There are other matrix materials such as ceramics, carbon and metals that are used for specific purposes.
Reinforcement materials grow more varied with time and technology, but the most commonly used ones are still glass fibers. Advanced composites tend to favor carbon fibers as reinforcement, which are much stronger than glass fibers, but are also more expensive. Carbon fiber composites are strong and light, and are used in aircraft structures and sports gear (golf clubs and various rackets). They are also increasingly used to replace metals that replace human bones. Some polymers make good reinforcement materials, and help make composites that are strong and light.
The manufacturing process usually involves a mould, in which the reinforcement is first placed and then the semi-liquid matrix is sprayed or poured in to form the object. Moulding processes are traditionally done by hand, though machine processing is becoming more common. One of the new methods is called ‘pultrusion’ and is ideal for making products that are straight and have a constant cross section, like different kinds of beams. Products that of thin or complex shape (like curved panels) are built up by applying sheets of woven fiber reinforcement, saturated with matrix material, over a mould. Advanced composites (like those which are used in aircraft) are usually made from a honeycomb of plastic held between two sheets of carbon-fiber reinforced composite material, which results in high strength, low weight and bending stiffness.
Where can composites be found?
Composite materials have many obvious advantages, as they can be made to be lightweight, strong, corrosion and heat resistant, flexible, transparent and more according to specific needs. Composites are already used in many industries, like boats, aerospace, sports equipment (golf shafts, tennis rackets, surfboards, hockey sticks and more), Automotive components, wind turbine blades, body armour, building materials, bridges, medical utilities and others. Composite materials’ merits and potential assures ample research in the field which is hoped to bring future developments and implementations in additional markets.
Modern aviation is a specific example of an industry with complex needs and requirements, which benefits greatly from composite materials’ advantages. This industry raises demands of light and strong materials, that are also durable to heat and corrosion. It is no surprise, then, that many aircraft have wing and tail sections, as well as propellers and rotor blades made of composites, along with much of the internal structure.
What is graphene?
Graphene is a two-dimensional matrix of carbon atoms, arranged in a honeycomb lattice. A single square-meter sheet of graphene would weigh just 0.0077 grams but could support up to four kilograms. That means it is thin and lightweight but also incredibly strong. It also has a large surface area, great heat and electricity conductivity and a variety of additional incredible traits. This is probably why scientists and researchers call it “a miracle material” and predict it will revolutionize just about every industry known to man.
Graphene and composite materials
As was stated before, graphene has a myriad of unprecedented attributes, any number of which could potentially be used to make extraordinary composites. The presence of graphene can enhance the conductivity and strength of bulk materials and help create composites with superior qualities. Graphene can also be added to metals, polymers and ceramics to create composites that are conductive and resistant to heat and pressure.
Graphene composites have many potential applications, with much research going on to create unique and innovative materials. The applications seem endless, as one graphene-polymer proves to be light, flexible and an excellent electrical conductor, while another dioxide-graphene composite was found to be of interesting photocatalytic efficiencies, with many other possible coupling of materials to someday make all kinds of composites. The potential of graphene composites includes medical implants, engineering materials for aerospace and renewables and much more.
The latest graphene composite news:
XG Sciences recently announced that it has entered into a memorandum of understanding with Sinochem Plastics and Yuyao PGS New Material Technology (an advanced materials development company focusing on the combination of graphene nanoplatelets and thermoplastic composites) to participate in developing advanced composites in China, based on its xGnP graphene nanoplatelets.
The Agreement strengthens the on-going relationship among the parties through creation of the Graphene Applications Development Center (GADC), a joint venture company between Sinochem Plastics and Yuyao PGS New Material Technology in the Sino-Italy Ningbo Ecological Park in Yuyao City. The parties recently partnered to bring new graphene enhanced anti-corrosion coatings to industrial and marine applications.
Researchers at Joseph Wang's Laboratory for Nanobioelectronics at UC San Diego demonstrated the synthesis of high-performance stretchable graphene ink using a facile, scalable, and low-cost laser induction method for the synthesis of the graphene component.
As a proof-of-concept, the researchers fabricated a stretchable micro-supercapacitor (S-MSC) demonstrating high capacitance. This is said to be the first example of using laser-induced graphene in the form of a powder preparation of graphene-based inks and subsequently for use in screen-printing of S-MSC.
Italian bicycle tire manufacturer Vittoria Industries recently announced that it is launching a new range of products employing a second generation of its graphene-filler technology. The graphene supplier is assumed to be Perpetuus Carbon, as the two companies signed a long-term supply agreement for graphene materials.
It was said that while the first-generation generally enhanced the performance of tires, the new 2.0 graphene is functionalized to improve specific tire performances, targeting metrics like speed, wet grip, durability and puncture resistance.
Rice University researchers have recently taken the idea of wearable devices that harvest energy from movement to a new level. Prof. James Tour's lab has adapted laser-induced graphene (LIG) into small, metal-free devices that generate electricity.
Putting the LIG composites in contact with other surfaces produces static electricity that can be used to power devices. This relies on the triboelectric effect, by which materials gather a charge through contact. When they are put together and then pulled apart, surface charges build up that can be channeled toward power generation.
A team of researchers from China has reported a novel strategy to 'stitch' together reduced graphene oxide (rGO) nanosheets into ultra-strong, tough, and highly conductive graphene films using only small amounts of cross-linker. They show that the bridging of long-chain π-π bonding agent between neighboring rGO nanosheets can provide substantial improvement in multiple properties including tensile strength, toughness, electrical conductivity, EMI shielding capability, and resistance to mechanical damage.
"Our graphene films not only demonstrate a record tensile strength of almost 1.1 GPa, but exceptional abilities to absorb mechanical energy, transport charge, and shield electromagnetic interference that are comparable to or even superior to graphene films annealed at much higher temperatures," says Qunfeng Cheng, a professor at Beihang University in Beijing. "Our process uses abundant natural graphite as a raw material at room temperature. This novel strategy can provide an inspiration for converting low-priced graphite powders into much higher performance macroscopic graphene films for diverse commercial uses in the future."