参数化单胞计算三维编织预制件纤维体积含量

在Pro/E中建立了三维编织预制件的内部单胞、表面单胞和棱角单胞的3D实体模型,并对模型进行了参数化设计。当编织工艺参数改变时能自动生成新的单胞模型,单胞纤维体积由Pro/E的模型分析功能直接输出。提出了基于参数化单胞计算预制件纤维体积含量的公式。计算了长方体形预制件的纤维体积含量,并与实测值进行比较,理论计算与实验结果吻合良好。计算了扇环形预制件的纤维体积含量,为复杂外形预制件纤维体积含量的计算提供了新方法。     

Microstructure analyses and volume fraction model of 3D 6-directional variable cross-sectional cone-shaped tubular braided fabric

The three-dimensional 6-directional variable cross-sectional cone-shaped tubular braided fabric (6DCTBF) has been applied successfully as the components in aerospace craft. The application of cone-shaped tubular braided fabric requires the densification of a small end to ensure ablation uniformity during composite fabrication. In this paper, in order to meet the size and performance requirements for 6DCTBF, a unique yarn-thinning technique used in the braiding process has developed and explained in detail by first analyzing the fiber bundle movement and distribution in modeling. After the yarn has been thinned, different zones are divided according to the constituting method of the yarn in its unit cell. Geometric models are built for different zones to determine the geometrical dimensions and volume fraction variation range. It has been shown that the theoretical model can accurately describe the 6DCTBF and provide a theoretical basis for the design of its structure and properties.     

体积含量对织物/水泥复合材料弯曲性能的影响

采用无碱玻璃纤维机织物,制备了不同体积含量的织物增强水泥基复合材料,通过三点弯曲抗折强度试验和断裂面形貌数码照片分析,研究了织物体积含量对机织物增强水泥基复合材料弯曲性能的影响。研究结果表明,玻璃纤维机织物体积含量从1%上升到5%时,织物增强水泥复合材料全载荷挠度曲线的形状和弹性模量没有明显变化,经向抗折强度从8.5 MPa上升到17.8 MPa,纬向抗折强度从8.1 MPa上升到17.2 MPa,但增加的幅度与聚合物基单向复合材料纵向强度的混合定律不相符,断裂能从0.53 kJ/m2上升到1.89 kJ/m2,且增加的幅度明显增大。     

Microscopic deformation mechanisms of unidirectional fiber bundles under transverse compressive stresses

The high-performance filament yarns, such as carbon fiber yarn, glass fiber yarn, and Kevlar fiber yarn, have characterized as unidirectional,high parallel filament in fiber bundle. However, due to the difficulties in statistically analyzing the micro-structural characteristics of high-performance fiber bundles comprising of thousands of filaments, Nylon (PA6) filament yarns were chosen as the substitute of high-performance fiber bundles to study the deformation micro-mechanisms of fiber bundles under transverse compressive stresses. In order to evaluate the effects of different compressive stresses on the deformation properties, the synchrotron radiation X-ray micro-computed tomography (micro-CT) was used to obtain cross-section images of the fiber bundle during the compression testing. In particular, the influences of compressive stress on the fiber volume fraction, fiber distribution, fiber contact, and fiber orientation were studied. Results indicate a strong dependence of the microstructure of fiber bundles on the compressive stress.     

Analysis and prediction of elastic constants of co-woven-knitted fabric (CWKF) composite

This paper presents an analytical and numerical model for the prediction of tensile elastic constants of a novel textile structural composite, namely co-woven-knitted fabric (CWKF) composite. Based on the CWKF geometry model previously developed, the direction angles of basic-cells of the weft, warp, and stitch yarn components in a representative volume elementary were determined. The micromechanics method and both isostrain and isostress conditions were applied to the yarn and the pure resin components, and the overall stiffness or compliance matrix of the composite was obtained. The normal elastic constants were calculated and compared with the experimental ones. The results showed that the relative errors between the calculated and the tested values are at an acceptable level (<10%). Thus, the proposed model can be used for the predictions of other elastic constants of the CWKF reinforced composite and effects of structural parameters.     

A study by a genetic algorithm for optimizing the arrangement of the fibers on the damage to the fiber–matrix interface of a composite material

The objective of this work is to optimize the arrangement of the fibers to reduce damage to the fiber matrix interface of a composite material. The results obtained by the genetic algorithm based on the volume fraction of reinforcement show a good agreement between numerical simulation and the actual behavior of both materials T300/914 and PEEK/APC2, however, it would be interesting to see the effect of thermal stress on the optimization of the arrangement by the molecular dynamics method.     

