title: Nanotwin-governed toughening mechanism in hierarchically structured biological materials.
abstract: As a natural biocomposite, Strombus gigas, commonly known as the giant pink queen conch shell, exhibits outstanding mechanical properties, especially a high fracture toughness. It is known that the basic building block of conch shell contains a high density of growth twins with average thickness of several nanometres, but their effects on the mechanical properties of the shell remain mysterious. Here we reveal a toughening mechanism governed by nanoscale twins in the conch shell. A combination of in situ fracture experiments inside a transmission electron microscope, large-scale atomistic simulations and finite element modelling show that the twin boundaries can effectively block crack propagation by inducing phase transformation and delocalization of deformation around the crack tip. This mechanism leads to an increase in fracture energy of the basic building block by one order of magnitude, and contributes significantly to that of the overall structure via structural hierarchy.
authors.affiliation: Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
authors.forename: Yoon Ah
authors.initials: YA
authors.lastname: Shin
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Sheng
authors.initials: S
authors.lastname: Yin
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island 02912, USA.|Center for Advanced Mechanics and Materials, Applied Mechanics Laboratory, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
authors.forename: Subin
authors.initials: S
authors.lastname: Lee
authors.affiliation: Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
authors.forename: Sungmin
authors.initials: S
authors.lastname: Moon
authors.affiliation: Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.|IBS Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.
authors.forename: Jiwon
authors.initials: J
authors.lastname: Jeong
authors.affiliation: Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.
authors.forename: Minhyug
authors.initials: M
authors.lastname: Kwon
authors.affiliation: Nano-Bio Electron Microscopy Research Group, Korea Basic Science Institute (KBSI), Daejeon 34133, Republic of Korea.
authors.forename: Seung Jo
authors.initials: SJ
authors.lastname: Yoo
authors.affiliation: IBS Center for Integrated Nanostructure Physics (CINAP), Institute for Basic Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.|Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.
authors.forename: Young-Min
authors.initials: YM
authors.lastname: Kim
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Teng
authors.initials: T
authors.lastname: Zhang
authors.affiliation: School of Engineering, Brown University, Providence, Rhode Island 02912, USA.
authors.forename: Huajian
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 37673, Republic of Korea.|Department of Energy Science, Sungkyunkwan University, Suwon 16419, Republic of Korea.
authors.forename: Sang Ho
authors.initials: SH
authors.lastname: Oh
mesh_terms: D060105:Animal Shells / Q000737:chemistry*; D000818:Animals; D001696:Biomechanical Phenomena; D049851:Gastropoda / Q000737:chemistry*; D008954:Models, Biological; D049329:Nanostructures / Q000737:chemistry*