Digital image correlation (DIC) analysis of regenerated cellulose (viscose) woven composites: orientation-dependent mechanical properties and poisson’s ratio variations

This study investigates the anisotropic mechanical behavior of plain 1/1 woven regenerated cellulose composites, focusing on the influence of yarn orientation on tensile stiffness and strength, the composite toughness in the form of work of fracture and Poisson’s ratio. The latter of which has not been investigated so far in the context of cellulose multifilament yarns. For this reason, a method using Digital Image Correlation (DIC) was established to provide a 3D high-resolution strain mapping. The results reveal a high sensitivity of the Poisson’s ratio towards changes in yarn orientation making the weaving structure an essential design parameter in the engineering of bio-based lightweight composites. At 0 and 90°, the composites exhibit low Poisson’s ratios (0.08 and 0.12), high stiffness (up to 7.1 GPa), and tensile strength (up to 170 MPa), but display brittle failure modes. Intermediate orientations, particularly 45°, demonstrate higher Poisson’s ratios (~ 0.9), improved work of fracture values (up to 9000 J). Conversely, the 60° orientation shows the lowest mechanical properties, with stiffness and tensile strength dropping to 3.1 GPa and 50 MPa, respectively, due to critical misalignment effects. Seeking an optimum energy uptake for lightweight composites under tensile loads, orientations of 45° should be considered while intermediate orientation of 60° feature adverse strength to toughness relations. The findings contribute to the understanding of regenerated cellulose composites, which offer competitive mechanical properties, biodegradability, and sustainability, making them suitable for lightweight structural applications.