The quality of adhesive bond between wood and steel

Cilj raziskave je bil ugotoviti primernost izbranih poliuretanskih in epoksidnih lepil za konstrukcijsko lepljenje lesa in jekla. Preizkusili smo štiri poliuretanska lepila COSMO in dve epoksidni lepili ERGO in XEPOX. Kakovost lepilnega spoja smo ovrednotili s testom strižne trdnosti, ki je sledil posameznim postopkom izpostavitve preizkušancev: izpostavitev standardni klimi, z relativno zračno vlažnostjo 65 % in temperaturo 20 °Cizpostavitev vlažni klimi s 87 % vlažnostjo in temperaturo 20 °Cter različne izpostavitve (namakanje/kuhanje) v vodi. Rezultati so pokazali, da proučevana poliuretanska lepila z vidika kakovosti lepljenja ne morejo konkurirati epoksidnim lepilom. Proučevani epoksidni lepili sta zagotovili odlično kakovost lepljenja v suhih pogojih ter se izkazali kot pogojno primerni za nekonstrukcijsko rabo v vlažnih pogojih. Za uporabo izbranega lepila v konstrukcijskih aplikacijah je bilo izdano priporočilo, da je potrebno lepilni spoj dodatno ojačati z vijaki, ki bi zagotovili zanesljivost spoja v primeru nastopa izjemne vlage ali požara.The aim of the research was to determine the suitability of selected polyurethane and epoxy adhesives for structural bonding of wood and steel. We tested four polyurethane adhesives COSMO and two epoxy adhesives ERGO and XEPOX. The quality of the adhesive bond was evaluated by a shear strength test followed by one of the following exposure tests of the specimens: exposure to the standard climate with 65 % relative humidity and a temperature of20 °Cexposure to humid climate with 87 % humidity and a temperature of 20 °Cand various exposures (soaking/cooking) in water. The results showed that the polyurethane adhesives studied in this work cannot compete with epoxy adhesives in terms of bonding quality. The epoxy adhesives provided excellent bonding properties in dry conditions,and proved to be potentially suitable for non-structural use in humid conditions. However, in order to use the selected adhesives in construction applications, it is recommended that the adhesive joint should be additionally reinforced with screws to ensure the reliability of the joint in the event of exceptional moisture or fire