Lower Bound and optimality for a nonlinearly damped Timoshenko system with thermoelasticity

In this paper, we consider a vibrating nonlinear Timoshenko system with thermoelasticity with second sound. We first investigate the strong stability of this system, then we devote our efforts to obtain the strong lower energy estimates using Alabau--Boussouira's energy comparison principle introduced in \cite{2} (see also \cite{alabau}). One of the main advantages of these results is that they allows us to prove the optimality of the asymptotic results (as $t\rightarrow \infty$) obtained in \cite{ali}. We also extend to our model the nice results achieved in \cite{alabau} for the case of nonlinearly damped Timoshenko system with thermoelasticity. The optimality of our results is also investigated through some explicit examples of the nonlinear damping term. The proof of our results relies on the approach in \cite{AB1, AB2}.