Bonding strength in the structure of engineered wood products and composites is one of the vital properties for their application. Up to now, numerous research efforts have been made on improving durability, wettability, and strength of resins or adhesives. However, there are only a few reports on how to improve bond line strength according to wood feature itself. In this study, a new conceptual bonding design based on wood radial section feature was reported. In this design, finger-joint like bonding interfaces were generated by hot pressing two resin coated wood radial sections together at optimized pressure of 300 lb per square inch (psi). By this design, the wet bonding strength of the bond line has potential to be higher than dry bonding strength. Meanwhile, with a compression ratio of 7.3% of wood strips, the obtained dry bonding or shear strength has been significantly increased up to 33.9%, as compared to end matched tangential controls. Wood specific gravity played an important role in this design. A proper compression ratio explored here in the radial section was about 17%. This work has provided a new route to improve wood bonding strength in an environmentally friendly way. Its impact on bending strength and dimensional stability of bonded wood structures needs to be further investigated.
Published by Elsevier Ltd.
Wood materials have been widely used in human's daily life for a very long time, due to its easy processing, abundant resource, renewable, and environmentally friendly features. With the increasing demand of the sustainable material, fast growing tree species are the main feedstock of wood based engineered products. Southern yellow pine trees are the most popular species in the southern United States. In order to add value of use, prolong service life, and broaden their application, many engineering approaches have been developed to produce wood based products, such as plywood, laminated veneer lumber, glued laminated timber, and cross laminated timber. In these products, all of them are assembled from single wood elements, such as wood veneer, wood strip, and lumber, which are bonded or glued together by adhesives. Therefore, bonding strength and bonding durability of these bond lines are the major concerns in applications. Generally, the bonding strength of engineered wood products is evaluated by its resistance to delamination and bonding creep behavior .
The strength prediction is, more or less, reliable in materials like steel and plastic, which are typical materials with relevant uniform structure. Most of the adhesives are, just like plastics, polymeric and their performance can be computationally modeled in a reliable way. The structures of solid wood material layers or elements are much more complicated than that of steel and polymers. Since wood is a type of anisotropic material, the quality of wood surface for bonding is less consistent , The main variables include wood species and sections, reaction wood, moisture content, and wood defects. The bonding strength is significantly different even in the same wood species. In evaluation of...