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A team of researchers at Cukurova University, a research university in Adana, Turkey, announce several ongoing patents that are said to provide a simple, more cost-effective way to create a channel or micro-channel of any diameter in carbon fiber composites for self-healing and thermal management, without the need to integrate pipes for circulating gases or liquids.

Cukurava University has been conducting R&D development studies on carbon fiber-reinforced polymer (CFRP), FRP and sandwich composites since 2016. Damage like crack propagation, fiber shedding and surface abrasion — something that naturally occurs over long-term service of FRP components and structures in any sector due to the material’s subjection to complex variable loads in harsh conditions — led university researchers to explore self-healing mechanisms. This, of course, requires obtaining microvascular channels within CFRP or FRP, including at a large scale.

Many methods have been invented and tested for microvascular channel creation in composite structures, including electrostatic discharge, melt- and electrospinning, soft lithography, 3D printed scaffolds and others. These current techniques, however, are generally impractical for large-scale production, in addition to having their own downsides and challenges.

This was a key driver for Cukurova University researchers to achieve a novel method of obtaining vascular and microvascular channels that is suitable for both small and large-scale products, as well as creating these channels in a shorter period of time. It is achieved by placing or positioning the monofilaments used for channel formation in a suitable sequence in the fiber fabric or filament and integrating them into the structure to form interconnected channels. This feature was also the core idea of the last two patents and, according to researcher Prof. Dr. Necdet Geren, will optimize mass production.

The following projects, supported by the Scientific Research Projects Coordination Unit (BAP) of Çukurova University and the Research Universities Support Programme (ADEP), respectively, are described in more detail via the abstracts below:

Composite battery enclosure with thermal management and self-healing (repairing) features (PCT/TR2024/050272)

This invention is related to a composite battery enclosure used in electric vehicles (EVs) with self-healing properties in case of any damage and a thermal management system used on the enclosure. The battery box, which fulfills more than one function, consists of fiber-reinforced polymer composite plates and contains integrated channels of various diameters to enable self-healing (repair) in case of any mechanical damage and thermal management. Thus, a smart material system is created by providing self-repair (improvement) of the battery box with the channels located in the high-strength composite structure. 

Battery enclosures are used in various industries related to EVs of any class — such as aerospace, marine, automotive and rail systems — and the battery packaging sector.

Production method for self-repairing polymer matrix, fiber-reinforced composite pressure vessel tank and wind turbine blades (PCT/TR2024/050885)

This patent relates to a self-healing/repairing production method for high-pressure, fluid-carrying vessels/tanks (including cryogenic), as well as composite wind turbine blades, in the event of damage. Tanks fulfill multiple functions such as sealing and withstanding high pressure. The cryogenic liquid/gas storage tank made of high-strength fiber-reinforced composite material developed within the scope of this patent contains self-healing channels of different geometries and dimensions for self-healing (repair) in case of any mechanical damage. These channels also contain a repairing agent (resin) that can be found in liquid form at cryogenic temperatures and/or between -80°C and 148°C. Successive channels contain resin with self-healing agent and hardening agent/activator material.

In another implementation of the patented technique, the hardening agent/activator material is mixed as particles into the matrix material forming the composite and distributed into the matrix. In this application, all channels contain a repairing agent (resin) that can exist in liquid form between -80°C and 148°C. Thus, cryogenic and semi-cryogenic chemical resins in the micro-channels within the high-strength composite structure enable the tank to be repaired spontaneously. 

In this respect, this patent relates to composite tank sectors — such as liquefied natural gas (LNG), liquefied propane, nitrogen, hydrogen and similar gases and liquids — in the transport and storage of these gases and liquids by land and aircraft tankers, including tanker ships, and hydrogen fuel storage belonging to any class of vehicles (sectors such as space-air, rocket, ship, automotive, rail systems). For this reason, it is related to the production and manufacturer of all kinds of tanks containing self-repairing properties, including but not limited to the above-mentioned industries. It is also suitable for seabed and subsea, commercial and military subsea, and surface vehicles exposed to external pressure.

Similar application can be made to composite wind turbine blades. Integrated channels were formed containing a fluid repairing resin in the case of damage.

Ultimately, this self-repairing feature can reduce safety risks when transporting or storing flammable and explosive gases/liquids and can eliminate the need for mechanical repair.

Weaving of filament yarns to form microvascular channels in fiber fabric for fiber-reinforced polymer composite production (PCT/TR2023/051362)

The self-healing method can also be related to weaving (or placing) filaments to create microvascular channels in fiber-reinforced polymer composites at regular intervals during the fiber fabric weaving process. This method is said to reduce production cost of fiber-based industrial composites containing microvascular channels without decreasing the material’s strength.

There are several application areas. One is biomedical applications, such as devices (lab on a chip) that integrate one or several laboratory functions on a single integrated circuit — from millimeters to a few square centimeters — to achieve automation and high-throughput scanning. Other applications include automotive, technical textile weaving, a range of critically important composites equipment and parts, wearable technical products, electric batteries and more.

High-strength fiber used in air and space vehicles containing monofilament yarn interlayers for composite applications (PCT/TR2023/051491)

This invention relates to interlayers consisting of polyamide/nylon and derivative filament/monofilament yarns fabricated together with high-strength fibers to create the necessary microvascular channels in critical composite parts used in air and space vehicles. It also appeals to areas where composite structures can be used for the same purpose by arranging (polyamide/nylon polyamide, nylon derivative and so on) monofilaments as additional intermediate layers in solid/semi-solid/fluid states into layer/mesh/plate structures.

These filaments and/or layers, which are integrated into the weaving or laid on prepreg fibers after weaving, can be easily removed after composites production. Thus, micro-channels are created in the composite structure through which all kinds of fluids — including self-healing agents — can be permanently injected. Moreover, these micro-channels are suitable for any gas or liquid fluid flow.