Led by Jinwen Zhang, a professor in the School of Mechanical and Materials Engineering, researchers developed a recyclable material that is as strong as commonly used carbon fibre composites and can also be broken down in very hot water within a pressure vessel. The new material could be easily substituted into current manufacturing processes. The research team, including scientists from the Department of Energy’s Pacific Northwest National Laboratory, report on their work in the journal, Macromolecular Rapid Communications.

Carbon fibre reinforced composites are increasingly popular in many industries because they are light and strong. They serve as an energy-saving, lighter alternative to metals, especially in the aviation and automotive industries. They are, however, difficult to break down or recycle, and disposing of them has become of increasing concern. Early versions of modern wind turbines made of composites from the 1990s, for instance, are now reaching the end of their lifetimes, creating a significant challenge for disposal.

While thermoplastics, the type of plastic used in milk bottles, can be melted and easily re-used, the carbon fibre composites are made from thermosets. These types of plastics are cured and can’t easily be undone and returned to their original materials.

Zhang’s team developed a composite material that uses an epoxy vitrimer as an alternative to the traditional epoxy resin. The material is hard and durable like an epoxy thermoset but can also show self-healing and malleable properties at high temperatures like a thermoplastic.

When they used their epoxy vitrimer in the composite material, they were able to degrade their material in pressurised, distilled water beginning at 160 degrees Celsius, dissolving it into valuable carbon fibre and other compounds, which can then be re-used. The recycled carbon fibre was comparable in strength to brand new carbon fibre. When they raised the temperature to 180 degrees, the material completely dissolved. The epoxy vitrimer that they developed could easily be substituted into the manufacturing process.

There is no need to change the chemistry of the process – it is just a slight modification of using the epoxy vitrimer instead of traditional epoxy. The technology is simply and readily applicable.

While the new recyclable material could be easily adopted by manufacturers, Zhang is also continuing work to improve the recycling of composites that are currently in the market. In recent years, he developed an environmentally friendly method to break down the material in a liquid or ethanol medium. Earlier this year, he received a $1.2 million Department of Energy grant for the up-cycling of the composites waste.

The research was supported through grants from the Department of Energy’s Office of Energy Efficiency & Renewable Energy and the Joint Center for Aerospace Technology Innovation.

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CFRP, a composite material that contains carbon fibre, which is about four times lighter than steel yet 10 times stronger, is widely used in the aerospace, automotive, shipbuilding, and sports equipment industries. Structurally, CFRP is made up of carbon fibre and epoxy resin, which serve functions in this composite material similar to the respective roles that reinforcing rods and cement play in concrete structures. To achieve mechanical rigidity, the binding of carbon fibre and epoxy resin in CFRP must be strong. Moreover, CFRP must be fire-safe, as it is used for purposes closely related to everyday life, e.g., use as a construction material. To induce these traits in CFRP, sometimes it is synthesized with additives.

Due to its susceptibility to heat, CFRP had been made fire-safe by adding a halogen flame-retardant. However, the use of halogen in CFRP was banned worldwide, because it generates toxic substances when incinerated for recycling. As such, the task at hand was to make CFRP flame-retardant with the use of non-toxic, safe material.

We have created a composite material with an expanded range of application that is a dramatic improvement over conventional carbon fibre-reinforced plastic in terms of flame-retardancy, mechanical rigidity, and recyclability.

Head researcher Dr. Jung

Jung Yong-chae, head researcher at KIST’s Institute of Advanced Composite Materials, sought to improve the mechanical rigidity and flame-retardance of CFRP with tannic acid, an eco-friendly substance. Tannic acid characteristically bonds strongly with carbon fibre. It also turns into charcoal when burned. Charred tannic acid functions as a barrier that blocks the inflow of external oxygen. By manufacturing epoxy resin from tannic acid and mixing it into carbon fibre, the KIST research team successfully developed a CFRP that is strong and flame-retardant.

Unlike conventional epoxy resin that is vulnerable to heat, epoxy resin made from tannic acid is flame-retardant and needs no additives. This means that the toxic substances generated when incinerating CFRP for recycling would no longer be a problem. Also, because conventional CFRP when burned decreased the performance of its epoxy resin, precluding complete recycling, the research team came up with a new recycling method.

By dissolving CFRP in water in a supercritical fluid state—i.e., temperature and pressure over a set level—over 99% of the CFRP could be recovered without reduced carbon fibre performance. It was also found that epoxy resin when dissolved produced a substance called “carbon dots,” which can be used as an electronic material (Optronics, Sensing, Bioimaging etc.). Unlike the method of recycling by incineration, which burns up epoxy resin leaving only the incomplete carbon fibre to be recycled, this new method of recycling enables the recycling of all components of a composite material.

