Avaliação na qualidade da colagem e desempenho de painéis Cross Laminated Timber (CLT) produzidos com madeira de Eucalyptus grandis e Pinus taeda

Abstract

The objective of the present study is to evaluate the bonding quality of the lamellas of CLT panels with the use of single-component polyurethane adhesive produced with Eucalyptus grandis, Pinus taeda, and also a mixture of the species. The material used for the research was collected at the Department of Diagnosis and Agricultural Research (DDPA), Santa Maria, RS, Brazil. After felling the trees, they were cut into planks and transported to the Forest Products Laboratory at UFSM. This material was stored in a climate chamber with controlled temperature and relative humidity until it reached hygroscopic equilibrium, with a moisture content of around 12%. After this period, the lamellae were sectioned into the final dimensions for assembling the CLT panels, at 1,6 x 10 x 50 cm, thickness, width, and length, respectively. The physical properties of wood were tested: density at 12%, basic density, and moisture content. In addition, the lamellae were visually and mechanically (MOE) classified for better arrangement in the making of the panels. The panels were assembled in three layers, and each layer with the arrangement of five lamellae, in a total of 10 panels (four panels of E. grandis, four panels of P. taeda, and two panels of the mixture of species). We evaluated the properties of specific mass, moisture content, and tests to evaluate the quality of gluing, according to the American ANSI (2019): shear at the glue line and delamination. The results showed that the physical properties of wood were superior for E. grandis compared to P. taeda, corroborating the literature. The visual and mechanical classification allowed the selection of pieces and the organization of lamellas with higher quality to be placed in the outer layers of the panels, and with lower properties in the inner layers. The panels produced with E. grandis wood and with a mixture of species showed adequate properties, showing that it can be a viable alternative for use in the manufacture of these panels. The specific mass of the wood and of the panels, MOE, shear strength at the glue line by compression and also the absence of delamination indicate better results for the wood of CLT panels produced with E. grandis, indicating that the gluing was better compared to panels assembled with pure P. taeda wood. In this perspective, the importance of future studies with the projection of CLT panels in large dimensions is emphasized, in order to evaluate their properties in such a way as they are made commercially.