Fabrication, Mechanical and Dielectric Characterization of 3D Orthogonal Woven Basalt Reinforced Thermoplastic Polyimide Composites

The 3D orthogonal woven basalt fiber reinforced polyimide (PI) composites were fabricated and characterized in this study. The PI film was firstly prepared to determine PI processing parameters. Fourier transform infrared (FTIR) analysis showed that 300°C was the suitable imidization temperature. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) results showed relatively good thermal properties of the PI film. In the fabrication of composites, the multi-step impregnation method was applied. The bending properties of 3 mm-thick composite showed increasing trend in all and the second-time impregnated composite had much higher value than the first-time impregnated composite. Moreover, the bending fracture mode photos showed obvious creases except for the first-time impregnated materials, which agreed well with the bending property values. The dielectric constants for the composites were complex because they had not regular value following the mixing rule of the composites, which was mainly due to the interfacial polarization and other effects in the fabrication processing.

Effect of Weft Binding Structure on Compression Properties of Three-Dimensional Woven Spacer Fabrics and Composites

With the wide use of three-dimensional woven spacer composites(3DWSCs),the market expects greater mechanical properties from this material.By changing the weft fastening method of the traditional I-shape pile yarns,we designed three-dimensional woven spacer fabrics(3DWSFs)and 3DWSCs with the weft V-shape to improve the compression performance of traditional 3DWSFs.The effects of weft binding structures,V-pile densities,and V-shaped angle were investigated in this paper.It is found that the compression resistance of 3DWSFs with the weft V-shape is improved compared to that with the weft I-shape,the fabric height recovery rate is as high as 95.7%,and the average elastic recovery rate is 59.39%.When the interlayer pile yarn density is the same,the weft V-shaped and weft I-shaped 3DWSCs have similar flatwise pressure and edgewise pressure performance.The compression properties of the composite improve as the density of the V-pile yarns increases.The flatwise compression load decreases as the V-shaped angle decreases.When the V-shaped angle is 28°and 42°,the latitudinal V-shaped 3DWSCs perform exceptionally well in terms of anti-compression cushioning.The V-shaped weft binding method offers a novel approach to structural design of 3DWSCs.

Property of three-dimensional silica composites

Silica fibers-reinforced, fused silica composites were fabricated with repeated vacuum-assisted liquid-phase infiltration. The mechanical properties, thermal properties, and ablative properties of the samples were evaluated. The effect of the silica fiber content and treatment temperature on the flexural strength of the three-dimensional SiO2 （3-D SiO2） composites also was investigated. The SiO2 composites show good mechanical properties and excellent ablative performance. The flexural strength increases with an increase in silica fiber content, and decreases with an increase in treatment temperature. When the volume fraction of the silica fiber is 50vo1% and the treatment temperature is 700℃ the flexural strength of the composites reaches a maximum value of 78 MPa. By adding cyclohexanone surfactant, the infiltration property can be largely improved, resulting in the density of SiO2 composites increasing up to 1.65 g/cm^3. The fracture surfaces of the flexural specimens observed using SEM, show that the pseudoplasticity and the toughening mechanisms of the composites are caused by absorption of a lot of energy by interface debonding and fiber pulling out.

3D Woven Structures and Their Weave Design with Changing Cross-section on Warp and Weft Direction

With 3D orthogonal and pseudo-orthogonal weaves, woven sructures with lengthwise and widthwise changing cross section on one side or both sides of the structure can be constructed. The weave formation and the looming draft creation are discussed in this paper which can be used as references to manufacture woven preforms with changing cross sections.

Analysis of Apparent Elasticity Constants of Woven Fabrics

The woven fabric can be defined as orthogonal elastomer if the extension force that puts on the fabric is very small. Based on the precondition, the apparent elasticity constants of a woven fabric were analyzed theoretically in the paper. The bias angle (which is between weft yarns and extension direction ) affects apparent elasticity modulus and elasticity coefficient of the fabric in the extension direction. And the experiment describes fluxes of elasticity constants going with the bias angle of the fabric.

Structural effects of three-dimensional angle-interlock woven composite undergoing bending cyclic loading

This paper reports the structural effects of three-dimensional(3-D)angle-interlock woven composite(3DAWC)undergoing three-point bending cyclic loading from experimental and finite element analysis(FEA)approaches.In experiment,the fatigue tests were conducted to measure the bending deflection and to observe the damage morphologies.By the FEA approach,a micro-structural unit-cell model of the 3DAWC was established at the yarn level to simulate the fatigue damage.The stress degradation at the loading condition of constant deformation amplitude was calculated to show the degradation of mechanical properties.In addition,the stress distribution,fatigue damage evolution and critical damage regions were also obtained to qualitatively reveal the structural effects and damage mechanisms of the 3DAWC subjected to three-point bending cyclic loading.

