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Calculation of the Stokes and Aerodynamic Equivalent Diameters of a short reinforcing fiber
Author(s) -
Henn Arthur R.
Publication year - 1996
Publication title -
particle and particle systems characterization
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.877
H-Index - 56
eISSN - 1521-4117
pISSN - 0934-0866
DOI - 10.1002/ppsc.19960130407
Subject(s) - fiber , materials science , particle (ecology) , aerodynamics , aspect ratio (aeronautics) , shape factor , sedimentation , composite material , aerodynamic diameter , stokes number , aerodynamic force , mechanics , mathematics , chemistry , aerosol , geometry , physics , reynolds number , turbulence , geology , paleontology , oceanography , organic chemistry , sediment
A concern about all reinforcing fibers is the extent to which they are respirable. The degree of respirability of a particle is frequently estimated in terms of its aerodynamic equivalent diameter being less than a certain value (typically 3.5 to 7 μ). However, the aerodynamic equivalent diameter, like the Stokes diameter, is only defined exactly for spheres, which is far from the shape of acicular fibers. Thus, it is useful to be able to calculate, based on actual fiber diameter and aspect ratio, the effective Stokes and aerodynamic equivalent diameters of various fibers. The present paper derives simple expression for relating the two effective diameters to actual fiber dimensions. Calculated results are compared with experimental data for glass fiber and three fractions of phosphate fiber [1], which is a short, reinforcing inorganic fiber. Agreement is seen to be good. Phosphate fiber was fractionated using a sedimentation technique described in the paper. The resulting fractions were characterized by semi‐manual measurements of micrographic dimensions and compared with results obtained from particle size instruments based on sedimentation principles. Based on these results, a large weight fraction of phosphate fiber is predicted not to be respirable.