三维机织角联锁SiCf/SiC复合材料弯曲性能及损伤机制

为解决陶瓷基复合材料在服役环境中由于弯曲而导致失效的问题,从理论上分析了经向和纬向弯曲过程中复合材料弯曲受力与内部纤维之间的相互作用机制。以SiC_f/SiC复合材料为例,利用微计算机断层扫描技术获得其内部纤维结构和孔隙等三维图像;并在此基础上,分别对三维机织角联锁SiC_f/SiC复合材料经向和纬向进行弯曲性能测试,从细观、微观尺度分析弯曲损伤机制。结果表明:三维机织角联锁SiC_f/SiC复合材料的纬向和经向性能明显不同,且纬向试样的弯曲强度大于经向试样;SiC_f/SiC复合材料的弯曲损伤模式复杂,经向试样裂纹主要沿着经纱与纬纱接触点扩展,而纬向试样裂纹主要在纬纱束之间产生,并最终导致弯曲破坏。     

Mechanical properties improvement of silane addition epoxy/3D orthogonal woven composite material

In this study, the influence of silane addition on mechanical properties of epoxy/3D orthogonal glass fiber woven composite was studied. The KH560 silane modification composite specimen reinforced with 3D orthogonal woven fabric/epoxy was manufactured by means of Resin Infusion under Flexible Tooling. The mechanical properties of the epoxy/3D glass fiber woven composites were characterized by tensile and bending tests. The tensile and bending properties of silane-modified 3D orthogonal woven glass composite in warp and weft directions were compared with the pristine or epoxy/glass composite material not coupled using silane. The results show that the tensile and bending properties in warp and weft directions have been improved due to the silane addition. The bonding strength between the fiber and matrix was improved and the delamination and debonding between fiber and matrix was retarded and shifted to cohesive failure of the matrix due to the silane modification. Electron microscopy of the fracture and failure modes of the test specimens were used to support the results and conclusions.     

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。     

Warp and weft directional tensile properties of multistitched biaxial woven E-glass/polyester composites

The objective of this research work was to understand the warp and weft directional tensile properties of the two-dimensional multistitched multilayer E-glass/polyester woven composites. The warp and weft directional specific tensile strength and modulus of unstitched structure were higher than those of multistitched structures as stitching caused minor warp and weft yarn filament breakages. Contrarily, the specific tensile strains of unstitched structure were slightly lower than those of all multistitched structures. The stitching yarn type, the number of stitching directions, and the stitching density generally influenced the warp and weft directional tensile properties of multistitched E-glass/polyester woven composites. The failure of warp and weft directional multistitched woven E-glass/polyester composite structures was matrix breakages, and partial and complete yarn breakages in their surfaces. They had a local delamination in their cross-sections and the delamination did not propagate to the large areas due to multidirectional stitching. Also, the failure was confined at a narrow area and resulted in the catastrophic fiber breakages. The warp and weft directional specific damaged areas of multistitched structures, in particular four-directional stitching, were significantly lower than those of the unstitched structures. This indicated that the multistitching made the structures better damage-tolerance materials.     

玄武岩纤维机织针织复合织物增强复合材料的弯曲性能

根据新型的机织针织复合织物的结构特点,分别选用不同线密度的高强高模玄武岩纤维作为经纱、纬纱和针织纱编织这种织物,以其作为增强体,采用VARTM工艺制作了玄武岩纤维/乙烯复合材料。为提供该新型织物增强复合材料的应用依据,测试了复合材料的横向、纵向和斜向弯曲性能,并对各个方向的弯曲载荷-挠度特征曲线及其弯曲断裂形态进行了分析。研究结果表明：这种复合材料具有较好的轴向弯曲性能,横向和纵向的弯曲性能均优于斜向,其弯曲断裂都表现一定的塑性,弯曲能量基本相近。     

