Surface Ripples of Polymeric Nanofibers under Tension: The Crucial Role of Poisson鈥檚 Ratio
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- 作者：Shan Tang ; Ying Li ; Wing Kam Liu ; Xiao Xu Huang
- 刊名：Macromolecules
- 出版年：2014
- 出版时间：September 23, 2014
- 年：2014
- 卷：47
- 期：18
- 页码：6503-6514
- 全文大小：587K
- ISSN：1520-5835
文摘
Molecular dynamics and finite element simulations are performed to study the phenomenon of surface rippling in polymeric nanofibers under tension. Each nanofiber is modeled as a core鈥搒hell system that resembles most relevant features extracted from detailed molecular simulations and experiments. Accordingly, our model nanofiber consists of a dense glassy core embedded in a less dense, more flexible, rubbery shell. Poisson鈥檚 ratios of the core and shell layers are assumed close to that of compressible and incompressible materials, respectively. Surface rippling of the nanofiber is found, via combined finite element analysis and continuum theory, to be governed by a 鈥減olarization鈥?mechanism at the core鈥搒hell interphase regime that is ultimately induced by the mismatch between Poisson鈥檚 ratios while a mismatch between Young鈥檚 moduli seems to play a secondary role. Plastic deformation is a prerequisite for the formation of rippled surfaces, that evolve from initial imperfections, and grow in the presence of uniaxial tension. For this reason, both strain rate and yield stress greatly influence the onset and modes of the observed rippled surface. Our findings are consistent with experimental observations on surface ripples of electrospun nanofibers and pave the way to design polymeric nanofibers with distinct surface morphologies.