Application of different microscopy techniques for interphase analysis of glued-laminated Tectona grandis wood

Abstract The use of tropical wood species in the production of glued laminated timber (GLT) has been researched with the aim of facilitating the utilization of this material in countries lacking pine and eucalyptus. Teak (Tectona grandis) stands out as a wood species with superior physical and mechanical properties, in addition to exhibiting excellent natural durability. Studies indicate that the use of Teak in GLT is promising. Besides the wood properties, the interphase of the composite directly impacts structural performance, which is typically evaluated through macroscopic testing. However, incorporating microscopic analyses can provide valuable insights into bonding characteristics, which directly affect macroscopic results. Although many studies employ microscopy techniques such as polarized light microscopy (LM), fluorescence microscopy (FM), confocal laser scanning microscopy (CSLM), scanning electron microscopy (SEM), and micro-computed tomography (µCT), no studies have yet compared the effectiveness of these approaches. In this context, the present research aimed to compare the efficiency of five different microscopy techniques in assessing the adhesive interphase in GLT elements produced with Teak. It was observed that the evaluated techniques are complementary, each with specific advantages and limitations. The most detailed results were obtained with CSLM, indicating the relevance of this methodology for more precise analyses of adhesive interphases. In addition to conducting macroscopic tests, it is recommended to employ at least two complementary microscopy techniques to corroborate additional information regarding the quality of bonding in GLT beams. This approach can significantly contribute to the enhancement of GLT manufacturing and usage, reinforcing the effectiveness of Teak as a viable and sustainable alternative.