Multifunctional ‘core-sheath’ fibers composed of a poly(caprolactone) (PCL) polymer sheath and poly(ethylene glycol) (PEG) fluid core were designed via coaxial electrospinning. Mechanical stretching of the fibers caused a discontinuous dilatancy-like (stiffening) behavior when the cores were composed of a known shear-thickening fluid (PEG and SiO2 particles). Surprisingly, the dilatant behavior persisted even when the shear-thickening SiO2 particles were absent in the PEG liquids. Data from optical microscopy, thermogravametric analysis, dynamic mechanical analysis, and rheology have been employed to gain insights into the interactions between the PCL sheath and the PEG cores, and to assess the role of PEG viscosity. The degree of dilatancy-like behavior was found to correlate with the viscosity of the core PEGs and is discussed in terms of frictional forces experienced by the core and sheath, as well as, the shape and volume changes of the polymer sheath. Furthermore, non-woven fiber mats were tested on their abilities to attenuate different auditory sounds (e.g., white noise, pink noise, frequency steps and sweeps). It is demonstrated that the fiber mats attenuate sound, especially in the lower frequency ranges. Overall, the results reported here demonstrate dilatancy-like behavior in core-sheath fibers for the first time and that minor structural changes in the cores can alter significantly the bulk properties of core-sheath electrospun fibers. Additionally, we demonstrate that these fibers can provide auditory sound damping in which the degree of damping is dependent upon the liquid core.

Dilatancy-like behavior in electrospun polymer fibers with liquid cores: Applications to sound damping

2019 Spring National Meeting

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