Publisher Correction: Toughening mechanisms of the elytra of the diabolical ironclad beetle (original) (raw)
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Twist and lock: nutshell structures for high strength and energy absorption
Royal Society Open Science
Nutshells achieve remarkable properties by optimizing structure and chemistry at different hierarchical levels. Probing nutshells from the cellular down to the nano- and molecular level by microchemical and nanomechanical imaging techniques reveals insights into nature's packing concepts. In walnut and pistachio shells, carbohydrate and lignin polymers assemble to form thick-walled puzzle cells, which interlock three-dimensionally and show high tissue strength. Pistachio additionally achieves high-energy absorption by numerous lobes interconnected via ball-joint-like structures. By contrast, the three times more lignified walnut shells show brittle LEGO-brick failure, often along the numerous pit channels. In both species, cell walls (CWs) show distinct lamellar structures. These lamellae involve a helicoidal arrangement of cellulose macrofibrils as a recurring motif. Between the two nutshell species, these lamellae show differences in thickness and pitch angle, which can explai...
High performance biological structures
Nature has developed high-performance structures and materials over billions of years of evolution that can become a valuable source of inspiration for architectural, mechanical, hydrodynamic, optical and electrical design solutions as well as for advanced material technology. The main goal of this paper is to review biological structures that showcase impressive load-bearing and protective qualities with great potential for the development of new materials and mechanical design principles in a variety of applications. Crysomallon squamiferum is a species of gastropod that carries an ironplated, multi-layered exoskeleton which is unlike any other known natural or man-made protective structure. Another structure with exceptional damage tolerance is the dactyl club of the stomatopod species, Odontodactylus scyllarus, which can withstand impacts up to 1500N. The desert beetle, Phloeodes diabolicus, possesses a highly advanced, nonmineralized, composite exoskeleton that is light and extremely compression resistant. Teleost fish scales are also characterized by impressive load-stress and impact resistance. Found in all modern fish species, like the striped bass (Morone saxatilis), they provide a structural and, at the same time, protective support. However, such structures are found not only in animal species but also in plants, like the pomelo fruit (Citrus maxima), which can drop from heights of 10m and more without any significant damage, due to the excellent mechanical properties of its pericarp.
Investigation into the microstructure of high performance natural materials has revealed common patterns that are pervasive across animal species. For example, the helicoid motif has gained significant interest in the biomaterials community, where recent studies have highlighted its role in enabling damage tolerance in a diverse set of animals. Moreover, the helicoid motif corresponds to a highly adaptable architecture where the control of the pitch rotation angle between fibrous structures produces large changes in its mechanical response. Nature, takes advantage of this special feature enabling an active response to particular biological needs occurring during an animal's ontogeny. In this work, we demonstrate this adaptive behavior in helicoidal architectures by performing a mechanistic analysis of the changes occurring in the cuticle of the figeater beetle (Cotinis mutabilis) during its life cycle. We complement our investigation of the beetle with the testing of 3D printing samples and a systematic analysis of the effect of pitch angle in the inherent mechanics of helicoidal architectures. Experimentation and analysis reveal improved isotropy and enhanced toughness at lower pitch angles, highlighting the flexibility of the helicoidal architecture. Moreover, trends in stiffness measurements were found to be well-predicted by laminate theory, suggesting facile mechanics laws for use in biomimicry.
Multiscale Toughening Mechanisms in Biological Materials and Bioinspired Designs
Advanced Materials, 2019
Biological materials found in Nature such as nacre and bone are well recognized as light‐weight, strong, and tough structural materials. The remarkable toughness and damage tolerance of such biological materials are conferred through hierarchical assembly of their multiscale (i.e., atomic‐ to macroscale) architectures and components. Herein, the toughening mechanisms of different organisms at multilength scales are identified and summarized: macromolecular deformation, chemical bond breakage, and biomineral crystal imperfections at the atomic scale; biopolymer fibril reconfiguration/deformation and biomineral nanoparticle/nanoplatelet/nanorod translation, and crack reorientation at the nanoscale; crack deflection and twisting by characteristic features such as tubules and lamellae at the microscale; and structure and morphology optimization at the macroscale. In addition, the actual loading conditions of the natural organisms are different, leading to energy dissipation occurring at different time scales. These toughening mechanisms are further illustrated by comparing the experimental results with computational modeling. Modeling methods at different length and time scales are reviewed. Examples of biomimetic designs that realize the multiscale toughening mechanisms in engineering materials are introduced. Indeed, there is still plenty of room mimicking the strong and tough biological designs at the multilength and time scale in Nature.
