Influence of wood substrate on bonding joint with structural silicone sealants for wood frames applications

The interest on silicone structural sealants application in the field of wood window frames is growing fast, because of the introduction of novel production processes and stringent energy performance requirements of buildings. Structural timber-glass-sealant adhesive bonding assessments were carried out in several researches. The goal of this paper is to investigate the mechanism of adhesion and the properties of wood-structural silicone joints in order to understand the failure modes and strength of these bondings. For this purpose, tensile tests on wood-silicone joints were carried out in order to investigate the adhesion strength with different wood species. Moreover, peel tests have been carried out on wood-silicone joints in order to better understand the adhesion properties of the different materials. For this purpose, a dedicated belt was used, to avoid typical problems encountered during the standard peel test execution. In this investigation, both tests on untreated wood-silicone bonding and on coated wood-silicone bonding have been carried out, in order to capture the influence of wood species and wood primers on the adhesion to silicone. The results clearly proved that the adhesion strength between wood and structural silicone is highly influenced by the wood species, and a good correlation was found between tensile strength and breakage load in peel test. These results can be useful when assessing the strength of wood-silicone-double glazing glass joints and when informing FE models of wood frames joints and also to provide indications about optimal structural sealant application modes and selection of silicone typologies in wood frames applications.