Snubbing effect in atomic scale friction of graphene

Effects of Graphene Nanoplatelet Size and Surface Area on the AC Electrical Conductivity and Dielectric Constant of Epoxy Nanocomposites

“…Compared to pure polymer, an increase of up to 121% in thermal conductivity was observed by Kim et al for GNP-reinforced polymer composites [ 18 ]. More work on evidencing the reinforcing effects of graphene on mechanical, thermal performance, and functionality of composite materials and structures can also be found in [ 12 , 13 , 14 , 15 , 16 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ].…”

Role of Multiwalled Carbon Nanotubes as Shear Reinforcing Nanopins in Quasi-Brittle Matrices

“…Accompanied by the breakage and re-formation of silicon–oxygen (Si–O) atom bonds, a crack grows until it traverses the matrix at u of 20 Å. Figure b shows that MWCNTs modify the crack propagation direction, and the shear deformation indicated by δ in the pSiO 2 -16 system is fully released after crack coalescence, while a certain amount of shear deformation (δ = 95°) remains due to the bridging and snubbing effects of the MWCNTs in the MWCNT–pSiO 2 -16 system. , Moreover, MWCNTs become bent, implying the existence of tensile force in the nanotubes . The stress flow drawn based on the virial stress in the systems (Figure c,d) indicates that the stress concentration (point 2 in Figure d) is generated at the MWCNT–matrix interface in addition to the stress concentration at the crack (point 1 in Figure c,d).…”

“…The higher E p indicates a greater reduction in the magnitude of potential energy, implying more bond breakage and re-formation in the MWCNTs enhanced systemsa finding that is consistent with the larger crack shown in Figure b and Figure S5b,d. In stage II, E n contributes to up to 65% of the dissipated energy in MWCNT–pSiO 2 systems, whereas in the pSiO 2 systems the dissipated energy contributed by E n is less than 45%, mainly because of the enhanced nanofriction caused by the snubbing effect of MWCNTs when they start to work as nanopins. , It should be noted that E n continues to increase in the MWCNT–pSiO 2 systems (stage III), indicating that more energy is consumed due to the nanofriction between MWCNTs and matrix. Until u reaches 120 Å, the nanofriction contributes to about 90–95% of the increment in E w , and the extra breakage of Si–O bonds induced by MWCNTs leads to the other 5–10% of the increment.…”

“…43 Figure 2b shows the modeled crack propagation region where a triple-walled MWCNT with wall diameter of 8.14, 14.83, and 21.5 Å is embedded in a pSiO 2 system with periodic boundary conditions in the x-and y-direction. Considering the snubbing effect between MWCNTs and matrix, 27 MWCNTs in the boundary regions are rotation-constrained. The geometrical dimensions of the region of interest are 90 Å (x-direction), 60 Å (y-direction), and 90 Å (z-direction), and the crack is 22 Å in length.…”

“…Porous-silica (pSiO 2 )-based matrices containing MWCNTs were constructed for atomic simulation. The nonequilibrium molecular dynamics (MD) simulation with a reactive force field was adopted due to its usefulness for accurately quantifying energy consumption during the fracture process. , The novel framework here allows the identification of effective shear reinforcing mechanism and suitable working conditions for MWCNTs in quasi-brittle matrices. This study reveals that the MWCNTs can significantly improve the shear resistance of quasi-brittle matrices due to the shear reinforcing mechanism (snubbing, nanocrack diverging) that is less dependent on the bending stiffness of MWNCT.…”