Remains of Titan’s innovative carbon fiber hull were found separated into three distinct layers, National Transportation Safety Board engineer Donald Kramer said at a Coast Guard hearing on the deadly 2023 Ocean Gate submersible explosion.
Kramer did not offer an opinion on what caused the hull to delaminate, but testified that there had been multiple issues with the hull since it was first built in 2020.
Using carbon fiber samples preserved from construction, as well as dozens of pieces recovered from the ocean floor, the NTSB has provided the most complete information yet about the experimental nature of Titan’s hull.
After cracks and delamination were found in Titan’s original hull following a deep-sea dive in 2019, Ocean Gate replaced it with a new manufacturer.
The new manufacturer, Electroimpact, used a multi-step process to wrap and cure the 5-inch-thick hull in five separate layers. Each layer was baked at high temperature and pressure, then sanded flat, a sheet of adhesive was added, and another layer was built on top. The purpose of this multi-step process was to reduce wrinkling in the final hull, which was thought to be causing test models to not reach their design depth.
But Kramer testified that the NTSB found several anomalies in the new hull samples. Four of the five layers had rippling, and the wrinkling got progressively more severe with each layer. The NTSB also found that some layers had porosity (gaps in the resin material) that was four times greater than specified in the design. It also noted voids between the five layers.
“Defects such as voids, surface blisters and porosity can weaken the carbon fibre and accelerate the failure of the hull under extreme hydrostatic pressure,” Roy Thomas, a materials expert at the American Bureau of Shipping, said at the hearing on Monday.
OceanGate did not create additional test models using its new multi-step process.
The NTSB was able to recover numerous pieces of the carbon fiber hull from the ocean floor, one of which was still attached to one of the submersible’s titanium end domes. In a report released at the same time as Kramer’s testimony, the NTSB noted that there was little to no full-thickness debris of the hull. All visible debris had delaminated into three hulls: the innermost hull of five layers, the hull made up of the second and third layers, and the hull made up of the fourth and fifth layers. Like a peeled onion, the hull had delaminated significantly at the glue that held the layers together.
The remains of the Titan submersible on the ocean floor, photographed by a remotely operated vehicle. Photo: Reuters
