Fig. 1.

a A sketch of all six possible shear modes, $\mathbf{f}$, $\mathbf{s}$, and $\mathbf{n}$ denote the fibre, sheet, and normal direction, respectively. (ij) refers to shear in the j direction within the ij plane, where $i\ne j\in \{\text{f, s, n}\}$. b A sample with fibres (red dash lines), which is stretched along the two orthogonal directions (MFD and CFD) in fibre-normal plane during a biaxial test; c uniaxial tension tests along the MFD and CFD; $f_1$ and $f_2$ are the loading force along the MFD and CFD. L is the initial length of specimen, and ${\lambda }_1$ and ${\lambda }_2$ are stretch ratios