Feb 7, 2018 | By Tess

A breakthrough in 3D printed foam materials could help advance and improve submarine vehicles, allowing the underwater crafts to explore at greater depths.

A team of materials science researchers from the NYU Tandon School of Engineering has developed a way to 3D print syntactic foam, a composite material used for a range of applications in automotive, aircraft, ship, and submarine manufacturing.

Syntactic foams are made up of a mixture of microscopic hollow ceramic or glass spheres and an epoxy or plastic resin material. The material is popular in manufacturing because it is at once incredibly strong, lightweight, and buoyant. (Understandably, these three characteristics have made it especially useful in submarine production.)

The NYU scientists say the ability to 3D print syntactic foams could enable the production of more complex components with better stress resistance and physical properties, improving on the currently used method of injection molding syntactic foam parts.

Injection molding the foam, while mostly effective, requires parts to be joined and attached after molding, which can, as the researchers say, “introduce vulnerabilities.” Additive manufacturing, on the other hand, would make it possible to 3D print whole and highly complex parts, thus improving the overall strength of the components.

How exactly does 3D printing syntactic foam work? It’s surprisingly straightforward, as the research team was able to develop a syntactic foam filament that can be processed using off-the-shelf 3D printers.

The filament development, for its part, was a tad more complex. As the team explains in a recently published study, it faced several challenges in creating a 3D printable filament, including stopping the foam’s microspheres from either breaking down during the printing process or blocking the printer nozzle.

In the end, however, they created a printable filament made from high-density polyethylene plastic (HDPE) and microspheres composed of recycled fly ash, a waste byproduct of coal combustion. In addition to its printability, the syntactic foam material is also fully recyclable.

“Our focus was to develop a filament that can be used in commercial printers without any change in the printer hardware," explained  Nikhil Gupta, an associate professor of mechanical and aerospace engineering who worked on the project. “There are a lot of parameters that affect the printing process, including build-plate material, temperature, and printing speed. Finding a set of optimum conditions was the key to making the printing of high-quality parts possible.”

A key element in developing the filament was finding the right size for the hollow microspheres which could allow them to pass through the printer nozzle easily without clogging. Ultimately, the microspheres have a diameter range of 0.04 mm to 0.07 mm, which pass easily through a standard 1.7 mm printer nozzle.

Further, the scientists had to figure out how to mix the HDPE resin with the microstructures in a way that wouldn’t completely break and crush the hollow forms.

“We want to add as many hollow particles as possible to make the material lighter, but having a greater number of particles means more of them will break during processing," said Ashish Kumar Singh, one of Gupta’s doctoral students and the leader of the study. "The survival of hollow particles first during filament manufacturing and then in the 3D printing process requires a lot of process control."

Impressively, the 3D printed syntactic foam material has demonstrated excellent properties, and is reportedly comparable to injection molded parts in terms of tensile strength and density. “The results show that the properties of 3D printed syntactic foam components are at par with the widely used traditional injection molded parts of the same material,” added Singh.

Currently, the team is working on optimizing the material for the development of submarine vehicles which can operate at specific depths.

The research was recently published about in JOM, the Journal of the Minerals, Metals & Materials Society in two separate papers: “Additive Manufacturing of Syntactic Foams: Part 1: Development, Properties, and Recycling Potential of Filaments” and “Additive Manufacturing of Syntactic Foams: Part 2: Specimen Printing and Mechanical Property Characterization.

The NYU Tandon Mechanical Engineering department team worked in collaboration with a team from the National Institute of Technology Karnataka, Surathkal in India.

 

 

Posted in 3D Printing Materials

 

 

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