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Carbon fiber chains. Source (All Images) | Guanglian Aviation Industry Co. Ltd.

Since 2019, ’s scientific and technological innovation center for composite material forming, based in Heilongjiang Province, China, has researched and developed carbon fiber circular chains. Six years of continuous effort has led to the company’s recent milestones.

Circular chains made of carbon fiber are particularly suitable for (1) marine engineering (floating platform mooring chains), (2) shipbuilding (ultra-long anchor chains), (3) mineral mining (compact chains for scraper conveyors) and (4) deep sea buoy anchor chains or FPSO tanker mooring chains.

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Traditional industrial circular chains mainly use metal alloy steel materials, which have three disadvantages. First, its specific strength is relatively low compared to carbon fiber materials. This means that as the length of the chain increases, its own weight (self weight) will rapidly increase. For any circular chain of wire diameter specification, when the chain length exceeds the limit (usually 2,200 meters), the tension (i.e., the self weight of the entire chain) borne by the top link will exceed the break load of the link itself, causing the chain to break due to its own weight.

A second disadvantage of the metal is its poor weather resistance and salt corrosion resistance. After applying inert anti-corrosion paint on the outer surface of the circular chain, service life can reach 6-8 years. If anti-corrosion treatment is not carried out, the service life may only be 2-4 years. In general, metal circular chains are not easily used in marine engineering or humid mining industries.

Also, when high loads and high-frequency stresses are applied to the circular chain, metal creep is easily generated, causing deformation and instability failure. The lightweight, high-strength, inert anti-corrosion, high damage impedance, high fatigue resistance and bullet damage tolerance properties of carbon fiber can compensate for the shortcomings of these metal materials.

Guanglian Aviation’s innovation comprises carbon fiber and Kevlar, which are cured under high temperature and high pressure. These circular chains have lightweight, high-strength and inert anti-corrosion properties. The composite version can reach five times the length of metal chains when reaching the same weight; alternatively, the weight of the same length can be reduced by four to five times. The application prospects of ship anchor chains are broad.

Additional challenges that the company has addressed include:

• Difficulties in forming complementary interference rings
• Tensile strength exceeds that of metals of the same size
• Mechanized and automated mass production line
• Cost control of fiber-reinforced materials.

The company’s carbon fiber circular chain has passed testing by a third-party authoritative organization, and has the same wire diameter compared to equal volume metal ring chains with international standards (ISO 20438). According to the comparative test report, it was found that the fracture load of these composite circular chains exceeded 1.75 times that of metals; they can resist seawater salt corrosion for 15 years; and they have a high-frequency fatigue load resistance 60,000 times that of metals (400 cycles/minute).

After successively overcoming key technologies related to this product, Guanglian Aviation Industry Co. Ltd. has initiated its industrial application while simultaneously developing mechanized production lines to ensure product consistency and increase production capacity. Currently, planned areas for industrial application include the following aspects:

Ultra-long anchor chains exceeding 2,000 meters. The anchor chains of the U.S. Nimitz-class nuclear-powered aircraft carriers are more than 1,500 meters long, while those of other aircraft carriers are approximately 470 meters. The length of anchor chains enhances the mooring area and reduces mooring time for vessels, thereby decreasing the energy consumption of ship dynamic positioning systems (DPS).

Providing mooring chains for floating semi-submersible platforms. Current solutions for floating drilling rigs, floating wind power, and deep-sea aquaculture often adopt a steel anchor chain plus polyester rope configuration. There is a need to reduce mooring costs.

Due to the low specific strength of metal, when the length of the scraper conveyor exceeds 380 meters, the effective transportation capacity drops below 50% as a result of the compact chain’s self-weight. Thanks to its high specific strength, carbon fiber compact chains can increase their length by 4.5 times under the same total weight, while offering corrosion resistance and fatigue resistance. Alternatively, at the same length, the self-weight can be reduced by three-quarters, significantly increasing the effective payload.

Moreover, carbon fiber’s curing temperature (180°C) is far lower than that of metal (1200°C). This allows chips to be embedded during the carbon fiber forming process to provide pre-failure warnings for the compact chain.