基础理论

<正>TQ 340.120144009纤维悬浮液的结构和流变性能Eberle Aaron P.R.…;Applied Polymer Rheology,2012,p.113(英)综述了纤维悬浮液的流变性能以及流变性能与微观结构之间的联系。文章中收录了目前对长、短纤以及牛顿、非牛顿悬浮介质的理论加工方法。此外,还讨论了流变性能的实验研究,以及流变性能     

短纤维复合材料注射成型纤维取向数值模拟研究进展

综述了国内外短纤维复合材料注射成型过程中纤维取向数值模拟的研究成果,包括纤维取向的描述、复合体系流变模型、工艺参数对纤维取向的影响和纤维取向数值模拟状况.展望了该领域的发展趋势.     

PBS/蒲草纤维复合材料的制备与性能

用蒸汽爆破后的蒲草纤维与聚丁二酸丁二醇酯(PBS)制备复合材料,研究蒲草纤维的质量分数对复合材料力学性能、热学性能以及流变性能的影响。研究结果表明:随着蒲草纤维组分的增加,复合材料的弯曲强度和弯曲模量有明显提高,而冲击强度呈现先增大后减小的趋势,当蒲草纤维质量分数为5%时,冲击强度达到最大值5.49 k J/m2。热重分析结果表明蒲草纤维与PBS基体间存在互补作用使复合材料在高温条件下的热稳定性提高。DSC结果表明:随着蒲草纤维质量分数的增加,复合材料的结晶度和熔融温度都呈现增大趋势。平板流变结果表明:蒲草纤维降低了PBS分子的运动能力,增加了复合材料的黏度。     

基于Moldflow复合材料注射压缩成型纤维取向模拟

依据Folgar-Tucker纤维取向模型及广义非牛顿流体本构方程,采用Solidwoks软件创建了复合材料制品的三维模型,将模拟纤维在模腔中的注射压缩成型流动过程导入Moldflow软件中.对比了注射成型与注射压缩成型得到的制品中碳纤维取向程度,并预测复合材料在该取向上的导热性能.研究结果表明,制品厚度、纤维含量是影...     

短亚麻纤维/聚乳酸复合材料制备与性能研究

采用双螺杆挤出机制备出一系列短亚麻纤维/聚乳酸复合材料,通过力学性能测试、SEM和DSC等方法研究了短亚麻纤维用量、偶联剂种类对短亚麻纤维/聚乳酸复合材料力学性能、结晶性能、流变性能和耐热性能的影响。结果表明:短亚麻纤维用量达到4.62%时,亚麻纤维/聚乳酸复合材料力学性能达到最佳;随短亚麻纤维用量的增加亚,麻纤维/聚乳酸复合材料流动性降低而,结晶度和耐热性有所提高。     

短纤维在氯丁橡胶中的应用

研究了短纤维种类、用量及长度对短纤维/氯丁橡胶复合材料的纤维取向、纤维分散、力学性能、耐热性能以及溶胀性能的影响。结果表明,复合材料呈现明显的各向异性;3mm短纤维/氯丁橡胶(CR)复合材料的纤维取向度、拉伸强度、撕裂强度和耐溶胀性能均优于1mm复合材料,短纤维分散性对复合材料耐热性的影响较小。     

玄武岩纤维沥青高低温流变特性研究

为研究玄武岩纤维不同形态对沥青高低温流变性能的影响,通过动态剪切流变试验(DSR)和低温弯曲梁流变试验(BBR)对掺量为1%、2%、3%的玄武岩纤维沥青进行高低温流变性能指标进行测定。试验结果表明:丝状玄武岩纤维较束状在沥青中有更好的分散程度,充分发挥了纤维的作用。随着纤维掺量的增加,车辙因子也逐渐的增加,玄武岩纤维对沥青抵抗高温变形的能力有着很好的增强效果。纤维的加入对沥青的低温性能有一定的影响,随着掺量的增加,纤维沥青的劲度模量(s)逐渐增加,蠕变速率(m)逐渐减小,虽增加了抵抗恒载的能力,但也牺牲了变形恢复的能力。     

