Theoretical tubulanes inspire ultra-hard polymers: The sample printed at Rice University is full of holes, but it does better than solid materials.
A light material full of holes is almost as hard as diamond. The mere bumps created by accelerating bullets prove this.
Researchers at Rice University's Brown School of Engineering and their colleagues are testing polymers based on tubulans, theoretical structures of cross-linked carbon nanotubes predicted to be exceptionally strong.
The Rice lab of Materials scientist Pulickel Ajayan found that tubulans can be imitated as enlarged, 3D-printed polymer blocks that deflect the projectiles better than the same material without holes. The blocks are also highly compressible without breaking up.
As detailed in Small, the discovery could lead to printed structures of any size with adjustable mechanical properties.
In 1993, tubulans were predicted by chemist Ray Baughman of the University of Texas at Dallas and physicist Douglas Galvão of the State University of Campinas in Brazil, both co-principal Investigators of the new paper , Tubulans themselves still need to be made, but their polymer cousins might be second best.
Rice's student and lead author, Seyed Mohammad Sajadi, and his colleagues built computer simulations of various tubule blocks, printed the designs as macroscale polymers, and squeezed out squeezing forces and accelerating balls. The best thing turned out to be ten times better at stopping a bullet than a massive block of the same material.
The Rice team fired projectiles at a speed of 5.8 kilometers per second into patterned and solid cubes. Sajadi said the results are impressive. "The bullet was in the second layer of the structure," he said. "But in the massive block, cracks spread throughout the structure."
Tests in a laboratory press showed how the porous polymer lattice collapses tubulan blocks without forming cracks, said Sajadi.
The Ajayan group made it similar to structures two years ago when it converted theoretical models of blacksites into 3D printed blocks. But the new work is a step toward what materials scientists consider a holy grail, Sajadi said.
"There are many theoretical systems that humans can not synthesize," he said. "They have been impractical and elusive, but in 3D printing we can continue to use the predicted mechanical properties because they are the result of topology rather than size."
Sajadi said that tubulane-like metal structures, ceramics Optimizing the grid design could lead to better materials for civil, aerospace, automotive, sports, packaging, and biomedical applications.
"The unique characteristics of such structures arise from their complex topology, which is independent of scale "He said Chandra Sekhar Tiwary, graduate of Rice, co-principal investigator of the project and now assistant professor at the Indian Institute of Technology in Kharagpur. "Topology-driven boosting or upgrading capability may also be useful for other structural designs."
According to co-authors Peter Boul and Carl Thaemlitz of Aramco Services Co., a sponsor of research, potential applications span many industries, but oil and gas Gas will find tubulane structures particularly valuable as tough and durable materials for well construction. Such materials must withstand impacts, especially hydraulic fracturing, which can crush standard cements.
"The impact resistance of these 3D printed structures makes them a class of theirs," said Boul.
###  Reference: "3D Printed Tubulans as Lightweight, Hypervelocity Shock-Resistant Structures" by Seyed Mohammad Sajadi, Cristiano F. Woellner, Prathyush Ramesh, Shannon L. Eichmann, Qiushi Sun, Peter J. Boul, Carl J. Thämlitz, Muhammad M. Rahman Ray H. Baughman, Douglas S. Galvão, Chandra Sekhar Tiwary and Pulickel M. Ajayan, November 11, 2019, Small .
DOI: 10.1002 / smll.201904747
Co-authors are graduate student Prathyush Ramesh and researcher Muhammad Rahman of Rice; Rice Alumnus Cristiano Woellner, Assistant Professor at the Federal University of Parana, Brazil; and Rice alumnus Shannon Eichmann and Qiushi Sun of the Aramco Research Center, Houston. Ajayan is Chairman of the Department of Materials Science and Nanotechnology of Rice, Professor of Engineering by Benjamin M. and Mary Greenwood Anderson and Professor of Chemistry Research.