Details

Autor(en) / Beteiligte

• Galuppi, Laura
• Pasquali, Matteo
• Royer-Carfagni, Gianni

Titel

The effective tensile and bending stiffness of nanotube fibers

Ist Teil von

• International journal of mechanical sciences, 2019-11, Vol.163, p.105089, Article 105089

Ort / Verlag

Elsevier Ltd

Erscheinungsjahr

2019

Link zum Volltext

Quelle

ScienceDirect Journals (5 years ago - present)

Beschreibungen/Notizen

• •Axial and bending stiffness of fibers is much lower than that of the constituent nanotubes.•A micro-macro analytical approach is proposed for nanotube fibers under traction and bending.•Van der Waals interaction among the nanotubes is modeled by shear springs on lateral surface.•The longitudinal offset of the nanotubes and their aspect ratio govern the macroscopic stiffness.•Scaling laws for axial and bending stiffness are in agreement with experimental results. We analyze the pure bending state, preliminarily considering the pure traction problem, for a fiber with circular cross-section composed by monodispersed Nano Tube (NT) segments, whose length is much lower than the length of the fiber, arranged in a cross-sectional square lattice, possibly inclined with respect to the bending plane. The proposed model accounts for the compliant shear coupling of the constituent NTs along their lateral contact surfaces, and considers that the position of each NT is offset with respect to the neighboring ones by a fixed distance. The shearing of the NTs permits their mobility in longitudinal direction, inducing an internal rearrangement, calculated through energy minimization, that affects the macroscopic response. With a micro-macro approach, the internal actions in the whole fiber are calculated. We find that uniform axial macroscopic strain is associated with constant tensile normal force in the fiber and null moment; correspondingly, constant macroscopic curvature provides a constant bending moment in the plane of bending and null axial force. It is then possible to consider the NT fiber as an equivalent homogeneous beam, whose effective tensile and bending stiffness can be calculated, finding a dependence upon the aspect ratio of the fiber, the aspect ratio of the individual NTs and, more important, the offset of the NTs. The model permits to interpret recent experimental results.