基于失效机理的复合材料层合板强度分析方法

发布时间：2018-05-05 11:59

本文选题：复合材料层合板 + 层间断裂　；参考：《西北工业大学》2015年博士论文

【摘要】：当前复合材料在航空航天等工程结构中的使用率正处于快速增长阶段。与各向同性材料相比,复合材料具有构造复杂和损伤形式多样等特点,其失效模式之间相互作用,互为诱因。这种材料构成和损伤组合的复杂特性给复合材料的强度分析带来很大挑战。深入理解复合材料失效破坏机理,建立反映客观物理现象的强度分析方法对复合材料结构设计和使用维护十分必要,有助于降低结构试验测试成本,缩短研制周期,提高结构使用效率和安全性。本文以工程应用最为广泛的纤维增强复合材料层合板为研究对象,在层合板层间界面断裂、面内破坏强度理论和非线性本构关系等方面开展研究工作。论文首先研究了层合板层间断裂分析问题。针对层间界面断裂模拟时计算效率低、计算成本高等问题,提出一种适合与板壳单元配合使用,且能够考虑板壳平动和转动自由度以及板壳厚度的新型组合界面单元,并建立相应的三维板壳分层模型。推导了新型组合界面单元的有限元列式,给出双线性形式下单一型和混合型分层的本构关系,推导出组合界面单元的切线刚度矩阵,并在ABAQUS隐式用户自定义单元子程序UEL中予以实现。将组合界面单元用于模拟单一型和混合型分层问题。通过双悬臂梁(DCB)试验的模拟,重点考察了数值模拟中几种参数的选取及其对计算结果的影响。对末端缺口三点弯曲试验(3ENF)、混合模式弯曲试验(MMB)和单搭接胶接接头试验进行了数值模拟,并推导了解析计算公式,计算结果与有关文献中的试验结果及解析计算结果相吻合,表明组合界面单元能很好的模拟单一型和混合型分层损伤的起始和演化。其次研究了层合板的面内强度分析问题。建立了完整的基于复合材料层合板失效机制的强度理论。首先论述了复合材料就地效应及其重要性,推导了一种基于断裂力学假设的层合板就地强度计算方法。以有关文献中纤维压缩破坏机理的试验观察为基础,提出一种改进的纤维压缩失效预测模型,在保持LaRC系列强度理论中kink model基本特征的前提下对其进行改进,并增加一个强度准则来描述剪切驱动型纤维压缩破坏模式,使改进模型具有更好的适应性。针对树脂基体在横向压缩和面内剪切加载下的非线性力学行为,提出一种利用等效应变来考虑二者之间非线性叠加耦合效应的方法,并由此得到非线性本构关系。利用建立的强度理论和失效模式预测方法,对多种单向板和层合板在简单和复杂应力状态下的失效包线和应力应变曲线进行了理论预测,并讨论了关键参数选取的影响。结果表明,本文提出的强度理论全方位表现出较好的预测精度和适应性,能反映真实的试验现象和趋势。采用连续介质损伤力学(CDM)思想,建立一种基于失效机理的非线性损伤本构关系。结合层合板连续壳模型的特点,根据强度理论预测的不同失效模式特征提出对应的损伤退化方法,并针对许多细节问题给出详细的因应对策,在商业有限元软件ABAQUS的显式用户材料子程序VUMAT中予以程序实现。为了验证方法的可靠性,首先通过一个受载立方体的模拟进行了网格敏感性测试分析,然后通过模拟单向板偏轴压缩试验来验证非线性本构关系的合理性,再通过模拟文献中多种层合板的开孔压缩、开孔拉伸和增高型紧凑拉伸试验来表现方法的分析精度,分析各自的失效破坏过程和特征。数值模拟结果表明,本文方法具有较好的预测精度,能反映结构的真实力学行为和破坏形态。
[Abstract]:Compared with isotropic materials, composite materials have the characteristics of complex structure and various types of damage compared with isotropic materials, and their failure modes interact and cause mutual inducement. The complex properties of this material and damage combination give the strength of the composite material. The analysis brings great challenges. It is necessary to understand the failure mechanism of composite materials and to establish the strength analysis method to reflect the objective physical phenomena, which is very necessary for the design and maintenance of composite materials. It is helpful to reduce the cost of test and test, shorten the development cycle and improve the efficiency and safety of the structure. A wide range of fiber reinforced composite laminates are used as the research object, the interlaminar interface fracture, the theory of in-plane failure strength and the nonlinear constitutive relation are carried out. Firstly, the problem of interlaminar fracture analysis is studied. The problem of low calculation efficiency and high calculation cost is proposed for interlaminar interface fracture simulation. A new type of composite interface unit suitable to the plate and shell elements which can be used in combination with the plate and shell translational and rotational degrees of freedom and the thickness of the plate and shell is taken into account, and a corresponding three-dimension plate and shell stratification model is established. The finite element formula of the new type of composite interface unit is derived, and the constitutive relation of the bilinear form and the mixed type is given. The tangent stiffness matrix of the composite interface unit is derived and implemented in the ABAQUS implicit user custom element subprogram UEL. The combined interface unit is used to simulate the single and mixed stratification problems. The selection of several parameters in the numerical simulation and the shadow of the calculation results are emphatically investigated by the simulation of the double cantilever beam (DCB) test. The three point bending test (3ENF), the mixed mode bending test (MMB) and the single lap joint joint test were numerically simulated, and the analytical formula was deduced. The results were in agreement with the experimental results and the analytical results in the relevant literature. It showed that the combined interface unit could well simulate the single and mixed type. The beginning and evolution of layer damage. Secondly, the internal strength analysis of laminates is studied. A complete strength theory based on the failure mechanism of composite laminates is established. First, the local effect and its importance of composite materials are discussed. A calculation method for the in-situ strength of laminates based on the hypothesis of fracture mechanics is derived. Based on the experimental observation of the failure mechanism of the medium fiber compression, an improved prediction model for the failure of fiber compression is proposed. It is improved on the premise of maintaining the basic characteristics of kink model in the LaRC series strength theory, and a strength criterion is added to describe the compression failure mode of the shear driven fiber, which makes the improved model better. Adaptability. In view of the nonlinear mechanical behavior of the resin matrix under transverse compression and in-plane shear loading, a method of using equal effect to consider the nonlinear superposition coupling effect between the two is proposed, and the nonlinear constitutive relation is obtained. The theoretical prediction of the failure package line and stress strain curve in simple and complex stress state is made, and the influence of the key parameters is discussed. The results show that the strength theory presented in this paper has good prediction accuracy and adaptability, and can reflect the true test phenomenon and trend. The continuous medium damage mechanics (CD M) thought, establish a nonlinear damage constitutive relation based on failure mechanism. Combining the characteristics of the laminates continuous shell model, the corresponding damage degradation method is proposed according to the different failure mode characteristics predicted by the strength theory, and the detailed response strategies are given for many details, and the explicit user material of the commercial finite element software ABAQUS is given. In order to verify the reliability of the material program VUMAT, in order to verify the reliability of the method, the grid sensitivity test is carried out by the simulation of a loaded cube, and then the rationality of the nonlinear constitutive relation is verified by simulating the uniaxial compression test of one way plate, and then the opening of a variety of laminates in the simulated document is compressed and opened. Tensile and elevated compact tensile tests are used to demonstrate the analytical accuracy of the methods and to analyze their failure processes and characteristics. The numerical simulation results show that the proposed method has good prediction accuracy and can reflect the real mechanical behavior and failure mode of the structure.

【学位授予单位】：西北工业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB33;O346

【参考文献】