Determination of the screwing torque performance of beech plywood produced with glass fiber reinforced phenol formaldehyde glue

In the study, the effects of the mechanical properties of plywood, which is generally used as a building material in outdoor areas, improved by the addition of low-cost glass fiber, on screwing torques were revealed. In this study, beech veneers of 600x600 mm in size and 2 mm thickness were used in 3-5% humidity, by adding powdered e-type glass fiber in two different sizes, 25 µm and 10 µm, to the phenol formaldehyde glue at the rates of 10, 20 and 30%. 7-layer beech plywood was obtained by applying the resulting mixture homogeneously between the layers at 200 g/m². The determination of screwing torque values was carried out with test samples cut from the obtained plywood in 500x500 mm dimensions. The torque value at the moment when the screw fully contacts the material surface, the "seating torque", and after the seating torque is obtained, the "maximum torque" values just before the moment when the screw rotates idle in the material are obtained in Nm. Test samples cut in 50x50 mm dimensions were used in density, equilibrium moisture content, thickness swelling, tensile-shear and tensile tests perpendicular to the surface. Two-factor analysis of variance (ANOVA) was performed separately for the mentioned tests. According to the ANOVA results of the tests, when the pairwise interactions were found to be significant at the 0,05 significance level, the least significant difference value (LSD) analysis of the pairwise interaction was performed. According to the results, in cases where the bilateral interaction was not significant, comparisons were made by performing LSD analysis on the factors separately.