短纤维交错排布复合材料沿轴等效模量的理论预测

该文针对高性能短纤维交错排布复合材料的刚度预测发展了三维"拉伸-剪切链"模型,并通过了有限元(FEM)计算验证,能够合理地预测短纤维交错排布复合材料的等效模量。验证结果显示,对于纤维长细比的变化、纤维体积含量的变化、纤维和基体间弹性模量比的变化,三维"拉伸-剪切链"模型都可以给出合理的预测,为短纤维交错排布复合材料的刚度设计提供了理论指导和参考依据。研究还显示,同样纤维体积含量和长细比下短纤维交错排布复合材料的等效模量远大于短纤维对齐排布的等效模量,说明了短纤维交错排布结构的优越性。     

随机短纤维复合材料层与刚性平面的滚动接触特性研究

借助于Eshelby等效包容理论及粘弹性基础假设，对随机短纤维增强复合材料层与刚性平面的滚动接触问题进行了理论研究，分析了短纤维长径比和体积分数对滚动接触特性的影响，数值结果表明，滚动接触宽度和滚动摩擦系数均随纤维长径比和体积分数的增大而减小；等效接触应力分布不对称，最大等效接触应力随着纤维长径比和体积分数的增大而增大...     

短纤维橡胶复合材料强度的理论研究I 纵向拉伸强度的理论预测

首次在较宽的纤维用量和纤维长度范围内, 研究了短纤维橡胶复合材料的拉伸强度规律, 并基于Cox 剪滞法和复合材料的结构特点, 提出了一种新的混合定律模式, 对复合材料的纵向拉伸强度进行了理论预测。结果表明, 新的模型包含结构因素较全面, 理论计算值与实验值符合较好。此外, 探讨了复合材料的拉伸破坏机理, 认为复合材料的拉伸破坏主要由界面控制, 在复合材料中存在着界面剪切应力集中和纤维拉伸应力集中之间相互竞争增长的过程, 但前者的增长制约着后者的增长。本文是短纤维橡胶复合材料强度理论预测的第一部分。      

短纤维增强橡胶复合材料研究进展

综述了短纤维增强橡胶复合材料制备过程中短纤维的预处理、短纤维的混合、分散、取向方法及影响因素 ,并介绍短纤维增强橡胶复合材料的新进展     

短纤维增强橡胶复合材料研究进展

综述了短纤维增强橡胶复合材料制备过程中短纤维的预处理、短纤维的混合、分散、取向方法及影响因素，并介绍短纤维增强橡胶复合材料的新进展。     

基体合金种类对SiCw／Al复合材料拉伸性能的影响

对SiCw/LD2、SiCw/LC9复合材料进行了热挤压加工并沿其纵向进行了拉伸对比试验。结果表明:SiCw/LD2的抗拉强度为590MPa,而SiCw/LC9复合材料的抗拉强度高达750MPa。SEM分析发现,上述两种复合材料均为切应力作用下的韧窝形断口,但SiCw/LD2的断口有明显的晶须拔出。低于临界长径比的晶须被拔出是SiCw/LD2断裂的主要形式;高于临界长径比的晶须被拉断是SiCw/LC9断裂的主要形式;基体合金的不同导致了复合材料具有不同的晶须临界长径比,这也是SiCw/LC9复合材料较SiCw/LD2复合材料有更高抗拉强度的根本原因。     

PA66短纤维/天然橡胶复合材料的制备及性能研究

尼龙66(PA66)短纤维具有质轻、强度高、耐热性强等优良性能,是橡胶复合材料中常用的增强材料。为改善纤维和橡胶的界面粘结,首先采用高效环保的紫外光辐照纤维表面,在此基础上接枝端羧基液体橡胶进行改性,制备了PA66短纤维/天然橡胶复合材料,考察了紫外光辐照时间对纤维及复合材料性能的影响。结果表明,紫外光辐照PA66短纤维表面4min,浸渍2g液体橡胶后,PA66短纤维/天然橡胶复合材料的100%定伸应力提高了11.3%,300%定伸应力提高了9.23%,PA66短纤维与天然橡胶复合材料的界面粘结效果得到明显改善。     

