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The remains of the Titan submersible’s advanced carbon fiber hull were discovered in three separate layers, according to Donald Kramer, an engineer with the U.S. National Transportation Safety Board (NTSB). He presented this information during a Coast Guard hearing investigating the tragic implosion of the OceanGate submersible in 2023.
Kramer refrained from speculating on what might have caused the hull to separate but highlighted several issues with the hull that began with its production in 2020. The NTSB utilized both carbon fiber samples from the submersible’s construction and numerous fragments recovered from the ocean floor to provide a comprehensive overview of the Titan’s experimental hull design.
Following the discovery of a crack and delamination in the Titan’s initial hull after deep dives in 2019, OceanGate switched manufacturers. The new company, Electroimpact, employed a complex, multistage process to create the five-inch-thick hull using five individual layers. Each layer was baked under high temperature and pressure before it was smoothed, had an adhesive applied, and another layer was added. This method aimed to minimize the wrinkling that led to failures in previous test models.
However, Kramer noted several irregularities in the newly manufactured hull samples. Four of the five layers displayed waviness, and the wrinkles worsened from one layer to the next. Additionally, the NTSB identified that some layers exhibited porosity, with gaps in the resin material exceeding the design specifications by four times. Voids were also present between the layers.
Roy Thomas, a materials expert from the American Bureau of Shipping, testified at the hearing that defects such as voids, surface blisters, and porosity could weaken the carbon fiber. He warned that under significant hydrostatic pressure, these defects could hasten the hull’s failure.
Despite the identified manufacturing defects, OceanGate did not produce any further test models using the new process. The NTSB successfully retrieved numerous pieces of the carbon fiber hull from the seabed, one of which was still connected to one of the submersible’s titanium end domes. In a report released simultaneously with Kramer’s testimony, the NTSB mentioned the scarcity of complete hull pieces, noting that most visible fragments had delaminated into three sections: the innermost layer, a combination of the second and third layers, and another consisting of the fourth and fifth layers. Much like peeling an onion, the hull had separated mainly along the adhesive that bonded the layers together.
Photograph: Reuters
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