NC State
  • Researchpp 9575-9587Heldin, M., and Wiklund, U. (2019). "Evaluation of well-defined tool surface designs for groundwood pulping," BioRes. 14(4), 9575-9587.AbstractArticlePDF

    Groundwood pulping is a process in which logs are pressed against a rotating grinding stone. A conventional grinding stone is generally made of grinding particles in a vitrified matrix. As the particles are practically round, their contact with the wood is limited to occasional point contacts. The interaction between the particles and the wood occurs at random positions and at random times, only intermittently contributing to the defibration process. In this work, well-defined grinding tools with asperities giving line contacts rather than point contacts were tested. The tool surface asperities were elongated in shape and positioned with different density over the surface. The tools were tested in a lab-scale equipment at elevated temperatures, and their performance was compared to that of a conventional grinding stone. The grinding mechanisms varied between the different tools, and the specific grinding energy was reduced compared to the conventional tool.

  • Researchpp 9588-9600Parlak, S., and Tetik, E. (2019). "Soil characteristics of natural silver linden (Tilia tomentosa Moench) populations," BioRes. 14(4), 9588-9600.AbstractArticlePDF

    Studies regarding the determination of the ecological characteristics of the natural distribution areas of the silver linden (Tilia tomentosa Moench) are limited. It is of great importance to select areas with similar natural cultivation characteristics in the plantations established for flower or timber production. Physiographical factors affecting these forests were explored to determine the physical and chemical characteristics of the soil. The soil samples were collected from three natural populations, and a total of 43 samples were examined in terms of aspect, elevation, declivity position, and slope. It was determined that the natural linden populations expanded between the altitudes of 0 m and 400 m and 88% of the populations were denser in aspects with shadow. It was found that 91% of the soil was in the class of “deep to very deep”, 61% showed an expansion in sandy clay loam soils, and 30% showed an expansion in sandy loam soils. Average soil pH ranged between 5.6 and 6.6. The soils were found to be salt-free and slightly limy. In terms of the organic carbon amount, the soils were classified as medium.

  • Researchpp 9601-9610Chai, H., Xu, C., Li, J., Kong, F., and Cai, Y. (2019). "Effects of pretreatment with saturated wet air and steaming on the high-frequency vacuum drying characteristics of wood," BioRes. 14(4), 9601-9610.AbstractArticlePDF

    The pretreatment of Mongolian pine (Pinus sylvestris var. mongholica Litv.) was conducted with saturated wet air (80 °C) and atmospheric saturated steam (100 °C) before high-frequency vacuum drying. Effects of the pretreatment on moisture content (MC), drying rate, drying crack, and drying shrinkage strain were investigated. The results showed that through pretreatment, the initial MC of the test material decreased by 2.6% to 6%, and the MC distribution was uniform. The maximum difference of the untreated wood MC distribution after drying was 2%, while that within the pretreated wood was less than 1%. The drying rate also increased, as the drying rates of the untreated and pretreated wood were 0.268%/h, 0.333%/h, and 0.398%/h, respectively. The drying shrinkage strain of the sample was reduced. The drying shrinkage strain of untreated wood was between 0.044 and 0.063, while the drying shrinkage strain of pretreatment wood was between 0.013 and 0.049. The crack of the test material was also reduced, and the drying quality was improved. The pretreatment reduced the high-frequency vacuum drying stress of wood and improved the drying speed and quality.

  • Researchpp 9611-9627Şenol, S., and Budakçı, M. (2019). "Effect of Thermo-Vibro-Mechanic® densification process on the gloss and hardness values of some wood materials," BioRes. 14(4), 9611-9627.AbstractArticlePDF

    This study aimed to determine the gloss and hardness values of low-density wood materials densified using the Thermo-Vibro-Mechanic® (TVM) method after pretreatment with wood stain and wood preservative. This was carried out with a TVM density press that was designed and produced with the support of project 115O138 of the Scientific and Technological Research Council of Turkey (TUBITAK). The samples obtained from Uludağ fir (Abies bornmüelleriana Mattf.) and black poplar (Populus nigra L.) were pretreated with wood stain and wood preservative prior to the TVM densification process. The TVM densification operation was conducted at three different temperatures, three different vibration pressures, and three different vibration times. After the TVM densification process, changes in the gloss (ISO 2813 2014) and Brinell hardness values (TS 2479 1976) of the samples were determined. According to the results, the TVM densification method increased the gloss value of the Uludağ fir and black poplar wood pretreated with the wood preservative by 175% and 1390%, respectively, and increased the Brinell hardness value by 63% and 150%, respectively.

