The Titan submersible hearing highlighted several issues related to its carbon fiber hull

Wreckage TitanThe company’s innovative carbon-fiber hull was found to have split into three separate layers, US National Transportation Safety Board engineer Donald Kramer told the Coast Guard. Hearing In the fatal explosion of the OceanGate submarine in 2023.

Although Kramer could not offer an opinion on what caused the hull to split into different layers, he testified to numerous problems with the hull, beginning with its construction in 2020.

Using samples of carbon fiber salvaged during its construction, as well as dozens of fragments recovered from the sea floor, the NTSB has produced the most complete picture to date of the experimental nature of the project. Titan‘s helm.

After TitanWhen cracks and contamination were discovered in OceanGate’s first hull following a deep dive in 2019, OceanGate switched manufacturers to replace it.

The new manufacturer, Electroimpact, used a multistage process to wrap and cure the five-inch thick hull in five separate layers. Each layer would be baked at high temperature and pressure, then flattened, an adhesive sheet added, and another layer built on top. The idea of ​​this multistage process was to reduce wrinkles in the final hull, which the company believed caused kinks in test models. Fail lower than your design depth,

However, Kramer testified that the NTSB found several anomalies in the fresh hull samples. Four of the five layers had ripples, and wrinkles that grew steadily worse with each layer. The NTSB also found that some layers had pores — gaps in the resin material — four times larger than specified in the design. It also recorded spaces between the five layers.

On Monday, Roy Thomas, a materials expert at the American Bureau of Shipping, told the hearing: “Defects such as voids, surface blisters and pores can weaken carbon fibres, and accelerate hull failure under extreme hydrostatic pressure.”

OceanGate did not create any additional test models using the new multilevel process.

The NTSB was successful in recovering several pieces of the carbon fiber hull from the ocean floor, one of which was still attached to one of the submarine’s titanium fin domes. Report Released at the same time as Kramer’s testimony, the NTSB noted that there were few, if any, full-thickness hull fragments. All visible fragments had broken apart into three shells: the innermost shell of five layers, a shell made up of the second and third layers, and another shell consisting of the fourth and fifth layers. Like peeling an onion, the hull had separated largely at the adhesive that held the layers together.