## 2 Materials and Methods
### Reinforcement of LVL Panels  
Three different types of LVL panels were configured, as shown in Figure 1. The first one corresponds to the control sample, composed of 5 veneers glued with phenol formaldehyde adhesive. The second one corresponds to the carbon fiber-reinforced LVL panel (CFRP-LVL), which have two layers of CF, one between the first and the second veneer and other one on the opposite surface (tension side), and the third panel corresponds to the basalt-reinforced LVL panel (BFRP-LVL), which have two layers of BF, one between the first and the second veneer and other one on the opposite surface (tension side). The purpose of the board being reinforced by only one surface is to allow the user to decide whether or not to leave the fiber exposed.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties** & **Carbon Fiber** & **Basalt Fiber** \\ \hline Fabric & Bidirectional weaving & Bidirectional weaving \\ Thickness (mm) & 0.28 & 0.18 \\ Grammage (g/m\({}^{2}\)) & 200 & 200 \\ Tensile Strength (MPa) & \(\geq\)3500 & \(\geq\)1000 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Properties of the reinforcement fibers used by Aura Industrial data sheets [31].  
Both reinforcement fibers, CF and BF, were impregnated on both sides with ER and PVAc adhesives, forming different samples, while the rest of the veneers were glued with PF adhesive. The difference in the grammage used is due to the different solids content of the adhesives and also to the manufacturer's recommendations. (The experimental design is presented in Table 2).  
Once properly prepared, the panels were subjected to two pressing steps; the first step corresponded to high-temperature pressing, and the second step to cold pressing. The hot-pressing step consisted of subjecting the panels to a specific temperature of 130 \({}^{\circ}\)C, using a three-stage pressing cycle, as illustrated in Figure 2. The objective of the first cycle is to generate adhesion between the wood and the adhesive, the second cycle seeks to consolidate the adhesive, and the third cycle is to prevent the pressure decompression from being abrupt and producing the breakage of the bonding chains (blowing).  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**ID** & **N\({}^{\circ}\) LVL** & **Adhesive Grammage (g/m\({}^{2}\))** \\ \hline P & 4 & 200 \\ ER-CF & 4 & 250 \\ ER-BF & 4 & 250 \\ PVAc-CF & 4 & 400 \\ PVAc-BF & 4 & 400 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Design of experiment.  
Figure 1: The control LVL panel, carbon fiber reinforced LVL, and basalt fiber reinforced LVL panel were configured as follows: (**a**) Control LVL panel; (**b**) LVL panel reinforced with carbon fiber; and (**c**) LVL panel reinforced with basalt fiber.  
Figure 2: Three-stage pressing cycle for both hot and cold pressing.  
After hot pressing, the panels were immediately subjected to the cold pressing stage at an ambient temperature of 20 \({}^{\circ}\)C, under the same pressure and time conditions of the first pressing step (Figure 2). The purpose of cold pressing is to accelerate the adhesive curing process.  
After pressing, the LVL panels were conditioned for 7 days at 23 \(\pm\) 3 \({}^{\circ}\)C and 65% relative humidity. Then, the LVL panels were formatted in 480 mm length \(\times\) 480 mm width and a dimension range of 14.7-15.6 mm thickness and finally cut to the dimensions of each specimen according to European and American standards to determine their physical, mechanical, and thermal properties.