小径级竹材抗弯性能测试方法

探究小径级竹材（胸高直径50 mm以下）的抗弯性能实验方法，充分发掘小径级竹材的性能，为小径级竹材的材性研究和工业加工等提供技术支撑，以扩大小径级竹材的用途，提高其利用价值。实验以箬竹、早园竹、苦竹、水竹和笔竿竹5种小径级竹材为研究对象，利用三点弯曲法与四点弯曲法分别测定了不同长径比（试件长度与其直径之比）试样的抗弯弹性模量和抗弯强度，以测试数据的标准差、标准误差和变异系数为评价依据，分析不同长径比的试样和加压弯曲方式对实验结果的影响。结果表明：就加压方式而言，当测试抗弯弹性模量时，三点加压弯曲法优于四点加压弯曲法；就试样长径比而言，长径比为12的试件更适于测试小径级竹材的抗弯弹性模量和抗弯强度。因此，当测试小径级竹材抗弯性能时，宜采用三点加压弯曲方式、长径比为12的试样并按照一定的流程进行操作。     

Elastic properties of the extruded tubular particleboard

Abstract

Particleboard can be commonly produced by flat-pressing and extrusion methods. The elastic properties of the flat-pressed particleboard have been studied a lot, but the extruded particleboard has not had much attention. Six elastic properties of two commercial extruded tubular particleboards with different solid density were measured by a three-point bending test and electric resistance gages method. The elastic modulus in the extruded direction of the tubular particleboard is only one-tenth of the other two directions. The extruded tubular particleboard can not only be regarded as an orthotropic material but also a transverse surface isotropic material. The isotropic plane is the transverse section of the extruded particleboard which is different from the flat-pressed particle with the length–width plane as the isotropic plane. The checking of the data we measured demonstrated suitability and rationality.     

Bending moment resistance of corner joints constructed with spline under diagonal tension and compression

We determined the effects of the penetration depth and spline material and composite material type as well as joining method on bending moment resistance under diagonal compression and tension in common wood panel structures. Composite materials were laminated medium density fiberboard (MDF) and particle board. Joining methods were buttand miter types. Spline materials were high density fiber board (HDF).The penetration depths of plywood, wood (Carpinus betolus) and splinewere 8, 11 and 14 mm. The results showed that in both diagonal compression and tension, MDF joints are stronger than particle board joints,and the bending moment resistance under compression is higher compared with that in tension. The highest bending moment resistance under tension was shown in MDF, butt joined using plywood spline with 8 mm penetration depth, whereas under compression bending moment resistance was seen in MDF, miter joined with the HDF spline of 14 mm penetration depth.     

Study on sheet material made from zephyr strands V: Properties of zephyr strand board and zephyr strand lumber using the veneer of fast-growing species such as poplar

Zephyr strand board (ZSB) and zephyr strand lumber (ZSL) were produced using zephyr made from poplar veneer to investigate the greater utilization of low-density poplar as a structural material. These materials were then compared to ordinary plywood, laminated veneer lumber (LVL) from poplar veneer, lauan plywood, and particleboard. The bending properties (moduli of rupture and elasticity) of ZSB proved superior to those of poplar plywood: and ZSL produced from poplar veneer zephyr had bending properties greater than ordinary LVL from poplar veneer. Apparently, the conversion of the poplar veneer into zephyr material had a positive effect on bending properties. Additionally, poplar ZSB had bending properties superior to those of lauan particleboard and equal to those of lauan plywood. The internal bond strength of poplar veneer ZSB was nearly two times greater than that of lauan particleboard.Parts of this report were presented at the international symposium on the utilization of fast-growing trees, Nanjing, China, October 1994. Report IV appeared inMokuzai Kogyo 49:599, 1994     

刨花形态,树皮含量及石膏质量与石膏刨花板性能的关系

对刨花形态、树皮含量及石膏粉质量与石膏刨花板性能之间关系的研究结果表明:保持一定的刨花长度有利于提高石膏刨花板的静曲强度;石膏刨花板的静曲强度随着木刨花中树皮含量的增加而下降,但把树皮作为填料加入石密刨花板能使板子强度得以提高,不同产地的石膏粉制成的石膏刨花板性能差异很大,按建筑石膏粉标准测定的性能指标及相组成与石膏刨花板的性能之间无显著的相关关系。     

Utilization of sweet sorghum bagasse and citric acid for manufacturing of particleboard II: influences of pressing temperature and time on particleboard properties