不同结构厚截面三维机织碳纤维复合材料的弯曲性能对比

为准确分析不同结构厚截面复合材料不同方向上的弯曲性能差异,通过设计织造三向正交、浅交直联、浅交弯联3种典型机织结构的厚截面碳纤维三维机织物,并采用真空辅助树脂成型工艺制备了近似纤维体积含量的碳纤维复合材料板,对其进行了XYZ方向的弯曲实验。结果表明:三向正交结构由于内部纤维束近似平直,碳纤维束自身性能得到最大利用,对应复合材料经向弯曲强度最好;浅交直联结构复合材料的Z经和Z纬弯曲强度累加值最大,其厚度截面上的综合弯曲性能最好,且其他各方向的弯曲强度较为均衡;浅交弯联结构内部纱线交织摩擦损伤严重,且经纱屈曲程度最大,对应复合材料经纬向弯曲性能均为最差。     

三维正交机织复合材料的冲后压缩性能

为揭示纱线张力对三维机织复合材料抗冲击及冲后压缩性能的影响规律,基于多剑杆织造工艺,配置不同接结纱张力(25、50、100 cN)织造三维正交机织物,通过真空辅助树脂传递模塑成型工艺制备复合材料,并在室温下进行低速冲击及冲后压缩性能测试。结果表明：当接结纱张力为100 cN时,试样在冲击载荷下发生表层树脂大面积破裂和剥离并使纬纱失去支撑,同时,试样表层纬纱发生较大卷曲,促使压缩载荷发生屈曲失效;接结纱张力为100 cN试样的压缩性能相比接结纱张力为25 cN试样下降约50%;接结纱张力较高时易导致纬纱卷曲增大和树脂富集,并由此降低试样的弯曲刚度和冲后压缩性能。     

玄武岩纤维机织针织复合结构增强复合材料的拉伸性能

根据新型机织针织复合织物的结构特点,分别选用不同线密度的高强高模玄武岩纤维作为经纱、纬纱和针织纱编织织物,以其作为增强体,采用VARTM工艺制作玄武岩纤维/乙烯复合材料.为提供这种新型织物增强复合材料的应用依据,测试了复合材料的横向、纵向和斜向拉伸性能,并对各个方向的拉伸应力与应变特征曲线及其拉伸断裂形态进行分析,对比...     

锯齿形三维机织间隔复合材料的弯曲性能

为解决层合间隔复合材料易开裂和整体性差的问题,采用绿色环保的玄武岩低捻长丝作为经、纬纱,合理设计经向截面图和组织图,并在普通织机上织造3种不同间隔高度的锯齿形三维机织间隔织物。以所织得的锯齿形三维机织间隔织物作为增强材料,环氧乙烯基树脂作为基体,利用真空辅助成型工艺,制备锯齿形三维机织间隔复合材料,同时对三维机织间隔复合材料进行三点弯曲性能测试,得到弯曲载荷-位移曲线、能量吸收图和破坏模式。结果表明:复合材料的纬向是主要承力方向;组织循环个数越多的材料表现出更好的弯曲性能;在一定间隔高度范围内,间隔高度越高的锯齿形三维机织间隔织物承受的弯曲载荷和吸收的能量也越高;锯齿形三维机织间隔复合材料的破坏模式是材料上表层受压,下表层受拉,而连接层受压;在作用力下材料只是出现明显的变形,但并未出现材料整体的破坏。     

广角机织物的织造工艺及其偏轴拉伸力学性能

为开发适用于不同应用领域的产业用纺织品,在对原有普通剑杆织机改进的基础上,探讨了广角机织物的织造工艺,织造了经纱和纬纱夹角为120°的涤/棉平纹广角机织物。借助万能材料试验机研究了普通涤/棉正交织物和广角机织物不同偏轴方向的拉伸力学性能,获得了其应力-应变曲线和特征值变化规律,并分析了其变形及失效模式。结果表明:对于普通正交机织物和广角机织物,其拉伸断裂强力均呈现出明显的极轴特性;在断裂强力相同的情况下,与普通正交机织物相比,广角机织物纬向的断裂伸长率提高了30%,经、纬向弹性模量分别提高了42%和79%,展现出优异的强度和变形特征。     

