The Bouligand structure features a helicoidal (twisted plywood) layup of fibers that are uniaxially arranged in-plane and is a hallmark of biomaterials that exhibit outstanding impact resistance. Despite its performance advantage, the underlying mechanisms for its outstanding impact resistance remain poorly understood, posing challenges for optimizing the design and development of bio-inspired materials with Bouligand microstructures. Interestingly, many bio-sourced nanomaterials, such as cellulose nanocrystals (CNCs), readily self-assemble into helicoidal thin films with inter-layer (pitch) angles tunable via solvent processing. Taking CNC films as a model Bouligand system, we present atomistically-informed coarse-grained molecular dynamics simulations to measure the ballistic performance of thin films with helicoidally assembled nanocrystals by subjecting them to loading similar to laser-induced projectile impact tests. The effect of pitch angle on the impact performance of CNC films was quantified in the context of their specific ballistic limit velocity and energy absorption. Bouligand structures with low pitch angles (18–42°) were found to display the highest ballistic resistance, significantly outperforming other pitch angle and quasi-isotropic baseline structures. Improved energy dissipation through greater interfacial sliding, larger in-plane crack openings, and through-thickness twisting cracks resulted in improved impact performance of optimal pitch angle Bouligand CNC films. Intriguingly, decreasing interfacial interactions enhanced the impact performance by readily admitting dissipative inter-fibril and inter-layer sliding events without severe fibril fragmentation. This work helps reveal structural and chemical factors that govern the optimal mechanical design of Bouligand microstructures made from high aspect ratio nanocrystals, paving the way for sustainable, impact resistant, and multi-functional films.
Abstract Cellulose nanocrystals (CNCs) is a new family of cellulose materials with outstanding mechanical and chemical properties that have been successfully demonstrated to have potential for many applications. Understanding the mechanical behavior of individual CNCs and their interaction at nanoscale is very important for improving the manufacturing process and mechanical performance of the resulting materials at macroscale. However, due to time and length scale limitations for both, experimen...
#1Kaijin Wu(USTC: University of Science and Technology of China)H-Index: 5
#2Zhijun Zheng(USTC: University of Science and Technology of China)H-Index: 19
Last. Yong Ni(USTC: University of Science and Technology of China)H-Index: 26
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Abstract Nacre with a combination of superior strength and toughness is one of the best natural body armors due to its unique brick-and-mortar structure, which is recently regarded as the model system for the lightweight and high impact performance composite design. However, most of the studies of nacreous structure focused on static loadings or simple one-dimensional dynamic load. Our study presents 3D finite element simulation, 3D printing and drop-tower impact testing to reveal the role of in...
Abstract The nature of polymer deformation depends on the ability of the chain segments to respond to the applied load at the imposed loading rate. When the polymer response time is significantly longer than the loading duration, the polymer responds in a brittle manner. Polystyrene, for example, is a brittle, glassy solid at room temperature and absorbs very little energy during deformation. Here we show unexpected, thickness and strain-rate-dependent deformation processes in thin polystyrene f...
Last. Sinan Keten(NU: Northwestern University)H-Index: 34
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Therapeutic agent loaded micro and nanoscale particles as high-velocity projectiles can penetrate cells and tissues, thereby serving as gene and drug delivery vehicles for direct and rapid internalization. Despite recent progress in developing micro/nanoscale ballistic tools, the underlying biophysics of how fast projectiles deform and penetrate cell membranes is still poorly understood. To understand the rate and size-dependent penetration processes, we present coarse-grained molecular dynamics...
#2Jeffrey W. Gilman(NIST: National Institute of Standards and Technology)H-Index: 50
The twisted plywood, or Bouligand, structure is the most commonly observed microstructural motif in natural materials that possess high mechanical strength and toughness, such as that found in bone and the mantis shrimp dactyl club. These materials are isotropically toughened by a low volume fraction of soft, energy-dissipating polymer and by the Bouligand structure itself, through shear wave filtering and crack twisting, deflection and arrest. Cellulose nanocrystals (CNCs) are excellent candida...