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Composite laminates used in Aerospace applications are typically made of layers of carbon fibres with varying orientations embedded in epoxy. For example, the composite laminate can be composed of a carbon/epoxy layer with the fibres oriented in the 90-degree direction sandwiched between two 0-degree plies. The fibres are each about seven microns in diameter, or about one-seventh of the thickness of a human hair.

“We know from experiments that cracks propagate transversely across the 90-degree plane, then stop when they reach the interfaces with the 0-degree plies. So we developed a method that allows us to simulate hundreds of fibres in a realistic system and study how the failure response is affected if we change the location of a single fibre or of many fibres, or the strength of the interface,” said Philippe Geubelle, a professor in the Department of Aerospace Engineering.

In this new method, optical micrographs are taken of the 90-degree ply and the location of all of the fibers are extracted to construct a realistic computational model of the ply. Similar studies have been limited to tens of fibers.

“With the special finite element method we have developed to simulate the transverse cracking of the 90-degree ply, we can simulate hundreds of fibres,” Geubelle said. “The most we’ve done so far is close to 3,000 fibres.”

“Because the crack propagates primarily along the fibre-matrix interfaces, our model emphasizes the cohesive failure of these interfaces,” he said. “In addition, we have developed the ability to extract efficiently the sensitivity of the failure event with respect to the properties of the microstructure including the location and size of the fibres, and the failure properties of the fibre-matrix interfaces. We can also compute the sensitivity of the failure event with respect to the parameters (average, standard deviation, etc.) that define the distribution of these microstructural parameters.”

“Of course, you could get these sensitivities experimentally, with every conceivable variation, to see what the effect is on the failure event,” Geubelle said. “To do this numerically is much more efficient.”

Of course, you could get these sensitivities experimentally, with every conceivable variation, to see what the effect is on the failure event,” Geubelle said. “To do this numerically is much more efficient.

The study, “Transverse Failure of Unidirectional Composites: Sensitivity to Interfacial Properties,” written by  S. Zacek, D. Brandyberry, A. Klepacki, C. Montgomery, M. Shakiba, M. Rossol, A. Naja, X. Zhang, N. Sottos, P. Geubelle, C. Przybyla, and G. Jefferson appears in Integrated Computational Materials Engineering.

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Part of the Air Force 2030 Science and Technology strategy includes the deployment of low-cost Unmanned Aerial Systems in mass to assist in future near-peer engagements. In order to realise this vision, new manufacturing strategies need to be identified which can support the rapid manufacturing of high-quality aerospace components at costs that are lower than what is currently available using legacy manufacturing processes.

The Air Force Research Laboratory’s Manufacturing and Industrial Technologies Division and the contractor team of Cornerstone Research Group, A&P Technology and Spintech LLC, conducted research to quantify the benefits of replacing legacy manufacturing processes with novel processes for the fabrication of an 11-foot long, S-shaped engine inlet duct.

The legacy fabrication process for the inlet duct consists of composite material pre-impregnated with a synthetic resin, applied by hand, to a multi-piece steel mandrel. The mandrel is packaged and placed in an autoclave for processing. An autoclave is essentially a heated pressure vessel which supplies heat to activate resin curing and pressure to ensure there is minimal absorbency in the fully cured composite part.

The approach replaces the hand-applied composite prepreg with an automated over-braid process which applies dry fibre to a mandrel. The very heavy multi-piece steel mandrel was replaced with a light-weight single-piece shape-memory polymer mandrel and the dry braided carbon fibre was processed with low-cost epoxy resin using a vacuum-assisted resin transfer moulding process.

One of the primary goals of this program is to understand the part cost and production time benefits from introducing the new tooling and processing solutions.

The team completed element analysis finalisation of the over-braid architecture, fabrication of a shape memory polymer-forming tool and construction of the SMP mandrel that will serve as the tool during the preform over-braid process.

We believe that the introduction of a reusable shape memory polymer mandrel together with the automated over-braid process and an oven based VARTM composite cure will lead to significant cost and cycle time reductions

 Mr. Craig Neslen, manufacturing lead for the Low Cost Attritable Aircraft Technology Initiative

Because of inlet duct geometrical complexity, multiple iterations were necessary to optimise the over-braid machine settings and thus minimise composite material wrinkling. A total of four inlet ducts will be fabricated and legacy part cost and production time will be compared to the new design.

The final inlet duct will be delivered to the government for further integration into the Aerospace System’s Directorate’s complementary airframe design and manufacturing program. Personnel at the Aerospace Vehicles Division will conduct static ground testing of the integrated braided fuselage and inlet duct structure.

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Under terms of the agreement, Huntsman will pay $300 million, subject to customary closing adjustments, in an all-cash transaction funded from available liquidity.  Based on full-year 2019, the purchase price represents an adjusted EBITDA multiple of approximately 10 times, or between approximately 7 to 8 times pro forma for synergies, the lower multiple end being dependent upon normal growth market conditions.  The transaction is expected to close around midyear of 2020.

