三维编织复合材料圆管轴向冲击压缩破坏细观结构和温度效应

发布时间：2018-04-24 23:27

本文选题：三维编织复合材料圆管 + 轴向冲击压缩　；参考：《东华大学》2017年博士论文

【摘要】：三维编织复合材料因其厚度方向具有更高强度、刚度、断裂韧性、冲击损伤容限,具有抗分层、耐疲劳、净型性和良好的结构整体性等优点,已被广泛应用于航空航天、汽车和船舶等工程领域。本文采用实验和细观结构有限元模拟方法,研究三维编织复合材料圆管在准静态和高应变率轴向压缩条件下破坏机理,探索编织结构参数及低温度场对三维编织复合材料圆管轴向冲击压缩行为的影响。本论文主要研究内容：(1)采用四步法1×1编织技术编织不同结构参数三维圆形管状碳纤维预成型体：试件编织角为25°、35°和45°,编织层数为2层、3层和4层,编织结构为三维四向和五向。(2)常温和低温度场下分别测试不同结构参数三维四向和五向编织复合材料圆管准静态和高应变率下轴向冲击压缩行为。准静态压缩实验中压缩速度为2mm/min,应变率约为0.001/s；高应变率压缩实验中,应变率控制在416/s～936/s；环境温度为-100℃～23℃。提取压缩测试结果,包括应力-应变曲线、压缩强度、压缩刚度、比能量吸收、宏观破坏形态,利用计算机断层扫描成像(CT)测试系统及电子扫描显微镜(SEM)观察材料内部破坏形态。(3)常温下六种不同类型的三维四向和三维五向编织复合材料圆管细观结构有限元分析基于增强体编织物基本结构参数,将三维编织复合材料圆管细观结构几何模型和材料属性相结合,计算复合材料圆管准静态和冲击压缩破坏过程,得到复合材料应力-应变曲线和最终破坏形态。(4)基于常温下建立的三维编织复合材料圆管细观结构几何模型,通过实验和推导确定应变率相关、温度依赖材料模型,进行低温度场冲击加载下复合材料圆管细观结构热力耦合有限元计算。通过增强体和树脂上特殊节点温升-时间曲线、材料冲击压缩变形、渐进破坏过程及材料最终破坏形态应力分布及温分布云纹图来揭示复合材料圆管低温度场下冲击压缩热力耦合破坏过程及机理。通过上述研究发现：(1)常温下不同结构参数三维四向和五向编织复合材料圆管应力-应变曲线均具有应变率敏感性；每种编织复合材料圆管压缩强度、刚度和比能量吸收均随着应变率增加而增大,具有明显应变率依赖性；在准静态和冲击压缩加载下,应力-应变曲线均表现弹塑性特征；编织角和编织层数均明显影响编织复合材料圆管在不同应变率下的压缩性能；三维五向编织复合材料圆管比三维四向编织复合材料圆管具有更高的轴向压缩性能和抗冲击损伤容限；破坏模式可以分为：剪切破坏、纤维抽拔、纤维断裂、树脂开裂、压缩变形、屈曲破坏、粉碎破坏。低温度场下,三维编织复合材料圆管的轴向压缩性质优于常温条件,压缩刚度、强度和比能量吸收对应变率敏感性大于对温度敏感性；低温、高应变率下材料呈现脆性特征,材料压缩破坏形态包括树脂开裂、纤维抽拔和断裂、试样整体屈曲变形、树脂和纤维束界面脱粘等。(2)对比准静态和动态有限元模型计算结果与实验结果,两者具有较好一致性,表明该有限元细观结构模型能够对三维编织复合材料圆管的准静态和冲击压缩基本力学性能进行准确模拟。该有限元细观结构模型可以深入揭示三维编织复合材料圆管冲击压缩失效机理,从冲击压缩过程、应力分布、破坏模式等方面对材料进行动态力学分析。详细研究了应变率、编织角、编织层数和轴纱对三维编织复合材料圆管冲击压缩性能及破坏模式的影响。通过提取细观结构模型分析结果,分别得到三维编织复合材料圆管增强体和树脂在冲击压缩过程中应力分布,再现冲击压缩加载下纤维束和树脂受力变形过程、纤维断裂、树脂基体开裂及两者相互作用状态,分析增强体和基体在冲击压缩过程中承受载荷差异。提取三维五向编织复合材料圆管编织纱、轴纱及树脂上不同位置特殊节点应力-时间曲线,分析应力波在编织纱、轴纱和树脂上传播差异。结果表明,应力波在轴纱上传播速度大于编织纱,树脂上应力波的传播是均匀的,轴纱的应力高于编织纱,而树脂应力远低于所有纱线。这些实验中未测到的中间数据可以进一步揭示三维五向编织复合材料圆管不同于三维四向编织复合材料圆管的冲击压缩破坏机理。(3)低温条件下,由于冲击压缩过程中编织增强结构的压缩变形对树脂有挤压作用,有限元模型计算过程中应力集中最先出现在编织纱线屈曲处并导致树脂非弹性热的产生。由于表面编织纱线取向影响,试件冲击受载面温升云图呈散点状,中部呈“锯齿”状剪切带。编织纱线的温升大于树脂且变化速度快于树脂。上述研究结果对高速加载下抗冲击结构件设计有指导价值,编织复合材料圆管在冲击加载下应变率效应和结构效应明显,通过有效表征细观结构尺度力学性质和动态响应可以对复合材料抗冲击设计提供理论指导。同时低温条件下热力耦合响应及破坏机理研究为该复合材料在航天航空领域应用提供参考。
[Abstract]:Three-dimensional braided composites have been widely used in aerospace, automobile and ship engineering fields because of their higher strength, stiffness, fracture toughness, impact damage tolerance, resistance to stratification, fatigue, net shape and good structural integrity. This paper adopts the finite element simulation method of experimental and mesoscopic structures in this paper. The damage mechanism of three-dimensional braided composite circular tube under the condition of quasi static and high strain rate axial compression is studied. The influence of the weaving structure parameters and low temperature field on the axial impact compression behavior of the three-dimensional braided circular tube is explored. The main contents of this paper are as follows: (1) using the four step method 1 x 1 knitting technology to weave different structural parameters of three dimensional circle Tubular carbon fiber preforms: the braiding angle of the specimen is 25, 35 and 45 degrees, the number of braiding layers is 2, 3 and 4, and the braiding structure is three-dimensional four and five. (2) the axial impact compression behavior under the quasi-static state and high strain rate of three dimensional four and five directional braided composite materials with different structural parameters is tested under the normal temperature and low temperature field. The compression rate is 2mm/min and the strain rate is about 0.001/s, and the strain rate is controlled at 416/s to 936/s in the high strain rate compression test; the ambient temperature is -100 to 23 C. The compression test results are extracted, including the stress strain curve, compression strength, compression stiffness, energy absorption, macro damage form, and computer tomography. (CT) test system and electron scanning microscope (SEM) to observe the internal damage morphology of materials. (3) finite element analysis of six different types of three-dimensional four direction and three-dimensional five directional braided circular tube meso structure finite element analysis based on the basic structural parameters of the reinforced body, the geometric model and material of the circular tube meso structure of the three dimensional braided composite materials Properties are combined to calculate the quasi-static and impact compression failure processes of composite circular tubes, and the stress-strain curves and final failure modes of composite materials are obtained. (4) based on the geometric model of three-dimensional braided circular tube meso structure established at normal temperature, the strain rate correlation, temperature dependent material model and low temperature are carried out by experiment and deduction. The thermomechanical coupling finite element calculation of the microstructure of the composite circular tube under the degree of degree field impact loading is calculated. The compression deformation of material impact compression, the progressive failure process, the final failure mode stress distribution and the temperature distribution cloud pattern are used to reveal the