||CMC: Computers, Materials & Continua, Vol. 38, No. 1, pp. 31-41, 2013
||Full length paper in PDF format. Size = 754,056 bytes
||Ceramic matrix composites, modeling, interfaces, toughening.
||Crack deflection and penetration at the interface of multi-wall carbon
nanotube/amorphous carbon composites were studied via molecular dynamics simulations.
In-situ strength of double-wall nanotubes bridging a matrix crack was
calculated under various interfacial conditions. The structure of the nanotube reinforcement
-ideal multi-wall vs. multi-wall with interwall sp3 bonding - influences
the interfacial sliding and crack penetration. When the nanotube/matrix interface
is strong, matrix crack penetrates the outermost layer of nanotubes but it deflects
within the nanotubes with certain sp3 interwall bond density, resulting in inner wall
pullout. With increasing the sp3 interwall bond density, the fracture mode becomes
brittle; the fracture energy decrease while the bridging strength increases and then
decreases. Our results suggest that the outermost nanotube wall can serve as a sacrificial
layer such that the interface may be designed by effectively putting it inside
the nanotubes. Controlling the density of sp3 interwall bond within the multiwall
carbon nanotube makes the transition from brittle to tough failure modes in the
composites even when the matrix/nanotube interface is strong.