Influence of microfluidic flow rates on the propagation of nano/microcracks in liquid core and hollow fibers

  • Mohammadreza Naeimirad, Ali Zadhoush, Rasoul Esmaeely Neisiany, Seeram Ramakrishna, Saeed Salimian, A. Andres Leal
  • Theoretical and Applied Fracture Mechanics, August 2018, Elsevier
  • DOI: 10.1016/j.tafmec.2018.04.001

Influence of microfluidic flow rates on the propagation of nano/microcracks in liquid core

What is it about?

Therefore, the purpose of the present work is to study the conditions leading to the leakage of a liquid through the polymer sheath of melt-spun LCF and hollow fibers. For this, a newly developed specimen preparation technique is employed which, in combination with a microfluidics pump, allows to analyze the crack propagation phenomenon. The differences in crack propagation behavior observed for the two fibers under analysis are discussed.

Why is it important?

 Liquid core and hollow fibers were spun from polypropylene and complex ester using multicomponent high-speed melt-spinning pilot plant.  A new technique was developed for bundling melt-spun filaments and attaching to the microfluidic pump.  Nano/microcrack-induced leakages during the microfluidic trials were used for crack analysis on fine polymeric fibers.  Liquid core fibers showed less nano/microcracks compare to the hollow fibers.

Perspectives

Saeed Salimian

Liquid core and hollow fibers were produced using a melt-spinning process. The internal micro channels of the fibers were employed as a new media for microflow, developing a bundling technique and attaching the fiber bundles to a microfluidic pump. The microflow and leakage behavior of the hollow fibers and LCFs were investigated by means of microfluidic tests and the fracture mechanisms were identified via SEM images of the fractured surfaces. Microfluidic tests indicated that most of the cracks appear in the early stages (low flow rates) of the microfluidic studies. Moreover, LCFs showed a lower number of leakages compared to the hollow fibers. The strengthening and toughening of the LCFs is a result of the thicker sheath walls and the damping properties of the core liquid already present in the fiber. From the SEM images, the main mechanism of crack propagation involves the type I (opening mode) initiated by the mechanical loads during operation in addition to residual stresses, where the cracks are formed preferentially in the axial direction. Optimization of the fiber spinning process can certainly lead to a significant reduction of the already very low proportion of cracks appearing in these fibers. Future work will include a parametric study to analyze the relation between fiber spinning parameters and crack formation, where the insights gained on nano/microcrack formation and propagation will allow to perform an optimization of fiber spinning parameters.

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http://dx.doi.org/10.1016/j.tafmec.2018.04.001

The following have contributed to this page: Saeed Salimian