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.     

竹篾厚度及排列方向对竹篾层积材性能影响

以毛竹竹篾为研究对象,考察了竹篾厚度及排列方向对竹篾层积材物理力学性能的影响。结果表明:竹篾厚度变化对竹篾层积材的物理力学性能影响非常显著。随着竹篾厚度的增加,竹篾层积材的24小时吸水厚度膨胀率和浸渍剥离率都明显增加,静曲强度值和弹性模量值减小;竹帘方向对各项物理力学性能的影响显著,其影响程度大小分别为24h吸水厚度膨胀率>浸渍剥离率>弹性模量>静曲强度。竹帘方向层与层之间互为垂直时,压制的板材的各项物理力学性能较层与层顺向排列的板材对应性能均大幅下降,尤其是板材的24小时吸水厚度膨胀率和浸渍剥离率的值变化最大。     

Mechanical properties of aramid fiber reinforced polymer confined laminated bamboo lumber column under cyclic loading

European Journal of Wood and Wood Products - This paper explores the effect of using fiber-reinforced polymer (FRP) wrap on the hysteresis curve, skeleton curve, bearing capacity, stiffness and...     

Effect of knots on the flatwise bending stiffness of lumber members

In machine stress-rating of lumber where flatwise bending stiffness is used as a predictor of strength, it is customary to assume that the effect of knots is accounted for by stiffness. However, only few data in the published literature can be used to substantiate this claim. The present study was undertaken to evaluate the relationship between stiffness and knot size for lumber members loaded in bending with a test geometry similar to that used by grading machines. Experiments were carried out with spruce lumber specimens containing a single centerline knot. A theory-of- elasticity based model was derived for analysis purposes. Theory and experiments agreed in showing that the effect of knots on flatwise bending stiffness is very small. This low sensitivity may explain why correlations between strength and machine measured stiffness are rather poor for commercial lumber. Implications of this finding on the practice of machine stress-rating of lumber are discussed.     

竹篾层积材在建筑结构中的研究及应用

竹篾层积材由于其良好的物理力学特性,可制造成梁、檩、柱、椽等主要承载构件,并逐步应用于现代竹结构示范建筑中.文章简要介绍了竹篾层积材的制造工艺、影响因子及产品性能,并阐述了在建筑结构中的研究应用现状及存在的问题,为其在建筑方面的发展提供参考     

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.     

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.

---

     

竹篾层压板的力学性质及耐老化性能研究

利用靠近竹青和靠近竹黄的竹篾分别生产层压板,对其抗弯、抗压力学性质及其耐老化性能进行比较研究,为竹材的优化利用提供基础资料。研究结果表明:利用靠近竹青的竹篾制备的层压板的抗弯抗压力学性能远远高于利用靠近竹黄的竹篾制备的高低两种密度的层压板的性能。在实验室加速老化处理后利用靠近竹青的竹篾制备的层压板的抗弯弹性模量、抗弯强度和顺纹抗压强度的保留率都很高,表现出很强的抗老化能力;利用靠近竹黄的竹篾制备的层压板的顺纹抗压强度的保留率也比较高,而抗弯弹性模量、抗弯强度保留率较低,特别是利用靠近竹黄的竹篾制备的低密度层压板的抗弯强度保留率最低;利用靠近竹青的竹篾制备的层压板、利用靠近竹黄的竹篾制备的高密度层压板的厚度变化率都较高,而利用靠近竹黄的竹篾制备的低密度层压板的厚度变化率最低。本研究的结论表明:竹篾性能对层压板的性能有重要的影响,竹篾分类利用对于促进竹材的适材适用和高效利用具有一定的意义。     

竹原/亚麻复合材料力学性能的模糊评判

采用竹原纤维、亚麻纤维作为增强体,低熔点聚酯纤维(LMPET)及丙纶纤维(PP)做基体,通过非织造工艺制作混合纤维预成型件,采用模压成型工艺制作植物纤维增强复合材料。用模糊综合评判的方法,探讨增强相与基体相选用的纤维种类及纤维质量百分率对材料力学性能的影响。利用扫描电镜研究了复合材料拉伸断口的形貌。结果表明:LMPET/40%竹原纤维复合材料的力学性能最优,纵、横向拉伸强度分别为136.00 MPa和87.58 MPa;纵、横向弯曲强度分别为534.00 MPa和470.00 MPa,超过了普通工程塑料的水平。     

Photogrammetric evaluation of shear modulus of glulam timber using torsion test method and dual stereo vision system

European Journal of Wood and Wood Products - The shear modulus of timber and timber-based composite materials is a fundamental mechanical property, which is used in the design of timber and...     

