The adhesive bond properties of laminated wood made of thermally modified beech wood

Bukovina ima kljub dobrim mehanskim lastnostim še precej neizkoriščen potencial v leseni gradnji. Ima visoko gostoto in je zelo trdna, vendar pa tudi biološko neodporna in dimenzijsko nestabilna. Te nezaželene lastnosti lahko zmanjšamo s postopkom termične modifikacije. Bukov les lahko tako uporabimo tam, kjer je bila njegova uporaba do sedaj omejena. Lesu se po termični modifikaciji poslabšajo nekatere mehanske lastnosti, prav tako se mu spremenijo določene lastnosti, ki lahko vplivajo na kakovost lepilnih spojev. Namen diplomskega dela je bil ugotoviti, ali bodo lepilni spoji lameliranega lesa iz termično modificirane bukovine dosegli zahteve standarda SIST EN 14080:2013. Zanimal nas je tudi vpliv predpremaza pri lepljenju s PUR lepili. Pri izdelavi nosilcev smo uporabili MUF, PUR, PUR v kombinaciji s predpremazom (PUR+P) in EPI lepilo. Po navodilih proizvajalcev lepil smo z vsakim lepilom izdelali po tri štirislojne nosilce. Izvedli smo strižni in delaminacijski test po standardu SIST EN 14080:2013. Ugotovili smo, da so zahteve za strižno trdnost lepilnih spojev dosegla vsa lepila, najvišje vrednosti so dosegli preizkušanci, zlepljeni s PUR+P lepilom (fv avg = 14,9 N/mm2), v vseh primerih pa je bil delež loma po lesu visok. Delaminacijski test smo izvedli po postopkih A, B in C. Pri vseh postopkih sta zahteve dosegli lepili MUF in PUR+P. Delaminacija lepilih spojev je bila pri preizkušancih, zlepljenih s PUR in EPI lepilom pri vseh postopkih prevelika. Ugotovljene so bile šibke povezave med rezultati strižnega in delaminacijskega testa (R2 = 0,179 – 0,272). Potrdili smo, da nanos predpremaza pri lepljenju s PUR lepili močno poveča odpornost proti delaminaciji, prav tako je višja strižna trdnost teh lepilnih spojev.Despite good mechanical properties, beech wood still has much untapped potential in wood construction. It has a high density and is very strong, but at the same time biologically non-durable and dimensionally unstable. These undesirable properties can be reduced with thermal modification. This way we can use beech wood for purposes, for which its use was limited until now. After thermal modification, some mechanical properties of wood worsen and certain properties, impacting the quality of adhesive bonds, change. The purpose of the thesis was to find out, whether the adhesive bonds of the laminated wood from thermally modified beech wood will reach the demands of the standard SIST EN 14080:2013. We were also interested in the impact of the primer in gluing with PUR adhesives. In the manufacture of glulams, we have used the adhesives MUF, PUR, PUR in combination with the primer (PUR+P) and the EPI adhesive. Following the instructions of the manufacturers of adhesives we made three 4-layered glulams with each adhesive. We carried out a shear and delamination test according to the standard SIST EN 14080:2013. We found that all the adhesives have met the requirements for the shear strength of the adhesive bonds, the highest value was reached by specimens, glued with the adhesive PUR+P (fv avg = 14,9 N/mm2), but in all cases the shear strength and wood failure percentage was high. The delamination test was carried out according to the procedures A, B and C. In all the procedures, the requirements were met by the adhesives MUF and PUR+P. The delamination of the adhesive bonds in the case of samples, glued with the adhesives PUR and EPI, was too high in all procedures. We identified poor connections between the results of the shear and delamination test (R2 = 0,179-0,272). We confirmed that the application of the primer in gluing with PUR adhesives significantly increases the resistance to delamination and that the shear strength of these adhesive bonds is also higher