In a current research project the gluability of various soft- und hardwood species and their applicability in glued laminated timber are investigated. The influence of the processing parameters on the delamination resistance and shear strength of the glue lines are presented in this work.
The bonding forces, which are necessary for the integrity of a glue line, act in the interface within a distance that varies from nanometers to micrometers. The parameters that may have significant influence on the bonding strength and durability of adhesive joints are numerous and depend on the type of wood, adhesive and processing conditions.
This study aims to develop an improved understanding of the interfacial bond behavior of softwood glulam joints with bonded-in threaded steel rod. A total of 39 glulam joints with bonded-in single-threaded steel rods were tested to failure in the pull-pull configuration. The test results were presented in term of failure modes, load-relative movement response, pullout strength, and the corresponding slip. The distributions of bonded-in rod axial strain, interfacial bond stress, and relative movement were also analyzed to evaluate the local bond stress– relative movement response in the bond line. The results confirmed that the bond-relative movement response is dependent on the locations along the anchorage length, and the bond-relative movement responses located near both the loaded end and the anchorage end were observed to be stiffer than those at other locations. Finally, the predictions for the load capacity of the glulam joints with bonded-in threaded steel rod were carried out based on several existing empirical formulas.
In this paper, results of flexure tests aimed at improving the structural behavior of softwood beams reinforced with unglued composite plates and at developing an effective alternative to the use of organic resins are presented. The addition of modest ratios of GFRP (Glass Fiber Reinforced Polymer) composite strengthening can prevent tension failure in timber beams. However the application of organic matrices presents problems of reversibility, compatibility and durability with timber and poor performance at high temperatures. The increment in capacity and stiffness and the analysis of the failure modes is the central focus of this paper. The experimental campaign is dealing with a significant number of un-reinforced and reinforced beams strengthened with unbonded GFRP plates. A 3-dimensional finite element model is also presented for simulating the non-linear behavior of GFRP-reinforced softwood beams. The ability of the numerical model to reproduce experimental results for the load–deflection curves is validated.
The objective of this study was to examine new attributes and conduct economic analyses for composite CLT (CCLT) and value-added appearance-based CLT products manufactured with varying substitution of softwood lumber with structural composite lumber (SCL) and hardwood lumber. Incentives for including such materials could be aesthetic, structural and economic.
Structural and aesthetic property assessments were carried out on prototype CLT panels. Multiple CLT panel configurations (17) were evaluated to assess the effects of including hardwood and SCL materials in the layups. Presence of hardwood in the panels’ configuration generally led to higher checking and density. Because of the higher shrinkage of hardwood, the bondline suffered from more delamination. A lower density hardwood (aspen) was included in some configurations and exhibited a greater direct compatibility with current Canadian manufacturing process. Changes to this process, such as selecting a hardwood specific adhesive may lead to improvements.
The proposed paper presents two alternative strategies for using fast-growing, low-grade softwood for modern engineered wood products. A chemical based strategy is explored first with the testing of polymer-impregnated small clear wood samples. A second mechanical based strategy based on the tectonics of stress-laminated bridge decks is examined in further detail with 1:10 scaled structural models, followed later on by full-scale testing. The relative benefits and disadvantages of each strategy are compared to each other, and benchmarked against regular sawn timber and conventional engineered wood products like glulam and cross-laminated timber.