PSI - Issue 59

Sviatoslav Homon et al. / Procedia Structural Integrity 59 (2024) 545–550 Sviatoslav Homon et al. / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Wood is an organic material with specific mechanical properties (Landis et al. (2002); Gomon et al. (2023); Da Silva and Kyriakides (2007); Green and Kretschmann (1992)). The popularity of materials, products and structures based on wood is growing rapidly (Rudavska et al. (2018), Gomon et al. (2019); Huang et al. (2006); Galicki and Czech (2005)). On the other hand, global stocks of industrial hardwood, softwood and tropical species are falling. At the same time, trees of a younger age remain in the forests. Forest restoration is taking place at a slow pace in many countries of the world. Therefore, in many cases, people are forced to use younger wood. In particular, it can be used in enterprises of the furniture and woodworking industries (Rudavska et al. (2018), Pinchevska and Zavialov (2020); Horbachova et al. (2023)), in the sphere of industrial and civil engineering (Gomon et al. (2022); Sobczak- Piastka et al. (2020); Zhou et al. (2018); Nsouami et al. (2022); Pavluk et al. (2023)), shipbuilding, in the manufacture of musical instruments and many other sectors of the world economy (Bosak et al. (2021); Gomon et al. (2022); Thygesen et al. (2010); Sobczak- Piastka et al. (2023)).

Nomenclature σ с

compressive stress of wood along the fibers

relative compression deformations of wood along the fibers

u c Е 0

initial elasticity modulus of wood

ultimate compressive strength of wood along the fibers relative critical compressive deformations of wood along the fibers relative residual (final) compression deformations of wood along the fibers

f c,0,d u c,0,d u c,fin

At the same time, wood-based materials, products, details, elements, and structures (Zhao et al. (2020); Soriano et al. (2016); Donadon et al. (2020)) can easily compete with concrete (Dvorkin et al. (2021); Iskhakov et al. (2022)), reinforced concrete (Kovalchuk et al. (2022), Masiuk et al. (2018); Mel’nyk (2016)) and other composites (Imbirovych et al. (2023); Mikulich (2023)). Most of the experimental studies related to the influence of age on the main properties of wood were conducted at the beginning and in the middle of the last century. However, there are few such studies, and they are mentioned only in wood reference books (Bojok and Vintoniv (1992)). Therefore, it is necessary to conduct experimental studies of coniferous and deciduous wood species of standard moisture content of different ages on modern testing machines. Moreover, it establishes the influence of the age factor on the principal strength and deformation parameters. In our previous works, complete diagrams of the deformation of some conifers and hardwoods of 60-year-old solid wood under the action of active water (Homon et al. (2023), Janiak et al. (2023)) and acid environments (Homon et al. (2023)) have already been plotted The main mechanical properties were also determined. This work aims to conduct experimental studies of conifers of different ages of standard humidity under axial compression along the fibers and establish the main mechanical parameters based on full deformation diagrams. 2. Methods of experimental research A series of samples of the 1st grade of solid wood of structural dimensions of conifers in the form of prisms with a cross-section of 30x30x120 mm were produced. In particular, larch is grown in the Ukrainian forests of the Ivano Frankivsk region, pine is grown in the forests of the Rivne region, and spruce is grown in the forests of the Volyn region. So, trees aged 20±2, 40±3, 60±5 years were selected for experimental research. Trees with a smooth trunk and few branches were chosen. This made it possible to reduce the knotting of the wood and increase the parallelism of the fibers. After cutting the selected trees, the trunks were transported to carpentry shops and cut into beams. Wood blanks were dried in special drying chambers to a moisture content of 12±1%. The moisture content of the wood was monitored using a hygrometer. Samples were sawn from previously prepared long bars. Each of the received samples was without visible defects. The prisms were manufactured according to current standards (ASTM