Volume 15 Issue 3

The bending moment capacity of heat-treated wood dowel joints loaded in compression or tension was predicted via two artificial neural network (ANN) models. Additionally, a comparative study between similar models that were developed through response surface methodology (RSM) was performed. The joints were made of heat-treated ash (Fraxinus excelsior). The values of the ultimate failure load and the moment arms were recorded for each run via a universal testing machine. To develop the ANN models, the experimental data were randomly divided into three subsets, which were needed for the training, testing, and validation phases. The RSM models were obtained from the literature. The performances of the models were analyzed in terms of the correlation coefficient, coefficient of determination, root mean square error, mean square error, and mean absolute prediction error. A sensitivity analysis was also performed to observe potential changes in the results due to the uncertainty in the input variables. The ANN model better predicted the bending moment capacity of heat-treated wood dowel joints loaded in compression than the RSM model. In contrast, the RSM model predicted the bending moment capacity of joints loaded in tension more accurately than the ANN model.

Compressive and tensile strengths were considered for a box connected by dovetail keys under different mortise-and-tenon sizes. Poplar wood modified by melamine resin (MF modified poplar wood) was chosen as the experimental material, and the experimental study was carried out on the box using the concentrated loading method. The results showed that the ratio (T) of hole depth to slope height had a significant effect on the structural strength of the box connected by dovetail keys when other dimensional parameters were the same. When T was equal to 75%, the compression and tensile strength of the box was the highest, and the joint had better recovery and deformation ability. When T` was equal to 50%, the box strength was the worst, and the joint damage was the most serious in both types of loading. In addition, the measurement standard of the displacement was determined through preliminary experimentation. The compression quantity was 8 mm, and the stretching quantity was 5 mm. The latter experiment showed the reliability of the pre-experiment.

Palm fiber, a type of natural multicellular fiber, exhibits distinct mechanical properties, such as excellent elasticity, higher fracture energy, and desirable stretch ability. To reveal the structure-property relationship, a multi-scale layered fractal theoretical model was introduced to investigate the tensile behavior of palm fibers at different scales. A three-circle model was established and used to simulate the hierarchical organization of palm fibers. The palm fibers consisted of cellulose molecular chains, fibril filaments, microfibrils, and cells. Moreover, the characteristics of stress, fracture energy, and Young’s modulus on different scales were calculated and verified by tensile testing and atomic force microscopy (AFM). The results revealed that the fractal model effectively decoupled the contributions of different scales to the tensile properties. In particular, the microfibril mainly influenced the stiffness, whereas the cell determined the toughness of palm fibers. The findings of the current study can be utilized to improve the design and preparation of fiber-based nanomaterials.

This study aimed to obtain a better method for establishing a finite element model of mortise-and-tenon (M-T) joints. Three types of M-T joint finite element models, which included a whole rigid model, a tie rigid model, and a semi-rigid model, were established and compared with experimental results by predicting the bending moment capacity (BMC) of M-T joints based on the finite element method (FEM). The results showed that the semi-rigid model performed much better than the tie rigid model, followed by the whole rigid model. For the semi-rigid model, the ratios of FEM ranged from 0.85 to 1.09. For the whole rigid model and tie rigid model, the BMC of the M-T joint was overestimated. In addition, the results showed that tenon size remarkably affected the BMC and stiffness of the M-T joint, and tenon width had a greater effect on the BMC of the M-T joint than the tenon length.

Aqueous ammonia vapors were found to affect the color and structure of oak (Quercus L.) and Robinia pseudoacacia L. woods. The modification process was performed using 5% or 10% ammonia concentration at a temperature of 120 °C, 130 °C, or 140 °C. Wood mass and volume change coefficients were determined. The degree of wood discoloration was determined using the Commission Internationale de l’Eclairage (CIE) Lab system, and the changes to the chemical structure were determined using the Fourier transform infrared (FTIR) technique. The samples darkened due to the modification. They also became less red and less yellow. It was found that Robinia wood was more discolored. The total color change (ΔE*) of Robinia wood ranged from 39.0 to 41.9, and of oak wood ranged from 26.8 to 33.3. The L* and b* color coordinates had a significant effect on the ΔE. Analysis of variance showed that in most cases both the concentration of the aqueous ammonia solution and the process temperature alone did not cause significant differences in the colour of the wood (GenStat 18ed (VSN International 2015)). However, the interaction between concentration and temperature was important. Analysis of wood structure via FTIR showed that during the applied treatment, wood underwent chemical changes and that the effects were different in the compared species.

