(507a) Multiscale Finite Element Simulation of Helically Symmetric Cellulose Nanocrystals in Alginate Fibers

Alginate is a natural polymer isolated from brown seaweed that can be spun into calcium alginate fibers through a wet-spinning process. The fibers are widely used in wound dressings, as they are non-toxic, provide excellent moisture management, and can act as a hemostatic agent due to ion-exchange processes with wound exudate. To improve the relatively low mechanical strength of alginate fibers, cellulose nanocrystals (CNCs) have been incorporated into the wet-spinning process. The processing of these composites can result in spiral alignment of CNCs about the alginate fiber axis. The alignment of the CNCs is dependent upon the CNC loading and the apparent jet stretch of the fiber. In this study, the effect of the CNC alignment on the mechanical properties of the calcium alginate fiber composite is examined using finite element (FE) analysis at two different length scales, 1) at the “micro” level where the CNCs within a representative volume element (RVE) can be considered as aligned with one another, and 2) at the “mesoscale” where the longer-range alignment of RVEs forms a helically symmetric spiral around the alginate fiber axis. The stiffness of the RVE at the micro-level is evaluated using virtual periodic displacements to determine the resulting stresses, and thus the effective stiffness tensor. The effective stiffness at each integration point within the global fiber model is determined by analytically computed rotations of the effective stiffness tensor for a single micro-level RVE, such that the resulting rotations align with the mesoscale spiral symmetry. The correlation of the wet-spinning process control parameters with the predicted composite fiber mechanical properties is investigated.