38 research outputs found
The shear viscosity of carbon fibre suspension and its application for fibre length measurement
The viscosity of short carbon fibre suspensions in glycerol aqueous solution was measured using a bespoke vane-in-cup viscometer, where the carbon fibre has an aspect ratio from 450 to 2209. In the semi-concentrated regime, nL3 ranging from 20 to 4400, the suspensions demonstrated strong shear-thinning characteristics particularly at higher concentrations. The shear-thinning characteristic is strongly related to the crowding factor proposed by Kerekes, indicating that non-hydrodynamic interactions occur in the suspensions. The influence of fibre bending on viscosity emerges when the bending ratio is lower than 0.0028. An empirical model based on transient network formation and rupture was proposed and used to correlate the relative viscosity with fibre concentration nL3 and shear rate. Based on the model, a viscosity method is established to analyse the fibre length by measuring the viscosity of the fibre suspension using a bespoke vane-in-cup viscometer
A numerical study of the rheological properties of suspensions of rigid, non-Brownian fibres
Epoxy-steel fiber composites : a simple model to predict the fiber sedimentation
Sedimentation of short steel fibers (SSFs) is an important
phenomenon observed in the manufacture by
casting of polymer/metal composites. Modeling of the
fiber sedimentation has been a subject of research but
hardly applied in the context of injection molds. In this
study, the sedimentation velocity of the SSF suspension
in nonreactive epoxy resin was evaluated theoretically
and experimentally. The sedimentation behavior
of single and concentrated SSF in epoxy resin was followed
experimentally to obtain the terminal and sedimentation
velocities. These data were interpreted
using theoretical models that take into account the
hindered settling factor and the shape factor. The experimental
data can be correlated with the theoretical
analyses. The findings were used to propose a simple
model to predict the sedimentation of steel fibers in
viscous resins that are used in composites for making
molding blocks.Portuguese Foundation for Science and Technology,
Brazilian Ministry of Education (Covenant FCT-CAPES
Three-dimensional Monte Carlo simulations of the dynamics of macromolecular particles in solutions flowing in mesopores
Using a Mass Balance to Determine the Potency Loss during the Production of a Pharmaceutical Blend
The manufacture of a blend containing the active pharmaceutical ingredient (API) and inert excipients is a precursor for the production of most pharmaceutical capsules and tablets. However, if there is a net water gain or preferential loss of API during production, the potency of the final drug product may be less than the target value. We use a mass balance to predict the mean potency loss during the production of a blend via wet granulation and fluidized bed drying. The result is an explicit analytical equation for the change in blend potency a function of net water gain, solids losses (both regular and high-potency), and the fraction of excipients added extragranularly. This model predicts that each 1% gain in moisture content (as determined by a loss on drying test) will decrease the API concentration of the final blend at least 1% LC. The effect of pre-blend solid losses increases with their degree of superpotency. This work supports Quality by Design by providing a rational method to set the process design space to minimize blend potency losses. When an overage is necessary, the model can help justify it by providing a quantitative, first-principles understanding of the sources of potency loss. The analysis is applicable to other manufacturing processes where the primary sources of potency loss are net water gain and/or mass losses