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The effect of tenon length and tenon width on withdrawal load capacity of mortise and tenon (M-T) joint was studied based on the finite element method (FEM), and the relationship of withdrawal load capacity relating to tenon length and tenon width was regressed using response surface method. The results showed that the tenon length and tenon width had remarkable effects on withdrawal load capacity of M-T joint T-shaped sample. The effect of tenon length on withdrawal load capacity was greater than tenon width. The regression equation used to predict the withdrawal load capacity was capable of optimizing the tenon sizes of M-T joint with R-square of 0.926. Using FEM can get more knowledge of M-T joint visually, and reduce the costs of materials and time of experiments.

The fracture behaviors of four wood species commonly used in wood products were characterized when subjected to compact tension (CT) load in radial-longitudinal (RL) system crack propagation. Meanwhile, the failure modes of evaluated CT samples were compared and analyzed using the fractal dimension method. The results showed that wood species had a significant effect on fracture characteristic values, including maximum fracture load, critical stress intensity factor and fracture energy. These characteristic values changed in the same way, i.e., beech wood CT samples obtained the maximum characteristic values, followed by ash, okoume, and poplar in descending order. The fracture behaviors of all wood species evaluated can be described by combining linear and exponential fitting equations at the crack initial stage and evolution stage, respectively. Linear positive proportional relationships were observed between fracture characteristic values and fractal dimensions calculated using cracks in front and left views of CT samples. However, the relationships between fracture characteristic values and fractal dimensions calculated using fracture surfaces were negative. The fractal dimensions of cracks in front view of CT samples could be a better indicator used to predict critical stress intensity factor and fracture energy, which had greater correlation coefficients beyond 0.95.

Mortise-and-tenon (M&ndash, T) joint is a traditional joint type commonly used in wood constructions and wood products. Bending moment capacity (BMC) is a critical criterion to evaluate the strength of the M&ndash, T joint. In order to design the M&ndash, T joint structure more rationally, many researchers have been devoted to studying on this topic. However, the factors influencing the BMC are too many to conduct comprehensive studies using experimental tests, especially for tenon size. In this study, the BMC and bending stiffness of the M&ndash, T joint were studied using a combination of finite element method (FEM) and response surface method to optimize the tenon size of the M&ndash, T joint. The results showed that (1) the proposed finite element model was capable of predicting BMC of M&ndash, T joints with the ratios of FEM to observed, ranging from 0.852 to 1.072, (2) the BMC and stiffness were significantly affected by tenon size, and tenon length had a more significant effect on BMC than tenon width, while the tenon width affected the bending stiffness more significantly, (3) the response surface model proposed to predict and optimize the BMC of the M&ndash, T joint relating to tenon length and tenon width was capable of providing an optimal solution, (4) it was recommended to make the ratio of tenon length to tenon width higher than 1 to get higher BMC of M&ndash, T joints. In conclusion, this study will contribute to reducing the cost of a huge amount of experimental tests by applying FEM and the response surface method to design M&ndash, T joint wood products.

Effects of tenon fit in its width direction on the tensile load-deflection behavior of T-shaped, round-end, mortise-and-tenon joints were investigated experimentally and analytically. Finite element method (FEM) 3D modeling technique as an analytical tool was used to model the tensile load-deformation behavior of T-shaped, round-end, mortise-and-tenon joints. Experimental results indicated that mean ultimate tensile loads and stiffness of evaluated mortise-and-tenon increased significantly as tenon fit increased from 0 to 0.2 mm with an increment of 0.1 mm. The measured glue-line thickness between mortise-andtenon contact surface was found to be a good indicator of tensile load resistance performance of mortise-andtenon joints evaluated in this study. FEM modeling technique was verified as a valid analytical tool for prediction of tensile load resistances of T-shaped, round-end, mortise-and-tenon joints.

For a long time, the geometry dimensions of tenons have been designed through empirical methods, which is not beneficial to designers and manufacturers and results in more time spent in construction and a greater amount of waste wood materials. In this study, an optimal methodology of combining finite element analysis (FEA) with response surface method (RSM) was proposed to investigate the effect of tenon geometric dimensions (length, width, and thickness) on withdrawal and bending load capacities of mortise-and-tenon (M-T) joints, with the aim of making the design of wood products more scientific. The following results were concluded: (1) the effect of tenon length on withdrawal load capacity was greater than tenon thickness, followed by tenon width, (2) the effect of tenon thickness on bending load capacity was greater than those of tenon width, followed by tenon length, (3) it was concluded that the tenon length should be designed to be greater than the tenon width and smaller than twice the tenon width, especially, when tenon thickness was relatively thin, (4) quadratic models can be used to predict the withdrawal and bending load capacities of M-T joints relating the length, width, and thickness of the tenon, (5) the proposed method was capable of being used to optimize the tenon sizes and get more knowledge of M-T joints visually. This study will contribute to reducing the costs of time and materials, and it will result in M-T joints being designed more rationally.

The effect of impregnation treatment of low molecular weight phenol formaldehyde (MWPF) resin on the bolt-bearing yield strength (BBYS) of a three-layered cross-laminated timber (CLT) composed of two face layers of southern pine (Pinus taeda) and one core layer of sweetgum (Liquidambar styraciflua) was investigated together with two additional factors of material type and loading direction. Experimental results indicated that the amount of low MWPF resins penetrating into sweetgum was more than the ones into southern pine. Sweetgum had more uniform distribution of low MWPF resins penetrating longitudinally than southern pine. Impregnation treatment using a low MWPF resin at a concentration of 20% can enhance the BBYS of three-layered CLTs with a 60% increase. The BBYS of a core layer material in three-layered CLTs can significantly alter the overall BBYS of the three-layered CLTs.

Elastic constants of wood are fundamental parameters used in finite element analysis of wood structures. However, few studies and standards regulate the dimensions of sample used to measure elastic constants of wood. The size effect on mechanical properties (i.e., elastic constants and proportional limit stresses) of European beech (Fagus sylvatica L.) wood was studied with five different sizes samples. The data of experiments were inputted into a finite element model of self-designed chair and the loading capacity of chair was investigated by finite element method (FEM) and experiment. The results showed that nonlinear relationships were found between proportional limit stresses, cross-sectional area, and height of specimen by response surface method with R2 greater than 0.72 in longitudinal, radial, and tangential directions. Elastic moduli and shear moduli increased with the height of specimen when cross-sectional area was kept constant, and decreased with an increased cross-sectional area of specimen, when the height was a constant, while the trends of Poisson&rsquo, s ratio were not as expected. The comparisons between experiment and FEM suggested that the accuracy of FEM simulation increase with the raise of width-height ratio (&le, 1) of specimens used to determine the elastic constants. It is recommended to use small cubic wood specimen to determine the elastic mechanical properties used for finite element analysis of beech wood structures. Further research to find optimized wood specimen dimensions to get mechanical properties for FEM is quite necessary.