PSI - Issue 72

Sviatoslav Homon et al. / Procedia Structural Integrity 72 (2025) 301–307

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temperature of the workpieces prior to gluing ranged from 16 to 18 °C. The adhesive was applied evenly in a layer with a thickness of 0.1 to 0.15 mm using a roller. The consumption of resorcinol adhesive was 0.2 kg/m² of the surface area to be bonded. The viscosity of the adhesive was measured using a viscometer, which recorded the flow time (in seconds) for 100 cm³ of adhesive at a temperature of 20 °C. After applying the adhesive to both surfaces of the boards and assembling them into a package consisting of three 10 mm thick boards, they were clamped together with clamps positioned 15 cm apart. During the gluing process, the boards were arranged so that the direction of the fibres aligned properly. The package was maintained in a pressed state for 12 hours. Subsequently, it underwent an additional 48 hours of pressing to ensure the complete curing process was achieved. During the gluing of the wood, the room temperature was set at 200°C, with the ambient humidity levels maintained between 65±5%. Once the bonding process was finalized, the side surfaces of the glued beam were finely processed using a jointer to achieve a desired cross-section of 30x30 mm. For this series of tests, 120 mm long prism samples were cut from a single beam for each type of wood species. The selected length of the prisms (see Fig. 1) was designed to minimize the influence of friction between the testing machine's plate and the ends of the specimens on material strength.

Figure 1. Geometrical dimensions of laminated wood samples

The total number of test specimens was 36. The prisms were tested under axial compression along the fibres with a short-term load of 12% humidity using a STM-100 testing machine (DSTU 3129: 2015; EN 380: 2008; ASTM D 143-14: 2014). The deformation rate was 1.5 mm/min. 3. Methodology of theoretical research The determination of relative critical deformations in wood is proposed to involve the sum of the relative elastic and plastic deformations, as expressed in the following formula: u c,0,d =u c,el +u c,pl . (1) Based on our experimental studies, formula (1) can be reformulated as: ,0, = ,0, / 0 + 1 ∙ 2 ,0, . (2)