# Fire Behavior of Wood-Glass and Jute-Glass Hybrid Laminates Manufactured by Vacuum Infusion
## 3 Results and Discussion
To further highlight this fact, a parameter widely used in the flame retardancy literature named FIGRA (fire growth rate index) is reported in Table 1. This value is obtained by dividing the pHRR by the time at which this peak is obtained, i.e., the TTP. It is therefore evident that the smaller this parameter is, the better is the behavior. The best performance result is attributed to the WGWGW sample (2.7 \(\pm\) 0.3 kW/m\({}^{2}\)\(\times\) s), which is even better than the G5 sample (3.5 \(\pm\) 0.4 kW/m\({}^{2}\)\(\times\) s). MARHE (kW/m\({}^{2}\)), the maximum average rate of heat emission, is a parameter similar to the HRR that is used in large-scale tests as a single burning item (SBI). Basically, it can be observed that the ratios between the analyzed samples remain the same compared to the pHRR value reported. The best performance was obtained by the G5 sample, with 141 \(\pm\) 11 kW/m\({}^{2}\), and the worst by the neat polyester resin, 492 \(\pm\) 3 kW/m\({}^{2}\). The J5 and polyester samples showed a greater deviation in HRR compared to other laminates, likely due to their higher void content, as reported by [PERSON] et al. [14]. Void spaces within the material can act as pockets for the accumulation of combustible gases, promoting faster and more intense combustion when exposed to heat [27]. Additionally, the presence of voids can alter the heat transfer mechanisms within the material, leading to localized hotspots and uneven combustion. This can result in fluctuations and deviations in the HRR measurements. The voids may also affect the thermal stability and decomposition pathways of the material. The increased void content can facilitate the escape of volatile components and combustion products, influencing the combustion kinetics and heat release characteristics during the test [28]. Figure 4A shows the curves for the total heat release (THR) of the laminates, while Figure 4B shows the statistical differences according to the confidence interval of 95%. It can be seen that the WGWGW hybrid laminate showed statistically higher values (76.5 \(\pm\) 5.8 MJ/m\({}^{2}\)) than the GJGJC (40.2 \(\pm\) 5.1 MJ/m\({}^{2}\)), corroborating the theory that the material present on the surface of the hybrid laminate has a significant influence on heat release. This is evidenced by the presence of glass (an inorganic non-combustible material), which showed lower average values [29]. Finally, the G5 mono-component laminate had statistically lower average values than pure resin (\(-\)78%, 25.1 \(\pm\) 2.3 MJ/m\({}^{2}\)), since pure resin has low fire resistance and tends to release a considerable amount of heat in a short period of time [25]. It is important to emphasize that, despite the resin having low fire resistance, an improvement in combustion performance was observed for all laminates. Even WGWGW, which is an interesting alternative, combining fire resistance with low raw material costs for composites, as well as wood being an environmentally friendly material, reached a reduction of 34% with respect to the neat resin [21; 30]. Figure 5A shows the total smoke release (TSR) curve in relation to time for the different laminates produced, as well as for the pure resin. One of the problems associated with fires is the smoke produced. Smoke means the mixture of pyrolysis products and air near the site of the fire and represents a potential hazard because it interacts with light to obscure vision and probably contains harmful and toxic substances [31]. This makes it interesting to determine the amount of smoke production. In general, for the materials under study, the value of smoke formed was highest for polyester, 7361 \(\pm\) 839 m\({}^{2}\)/m\({}^{2}\), followed by WGWGW, 2873 \(\pm\) 188 m\({}^{2}\)/m\({}^{2}\), and J5, 2484 \(\pm\) 216 m\({}^{2}\)/m\({}^{2}\). Among the hybrid laminates, the best performance was obtained by GJGJC, 1860 \(\pm\) 49 m\({}^{2}\)/m\({}^{2}\); compared to the G5 laminates, it was only \(\sim\)36% higher.