Research Articles

A study was conducted on the reinforcement of cross-laminated timber (CLT) concrete composite floors with carbon fiber reinforced plastic (CFRP) to improve its mechanical performance and reliability in wood composite structures. A four-point bending test evaluation was completed on three types of cross-laminated timber concrete composite floors produced with different carbon fiber reinforced plastic reinforcement ratios (33%, 66%, and 100%) on the entire surface of the tensile portion. An increase in the carbon fiber reinforced plastic reinforcement ratio of the composite floors led to an increased bending capacity and a slightly improved yield performance. In the case of a composite floor with a reinforcement ratio of 33%, premature failure occurred in the elastic region due to defects of the CLT such as knots and slopes of the grain. Failure mode analysis revealed that tensile and shear failure coexist when the composite floor has a CFRP reinforcement ratio of 33%. In contrast, reinforcement ratios of 66% and 100% prevented premature failures in the elastic region caused by defects and induced a consistent failure mode. These reinforcement effects reduced the variability in the increased bending capacity of the composite floors and improved the accuracy of the theoretical prediction design via the γ-method. Meanwhile, the shear connections between the cross-laminated timber and concrete via epoxy adhesive exhibited full-composite behavior without being affected by the reinforcement ratio.

This paper presents the push-out experimental results of hybrid notch-screw (HNS) connections for timber-concrete composite structures. A total of 7 groups of specimens were designed and tested. The experimental parameters included the loading constraint conditions (i.e., the test specimens were loaded either in local compression or in uniform compression), shapes of notches in the wood, screw number in notch, notch width, and the inclusion of a self-tapping screw reinforcement for timber or not. The experimental results were discussed in terms of failure modes, ultimate strength, slip moduli, and ductility. The yield strengths and ductility factors were determined based on the load-slip curves according to existing standards. The experimental results showed that both the shear timber width and the self-tapping screw reinforcement played important roles in terms of the ultimate strengths, ductility, and deformability. Rectangular notched connections with screw reinforcements displayed timber shear failure coupled with brittle failure. With the trapezoidal notch, the ductility of the connections improved, coupled with a decrease in the slip modulus. The self-tapping screw reinforcement for shear timber could greatly improve the ductility performance of the HNS connections. The slip modulus models for the connection with vertical deep notches were provided, which were in agreement with the experimental results.

In this work, the catalytic liquefaction of eucalyptus organosolv lignin (EOL) over hydrogen type-zeolite socony mobile-five (HZSM-5) zeolite supported transition metals in an ethanol system was studied, and a cheap transition metal NiCr/HZSM-5 catalyst was prepared. Among them, nickel and chromium proved to have a good synergistic effect, which could remarkably enhance the acidity of the catalyst surface, and the catalytic effect was better than Ru-based precious metal catalysts and commercial Raney Ni catalysts. Meanwhile, the optimal reaction process of NiCr/HZSM-5 and Raney Ni catalyst for synergistic catalysis of EOL was explored. Under the optimal process conditions, the lignin liquefaction rate reached 95.9%, the monophenol yield was 8.64%, and the char content was only 2.08%. Furthermore, 1H-13C heteronuclear single quantum correlation nuclear magnetic resonance (1H-13C HSQC NMR) showed that the β-O-4, β-β, and β-5 linkages of lignin were effectively broken. Thus, a higher liquefaction rate of lignin was realized, which provided the possibility for further comprehensive utilization of lignin.

Fibrovascular bundles (FVB) are a cell tissue in monocot plants composed of fibers, xylem, phloem, and axial parenchyma, binding to form bundles. FVB has the potential to be used as a raw material for composite boards. However, it has several weaknesses, including low strength and surface properties that do not support gluing. This study therefore aimed to investigate the effect of a combined NaOH + Na2SO3 treatment on the physical, chemical, and mechanical properties changes in S. sumatrana Becc. fronds. After separation from the fronds, the fibrovascular bundles were separately immersed in several conditions of NaOH + Na2SO3, for 30 min and 60 min, then washed and dried. Subsequently, the tissues were evaluated using scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, and tensile strength tests. The pits and deposits of the fibrovascular bundles completely collapsed, degraded, and swelled after treatment with 1 M NaOH + 2% Na2SO3. The treatment resulted in the eventual elimination of hemicelluloses and lignins. Separation of the elementary fiber on the fibrovascular bundles occurred at higher concentration treatments. In addition, the strength of the tissue improved after 60 min of immersion in a mixture of 1% NaOH and 0.2% Na2SO3. Based on these results, treatment with a combination of 1% NaOH + 0.2% Na2SO3 was concluded to change the chemical and physical properties as well as improve the mechanical properties of the fibrovascular bundles.

Forest resources are the most important natural resources; their dynamic changes (growth or decline) are affected by socio-economic factors, and to study their linkage is of great significance. However, the relationship between forest resources and social economic factors is normally a multivariate nonlinear relationship. There are difficulties in accurately analyzing it by using traditional multivariate-statistical methods. Also, its explicit mathematical model is inconvenient for intelligent management. In this paper, the radial basis function (RBF) neural network was introduced to study the relationship between the changes of forest resources and socio-economic factors and was evaluated by comparison with the traditional multiple-linear regression model. The results showed that the RBF neural network method can be applied in modeling the dynamic changes of forest resources and showed a higher prediction accuracy over the traditional statistical modeling approaches. At the same time, the RBF neural network can analyze and evaluate the importance of influencing factors simply and conveniently. The results provide a new way and show an application potential for the analysis and intelligent management in forest resources.

