2.5D类缎纹织物增强复合材料疲劳特性研究

发布时间：2019-03-08 20:51

【摘要】：三维织物增强复合材料具有良好的层间力学性能、抗剪切性能、结构稳定性和可设计性。常见的三维织物结构有正交三向结构、2.5D平纹结构、及其衬经、衬纬、和衬法向结构,这些结构大量运用在各类复合材料中。与2.5D平纹结构相比,2.5D类缎纹结构织物中浮长线较长,交织点较少,使2.5D类缎纹织物具有良好的变形能力,更适宜用于弯曲、扭转等曲面结构复合材料增强体,典型应用如叶片和天线罩等。为了保证2.5D类缎纹织物增强复合材料在疲劳环境下的使用安全,研究其拉伸特性和拉-拉疲劳性能是十分有必要的。根据2.5D类缎纹织物组织结构特点,设计织物开口工艺和一种开口辅助工装,在三维织机上实现织物的连续织造。对织物进行复合,得到2.5D类缎纹织物复合材料,简称FC(Fabric Composite),剖切试件研究复合材料内部结构,以经纬纱真实状态建立细观模型,并计算2.5D类缎纹织物几何参数。同时,制备缎纹铺层复合材料,简称LC(Laminates Composite),进行对比研究。基于DIC全场应变系统,测试了 FC和LC试件面内经向拉伸应力-应变关系,研究两种结构对复合材料拉伸性能的影响。并开展FC和LC试件拉-拉疲劳性能,从细观层次分析了两种复合材料在高周疲劳下强度、模量和疲劳损伤扩展模式。经向拉伸试验中,FC比LC试件经向拉伸强度小5%,拉伸模量高9%,断裂伸长率高5%,差值小主要原因为两种试件面内结构和纤维体积含量近似;但泊松比FC比LC试件大93%,主要因为2.5D类缎纹织物纬向变形能力较强。拉-拉疲劳试验中,FC试件在70%疲劳应力水平下就到达100万次疲劳循环,而LC试件满足100万次疲劳循环的应力水平为52.5%,说明FC试件抗疲劳能力强于LC试件。FC和LC试件拉-拉疲劳具有三个发展阶段,FC试件三个阶段正则化模量下降趋势和塑性变形增长趋势明显弱于LC试件,表明FC抗疲劳性能优于LC试件。疲劳后FC试件强度损失31.2%、拉伸模量下降22.6%、断裂伸长率下降27.8%、泊松比下降2.5%;LC试件强度损失51.7%、拉伸模量下降4.2%、断裂伸长率下降50.9%、泊松比上装123%;各项性能变化均与疲劳对试件损伤程度有关。观测比疲劳断口和疲劳后无损检测,发现,FC试件在经纬纱交织处和纬向具有明显损伤,并沿经纬交织方向和纬向发展,LC试件层间具有明显损伤,在层间沿受力方向扩散。对比两组拉-拉疲劳试验结果,表明,2.5D类缎纹织物复合材料抗疲劳性能优于缎纹织物铺层复合材料试件。课题以复合材料实际应用需求为背景,研究了 2.5D类锻纹织物作为用于高周疲劳复合材料增强体的可行性,为其应用提供了试验数据和设计依据。
[Abstract]:Three-dimensional fabric reinforced composites have good interlaminar mechanical properties, shear resistance, structural stability and design. The common three-dimensional fabric structure has orthogonal three-way structure, 2.5D plain grain structure, and its lining warp, lining weft, and lining normal structure. These structures are widely used in all kinds of composite materials. Compared with 2.5D plain fabric, 2.5D satin fabric has longer floating length and fewer interweaving points, so 2.5D satin fabric has good deformation ability and is more suitable for curved and torsional composite reinforcement. Typical applications such as blades and radome. In order to ensure the safety of 2.5D satin fabric reinforced composites in fatigue environment, it is necessary to study the tensile properties and tensile-tensile fatigue properties of 2.5D satin fabric reinforced composites. According to the structure characteristics of 2.5D satin fabric, the fabric opening technology and an opening assistant tool are designed to realize the continuous weaving of fabric on three-dimensional loom. The composite material of 2.5D satin fabric was obtained by compounding the fabric. The internal structure of the composite was studied by FC (Fabric Composite), cutting specimen. A mesoscopic model was established based on the true state of theodolite and weft yarn, and the geometric parameters of 2.5D satin fabric were calculated. At the same time, the preparation of satin laminate composite, abbreviated as LC (Laminates Composite), was compared. Based on the DIC full-field strain system, the in-plane tensile stress-strain relationship between FC and LC specimens was measured, and the effects of the two structures on the tensile properties of the composites were studied. The tensile-tensile fatigue properties of FC and LC specimens were studied. The strength, modulus and fatigue damage propagation modes of the two composites under high cycle fatigue were analyzed at a mesoscopic level. In the tensile test, the tensile strength, modulus and elongation at break of FC are 5% less, 9% and 5% higher than those of LC, respectively. The main reason for the small difference is that the in-plane structure and fiber volume content of the two specimens are similar. However, Poisson is 93% larger than FC than LC, mainly because 2.5D satin fabric has strong zonal deformation ability. In tension-tension fatigue test, FC samples reach 1 million fatigue cycles at 70% fatigue stress level, while LC specimens reach 52.5% stress level of 1 million fatigue cycles. The results show that the fatigue resistance of FC specimens is stronger than that of LC specimens. FC and LC specimens have three stages of development, and the decreasing trend of regularization modulus and the increasing trend of plastic deformation in three stages of FC specimens are obviously weaker than those of LC specimens. The results show that the fatigue resistance of FC is better than that of LC. After fatigue, the strength loss of FC specimen was 31.2%, tensile modulus decreased 22.6%, elongation at break decreased 27.8%, Poisson's ratio decreased 2.5%. The strength loss of LC specimens was 51.7%, tensile modulus decreased 4.2%, elongation at break decreased 50.9%, Poisson's ratio was 123%. Compared with fatigue fracture and after fatigue, it is found that FC specimen has obvious damage at warp and weft interweave and weft direction, and develops along longitude and weft direction. LC specimen has obvious damage between layers and diffuses along the direction of force between layers. The results of two groups of tensile-tensile fatigue tests show that the fatigue resistance of 2.5D satin fabric composite is better than that of satin fabric laminated composite specimen. Based on the practical application requirements of composite materials, the feasibility of 2.5D forged fabric as reinforcement for high cycle fatigue composites is studied in this paper. The experimental data and design basis are provided for its application.
【学位授予单位】：天津工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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