Hierarchically Enhanced Impact Resistance of Bioinspired Composites.
TL;DR: A 3D biomimetic conch shell prototype is presented, which can replicate the crack arresting mechanisms embedded in the natural architecture and show that adding the second level of cross-lamellar hierarchy can boost impact performance by 70% and 85% compared to a single-level hierarchy and the stiff constituent, respectively.
Abstract: An order of magnitude tougher than nacre, conch shells are known for being one of the toughest body armors in nature. However, the complexity of the conch shell architecture creates a barrier to emulating its cross-lamellar structure in synthetic materials. Here, a 3D biomimetic conch shell prototype is presented, which can replicate the crack arresting mechanisms embedded in the natural architecture. Through an integrated approach combining simulation, additive manufacturing, and drop tower testing, the function of hierarchy in conch shell's multiscale microarchitectures is explicated. The results show that adding the second level of cross-lamellar hierarchy can boost impact performance by 70% and 85% compared to a single-level hierarchy and the stiff constituent, respectively. The overarching mechanism responsible for the impact resistance of conch shell is the generation of pathways for crack deviation, which can be generalized to the design of future protective apparatus such as helmets and body armor.
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TL;DR: A comprehensive overview of recent advances in the development of bio-inspired structures for energy absorption applications is provided in this paper, where the authors describe the unique features and remarkable mechanical properties of biological structures such as plants and animals, which can be mimicked to design efficient energy absorbers.
Abstract: It is widely known that the availability of lightweight structures with excellent energy absorption capacity is essential for numerous engineering applications. Inspired by many biological structures in nature, bio-inspired structures have been proved to exhibit a significant improvement over conventional structures in energy absorption capacity. Therefore, use of the biomimetic approach for designing novel lightweight structures with excellent energy absorption capacity has been increasing in engineering fields in recent years. This paper provides a comprehensive overview of recent advances in the development of bio-inspired structures for energy absorption applications. In particular, we describe the unique features and remarkable mechanical properties of biological structures such as plants and animals, which can be mimicked to design efficient energy absorbers. Next, we review and discuss the structural designs as well as the energy absorption characteristics of current bio-inspired structures with different configurations and structures, including multi-cell tubes, frusta, sandwich panels, composite plates, honeycombs, foams, building structures and lattices. These materials have been used for bio-inspired structures, including but not limited to metals, polymers, fibre-reinforced composites, concrete and glass. We also discussed the manufacturing techniques of bio-inspired structures based on conventional methods, and adaptive manufacturing (3D printing). Finally, contemporary challenges and future directions for bio-inspired structures are presented. This synopsis provides a useful platform for researchers and engineers to create novel designs of bio-inspired structures for energy absorption applications.
424 citations
TL;DR: This work proposes a new approach to design hierarchical materials using machine learning, trained with a database of hundreds of thousands of structures from finite element analysis, together with a self-learning algorithm for discovering high-performing materials where inferior designs are phased out for superior candidates.
Abstract: Biomimicry, adapting and implementing nature's designs provides an adequate first-order solution to achieving superior mechanical properties. However, the design space is too vast even using biomimetic designs as prototypes for optimization. Here, we propose a new approach to design hierarchical materials using machine learning, trained with a database of hundreds of thousands of structures from finite element analysis, together with a self-learning algorithm for discovering high-performing materials where inferior designs are phased out for superior candidates. Results show that our approach can create microstructural patterns that lead to tougher and stronger materials, which are validated through additive manufacturing and testing. We further show that machine learning can be used as an alternative method of coarse-graining – analyzing and designing materials without the use of full microstructural data. This novel paradigm of smart additive manufacturing can aid in the discovery and fabrication of new material designs boasting orders of magnitude increase in computational efficacy over conventional methods.
309 citations
TL;DR: This work optimization a large-scale system not tractable by an exhaustive brute force approach and shows that it is a promising tool towards composite design offers a new perspective in the exploration of design spaces and accelerating the discovery of new functional, customizable composites.
299 citations
TL;DR: 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 andBiomineral nanoparticle/nanoplatelet/nanorod translation, and crack reorientation at the nanoscale.
Abstract: 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.
290 citations
TL;DR: An overview of recent developments in 3D printing of biomimetic reinforced mechanics, shape changing, and hydrodynamic structures, as well as optical and electrical devices is provided.