Straw fiber mulch film is a promising alternative to petroleum-based plastic mulching film. The optimal combination of process parameters during the manufacturing process of the wheat straw fiber-based plant fiber film (hereinafter referred to as film), was studied via a five-factor and five-level central composite design methodology. Response surface methodology was used to analyze the effects of sizing agent content, wet strength agent mass fraction, basis weight, KP pulp mixing ratio, and beating degree of wheat straw fiber on the dry tensile index, wet tensile index, and degradation time. The optimal parameters were as follows: a sizing agent content of 2.0%, a wet strength agent mass fraction of 60%, a beating degree of wheat straw fiber of 60 °SR, a basis weight of 54.6 to 60.8 g/m2, and a KP pulp mixing ratio of 37.6% to 44.7%. These parameters achieved the desired physical properties, i.e., a degradation time of 55 to 65 d, a dry tensile index of 10 to 12 N·m/g, and a wet tensile index 3.5 to 5.5 N·m/g. With the optimal manufacturing parameters, straw mulch film would meet the demands for agriculture.

The shear capacity was evaluated for specimens connected by beech dowels and composite dowels. The bearing capacities were calculated by the shear capacity formulas of metal dowel connectors in the GB 50005 (2017), NDS (2018), and EN 1995-1-1 (2014) standards. The results showed that, except for the specimen connected by one composite dowel calculated by the GB 50005 standard (2017), the remaining calculation differences were larger. Based on the failure mode, the force analysis of the beech dowels and the composite dowels was carried out. A calculation formula for the shear bearing capacity of the beech dowels and the composite dowels was proposed. The calculated results were in strong agreement with the test results, and the margins of difference were less than 10%. Furthermore, the formulas for two and four connectors were investigated. When the number of effective connectors was calculated by the GB 50005 standard (2017), the differences between the test values and the calculated values were less than 9.36%.

Inducing hydrolytic enzymes production and antibiosis is an attractive process for industrial applications. The approach can be used to repress pathogenic microorganisms. Using a dual culture of Aspergillus fumigatus and Aspergillus flavus, the activities of cellulase, polygalacturonase, chitinase, β-1,3-glucanases, protease, xylanase, and β-glucosidase were 1.78, 3.87, 2.98, 2.79, 6.91, 2.89 U, and 1.43 U∙mg-1 of protein. Meanwhile, the activities were 0.87, 2.78, 0.58, 1.69, 4.45, 2.06, and 0.89 U.mg-1 of protein for A. flavus alone and 0.98, 2.98, 0.87, 1.89, 4.98, 2.58, and 0.91 U.mg-1 of protein for A. fumigatus alone. The cellulase, polygalacturonase, and chitinase activities were studied at different temperatures; 40 °C and 50 °C, which were better temperatures than 20 °C in terms of enzymes activity for A. fumigatus and the dual culture compared to A. flavus. The highest antimicromial activity was observed using the dual fungal culture, where the inhibition zones were 3.13, 3.47, 2.27, 1.77, 1.03, and 2 mm compared with A. fumigatus alone or A. flavus alone, against Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Aspergillus fumigatus, Mucor circinelloides, and Fusarium moniliforme, respectively.

Poplar laminated veneer lumber (poplar LVL) is made of fast-growing poplar veneer and structural adhesive, which can well meet the developing requirement of the modern wood structures. This paper mainly focuses on the lateral loading behavior of the poplar LVL shear wall. For this purpose, six shear wall specimens with different opening types were fabricated and tested under the action of monotonic and cyclic loading. Performances were analyzed on the failure pattern, the load-displacement curve, the shear strength, the ultimate displacement, the elastic lateral stiffness, and the energy dissipation. To strengthen the corner joint, an innovative custom-designed hold-down was adopted, and the mechanical performance was also considered. The results showed that the failure of the specimen was mainly due to the yield of the nails and the separation between the stud and the base plate, while the hold-down can greatly improve the shear strength, the ultimate displacement, and the energy dissipation performance of the poplar LVL shear wall without openings. At last, the evaluation formula of the bearing capacity for the light wood shear wall is proposed so as to promote the theoretical basis for the application of poplar LVL in the light wood frame construction.

Green composites based on ramie fiber yarn and cellulose acetate resin were prepared via hot pressing. The ramie fiber yarns were treated with NaOH and 3-glycidoxypropyltriethoxysilane. The effect of surface treatment on the fiber adhesion to the resin surface and the mechanical properties of the green composites were studied. The chemical properties of the modified ramie fiber yarn were studied via Fourier-transform infrared (FTIR) spectroscopy. The adhesion performance between the fiber and resin was evaluated. The tensile strength of the composites was measured through tensile testing. A single-fiber tensile experiment was used to determine the influence of the tensile strength of the single fibers after surface-treatment. The surface morphology changes were observed via scanning electron microscopy. The results showed fiber–resin adhesion was improved by the surface treatments. However, the surface treatments negatively affected the single-fiber mechanical properties, with the alkali treatment causing greater damage than the silane treatment.