Structural Orientation and Anisotropy in Biological Materials: Functional Designs and Mechanics
Advanced Functional Materials, 2020
Biological materials exhibit anisotropic characteristics because of the anisometric nature of their constituents and their preferred alignment within interfacial matrices. The regulation of structural orientations is the basis for material designs in nature and may offer inspiration for man-made materials. Here, how structural orientation and anisotropy are designed into biological materials to achieve diverse functionalities is revisited. The orientation dependencies of differing mechanical properties are introduced based on a 2D composite model with wood and bone as examples; as such, anisotropic architectures and their roles in property optimization in biological systems are elucidated. Biological structural orientations are designed to achieve extrinsic toughening via complicated cracking paths, robust and releasable adhesion from anisotropic contact, programmable dynamic response by controlled expansion, enhanced contact damage resistance from varying orientations, and simultaneous optimization of multiple properties by adaptive structural reorientation. The underlying mechanics and material-design principles that could be reproduced in man-made systems are highlighted. Finally, the potential and challenges in developing a better understanding to implement such natural designs of structural orientation and anisotropy are discussed in light of current advances. The translation of these biological design principles can promote the creation of new synthetic materials with unprecedented properties and functionalities.
A Sinusoidally Architected Helicoidal Biocomposite
Advanced materials (Deerfield Beach, Fla.), 2016
A fibrous herringbone-modified helicoidal architecture is identified within the exocuticle of an impact-resistant crustacean appendage. This previously unreported composite microstructure, which features highly textured apatite mineral templated by an alpha-chitin matrix, provides enhanced stress redistribution and energy absorption over the traditional helicoidal design under compressive loading. Nanoscale toughening mechanisms are also identified using high-load nanoindentation and in situ transmission electron microscopy picoindentation.
Tough Nature-Inspired Helicoidal Composites with Printing-Induced Voids
Cell Reports Physical Science, 2020
Micro-scale voids are discovered in the exoskeletons of Odontodactylus japonica. Yin et al. print bioinspired composites to mimic this material, which are found to have superior specific impact energy in the presence of voids. Simulations indicate that the voids expand and coalesce on loading, contributing to impact toughness.
Journal of the Mechanics and Physics of Solids
Bouligand structures are widely observed in natural materials; elasmoid fish scales and the exoskeleton of arthropods, such as lobsters, crabs, mantis shrimp and insects, are prime examples. In fish scales, such as those of the Arapaima gigas, the tough inner core beneath the harder surface of the scale displays a Bouligand structure comprising a layered arrangement of collagen fibrils with an orthogonal or twisted staircase (or plywood) architecture. A much rarer variation of this structure, the double-twisted Bouligand structure, has been discovered in the primitive elasmoid scales of the coelacanth fish; this architecture is quite distinct from "modern" elasmoid fish scales yet provides extraordinary resistance to deformation and fracture. Here we examine the toughening mechanisms created by the double-twisted Bouligand structure in comparison to those generated by the more common single Bouligand structures. Specifically, we have developed an orientationdependent, hyperelastic, phase-field fracture mechanics method to computationally examine the relative fracture toughness of elasmoid fish scales comprising single vs. double-twisted Bouligand structures of fibrils. The model demonstrates the critical role played by the extra inter-bundle fibrils found in coelacanth fish scales in enhancing the toughness of Bouligand-type structures. Synthesis and fracture tests of 3-D printed Bouligand-type materials are presented to support the modeling and complement our understanding of the fracture mechanisms in Bouligandtype structures.