机织物组织自动识别技术

为实现机织物组织的自动识别,对织物表面反射图像进行纠偏和直方图均衡预处理,并按图像的经纬向灰度投影曲线实现织物组织点的定位。根据经纬向组织点灰度的相关性,求出织物组织的经纬纱循环数。通过比较组织循环范围内组织点的灰度均值来确定组织点的属性,并以组织点的灰度方差对组织点的属性进行验证。实现单循环组织识别后,再对多个组织循环内的对应组织点进行验证,以进一步提高识别的准确性。织物的测试结果表明,所提出的算法能够实现简单的机织物组织的准确识别,并能输出对应的织物组织图。     

石墨烯黏胶纤维机织物的功能改性研究

制备同规格的普通黏胶纤维机织物、石墨烯黏胶纤维机织物及不同不锈钢丝质量分数的石墨烯黏胶纤维/不锈钢丝机织物,对比它们的导电、防电磁辐射、防紫外线、抗静电、力学(拉伸、弯曲、耐磨)及透气等性能。结果表明:普通黏胶纤维经石墨烯改进后,所制成的石墨烯黏胶纤维机织物的导电、防电磁辐射、防紫外线、抗静电、力学(拉伸、弯曲、耐磨)等性能都有所改善,其中防紫外线与耐磨性能提高显著,透气性能下降明显;石墨烯黏胶纤维/不锈钢丝机织物的导电、防电磁辐射、防紫外线和抗静电、经向拉伸断裂强力、纬向抗弯刚度、透气性能都优于石墨烯黏胶纤维机织物,纬向拉伸断裂强力、经纬向拉伸断裂伸长率、经向抗弯刚度及耐磨性能不及石墨烯黏胶纤维机织物;随着不锈钢丝质量分数在7.0%~20.0%范围内的增加,石墨烯黏胶纤维/不锈钢丝机织物的导电、防紫外线、抗静电、经向拉伸断裂强力、纬向抗弯刚度及透气性能增强,纬向拉伸断裂强力、经纬向拉伸断裂伸长率、经向抗弯刚度、耐磨性能减小,不锈钢丝质量分数变化对防电磁辐射性能影响较小。当不锈钢丝质量分数为7.0%时,石墨烯黏胶纤维/不锈钢丝机织物的综合性能最佳。     

Interactive effect between warp and weft of a woven ramie fabric under biaxial loadings

The occurrence of an interactive effect between warp and weft of woven fabrics under practical working conditions is an important concern for researchers. A novel 3D loading device has therefore been developed to elucidate information on materials subjected to loadings in multiple dimensions. This paper investigated the interactive effects between warp and weft in biaxial tension. Strain fields were characterized by digital speckle correlation method and Poisson’s ratio was calculated at 0° in the warp direction. The effects of different cutting angles and loading threshold values at 0° on the interactive effect were also evaluated. An interactive effect between warp and weft existed, and the influence of load at weft to warp was larger than warp to weft. Weft produced larger strain fields in both directions. As the load in the warp direction linearly increased, force values nonlinearly increased while load ratio decreased. Poisson’s ratio, however, was practically unchanged. Loading mean value curves at x and y axes had sine curve characteristics. The greatest interactive effect occurred when the warp load was 65.3% of the biaxial breaking strength.     

Finite element analyses of stress distributions of three-dimensional angle-interlock woven composite subjected to three-point bending cyclic loading

This paper presents the finite element simulation of stress distribution features of 3D layer-to-layer angle-interlock woven composite undergoing three-point bending cyclic loading. With the finite element analysis model, a microstructure shell element model of the woven composite at yarn level was established to calculate the fatigue behaviors and stress distribution during cyclic loading. The stress distributions in the warp, weft yarns, and the resin regions have been calculated to show the stress difference in the woven composite. It has been observed that the warp yarns share the most part of the stress or loading, i.e. the strength warp yarn is more important than that of the weft yarn for the fatigue design. In addition, the stress distributions at the locations where the weft yarns crossover the warp yarns have been investigated. The stress degradations of the top and bottom surface of the woven composite panels were also compared with those in experimental and good agreement was found. With the stress distribution in the woven composite, the method of improving the fatigue damage tolerance was expected to be developed.     

