长纤维增强聚酰胺制件中浇口位置对纤维取向分布的影响

首先利用模流分析软件Moldflow对长纤维增强聚酰胺制件进行最佳浇口位置分析,再取包括该最佳浇口位置等三个不同的浇口位置分析塑件中的纤维取向分布,对纤维取向的平均纤维取向、纤维取向张量、泊松比(纤维)、剪切模量(纤维)、第一主方向上的拉伸模量(纤维)、第二主方向上的拉伸模量(纤维)等六种结果进行比较,并进一步分析浇口位置对纤维取向分布的影响。结果表明,由最佳浇口位置并非得到最佳的纤维取向。     

基于纤维取向的纳米纤维滤料设计及其性能

通过基于霍夫变换的图像分析法获取静电纺纳米纤维取向分布信息,分析纤维取向对纳米纤维滤料性能的影响,并据此设计制备了中间为杂乱纤维层、两侧为相互垂直的取向纤维层构成的复合纳米纤维膜滤料。采用扫描电镜对纳米纤维膜形貌进行观察并获取SEM图像,进行了透气性、拉伸性能、孔径尺寸和过滤性能测试。结果表明,纳米纤维膜纤维分布方向拉伸断裂强度高,纤维取向各向异性比例理论值和实验值相吻合,纤维取向是影响纳米纤维膜力学各向异性的主要参数;取向纳米纤维膜滤料孔径较大且有许多微粒可逃逸的通道,其过滤效率和过滤阻力均较低,与文献中报道的数值模拟结果相一致;所设计制备的复合纳米纤维膜滤料结合了取向纳米纤维膜滤料力学性能优良和杂乱纳米纤维膜滤料过滤效率高的优点,其纵向和横向断裂强度分别为8.85MPa和8.71MPa,气流流速为25L/min时过滤效率高达99.691%。     

流动诱导注射模纤维取向数值模拟

引入了二阶取向张量来描述流动诱导纤维取向分布，利用伽辽金法建立了流动诱导纤维取向的有限元求解方程，分别采用Hand闭合近似模型和Hinch-Leal闭合近似模型，对典型的注射模平面流动行为进行了纤维取向的数值模拟。结果表明纤维的取向分布和取向程度与其受到的剪切历史和剪切速率密切相关，剪切速率是决定纤维取向分布的重要因素之一。     

注射成型纤维增强试样的机械性能模拟

采用Moldflow软件对注射成型纤维增强热塑性塑料的拉伸试样进行模拟研究.详细分析了注塑成型拉伸试样的纤维取向结构及由此引起的机械性能变化.分析表明:试样标距位置的纤维平均取向较好、皮芯结构不明显,标距外的两端部及两过渡位置的纤维平均取向不佳、皮芯结构较为明显;试样的物理性能参数受到取向影响而呈现各向异性.结合纤维取向分析、拉伸模量分析及泊松比分析,对注射法成型拉伸试样的方法进行初步探讨.     

异形聚酯纤维的结构性能研究

对几种国产的异形聚酯纤维的表面形貌、取向因子、蠕变性能进行了分析，对比了扁平、“十”字断面、中空三种不同截面聚酯纤维的形态结构，讨论了纤维形态结构对性能的影响。结果表明：聚酯纤维异形化结构显著，纤维的蠕变现象明显；通过对异形聚酯纤维取向因子的测定，表明纤维的取向因子受纤维线密度及喷丝板形状的影响；对比了不同纤维截面对纤维性能及纤维用途的影响。     

层叠单元流道对纤维取向作用的数值模拟

基于广义非牛顿流体本构方程,建立了纤维增强聚合物三维层叠单元流道注塑成型充填阶段数学模型,采用Moldex3D对短纤维增强复合材料在层叠单元流道中的注塑流动过程进行模拟,研究了层叠单元流道对纤维流动取向的影响。结果表明:入口处的纤维从开放领域进入较窄领域,取向呈随机分布状态;进入流道后,表层纤维取向度迅速提高;在接近流道出口处,纤维取向度降低,在出口截面的两侧和中间部分均出现了随机取向纤维。     

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.     

纤维增强塑料的充模流动和纤维取向的耦合仿真模型

分析充模流动、纤维取向耦合仿真的特点,在此基础上提出充模流动、纤维取向耦合仿真模型,可对充填和后充填阶段的可压缩流体的非对称流动,以及由于熔体流动引起的三维纤维取向行为进行统一建模,并且两者相互耦合,在耦合程度上考虑了由于增强纤维存在并且取向引起的熔体流动类型、流变学性质和本构方程的变化.     

