Thermomechanical behaviour of bonding joints of wood and wood-based panels at room temperature and elevated temperatures
Academic ArticleConference Paper
This work was developed within the scope of the project NORTE-01-0247-FEDER-072225, supported by North
Portugal Regional Operational Programme (NORTE 2020), under the PORTUGAL 2020 Partnership Agreement,
through the European Regional Development Fund (ERDF), CIMO (UIDB/00690/2020) funded by FCT/MCTES
(PIDDAC), FCT, P.I., through the institutional scientific employment program-contract for Arantzazu Santamaria.
Wood is a natural material traditionally used in the construction industry. In recent decades, developments in
scientific research have turned wood into a high-tech construction resource. Increased interest in bonded joints in wood
construction is due to the advantages of adhesive technology compared to traditional mechanical joining techniques. It is
very important to understand the influence of elevated temperatures on adhesives due to their use in multilayer systems
such as compartmentation walls and fire-resistant doors, which require adequate mechanical and thermal resistance in fire
situations. The purpose of this study is to investigate the mechanical behaviour of different structural adhesives on bonded
connections of wood and wood-based panels at room and elevated temperatures through experimental testing. The
performance of the adhesives was evaluated at room temperature and at 50 °C, 100 °C, 150 °C, and 200 °C. The resins
tested were a polyurethane prepolymer resulting from the reaction between polyols and diphenylmethane diisocyanate
(MDI), Flexpur151, and urea resin glue for hot pressing. The tensile shear tests with lap joints were performed using
combinations of pinewood-pinewood and MDF-MDF. The experimental tests were done according to EN 205:2016, which
allows for determining the tensile shear strength of bonded joints. The failure mode of the tested specimens was classified
according to ASTM D5573. The results show that the bonding strength and the displacement of the specimens decrease
with the increase of the temperature. The failure mode presents a different result for different temperatures. For example,
for the urea resin, the shear resistance of MDF-MDF panels decreases about 50 % when exposed to 100 ºC with the failure
mode usually occurring on the panel, and 98 % when exposed to 200 ºC with the failure mode in the adhesion plane. For
the MDI based resin, the shear resistance of MDF-MDF panels decreases about 35 % when exposed to 100 ºC with the
failure usually occurring on the panel, and 65 % when exposed to 200 ºC with the failure mode occurring in the adhesion
plane.
