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A Representative Volume Cell (RVC) chosen to epitomize the entire three dimensional four-directional braided composites is
investigated to evaluate the mechanical behavior of the material by computational micromechanics. In addition to including
several damage modes of braid yarn and matrix within the braided composites, the numerical model also takes into account interface
damage mode by using a Cohesive Zone Model (CZM). A parametrical study is conducted to evaluate the influence of interface
properties on the macro stress-strain curve and the interaction of different failure modes of the braided composites under
uniaxial tensile loading. The interface damage evolution of the braided composites with large braid angle is also provided
further. Preliminary results indicate that the interface damage, which is one of the key factors to cause the nonlinearity
of the stress-strain relationship, can decrease the elastic modulus but not obviously control the ultimate strength of the
braided composites with large braid angle. 相似文献
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针对不同编织角度的三维四向编织碳纤维/环氧树脂复合材料,进行了热环境下的轴向拉伸和压缩力学性能实验研究,讨论了温度对三维四向编织复合材料的轴向拉伸和压缩力学性能的影响,并根据宏观断裂形貌和SEM图像分析了材料的破坏和断裂机制。结果表明,随着测试温度的升高,三维四向编织碳纤维/环氧树脂复合材料的纵向拉伸强度有小幅提高,而纵向压缩强度显著降低。在室温条件下,编织角对材料的纵向拉伸破坏特征没有影响,而对材料的纵向压缩破坏特征有较大影响。随着测试温度的升高,不同编织角度复合材料的纵向拉伸和压缩的损伤破坏形态均与室温条件下明显不同。 相似文献
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The effect of yarn distortion on the mechanical properties of 3D four-directional braided composites
A representative volume cell (RVC) is chosen to analyze the mechanical properties of 3D (3 dimensions) four-directional braided composites. Owing to braid yarns (an assembly of fibers) squeezing against each other in the braided composites, the braid yarns are distorted. Based on geometrical characteristics of the braided composites, cross-section of each braid yarn is supposed to be an octagon and divided into seven regions in the RVC. The distortion characteristics of yarns are considered in each region. Elastic properties of each region obtained by stochastic function theory are introduced into finite element model to calculate the mechanical properties of the RVC. The influences of yarn distortion on the stiffness and strength of the braided composites are obtained and discussed. 相似文献
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利用分离式霍普金森压杆(SHPB)装置对三维四向编织碳纤维增强树脂基复合材料的动态压缩性能进行了研究。通过对编织角为20°、30°和45°的试验件分别进行沿纵向、横向和厚度方向的动态压缩试验,得到材料在800~2 000/s应变率范围内的应力-应变曲线,并与准静态压缩试验结果进行对比,研究了应变率、压缩方向及编织角对材料极限强度和弹性模量的影响。结合高速摄影记录的动态压缩过程,进一步分析了不同情况下材料的破坏模式与破坏过程。结果表明:应变率越高,材料的极限强度和弹性模量越大,材料在受压的三个方向上均具有一定的应变率强化效应,且高应变率下表现出比准静态压缩时更明显的脆性;编织角的改变对材料在三个方向上的动态压缩性能均有影响,其中对纵向的影响最为明显;不同方向受压时材料的失效形式不同,且准静态和高应变率下的失效形式也有区别。 相似文献
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为了准确预测三维四向编织复合材料的纵向拉伸力学性能,对编织复合材料的面胞和内胞细观实体模型进行参数化建模,面胞模型考虑了纱线空间轨迹的偏移和横截面的挤压变形。用体素网格离散模型并施加合适的边界条件,将各组分材料的损伤模型编入到有限元分析软件ABAQUS用户定义材料子程序UMAT中。分别对内编织角为30°和45°的三维四向碳纤维/环氧树脂编织复合材料的面-内胞模型进行数值分析,经体积加权平均获得不同厚度编织复合材料试件的纵向拉伸模量和强度,通过统计具有相同破坏模式的积分点数量研究复合材料的渐进损伤过程。结果表明:基于面-内胞模型预测三维四向编织复合材料的纵向拉伸力学性能与试验值吻合良好,损伤分析结果合理地反映了面胞和内胞的渐进损伤过程。 相似文献
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基于二维编织C/SiC复合材料的细观结构,建立了碳纤维丝/热解碳界面/SiC基体和纤维束/表层SiC基体两种尺度下的细观单胞模型,通过有限元方法计算碳纤维丝/热解碳界面/SiC基体模型的等效弹性常数和强度,然后代入纤维束/表层SiC基体模型中计算,并引入Tsai-Wu失效准则,考虑不同失效模式的损伤,建立了二维编织C/SiC复合材料的渐进损伤模型,模拟了其偏轴拉伸应力-应变行为。针对该模型,阐述了二维编织C/SiC复合材料单胞模型在复杂应力状态下其纤维束的损伤过程。数值模拟结果与实验数据吻合较好,验证了模型的有效性,为该种材料的力学性能分析提供了一种有效方法。 相似文献
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针对不同编织角、 不同纤维体积分数的三维五向炭纤维/酚醛编织复合材料在不同温度下进行了纵向(编织方向)压缩和横向压缩试验 , 获得了其主要压缩力学性能 , 分析了编织参数、 温度对材料压缩力学性能的影响。对试件断口进行了宏观及扫描电镜观察 , 从宏、 细观角度研究了材料的变形及其破坏机制。结果表明 , 三维五向炭纤维/酚醛编织复合材料的压缩应力2应变曲线呈现明显的非线性特征 , 且温度效应明显; 编织角和纤维体积分数是影响材料压缩性能的主要参数。三维五向炭纤维/酚醛编织复合材料的纵向压缩与横向压缩具有完全不同的破坏机制。 相似文献
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通过实验研究了三向编织玻璃/环氧复合材料的刚度性能 , 并考虑编织角和试件宽度参数的影响 , 探讨了拉伸和压缩刚度性能的差异。实验结果表明 : 在同一纤维体积分数条件下 , 随着编织角的增大 , 试件的纵向弹性模量有所减小 , 泊松比 (在编织角约大于 35° 时) 也有所减小 ; 宽度为两倍和三倍单胞宽度的试件的刚度性能基本相同; 试件的纵向弹性模量和泊松比远大于横向弹性模量和泊松比; 拉伸和压缩时试件的弹性模量和泊松比基本接近 ; 在横向拉伸和压缩时试件的应力2应变曲线具有明显的非线性特征。实验结果为编织复合材料结构设计提供了数据参考。 相似文献
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The focus of this paper is on the manufacture of textile composite beams and on the determination of their mechanical properties.
