【作者】 杨家富；

【导师】 周永钊；

【作者基本信息】 南京林业大学 ， 机械设计及理论， 2013， 博士

【摘要】 木竹复合材料的研究开发促进了竹类资源的优化利用和竹产品性能提高和用途的扩大，在一定程度上缓解了由于天然林保护工程带来的木材供应短缺。竹材强度高、韧性好、耐磨，但经级小、出材率低、加工难度大且效率低，人工速生林树种（杉木、杨木等）加工容易、效率高、机械强度差、表面硬度低，木竹复合材料将这两种材料通过科学合理组合形式和胶合工艺，有效地发挥竹材和木材各自特性。本研究从材料设计观念出发，提出木竹复合材料主动设计思想。从组分材料性能试验分析入手，结合生产工艺，提出强度预测模型，基于模态分析技术对木竹复合材料板动态特性进行试验研究，用PULSE对组分材料及木竹复合材料吸声性能进行测试研究。木竹复合材料产品设计的特点是结构设计与材料设计同时进行，不同的组分比得到不同性能复合材料。为了研究组分材料纵向、横向弹性性能，强度性能（拉、压）以及正交性对力学性能的影响，通过正交试验的方法，在常态、常态受压、浸渍塑化状态下对木/竹复合材料组分材料杨木单板和竹片进行拉伸性能和弯曲性能的试验研究。研究表明常态下杨木单板的纵向拉伸强度和弹性模量随厚度增加而增大，呈现一定的非线性关系；受不同压力作用后的杨木单板的纵向拉伸强度和弹性模量与压力不存在正比的关系，甚至随着压力的增大，单板弹性模量值会减小，纵向拉伸强度随压力增大呈上升趋势；常态受压情况下不同厚度的杨木单板纵向拉伸强度和弹性模量、弯曲弹性模量和弯曲强度随压力的增加而增加，呈二次抛物线关系；浸渍塑化塑化杨木单板的各项纵向拉伸性能较常态受压杨木单板的各项拉伸性能有了较大的提高。纵向拉伸弹强度和弹性模量、弯曲弹性模量和弯曲强度都与塑化压力呈非线性关系，经回归分析分别得到成二次抛物线关系；横纹拉伸强度小于5MPa，横纹弯曲强度值在几兆帕到十几兆帕之间，说明杨木单板的横纹抗拉性能和抗弯曲性能较差。在了解组分材料的弹性性能的基础上，进行有效弹性模量的预测。木竹复合材料是一种层叠结构，视为均匀正交各向异性材料。基于经典层合板理论，分析推导了木竹复合层合板梁的纵向有效弹性模量预测模型；根据最小势能原理，推导出木/竹复合层合板梁弯曲强度模型，利用等效梁原理，求出木竹复合层合板梁弹性模量模型。将一定工艺条件下单板的拉伸弹性模量值和弯曲弹性模量值代入模型进行计算，从计算结果可以看出，拉伸弹性模量时的计算结果比实测值小9.93%，弯曲弹性模量的计算结果比实测值大4.84%。运用模态分析理论和梁的横向弯曲自由振动理论对木/竹复合材料板的动态特性进行分析研究，基于横向弯曲振动梁理论的两种计算模型：Euler-Bernoulli梁和Timoshenko梁的横向弯曲自由振动微分方程推导出它的频率方程和动弹性模量表达式。通过分析对比，采用脉冲激励法对木/竹复合材料板的动态特性进行研究，基于CRAS V5.1软件分析得出这种新型复合材料的模态参数（固有频率、阻尼比）、动态弹性模量、物理参数及非参数模型，并与共振法和三点弯曲法进行对比研究，为木/竹复合材料的进一步研究应用提供试验依据和参考。以杨木单板和竹木复合板为研究对象，采用B&K公司生产的专业的PULSE声学测试系统，通过吸声系数测试，分别对杨木单板和竹木复合材料板的性能进行了研究。研究表明不论是杨木单板还是竹木复合材料板，高频吸声性能比低频吸声性能好，杨木单板的中高频吸声系数明显优于低频吸声性能，厚度对材料的中高频吸声系数影响较大，在所选厚度范围内，厚度越小，吸声系数越大，吸声频带就越宽，吸声能力越强，对于竹木复合材料板，吸声系数极小，说明木竹复合材料不适宜作为吸声材料。更多还原

