复合材料层合板疲劳累积损伤数值模拟
发布时间：2019-01-28 20:43
【摘要】：疲劳失效是工程中常见的一种破坏形式。多数金属材料的疲劳极限是拉伸强度的40%~50%,而碳纤维/环氧树脂复合材料则可达90%,虽然复合材料的抗疲劳性能比金属好,但是也避免不了疲劳问题。在分析复合材料层合板疲劳分层问题时也不能再用研究金属材料疲劳裂纹扩展的方法。在复合材料层合板使用过程中,层间分层和界面脱粘是其中两种常见的和起决定性作用的失效形式。由于分层常常发生在低应力水平下的周期载荷,因此机械疲劳是引起复合材料结构分层损伤的最重要因素。由于复合材料层合板往往具有非线性,经典断裂力学已经无法满足。同时复合材料由于其铺层方式的多样性,层合板厚度的影响,因此若是通过实验方法来研究复合材料层合板疲劳分层扩展将会是一个耗时费力的事情。随着计算机技术的发展,因此寻求有效的数值模拟技术,对复合材料层合板疲劳分层进行分析具有极大的工程意义。本文将断裂力学和损伤力学相结合,利用数值模拟技术对复合材料层合板疲劳分层进行分析,同时对复合材料层合板疲劳寿命进行预报。首先介绍了单调载荷下和疲劳周期载荷下离散内聚力模型本构关系。在单调载荷下,视内聚力模型关系为双线性关系。通过弹簧单元,建立了单调载荷下的静态损伤演化形式。同时针对高周疲劳下,建立了指数形式的疲劳累积损伤演化模型。分析了在商业有限元软件ABABQUS中的数值运用,利用子程序进行实现复合材料层合板的疲劳累积损伤模型,为后面分析复合材料层合板疲劳扩展奠定理论基础。其次针对单调载荷下利用离散内聚力模型,分析了复合材料层合板I、II和复合型断裂分层扩展情况。得到三种形式下的复合材料层合板分层演化过程,并和VCCT技术进行比较,验证了离散内聚力模型的有效性。同时就内聚力模型参数弹簧单元模量和网格大小对离散内聚力模型运用影响进行分析,得到离散内聚力模型对这两个参数的敏感性很小的结论。然后分析在高周疲劳载荷下复合材料层合板疲劳分层扩展情况。利用疲劳离散内聚力模型对I型、II型和复合型裂纹扩展情况。得到三种形式下载荷加载初期时裂纹扩展速率。同时分析在四种载荷大小工况下的疲劳裂纹扩展速率和能量释放率之间的关系,并与文献中实验数据吻合良好。最后建立了用虚拟裂纹闭合技术来预测复合材料疲劳寿命方法,对I型和II型复合材料层合板寿命进行预测分析。
[Abstract]:Fatigue failure is a common failure form in engineering. The fatigue limit of most metal materials is 40% of the tensile strength, while the carbon fiber / epoxy composite can reach 90%. Although the fatigue resistance of the composite is better than that of the metal, the fatigue problem can not be avoided. In the analysis of fatigue delamination of composite laminates, the method of fatigue crack propagation of metal materials can no longer be used. Interlaminar delamination and interfacial debonding are two common and decisive failure forms in composite laminates. Because delamination often occurs under periodic loads at low stress levels, mechanical fatigue is the most important factor causing delamination damage of composite structures. Because composite laminates are often nonlinear, the classical fracture mechanics can not be satisfied. At the same time, due to the diversity of the laminates and the influence of the thickness of the laminates, it would be time consuming to study the fatigue delamination propagation of the composite laminates by the experimental method. With the development of computer technology, it is of great engineering significance to seek effective numerical simulation technology and to analyze the fatigue delamination of composite laminates. In this paper, the fracture mechanics and damage mechanics are combined, and the fatigue delamination of composite laminates is analyzed by numerical simulation technique, and the fatigue life of composite laminated plates is predicted at the same time. The constitutive relation of discrete cohesive force model under monotone load and fatigue cyclic load is first introduced. Under monotone load, the cohesion model is regarded as a bilinear relation. The static damage evolution form under monotone load is established by spring element. At the same time, an exponential fatigue cumulative damage evolution model is established for high cycle fatigue. The numerical application in the commercial finite element software ABABQUS is analyzed. The fatigue cumulative damage model of composite laminates is realized by subroutine, which lays a theoretical foundation for the later analysis of fatigue propagation of composite laminated plates. Secondly, based on the discrete cohesive force model under monotone load, the delamination and propagation of composite laminated plates I _ (II) and composite mode fracture are analyzed. The delamination evolution process of composite laminates in three forms is obtained, and compared with VCCT technique, the validity of the discrete cohesive force model is verified. At the same time, the influence of spring element modulus and mesh size on the application of discrete cohesive force model is analyzed, and the conclusion that the sensitivity of discrete cohesive force model to these two parameters is very small is obtained. Then the fatigue delamination propagation of composite laminates under high cycle fatigue loading is analyzed. The fatigue discrete cohesive force model is used to investigate the crack propagation in mode I, II and composite mode. The crack growth rate at the initial loading stage is obtained in three forms. At the same time, the relationship between the fatigue crack growth rate and the energy release rate under four load conditions is analyzed, and it is in good agreement with the experimental data in the literature. Finally, a virtual crack closure method is established to predict the fatigue life of composite materials, and the life of type I and II composite laminates is predicted and analyzed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33