Founded in 1982, the company manufacture speciality products for high-performance thermoset systems including epoxy resins, reactive liquid polymers, epoxy-functional reactive modifiers, elastomer modified epoxy resins and curing agents, catalysts and accelerators.

In these uncertain times, our financial strength will allow us to keep looking for these types of acquisitions, while at the same time maintain a conservative balance sheet and opportunistically repurchase shares

Peter Huntsman, Chairman, President and CEO

With manufacturing facilities in Akron, Ohio, and Maple Shade, New Jersey CVC Thermoset Specialties has annual revenues of approximately $115 million. Under terms of the agreement, Huntsman will pay $300 million, subject to customary closing adjustments, in an all-cash transaction funded from available liquidity. Based on full-year 2019, the purchase price represents an adjusted EBITDA multiple of approximately 10 times, or between approximately 7 to 8 times pro forma for synergies, the lower multiple ends being dependent upon normal growth market conditions.  The transaction is expected to close around midyear of 2020.

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CMF is a foam that consists of hollow, metallic spheres – made of materials such as stainless steel or titanium – embedded in a metallic matrix made of steel, aluminium or metallic alloys. For this study, the researchers used steel-steel CMF, meaning that both the spheres and the matrix were made of steel. Previous work has found the metal foam is remarkably tough: it can withstand .50 calibre rounds, resist high temperatures, and block blast pressure from high explosive incendiary rounds.

The infused CMF is made by immersing the steel-steel CMF in a hydrophobic epoxy resin and using vacuum forces to pull the resin into both the hollow spheres and into much smaller pores found in the steel matrix itself. This results in about 88 per cent of the CMF’s pores being filled with epoxy resin.

The researchers then tested both infused CMF and aerospace-grade aluminium to see how they performed in three areas: contact angle, which determines how quickly water streams off of a material; insect adhesion, or how well bug parts stuck to the material; and particle wear, or how well the material stands up to erosion. All of these factors affect the performance of an aircraft wing’s leading edge.

The contact angle is a measure of how well water beads up on a surface. The lower a material’s contact angle, the more the water clings to the surface. This is relevant for aircraft wings because water buildup on a wing can affect aircraft performance. The researchers found that infused CMF had a contact angle of 130% higher than aluminium – a significant improvement.

Insect adhesion is measured in two ways: by the maximum height of insect residue that builds upon the material, and by the amount of area covered by insect residue on a material’s surface. Again, infused CMF outperformed aluminium – by 60% in regard to maximum height, and by 30% in regard to the surface area covered.

The researchers also conducted grit blast experiments to simulate the erosion caused by the wear and tear that occurs over time when aircraft wings are in use. The researchers found that, while grit blast did increase surface roughness for infused CMF, it still fared better than aluminium. For example, at its worst, infused CMF still had a contact angle 50 per cent higher than that of aluminium.

In other words, the infused CMF retained its properties through erosion and wear, which indicates that it would give leading-edge wing components a longer lifetime – and reduce the costs associated with maintenance and replacement.

Aluminium is currently the material of choice for making the leading edge of fixed-wing and rotary-wing aircraft wings. Our results suggest that infused CMF may be a valuable replacement, offering better performance at the same weight.

The paper, “Polymer Infused Composite Metal Foam as a Potential Aircraft Leading Edge Material,” is published in the journal Applied Surface Science. The first author of the paper is Jacob Marx, a Ph.D. student at NC State. The paper was co-authored by Samuel Robbins, Zane Grady, Frank Palmieri and Christopher J. Wohl of NASA Langley Research Center.

The research was done with support from NASA, under grant number NNX17AD67A.

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NASA’s CubeSat Launch initiative (CSLI) provides opportunities for small satellite payloads to fly on rockets planned for upcoming launches. These CubeSats are flown as auxiliary payloads on previously planned missions.

Small satellites are playing an increasingly larger role in exploration, technology demonstration, scientific research and educational investigations at NASA. These miniature satellites provide a low-cost platform for NASA missions, including planetary space exploration. They also allow an inexpensive means to engage students in all phases of satellite development, operation and exploitation through real-world, hands-on research and development experience on NASA-funded ride share launch opportunities.

The first ever carbon-nanotube resin mirror could prove central to creating a low-cost space telescope for a range of CubeSat scientific investigations.

Unlike most telescope mirrors made of glass or aluminium, this particular optic is made of carbon nanotubes embedded in an epoxy resin. Sub-micron-size, cylindrically shaped, carbon nanotubes exhibit extraordinary strength and unique electrical properties, and are efficient conductors of heat. Owing to these unusual properties, the material is valuable to nanotechnology, electronics, optics, and other fields of materials science, and, as a consequence, are being used as additives in various structural materials.

