## 3 Results and Discussion
### Estimation of Load Carrying Capacity
Thus, for both polymeric materials, the areas under the compressive stress-strain curves, up to the corresponding peak point (see Figure 6), were calculated. After that, these values were substituted into Equation (3). The resulting compressive strengths (\(\sigma_{\text{t}}\)*) of the equivalent materials are equal to \(-175.1\) and \(-90.2\) MPa for the PMMA and the GPPS, respectively. These critical stress values are appealingly close to those achieved from the experimental calibration. Finally, the estimations of the LCCs were derived from the MTS and the MS criteria and using \(\sigma_{\text{t}}\)* as \(\sigma_{c}\) (EMC-MTS and EMC-MS predictions). The results are reported in Table 5.  
In contrast to Table 4, since the values of critical stresses are not obtained from the experimental calibration, the discrepancies for the notch tip radii 0.5 and 4 mm are no longer equal to zero. In addition, for all notch tip radii, the discrepancies are considerably lower, always below 10%. This shows that not only is the EMC capable of estimating the compressive critical stress of the two polymers, but also that both the EMC-MTS and the EMC-MS coupled criteria can outstandingly predict the fracture loads of keyhole notched polymeric specimens under compression loading. Finally, it is worth mentioning that the EMC-MTS criterion has provided conservative predictions of the experimental fracture loads for both PMMA and GPPS, whereas the EMC-MS criterion provided critical load estimations larger than the experimental ones (slightly non-conservative results). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Material** & \(\rho\) **(mm)** & \(\mathbf{P_{avg}}\) **(N)** & \(\mathbf{P_{MTS}}\) **(N)** & \
\begin{tabular}{c} **Discrepancy** \\ **(\%)** \\ \end{tabular} & \(\mathbf{P_{MS}}\) **(N)** &
\begin{tabular}{c} **Discrepancy** \\ **(\%)** \\ \end{tabular} \\ \hline \multirow{4}{*}{PMMA} & 0.5 & 16,753 & 16,753 & 0 & 16,753 & 0 \\  & 1 & 17,306 & 16,832 & \(-2.6\) & 16,793 & \(-2.9\) \\  & 2 & 19,188 & 18,549 & \(-3.3\) & 17,614 & \(-8.2\) \\  & 4 & 20,196 & 20,196 & 0 & 20,196 & 0 \\  & 0.5 & 7179 & 7179 & 0 & 7179 & 0 \\  & 1 & 7526 & 7416 & \(-1.4\) & 7203 & \(-4.2\) \\  & 2 & 8678 & 8532 & \(-1.6\) & 7886 & \(-9.1\) \\  & 4 & 9424 & 9424 & 0 & 9424 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Estimations of LCC derived from the MTS criterion (\(\mathbf{P_{MTS}}\)) and the MS criterion (\(\mathbf{P_{MS}}\)), and the discrepancies between estimations and experimental results (\(\mathbf{P_{avg}}\)). \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Material** & \(\rho\) **(mm)** & \(\mathbf{P_{avg}}\) **(N)** & \begin{tabular}{c} **P\(\_\)cm-MTS** \\ **(N)** \\ \end{tabular} & \begin{tabular}{c} **Discrepancy** \\ **(\%)** \\ \end{tabular} & \(\mathbf{P_{EMC-MS}}\) & \
\begin{tabular}{c} **P\(\_\)cm-MTS** \\ **(N)** \\ \end{tabular} &
\begin{tabular}{c} **Discrepancy** \\ **(\%)** \\ \end{tabular} \\ \hline \multirow{4}{*}{PMMA} & 0.5 & 16,753 & 16,484 & \(-1.6\) & 17,505 & +4.5 \\  & 1 & 17,306 & 16,982 & \(-1.8\) & 18,214 & +5.2 \\  & 2 & 19,188 & 187,08 & \(-2.5\) & 20,594 & +7.3 \\  & 4 & 20,196 & 19,628 & \(-2.8\) & 21,888 & +8.3 \\ \hline \multirow{4}{*}{GPPS} & 0.5 & 7179 & 6919 & \(-3.6\) & 7301 & +1.7 \\  & 1 & 7526 & 7057 & \(-6.2\) & 7681 & +2.0 \\ \cline{1-1}  & 2 & 8678 & 8101 & \(-6.6\) & 9304 & +7.2 \\ \cline{1-1}  & 4 & 9424 & 8669 & \(-8.0\) & 9814 & +4.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Estimations of LCC derived from the EMC-MTS criterion (\(\mathbf{P_{EMC-MTS}}\)) and the EMC-MS criterion (\(\mathbf{P_{EMC-MS}}\)), and the discrepancies between estimations and experimental results (\(\mathbf{P_{avg}}\)). It may be of interest for the reader to know that the authors are currently working on the prediction of the compressive critical loads of notched specimens using a fully analytical approach. This requires determining the critical distances under compression without any experimental calibration.