## 3 Results and Discussion
### Mechanical Properties Test
#### 3.1.2 Flexure Test  
The results of the flexure tests are shown in Figure 7c,d and Table 4. As with the compression test, each curve represents the averaged results of each test group. In addition, the asterisks denoting the results of specimens cut with a hot wire and dots representing those cut with a table saw were plotted to display the maximum stress values of four specimens in each test group. This section also studied the influences of density, specimen size, and cutting method, as in the compression test. In ASTM C203, the stress at rupture  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Compression Test**} & \multicolumn{2}{c}{**Flexure Test**} \\ \cline{2-5}
**Test Group** &
\begin{tabular}{c} **Compressive Strength** \\ **(kPa)** \\ \end{tabular} & **Initial Modulus (MPa)** & **Rupture Stress (kPa)** & **Strain at Rupture (\%)** \\ \hline EPS22 * & 167, 164 (1.7, 2.8) & 3.8, 3.7 (0.2, 0.1) & 374, 342 (1.5, 4.9) & 7.0, 8.1 (0.7, 1.2) \\ EPS22 & 168, 165 (5.7, 5.4) & 4.6, 4.7 (0.4, 0.3) & 325, 334 (5.6, 8.8) & 6.9, 6.7 (0.6, 1.2) \\ EPS23 & 181, 177 (4.4, 2.9) & 5.3, 5.2 (0.4, 0.1) & 349, 346 (12.6, 4.6) & 4.9, 5.3 (0.5, 0.2) \\ \hline \hline \end{tabular}  
* The thickness of this test group was 20 mm and all 6 faces were processed instead of only 4 lateral faces for EPS22 and EPS23; meaning in the flexure test, EPS22* had no original surfaces on the tension and compression side, while EPS22 and EPS23 retained the original.  
\end{table}
Table 4: Results of compression test and flexure test on EPS.  
was named modulus of rupture, which could be easily confused with the initial modulus; hence it was denoted herein as rupture stress.  
The rupture stress rises with its density; EPS23 was 7.4% higher than EPS22 if specimens were cut with a hot wire and 3.6% higher if cut with a table saw. With higher density, the material appeared to be brittle, as it ruptured at a lower strain level. The initial modulus of EPS23 was 25.8% higher and 20.3% higher than EPS22 for hot-wire-cut and table-sawed specimens, respectively.  
A comparison between EPS22 and EPS22* showed that the size of the specimen displayed a minor influence in rupture stress and strain at rupture. However, when cut with a hot wire, EPS22* specimens displayed stronger behavior under flexure. Specimens in this group ruptured at similar strain levels but yielded at about 15% higher stress than the others. Connected to the compression test results, one theoretical explanation was that, when cut with a hot wire, a layer of extra thin coating formed in the cutting process with PS beads fused at a high temperature. This coating possessed the high tensile strength of a PS thin film, whereas the strength increased. Considering the difference between cutting methods, apart from abnormal results in EPS22*, the cutting method inconsiderably affected the initial modulus and rupture stress when original surfaces were preserved or cut with a table saw in EPS22. The rupture stress of specimens cut with a hot wire was 2.8% higher than those with a table saw in EPS23. In the flexure test, 3-point bending was adopted in this study. Nevertheless, this was only for the modulus of rupture instead of flexural strength, on account of failure produced by a high shear stress component rather than a simple tension/flexural failure [28]. Hence, 4-point bending is recommended for investigating flexural strength in future studies.