## Materials and Methods
### Fracture Tests  
All notched and cracked samples were tested by using a universal test machine. The tests were carried out by displacement control conditions. The speed of the crosshead was fixed at 0.5 mm/min for all tests, which were continued until final fracture and separation of the two halves of the samples. An LS-20 load cell (2000 kgf), with a maximum error of 0.5% in the range of 2-100% of the nominal capacity was utilized. A load cell with a capacity of 500 kgf was also employed to enhance the accuracy of measurements for smaller specimens with nominal radii R5 and R10 mm. Figure 1: Schematics of the fracture samples: (**a**) RVNBD; (**b**) RVNSCB. The load-displacement curve for each test was recorded, as shown in the example of Figure 3. The load-displacement curves were nearly linear until final fracture, except at the initial moment when a slip occurred between the upper fixture roller and the BD and SCB samples, with no effect on the fracture load. It is noteworthy that experiments on the SCB samples were conducted with two different fixtures due to the different nominal dimensions of SCB specimens. In other words, the two largest specimens (i.e., samples with R = 20 and 35 mm) were loaded using one fixture, while the two smallest ones (i.e., samples with R = 5 and 10 mm) were tested using another fixture with sharper edges. Tables 2 and 3 show the fracture loads P\({}_{\mathrm{f}}\) in all the tested specimens (cracked and notched, respectively). Figure 2: Schematic of scaling on the nominal radius of BD and SCB specimens containing crack and RV notch. In addition, Figure 4 shows an example of fractured RVNBD and RVSCB specimens of GPPS and PMMA materials. It can be observed how cracks propagated along the bisector line of the initial notch in RVNBD and RVSCB samples. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Specimen** & **Material** & **Specimens Radius, R** &
\begin{tabular}{c} **Crack Length** \\ **(a or d)** \\ \end{tabular} & \(\mathbf{P_{f1}}\) & \(\mathbf{P_{f2}}\) & \(\mathbf{P_{f3}}\) & \(\mathbf{P_{f,average}}\) \\ \hline \multirow{8}{*}{CBD} & \multirow{4}{*}{PMMA} & 5 & 5 & 791.0 & 761.0 & 708.5 & 753.5 \\  & & 10 & 10 & 1058.0 & 1170.5 & 1148.0 & 1125.5 \\  & & 20 & 20 & 1679.5 & 1713.0 & 1572.0 & 1654.8 \\  & & 35 & 35 & 2345.0 & 2277.5 & 2109.5 & 2244.0 \\ \cline{2-7}  & & 5 & 5 & 524.5 & 564.0 & 586.0 & 558.2 \\  & & 10 & 10 & 972.0 & 991.0 & 895.5 & 952.8 \\  & & 20 & 20 & 1573.5 & 1473.0 & 1604.5 & 1550.3 \\  & & 35 & 35 & 2232.0 & 2168.0 & 2008.0 & 2136.0 \\ \hline \multirow{8}{*}{SCB (S/R = 0.8)} & \multirow{4}{*}{PMMA} & 5 & 2.5 & 210.0 & 196.5 & 209.0 & 205.2 \\  & & 10 & 5 & 377.3 & 370.5 & 339.5 & 362.4 \\ \cline{1-1}  & & 20 & 10 & 528.8 & 558.5 & 551.5 & 546.3 \\ \cline{1-1}  & & 35 & 17.5 & 773.5 & 709.7 & 765.0 & 749.4 \\ \cline{1-1} \cline{2-7}  & & 5 & 2.5 & 129.5 & 121.7 & 130.2 & 127.1 \\ \cline{1-1}  & & 10 & 5 & 212.5 & 232.0 & 236.0 & 226.8 \\ \cline{1-1}  & & 20 & 10 & 402.0 & 424.0 & 419.2 & 415.1 \\ \cline{1-1}  & & 35 & 17.5 & 596.5 & 547.5 & 590.0 & 578.0 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: The fracture loads of polymeric (PMMA and GPPS) CBD and SCB samples at various scales (dimensions in mm, load values in N). Figure 3: Typical force–displacement curves obtained from the RVNBD and RVSCB polymeric specimens with R = 35 (mm).