单板层积材力学性能研究

经三种不同的外部条件处理后,使用无损检测设备(FFT)和力学试验机对杉木单板层积材试件静曲强度和弹性模量进行测量。结果表明,试件含水率在纤维饱和点以下时,无损检测方法(FFT)测得的弹性模量和力学试验机测得的静曲强度和弹性模量具有较优的线性相关性;在试件纤维饱和点以上,无损检测方法测得的弹性模量和力学测得的弹性模量有较优的线性相关性,而与静曲强度无线性相关性;单板层积材的静曲强度和弹性模量随着含水率的增加而降低。     

An investigation into the tool wearing characteristics of rubberwood (Hevea brasiliensis) laminated veneer lumber

Peripheral machining of Rubberwood LVL and solid Rubberwood were carried out on a computer numerical control router, using cemented tungsten carbide cutters. The cutter wear rate and power consumption showed similar patterns of increment. Rubberwood LVL was found to be four times as abrasive as solid Rubberwood, and a combination of wear mechanisms were involved in contrast, to abrasion which was the predominant mechanism when machining solid Rubberwood. The use of a simple wear model based on the Taylor’s tool life equation has enabled the total tool wear to be quantified. This information can be expanded into useful production data for the Rubberwood based high-volume Furniture manufacturing industry.     

Effect of laminated structure design on the mechanical properties of bamboo-wood hybrid laminated veneer lumber

The effects of veneer orientation and loading direction on the mechanical properties of bamboo-bundle/poplar veneer laminated veneer lumber (BWLVL) were investigated by a statistical analysis method. Eight types of laminated structure were designed for the BWLVL aiming to explore the feasibility of manufacturing high-performance bamboo-based composites. A specific type of bamboo species named Cizhu bamboo (Neosinocalamus affinis) with a thickness of 6 mm and diameter of 65 mm was used. The wood veneers were from fast-growing poplar tree (Populus ussuriensis Kom.) in China. The bamboo bundles were obtained by a mechanical process. They were then formed into uniform veneers using a one-piece veneer technology. Bamboo bundle and poplar veneer were immersed in water-soluble phenol formaldehyde (PF) resin with low molecular weight for 7 min and dried to MC of 8–12 % under the ambient environment. All specimens were prepared through hand lay-up using compressing molding method. The density and mechanical properties including modulus of elasticity (MOE), modulus of rupture (MOR), and shearing strength (SS) of samples were characterized under loading parallel and perpendicular to the glue line. The results indicated that as the contribution of bamboo bundle increased in laminated structure, especially laminated on the surface layers, the MOE, MOR and SS increased. A lay-up BBPBPBB (B-bamboo, P-poplar) had the highest properties due to the cooperation of bamboo bundle and poplar veneer. A higher value of MOE and MOR was found for the perpendicular loading test than that for the parallel test, while a slightly higher SS was observed parallel to the glue line compared with perpendicular loading. Any lay-up within the homogeneous group can be used to replace others for obtaining the same mechanical properties in applications. These findings suggested that the laminated structure with high stiffness laid-up on the surface layers could improve the performance of natural fiber reinforced composites.     

Effects of cold setting adhesives on properties of laminated veneer lumber from oil palm trunks in comparison with rubberwood

In this study, the properties of laminated veneer lumber (LVL) made from oil palm trunks (OPT) were evaluated in comparison with rubberwood using cold setting adhesives, namely, emulsion polymeric isocyanate (EPI) and polyvinyl acetate (PVAc). The evaluations were based on either dry or after cold water, hot water and cyclic pre-treatment. The density of the OPT LVL was slightly higher than that of solid OPT. Thickness swelling and water absorption of OPT LVL were greater than of rubberwood LVL. Pre-treatment increased the water absorption and thickness swelling. The OPT LVL bonded with EPI without toluene showed greater water absorption and thickness swelling than EPI with toluene. Pre-treatment significantly reduced the tensile strength of OPT LVL. The OPT LVL bonded with EPI without toluene showed higher tensile shear strength, but a greater reduction of tensile shear strength after pre-treatment, than the OPT LVL bonded with EPI and toluene. The PVAc adhesive had greater wettability than the EPI. The EPI without toluene showed a lower contact angle than the EPI with toluene. The loose side of the OPT veneer was found to have greater wettability than the tight side.     

