Scientists have created a new 3D-printed mold that dissolved in water to produce linerless, lightweight tanks for storying hydrogen in addition to other gases under high pressure.
The mold, also known as mandrel, was designed by a group of researchers at the Department of Energy’s (DOE) Oak Ridge National Laboratory (ORNL). As part of the project, the team worked together with aerospace firm Infinite Composites, additive manufacturing company JuggerBot 3D, and Oklahoma State University.
Ahmed Arabi Hassen, PhD, who led the project, revealed that the technology uses a specially tailored water-soluble polymer to create the mandrels. These are then used to manufacture Type V composite pressure vessels.
These vessels are entirely made from composite materials. They also do not need a permanent internal liner. On top of that, they can store hydrogen, compressed natural gas, nitrogen, and helium for the aerospace, defense, transportation, and energy industries.
A water-soluble mandrel
Lightweight gas storage tanks can be difficult to produce especially when creating and removing the internal molds used to shape them. Engineers rely on expensive metal molds or complex tools that must be disassembled before removal.
Hassen discussed the significance of Type V composite pressure vessels, and their potential. “Type V linerless composite pressure vessels represent the next frontier in lightweight, high-pressure gas storage, but their manufacturing remains extremely challenging, particularly when it comes to producing and removing complex internal tooling,” he added.
Credit: Logan Korn / ORNL, U.S. Dept. of Energy
To tackle the challenge and create a temporary mandrel, the researchers turned to large-format additive manufacturing, commonly known as 3D printing. They used a specially formulated polymer that can dissolve in water, which serves to print the mold in the desired shape of the tank.
The engineers then wound carbon fiber around the mandrel to create the vessel’s outer structure. Once the composite material cured, they dissolved the temporary mold in water. As a result, the team designed a hollow carbon-fiber tank without a permanent internal liner. They then applied a gas-barrier coating to the vessel.
Making gas tanks lighter
The research team pointed out that the technology does not require complicated mechanical systems to remove the internal tooling. It can also eliminate the need for solvents during mold removal, and simplify the production of large pressure vessels.
Hassen explained that the method could also ensure high dimensional accuracy. “Our water-soluble, 3D-printed mandrels represent an important step toward overcoming this barrier and enabling scalable, cost-effective manufacturing of Type V vessels,” he continued.
The design also reduces the tanks’ overall weight and prevents problems caused by permanent internal liners. Additionally, replacing conventional metal tooling with 3D-printed molds could cut manufacturing complexity, shorten production times, and lower costs.
This could be useful for industries that require lightweight gas storage systems capable of operating under high pressure. “This achievement demonstrates how advanced manufacturing and strong industry partnerships can help bring these technologies closer to commercial reality,” Hassen concluded in a press release.
The team carried out its research at the Department of Energy’s Manufacturing Demonstration Facility. The project was backed by the DOE’s Office of Critical Minerals and Energy Innovation.