  We investigate with experiments the twist induced transverse buckling
instabilities of an elastic sheet of length $L$, width $W$, and thickness $t$,
that is clamped at two opposite ends while held under a tension $T$. Above a
critical tension $T_\lambda$ and critical twist angle $\eta_{tr}$, we find that
the sheet buckles with a mode number $n \geq 1$ transverse to the axis of
twist. Three distinct buckling regimes characterized as clamp-dominated,
bendable, and stiff are identified, by introducing a bendability length $L_B$
and a clamp length $L_{C}(<L_B)$. In the stiff regime ($L>L_B$), we find that
mode $n=1$ develops above $\eta_{tr} \equiv \eta_S \sim (t/W) T^{-1/2}$,
independent of $L$. In the bendable regime $L_{C}<L<L_B$, $n=1$ as well as $n >
1$ occur above $\eta_{tr} \equiv \eta_B \sim \sqrt{t/L}T^{-1/4}$. Here, we find
the wavelength $\lambda_B \sim \sqrt{Lt}T^{-1/4}$, when $n > 1$. These scalings
agree with those derived from a covariant form of the F\"oppl-von K\'arm\'an
equations, however, we find that the $n=1$ mode also occurs over a surprisingly
large range of $L$ in the bendable regime. Finally, in the clamp-dominated
regime ($L < L_c$), we find that $\eta_{tr}$ is higher compared to $\eta_B$ due
to additional stiffening induced by the clamped boundary conditions.