impact compression heat of the composite circular tube under low temperature field. It is found that: (1) the stress strain curves of three dimensional four direction and five direction braided composites with different structural parameters at normal temperature have strain rate sensitivity, and the compressive strength, stiffness and specific energy absorption of each woven composite pipe increase with the increase of strain rate. The stress strain curve shows elastoplastic characteristics under quasi static and impact compression loading, and the braiding angle and the number of weave layers all obviously affect the compression performance of the woven composite circular tube under different strain rates, and the three-dimensional five direction braided circular tube has a higher axial direction than the three-dimensional and four directional braided circular tube. Compression performance and impact damage tolerance; failure modes can be divided into shear failure, fiber pulling, fiber fracture, resin cracking, compression deformation, buckling failure, and crushing failure. Under low temperature field, the axial compression properties of the three-dimensional braided composite pipe are superior to the normal temperature strip, compression stiffness, strength and specific energy absorption correspond to variable rate sensitivity. The properties of the materials are more than the temperature sensitivity, and the material presents brittle characteristics at low temperature and high strain rate. The failure modes of the material include resin cracking, fiber pulling and breaking, the overall buckling deformation of the sample, and the debonding of the resin and fiber bundle interface. (2) the results of the quasi-static and dynamic finite element model calculation are in good agreement with the experimental results. It is shown that the finite element meso structure model can accurately simulate the basic mechanical properties of the quasi static and impact compression of the three-dimensional braided circular tube. The finite element meso structure model can thoroughly reveal the failure mechanism of the impact compression of the three-dimensional braided composite circular tube, from the impact compression process, the stress distribution, the failure mode and so on. The dynamic mechanical analysis of the material is carried out. The effects of strain rate, braiding angle, weave layer number and shaft yarn on the impact compression performance and failure mode of the three-dimensional braided composite circular tube are studied in detail. By extracting the microscopic structure model analysis results, the stress in the impact compression process of the three-dimensional braided composite pipe reinforced body and the resin is obtained. Distribution, the stress and deformation process of fiber bundles and resins under impact compression loading, fiber fracture, resin matrix cracking and the interaction state of the two are analyzed. The load difference between the reinforced body and the matrix in the process of impact compression is analyzed. The stress of three dimensional five direction braided composite circular tube woven yarn, the axial yarn and the special joints on the resin are obtained. The stress wave propagating on the woven yarn, the axial yarn and the resin is analyzed. The results show that the propagation speed of the stress wave on the axis yarn is greater than that of the woven yarn. The propagation of the stress wave on the resin is uniform, the stress of the axial yarn is higher than that of the woven yarn, and the stress of the resin is far lower than that of all yarns. The unmeasured intermediate data in these experiments can be further uncovered. The impact compression failure mechanism of the three-dimensional five direction braided circular tube is different from the three-dimensional four direction braided circular tube. (3) under the low temperature condition, the compressive deformation of the woven reinforced structure during the impact compression process has the extrusion effect on the resin. The stress concentration in the finite element model first appears at the braid yarn flexion. It causes inelastic heat of the resin. Due to the influence of the orientation of the yarn on the surface, the temperature lift of the specimen is scattered in a scattered point and the "sawtooth" shear band in the middle. The temperature rise of the yarn is greater than the resin and the change speed is faster than that of the resin. The strain rate effect and structural effect are obvious under impact loading. By effectively characterizing the mechanical properties and dynamic responses of the meso structure, the composite material can provide theoretical guidance for the impact design of the composite materials. At the same time, the thermal coupling response and failure mechanism under low temperature conditions provide the application of the composite in the aerospace field. Reference resources.

【学位授予单位】：东华大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：TB332

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