短剑麻纤维增强聚苯乙烯复合材料的拉伸性能

研究了短剑麻纤维和苯甲酰化剑麻纤维增强聚苯乙烯的拉伸性能，评价了剑麻纤维长度，含量，取向及苯甲酰作用对这种复合材料拉伸性能的影响。     

PBT/PET并列型复合纤维后加工条件探索

本文研究了PBT/PET并列型复合纤维在不同的松弛热定型和假捻变形工艺条件下,纤维卷曲度、卷曲收缩性能以及纤维结构之间的关系。试验表明复合纤维的卷曲性能随着热定型温度和变形温度的上升而增加,当温度升到某一值时超于平衡,本文还表明纤维卷曲性能与纤维中大分子链的解取向和结晶度有关。随着温度的增加,取向度下降,结晶度上升,卷曲性能亦上升。且证明了PBT/PET并列型复合纤维经假捻变形后其卷曲度、卷曲收缩率、卷曲模量、卷曲稳定性处于最佳状态,经机织后织物的弹性可达23％以上。     

纤维增强聚合物注塑件力学性能耦合数值分析

基于聚合物复合材料的各向异性机理,建立了纤维增强聚合物注塑件各向异性力学模型,以标准拉伸试样为研究对象,通过网格映射法集成Moldflow和Abaqus,实现纤维增强聚合物复合材料注塑流动和结构分析的耦合。结合塑件纤维取向和残余应力,分析浇口位置及数量对塑件力学性能的影响,结果表明,在给定塑件及载荷条件下,边浇口变形最小,中心浇口次之,两浇口变形最大。以上结果对提升塑件结构分析的精度具有重要意义。     

纸桨泵叶轮中纤维悬浮湍流的流动特性(英文)

A numerical method for predicting fiber orientation is presented to explore the flow properties of turbu-lent fiber suspension flowing through a stock pump impeller. The Fokker-Planck equation is used to describe the distribution of fiber orientation. The effect of flow-fiber coupling is considered by modifying the constitutive mode. The three-dimensional orientation distribution function is formulated and the corresponding equations are solved in terms of second-order and fourth-order orientation tensors. The evolution of fiber orientation, flow velocity and pressure, additional shear stress and normal stress difference are presented. The results show that the evolutions of fiber orientation are different along different streamlines. The velocity and its gradient are large in the concave wall region, while they are very small in the convex wall region. The additional shear stress and normal stress difference are large in the inlet and concave wall regions, and moderate in the mid-region, while they are almost zero in most downstream regions. The non-equilibrium fiber orientation distribution is dominant at the inlet and the concave wall regions. The flow will consume more energy to overcome the additional shearing losses due to fibers at the inlet and the concave wall regions. The change of flow rates has effect on the distribution of additional shear stress and normal stress difference. The flow structure in the inlet and concave wall regions is essential in the resultant rheological properties of the fiber suspension through the stock pump impeller, which will directly affect the flow efficiency of the fiber suspension through the impeller.     

短玻纤增强聚丙烯的研究进展

综述了近年来有关短玻纤增强聚丙烯复合材料的力学性能、变形机理和断裂韧性等方面的研究工作。短玻纤取向后的复合材料注射样的力学性能是各向异性的 ,复合材料在取向方向上具有更高的拉伸强度。玻纤与树脂基体间界面结合力的强弱对材料的力学性能同样起着至关重要的作用。良好的界面结合力保证了应力有效地从基体向玻纤传递 ,从而提高了复合材料的强度。由于短玻纤的分布既不均匀又不规则 ,在受到负荷时的变形过程很复杂 ,包括玻纤 -基体的界面脱黏、脱黏后的摩擦、基体的塑性变形、玻纤的塑性变形、玻纤断裂、基体断裂和玻纤抽出等     