基于周期性边界条件的炭黑填充橡胶复合材料力学行为的预测

在分析炭黑填充橡胶复合材料的宏观与细观特征之间联系的基础上,提出了具有随机分布形态的代表性体积单元,推导并应用了周期性细观结构的边界约束条件,建立了三维多颗粒夹杂代表性体积单元的数值模型,对炭黑填充橡胶复合材料的宏观力学行为进行了模拟仿真。研究表明,该模型通过周期性边界条件的约束保证了宏观结构变形场和应力场的协调性;计算得到的炭黑填充橡胶复合材料的弹性模量明显高于未填充橡胶材料,并随着炭黑颗粒所占体积分数的增加而增大;该模型对复合材料有效弹性模量的预测结果与实验结果吻合较好,而且比Bergstrom三维模型的预测结果更好,证实了该模型能够用于炭黑颗粒增强橡胶基复合材料有效性能的模拟分析。     

尼龙6短纤维—NR／SBR复合材料的研究

用RFL溶液作为纤维的增粘处理剂,研究了尼龙6短纤维-NR/SBR复合材料的物理机械性能和应力松弛特性;并利用抗平衡溶胀法(RES)和SEM分析了纤维与橡胶基质间的粘着效应以及复合材料的形貌结构。结果表明,经RFL处理的尼龙6短纤维与橡胶产生了强的粘着,并具有良好的分散性和取向性,从而使橡胶的物理机械性能得到很好的改善,并赋予复合材料显著的力学各向异性。     

单向短纤维增强复合材料应力传递模型及其细观力学分析

建立了含单纤维和基体的双圆柱复合材料细观力学模型,采用基体剪应力的Lame形式推导了纤维轴向应力和纤维基体间界面剪应力计算方程。分析了纤维/基体模量比、纤维长径比和纤维体积分数等细观结构参数对纤维轴向应力和界面剪应力分布的影响,并对结果进行了验证。     

Nylon／SBR／NR复合材料的基本性能研究

研究了短纤维（Ｎｙｌｏｎ－６）补强弹性体（ＳＢＲ／ＮＲ）的基本物理机械性能，并对Ｎｙｌｏｎ／ＳＢＲ／ＮＲ复合体系在应力作用下的破坏结构进行了电子显微镜扫描。试验表明：短纤维形状系数，短纤维体积分数、弹性体基质与短纤维的粘合强度和短纤维在弹性体基质中的取向是影响Ｎｙｌｏｎ／ＳＢＲ／ＮＲ复合材料物理机械性能的主要因素。控制这４个变化因素，就能有效地设计其机械性能。     

The effect of non-symmetric distribution of fiber orientation and aspect ratio on elastic properties of composites

A composite’s microstructure significantly influences its overall properties. Orientation and aspect ratio of the fiber are two key parameters that describe the microstructures of a composite with straight short fibers. This paper discusses the effects of fiber orientation and aspect ratio distribution on the overall elastic properties of composites using the Mori–Tanaka’s method in this paper. The results show that using an average aspect ratio of the fibers to estimate overall elastic properties is not appropriate under some conditions. When the aspect ratio of the fibers does not follow a symmetric distribution, the overall elastic properties obtained by the average aspect ratio of the fibers may differ by more than 30% from those obtained by the method considering the aspect ratio distribution. This paper presents a model used to predict the properties of nanotube-reinforced composites. The results obtained by the model were compared with experimental results.     

A design approach for the mechanical properties of polypropylene discontinuous fiber reinforced cementitious composites by extrusion molding

Polypropylene discontinuous fiber reinforced cementitious composites were prepared by extrusion molding and tested in uniaxial tension to determine the mechanical properties such as ultimate composite strength and strain, and the critical volume fraction for multiple cracking. It was shown that the experimentally determined critical fiber volume fraction reasonably agreed with the theoretical value predicted by a micromechanics model. The extruded fiber composites yielded the ultimate composite strength of 9.0 MPa and composite strain of 0.55% at the fiber volume fraction of 7.4%. Our experimental results suggest that there is an optimal fiber aspect ratio and fiber volume fraction for enhancing the fracture properties.     

