Student Creates Self-Strengthening Nanocomposite Material

Carbon nanotube illustration (National Science Foundation)

A graduate student at Rice University in Houston, Texas has created a synthetic material combining nanotechnology and polymers that gets stronger from repeated stress. The results of the research by Brent Carey and colleagues appear this month in the journal ACS Nano (paid subscription required).

Carey, a Ph.D. candidate in the lab of materials science and engineering professor Pulickel Ajayan, made this discovery while testing the high-cycle fatigue properties of a composite he developed. Carey created the material by adding the inert, rubbery polymer polydimethylsiloxane to a field of vertically aligned, multi-walled nanotubes. Repeated loading-stress tests of the material not only failed to cause any damage, they seemed to make the  material stronger.

The tests involved a process called dynamic mechanical analysis (DMA). Carey submitted the material to a DMA protocol of 3.5 million compressions  — five compressions per second — over about one week. After that wear and tear, the stiffness of the composite had increased by 12 percent and showed potential for even further improvement.

So far Carey and his colleagues cannot pinpoint the reason for the behavior of this material. Polymers, made of long repeating chains of atoms, are not supposed to behave this way. “The data shows that there’s very little chemical interaction, if any, between the polymer and the nanotubes,” says Carey, “and it seems that this fluid interface is evolving during stressing.” Ajayan guesses that the use of nanomaterials increases the interfacial area for the amount of filler material added, which could amplify their impact compared to convention composites.

The research was supported in part by NASA’s Graduate Student Researchers Program.

Read more: Academics, Company Develop High-Performance Nanotech Fiber

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