Modification of beech veneers with lignin phenol formaldehyde resins in the production of laminated veneer lumber (LVL)

Rotary cut beech (Fagus sylvatica L.) veneers were treated with four different lignin phenol formaldehyde (LPF) solutions using dimethyl sulfoxide (DMSO) as a solvent. Four of these veneers were bonded with PF adhesive to produce four-layer laminated veneer lumber (LVL). To synthesize the LPF solutions, a commercial phenol formaldehyde resin (PF resin) was individually mixed with three different technical lignins (Indulin AT, BioChoice lignin, organosolv lignin) and lignin cleavage products (LCP) at a ratio of 3:2 (60%:40%). Differential scanning calorimetry showed an increased curing temperature for the LPF resins in comparison to the PF resin. The mechanical and water-related properties of the LPF-modified LVL were shown to be similar or slightly improved compared to PF-modified LVL. Fungal degradation experiments with white-rot fungus (Trametes versicolor) and brown-rot fungus (Coniophora puteana) exhibited no significant differences in the mass loss of the LPF-modified and PF-modified samples except in one case: LVL made from veneers treated with Indulin AT exposed to the white-rot fungus. The resistance to weathering of LVL samples made from veneers treated with technical lignins was low; however, specimens treated with LCP and the reference PF resin displayed a higher resistance to weathering. It is concluded that technical lignins or LCP can, to a certain extent, be used as a substitute for crude-oil based PF resin.     

Evaluation of strength properties of parallel splint lumber (PSL) and its comparison with laminated veneer lumber (LVL), rubber wood and teak

( Heavea brasiliensis ) and an exterior type of adhesive were evaluated in air-dry condition. Block shear tests were also carried out in wet and dry condition. Comparisons of these strength values were made with those of laminated veneer lumber (LVL), solid rubber wood and standard teak. The results show that PSL has slightly lower values of strength properties compared to teak, solid rubber wood and quite inferior ones to those of LVL. On the basis of the data obtained in the present study, PSL made from rubber wood can be utilised as a structural material for different purposes like door and window frames, rigs and trusses.

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Evaluation of strength properties of parallel splint lumber (PSL) and its comparison with laminated veneer lumber (LVL), rubber wood and teak

Heavea brasiliensis ) and an exterior type of adhesive were evaluated in air-dry condition. Block shear tests were also carried out in wet and dry condition. Comparisons of these strength values were made with those of laminated veneer lumber (LVL), solid rubber wood and standard teak. The results show that PSL has slightly lower values of strength properties compared to teak, solid rubber wood and quite inferior ones to those of LVL. On the basis of the data obtained in the present study, PSL made from rubber wood can be utilised as a structural material for different purposes like door and window frames, rigs and trusses.     

An empirical model for predicting the mechanical properties degradation of bamboo bundle laminated veneer lumber (BLVL) by hygrothermal aging treatment

An empirical 3-D model was developed to evaluate the effect of ambient environment on the mechanical properties and degradation behavior of bamboo-bundle laminated veneer lumber (BLVL) fabricated with different levels of PF/PVAc resin. This model can describe the relationship between the modulus of elasticity (MOE), water absorption ratio, and aging temperature. Five levels of PF/PVAc weight ratio (2:1, 4:1, 6:1, 8:1 and 10:1) and three treatment conditions (18, 63, and 100 °C) were examined in this experiment. Computed tomography (CT) scanning technology was employed to observe the morphology of damage degree as well as explore the mechanism of degradation behavior of BLVL. The results indicated that the 3-D model used for tracking and monitoring the variance of MOE provided good predictors. The higher the water impregnation temperature the larger the water absorption ratio and the higher the MOE degradation were. The aging temperature had a significant effect on the mechanical properties and degradation behavior of BLVL. A linear relationship between modulus of rupture (MOR) degradation and aging temperature was observed. The degradation rate of MOE and MOR increased as the temperature increased. The aging degree tested by CT along with damage of inner board showed the PF/PVAc ratio had a significant influence on the mechanical degradation of treated BLVL when the PF/PVAc ratio was below 6:1. Localized yielding, micro-cracks developing between interfaces, PVAc resin softening along with delamination, and debonding were the main failure models for the BLVL by hygrothermal aging treatment.     

