Rheometer

About: Rheometer is a research topic. Over the lifetime, 5759 publications have been published within this topic receiving 125849 citations.

The influence of carbon nanotubes on quasi-static puncture resistance and yarn pull-out behavior of shear-thickening fluids (STFs) impregnated woven fabrics

Abstract: This study focuses on the puncture resistance performance of woven high modulus polypropylene (HMPP) fabric impregnated with shear-thickening fluids (STFs) composed of fumed silica nanoparticles suspended in polyethylene glycol (PEG) and those containing carbon nanotubes (CNTs). The shear-thickening characteristics and rheological features of suspensions were determined at steady and oscillatory shear stress using a stress controlled rheometer. The puncture resistance performance of STF-treated HMPP fabrics were evaluated by the quasi-static puncture test. To gain a better understanding of the effect of these two suspensions on puncture resistance mechanism of fabric, yarn pull-out test was conducted to examine internal shear strength and inter yarn frictional behavior of fabric. The results showed that both the STF-treated fabrics exhibited significant enhancement in puncture resistance performance as compared to neat fabric. However, the fabric impregnated with the suspension containing CNTs showed lower enhancement, due to its lower degree of shear-thickening as confirmed by rheological measurement. The possible improving mechanisms responsible for puncture resistance performance of STF-treated fabrics were also discussed.

Magnetorheology of fiber suspensions. I. Experimental

Abstract: This work reports a detailed study on the shear magnetorheology of suspensions of magnetic microfibers. The steady-state regime was investigated using a controlled-stress rheometer for different concentrations of particles and under the presence of a broad range of applied magnetic fields (up to 512kAm−1). The results were compared with those obtained for conventional magnetorheological fluids (suspensions of magnetic microspheres). It was found that the suspensions of magnetic fibers show an enhanced magnetorheological effect. We proposed the existence of field-dependent solid friction between fibers as the main physical reason for this enhancement. In order to ascertain the relevance of the interfiber solid friction, the microscopic structure of fiber suspensions was investigated using an optical microscope. In the absence of applied field, fibers form an entangled network with approximately isotropic orientation. Upon magnetic field application, the fiber network becomes deformed and approximately alig...

Studies of a Polymer Melt in an Orthogonal Rheometer

Abstract: A method has been developed for measuring three orthogonal forces in a polymer melt subjected to shear. Data are presented showing the relationship of these forces to shear rate for linear polyethylene. It has been found possible to measure the elastic and viscous forces while varying the shear rate in two different independent manners: (1) by varying the time scale of applying a given magnitude of shear deformation; (2) by varying the magnitude of shear deformation for a given time scale of application. Method number one results in the usual nonlinear relationship between shear stress and shear rate for polymer melts. Method number two results in a linear relationship between shear stress and shear rate thus making it possible to determine a single value of the coefficient of viscosity for any given time scale of application of shear strain. By varying the time scale of strain application, it has been found possible to measure polymer melt viscosities from essentially the zero shear rate viscosity to the...

Microfluidic extensional rheometry using stagnation point flow.

Abstract: Characterization of the extensional rheometry of fluids with complex microstructures is of great relevance to the optimization of a wide range of industrial applications and for understanding various natural processes, biological functions, and diseases. However, quantitative measurement of the extensional properties of complex fluids has proven elusive to researchers, particularly in the case of low viscosity, weakly elastic fluids. For some time, microfluidic platforms have been recognized as having the potential to fill this gap and various approaches have been proposed. This review begins with a general discussion of extensional viscosity and the requirements of an extensional rheometer, before various types of extensional rheometers (particularly those of microfluidic design) are critically discussed. A specific focus is placed on microfluidic stagnation point extensional flows generated by cross-slot type devices, for which some important developments have been reported during the last 10 years. Additional emphasis is placed on measurements made on relevant biological fluids. Finally, the operating limits of the cross-slot extensional rheometer (chiefly imposed by the onset of elastic and inertial flow instabilities) are discussed.