$6.)$ Now consider the case where the silicon membrane is glued on top of a supporting rubber substrate having thickness of $1$ mm $,$ forming a composite beam as shown in Fig. $3.$ The neutral axis of the assembly is shown by the dashed line in Fig. $3.$ Recall that both stress and strain are $0$ on the neutral axis.

Fig. $3$: Silicon membrane $($black$)$ on top of rubber substrate $($gray$).$ The neutral axis is shown by the dashed line.

What bending radius $\backslash (\backslash$rho $\backslash )$ would cause failure due to the maximum strain in the silicon membrane exceeding the fracture strain?