Abstract: Nature has developed high-performance materials and structures over millions of years of evolution and provides valuable sources of inspiration for the design of next-generation structural materials, given the variety of excellent mechanical, hydrodynamic, optical, and electrical properties. Biomimicry, by learning from nature's concepts and design principles, is driving a paradigm shift in modern materials science and technology. However, the complicated structural architectures in nature far exceed the capability of traditional design and fabrication technologies, which hinders the progress of biomimetic study and its usage in engineering systems. Additive manufacturing (three-dimensional (3D) printing) has created new opportunities for manipulating and mimicking the intrinsically multiscale, multimaterial, and multifunctional structures in nature. Here, an overview of recent developments in 3D printing of biomimetic reinforced mechanics, shape changing, and hydrodynamic structures, as well as optical and electrical devices is provided. The inspirations are from various creatures such as nacre, lobster claw, pine cone, flowers, octopus, butterfly wing, fly eye, etc., and various 3D-printing technologies are discussed. Future opportunities for the development of biomimetic 3D-printing technology to fabricate next-generation functional materials and structures in mechanical, electrical, optical, and biomedical engineering are also outlined.
274 citations
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TL;DR: The common design motifs of a range of natural structural materials are reviewed, and the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts are discussed.
Abstract: Natural structural materials are built at ambient temperature from a fairly limited selection of components. They usually comprise hard and soft phases arranged in complex hierarchical architectures, with characteristic dimensions spanning from the nanoscale to the macroscale. The resulting materials are lightweight and often display unique combinations of strength and toughness, but have proven difficult to mimic synthetically. Here, we review the common design motifs of a range of natural structural materials, and discuss the difficulties associated with the design and fabrication of synthetic structures that mimic the structural and mechanical characteristics of their natural counterparts.
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TL;DR: Quantification of cerebral perfusion by monitoring of intracranial pressure and treatment of cerebral hypoperfusion decrease secondary injury and an organised trauma system that allows rapid resuscitation and transport directly to an experienced trauma centre significantly lowers mortality and morbidity.
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TL;DR: This work reviews 48 cases of neuropathologically verified CTE recorded in the literature and document the detailed findings of CTE in 3 professionalathletes, 1 football player and 2 boxers.
Abstract: Since the 1920s, it has been known that the repetitive brain trauma associated with boxing may produce a progressive neurological deterioration, originally termed dementia pugilistica, and more recently, chronic traumatic encephalopathy (CTE). We review 48 cases of neuropathologically verified CTE recorded in the literature and document the detailed findings of CTE in 3 profession althletes, 1 football player and 2 boxers. Clinically, CTE is associated with memory disturbances, behavioral and personality changes, parkinsonism, and speech and gait abnormalities. Neuropathologically, CTE is characterized by atrophy of the cerebral hemispheres, medial temporal lobe, thalamus, mammillary bodies, and brainstem, with ventricular dilatation and a fenestrated cavum septum pellucidum. Microscopically, there are extensive tau-immunoreactive neurofibrillary tangles, astrocytic tangles, and spindle-shaped and threadlike neurites throughout the brain. The neurofibrillary degeneration of CTE is distinguished from other tauopathies by preferential involvement of the superficial cortical layers, irregular patchy distribution in the frontal and temporal cortices, propensity for sulcal depths, prominent perivascular, periventricular, and subpial distribution, and marked accumulation of tau-immunoreactive astrocytes. Deposition of beta-amyloid, most commonly as diffuse plaques, occurs in fewer than half the cases. Chronic traumatic encephalopathy is a neuropathologically distinct slowly progressive tauopathy with a clear environmental etiology.
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TL;DR: The results show that n-HA/PA composite scaffolds exhibit good biocompatibility and extensive osteoconductivity with host bone, and the introduction of MSCs to the scaffolds dramatically enhanced the efficiency of new bone formation, especially at the initial stage after implantation.
690 citations
TL;DR: In contrast to synthetic materials, evolutionary developments in biology have resulted in materials with remarkable structural properties, made out of relatively weak constituents, arranged in complex hierarchical patterns as discussed by the authors, which can exhibit superior levels of strength and toughness.
651 citations