CNTs/纤维增强树脂基复合材料制备及取向设计进展

综述了随机方位分布碳纳米管(CNTs)/纤维增强树脂基复合材料和取向方位分布CNTs/纤维增强树脂基复合材料的制备方法,并对CNTs在纤维增强复合材料中取向设计方法进行了归纳分析。最后,对其研究发展动向进行了展望。     

注塑工艺参数对矩形薄壁件纤维取向影响模拟研究

以矩形薄壁件为研究对象,基于Folgar-Tucker张量模型,研究了注塑工艺参数:注射时间、模具表面温度、熔体温度对纤维取向的影响,并着重探讨了注射时间对纤维取向沿厚度方向分布的影响。研究结果表明:注射时间对纤维取向的影响最显著;随着注射时间的增加,平均纤维取向程度大幅降低,而模具表面温度与熔体温度对纤维取向的影响较小,且随着注射时间的增加,核层宽度变窄,而壳层宽度变宽。     

Comparative study of micro topography on laser ablated C/SiC surfaces with typical uni-directional fibre ending orientations

Functional micro-structures on laser-ablated carbon fibre reinforced composites surfaces exhibit distinct advantages. A variety of fibre endings with different orientations may coexist on the C/SiC sectional plane, the anisotropic nature of C/SiC (carbon fibre reinforced silicon carbide) composites present a new challenge to the laser ablation process. However, few reports describing the influence of the fibre ending orientations on the laser-ablated C/SiC surface topography could be found. In this investigation, micro-ridges were established on three typical C/SiC surfaces by laser ablation, and a comparative study was performed to identify the topography variations on these laser-ablated C/SiC surfaces. The results showed that C/SiC surfaces with different fibre ending orientations present distinct surface characters (Sz, Sq) after laser ablation. Although all of the laser ablation processes are similar in nature, the fibre ending variation made the laser and material interaction different greatly. Attention should be devoted to the influence of the fibre ending orientation on surface topography formation before performing the laser ablation of carbon fibre reinforced composite materials. Finally, some typical surface defects on these laser-ablated surfaces were also discussed.     

计算机控制的短纤维补强弯管生产工艺

介绍了计算机控制短纤维补强弯管生产工艺的基本组成和优点，短纤维补强的基本原理；美国孟山都公司挤出口型的特征；纤维定向排列的影响因素；孟山都公司Ｓａｎｔｏｗｅｂ（木质纤维）的性能及其用于胶管的配合技术和制造工艺；配有高强度混炼螺杆的英国倪登公司挤出机的特点。指出短纤维是补强橡胶的很有发展前途的新型材料；倪登公司利用孟山都公司挤出口型开发的Ｃｏｍｐｕｔａｈｏｓｅ（计算机控制弯管挤出系统）具有显著优点；短纤维补强弯管在我国现有汽车维修上具有广阔的市场，并将逐渐为国产新车配套。     

Glass fibre orientation within injection moulded automotive pedal: Simulation and experimental studies

Abstract

Modelling and measurement of the fibre orientation distribution within a reinforced thermoplastic automotive clutch pedal are presented. Products have been manufactured on an injection moulding machine equipped with accurate process monitoring. The fibre orientation distributions at selected points within the pedal were measured using a fully automated, polished section/reflection microscopy image analysis system. Simulation was undertaken using commercial software with a fibre orientation prediction algorithm. The predicted fibre orientation distributions are compared with experimental results in order to assess the accuracy of the software in both thin and thick (～5 mm) sections of the pedal.     

Orientation effects during the flow of short-fibre reinforced thermoplastics

A study has been carried out to investigate molecular orientation in injection moulded bars of short glass fibre reinforced polypropylene and polyethylene. For the range of fibre concentrations encountered commercially, the fibres do not appear to have any direct effect on the matrix orientation. As the fibre concentration increases, however, the matrix orientation becomes dominated by the orientation of the fibres. These effects are interpreted in terms of current ideas of the rheology of polymer melts during injection moulding and the crystallization of polymers at fibre surfaces.     