纤维长径比对环氧复合材料动态力学性能的影响

本文研究不同纤维长径比对碳纤和玻纤环氧复合材料动态力学性能的影响.结果表明,随长径比的增大,材料的力学内耗下降而模量增加;在低长径比,碳纤复合材料的内耗值比玻纤复合材料的高.达到一定长径比后,内耗值和模量值趋于连续纤维复合材料的值.温度越高,基体模量下降,达到相同纤维刚度的使用效率所需要的长径比就越大.用材料在外载荷或热缩应力作用下,纤维及其界面上沿纤维方向上的应力大小和分布随长径比的变化规律解释上述现象.     

A New Model for the Transverse Modulus of Unidirectional Fiber Composites

In this paper a new micromechanical model for predicting the transverse modulus of unidirectional continuous and discontinuous fiber composites is proposed. This model is based on modeling a composite with a regular array of volume elements and constructing a stress pattern based on simple averaging procedures in the direction transverse to the fiber axis for a representative volume element. The effects of fiber aspect ratio, interfiber spacing and fiber end gap on the transverse modulus of discontinuous fiber composites are discussed in detail. The predictions of the model are compared with existing experimental results for various fiber/matrix systems and very good agreement is found. The present model has advantages over other existing models not only because the effects of fiber aspect ratio, interfiber spacing and fiber end gap are taken into account and the expression for the transverse modulus of composites is simple in form but also because the present model gives precise predictions of the transverse composite modulus.     

短纤维橡胶基复合材料模量的理论预测

基于Ｈａｌｐｉｎ－Ｔｓａｉ方程，引入短纤维平均长度和取向因子ｆｐ考虑尼龙短纤维／氯丁橡胶天然橡胶复合材料中短纤维的长度分布和纤维取向对纵向杨氏模量的影响，提出直接用ｆｐ修正ζ来考虑取向影响的新方法，ζθ（ｆｐ）＝Ｌｄ＾－１（ｆｐ＋１）。结果表明，纵向模量的理论预测值和实验值的相关性较好，对横向模量，用ζ＝２＋Ｋｖｆ（Ｋ为决定于体系的常数）考虑取向的影响，预测也较成功。     

形状记忆合金短纤维增强弹塑性基体复合材料的力学行为

基于Eshelby等效夹杂方法和Mori-Tanaka的平均化理论推导了针对SMA短纤维增强弹塑性基体复合材料的细观力学模型。利用此模型,分析了这种复合材料的力学行为,讨论了材料温度、纤维体积分数和纤维特征形状等参数对复合材料残余应力和残余应变的影响。这对复合材料的分析和设计都有重要的意义。      

Post-curing effect on magnetoelectric performance of single PZT rod/continuous Terfenol-D fiber/epoxy 1-1-3 composites

A magnetoelectric (ME) composite consisting of a single PZT rod embedded in a matrix of continuous Terfenol-D fiber and epoxy medium has been fabricated and characterized. With an optimized aspect ratio of the composite rods, a large ME effect has been observed. The magnetostrictive effect of the continuous Terfenol-D fiber/epoxy medium can be enhanced by imposing an optimal pre-loading stress on the material and this pre-loading stress can be induced by suitable heat treatment. Experimental results show that the ME effect of the single PZT rod/continuous Terfenol-D fiber/epoxy composites can be enhanced significantly by a post-curing process. A thermal stress-mediated continuous fiber composite model has been used to explain the ME enhancement of the post-cured composites.     

Strength improvement in injection-molded jute-fiber-reinforced polylactide green-composites

The mechanical properties of green-composites based on polylactic acid (PLA) with jute fibers were investigated. A long fiber pellet was developed to obtain a high aspect ratio of residual fiber after injection molding. Comparative studies were carried out, where shorter fiber pellets were compounded by different screw configurations using a twin-screw extruder. To interpret the results of our mechanical tests, the fiber geometry, dispersion state, and fiber fracture surfaces after tensile testing were analyzed. We found that the composites made of short fiber pellet (which suffer high compound intensity), exhibited optimal mechanical performance. Although, compounding with a twin-screw extruder decreased the overall aspect ratio of residual fibers, we observed that it significantly facilitated both the dispersion of the jute yarn to jute bundle and the decohesion of jute bundle to elementary fibers. This fiber separation caused by high intensity mixing led to efficient load transfer from matrix to fiber, and improvement of interfacial strength. These findings provide us with an insight into the critical parameters required to develop a high performing jute/PLA composite.