搅拌过程和流变性对水泥基材料中纤维分布及力学性能影响

纤维增强水泥基设计复合材料( ECC)具有高延性特征,而成型过程影响纤维在水泥基体内分布状态,进而影响ECC获得高延性性能的稳定性。本文综述了ECC搅拌过程和拌合状态下的流变性能对纤维分布的影响,重点分析了塑性黏度和屈服应力对纤维分布及力学性能的影响。结果表明：后加纤维的搅拌过程是ECC成型过程中纤维分布的最优方式;良好的塑性黏度是保证纤维均匀分布的关键,屈服应力影响纤维分布及取向分布;综合调整ECC的流变性可以保证纤维均匀分布,使硬化后ECC获得稳定的高延性。     

离子液体法新型再生纤维素纤维的研究

采用离子液体1-乙基-3-甲基咪唑醋酸盐([EMIM]Ac)为溶剂,制备了纤维素/[EMIM]Ac溶液,研究了该体系的流变性能,利用干喷湿纺的方式制备的新型再生纤维素纤维,并对纤维的结构与性能进行了分析。结果表明,纤维素/[EMIM]Ac溶液为典型的切力变稀流体,在较高剪切速率下,纺丝溶液的黏度变化较小;由该体系制备的新型再生纤维素纤维具有纤维素Ⅱ晶型的结构;随着拉伸比的提高,纤维的取向程度及结晶度增大,纤维力学性能提高。以离子液体为溶剂制备的再生纤维素纤维表面光滑,质地紧密。     

以离子液体为溶剂的纤维素纤维的结构与性能

以离子液体氯化1-丁基-3-甲基咪唑([BMIM]Cl)为溶剂,制备了纤维素/[BMIM]Cl溶液,探讨了该体系的流变性能,并对所纺得的纤维素纤维的结构与性能进行了分析。结果表明:纤维素/[BMIM]Cl溶液为切力变稀流体,当剪切速率较大时,温度对体系黏度几乎没有影响,因此可以在较高剪切速率下降低纺丝温度;由该体系纺制的纤维具有纤维素II晶型的结构;随着拉伸比的提高,纤维的取向程度及结晶度增大,从而使纤维力学性能提高,所得纤维的表面光滑、结构致密,其染色性能及抗原纤化性能与Lyocell纤维基本相近。从而证明了用离子液体[BMIM]Cl所纺制的纤维素纤维性能良好,可望成为继Lyocell纤维之后的又一新型绿色纤维素纤维。     

Numerical investigation of three-dimensional fiber suspension flow by using finite volume method

Fiber suspension flow is common in many industrial processes like papermaking and fiber-reinforcing polymer-based material forming. The investigation of the mechanism of fiber suspension flow is of significant importance, since the orientation distribution of fibers directly influences the mechanical and physical properties of the final products. A numerical methodology based on the finite volume method is presented in the study to simulate three-dimensional fiber suspension flow within complex flow field. The evolution of fiber orientation is described using different formulations including FT model and RSC model. The pressure implicit with splitting of operators algorithm is adopted to avoid oscillations in the calculation. A laminate structure of fiber orientation including the shell layer, the transition layer and the core layer along radial direction within a center-gated disk flow channel is predicted through a three-dimensional simulation, which agrees well with Mazahir’s experimental results. The evolution of fiber orientation during the filling process within the complex flow field is further discussed. The mathematical model and numerical method proposed in the study can be successfully adopted to predict fiber suspension flow patterns and hence to reveal the fiber orientation mechanism.     