Physical and mechanical properties of oriented strand lumber made from an Asian bamboo (Dendrocalamus asper Backer)

The study was conducted to determine the physical and mechanical properties as follows: modulus of rupture, modulus of elasticity, internal bond, thickness swelling and water absorption of oriented strand lumber (OSL) made from the Asian bamboo Dendrocalamus asper Backer. Thirty-six lab boards were produced from these bamboo strands with two manufacturing parameters varying, i.e., four resin types (MF, MUPF, PF, and pMDI) and three levels of resin content (7, 10, and 13%). The results indicate that OSL made from bamboo strands exhibits superior strength properties compared to the commercial products made from wood for the building sector. The resin type has a?significant effect on board properties. Moreover, all properties of the board improve generally with increasing resin content. With regard to the internal bond, bamboo-based OSL shows less strength than wood-based boards. The best results were obtained by using 13% pMDI content at 750?kg $ / $ m³ density.     

The effect of fine strands in core layer on physical and mechanical properties of oriented strand boards (OSB) made of beech (Fagus sylvatica) and poplar (Populus tremula)

This paper discusses the influence of three different content levels of fine strands in the core layers on the physical and mechanical properties of European beech and poplar oriented strand boards (OSB). The results show that increasing the fines content in the core layer from 10 to 50 %, based on total board weight has no significant effect on bending strength and modulus of elasticity (MOE). All panels exceeded the minimum requirement for bending strength and MOE set by EN standards. The highest modulus of rupture (MOR) and modulus of elasticity (MOE) was determined for panels solely made of poplar with different level of fines content. Increasing the amount of fines in the core layer raised the internal bond (IB). Panels made with 30 % fines in the core layer showed highest internal bond strength values. As the fines content increased from 10 to 50 %, thickness swelling decreased. Water absorption after 24 h showed the same declining trend as thickness swelling.     

Improvement of the nutritional quality of a traditional complementary porridge made of fermented yellow maize (Zea mays): effect of maize-legume combinations and traditional processing methods

BACKGROUND: Blends with a cereal-legume ratio of 70:30 have been introduced in many communities for use in the preparation of complementary foods with augmented protein quality. These foods should meet World Health Organization estimated energy and nutrient needs from complementary foods. OBJECTIVE: To increase energy and nutrient densities and nutrient availability in a traditional complementary porridge. METHODS: Yellow maize was processed by lactic acid fermentation. Peanuts (Arachis hypogea) and beans (Phaseolus vulgaris) were processed by germination, roasting, dehulling, and a combination of germination and roasting. Blends were prepared from processed peanuts and beans and cooked into porridges with viscosities less than 3,000 cp. Traditional porridge was the control and consisted of fermented yellow maize only. The porridges were analyzed for their physicochemical and nutritional properties. RESULTS: Blends increased energy and nutrient densities in porridges compared with the control (p < .05). The maize-peanuts combination yielded porridges with higher energy densities and improved nutritional quality compared with the maize-beans combinations. In vitro availability of iron did not change (p > .05) with formulation of the blends except for porridges made from maize and germinated peanuts, but there was a significant increase in zinc in vitro availability, whereas a decrease was observed for calcium in vitro availability. The energy densities of maize-peanuts porridges were sufficient to cover energy required from complementary foods for infants aged 6 to 11 months receiving four meals of complementary foods per day and an average amount of energy from breastmilk. CONCLUSIONS: Maize-legume blends can efficiently improve the nutritional quality of traditional porridge. Peanuts are the best legume complements.     

生熟麦曲在黄酒传统工艺中的应用研究

通过对生麦曲、熟麦曲、生麦曲和熟麦曲混合配比按传统黄酒发酵工艺进行试验,得出生麦曲因液化力、糖化力和蛋白质分解力等3个力都较低,使它起发时间迟,发酵缓慢,不彻底;熟麦曲3个力都较高,使其起发时间早,且发酵较彻底;混合曲由于按生麦曲和熟麦曲一定关系配比,表现出其的3个力处于两者之间,发酵状况也处于两者之间,同时得出可以酿造出与生麦曲所酿的酒风味相媲美的酒,为进一步改良传统工艺打下一定基础.混合曲中生麦曲与熟麦曲按9:1的比例较佳.     

