PSI - Issue 36

Petro Yasniy et al. / Procedia Structural Integrity 36 (2022) 211–216 Yasniy Petro et al. / Structural Integrity Procedia 00 (2021) 000 – 000

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1. Introduction Wood is an indispensable material of natural origin, used in various sectors of the world economy, including industrial (Gomon et al. (2020), Zakic (1974), Zhou et al. (2018)), civil (Sobczak-Piastka et al. (2020)) and hydraulic engineering, bridge construction, machine building, shipbuilding, woodworking and furniture industries (Pinchevska et al. (2021)) and many others. But in recent years, the demand for wood is constantly increasing, the world's forest resources are declining. On the other hand, materials, products, parts, elements and structures must be of increased strength. In order to improve such properties of wood, it must be modified. Modification can be surface or deep.

Nomenclature σ с

compressive stress

relative tensile strains of modified wood along the fibers

u c

relative tensile strains of modified wood along the fibers to the end of the 1-st section

u c1

σ с 1 tensile stress of modified wood along the fibers to the end of the 1-st section E 0 initial modulus of elasticity f c,0,d ultimate strength of modified wood u c,0,d relative ultimate tensile strains of modified wood along the fibers η stress level E strain modulus (secant modulus) u c,el, elastic component of relative tensile strains of modified wood along the fibers u c,0,d plastic component of relative strains of modified wood along the fibers u c,0,d ultimate relative tensile strains of modified wood along the fibers σ с,u stress of modified wood that correspond the ultimate relative strain u c,fin residual (final) relative strains of modified wood σ с,fin stress of modified wood that correspond the residual (final) relative strains r correlation ratio m r average error of correlation ratio V variation ratio

Mechanical properties of different species of solid wood have been studied quite precisely (Da Silva and Kyriakides S. (2007); Conrad et al. (2003); Davids et al. (2003); Galicki and Czech (2005); Green and Kretschmann (1992); Landis et al. (2002), Mackenzie-Helnwein et al. (2003); Madsen (1975); Patton-Mallory and Cramer (1987); Sinha et al. (2012)), in particular the compressive or tensile strength of wood along the fibers, the initial modulus of elasticity, deformability and others. On the other hand, it is necessary to study the properties of newly formed hardwood- and softwood-based composite materials. In this article, the behaviour of composite hardwood based material (birch, alder, ash and polymer composition ‘ silor ’ ) is to be analyzed, as well as the main strength and strain characteristics will be given. 2. Methods of experimental research The following hardwood species were used for experimental research: birch, alder, ash. The cross-section of the twin-prisms was 30x30x120 mm. The samples were made in the factory. Prisms were cut from long beams, which were prepared and dried to a standard moisture of 12%. Moisture was measured with a moisture meter MD-814. There were 6 samples for made each species of wood. The age of all studied wood species was approximately 60 years. The twin prisms were naturally impregnated with the polymer composition ‘ silor ’ without additional stimulation. Wood samples were placed in a vessel with a polymer composition for 12 hours. The experimental prisms were completely immersed in the polymer solution in a horizontal position, without contacting the walls of the vessel and each other.