Linear Viscoelasticity of Bio-based Composites of Polylactic Acid and Regenerated Cellulose Fibers: Modeling and Experimental Validation

A viscoelastic constitutive relationship of bio-based composites made from polylactic acid (PLA) and regenerated cellulose fibers (RCF) is developed by extending the Halpin-Tsai-Pagano model for linear elastic composites to the linear viscoelastic regime using the correspondence principle. To predict the creep compliance of PLA/RCF composites, the model only requires the constitutive relationships of the constituents, as well as concentration and geometry of the RCF. PLA/RCF composites with different RCF concentration are manufactured using a customized core-shell extrusion process, and creep tests are performed to extract their creep compliances. Good agreement is found between the model prediction and experimental results. The model has the potential to predict the linear viscoelasticity of other types of bio-based composites reinforced by short fibers.