## 1 Introduction
Reference [26] analysed the properties of OSB board obtained from a mixture of two European species, namely beech and poplar. The general conclusion is that with increasing the content of beech strands will increase the mechanical properties of the board, but the properties of hygroscopicity will decrease. Reference [27] studied the influence of Poisson's ratios on the characteristics of OSB boards and demonstrated that this method can become a criterion for assessing the quality of these boards. Reference [28] investigated the effect of the type of adhesive on the combustion of OSB plates based on the ASTM E69 standard and using thermo-gravimetric analysis (TGA). Based on the results of the research, it was found that the lowest temperature was obtained for the phenol-formaldehyde adhesive. Reference [29] studied the effect of the type of adhesive used in OSB technology for the face and core of the plate, noting that the formaldehyde content was limited to that of solid wood. Other research [30] analyzed several physical-mechanical properties of commercial boards measuring 18 mm thick, for the front and core layers, obtaining values over 40% higher in density and more than 2 times the strengths. These results confirm once again that the front layer of the OSB boards differs considerably from the core layer and is the decisive layer for increasing the strengths. Paper [31] studied the influence of density and content of resin content on the mechanical properties of the boards obtained from fast-growing willow (_Salix viiminalis_). The effect of density on MOR and MOE was better, while the resin content effect was better only for IB. The main characteristics of the strands are the geometric ones (length, width, and thickness, expressed in mm), the specific surface of the strands expressed in m\({}^{2}\)/100 g, the slenderness ratio, and the characteristic of thinness [32]. The main element that gives high resistance to OSB boards is the geometry of the strand used and especially its length, usually around 120 mm. If the thickness of the strands is similar to that used in the classic boards manufacturing from woodchips on average 0.6-0.8 mm, the width of the strands is non-uniform due to their breaking according to the longitudinal plane of minimal resistance of the wood. However, due to the large length of the strands and the use of high-performance cutter with the crown, the strands obtained in OSB technology have a rather large width of 10-12 mm. The slenderness ratio has always been defined as the dimensionless ratio of the length and thickness of the strands and expressed the quality of the strands. In this sense, two strands that have different dimensions but the same slenderness ratio will have the same quality. For example, if it has two strands of different sizes (the first strand with l\({}_{1}\) = 80 mm and t\({}_{1}\) = 0.4 mm and the second strand with l\({}_{1}\) = 40 mm and t\({}_{2}\) = 0.2 mm), these strands will have the same slenderness ratio \(\lambda\) = 200, so they will be of the same quality. Its average values range from 60-120 for the chips used in chipboard technology, from 100-160 for the boards with wide strands and over 160 for the strands of OSB [33]. The thinness characteristic emerged from the desire to take into account the width of the strands (which is also very important in OSB board technology) and was determined as a ratio between the length of the strands and a diameter equivalent to the thickness and width of the strands (Figure 3). The equivalent diameter was determined from the relation of equality of the surface of the circle and of the rectangle. Figure 3: Equivalent diameter of the strands.