The aim of the present paper is to assess the non-destructive indicating properties of Slovenian beech (Fagus sylvatica) logs and correlate them with the mechanical properties of the final product, which is boards. Beech logs were visually graded according to the standard procedure and vibrational frequencies were measured. Logs were further on sawn into boards which were also non-destructively tested in wet and dry conditions. Finally, the boards were experimentally tested in tension. Special focus was directed towards visual parameters of the beech logs and their influence on the overall quality of the output material. The longitudinal natural frequencies of the logs were studied as potential indicating properties. The results showed that a majority of the visual log grading parameters do not result in good quality timber in terms of strength and stiffness properties, and only few are decisive for the final classification. The coefficient of determination of the static MOE vs. dynamic MOE of logs was r2=0.13, whereas vs. the MOE of wet boards was r2=0.49. Using a few visual characteristics in combination with dynamic measurements of logs and of wet boards could help to increase the yield of high quality beech wood.
Beech wood has high mechanical properties, therefore the production of high quality beech glulam beams is one of our main objectives. Finger joints with standard geometries and adhesives used for joining coniferous wood are not sufficient in terms of strength when gluing beech wood. A hybrid glulam beam was produced and tested in a standard four point bending test. The beam was produced from finger joined beech lamellas on the outer sides and finger joined spruce lamellas in the middle. The results from the bending test showed a lack of tensile strength of the finger joints of beech lamellas on the bottom middle part of the beam, where the rupture occurred. We prepared a numerical model of finger joined beech lamellas and simulations of tension tests, parallel to the lamella. We performed parametric studies with multiple variables referring to geometrical properties of finger joints and two different types of applied adhesives. The results showed a high influence of the finger joint geometrical parameters. Experimental tests on the tension strength of the finger joints were performed. Two finger joint lengths were tested, 10 and 20 millimetres. The results showed a clear influence of the finger joint geometry where highest strengths were obtained with longer and thinner fingers.
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