The effect of coagulants on the texture of chhana (an acid and heat coagulated product made from milk)

Chhana (a heat and acid coagulated milk protein mass and an Indian equivalent to cottage cheese) can be used as a raw material for the manufacture of various types of sweets popular all over India. Texture Profile Analysis (TPA), using an Instron Universal Testing Machine, was used to determine the effect of different coagulants on the textural characteristics of chhana. Chhana was made using three different coagulants: citric acid, lactic acid and calcium lactate, at five different concentrations, 0.5, 1, 2, 4 and 8%. Two types of dilution media, distilled water and acid whey, were used. The textural characteristics obtained when aqueous 0.5% citric acid, aqueous 0.5% lactic acid and 4–8% calcium lactate solutions, using acid whey as the solvent, gave similar TPA readings to normal chhana.     

Inhibitory effect of yellow myrobalan (Terminalia chebula) extract on fibrosis induced by carbon tetrachloride in rat liver

Ethyl acetate layer of methanol extract (TCE) of yellow myrobalan (Terminalia chebula) contains 2.4% of chebulic acid, a standard compound in TCE, which have a strong anti-oxidative effect and was reported in our previous study. Thirty-one male SD rats were randomly divided into 5 groups (normal control, CCl₄ control, TCE control, CCl₄+high dose TCE, and low dose TCE). Liver fibrosis was induced by i.p. injection of CCl₄ and TCE were orally administrated. TCE decreased the up-regulated malondealdehyde value and increased the down-regulated ratio of GSH/GSSG content and activities of GRd, GPx, and GST compared to the CCl₄ control group. Decreased dysfunction and inflammatory reaction in liver was confirmed by alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels, relative liver weight and infiltration of neutrophils. Also, TCE inhibited phenotype change of hepatic stellate cells (HSC) by reducing α-smooth muscle actin (α-SMA) gene expression and protein production. Inhibition of collagen 1A1 gene expression and protein production were also confirmed. From these results, TCE may be a useful material for preventing liver fibrosis.     

聚噁二唑耐高温滤材的制备及其应用性能研究

以耐高温聚噁二唑纤维为原料,通过针刺法制备聚噁二唑针刺非织造布,再经系列后整理与缝制得到聚噁二唑耐高温过滤袋,将其应用于耐高温过滤领域,取得了初步效果.在研究耐高温阻燃聚噁二唑纤维相关性能的基础上,重点研究耐高温聚噁二唑滤材应用前后的过滤性能与力学性能的变化.结果表明:耐高温聚噁二唑纤维可广泛应用于高温烟气粉尘过滤领域,其滤材具有耐热性能好、拉伸强度高、孔径分布集中均一、过滤阻力小、过滤效率高等优点,可在高温烟气过滤领域长期使用.     

Control of Ephestia cautella (Walker) (Lepidoptera: Phycitidae) by synthetic sex pheromones in the laboratory and store

The reduction in mating of Ephestia cautella caused by permeation of the atmosphere with synthetic sex pheromone components was investigated in the laboratory and store. In the laboratory the three main components of the pheromone complex were tested either singly or in combination, and (Z, E)-9,12-tetradecadienyl acetate (ZETA) was found to be the most effective. Field trials were carried out in simulated cocoa stores with four different initial application rates of ZETA and two moth population densities. The concentration of airborne pheromone was measured, and the emergence of the F₁ generation was used to assess the degree of reproductive control. Decreased numbers of copulating pairs were observed in the stores treated with pheromone, and F₁ emergences were reduced by 91 to over 99% when population densities of moths of 0.1–0.3 moths/m² surface area were exposed to pheromone concentrations of 4–10 μg/m³. The results provide a basis for investigation of the effects of factors such as method of pheromone application and store conditions on the effectiveness of this control technique.     

The effect of log heating temperature on the peeling process and veneer quality: beech, birch, and spruce case studies

Heating green-wood prior to peeling is necessary to improve both peeling process and quality of veneer. This study investigates optimum heating temperatures by soaking of beech, birch and spruce. Experiments have studied the influence of heating temperatures from 20 to 80 °C on thickness deviations and veneer lathe checking using a pneumatic rugosimeter and image analysis of opening checks with the SMOF device (Système de Mesure de l’Ouverture des Fissures). Conclusions account for reduced heating temperatures compared to the temperatures currently in-use in the industry. Already at 50 °C, positive effects of heating ensure efficient peeling process. Low temperatures produce veneers with deeper and more spaced checks than high temperatures when checks are closer and less deep, becoming even unpredictable especially in case of spruce. These results establish the SMOF as an essential non-destructive control device to control the quality of the veneer produced at research level.