1. Dynamic mechanical analysis of fpu bonded beech wood at various temperaturesMartin Capuder, Boris Azinović, Andreja Pondelak, Paweł Rutkowski, Magdalena Szumera, Matthew Schwarzkopf, Arkadiusz Kwiecień, Klaudia Śliwa-Wieczorek, Jaka Gašper Pečnik, 2025, published scientific conference contribution Abstract: This study investigates the dynamic mechanical properties of flexible polyurethane (FPU) adhesives bonded to European beech wood (Fagus sylvatica L.) using Dynamic Mechanical Analysis (DMA) over a range of temperatures and frequencies. Samples included clear beech wood and three-layered composite (beech:FPU:beech). DMA tests were performed using a three-point bending setup at 1 Hz and 10 Hz in the temperature range from -120°C to 140°C. The results demonstrated high thermal stability and strong bonding performance of FPU adhesives on beech wood. Frequency-dependent responses varied among FPU types but resembled the behavior of solid wood at lower temperatures. This confirms the suitability of DMA for evaluating adhesive-wood composite behavior under dynamic conditions. The combination of FPU adhesives and beech wood showed potential for thermally stable and energy-dissipating bonded assemblies.
Keywords: dynamic mechanical analysis, FPU, beech wood
Published in DiRROS: 27.08.2025; Views: 409; Downloads: 192
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2. Natural exposure comparison of timber joints bonded with polyurethane adhesive in two climatic conditionsMartin Capuder, Gary M. Raftery, Weixi Wang, Zubin Karami, Boris Azinović, Andreja Pondelak, Luka Naumovski, Tomaž Pazlar, 2025, published scientific conference contribution Abstract: The increased use of engineered wood in the built environment is attracting much attention because of the significant sustainable attributes. The formation of high quality reliable structural adhesive bonds is essential during the manufacture of such products. This research examines and compares the performance of bonded European beech and Radiata pine subject to natural weathering, comparing untreated, preservative treated and mineralized wood. Bonded joints were naturally weathered in Slovenia and New Zealand, respectively. The fracture energy was evaluated through Mode I fracture tests using the double cantilever beam arrangement at various ageing stages. FTIR analysis was conducted to assess chemical changes in the adhesives and wood substrate. The research provides insights into the interactions between ageing, wood species, and adhesive performance, enhancing timber structures sustainability.
Keywords: durability, weathering, climate, adhesive bond, mode I fracture testing
Published in DiRROS: 27.08.2025; Views: 457; Downloads: 185
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3. Influence of surface preparation and surface topography on tensile shear strength of polyurethane adhesively bonded beech wood single-lap joints : a finite element method approachLuka Naumovski, Martin Capuder, Jakub Michal Sandak, Boris Azinović, 2025, original scientific article Abstract: In this study, the mechanical properties of bonded single-lap joints are analysed by tensile lap shear tests on beech wood. A one-component polyurethane adhesive was used, and three different methods of surface preparation were applied: planing, sanding along the grain, and sanding perpendicular to the grain. Prior to bonding, the wooden lamellae underwent laser scanning to obtain surface profiles, which were then analysed for surface roughness. Scanned surface topographies with their features were integrated into the finite element analysis (FEA) software COMSOL Multiphysics to simulate the lap shear bonding area for different surface profiles and roughness. The FEA model implements linear material models, which represent the adherend and thin adhesive layer, combined with a modified local cohesive zone model for the adhesive bond interfacial forces. The experimental tests were conducted in a dry environment, where a higher surface roughness achieved by sanding correlated with a higher tensile shear strength. This increased surface roughness was attributed to the enhanced mechanical interlocking mechanism. This finding aligns with the FE analysis, which showed that increased surface roughness, micropillars and indentations, led to variations in stress concentration and distribution compared to a smooth surface bond.
Keywords: beech wood, mechanical interlocking, surface modification, polyurethane, finite element modeling
Published in DiRROS: 11.08.2025; Views: 431; Downloads: 194
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4. Mehanske lastnosti lepljenih spojev : vpliv izpostavljenosti in naravnega staranjaMartin Capuder, Boris Azinović, Andreja Pondelak, Tomaž Pazlar, Jaka Gašper Pečnik, Luka Naumovski, 2025, published scientific conference contribution abstract Keywords: bukev, lepljen spoj, FTIR, naravna izpostavitev, mehanske lastnosti lesa
Published in DiRROS: 05.06.2025; Views: 596; Downloads: 234
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