|Dr. Ashok Ghosh shows off a piece of typical polyurethane foam and a piece of engineering composite that includes exterior layers of Kevlar. He earned patent for the new composite.
Dr. Ghosh’s invention is a composite structure that has Kevlar skin with a fluid-filled polyurethane foam core. The material may find applications in a variety of devices – from submarines and the Space Shuttle to military helmets and bullet-proof vests to radiation shielding. A short video on “Research Rocks: Students Explore Submarine Materials” was broadcast by KOAT TV in 2010.
One of the material’s key characteristics is its ability to disperse energy – thermal, acoustic, impact and explosive/shockwave energy.
The key to dispersing energy is the core layer of the polyurethane foam, Dr. Ghosh said. He said the inner structure of the foam is filled with varying sizes of spherical cells of polyurethane. A cross-section of polyurethane foam reveals larger balls, or cells, in the center, with smaller cells on the outer edges. The foam layer has impermeable faces, allowing the material to be filled with compatible fluid and sealed.
“The core layer is engineered,” he said. “The basic materials are procured over-the-counter, but subsequently engineered to do certain things. This is a unique material with unique characteristics.”
Dr. Ghosh and his team of students tested the material for a variety of acoustic energy attenuation characteristics under a grant from the Office of Naval Research. Some tests were performed at New Mexico Tech and the rest at the Air Force Research Lab in
“You could make a submarine skin out of this material,” he said. “It will have the capability to absorb wide range of noise (tested for frequencies from 250 hertz to 10 kilohertz . When designed carefully, it is possible to make the sound signature of this vehicle very close to zero.”
During the testing of thermal management characteristics, Dr. Ghosh found that no ASTM standards that can be applied to this unique material. So, Dr. Ghosh and his student Phillip Chavez developed their own test method and successfully demonstrated that this composite has good thermal management capability and can in fact dissipate heat energy by transferring thermal load from the location where heat energy is imparted to other parts of the body.
Developed by Dupont scientists in the 1960s, Kevlar is a synthetic fiber that, when woven, creates a material five times stronger than steel. Kevlar is used in tires, sails, bullet-proof materials. Coupled with the fluid-filled foam core, the new composite would lend itself to use in spacecraft and various other applications, Dr. Ghosh said.
The original patent application listed 18 features, or “claims,” that differentiate the material as unique. After refuting counter-claims, Dr. Ghosh added two new claims, thus strengthening his argument for a successful patent application.
At present, Dr. Ghosh has three graduate students working on implementation of the patent. Chris Turner is working on developing a helmet using the material. David Chavez is working on a protective vest. Naitram Birbahadur is working on general characterization. Other students who worked on the study of this material in the past are Phillip Chavez, Everest Sewell, Ian Luders, Jason Mathews, Jason Metzger, Byron Mortons, Nicholas Spinhirne and Holly Chamberlin. Andrew D. Williams of Air Force Research Laboratory, Emil Ardelean of Schafer Corp. and J. M. Zucker of LANL also contributed to the research project.
David Chavez has been working on the project for more than a year. He is finishing his master’s in mechanical engineering with an emphasis in explosives, in anticipation of starting his career as a test engineer at the Naval Surface Warfare Center in Virginia.
“The biggest challenge in this project is to integrate this new material into something we use for explosive defense,” he said. “We’re trying to improve what’s out there and find something novel. We’re taking new approaches to how we create materials and we’re combining materials in never-been-seen-before ways.”
|Professor Dr. Ashok Ghosh explains the testing device he built to test the thermal management of the engineered material.
Photos by Thomas Guengerich/New Mexico Tech
Dr. Ghosh has also applied for funding from the New Mexico Space Grant Consortium to test the material for its radiation shielding characteristics. Undergraduate student Miquela Trujillo is helping develop that proposal and test.
A junior in mechanical engineering, Trujillo said she appreciates the opportunity to do research in an exciting and interesting field. She is helping design the tests that will examine how well the composite shields or absorbs solar and space radiation.
“This project has sparked my interest in nuclear engineering,” she said. “I’m applying what I’ve learned in classes, plus I’m doing extra research on the space environment and learning about radiation.”
A graduate of McCurdy High School in Espanola, Trujillo is working with scientists at Los Alamos National Laboratory to develop a system of exposing the material to radioactive ions, then see how the composite’s properties might change.
Dr. Ghosh developed his concept from a detailed study of the structure of the human skull. He started his investigations while at the Indian Institute of Technology in the 1990s.
“You’ll find that natural concepts have evolved over time to be most efficient but very complex,” he said. “The skull is very complicated and thus replicating its morphology is challenging and often expensive.”
After examining and analyzing the skull’s structure through a scanning electron microscope and other means, Dr. Ghosh started to develop a concept that would mimic the features of a skull. He looked at available commercial materials, both natural origin and man made, before settling on polyurethane, which has a many comparable characteristics as that of the human skull.
He also looked at materials currently used as “acoustic blankets” in the fairing structure of a space launch vehicle. The Air Force has various designs for acoustic blankets that isolate a payload from damaging noise and vibration during lift-off.
“That’s the basis of the whole thing,” Dr. Ghosh said. “Now, we have a multifunctional composite, which may find application in various products and services. Now, if anyone wants to use this material, they’ll have to come to New Mexico Tech for a license.”
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By Thomas Guengerich/New Mexico Tech