界面层对三维机织角联锁SiCf/SiC复合材料断裂韧性的影响

为探究界面层对SiC_f/SiC复合材料性能的影响,选用国产第3代SiC纤维,通过先驱体浸渍裂解工艺制备了热解碳(PyC)、热解碳/碳化硅(PyC/SiC)、氮化硼(BN)、氮化硼/碳化硅(BN/SiC)4种界面层的三维机织角联锁SiC_f/SiC复合材料。在此基础上,结合声发射技术对复合材料进行常温断裂韧性测试,并利用扫描电镜对其细观损伤模式进行评价。结果表明：界面层对三维机织角联锁SiC_f/SiC复合材料的断裂强度和断裂韧性有强决定作用,但对其初始模量没有太大的影响;以PyC层为主界面层的试样具有良好的断裂韧性,试样P-SiC_f/SiC和P/S-SiC_f/SiC的断裂韧性分别为13.99和16.93 MPa·m^1/2,而试样B-SiC_f/SiC表现出强界面结合,具有最低断裂韧性6.47 MPa·m^1/2;但在界面引入SiC层后,试样B/S-SiC_f/SiC的断裂韧性显著提高至15.81 MP...     

三维六向编织SiCf/SiC复合材料的力学行为及其损伤机制

为解决陶瓷基复合材料在服役过程中因拉伸和弯曲导致的失效问题,以三维六向编织SiC_f/SiC复合材料为研究对象,分析了受力过程中复合材料力学行为与纤维及结构的联系机制。采用微计算机断层扫描技术获得材料结构及孔隙的三维图像,对复合材料纵向和横向进行拉伸、弯曲性能测试,并阐明其损伤机制。结果表明:复合材料呈现明显的各向异性特性,纵向拉伸强度和弯曲强度分别是横向的10.37、5.06倍;复合材料不同方向受力的损伤模式不同,拉伸载荷下纵向试样裂纹沿着六向纱呈Z字形扩展,而横向试样裂纹沿着编织轴向扩展,最终导致拉伸破坏;弯曲载荷下裂纹沿着厚度方向扩展,并最终导致纵向及横向试样的韧性断裂,且纵向韧性优于横向。     

2.5D角联锁芳纶机织复合材料的压缩性能研究

探讨2.5D角联锁芳纶机织复合材料的压缩性能。测试了4种结构的2.5D角联锁芳纶机织复合材料的经向压缩强度和压缩模量及纬向压缩强度和压缩模量,分析了其结构与压缩性能间的关系。试验结果表明:伸直状态的衬经纱对2.5D角联锁芳纶机织复合材料的经向压缩性能有较大贡献;伸直状态的衬纬纱对2.5D角联锁芳纶机织复合材料的纬向压缩性能有较大贡献。认为应根据实际应用环境所需要的压缩强度和压缩模量来设计2.5D角联锁芳纶机织复合材料的结构。     

2．5D芳纶机织复合材料弯曲性能测试

为了分析复合材料预制件结构和弯曲性能的关系,丰富2．5D复合材料的力学性能数据库,为2．5D复合材料的设计者提供参考;采用三点弯曲试验方法对4种结构的2．5D芳纶机织复合材料进行了经向和纬向弯曲性能测试;测试结果表明：带衬经结构复合材料经向的弯曲性能优于不带衬经结构复合材料,带衬纬结构复合材料纬向的弯曲性能高于不带衬纬结构复合材料;该测试的结论为：伸直状态的衬经纱对经向的弯曲性能具有大的贡献,伸直状态的衬纬纱对纬向的弯曲性能具有大的贡献。     

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。     

空口角连锁织物组织结构探讨

简述了三维机织复合材料的发展,以角连锁复合材料预成型件作为研究目标。介绍了几种不同组织结构的角连锁织物,分析了角连锁织物的空口最大值与空口非最大值的形成过程,设计了几种空口角连锁机织物的经向结构剖面图。利用假设的方法把纬角连锁结构中的空口视为纬纱,重新构造成了相对应的实口纬角连锁组织,并对其经纬纱组织循环数之间的关系进行研究推理,得出了一个共用于实口与空口的通式。     