Fibre orientation structures and their effect on crack resistance of injection moulded transverse ribbed plate

Abstract

An extensive study of the fibre orientation structures developed in a transverse ribbed plate during injection moulding, and the use of these structures to investigate the effect of local fibre orientation state on crack initiation resistance, is reported. The fibre orientation results for the ribbed plate, measured using large area image analysis system developed at Leeds University, showed that after an initial settling down period, the central core region, where the fibres are aligned perpendicular to the flow direction, decreased in size monotonically, with an associated monotonic increase in the outer shell regions, where the fibres are aligned preferentially along the injection direction. Interestingly, the level of orientation in the two regions remained almost constant: only the proportions of the two regions were found to change with flow length. Across the plate, close to the gate, the central core region was found to have a lens-like shape, while at the other end of the plate the core was thinner and also consistent in thickness across the sample width. The transverse rib was found to cause little disturbance to the fibre orientation of the base plate. The different proportions of the shell and core regions at different locations over the ribbed plate provided an ideal case to test the proposition of Friedrich that the crack resistance of a short fibre reinforced material depends on the number of fibres that are perpendicular to the crack tip. The impact test results gathered in this way confirmed this hypothesis of Friedrich.     

海泡石纤维增强酚醛复合材料的研制

介绍海泡石纤维增强酚醛复合的制备方法和应用。讨论了海泡石纤维含量和表面处理对复合材料性能的影响。试用结果表明,海泡石纤维增强酚醛复合是一种新型耐烧蚀绝热防护材料。     

Preparation of TPI-g-MAH and the application in toughened PA6

Maleic anhydride grafted trans-1,4-polyisoprene (TPI-g-MAH) was successfully prepared, and characterised through FTIR and the chemical titration method. Furthermore, effect of TPI-g-MAH on the mechanical properties of the glass fibre reinforced nylon 6 was investigated. The results show that TPI-g-MAH can improve the toughness of glass fibre reinforced PA6 composite material, and composite material has excellent comprehensive performance when the content of TPI-g-MAH reaches 4%.     

Relation between fibre distribution and post-cracking behaviour in steel fibre reinforced self-compacting concrete panels

In this research, the influence of the fibre distribution and orientation on the post-cracking behaviour of steel fibre reinforced self-compacting concrete (SFRSCC) panels was studied. To perform this evaluation, SFRSCC panels were cast from their centre point. For each SFRSCC panel, cylindrical specimens were extracted and notched either parallel or perpendicular to the concrete flow direction, in order to evaluate the influence of fibre dispersion and orientation on the tensile performance. The post-cracking behaviour was assessed by both splitting tensile tests and uniaxial tensile tests. To assess the fibre density and orientation through the panels, an image analysis technique was employed across cut planes on each tested specimen. It is found that the splitting tensile test overestimates the post-cracking parameters. Specimens with notched plane parallel to the concrete flow direction show considerable higher post-cracking strength than specimens with notched plane perpendicular to the flow direction.     

Reorientation of short steel fibres during the flow of self-compacting concrete mix and determination of the fibre orientation factor

A simple method has been developed to assess the orientation and distribution of short steel fibres in self-compacting concrete mixes during flow. The flow of self-compacting fibre reinforced concrete has been simulated using three-dimensional Lagrangian smooth particle hydrodynamics (SPH) which is simpler and more appropriate to use to simulate the flow and to monitor the distribution of fibres and their orientation during the flow. A probability density function (PDF) has been introduced to represent the fibre orientation variables in three dimensions. Moreover, the orientation variables of each individual fibre in an arbitrary two dimensional cross-section have been calculated using the geometrical data obtained from the three dimensional simulations. From these a new definition of the fibre orientation factor has been introduced and a method proposed for its determination from the fibre orientations monitored during the simulations. It is shown that this new definition gives results that are consistent with the expected reorientation of fibres towards the principal direction of flow. A method has also been proposed for its determination from image analysis on cut sections.     

Structure and mechanical properties in injection moulded discs of glass fibre reinforced polypropylene

Edge-gated discs of glass fibre reinforced polypropylene have been produced over a range of injection moulding conditions. Examination of the structure of the discs has shown that injection moulding conditions which resulted in retained fibre length in the mouldings also produced serious fibre agglomeration and increased voiding. However, despite this agglomeration and voiding, average mechanical properties were still improved for the disc with retained fibre length. Fibre orientation distribution showed little variation over the range of moulding conditions.