双轴向经编针织复合材料压缩性质应变率效应和失效机理

发布时间：2018-06-25 06:07

本文选题：BWK复合材料 + 有限元分析　；参考：《东华大学》2015年硕士论文

【摘要】：双轴向经编针织物(biaxial warp-knitted,简写为BWK)在经编地组织衬入伸直纱线，经编组织使衬入纱线形成稳定结构，沿纱线方向具有高拉伸刚度和强度。双轴向经编针织物可作为增强体用于风力发电、航空航天等领域。本课题以压缩试验为基础，建立细观结构简化模型，利用有限元方法研究双轴向经编针织复合材料压缩性能，分析破坏机理。论文主要工作有： (1) BWK复合材料冲击压缩试验：采用MTS-810材料测试系统和分离式霍普金森压杆完成BWK复合材料不同应变率范围内的冲击压缩试验，获取应力-应变曲线、破坏形态特征。试验结果表明：BWK复合材料对应变率敏感，最大应力和压缩刚度随应变率增大而增大，失效应变随应变率增大而减小；BWK复合材料厚度方向失效模式为剪切破坏，面内方向准静态时失效模式为剪切破坏，高应变率时材料主要是分层破坏。 (2) BWK复合材料细观结构模型的简化：经编纱的力学性质融进树脂内，简化为“等效树脂”。依据BWK的结构特点，确定等效树脂最小代表体积单元(RVE)，将RVE分割成一系列纤维体积含量相同的“亚单胞”，计算局部坐标系下“亚单胞”刚度矩阵，并转换成全局坐标系下“亚单胞”刚度矩阵，，根据体积平均思想计算得到等效树脂的刚度矩阵，简化后BWK复合材料只包含等效树脂与经纬纱。在有限元软件ABAQUS中创建BWK复合材料细观结构简化模型。 (3)有限元计算结果分析：在商用有限元软件ABAQUS中模拟BWK复合材料准静态压缩和高应变率冲击压缩破坏过程。模拟结果与试验结果吻合较好，证明本文所建有限元细观结构简化模型在预测压缩性能方面有效。通过观察应力波在经纬纱和树脂中的传播，揭示复合材料破坏机理：BWK复合材料面外压缩失效模式为剪切破坏，产生两条与压缩轴成45°夹角的剪切带，切断与剪切带不在一个平面上的纤维束，树脂也沿着剪切带开裂。复合材料被分割成三部分发生滑移，导致较大塑性变形。面内方向上失效模式主要是分层破坏。应力由受压面向另一端面传递，纤维束间树脂首先发生碎裂，层间发生分离。主要由纤维束承受压缩载荷，纤维束发生屈曲变形使复合材料产生分层。
[Abstract]:The biaxial warp knitted fabric (biaxial warp-knitted, BWK) is lined with straight yarns in the warp knitted structure, the warp knitting organization makes the lining into the yarn to form a stable structure, and has a high tensile stiffness and strength along the yarn direction. The dual axis warp knitted fabric can be used as an augmented body for wind power generation, aerospace and other fields. This subject is based on compression test. Based on the foundation, a simplified microstructure model is established. The compressive properties of the biaxial warp knitted composites are studied by using the finite element method, and the failure mechanism is analyzed.
The main work of the paper is as follows:
(1) the impact compression test of BWK composite material: using MTS-810 material test system and separated Hopkinson pressure bar to complete the impact compression test within the range of different strain rate of BWK composite, and obtain the stress strain curve and destroy the shape characteristics. The test results show that the BWK composite material is sensitive to the variation rate, the maximum stress and the compression stiffness follow. The strain rate increases and the failure strain decreases with the increase of strain rate; the failure mode of the thickness direction of BWK composite is shear failure. When the direction of the surface is quasi static, the failure mode is shear failure, and the material is mainly stratified failure when the high strain rate is high.
(2) simplification of the meso structure model of BWK composite: the mechanical properties of warp knitting yarn are incorporated into the resin and simplified as "equivalent resin". According to the structural characteristics of BWK, the minimum representative volume unit (RVE) of the equivalent resin is determined, and RVE is divided into a series of "subcells" with the same volume content of the fiber, and the "sub cell" in the local coordinate system is calculated. The degree matrix is converted into the "subcellular" stiffness matrix in the global coordinate system, and the stiffness matrix of the equivalent resin is obtained by the volume averaging method. The simplified BWK composite only contains the equivalent resin and the warp and weft yarn. The meso microstructure simplification model of the BWK composite is created in the finite element software ABAQUS.
(3) analysis of the results of finite element calculation: Simulation of BWK composite quasi-static compression and high strain rate impact compression failure process in the commercial finite element software ABAQUS. The simulation results are in good agreement with the experimental results. It is proved that the simplified model of the finite element structure in this paper is effective in predicting the compression performance. The propagation of the yarn and resin reveals the failure mechanism of the composite material: the failure mode of the BWK composite is shear failure, which produces two shear bands with the angle of 45 degrees with the compression axis, cutting off the fiber bundles that are not on the one plane, and cracking the resin along the shear zone. The composite material is divided into three parts to slip and lead to the slip. The failure mode in the direction of the surface is mainly stratified failure. The stress is transferred from the compression to the other end, the resin is first cracked and the interlayer separates. The fiber bundle is mainly subjected to the compression load, and the fiber bundle flexed to make the composite layered.
【学位授予单位】：东华大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB332

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