## 2 Experimental Test
### Test Setup  
Bending tests measure the behavior of a beam subjected to different loading conditions. They are commonly performed on relatively flexible materials such as polymers, wood and composite materials. At its most basic level, a bending test is performed on a universal testing machine by placing a specimen on two supporting anvils and bending it through a force applied through one or two loading anvils to measure its properties. In the three-point bending test, it balances a specimen between two lower supports while a force centered in the middle is applied by the testing machinery. The uniform stress area is quite small and concentrated below the center point of loading. Different testing standards may require anvils to be fixed, rotated or oscillating. Specifically, the standards governing the performance of these tests are ISO 13061-3, ISO 13061-4 and ASTM D143 [38; 39; 40]. The standards listed above are the most used wood bending tests, but there are many other wood testing standards in various standards bodies, including ASTM, ISO, EN, BS, JAS and JIS.  
Three sets of tests (6 samples for each joint thickness) were performed for all four temperature levels, for a total of 72 samples. The beams consisted of two single lamellas with a cross-sectional area of 40 \(\times\) 20 mm and a length of 420 mm (see Figure 1c). The spacing between the supports was 350 mm. A PTS (model PT 100) thermocouple sensor (VISHAY Electronic GmbH, Selb, Germany) was used to measure the temperature inside the adhesive layer. Due to its small dimensions of 0.45 \(\times\) 0.85 \(\times\) 1.55 mm, this sensor did not disturb the obtained results. The load was applied according to the displacement-controlled method through a Zwicki Roell 1455 universal testing machine (UTM), with a  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Young Modulus E (MPa)/(Ratio (–))**} & \multicolumn{3}{c}{**Shear Modulus G (MPa)/(Ratio (–))**} \\ \hline \(\mathbf{E_{x}}\) & \(\mathbf{E_{y}}\) & \(\mathbf{E_{z}}\) & \(\mathbf{G_{xy}}\) & \(\mathbf{G_{xz}}\) & \(\mathbf{G_{yz}}\) \\ \hline \multicolumn{5}{c}{**20 \({}^{\circ}\)C**} \\ \hline
10611 (1.00) & 531 (1.00) & 531 (1.00) & 757.9 (1.00) & 757.9 (1.00) & 75.8 (1.00) \\ \hline \multicolumn{5}{c}{**40 \({}^{\circ}\)C**} \\ \hline
9761 (0.92) & 488 (0.92) & 488 (0.92) & 697.2 (0.92) & 697.2 (0.92) & 69.7 (0.92) \\ \hline \multicolumn{5}{c}{**60 \({}^{\circ}\)C**} \\ \hline
8763 (0.83) & 438 (0.82) & 438 (0.82) & 625.9 (0.83) & 625.9 (0.83) & 62.6 (0.83) \\ \hline \multicolumn{5}{c}{**80 \({}^{\circ}\)C**} \\ \hline
8334 (0.78) & 417 (0.78) & 417 (0.78) & 595.3 (0.78) & 595.3 (0.78) & 59.5 (0.78) \\ \hline \end{tabular}
\end{table}
Table 1: Elastic modulus of wood experimentally measured.  
load head movement speed of 10 mm/min. Specimens were instrumented with a Linear Variable Displacement Transducer (LVDT) mounted at the center of the beam to measure the displacement. The test stand is presented in Figure 1a.  
Before testing, all specimens were cured for 21 days in a room with a stable temperature of 20 \({}^{\circ}\)C and humidity of 65% \(\pm\) 5%. The adhesive was mixed as described in the product data sheet. The mixing ratio for Sika PS A:B = 100:11 parts by weight. The adhesive was mixed for 60-80 s, and the mechanical mixing speed was 600-800 rpm.