## 4 Discussion  
Although some authors [15; 26; 27] have established that pine wood (or softwoods, in general) is the most used species in the OSB industry, through the experiments performed in this paper, it was found that the mixture of some fast-growing species has properties as good as those of softwoods, sometimes even better than them. This is explained by the fact that fast-growing species are soft species with a medium density, and their mixture leads to superior chip compaction within the OSB. These species approach a structure with the juvenile wood of some woody species, such as eucalyptus [16]. In the  
Figure 8: Internal bond of OSB panels from mixed species compared to OSB/3–Krono.  
Figure 7: Interval plot of internal bond for the analyzed types of OSBs.  
same sense, some authors [10] have shown that the mixture of aspen and birch creates much stronger boards than pine, and other authors [23] have observed that boards obtained from a mixture of species are more dimensionally stable than those obtained from a single wood species.  
The density of OSBs in this work was 740 kg/m\({}^{3}\) for the softwood mix and 714 kg/m\({}^{3}\) for the hardwood mix, noting that at the same pressure, the hardwoods are less compressible by about 3.5%. These values are comparable to those found by other authors [30], with 750 kg/m\({}^{3}\) for pine OSBs or 650 kg/m\({}^{3}\) for balsa wood [7]. Absorption and swelling are up to 36% and 25% better in the hardwood mix than in the softwood mix, respectively. Regarding the resistance module, the OSBs resulting from softwoods are up to 25.5% better than those obtained from the hardwood mix, but the homogeneity of the resistance (obtained by the difference between the resistance on the major and minor axes) is much better in the case of the hardwood mix (4 N/mm\({}^{2}\)) than the softwood mix (27 N/mm\({}^{2}\)).  
One of the major problems of the chipboard industry is that an increase in the density of the boards will cause the mechanical properties of the boards to increase accordingly. Therefore, an analysis of the correlation of mechanical properties with board density was considered appropriate. The influence of density on the physical and mechanical properties of OSB panels is presented in Figure 9. Multiple comparisons of measured properties were made, and the applied method is Dunnett's, which allows us to determine the confidence levels for each individual comparison.  
Figure 9: Comparative analysis of OSB panel properties from mixed species of softwood (**a**) and hardwood (**b**).  
The analysis indicates that the density is highly significant in determining MOE values of OSBs manufactured from both mixed species.This can be explained by the fact that the elasticity of the boards is also dependent on other factors (wood elasticity, adhesive content, chip length) than the strength and thickness properties [38]. When the strength is higher, the modulus of elasticity is lower. For the other analyzed properties, there is no significant difference. Similar results indicate that MOR, MOE, IB, and WA were well correlated with board density, whereas the relationship between TS and density was less certain.  
As a general conclusion of the whole work, it can be mentioned that the mixture of hardwood species has similar properties to those of the softwood mixture and is, with regards to the mechanical properties, a little better than them. This makes it possible to use these hardwood species in large quantities in the case of the raw material recipe that is used in the current conditions at Kronospan Brasov (over the percentage of 5-8%). Additionally, less expensive alternative solutions can be found [15], adopting the gradual or total replacement of softwood species with a mixture of fast-growing hardwoods, thus reducing the pressure currently exerted on softwood species.