The use of a carbon-nanotube optic in a CubeSat telescope offers a number of advantages. In addition to being lightweight, highly stable, and easily reproducible, carbon-nanotube mirrors do not require polishing — a time-consuming and often times expensive process typically required to assure a smooth, perfectly shaped mirror.

To make a mirror, technicians simply pour the mixture of epoxy and carbon nanotubes into a mandrel or mould fashioned to meet a particular optical prescription. They then heat the mould to cure and harden the epoxy. Once set, the mirror then is coated with a reflective material of aluminium and silicon dioxide.

Many of the mirror segments in these telescopes are identical and can therefore be produced using a single mandrel. Carbon-nanotube mirrors can also be made into ‘smart optics’. To maintain a single perfect focus in the Keck telescopes, for example, each mirror segment has several externally mounted actuators that deform the mirrors into the specific shapes required at different telescope orientations.

This technology can potentially enable very large-area technically active optics in space, and can address everything from astronomy and Earth observing to deep-space communications.

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The new ZNT-boost product by Zyvex Technologies adds increased toughness without compromising on strength and stiffness and unlike most toughening systems Zyvex say this product doesn’t force you to compromise on one property to increase another. ZNT-boost often increases the toughness of the composite up to 100% while increasing the stiffness and strength up to 30%.

ZNT-boost is easy to use with standard composite processing systems and is likely the simplest way to leverage the benefits of carbon nanomaterials. No process changes need to be made and no changes are required in your catalysts or curing agents when using ZNT-boost.

In deploying the first commercial adoption of ZNT-boost, Zyvex Technologies worked closely with Composites Universal Group (CUG) located in Scappoose, Oregon. CUG fabricates components and assemblies for customers needing the high strength and low-weight properties of advanced composites materials.

ZNT-boost is available in two forms: liquid and dry flake (powder) for most epoxy-based composite applications that include prepreg, VARTM, infusions, and hand layup. ZNT-boost works with most forms of epoxy, vinyl esters and polyesters.

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The SKYe SH09 is a single engine helicopter and made its first flight in October 2014. The SKYe SH09 features a full composite airframe as well as all-composite main and tail rotor blades; it is equipped with glass cockpit, avionics systems and the Honeywell HTS–900–2 turbine engine.

With a cruise speed of 270 km/h (145 knots) it is not only one of the fastest single engine light helicopter in its class, but also offers very long-range – in excess of 800km (430 nautical miles) with standard fuel tanks.

TenCate will supply the Swiss helicopter maker an Epoxy resin that’s known for its toughness and ability to be used in out of autoclave fabrication conditions. Frank Meurs, Group Director of TenCate Advanced Composites EMEA, said;

We are very pleased to have been chosen by Marenco Swisshelicopter for the supply of our system based materials for this new and important project. This complements our global growth strategy in thermoset materials, not only from our facilities in the United States of America, but also from our facility in Langley Mill, United Kingdom.

The SKYe SH09 is scheduled to go into production within the next 12 to 16 months.

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Along with the recent investment, two new members have joined Connora’s advisory board; Andre Genton, former President of Huntsman Advanced Materials, and Brendan Iribe, a successful entrepreneur known recently for the acquisition of Oculus by Facebook.

The epoxy technology is a green chemistry platform that provides an efficient method for making and recycling composite waste materials and products. The company is hoping that their technology will be picked up by the automotive and aerospace industries, where the trend is to make lighter, stronger, and more energy efficient vehicles through the use of advanced composite materials.

https://www.youtube.com/watch?v=rA9vejjsnmE

Carbon fibre parts are often made in high volumes, with sometimes 20–40% of the raw materials going to waste. Since traditional thermoset plastics are not optimised for recyclability, current composite waste is intractable and often disposed of in landfill or by burning.

The company say that this investment shows that the technology will have an economic value for manufacturers just as compelling as the obvious environmental benefits. Reclaiming expensive carbon fibre, from manufacturing waste in a near virgin state, and enabling OEMs to put it back into their products will help lower their costs over time.

The European Union Directive for End of Life Vehicles (ELV) is already pushing the limits for composite materials if they are to have a mainstream role in that industry. Under the current provisions of the ELV Directive targeted for 2015, the proportions of ELV material required for re-use and recycling are 85% by weight, while that for re-use and recovery is 95%. The 10% difference being the amount allowed for incineration and energy recovery.

Connora’s Recyclamine Technology enables carbon fibre composites to more readily qualify as a recyclable material. Connora is currently in discussions with several auto and aerospace companies to develop a specific Recyclamine system for use in high-pressure resin transfer moulding processes (HP-RTM), suitable to the high-volume manufacturing methods being adopted by auto and aerospace manufacturers today.

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