Wreck titaniumEngineer Donald Kramer of the U.S. National Transportation Safety Board told the Coast Guard that the novel carbon fiber hull was separated into three separate layers hearing to the fatal implosion of the OceanGate bathyscaphe in 2023.
Although Kramer would not comment on the cause of the hull delamination, he testified that there have been numerous issues with the hull dating back to its production in 2020.
Using carbon fiber samples preserved during construction and dozens of fragments recovered from the seabed, the NTSB provided the most complete picture yet of the craft’s experimental nature. titaniumHull.
After titaniumThe first hull that was deep-dived in 2019 was found to have cracked and delamination, so OceanGate switched manufacturers to replace the hull.
The up-to-date manufacturer, Electroimpact, used a multi-step process to wind and cure the five-inch hull in five separate layers. Each layer would be baked at high temperature and pressure, then sanded flat, with a sheet of adhesive added and another layer on top. The idea behind this multi-step process was to reduce wrinkles in the final hull, which the company said caused test models to fall compact of their design depth.
However, Kramer testified that the NTSB found several anomalies in fresh fuselage samples. There were ripples in four of the five layers, and the ripples worsened progressively from layer to layer. The NTSB also found that some layers had porosity — gaps in the resin material — four times greater than the design specification. It also noted voids between the five layers.
On Monday, Roy Thomas, a materials expert with the American Bureau of Shipping, told the hearing: “Defects such as voids, surface bubbles and porosity can weaken carbon fiber and, when exposed to extreme hydrostatic pressure, can accelerate hull failure.”
OceanGate did not produce any additional test models using the up-to-date multi-step process.
The NTSB managed to recover multiple pieces of carbon fiber hull from the seabed, one still attached to one of the submarine’s titanium end domes. report released simultaneously with Kramer’s testimony, the NTSB noted that there were few, if any, full-thickness pieces of the fuselage. All noticeable pieces had delaminate into three shells: the innermost of five layers, a shell made of the second and third layers, and another made of the fourth and fifth layers. Like an onion being peeled, the fuselage largely separated at the glue holding the layers together.
Remains titanium submarine on the seabed after implosion, captured on film by a remotely operated vehicle.Photo: Reuters