Abstract
The energy mitigation properties of buckyballs are investigated using molecular dynamics (MD) simulations. A one dimensional buckyball long chain is employed as a unit cell of granular fullerene particles. Two types of buckyballs i.e. C60 and C720 with recoverable and non-recoverable behaviors are chosen respectively. For C60 whose deformation is relatively small, a dissipative contact model is proposed. Over 90% of the total impact energy is proven to be mitigated through interfacial reflection of wave propagation, the van der Waals interaction, covalent potential energy and atomistic kinetic energy evidenced by the decent force attenuation and elongation of transmitted impact. Further, the C720 system is found to outperform its C60 counterpart and is able to mitigate over 99% of the total kinetic energy by using a much shorter chain thanks to its non-recoverable deformation which enhances the four energy dissipation terms. Systematic studies are carried out to elucidate the effects of impactor speed and mass, as well as buckyball size and number on the system energy mitigation performance. This one dimensional buckyball system is especially helpful to deal with the impactor of high impact speed but small mass. The results may shed some lights on the research of high-efficiency energy mitigation material selections and structure designs.
Highlights
Protection of materials and devices under high-speed impact, whose most critical task is energy mitigation and absorption [1,2,3], poses a major challenge in engineering
Woven fabric composites [5,6,7,8], sandwich structure [9,10,11], metal foams [12,13,14] and nanomaterials [15,16,17,18,19,20,21] are widely used for energy mitigation upon high speed impact, which primarily consume the impact energy through widespread failure or extensive deformation
The major energy mitigation effect results from the stress wave attenuation caused by the reflections among buckyball walls, similar as that found in previous research in granular system [22,25,29,30,43], as well as the van der Waals interactions between buckled layers and similar energy absorption mechanism revealed in carbon nanotubes in Ref. [17,18,44]
Summary
Protection of materials and devices under high-speed impact, whose most critical task is energy mitigation and absorption [1,2,3], poses a major challenge in engineering. Granular material arranging in a chain-like structure [22,23] is attractive for force attenuation, and such a discrete system effectively responds to impact loading via stress wave propagation across various interfaces to reduce the transmitted force. With the development of nanomaterial, carbon nanotubes (CNTs) [21,32] have been one of the promising candidates for impact energy absorption thanks to its ultra-high modulus and strength [33,34,35] Buckyballs, another branch of fullerene family, have high potential for energy mitigation owing to their excellent mechanical properties and unique morphology [36,37]. Buckyballs with various sizes are embedded into the chain system to explore the particle size effect on the energy dissipation ability
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