Nonlinear properties of uni-directional cellulose nanofiber-reinforced poly (lactic acid) composite filaments: a multiscale computational study

In the quest to elevate the mechanical properties of cellulose nanofiber-reinforced poly (lactic acid) composite materials for robust industrial applications, we conducted multiscale nonlinear finite element analysis rooted in homogenization theory. Our study delved into the intricate web of mechanical mechanisms and their pivotal influencers. This paper zeroed in on three paramount factors: the distribution of fibers, the fiber–matrix interface, and the aspect ratio of the fibers. For fiber distribution, we assumed fiber orientation control in fused filament fabrication and clarified the limit of material improvement by setting one-dimensional orientation as the upper limit. Our analysis of the fiber–matrix interface proposed a comprehensive three-scale structure, encompassing microstructures featuring intricate interfacial phases around the fibers, sub-microstructures with myriad dispersed fibers, and macrostructures subjected to external loads. The profound impact of the fiber–matrix interface on material properties was unveiled through a meticulous two-step homogenization process. Furthermore, we examined the substantial influence of the fiber aspect ratio on material properties. By unraveling the complex interplay among these critical factors, this research provided new design guidelines for fiber morphology to the performance of cellulose composites.