A numerical model for simulating mechanical behavior of flexible fibers

A numerical method is developed for simulating the mechanical behavior of f lexible fibers. A circular crossed fiber is represented by a number of cyli ndrical segments linked by spring dash-pot systems. Segments are lined up a nd bonded to each neighbor. Each bond can be stretched or compressed by cha nging the bond distance. Bending deflection and twist movement occur, respe ctively, in the bending and torsion planes. While the bending angle is dete rmined by the positions of two neighboring bonds, a reference twist vector is introduced to record the torsion motion along the segment chain. Fluid d rag forces are calculated based on the Stokes' Law, where a free draining a ssumption is made. The motion of the fiber is determined by solving the tra nslational and rotational equations of individual segments. Computer simula tion has been conducted to verify the single fiber model with elastic theor y and excellent agreements have been found between the simulation results a nd the theory in various situations such as beam deflection under static lo ads, vibrating cantilevers, and dynamics of helical shaped fibers. Examinin g orientations of rigid fibers in a viscous shear flow, simulation results suggest that the rotational time is sensitive to the fluid drag torque whic h is related to the shape of the segments. For highly flexible fibers, the effect of bending deformation on the period of rotation and the rotation or bits is also investigated. This numerical model for single flexible fibers linked by discrete segments provides a framework in the future studies on f ibrous assemblies. (C) 1999 American Institute of Physics. [S0021-9606(99)5 0347-4].