多轴向经编复合材料预制件的几何模型

为更好地了解复杂多轴向经编复合材料预制件的细观结构,在对多轴向经编复合材料预制件结构特征进行研究的基础上,通过合理假设,从细观几何角度出发,建立了带有短切毡的多轴向经编复合材料预制件单元结构模型.利用这个模型推导几何结构特征参数和加工工艺参数之间的关系,得出多轴向经编复合材料预制件理论纤维体积分数公式.以不同规格的多轴...     

芳砜纶纤维成纱毛羽及其主要影响因素

文章介绍了芳砜纶（PSA）纤维的成纱毛羽情况。从纤维本身的特性、纺纱过程对纤维的控制、纺纱过程工艺参数、纤维预处理等几个方面对芳砜纶纤维成纱毛羽的影响因素进行了试验研究和分析。     

An analysis on abrasion resistance of polyester-/viscose-blended needle-punched nonwovens

In this study, the influence of fiber composition and process parameters such as mass per unit area and punching density on abrasion resistance of polyester-/viscose-blended needle-punched nonwovens has been investigated. For this purpose, five different blend ratios of polyester/viscose webs were produced, cross-lapped, and needled in four different mass per unit areas and three different needling/punching densities. The abrasion resistance and thickness of the nonwovens were determined by performing the standard test methods. The structural parameters such as fabric bulk density and fiber volume fraction were calculated and the data obtained from tests and calculations were analyzed in detail. It was concluded that abrasion resistance of the needle-punched nonwovens decreased with the increase of polyester proportion in the mixture and increased with the increase in mass per unit area. Also, an increase in punching density first caused to increase in abrasion resistance and then further increase in punching density decreased the abrasion resistance.     

三维正交机织物织造及复合材料成型工艺研究

详细阐述三维正交机织物的结构特征、织造原理及织造工艺,以三维正交机织物为增强体、环氧树脂为基体,采用真空辅助树脂传递模塑(VARTM)工艺成型,制成复合材料,并分析其内部结构。结果表明:由普通织机改造的多综眼多剑杆织机可以织造三维正交机织物,成型后复合材料内的纱线形状和位置未发生明显变化,树脂较好地渗透到织物内部,复合材料具有较高的纤维体积分数。研究结果为进一步研究三维正交机织复合材料的力学性能及应用奠定了基础。     

A novel structure of woven composite pressure pipes and its multi-scale analysis

A novel structure of woven composite pressure pipes (WCPP) is designed in this paper. Based on the overall geometry structure of woven preform, the representative volume unit (RVU) is established. The effective elastic constants and the mechanical properties of the woven composite layer are predicted by a multi-scale method, and the failure properties are simulated. Compared with filament-wound pressure pipes (FWPP), the WCPP can effectively improve the overall mechanical properties of the composite pressure pipes, and it can promote the further application of composite pressure pipes.     

基于一元二次函数的层联机织预制体细观结构表征

织物预制体结构参数之间的相互关系是高性能复合材料设计需要解决的关键问题.为建立层联机织预制体的细观几何关系,通过显微观察和结构分析提出基于一元二次函数的抛物线凸透镜形纬纱横截面、抛物线形经纱路径等假设,通过研究典型的多层平纹层间联锁结构层联机织预制体,建立预制体全厚度单胞模型,推导其细观结构参数的几何表达,获得纱线横截...     

2.5维机织复合材料的几何结构模型与验证

为验证2.5维机织复合材料结构与其力学性能的关系,基于对材料断面显微照片的观察和分析,假定纤维束截面为为跑道形,建立了2.5维机织复合材料的单元结构模型。借助模型推导出纱线在几种典型结构（浅交弯联、浅交直联、深角联）的单元体结构内的纱线长度、接结经的取向角和纤维体积分数,并对材料进行拉伸、压缩性能预测。制作了满足要求的2.5维机织复合材料实验件并对其进行力学性能测试,通过试验值和预测值的对比,验证几何模型的正确性。     

A novel structure design of braided composite pressure vessel and its mechanical analysis

A novel structure of braided composite pressure vessel (BCPV) is designed in this paper. Based on the overall geometry structure of braided preform, the representative volume unit (RVU) model is established. The effective elastic constants and the mechanical properties of the composite layer of BCPV are predicted, and compared with filament-wound pressure vessel (FWPV). Numerical results show that BCPV can effectively improve the overall mechanical properties of the composite pressure vessel, and has a wide application prospect.