This includes investigating the effects of fibre orientation on the mechanical properties of braided and woven textile composites.
Composites were manufactured from nominally identical constituents and identical consolidation processes, leaving as the only
variables, variations caused by the different fibre architecture of the preform. The repeatability and, hence, reliability
of this approach is demonstrated. Results obtained show that fibre architecture affects composite strength and extensibility.
Composites with woven preforms are practically linear up to catastrophic failure while composites with braided preforms exhibit
non-linearity prior to failure. Also the mechanical properties of the textile composite beams were determined. Results show
that by tailoring the braid angle and pick density of braided and woven composite performs, the mechanical properties of the
composite beams can be controlled to suit end-use requirement. 相似文献
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通过宏观压缩实验,研究了三维四向编织复合材料的抗压力学性能;同时,为了认识其压缩失效机理,对压缩试件的破坏断口进行了扫描电镜分析。实验结果表明:纵向压缩模量比横向压缩模量大得多;影响纵向压缩力学性能的主要参数是材料的编织角,随编织角的变化,复合材料的纵向压缩破坏机理发生了变化,编织角较小时,材料表现为脆性特征;当编织角大于某个角度,材料的应力-应变曲线趋于非线性,延性增加,更多地表现为塑性破坏特征。此外,横向压缩的破坏机理与纵向压缩明显不同。 相似文献
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三维五向编织复合材料纵向性能的实验研究 总被引:9,自引:2,他引:9
通过对具有不同编织结构参数的三维五向编织复合材料试件的纵向拉伸和压缩实验,分析了该类材料的纵向拉、压刚度和强度随编织工艺参数的变化规律以及材料的失效形式.三维五向编织复合材料在破坏前基本保持线弹性,纵向拉、压破坏具有脆性特征,拉伸模量和压缩模量比较接近,但拉伸强度远大于压缩强度.编织角和纤维体积含量对材料性能的影响显著,纱线粗细的影响不大.提高第五向纱线的比例,可提高材料的纵向性能.此外,研究中采用短标距薄板试件,以避免试件产生整体屈曲和端部纤维束开裂破坏. 相似文献
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基于三维六向编织复合材料的细观结构,假设第六向纱线的截面形状为菱形,建立了三维六向编织复合材料的渐进损伤有限元模型。采用Linde等提出的失效准则,引入周期性位移边界条件,对三维六向编织复合材料的纵向拉伸应力-应变行为进行了渐进损伤数值模拟,讨论了单胞模型在纵向拉伸载荷作用下的细观损伤起始、扩展和最终失效的演化过程,并预测了材料的拉伸强度。在此基础上,进一步研究了编织角、纤维体积分数和编织纱水平取向角等参数对材料纵向拉伸力学性能的影响规律。研究结果表明,三维六向编织复合材料的轴向纱线拉伸断裂是导致其破坏的最主要因素。所得数值结果与现有试验值吻合较好,验证了该模型的有效性,为更深入研究此类材料的力学性能奠定了基础。 相似文献
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Braided textile composites under compressive loads: Modeling the response, strength and degradation 总被引:1,自引:0,他引:1
Shunjun Song Anthony M. Waas Khaled W. Shahwan Xinran Xiao Omar Faruque 《Composites Science and Technology》2007,67(15-16):3059-3070
This paper discusses the results of a finite element (FE) based micromechanics study of the compressive damage development mechanisms of 2D triaxial braided carbon fiber composites (2DTBC). The micromechanics based study was carried out on a Representative Unit Cell (RUC) size 3D FE model. The uniaxial compressive response was established using an arc-length method in conjunction with the ABAQUS commercial FE code. In this work, explicit account of the braid microstructure (geometry and packing) and the measured inelastic properties of the matrix (the in situ properties) are accounted for via the use of the FE method. This enables accounting for the different length scales that are present in a 2DTBC. This detail is necessary for developing a mechanism based damage prediction capability. The computational model provides a means to assess the compressive strength of 2DTBC and its dependence on various microstructural parameters. In particular, the dependence of compressive strength on the axial fiber tow properties and axial tow geometrical imperfections is discussed and shown to be significant in capturing the mechanism of damage development. 相似文献
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