Researchers in the US have 3D printed lightweight plastic structures that have hardness properties similar to diamond and are capable of enduring the impact of a bullet.

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The team, from Rice University’s Brown School of Engineering in Texas, are testing polymers based on tubulanes, theoretical structures of crosslinked carbon nanotubes predicted to have extraordinary strength.

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The Rice lab of materials scientist Pulickel Ajayan found tubulanes can be mimicked as scaled-up, 3D-printed polymer blocks that prove to be better at deflecting projectiles than the same material without holes. These blocks are also highly compressible without breaking apart.

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Rice graduate student Seyed Mohammad Sajadi and his colleagues built computer simulations of various tubulane blocks, printed the designs as macroscale polymers and then subjected them to crushing forces and speeding bullets. The best proved to be 10 times better at stopping a bullet than a solid block of the same material.

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The Rice team fired projectiles into patterned and solid cubes at 5.8m per second and, following the experiment, Sajadi said the results were impressive. “The bullet was stuck in the second layer of the structure,” he said. “But in the solid block, cracks propagated through the whole structure.”

Tests in a lab press showed how the porous polymer lattice lets tubulane blocks collapse in upon themselves without cracking, Sajadi added.

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