电加热机织物的发热性能及发热均匀性探讨

以发热功率密度和温度均匀系数为指标,基于正交试验方案,探讨以不锈钢纤维纱为电加热元件的电加热机织物制备工艺。并基于九宫格取点法,优化温度均匀系数测试方法。研究发现:本研究中,温度测点取81点是可信的均匀度评价方案。电加热机织物的纬纱排列规律为1根不锈钢纤维纱+3根黏胶纱、纬纱密度为10.5根/cm、组织结构为经二重1/7时,织物具有较为优异的发热性能,发热功率密度为857.23 W/m^(2);电加热机织物的纬纱排列规律为1根不锈钢纤维纱+5根黏胶纱、纬纱密度为6.5根/cm、组织结构为经二重1/3时,电加热机织物具有较为优异的发热均匀性。

三维正交整体夹芯机织物的结构设计及织造

以正交结构为基本的三维结构单元,通过改变空心各边的长度和厚度,设计了多种经向截面为六边形的三维整体夹芯机织物结构,并在改造的普通织机上织造成功。在此基础上对试样的结构特点进行对比分析,同时探讨了三维正交夹芯机织物孔形尺寸的影响因素,比较了各种三维整体夹芯机织物试样的结构特点及织造方法。该研究为三维整体夹芯机织物的结构设计提供了参考,设计的多种三维夹芯机织物为蜂窝结构复合材料提供了性能良好的增强体。

三维正交机织复合材料的力学性能研究

利用材料试验机装置开展了三维正交机织Kevlar/乙烯基树脂复合材料力学实验,实验表明面内经向拉伸和厚度z方向压缩时,材料具有一定的应变率效应,厚度z方向压缩强度远大于面内压缩强度,而面内经向和纬向的拉伸强度则相当。结合纤维的编织方式,对这些现象做了必要的定性分析。最后,本文基于三维正交机织复合材料的结构特点,推导了一组可用于估算三维正交机织复合材料弹性模量的公式,估算结果和实验值接近。

碳-玻纤维混杂正交三向复合材料力学性能研究

为了使混杂纤维三维机织复合材料在航空航天领域能得到更好的发展,对碳-玻混杂正交三向复合材料X向力学性能进行了数值模拟与实验研究。通过了解增强织物各项结构参数并在多种理论假设的基础上确定了材料细观结构。选取具有对称性的单胞结构,建立了有限元模型并对其进行了X向拉压工况的数值模拟,采用渐进损伤的方法预测了材料X向力学性能。使用树脂传递模塑工艺制作成型碳-玻混杂正交三向复合材料实验件,对其进行X向力学性能测试。将实验数据与理论值对比分析,验证了数值模拟方法的准确性。通过与纯玻纤正交三向复合材料力学性能的对比,讨论了碳-玻混杂材料的优势与缺陷。研究结果对该材料的实际应用提供了重要的参考依据。

接结经纱对三维正交机织物结构的影响

以经纱接结的三维正交机织物为研究对象 ,在 3种接结纱张力下制织了 2种接结纱浮长的 6种正交机织物。通过比较织物的接结纱织缩率、纬纱密度和织物厚度 ,发现适当的接结纱张力既有利于形成较为理想结构的正交织物 ,又有利于织造的顺利进行 ;较小的接结纱浮长 ,有利于织物结构的均匀。

三维正交机织复合材料单胞特征单元及其应用

基于三维正交机织复合材料,提出了一种特征单元均匀化分析方法。用“特征单元”来表示能够反映单胞的几何构造细节和材料构造细节的单元。首先用一般有限元方法对三维正交机织复合材料单胞进行分析得到总体刚度矩阵,利用该矩阵的特征向量建立了单胞的特征单元。通过比较特征单元的刚度矩阵元素和利用传统均匀化方法得到的刚度矩阵元素,说明了特征单元能够反应单胞的几何构造和材料构造细节。为了验证特征单元的有效性,分别用特征单元、传统均匀化方法和一般有限元方法计算了三维正交机织复合材料梁的固有频率,结果表明特征单元精度比传统均匀化方法高,而计算量比一般有限元方法大幅度降低。

三维正交机织复合材料弹道侵彻数值模拟

利用LS-Dyna有限元软件开展球形弹弹道侵彻Kevlar/乙烯基树脂三维正交机织复合材料的模拟研究,靶板采用含损伤的正交各向异性本构模型和Hashin失效准则,子弹剩余速度的计算值和实验值符合较好,破坏形貌和实验基本一致,并给出侵彻速度时程曲线;结合x方向纤维和面内基体的损伤演化图,分析弹道侵彻过程和材料的破坏模式.