Development of environmentally friendly particleboard made from sweet sorghum bagasse and citric acid has recently attracted attention. In this study, we investigated the effects of pressing temperature and time on physical properties, such as dry bending (DB), internal bond strength (IB), and thickness swelling (TS) of particleboard. Wet bending (WB), screw-holding power (SH), biological durability, and formaldehyde emission of particleboard manufactured under effective pressing temperature and time were also evaluated. Particleboards bonded with phenol formaldehyde (PF) resin and polymeric 4,4′-methylenediphenyl isocyanate (pMDI) were manufactured as references. Effective pressing temperature and time were 200?°C and 10 min, respectively. It was clarified that DB, IB, and TS satisfied the type 18 requirements of the JIS A 5908 (2003), and were comparable to those of particleboard bonded with PF and pMDI. The WB and SH of particleboard did not satisfy type 18 of JIS. Particleboard manufactured under effective pressing conditions had good biological durability and low formaldehyde emission. Based on the results of infrared spectra measurement, the degree of ester linkages increased with increased pressing temperature and time.     

竹塑刨花板热压工艺的研究

对竹刨花与废旧热塑性塑料共混热压工艺进行了研究,压制成一种竹塑刨花板材。分析物料配比、热压压力、热压温度、偶联剂等工艺因素对板材物理力学性能的影响。竹塑配比对板子力学性能有着重要影响,随着竹刨花含量的增加,抗弯强度有下降的趋势,竹刨花含量达到30%～40%时,其性能下降的趋势变缓,通过极差分析与方差分析优化了工艺参数。结果表明竹刨花与废旧塑料复合压制竹塑刨花板在工艺上是可行的,主要物理力学指标均达到了相关标准的要求。     

相思、桉树刨花板两步法模压工艺的研究

以相思、桉树2树种的木材加工剩余物为原料,研究两步法刨花模压板的制造工艺以及各工艺参数与板材性能的关系.结果表明:以刨花预压制坯再进行热压模压的两步法刨花模压工艺,制备具有立体结构的刨花模压装饰板材的技术路线是可行的.相思和桉树2树种的对比试验研究结果表明:相思刨花模压制品性能优于桉树刨花模压制品.按选用工艺参数,相思原料的刨花模压制品性能完全达到相关国家标准.在工艺参数与板材性能相关性研究中,板材密度对模压板表观性能、内结合强度、静曲强度等板材性能具有显著性影响;热压模压温度和热压模压时间对板材吸水厚度膨胀率有较显著影响.施胶量增加,板材的各种物理力学性能都会提高,尤其对吸水厚度膨胀率影响最为显著.     

Measurement of bending properties of wood by compression bending tests

We measured Young's modulus, proportional limit stress, and bending strength by the compression bending test and examined the applicability of the testing method by comparing it with conventional bending test methods. Long columns of todomatsu (Japanese fir,Abies sachalinensis Fr. Schmidt) with various length/thickness ratios were the specimens. A compressive load was axially applied to the specimen supported with pin ends. Young's modulus, the proportional limit stress, and the bending strength were obtained from the load-loading point displacement and load-strains at the outer surfaces until the occurrence of bending failure. Four-point bending tests were also conducted, and the bending properties obtained were compared with the corresponding properties obtained by the compression bending tests. Based on the experimental results, we believe that when the stress-strain relation is measured by the load-loading point displacement relation using specimens whose length/thickness ratio is large enough, the bending properties can be obtained properly using the compression bending test.     

Nondestructive test and prediction of modulus of elasticity of veneer-overlaid particleboard composite

The effects of grain angle, thickness of face veneer, and shelling ratio on dynamic modulus of elasticity (E) of veneer-overlaid particleboard composite (VOP) were examined by using nondestructive test. In this study, the possibility that E of VOP can be predicted by means of some empirical formula was also discussed. This study has shown that grain angle, thickness of face veneer, and shelling ratio have substantial effects on E of VOP. The E at 0° of grain angle of face veneer was the largest, decreasing rapidly with increase in the grain angle. The lowest value of E occurred at 90° of grain angle of face veneer. The relationship between grain angle of face veneer and E of VOP can be expressed in the form of Jenkin’s and Hankinson’s equations. The orthotropic properties of wood and VOP defined as the ratio E ₀/ E ₉₀ were 25.7 for wood and 4.7 for VOP. When the grain direction of face veneer was parallel to the length of the specimens, the E of VOP increased with increasing shelling ratio. VOP increased E from 125 to 179% over that of the particleboard and veneer thickness from 2.1 upto 3.6 mm. However, when the grain direction of face veneer was perpendicular to the length of the specimens, the E of VOP decreased with increasing shelling ratio. VOP decreased E from 23 to 41% over that of the particleboard and veneer thickness from 2.1 upto 3.6 mm. The relationship between E of VOP and face veneer thickness can be expressed in the form of a second-order parabolic equation. Rule of Mixture (ROM) can be used to predict E of VOP from the E of wood element and particleboard element.     