Last. Erik Luijten(NU: Northwestern University)H-Index: 49
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With increasing environmental concerns about petrochemical-based materials, the development of high-performance polymer nanocomposites with sustainable filler phases has attracted significant attention. Cellulose nanocrystals (CNCs) are promising nanocomposite reinforcing agents due to their exceptional mechanical properties, low weight, and bioavailability. However, there are still numerous obstacles that prevent these materials from achieving optimal performance, including high water adsorptio...
Last. Jae-Hwang Lee(UMass: University of Massachusetts Amherst)H-Index: 23
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Biological materials have the ability to withstand extreme mechanical forces due to their unique multilevel hierarchical structure. Here, we fabricated a nacre-mimetic nanocomposite comprised of silk fibroin and graphene oxide that exhibits hybridized dynamic responses arising from alternating high-contrast mechanical properties of the components at the nanoscale. Dynamic mechanical behavior of these nanocomposites is assessed through a microscale ballistic characterization using a 7.6 μm diamet...
Last. Sinan Keten(NU: Northwestern University)H-Index: 34
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Abstract Ballistic performance of ultra-thin graphene membranes have recently been investigated at the micro and nanoscale. Two open questions that remain unanswered are, how graphitic plates behave when they can no longer be treated as a thin membrane, and how the projectile shape influences the perforation resistance of plates of varying thicknesses. Through coarse-grained molecular dynamics simulations, we show that beyond a critical plate thickness, a cylindrical projectile penetrates the pl...
Last. Hongxu Wang(UNSW: University of New South Wales)H-Index: 7
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Abstract Nature has a wide range of biological protection strategies that show resilience to impact loading. These strategies also serve certain amount of flexibility that contribute to body movement and locomotion. Consequently, researchers have developed biomimetic engineering structures emulating natural strategies. However, biological entities are often complex and are difficult to replicate with conventional manufacturing technologies. Recent advances in additive manufacturing provide a pat...
Last. Sinan Keten(NU: Northwestern University)H-Index: 34
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Abstract Polymeric films with greater impact and ballistic resistance are highly desired for numerous applications, but molecular configurations that best address this need remain subject to debate. We study the resistance to ballistic impact of thin polymer films using coarse-grained molecular dynamics simulations, investigating melts of linear polymer chains and star polymers with varying number ( 2 ≤ f ≤ 16 ) and degree of polymerization ( 10 ≤ M ≤ 50 ) of the arms. We show that increasing th...
#1Zhaofan Li(NDSU: North Dakota State University)H-Index: 3
#2Wenjie Xia(NDSU: North Dakota State University)H-Index: 20
Abstract Owing to the impressive mechanical properties and renewability, nanocellulose has been increasingly used for the development of lightweight materials in various applications. Here, we present a coarse-grained (CG) modeling study for investigations of mechanical performance of cellulose-based bulk material consisting of disordered cellulose nanocrystals (CNCs), forming a porous network microstructure. The simulation results reveal that increasing density and cohesive interaction between ...
Last. Jiahui Wang(JLU: Jilin University)H-Index: 1
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Abstract The microstructure of the dactyl club of mantis shrimp is mainly divided into two regions, the impact region and the periodic region, which their synergy make the dactyl club have better impact resistance. It is provided innovative inspiration by two regions cooperation for the manufacture of high-energy absorption and impact-resistant fiber composite laminates. In this paper, a novel dactyl-inspired helical-fiber sinusoidal-structure laminate (HSL) was manufactured by unidirectional ba...
Uniaxially arranged nanocomposite structures are common across biological materials. Through efficient structural ordering and hierarchies, these materials exhibit stiffnesses and strengths comparable to the better of their constituents. While much is known regarding the mechanical properties of materials with explicit stiff and compliant phases, substantially less is understood about neat (matrix-free) materials composed from high aspect ratio particles. A promising example of nanoparticle asse...