UB engineer discusses materials used to build Titan sub

BUFFALO, N.Y. – University at Buffalo researcher Deborah Chung is an expert in the study of composite materials, such as those used to build the Titan submersible vessel that recently imploded in the Atlantic Ocean killing five people.

Carbon fiber composites, which was among the materials the Titan was made of, are widely used for aircraft due to their outstanding combination of high strength and low weight, Chung says.

These same qualities are attractive to submersibles. However, the outside forces encountered by aircraft are little compared to those faced by deep-water submersibles, she adds.

“Carbon fiber is widely used in the construction of pressure vessels with the fiber wound around the perimeter of the vessel,” says Chung. “This design allows these vessels to withstand high pressure from the inside – but not necessarily from outside forces.” 

“The high pressure from inside the pressure vessel causes the fibers to be under tension. But that’s usually OK because carbon fibers are extraordinarily strong under tension, and, as such, the pressure vessel can withstand extremely high pressures from within,” she says.

“Vessels like the Titan submersible are not, however, as strong under compression. As these vehicles go deeper under water, the amount of pressure from weight of the water above increases,” she says. “This situation does not allow the incredible properties of the carbon fiber to be exploited adequately, and the results, as we recently witnessed, can be tragic.”

Carbon fiber composites suffer from fatigue (stress that weakens the material) upon repeated use, Chung says. This causes the fiber layers to separate from one another, a process called delamination. Extremely high outside pressure, such as what the Titan faced, tends to worsen delamination and, thus, hasten a catastrophic failure like the implosion.

Continuous monitoring of composites could help alleviate this problem, particularly if the monitoring allows detection of the initial stages of fatigue, she says.

Chung specializes in monitoring based on electrical measurement, which is effective in detecting early signs of damage. In contrast, monitoring by detecting sound waves emitted during cracking, as Titan was reportedly capable of, tends to be ineffective for monitoring the initial stages of damage, she says.