玻璃纤维多轴向经编复合材料的制备及拉伸性能研究

以环氧树脂为基体,分别以玻璃纤维多轴向经编针织物和玻璃纤维机织物作为增强材料,通过手糊法制备复合材料,并通过试验对比研究两种复合材料的拉伸性能。结果表明,经编复合材料沿各个轴向的拉伸强度比复合前多轴向经编针织物及机织复合材料的强度均有明显提高,增幅均在50%以上,说明多轴向经编复合材料具有更优异的力学性能。这为进一步扩大玻璃纤维多轴向经编复合材料的应用领域提供了有力证据。     

飞轮缠绕用圆环织物的设计

为提高复合材料飞轮的径向强度,设计了径向也存在纱线的圆环形织物,它是按照飞轮层状展开得到的形状,经纱沿圆环的圆周方向,纬纱沿半径方向。分析圆环形织物在织造过程中经纬纱间的剪切变形,从织口到织物被织机的卷取成形辊握持,剪切变形角逐渐增大。剪切变形的存在,使机上圆环形织物的大小半径比设计值要小,而经纱密度变大。推导出织物机上尺寸与设计尺寸之间的关系,并可用于圆环织物的设计。实际制织了一种碳纤维圆环形织物,下机后经相反方向的剪切变形,得到了与设计相一致的结构。     

组织结构对UHMWPE短纤纱织物防刺性能的影响

UHMWPE短纤纱具有优秀的抗切割性与较好的树脂浸润性,非常适用于制作防刺材料。文章试织了12种不同织物规格的试样,进行准静态穿刺实验,探究5种因素(组织、紧度、纱线线密度、经纬密和面密度)对织物防刺性能的影响,并比较不同穿刺角度下织物防刺性能的差异。结果表明:与方平织物与接结双层织物相比,平纹织物的防刺性能最好;同种经纬密或同紧度下,粗特纱织制的平纹织物防刺性能好;随着经密增加,紧度增加,面密度增加,防刺性能逐渐增加,但织物过于紧密时,防刺性能反而降低;平纹织物的穿刺性能具有各向异性,经纬向的防刺性能优于45°方向。     

三维横编间隔织物的编织工艺及其性能

为开发适合不同应用领域的曲面复合材料,采用新型三维曲面间隔结构,在电脑横机上用芳纶纱编织了带有双层罗纹连接中间层的横编间隔织物,探讨了编织步骤和编织工艺。在此基础上通过在间隔织物纬向的2个表层衬入芳纶增强纱,改进了织物的力学性能。通过调整编织程序,开发出不同曲率的间隔织物。在英斯特朗电子万能材料试验机上测试有增强纱和无增强纱织物的横、纵向拉伸性能,比较分析这2种织物的应力应变曲线。结果表明,在其他条件相同时,有增强纱的三维横编间隔织物横向、纵向拉伸应力增加明显,变形较少,织物尺寸稳定。     

亚麻机织物增强热塑性复合材料的性能

利用聚丙烯纤维对亚麻纱线进行包缠,使用该纱线织造3种经纱密度相同,纬纱密度不同的平纹织物。利用热压机将5层织物复合,分别制成3种复合材料板材。对板材的拉伸性能进行测试和分析。测试结果表明:织物中纱线的密度对层合板的强力和断裂伸长率有重要影响;在条件一定的情况下,随着织物纬纱密度的减小,材料沿经向的拉伸强度呈上升的趋势,而经向断裂伸长率呈下降趋势。     

二维与三维机织复合材料力学性能的实验研究

对超厚三维正交机织复合材料及二维要织层合板人别进行了拉伸和压缩实验,研究比较了两种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应力应变曲线都近似为直线,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.这主要是由于材料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.