Modeling the off-axis tensile nonlinearity of twisted plant fiber reinforced composites fused with hierarchical angles

Aiming at the off-axis tensile nonlinear behavior of twisted plant fiber reinforced composites, hierarchical angle constitutive model was built up by integration of macroscale and microscale methods by considering micro fibril angle of plant fibers, surface twist angle of fiber yarn and off-axis tensile angle of composites. When calculated, this model could only consider the effects of surface twist angle and off-axis tensile angle because micro fibril angle was random, difficult to be measured and less effects to composites' off-axis tensile properties than surface twist angle and off-axis tensile angle. That meant micro fibril angle was assumed to be constant and that model would be simplified. Finally, the model was validated by the experimental data of unidirectional flax fabric reinforced epoxy compo-sites conducted in this research and from the literatures. The calculated results show good agreement with the experimental data.