\begin{table}[htbp]
\footnotesize
  \centering
  \small
  %\caption{Model geometries summary.}
    \begin{tabularx}{\textwidth}{cc}
    \toprule
   \midrule
    \textbf{Name} & \textbf{Number of phases}\\
     bounded-RVE&3\\
    \midrule
    \multicolumn{2}{X}{\textbf{Description}}\\
    \multicolumn{2}{X}{Circular fiber inside a square matrix domain, bounded by two UD rectangular domains on the upper and lower side.}\\
    \midrule
    \multicolumn{2}{X}{\textbf{Geometry of each phase}}\\
    \multicolumn{2}{X}{Fiber: circular; matrix: square with circular inclusion at its center; UD: rectangular.}\\
    \midrule
    \multicolumn{2}{X}{\textbf{Boundary conditions}}\\
    \multicolumn{2}{X}{Free surface at $z=\pm l$.}\\
    \midrule
    \multicolumn{2}{X}{\textbf{Imposed conditions}}\\
    \multicolumn{2}{X}{Constant displacement $u_{x}|_{z=\pm l}=\bar{u}_{x}=\bar{\varepsilon}_{x}\cdot l$ at $x=\pm l$.}\\
    \midrule
    \bottomrule
    \end{tabularx}%
  \label{tab:geom_tab2}%
\end{table}%