混纺比对棉与竹浆/棉纱交织物弯曲性能的影响

 为进一步利用竹浆纤维的特性开发优良面料,采用了5种不同混纺比的竹浆/棉混纺纬纱与纯棉经纱交织,共设计开发了15种不同规格的面料,对其悬垂性、刚柔性、折皱性进行测试比较。结果表明：和纯棉织物比较,棉与竹浆/棉纱交织物的悬垂性、刚柔性和抗皱性得到显著改善;随着纬纱混纺比中竹浆纤维含量的增加,交织物静、动态悬垂因数减小,悬垂感和形态效果得到有效改善;交织物的抗弯刚度和抗弯弹性模量减小,柔软性提高;交织物弹性回复角增大,折皱回复性能提高,其抗皱性也显著提高;当织物组织、原料及经密相同时,随着交织物中纬密的增大,其悬垂性和刚柔性变差,织物的急、缓弹性回复性能呈下降趋势。当竹浆/棉纬纱混纺比为55/45时,其服用织物形态对称性较差,应慎重选用。     

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.     

我国竹材材性与加工利用研究新进展

简要介绍了竹类资源,竹材材性和加工利用的研究现状;重点分析了毛竹和其它竹种的材性,材性与培育和加工利用的相关关系;比较了现有竹质人造板产品、竹炭、竹纤维、竹醋液等研究概况.提出了关于竹材材性研究和利用的几点建议.     

Analysis of bending properties of worsted wool yarns and fabrics based on quasi-three-point bending

Abstract

The bending behavior of worsted wool yarns and fabrics plays a crucial role in handling and performance of end-use textiles. Hence, the fabric/yarn bending properties were studied based on a quasi-three-point bending model by means of the theoretical modeling and the corresponding measuring method. By means of the formula and the measured curves, the curve of bending rigidity and the curvature of a fabric or a yarn can be calculated so as to characterize the bending behavior more precisely than in the previous work. All the experiments on the fabric/yarn bending rigidity have been conducted for both the worsted wool fabrics and the corresponding yarns procured from the fabrics, with the same apparatus bending evaluation system of fabric and yarn, which was developed independently. The measured results of bending rigidity and curvature curve show good correlation with the bending moment and the curvature relationship of the theoretical modeling, and the comparisons of bending rigidity among KES-FB2 (Kawabata Evaluation System for Fabrics-2 pure bending tester), FAST-2 (Fabric Assurance by Simple Testing-2 bending meter), and the independently developed apparatus show that the three systems exhibist reasonably high correlations. It is confirmed that the new apparatus and the theoretical model are both viable and precious. Meanwhile, the theoretical relationship between the yarns and the fabrics has also been discussed, and the theoretical analysis of the bending behavior between the yarns and the fabrics is helpful in selecting a better theoretical model of the fabric-to-yarn bending rigidity ratio.     

竹纤维针织物性能的研究

采用实验测试与理论分析的方法,研究了不同组织结构的竹纤维针织物的服用性能。认为各种组织的竹纤维针织物都具有良好的透气性和抗皱性,织物柔软性较好,但抗起毛起球较差。该研究可作为竹纤维针织服装的开发基础。     

竹原纤维的分级提取及其性能

为探究不同竹龄及不同取材部位竹原纤维性能的变异规律,以不同竹龄、不同部位的慈竹为原料,采用物理化学结合的方法提取竹原纤维,并分别测定竹原纤维的化学组成、纤维的表面形貌、纤维的密度、吸湿性能、拉伸强度。结果表明：相同部位竹原纤维,随竹龄的增加,纤维的密度先增大后减小,纤维的回潮率先减小后增大;相同竹龄竹原纤维,随着距地高度的增加,纤维密度增加,回潮率先稍有降低后升高。3年生慈竹梢部纤维密度最大,为1.70 /cm3,4年生的基部纤维密度最小,为1.51 g/cm3。3年生慈竹中部纤维回潮率最低,为12.94%,其不同部位竹原纤维拉伸强度较为稳定,4年生中部竹原纤维拉伸强度最大,为787.42MPa。     

竹纤维针织物的性能分析

分别采用18.2tex的纯竹纤维纱和棉纤维纱在30G多针道单面机上织成布样,并进行织物性能测试和比较分析。结果表明,竹纤维针织物的透气性、悬垂性、折皱回复性均优于棉针织物的,而抗起毛起球性能比后者的差。     

再生竹纤维素纤维热学和拉伸性质的研究

利用DTG和DSC技术对再生竹纤维素纤维的热学性质进行了测试和分析,测试结果显示,再生竹纤维素纤维的DTG和DSC曲线与其他纤维素纤维相似,随着温度升高,纤维因水分蒸发而损失质量,约120℃时达到稳定;230-240℃时,纤维中的油剂开始分解;空气中,再生竹纤维素纤维305.7-330.2℃发生热裂解;氮气中,竹纤维素纤维的热裂解从310.5℃开始,到351.1℃结束。竹纤维素纤维在升温过程中没有出现熔融现象,其湿润状态下的断裂强力和断裂伸长率均较干态为低。     

基于单片机的单板层积材抗弯强度应力波波速检测系统

介绍了一种自主开发的单板层积材应力波弹性模量检测系统.该系统以单片机为数据处理核心,通过在线检测应力波的波速及相关参数来计算单板层积材的动态弹性模量和抗弯强度,进而实现单板层积材强度的分等.文中讨论了系统的检测原理,给出了具体的硬件实现电路、软件设计,并对系统进行了实验验证.