title: Pervasive nanoscale deformation twinning as a catalyst for efficient energy dissipation in a bioceramic armour.
abstract: Hierarchical composite materials design in biological exoskeletons achieves penetration resistance through a variety of energy-dissipating mechanisms while simultaneously balancing the need for damage localization to avoid compromising the mechanical integrity of the entire structure and to maintain multi-hit capability. Here, we show that the shell of the bivalve Placuna placenta (~99 wt% calcite), which possesses the unique optical property of ~80% total transmission of visible light, simultaneously achieves penetration resistance and deformation localization via increasing energy dissipation density (0.290 ± 0.072 nJ μm(-3)) by approximately an order of magnitude relative to single-crystal geological calcite (0.034 ± 0.013 nJ μm(-3)). P. placenta, which is composed of a layered assembly of elongated diamond-shaped calcite crystals, undergoes pervasive nanoscale deformation twinning (width ~50 nm) surrounding the penetration zone, which catalyses a series of additional inelastic energy dissipating mechanisms such as interfacial and intracrystalline nanocracking, viscoplastic stretching of interfacial organic material, and nanograin formation and reorientation.
authors.forename: Ling
authors.initials: L
authors.lastname: Li
authors.forename: Christine
authors.initials: C
authors.lastname: Ortiz
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry*; D001696:Biomechanical Phenomena; D049872:Bivalvia / Q000737:chemistry / Q000648:ultrastructure; D002119:Calcium Carbonate / Q000737:chemistry; D002516:Ceramics / Q000737:chemistry*; D003460:Crystallization; D004548:Elasticity; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology; D055620:Optical Phenomena
chemical_list: D001672:Biocompatible Materials; D002119:Calcium Carbonate