本文编号：2417301
[Abstract]:Fatigue failure is a common failure form in engineering. The fatigue limit of most metal materials is 40% of the tensile strength, while the carbon fiber / epoxy composite can reach 90%. Although the fatigue resistance of the composite is better than that of the metal, the fatigue problem can not be avoided. In the analysis of fatigue delamination of composite laminates, the method of fatigue crack propagation of metal materials can no longer be used. Interlaminar delamination and interfacial debonding are two common and decisive failure forms in composite laminates. Because delamination often occurs under periodic loads at low stress levels, mechanical fatigue is the most important factor causing delamination damage of composite structures. Because composite laminates are often nonlinear, the classical fracture mechanics can not be satisfied. At the same time, due to the diversity of the laminates and the influence of the thickness of the laminates, it would be time consuming to study the fatigue delamination propagation of the composite laminates by the experimental method. With the development of computer technology, it is of great engineering significance to seek effective numerical simulation technology and to analyze the fatigue delamination of composite laminates. In this paper, the fracture mechanics and damage mechanics are combined, and the fatigue delamination of composite laminates is analyzed by numerical simulation technique, and the fatigue life of composite laminated plates is predicted at the same time. The constitutive relation of discrete cohesive force model under monotone load and fatigue cyclic load is first introduced. Under monotone load, the cohesion model is regarded as a bilinear relation. The static damage evolution form under monotone load is established by spring element. At the same time, an exponential fatigue cumulative damage evolution model is established for high cycle fatigue. The numerical application in the commercial finite element software ABABQUS is analyzed. The fatigue cumulative damage model of composite laminates is realized by subroutine, which lays a theoretical foundation for the later analysis of fatigue propagation of composite laminated plates. Secondly, based on the discrete cohesive force model under monotone load, the delamination and propagation of composite laminated plates I _ (II) and composite mode fracture are analyzed. The delamination evolution process of composite laminates in three forms is obtained, and compared with VCCT technique, the validity of the discrete cohesive force model is verified. At the same time, the influence of spring element modulus and mesh size on the application of discrete cohesive force model is analyzed, and the conclusion that the sensitivity of discrete cohesive force model to these two parameters is very small is obtained. Then the fatigue delamination propagation of composite laminates under high cycle fatigue loading is analyzed. The fatigue discrete cohesive force model is used to investigate the crack propagation in mode I, II and composite mode. The crack growth rate at the initial loading stage is obtained in three forms. At the same time, the relationship between the fatigue crack growth rate and the energy release rate under four load conditions is analyzed, and it is in good agreement with the experimental data in the literature. Finally, a virtual crack closure method is established to predict the fatigue life of composite materials, and the life of type I and II composite laminates is predicted and analyzed.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB33
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