Influence of cellulose nanocrystal network on the Young’s modulus of polymer composites

Although numerous models have been proposed to estimate the modulus of composites reinforced with cellulose nanocrystals (CNCs), the applicability of the models remains limited, because they often neglect critical factors such as interphase effect and CNC network formation after percolation onset. In this study, these limitations are addressed by developing a comprehensive model that explicitly incorporates both CNC network formation and interphase characteristics. The proposed model is validated against experimental data and exhibits substantial improvements in predictive accuracy compared with previous approaches. Notably, a 400% increase in modulus was achieved at a CNC volume fraction of 0.02 with a mechanical percolation threshold of 0.001. Furthermore, an interphase thickness of 20 nm combined with a CNC radius of 4 nm produced the greatest enhancement, corresponding to a 900% increase over the neat polymer matrix. Similarly, a CNC network with a volume fraction of 0.006 and a network modulus of 6000 MPa yielded a 700% increase relative to the pure matrix. These findings confirm that increasing interphase thickness and optimizing CNC network characteristics markedly enhance mechanical performance. In addition, longer CNCs with smaller radii and optimized filler content effectively reduce the percolation threshold and further strengthen the nanocomposite.