Dependence of the strength of finger-jointed oak wood blanks on finger length and wood moisture content
DOI:
https://doi.org/10.36930/42265206Keywords:
common oak; finger-jointed blanks; finger joint; wood moisture content; bending strength; structural timber; mathe-matical modelling; regression analysis; design of experiments; circular economyAbstract
The paper presents the results of an experimental study on the influence of technological parameters of longitudinal finger-jointing on the mechanical properties of structural blanks manufactured from common oak (Quercus robur L.). The relevance of the study is determined by the need to improve the efficiency of wood resource utilization through the use of short residual wood in the production of structural components, in accordance with the principles of the circular economy and sustainable manufacturing. Particular attention is paid to determining rational technological parameters that ensure the required bending strength of finger-jointed structural elements. The aim of the study was to determine the effect of wood moisture content and finger-joint length on the bending strength of structural finger-jointed oak blanks, to develop a mathematical model of the process, and to determine the optimal manufacturing parameters. The object of the study was the process of strength formation in longitudinal finger-jointed structural blanks made of common oak wood. The subject of the research was the influence of wood moisture content (6, 10 and 14%) and finger-joint length (20, 35 and 50 mm) on the ultimate bending strength. Experimental investigations were performed using response surface methodology, full factorial experimental design, regression analysis and statistical processing in accordance with EN 310, EN 408 and EN 13353 standards. The results demonstrated that wood moisture content is the dominant factor governing the bending strength of finger-jointed oak blanks. Increasing the moisture content from 6% to 14% resulted in a systematic reduction in bending strength regardless of finger-joint length. The maximum bending strength of 62.19 MPa was obtained at 6% moisture content and a 20 mm finger length, whereas the minimum value of 38.19 MPa was observed at 14% moisture content and a 50 mm finger length. A second-order regression model adequately describing the investigated process was developed. The statistical significance of the regression coefficients was confirmed by Student’s t-test, while the adequacy of the model was verified using Fisher’s criterion. The scientific novelty of the study consists in establishing quantitative relationships between wood moisture content, finger-joint length and bending strength of structural finger-jointed oak blanks, developing an adequate predictive mathematical model and substantiating rational technological parameters for manufacturing high-strength structural products. The practical significance of the obtained results lies in the possibility of applying the developed mathematical model for predicting the mechanical properties of finger-jointed oak components, optimizing manufacturing technology, improving the utilization of residual wood resources and ensuring compliance with the mechanical requirements for structural wooden products
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