竹材水泥碎料板制造初探

用正交试验法探讨竹材碎料的预处理方法,板材密度和水泥/竹材比对产品的静曲强度,吸水率和吸水厚度膨胀率的影响规律。研究结果表明,以竹材为原料制造水泥碎料板的竹材必须进行预处理,否则不能硬化成板;竹材水泥碎料板的静曲强度随着板的密度增大而增大,吸水率随板的密度增大而降低。水泥/竹材比对吸水率无显著影响;竹材水泥碎料板的吸水厚度膨胀率是随水泥/竹材比增大而降低,与板的密度无明显关系。     

Investigation of a new natural adhesive composed of citric acid and sucrose for particleboard

The development of a natural adhesive composed of materials derived from non-fossil resources is a very important issue. In this study, only citric acid and sucrose were used as adhesive materials for particleboard. A water solution in which citric acid and sucrose were dissolved was used as an adhesive, and the manufacture of particleboard with a target density of 0.8 g/cm³ was attempted under a press condition of 200 °C for 10 min. The optimum mixture ratio of citric acid and sucrose and the optimum resin content was 25–75 and 30 wt%, respectively. The modulus of rupture (MOR) and the modulus of elasticity in bending were 20.6 MPa and 4.6 GPa, respectively. The internal bond strength (IB) was 1.6 MPa, indicating that the adhesive had excellent bond strength. The thickness swelling (TS) after water immersion for 24 h at 20 °C was 11.9 %. The board did not decompose even under more severe accelerated treatments. This meant that the adhesion had good water resistance. The MOR, IB and TS of the board were comparable to or higher than the requirement of the 18 type of JIS A 5908 (2003). Consequently, there is a possibility that a mixture of citric acid and sucrose can be used as a natural adhesive for particleboard.     

Bending and shear properties of compressed Sitka spruce

We examined the bending and shear properties of compressed wood using small and clear specimens of Sitka spruce (Picea sitchensis Carr.). For measuring the bending properties, three-point bending tests were conducted under the span/depth ratio of 14, which is standardized in the American Society for Testing and Materials [ASTM D143-94 (2005a)] and Japanese Industrial Standards [JIS Z2101-94 (1994)]. In the bending test, the load, deflection at the midspan, and strain at the bottom of the midspan were simultaneously measured, and Young’s modulus and bending strength were obtained by elementary beam theory. For obtaining the shear modulus and shear strength, asymmetric four-point bending tests were conducted using the specimens with rectangular and side-grooved cross sections, respectively, and the influence of the compression ratio on the shear properties was examined. The results are summarized as follows: (1) Young’s modulus increased with increasing compression ratio when it was determined by the load–strain relation. Nevertheless, this tendency was rather obscured when Young’s modulus was determined by the load–deflection relation. Hence, it is preferable that Young’s modulus is measured from the load–strain relation. (2) The shear modulus in the longitudinal–tangential plane was maximum at the compression ratio of 50%, whereas that in the longitudinal–radial plane was minimum at the compression ratio of 50%. (3) The influence of the compression on the bending and shear strength ratio was not significant.     

烟秆制备刨花板的力学性能研究

烟秆为烟草采摘烟口t-后的废弃物,为了更好的利用这种原料,利用不同含水率（9％、6％、3％、0％）和烟秆不同部位（上部、中部和下部）的刨花制成刨花板,测定刨花板的内结合强度、弹性模量和静曲强度,分析含水率和烟秆部位对刨花板力学性能的影响。结果表明,随着含水率从0增加至9％,刨花板的内结合强度从0．35MPa增加至0．58MPa,其弹性模量和静曲强度呈先增后减趋势,当含水率在6％时,烟秆刨花板的弹性模量和静曲强度最大。不同部位的烟秆刨花对刨花板的内结合强度、弹性模量、静曲强度有显著影响,其中,利用中部烟秆刨花制备的刨花板的内结合强度、弹性模量、静曲强度最小。利用烟秆刨花制备的刨花板其力学性能能达到国家标准的要求,因此利用烟秆制备刨花板是可行的。     

检测条件对人造板吸水厚度膨胀率测定结果的影响

研究了恒温恒湿处理和浸渍温度对人造板吸水厚度膨胀率检测结果的影响.结果表明:中密度纤维板和刨花板的测定值随着浸渍温度的升高而增大,两者存在着一定的线性关系,而胶合板则受水温影响很小;在浸渍前试件进行恒温恒湿处理与否会影响测试结果.对于刨花板和薄型中密度纤维板,进行恒温恒湿处理是必要的.     

