Both China and the US plan to deploy numerous underwater drones in key maritime areas such as the Taiwan Strait and the South China Sea. Recently, a US unmanned underwater vehicle was salvaged by the Chinese coast guard, highlighting the intensifying struggle. Foreign media suggests that in any potential conflict, the performance and quantity of underwater drones will be decisive. According to a report last month by the Washington think tank Center for a New American Security, the situation in the Taiwan Strait will differ significantly from the conflict in Ukraine, as underwater drones are harder to destroy or disrupt compared to drones.
The South China Morning Post reported on July 11 that Chinese scientists have developed a super carbon fiber hull capable of mass-producing high-performance underwater drones. These drones are not only suitable for shallow waters but can easily dive to depths of 6,000 meters (19,700 feet). This figure is a conservative estimate, with theoretical values suggesting the potential for even deeper dives.
Last month, a project team led by senior engineer Guo Yuqi from the Harbin Fiberglass Research Institute published a peer-reviewed paper in the Chinese academic journal *Fiber Composites*. The paper stated, “Current deep-sea submersibles typically use pressure-resistant structures made of alloy steel or titanium alloy. Due to their high density, these materials account for a significant portion of the submersible’s total weight, limiting their payload capacity.”
He and his colleagues wrote, “In today’s era of rapid national development and high demand for deep diving and high payloads, carbon fiber materials are widely used in manned and unmanned submersible pressure-resistant structures due to their low density, high strength, high modulus, fatigue resistance, corrosion resistance, and flexible design.”
The Harbin Fiberglass Research Institute, a spin-off from Harbin Institute of Technology (HIT), is considered the cradle of fiberglass in China. HIT, recognized for its significant contributions to national defense, is currently under US sanctions. The institute and HIT now operate under a collaborative model. The Harbin Fiberglass Research Institute has developed many pioneering technologies, often leading within China.
In the West, carbon fiber is considered unsuitable for the submarine industry. The world’s first carbon fiber manned submersible, the Titan, operated by the private US company OceanGate, suffered catastrophic failure under immense water pressure last June at a depth of 4,000 meters, resulting in the loss of all five onboard. Many industry experts attribute this tragedy to carbon fiber’s vulnerability underwater: high pressure can cause water to penetrate the gaps between fibers, and repeated diving can lead to hull cracking and deformation. Western experts believe that the inherent properties of carbon fiber make it unsuitable for the submarine industry, but Chinese scientists aim to challenge this belief.
The wall thickness of the Chinese-made carbon fiber pressure hull is about 3 centimeters, only a quarter of that of the Titan. According to Professor Guo’s team, laboratory tests showed that this hull could easily withstand 77 megapascals of water pressure, more than double the pressure resistance tested by the University of Washington for the Titan. Guo estimates that a chamber made of this carbon fiber material can withstand pressures of up to 90 megapascals, enabling submersion to depths of 9,000 meters. However, for safety, the operational depth is set at 6,000 meters, equivalent to 60 megapascals of pressure. While the US equivalent failed at 4,000 meters, the Chinese product is expected to safely reach 6,000 meters, with a potential limit of 9,000 meters, representing a significant lead.
The outer layer of the carbon fiber pressure hull is a 1-millimeter-thick waterproof coating, providing protection against leakage, damage, interface delamination, cracking, or other issues during normal use. Guo’s team stated that it could withstand a certain degree of impact, scratches, and other challenges without malfunction or damage.
Guo’s team conducted high-pressure and sealing system tests on the exterior of the pressure hull, with excellent results. To withstand the alternating pressures of 0-6,000 meters of seawater, designers also considered fatigue issues at the connections between the carbon fiber hull and titanium alloy, as well as internal pressure and temperature changes.
They stated in their paper, “It can withstand over 2,000 alternating cycles.” Guo’s team also developed a carbon fiber hull for unmanned underwater vehicles operating within 200 meters, with a thickness of only 3 millimeters and a diameter of 1 meter, suitable for low-cost operations in shallow waters.
Underwater submersibles are indispensable for safeguarding national maritime rights and resource security. Their technological level to some extent represents national defense capabilities and technological strength. As China has already mastered shallow-water submarine communication technology, the large-scale use of underwater submarine drones may be led by China.
Additionally, last year, China’s carbon fiber production nearly reached half of the global output. With many new production lines under construction, some industry experts estimate that China’s capacity could significantly increase in the coming years, further reducing the cost of carbon fiber.
Chinese-produced carbon fiber is primarily used in sports and recreational products. In the Chinese market, the price of a carbon fiber bicycle has dropped to just over 3,000 yuan, equivalent to about 410 US dollars, one-tenth of the price a few years ago.