三维正交机织复合材料厚向压缩性能试验研究

采用方柱形试样对UHMWPE/乙烯基酯三维正交机织复合材料进行了压缩试验。研究了该类材料的厚向压缩强度和压缩模量与z向增强纤维细度的关系,并讨论了材料的压缩破坏失效模式。结果表明:z向增强纤维细度的增加导致材料厚向压缩性能的下降。降低z向增强纤维束的细度,有利于提高材料厚向抗压性能。三维正交机织复合材料的压缩破坏具有塑性特征。三维正交机织复合材料主要的破坏模式是z向纤维在试样表面的应力集中、纤维束的剥离和剪切破坏。

三维正交机织复合材料弹道冲击实验及破坏模式

本文用钢芯弹对三维机织复合材料作弹道冲击测试。得到了弹体的入射速度和剩余速度,比较了常见几种材料的弹道性能评价参数的差异,并考察侵彻破坏模式和靶体最后的损伤破坏形态。在300-800m/s冲击速度范围下观测了材料的冲击破坏形态,发现机织复合材料受弹面和子弹出射面破坏形态不一样,受弹面主要是以纤维的压缩、剪切破坏以及基体开裂为主,出射面以纤维的拉伸、厚度方向的纱线断裂为主要破坏模式。通过对破坏模式和形态的分析,可以帮助建立更加准确的破坏准则,从而在设计抗弹材料时起到一定的作用。

三维正交机织玄武岩/芳纶混编复合材料的拉伸和剪切性能研究

本文设计和制作了两种混杂模式的三维正交机织玄武岩/芳纶混编复合材料,分别是层间混杂和层内混杂模式。对其拉伸性能和剪切性能进行了测试和分析,结果表明,层内混杂复合材料的拉伸性能和剪切性能比层间混杂复合材料的好,层内混杂复合材料的归一化强度和归一化模量分别比层间混杂复合材料的高22.12%和16.9%,层内混杂复合材料的剪切强度和剪切模量分别比层间混杂复合材料的高19.61%和26.03%;对于层间混杂复合材料,纬向的归一化强度比经向的高4.06%,但厚度方向上纱线的存在和织造工艺中经纱预加张力的影响,使纬向的归一化模量比经向的降低11.44%。

三维正交机织复合材料的力学性能

测试了5种不同规格型号的三维正交机织复合材料以及同种型号增强体与两种不同树脂基体得到的复合材料的抗拉伸、抗弯曲力学性能,并分析了其破坏模式。结果表明:三维机织复合材料能有效阻止分层破坏,且纬向的力学性能明显好于径向,其力学性能也会随树脂基体力学性能的提高而有所提高,模量的变化尤其明显。

非正交二维平纹编织树脂基复合材料的弹性性能

二维编织布在铺设形状复杂的复合材料结构时,如果边缘受到拉剪,经纬纱之间的夹角会发生变化;在固化过程中,原本正交的经纬纱走向也可能发生偏转。经纬纱之间夹角的变化会增加材料的各向异性,进而影响结构的力学性能。本文通过试验研究了纤维束偏转对二维编织复合材料弹性性能的影响,分别进行了三种典型试验件面内拉伸弹性模量的测试。基于刚度体平均方法,提出了一种非正交二维编织树脂基复合材料的刚度预测模型,并在此基础上分析了纤维束偏转对材料有效性能的影响规律。计算结果与试验数据符合良好。

二维与三维机织复合材料的力学性能实验研究

通过对超厚三维正交机织复合材料及二维机织层合板分别进行拉伸和压缩实验,研究比较两复合材料刚度和强度特性的差异;研究发现无论是三维机织材料的拉、压,还是二维层合板的拉、压的应力—应变曲线都可近似为直线关系,而且具有脆性破坏的特点;三维复合材料的拉、压强度要高于二维层合板,是由于不同的增强相结构及纤维含量造成;不同的破坏模式对材料强度影响很大。

三维正交机织复合材料弹道侵彻有限元模拟

测试复合材料弹道侵彻性质,得到复合材料弹道侵彻过程中子弹的入射速度和剩余速度及冲击破坏形态。基于复合材料的真实细观结构,建立细观结构模型,运用商用有限元软件ABAQUS/Explicit计算复合材料弹道侵彻破坏过程。研究发现三维正交复合材料不同破坏机制:三维正交机织复合材料不产生冲击分层,纤维断裂和基体开裂是主要吸能模式,复合材料冲击破坏是最主要的破坏模式。