Oriented strand boards (OSB) are widely used in construction replacing plywood. There are four types of boards (OSB/1, OSB/2, OSB/3, OSB/4) carried out depending on the conditions of uses. The present research aimed to evaluate the physical and mechanical performance of these types of boards, with 10 mm, 11 mm, 18 mm and 22 mm thicknesses. The boards were industrially manufactured using the continue press line. The results showed that the compression grade increased with decreasing of the wood strands densities, from 1.3 (OSB/1) to 1.1 (OSB/3). Thickness swelling values were lower for OSB/3 and OSB/2 with 35% and 14%, when compared to OSB/1. For these boards a slight increase in adhesive content and a lower speed of pressing line was set considering that they are designated for the exterior use. An increase in density with about 7.6% led to an increase with about 19% of modulus of rupture (MOR), when compare OSB 10 mm with OSB 22 mm. Improvements with 27% to 22% MOR and 13% to 10% modulus of elasticity (MOE) in case of OSB/3 and OSB/2 compared to OSB/1 were found. Internal bond (IB) values were with about 32% higher for OSB/3 than those reached by OSB/1 and the thinner boards registered 25% higher IB values even after boiling test, compared to the thicker ones.

The sapling stage is an important phase due to maintaining plant growth, stability, and survival over the life cycle of trees. However, there are limited investigations in the literature related to both growth and stability of different tree species. This study thus investigated how different tree species at the sapling stage showed different anatomical, morphological, and flexural traits despite being of similar age and growing under the same environmental conditions. The variation of sapling properties was determined in two deciduous tree species: common oak (Quercus robur L.) and Oriental beech (Fagus orientalis Lipsky). The results of anatomical and morphological measurements showed that the highest average values of ray length, ray width, pith radius, pith%, bark%, and node numbers were obtained in oak saplings, whereas average ring width, number of rays, and wood% were found to be higher in beech saplings. Oak also exhibited better functional stability in its saplings. The flexural properties were almost 60% greater in oak stems than beech stems. The variations in flexural properties were explained by the morphological and anatomical traits since stability was positively correlated with pith radius, pith%, and bark% and negatively correlated with the number of rays and wood%.

Microwave-assistance was used to increase the degumming efficiency in flax water retting. Different pre-soaking times, microwave times, and microwave power were investigated in this study. The relationships between degumming rate and process parameters were established via response surface methodology (RSM). The optimum process parameters were a pre-soaking time of 25.5 h, a microwave time of 18.5 min, and a microwave power setting of 570 W. Under these optimal conditions, the degumming rate was 83.85% ± 1.13%, which was 1.33 times higher than that of natural hot water retting (P < 0.05). Moreover, the tensile properties and color of the resulting fibers showed that they had tensile properties similar to those of the natural hot water retting fibers. However, the color values for the natural hot water retting fibers were higher than those of the fibers treated with microwave-assisted flax water retting.

A LaAlO3 carrier was prepared via the sol-gel method, and a Ni/LaAlO3 catalyst was prepared via the homogeneous precipitation method; this catalyst was used for the catalytic pyrolysis of soybean straw for syngas (H2 + CO) production. The analysis of the raw materials (straw) was performed via elemental analysis and industrial analysis. The support and catalyst were characterized and analyzed by X-ray fluorescence spectroscopy, thermogravimetric analysis, X-ray diffraction, scanning electron microscopy, and N2 adsorption-desorption isotherms. The results illustrated that the NiO was uniformly loaded on the LaAlO3 surface. Furthermore, the effects of the Ni loading amount, pyrolysis temperature, holding time, and calcination temperature on the performance of the catalyst were studied. The results showed that the catalyst had the highest increase in production and concentration of H2 and CO when the Ni loading was 10 wt%, the calcination temperature was 500 °C, the reaction temperature was 800 °C, and the holding time was 20 min. Compared with the pyrolysis of straw without a catalyst, the yield of H2 and CO increased from 85 mL/g and 125 mL/g to 238.5 mL/g and 255 mL/g, respectively, and the concentration of H2 and CO increased from 23.5 vol% and 29.4 vol% to 43.1 vol% and 41.9 vol%, respectively.

A new powder feedstock composed of biocompatible and degradable biomass materials was introduced and evaluated for laser sintering in this research. The goal for the material is to facilitate high-value utilization of sustainable materials and expand the variety of feedstock that can be used for laser sintering. It was mechanically mixed with polylactic acid (PLA) powder and the filler of α-cellulose powder in the content of 5 wt%, 10 wt%, 15 wt%, and 20 wt%. The effects of the ingredient proportions were evaluated relative to laser sintering performance of α-cellulose/PLA mixtures. The results revealed that the increasing cellulose loading had almost no influence on the mixtures’ glass transition temperature, the melt temperature, and the crystallization temperature; thus, the mixtures would share the same processing parameters with neat PLA during the laser sintering fabrication. Although the cellulose loading reduced the materials’ melt fluidity and mechanical properties, it decreased the dimensional deformation of the laser-sintered parts and made the mixture more feasible as the feedstock of laser sintering compared to neat PLA.