  • Researchpp 9628-9644Li, W., Chen, L., and Li, X. (2019). "Comparison of physical-mechanical and mould-proof properties of furfurylated and DMDHEU-modified wood," BioRes. 14(4), 9628-9644.AbstractArticlePDF

    In this study, 1,3-dimethylol-4,5-dihydroxyethyleneurea (DMDHEU) and furfuryl alcohol (FA) modification catalyzed by acrylic acid were comparatively studied. The effects on physical-mechanical properties and durability against mould of Masson pine and Camphor pine wood were investigated, including weight gain rate (WPG), moisture uptake, equilibrium moisture content (EMC), anti-swelling efficiency (ASE), parallel-to-grain compressive strength (CS), modulus of rupture (MOR), and mould resistance. The wood samples modified with DMDHEU closely retained their original color and texture, whereas the color of furfurylated wood became dark brown and the texture became clearer. The WPG of DMDHEU-treated wood ranged from 17.9% to 29.3%, which was lower than that of furfurylated wood that ranged from 36.7% to 39.3%. The equilibrium moisture content of DMDHEU-modified wood was slightly higher than the untreated wood, while furfurylation decreased the EMC of wood by approximately 50% compared with the untreated wood. The dimensional stability, parallel-to-grain compressive strength, and mildew resistance of Masson pine and Camphor pine improved after both modifications noticeably. It was concluded that acrylic acid can be utilized as a catalyst to perform wood furfurylation and DMDHEU modification.

  • Researchpp 9645-9657Sheng, B., Bian, Y., Liu, Y., and Chui, Y. (2019). "Experimental study of the uniaxial stress-strain relationships of parallel strand bamboo in the longitudinal direction," BioRes. 14(4), 9645-9657.AbstractArticlePDF

    Parallel strand bamboo has extensive potential applications as a structural material for construction. Studying longitudinal stress-strain relationships is essential as a means to build a constitutive law for parallel strand bamboo composites and to conduct an inelastic analysis for structural members constructed by this material. For this reason, failure modes and the damage mechanisms were investigated for tension and compression in parallel strand bamboo composites in the longitudinal direction. An analytical stress-strain formula for the parallel strand bamboo composites was developed for tension and compression related calculations. Tensile failure was caused by the damage of the longitudinal fibers and showed brittle characteristics. The compressive failure resulted from the buckling of the fibers near the damage area. In addition, three types of failure modes were observed; longitudinal buckling failure, compressive-shearing failure, and longitudinal crush failure. The stress-strain relationship in the longitudinal direction of parallel strand bamboo composites exhibited linear behaviour for tension. However, the stress-strain relationship for compression remained linear within the proportional limit, while becoming nonlinear, which can be simulated by a quadratic polynomial, once the stress exceeded the limit. The experimental data agreed well with the model predictions, showing that the present model had high prediction accuracy.

  • Researchpp 9658-9676Yao, L., Yoo, C. G., Pu, Y., Meng, X., Muchero, W., Tuskan, G. A., Tschaplinski, T. J., Ragauskas, A. J., and Yang, H. (2019). "Physicochemical changes of cellulose and their influences on Populus trichocarpa digestibility after different pretreatments," BioRes. 14(4), 9658-9676.AbstractArticlePDF