秸秆刨花板性能分析

对普通木质刨花板、麦秸刨花板及稻草刨花板进行了密度、含水率、吸水厚度膨胀率、静曲强度和弹性模量、内结合强度、表面结合强度及握钉力的测试,结果表明,麦秸刨花板在强度方面不及木质刨花板,稻草刨花板在抗弯性能上也无法满足要求,两种秸秆板的握钉力都较差。产生上述差距的关键原因是板坯的密度,另外,与原料形态、加工工艺、机械设备等也有关系。     

Comparison of internal bond strength and compression shear strength of wood-based materials

The purpose of this study was to design a compression shear device for easy and fast measurement of the bonded shear strength of wood-based materials to replace the conventional method used to evaluate internal bond strength (IB). To assess the performance of this device, five differently sized specimens, included group I (dimension 5 × 1 cm), group II (5 × 2 cm), group III (5 × 3 cm), group IV (5 × 4 cm), and group V (5 × 5 cm) cut from commercial particleboard and medium-density fiberboard (MDF) (1.8 cm thick) were tested in compression shear. Only group V (5 × 5 cm) was prepared for the IB test. Results indicated that the compression shear strengths (CS) of particleboard and MDF, loaded in the horizontal or the diagonal direction, were greater than the IB, although a significant correlation existed between the two. This finding suggests that the IB of particleboard and MDF could be accurately estimated from the data collected by the CS test.Part of this report was presented at the Third Pacific Rim Bio-based Composites Symposium, Kyoto, December 2–5, 1996     

木材水抽提物对石膏及石膏刨花板的凝固及其性能的影响

本文研究了在商用缓凝剂(Retardan P)的存在下木材水抽提物对石膏浆料和石膏刨花板凝固时间及其强度的综合影响。结果表明:1.木材水抽提物能使石膏浆料和石膏刨花板产生缓凝,并导致强度下降,其影响程度与树种和石膏质量均有关系。2.木材水抽提物能加强Retarda P的缓凝作用,并且用两者交互作用下石膏浆料的凝固时间,可以指示石膏刨花板的凝固时间。3.石膏刨花板的静曲强度受刨花树种的影响,但缓凝剂的添加量却无显著作用。     

Evaluation of the fire endurance of mechanically graded timber in bending

AbstractThis study examined the performance of mechanically graded timber in bending when exposed to fire at various load ratios. The test specimens were 150 pieces, each with the dimensions of 60 × 120 × 3500mm. The modulus of elasticity (MOE) of 150 specimens was measured, and 60 among them were selected to formulate the prediction equation for MOE and modulus of rupture (MOR), which was used to predict the remaining 90 specimens. These were tested under fire exposure in bending using three-point loading at 11.1%, 16.7%, 33.3%, 66.7%, and 83.3% of the ultimate load. Using mechanically graded timber, which means acknowledging the actual strength of the bending member, permits fairly precise application to the targeted design load. This research confirmed that mechanically graded timber under fire exposure has the following tendencies: under the same load ratio, time to failure is independent of strength class, and, at any load ratio, the critical strength is dependent on the timber strength class. The obtained design bending strength under fire exposure using the reduced cross section method and the reduced strength method conformed to those calculated based on Eurocode 5. Following those findings, mechanically graded timber can be applied to obtain the design bending strength when taking into account the fire attack.     

Preparation of composite board using foil-laminated and plastic-laminated liquid packaging paperboard as raw materials

We investigated the properties of composite board formed using base sheets of aluminum foil-laminated and polyethylene (PE) plastic-laminated liquid packaging paperboard (LP) as an alternative to recycling these items in wastepaper stream. Boards of different specific gravities ranging from 0.55 to 0.75 were made by pressing shredded LP blended with urea resin having resin content of 6%–10% at 180°C. Subsequently, we also prepared mixed particleboard [wood (WD) particles and LP mixed], three-layered particleboard (LP as the middle layer, WD in the upper and lower layers), and wood particleboard all having resin content of 10% and various specific gravities. Static bending and internal bonding strengths and thickness swelling of the specimens were determined to examine their properties. At the same specific gravity, the properties of LP particleboards were affected by their resin content. The modulus of rupture (MOR), modulus of elasticity (MOE), and internal bond strength of the LP particleboards increased with increasing specific gravity of the boards at the same resin content, but thickness swelling of the LP particleboards showed the reverse trend. The average MOR of the LP particleboards approximated that of the mixed particleboards and was greater than those of the three-layered particleboards and wood particleboards. Internal bond strength and thickness swelling of the LP particleboards were smaller than those of the other particleboards. Based on the above observations, we deemed that LP can be made into composite boards with adequate properties either alone or mixed with wood particles.