In the summer of 2023, the deep-sea submersible "Titan" of OceanGate, a marine tourism company, imploded on the way to the wreck of the Titanic, killing all five passengers on board. While there may have been a number of issues that led to the Titan deep-sea submersible's disaster, its carbon fiber hull attracted particular attention, not least since it was one of the first submersibles to use this material.
According to a recent study from the University of Houston in the United States, by using computer simulations to analyze the buckling strength of a thin-walled cylinder with certain defects (a structure almost identical to that of the Titan), it was found that the "microbuckling" of carbon fibers could cause the hull to lose considerable strength.
Review of the implosion of the "Titan" submersible
In the article "A Comprehensive Inventory of the Eight "Blockbuster" Events in the Field of High-performance Carbon Fiber and Composite Materials at Home and Abroad in 2023" written in this issue, a detailed inventory of the major events of global carbon fiber composite materials in 2023 is listed, among which the Titan "Deep-sea Submersible Implosion Accident" using carbon fiber composite materials is among them (read [Annual Focus] A comprehensive inventory of the eight "blockbuster" events in the field of high-performance carbon fiber and composite materials at home and abroad in 2023).
On June 18, OceanGate founder and CEO Stockton Rush, 77-year-old former French naval officer Paul Henri Najlet, 58-year-old British billionaire and adventurer Hamish Hardin (who flew into space on June 4, 2022 on Jeff Bezos' Blue Origin rocket), and Shahzada, a 48-year-old Pakistani businessman Five passengers, including Dawood (a member of the board of directors of the search for extraterrestrial intelligence) and his son Suleiman, watched the historic Titanic wreck aboard a deep-sea submersible.
The deep-sea submersible, named "Titan", went missing about 1 hour and 45 minutes after departure, and after several days of intensive searching, the U.S. Coast Guard found the debris of the missing submarine just 1,600 feet from the bow of the Titanic, and concluded that the ship had imploded and all the people on board were killed.
The wreckage of the Titan submersible recovered from the seabed near the wreck of the Titanic
A flurry of speculation ensued, including numerous previous complaints about the company, about what might have gone wrong when the Titan descended 12,500 feet below sea level, far more than any diver could reach. Many were quick to point the finger at the carbon fiber hull of the Titan, the first submersible to use this material.
Director and deep-sea explorer James Cameron told The Wall Street Journal at the time: "I never believed that the technology of winding carbon fiber around a cylindrical hull would work. I think that's a terrible idea. ”
The U.S. Coast Guard searches for submersibles from the Canadian research vessel Polar Prince
Latest research progress
Now, a new study from the University of Houston in the United States can explain exactly why carbon fiber caused the Titan deep submersible disaster. In a new paper published in the Proceedings of the National Academy of Sciences (PNAS), scientists analyze how thin-walled cylinders, especially elongated cylinders, succumb to ocean pressures.
While the researchers did not directly study the Titan in their paper, the doomed submersible would be an example of such a vessel explored in the paper, which uses computer simulations to develop equations that predict the buckling strength of the shell based on certain defects.
This paper points out that local deformation and random shape defects are the significant characteristics of buckling instability of thin-walled load-bearing structures. However, it is generally accepted that the complex interactions of these defective structures with mechanical loads are not fully understood, as evidenced by the catastrophic failures caused by buckling, which are still ongoing.
In the case of the Titan submersible, this was a tragedy of slow development, as its carbon fiber hull was subjected to several load pressures during its multiple (nearly a dozen) descent to the Titanic. Carbon fiber is known for its light weight and high strength, however, when subjected to a strong force, such as the pressure of the deep sea area where the Titanic is located, carbon fiber can weaken over time, causing each subsequent descent to be more dangerous than the last.
Roberto Ballarini, a collaborator on the study at the University of Houston, said in a press statement: "Fibers in carbon fiber composites are known to be prone to microbuckling under compressive loads, and they may detach from the surrounding matrix. If the Titan's hull had been subjected to extreme compressive pressure during the dive caused this damage, its stiffness and strength would have been significantly reduced, which, combined with the inevitable geometric defects in the manufacturing process, could have contributed to its buckling-induced implosion. ”
While the tragedy of the Titan is likely to have been avoided because, according to reports, it has taken cost- and time-saving measures due to the ship's design flaws, its example could drive future submersible design, especially after federal investigators publish their findings in the coming months.