Titan submersible hearings highlight multiple problems with its carbon fiber hull

Remains of the shipwreck TitanThe ship’s innovative carbon fiber hull was found separated into three distinct layers, U.S. National Transportation Safety Board engineer Donald Kramer told a Coast Guardsman. audience in the fatal implosion of the OceanGate submersible in 2023.

While Kramer did not offer an opinion on what caused the helmet to delaminate into separate layers, he did testify about multiple problems with the helmet, beginning with its manufacturing in 2020.

Using carbon fiber samples salvaged from its construction, as well as dozens of pieces recovered from the seafloor, the NTSB gave the most complete picture to date of the experimental nature of the Titanhelmet of

After the TitanIn 2019, after deep dives, the first hull was found to have a crack and delamination, so OceanGate changed manufacturers to replace it.

The new manufacturer, Electroimpact, used a multi-step process to roll and cure the five-inch-thick helmet in five separate layers. Each layer would be baked at high temperature and pressure before being flattened, an adhesive backing added, and another layer built on top. The idea of ​​this multi-step process was to reduce wrinkles in the final helmet that the company said had caused test models to fail before reaching design depths.

However, Kramer testified that the NTSB found several anomalies in the fresh hull samples. There were ripples in four of the five layers and wrinkles that progressively worsened from layer to layer. The NTSB also found that some layers had porosity (voids in the resin material) four times larger than specified in the design. It also recorded voids between the five layers.

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

OceanGate did not perform any additional test models using the new multi-stage process.

The NTSB was able to recover many pieces of the carbon fiber hull from the seabed, one of which was still attached to one of the titanium domes at the end of the submersible. report In a report issued simultaneously with Kramer’s testimony, the NTSB noted that there were few, if any, full-thickness hull pieces. All visible pieces had delami- nated into three layers: the innermost of five layers, a layer made up of the second and third layers, and another made up of the fourth and fifth layers. Like an onion being peeled, the hull had largely separated into the adhesive that held the layers together.