【Abstract】 With the developments and researches of bamboo-wood composite materials, theutilization of bamboo resources and products have been improved and widen, thus helpalleviate the shortage of wood supply resulted from natural forest protective project. Bamboomaterials are strong, tenacious and wear-resisting but have longer periods, smaller outturnpercentage, greater processing difficulty and lower efficiency. Meanwhile, fast-growing trees(poplar, fir, etc.) are easy to process and more efficient but have less mechanical strength andlower surface hardness. Bamboo-wood composite materials can give effective play of theadvantages of these two types of wood since bamboo-wood composite materials are producedin a scientific reasonable combination of them through adhesion. This research starts from theconcept of material design and provides an active design method of bamboo-wood compositematerials. In the beginning, there is an analysis of the performance test of component materials,and then make a model for the prediction of strength considering production technology. Afterthat, experimental researches of dynamic characteristics of bamboo-wood composite materialsare made using modal analysis technique and test researches of absorption ability of componentmaterials and bamboo-wood composite materials are made through PULSE.When designing bamboo-wood composite materials, the structural design and design ofcomposite materials are made simultaneously and different composite materials with differentcharacteristics are produced when ratio governing changes. Experiments in which tensile andflexural properties of component materials—poplar and bamboo are tested the samples aretreated normally, under pressure or adhesive-soaked are made in the method of orthogonal tablein order to study the influences of longitudinal and transverse elastic and strength (tensile andcompressive) properties and orthogonality on the mechanical properties of component materials.The research shows that in the normal condition, longitudinal tensile strength and elasticmodulus of poplar veneers increase when veneers are thicker but they are non-linearly related.Under different pressure, there is no proportionality between longitudinal tensile strength andelastic modulus of poplar veneers. When pressure increases, elastic properties will even comedown and longitudinal tensile strength and elastic modulus keeps going up. Under the normalpressure, Longitudinal tensile strength and elastic modulus, flexural elastic properties andbending strength of poplar veneers of different thickness increase as pressure increases,showing a quadratic parabola relationship. All numbers of longitudinal tensile strength of testpoplar veneers of adhesive-soaking have greatly improved compared with poplar veneers underpressure in normal condition. Longitudinal tensile strength and elastic modulus, flexural elasticproperties and bending strength all shows a non-linearly relationship with adhesive pressure and by regression analysis, it appears to be a quadratic parabola relationship. When transversetensile strength is smaller than5MPa, transverse flexural strength falls between several MPaand a dozen or more MPa, showing transverse tensile properties and anti-flex characteristics ofpoplar veneers are quite inferior.Predictions of effective elastic modulus are made since elastic properties of componentmaterials are understood. Bamboo-wood composite material is considered as evenly orthotropicmaterial for its stepped construction. Predicting model of longitudinal effective elastic model ofbamboo-wood composite beam is analyzed using classic laminated theory and flexural strengthmodulus and elastic modulus and model of bamboo-wood composite beam is developedrespectively through principle of minimum potential energy and the equivalent beam theory.After substituting tensile and elastic modulus as well as flexural bending modulus;bendingelastic modulus in the model, it can be calculated that the measured number of flexural elasticstrength is9.93%smaller than calculated and the measured number of flexural elastic modulusis4.84%smaller than calculated.modal analysis theory and transverse flexural vibration theory are used to analyze andstudy the dynamic characteristics of bamboo-wood composite materials and two calculationmodel are based:Euler-Bernoulli beam and Timoshenko beam’s transverse bending vibrationdifferential equations are used to calculate its frequency equation and dynamic elasticequations. To provide rationale and reference for further study and utilization ofbamboo-wood composite materials, impulse excitation test is used to study their dynamiccharacteristics and modal parameters (natural frequency and damping ratio), dynamic elasticmodulus、physical parameter and non-reference models of this new composite material areanalyzed and calculated with CRAS V5.1through analysis and comparism of resonance andthree-point bending methods.Tests of absorption coefficient are made of poplar veneers and bamboo-wood compositeboard with professional PULSE acoustic test system produced by B&K company. The researchresults turn out that both show a better performance when absorbing high-pitch sounds; thepoplar veneer has an obvious better performance in absorbing high-pitch sounds than low-pitchsounds and thickness has a clear influence of medium-high-pitch sound which means thethinner the veneer is, the greater the absorption coefficient, the greater acoustic absorption bandand absorbing ability is; bamboo-wood composite materials are proved to be unfit for absorbingmaterial for the minute absorption coefficient.更多还原