Thu. Aug 13th, 2020

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Impact Resistant Armor from the Conch Shell

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Just recently a team of researchers from MIT have developed a 3D printing technology that allowed them to duplicate the structure of a conch shell. Despite being highly mineralized natural composite materials are renowned for their mechanical strength and toughness.Because the conch shell is so strong and tough the goal of the researchers is to mimic it in the lab and produce materials for use in such industries as aerospace, aviation, military and for arms.The spiral-shaped shell is 99% aragonite. It is a mineral made of calcium, carbon and oxygen –yet it is up to 1,000 times as tough as pure aragonite.  Under a high-power electron microscope conch shells have a complex, three-tiered structure with a zigzag matrix, essentially resistant to breakage.The layered crisscross structure strengthens the shell in all directions. The shell of the Strombus gigas can be considered a ‘ceramic plywood’, and can guide the biomimetic design of tough, lightweight structures. In their paper in the AmericanScientist Roberto Ballarini and Arthur H. Heuer wrote,“The calcium carbonate gives the shell stiffness and strength, and the protein between these mineral sheets not only provides some compliance, but also enables the shell to develop energy-dissipating microcracks that make it much harder to break. When force is first applied to the shell, the protein-containing regions between aragonite crystals develop very useful, noncatastrophic microcracks. Such microcracking toughens the structure by dissipating the energy of mechanical forces. The cross-lamellar architecture itself provides a second energy-dissipating mechanism. Because alternating sheets of lamellae are at right angles to each other, cracks can only propagate through the material by following a tortuous zigzag path, which requires much more energy to achieve a complete fracture.Simply stated, an energy forced upon conch armor must follow a sort of zig-zagging path whereby much of the energy dissipates. Another in depth article can be found here called The Conch Shell as a Model for Tougher Composites.The MIT team subjected the created material to drop tests and the conch-like 3D material was 70 percent better than a traditional fiber composite arrangement and 85 percent better at preventing crack propagation than samples of the base material without the conch-like structure.In a paper by MIT graduate student Grace Gu, postdoc Mahdi Takaffoli, and McAfee Professor of Engineering Markus Buehler, in the journal Advanced Materials, they noted their findings. Team member Markus Buehler stated it has “stiffness, like glass or ceramics,” but it’s not brittle and doesn’t easily break.Though the structure of the conch shell was recently understood, it could not be replicated well. Their lab has now developed 3-D printing technology that allows them to duplicate that structure and be able to test it.Gu states that individualized helmets or body armor could be made for each soldier.  She stated, “tailored and personalized; the computer would optimize it for you, based on a scan of your skull, and the helmet would be printed just for you,”.Traditional helmets use a metal shell for strength and energy dissipation and comfort both need the use of a flexible liner. The new composite material would use the combination of strength and toughness qualities like a marriage of steel and rubber. Strength refers to the ability of the material to resist damage, like steel, while toughness means the material can dissipate energy like rubber does.Body armor and other applications for which they are now too brittle yet made from a conch shell structure would be very durable. MIT News*The views and opinions expressed on this website are solely those of the original authors and contributors. These views and opinions do not necessarily represent those of Spotter Up Magazine, the administrative staff, and/or any/all contributors to this site.[jetpack_subscription_form] срочный займ на карту без отказа

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