捆绑组织对三维正交机织复合材料拉伸性能的影响

以高强涤纶纱为原料,借助自主改造的二维小样机织造三种捆绑组织(平纹、斜纹和缎纹)的三维正交机织物,再采用真空辅助树脂传递模型工艺制作三维正交机织复合材料。重点研究三种不同的捆绑组织对三维正交机织复合材料拉伸性能的影响。结果表明:三维正交机织复合材料沿经向拉伸时断裂表面较平整,沿纬向拉伸时断裂处形状不规则;捆绑组织为缎纹的三维正交机织复合材料的拉伸性能整体最好,捆绑组织为平纹的三维正交机织复合材料拉伸性能整体最差;三种捆绑组织的三维正交机织复合材料纬向拉伸断裂强度大于经向拉伸断裂强度。     

2.5D芳纶机织复合材料的拉伸性能研究

2.5D机织复合材料凭借其特有的优点和相对成熟的技术受到各领域的关注。然而,这种材料现有的力学性能数据较少,且集中在耐高温和耐烧蚀材料上,影响了其可靠性的评估。对4种结构的2.5D芳纶机织复合材料进行经向和纬向拉伸性能研究,分析结构和拉伸性能的关系。试验结果表明:伸直状态的衬经纱对经向拉伸性能具有较大的贡献;伸直状态的衬纬纱对纬向拉伸性能具有较大的贡献;纬密增加会增大接结经纱的弯曲程度,从而降低经向拉伸性能。     

三维夹芯复合材料冲击损伤后弯曲性能研究

采用手糊成型工艺将环氧树脂与三维机织夹芯织物及玻纤平纹织物复合,制成三维夹芯复合材料,并采用不同的冲击高度对其进行低速冲击试验。利用Instron 5969H型万能材料试验机对经过低速冲击试验的三维夹芯复合材料的弯曲性能进行测试,分析冲击高度对三维夹芯复合材料弯曲性能的影响。结果表明:同种三维夹芯复合材料的弯曲性能与冲击高度呈负相关;相同冲击高度下,同种三维夹芯复合材料的经向剩余弯曲强度明显低于其纬向剩余弯曲强度。     

三维正交机织复合材料拉伸性能研究

阐述了三维正交机织复合材料沿不同方向的拉伸力学性能。复合材料以三维正交机织玻璃纤维织物为增强体,以环氧树脂为基体,基于真空辅助树脂传递模塑(VARTM)工艺成型并制备试样。测试了试样的拉伸性能,结果表明:该三维正交机织复合材料90°(纬向)的拉伸性能优于0°(经向),但断口处存在严重的纤维抽拔和界面脱粘现象;增强体结构中经纱和纬纱含量对拉伸性能影响较大,面内某一纱线含量高,则该方向拉伸性能就强。同时,Z纱有效地改善了普通层合板复合材料拉伸分层失效的缺陷,但玻璃纤维与树脂基体界面结合性能较差。     

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。     

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.     

开孔三维机织复合材料的拉伸性能

为研究开孔尺寸对三维机织复合材料拉伸力学行为、破坏模式以及失效机制的影响规律,设计了3种不同孔径的三维机织复合材料试样,利用非接触全场应变测试系统和显微图像技术进行表征。结果表明:6、10、14 mm 的孔径对三维机织复合材料的拉伸模量几乎没有影响,开孔后全截面拉伸强度分别下降35.6％、44.5％和51.8％,但开孔后的净截面拉伸强度基本相同,与未开孔试样相比,平均拉伸强度下降约22.4％;未开孔试样的全场应变呈现均匀分布,而开孔试样在孔左右两侧呈现出应变集中;开孔试样的断口形貌相似,主要表现为经纱的断裂,并伴随有部分纱线的抽拔以及层间开裂。     

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.     

三维机织多孔复合材料的横向冲击性能

为了解纺织结构复合材料的动态力学行为,更好地设计并应用纺织结构复合材料,对三维多重纬经角联锁织物复合材料的动、静态力学性能进行了测试。运用分离式Hopkinson压杆装置测试了不同速度（应变率）及准静态状态时材料的力学性能。结果表明：三维多重纬经角联锁织物复合材料是应变率敏感材料;随着冲击速度的不断提高,材料所能承受的载荷及吸收的能量增大;材料破坏时前面表现为压缩破坏形式,背面为拉伸破坏形式。     

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.