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Study of Physical and Mechanical Properties of Post-Consumer Wood of Different Age

Gayda Serhiy, Kiyko Orest

Drewno : prace naukowe, doniesienia, komunikaty

2023

Vol. 66, nr 212

Art. no. 177453

It should be noted that there is currently a problem with wood resources in the woodworking industry. A potential, unused wood reserve is post-consumer wood (PCW). The problem with the quality of this wood resource has not been fully resolved since there is no regulatory database. In fact, there is a lack of appropriate regulatory documents, which makes it impossible to describe to a full extent the physical and mechanical properties of PCW of common wood species of different ages as a source of additional raw materials for various woodworking technologies. Proceeding from the goal, the task of the study is to describe the physical and mechanical properties of postconsumer wood using the example of fir wood, which for a long period of time has been used to create furniture and joinery products. The task is also to identify patterns of change in the indicators of this resource with age - an expired service life or suitability. In order to use PCW in woodworking and to fill the scientific base with physical and mechanical indicators of fir wood of different ages with an expired product service life, the following characteristics were investigated: static hardness, swelling, coefficients of swelling, the value of transverse anisotropy, density, static bending strength, splitting strength along the fibers, modulus of elasticity in compression, and the modulus of elasticity in static bending. The characteristics of PCW of the widespread fir species in the range of use from 0 to 20 years were explored, with intermediate control over the properties every 5 years. The dynamics of the physical and mechanical indicators of fir PCW were revealed and it was found that in the course of operation time in various conditions they change, mainly decreasingly: static hardness by 9.2-9.6%; the value of transverse anisotropy by 30-32%; strength: static bending strength by 3.4-7.95%, splitting strength by 4.49-8.67%; modulus of elasticity: in compression by 3.89-4.08%, in bending by 2.75-6.64%. The main causes of changes in the properties of PCW with age: natural: weathering, partial internal rot, insect damage, other biological effects; mechanical: splitting, scratches, small holes from means of fastening and other defects due to use; operational: the influence of power and dynamic loads, the influence of surface finishing agents and other factors on the structural elements of wood products. A summary table was compiled for the selection of indicators of the physical and mechanical properties of fir PCW of different ages. When knowing the indicators and dynamics of the physical and mechanical properties of PCW with age, it can be recommended for manufacturing structural materials - blockboards and furniture panels.

The investigation of properties of blockboards made of post-consumer wood

Gayda Serhiy, Kiyko Orest

Drewno : prace naukowe, doniesienia, komunikaty

2020

vol. 63, nr 206

77--102

Today in woodworking, there are problems with the use of wood waste and the accumulation of involved wood as an additional and not fully used resource. The problem has not been completely solved, as there is no scientific basis and practical recommendations for efficient production processes with predicting the properties of products made from Post-Consumer Wood (PCW), in particular in the production of blockboards (BB). The objective of the studies is to substantiate and develop a scientific and technical basis for resource-saving and environmentally friendly technologies, to establish the influence patterns of PCW properties on the mechanical characteristics of the products obtained, to develop operating parameters and to formulate practical recommendations, confirmed by the results of experimental studies. The studies have proved the expediency of using PCW in technological processes of woodworking, in particular in the production of construction materials - blockboards with predicted characteristics. In order to rationally use raw materials for the manufacture of conventional blockboards made from Post-Consumer Wood (PCW-BB), new designs of a conventional PCW blockboard with a thickness of 22 mm and with a unified strip width of 16, 32, 48, and 64 mm, the strips are glued ones, 3 mm thick, and faced with plywood on both sides. The authors of the article found that in order to ensure improved operating characteristics of the blockboards, it is important to lay radial, semi-radial and tangential strips in structures with the ratio of width to thickness of the cross-sections of the strips - rationally and efficiently - 1:1, 2:1, 3:1. Substantiation on this basis of new designs of PCW blockboards makes it possible to reveal shortcomings of these products at the conceptual stage of the project and correct them before manufacturing taking into account the specified technical conditions and reducing costs at the development stage. Mathematical models for predicting the main characteristics of conventional PCW blockboards (PCW-BB) have been constructed, which made it possible to determine the indexes of the bending strength of the BB across the strips, σBB, and the shear strength of the BB along the glue line, τВВ. The coefficients of approximation of mathematical dependencies for predicting the strength of PCW-BBs, the strips of which were made of fir wood, were calculated, which would allow for the selection of rational designs of blockboards with appropriate characteristics. It has been established that the developed mathematical models make it possible to predict the characteristics of the PCW-BB depending on the cross-sectional dimensions of the strips, the angle of the annual rings slope to the blockboard face and the age of the PCW, and, on this basis, to propose improved designs of these blockboards for the technological processes of woodworking. The influence patterns of the properties of structural elements on the indicators of conventional PCW-BB (500 × 500 × 22 mm) were experimentally established. It was found that an increase in the width of the strips leads to a decrease in the strength indexes (by 29-37%); an increase in the angle of the annual rings slope to the BB face leads to an increase in static bending strength (by 31-33%) but to a decrease in shear strength (by 4-7%); an increase in the age of the PCW leads to a decrease in strength indexes (by 3-8%). It was found that the physical and mechanical parameters of the experimental PCW-BBs with a strip cross-sections of 1:1, 2:1, 3:1 meet the requirements of the standard (larger values: for static bending of a rate of 15 MPa and for shearing at a rate of 1 MPa), and for the 4:1 cross- -section, they partially had lower indexes by 2-3%. To ensure the strength of the developed structures of the PCW-BBs, it is recommended to use the 3:1 ratio of the sides in the cross-section of the strips, and the slope of the annual rings to the blockboard face must be at least 45o. It was found that the deviation of the values obtained by mathematical models in determining the strength in static bending and shearing in comparison with the experimental ones did not exceed 8% and 10%, respectively.