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- Thermomechanical behaviour of bonding joints of wood and wood-based panels at room temperature and elevated temperaturesPublication . Alves, Matheus Henrique; Andrade, Djems; Mesquita, L.M.R.; Barreira, Luísa; Manhique, Jocyla; Santamaria-Echart, Arantzazu; Barreiro, M.F.; Mofreita, FilipeWood 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.
- Thermomechanical behaviour of bonded joints of wood and wood-based panels at room and elevated temperaturesPublication . Andrade, Djems; Alves, Matheus Henrique; Mesquita, L.M.R.; Barreira, Luísa; Manhique, Jocyla; Santamaria-Echart, Arantzazu; Barreiro, Filomena; Mofreita, FilipeWood 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 material. 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.
- Potential use of the ATR-FTIR spectroscopy as an almond cultivar recognition tool: impact of sample and spectral pre-treatmentsPublication . Lamas, Sandra; Rodrigues, Nuno; Santamaria-Echart, Arantzazu; Palu, Igor; Manhique, Jocyla; Herrero, Baudilio; López-Cortés, Isabel; Pereira, José Alberto; Peres, António M.Three almond cultivars (Lauranne, Marinada, and Vairo) were studied, considering morphological parameters that showed statistical cultivar-dependence but not enabled accurate cultivar recognition. Alternatively, attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) was applied to whole endocarp, kernel, and ground almonds. Both transmittance spectra and respective derivatives (3400–2800 and 1900–600 cm of the three matrices were used to establish multivariate linear discriminant models, based on subsets of selected wavenumbers (6–33), allowing 90.5–99.7% of correct cultivar classification for repeated K-fold cross-validation. Ground almonds yielded the best results regardless of spectrum pre-treatment. While epicarp analysis offers less invasiveness, the use of raw transmittance spectra of ground almonds resulted into the most practical approach due to the need of fewer independent variables (less complex models), proving effective for cultivar identification via ATR-FTIR -chemometric tools. Overall, the findings point out that ATR-FTIR is a reliable tool for almond cultivar traceability.