    Pretreatment is commonly used to reduce recalcitrance of the lignin-carbohydrate matrix. In this study, leading pretreatment technologies, including dilute sulfuric acid, liquid hot water, alkaline, and organosolv pretreatments, were applied to the selected Populus trichocarpa genotype with relatively low lignin content to elucidate cellulose physicochemical property changes and digestibility-related factors. Pretreated Populus trichocarpa (BESC 131) exhibited higher accessibility and glucose yield than the untreated biomass. Chemical composition and Fourier transform infrared (FTIR) analysis results revealed that hemicellulose and lignin were removed to a varying extent depending on the pretreatment techniques applied. The degree of polymerization of the cellulose was decreased to the largest extent after dilute acid pretreatment, followed by organosolv, alkaline, and liquid hot water pretreatments. Cellulose crystallinity index was slightly changed after the pretreatments; however, its differences were not remarkable between those pretreatment techniques. Among four different pretreatments, organosolv was the most effective pretreatment technology in terms of sugar release, which was three times higher than that of the untreated native biomass. Among all of the tested cell wall traits, the lignin content of Populus trichocarpa was the most remarkable feature associated with glucose release, though Populus trichocarpa recalcitrance was not solely dependent on any single factor.

  • Researchpp 9677-9685Monteiro, S. R. S., Martins, C. E. J., Dias, A. M. P. G., and Cruz, H. (2019). "Mechanical characterization of clear wood from Portuguese poplar," BioRes. 14(4), 9677-9685.AbstractArticlePDF

    Poplar wood is a light, soft, and fast-growing timber from a hardwood species, characteristics that make it suitable for several applications. This study focused on the mechanical characterization of Portuguese poplar species, namely white poplar (Populus alba) and black poplar (P. nigra), aiming for its structural use. Therefore, a sample of lamellae was assessed to determine its density and dynamic modulus of elasticity, using a non-destructive device, based on longitudinal vibrations. Clear wood specimens were obtained from a set of lamellae to perform tension and compression parallel-to-grain tests. These tests were used to determine the moduli of elasticity in tension and compression and the tensile and compressive strengths and strains. Also, typical stress-strain curves were identified for the sample studied. The results stressed the potential for structural applications of Portuguese poplar.

  • Researchpp 9686-9703Maslej, M., and Smardzewski, J. (2019). "Experimental testing of elastic properties of LayWood pyramidal cores," BioRes. 14(4), 9686-9703.AbstractArticlePDF

    Sandwich panels most commonly used in the furniture industry are layered structures composed of a hexagonal cell paper core. The use of wood-based composites in modelling truss and pyramidal cores of layered furniture panels is rather scarce. The effect of geometry in the auxetic truss core on the mechanical properties of manufactured wood-based materials was primarily explored in this study. Moreover, the need to conduct further studies was also stressed to determine the elastic properties of cells and cores manufactured from wood filaments using 3D printing. The aim of this study was to determine the effect of the type of filament used in 3D printing and the geometry of pyramidal core cells on elastic constants in cores with identical relative density. This paper presented analytical models of manufactured cells, results of numerical calculations performed using the finite element method, as well as experimental tests determining elastic constants of the cores. Digital image analysis was used and showed that cell geometry had a considerable effect on elastic properties of the core while maintaining identical relative density of these structures. The angle of cell arms had a particularly marked effect on these properties.

  • Researchpp 9704-9718Shi, G., Zhang, Y., Zhao, Y., Chao, L., and Cao, J. (2019). "Prediction methodology for wood compression strength based on particle-filtered near-infrared spectroscopy," BioRes. 14(4), 9704-9718.AbstractArticlePDF

    The measurement of wood mechanical properties is important for engineering design and applications. This study investigated near-infrared (NIR) spectroscopy coupled with particle filter (PF) and partial least-squares (PLS) methods to predict wood compression strength. Three structural timbers (Acer mono, birch, and toothed oak) were studied. The NIR spectra were collected from 900 to 1700 cm-1 and preprocessed by a standard normal variate transformation combined with Savitzky-Golay filtering. The prediction model coefficient matrix and standard variance were obtained by a PF iterative process, and their ratio was used to select the NIR feature wavelength points. A PLS prediction model based on NIR spectroscopy was established to predict the wood compression strength. Compared with the successive projection algorithm (SPA) and Kalman filtering (KF), the PF-PLS prediction model outperformed the other models in all three wood samples, resulting in a high correlation coefficient (r) of 0.89, 0.92, and 0.90, a low root-mean-square error of prediction (RMSEP) of 6.30, 10.60, and 9.71, and a fast average detection speed of 0.28 s, 0.46 s, and 0.33 s, respectively. The optimal PF selection can effectively reduce the redundant information of the NIR matrix and improve the accuracy and efficiency of the prediction model.