Figure 3.

Finite element models of a single fiber with a circular cross-section (A) and a terminating fiber (red) within a fiber bundle (B), both shown in the activated condition. The FE models with circular cross-section (A) have a fiber diameter of 80μm, a volume fraction of 75% and have lengths varying from 120μm (L₀/2r₀ = 1.5) and 1.6mm (L₀/2r₀ = 20) at 80μm increments. To create a model based on a histological cross-section (B), we obtained an image at 20X magnification that contained several fibers, and outlined the boundaries of nine adjacent fibers that formed a bundle. The resulting fiber polygons were scaled to create a fiber volume fraction of 75%. The cross-sectional geometry remains constant along the length of the fibers. Hexahedral meshes were created based on the outlines in Ansys 11 (Ansys, Inc. Canonsburg, PA). The model is 120μm long (L₀/2r₀ = 1.5). The terminating (middle) fiber has the same cross-sectional area as the fiber with the circular geometry ( $\frac{\pi }{4}{(80\mu \text{m})}^2$). The middle fiber was constrained in the z direction at one end. All other fibers were constrained in the z direction at both ends.