氯化铵改性Lyocell纤维的制备及其热处理

研究了不同NH4Cl含量的纤维素／NMMO·H2O溶液的流变性能,在此基础上制备了NH4Cl改性Lyocell初生纤维,并探讨了NH4Cl添加量及后续热处理对纤维结构与性能的影响。结果发现：随着NH4Cl添加量的增加,纤维素溶液体系的表观黏度、结构化程度、表观相对分子质量增加而表观相对分子质量分布变窄。结合广角X-射线衍射和双折射分析结果还发现：对Lyocell纤维采用NH4Cl改性或进一步结合热处理,都可以有效提高纤维的结晶度和取向度,完善最终纤维的聚集态结构。对纤维的性能分析结果表明：在本研究条件下,当NH4Cl添加量为5％时,经适当条件热处理后,最终得到Lyocell纤维断裂强度7．21cN／dtex、初始模量92．6cN／dtex、干热收缩率小于0．8％,并且蠕变率也有一定的下降．     

Fiber orientation control of short‐fiber reinforced thermoplastics by ram extrusion

In this study we examine the fiber orientation distribution, fiber length and Young's modulus of extruded short‐fiber reinforced thermoplastics such as polypropylene. Axial orientation distributions are presented to illustrate the influence of extrusion ratio on the orientation state of the fibrous phase. Fibers are markedly aligned parallel to the extrusion direction with increasing extrusion ratio. The orientation state of extruded fiber‐reinforced thermoplastics (FRTP) is almost uniform throughout the section. The control of fiber orientation can be easily achieved by means of ram extrusion. Experimental results are also presented for Young's modulus of extruded FRTP in the extrusion direction. Young's modulus follows a linear trend with increasing extrusion ratio because the degree of the molecular orientation and the fiber orientation increases. The model proposed by Cox, and Fukuda and Kawada describes the effect of fiber length and orientation on Young's modulus. The value of the orientation coefficient is calculated by assuming a rectangular orientation distribution and calculating the fiber distribution limit angle given by orientation parameters. By comparing the predicted Young's modulus with experimental results, the validity of the model is elucidated. The mean fiber length linearly decreases with increasing extrusion ratio because of fiber breakage due to plastic deformation. There is a small effect on Young's modulus due to fiber breakage by ram extrusion.     

Processing of short‐fiber reinforced polypropylene. I. Influence of processing conditions on the morphology of extruded filaments

An experimental investigation of the processing of glass fiber reinforced polypropylene is presented. Final fiber orientation distribution, fiber distribution in filament sections, rheological properties, final fiber length distribution and surface morphology were analyzed. This analysis was done taking into account the quantity of fibers and their interactions and flow conditions. The final fiber orientation increased when shear rate increased and fiber concentration decreased. Moreover, inhomogeneities in fiber distribution increased as the concentration of fibers decreased. The density profile showed a significant variation with fiber concentration, but it was not dependent on the shear rate applied. The viscosity showed a linear dependence with shear rate. The average fiber length and the breadth of this distribution decreased with the increasing fiber concentration and extrusion rate. The extruded filament surface showed minor roughness when the shear rate increased or when the fiber concentration decreased. The results of this experimental characterization give useful information to determine the influence of the processing variables on the final properties of short‐fiber reinforced polypropylene and constitutes the first part of a more ambitious project that also includes the development of a modeling strategy of the processing behavior for short‐fiber composites.     

The prediction of flow and orientation behavior of short fiber reinforced melts in simple flow systems

A model for the prediction of changes in fiber orientation in simple flows of fiber suspensions is proposed. Fiber interactions are modeled as randomizing forces over the rotation of fibers in closed orbits in simple shear. The resulting Fokker-Planck type convection-diffusion equation in orientation space is solved using a finite difference technique. The solution technique permits the use of periodic boundary condition for the convection-diffusion equation and different initial conditions for the orientation distribution. The model predictions for simple shear flow demonstrate the interaction between the structural changes and the bulk rheological properties. The effect of non-Newtonian fluid properties on the orientation distribution was also incorporated at the slow flow limit. Structural changes are assumed to be irreversible. The irreversibility is incorporated through an orientation distribution dependent diffusion coefficient.