【作者】 张芳芳；

【导师】 刘才； 姜文光；

【作者基本信息】 燕山大学 ， 机械设计及理论， 2014， 博士

【摘要】 编织复合材料以纤维束相互交织为主要结构特征，材料的整体性能更加优异，能够从根本上克服传统层合复合材料层间强度低、易分层的缺点，这种材料具有更均匀的力学性能和更好的可设计性，可以很好地满足航空航天领域对材料结构减重和高承载性能的要求，应用前景十分广阔。而复合材料所应用航空航天的领域，多为高温或冷热交替的恶劣环境，同样需要对材料的热学性能进行设计，因此对编织复合材料力学和热物理性能研究及相关的系统软件预测平台研究具有重要的研究意义。本文首先参考材料试验有关规定，确定了三维四向编织复合材料试样尺寸、试样的夹持方式及应变的测量方法，联合材料试验机和数据测量系统对三维四向编织复合材料的纵向模量和强度进行测量，利用显微镜对断口进行观察与分析，为后续模拟分析提供了验证依据。同时基于Tcl语言与ANSYS计算平台实现了编织复合材料预测系统中数据存储模块开发，为后续开发预测系统软件平台提供了试验数据和相应的存储模块。基于区域叠合思想，针对复合材料复杂细观实体的网格生成问题，提出了直接网格建模而后切割的参数化单胞网格建立方案，根据原始单元与切割面的相对位置关系，分别给出了六面体单元14种，三棱柱单元19种和四面体单元3种再分形式。通过ANSYS代码数据库接口实现Fortran程序与ANSYS软件间高效的数据传递。通过该方法提高了复合材料中复杂实体网格建模效率，为复合材料力学和热学性能分析及性能预测系统软件平台建立奠定了基础。基于区域叠合方法，给出了增强相单元与基体单元间力学和热学自由度间协调关系和叠合区域材料性能匹配方案。分别给出了便于在ANSYS和ABAQUS有限元软件中施加的力学和热学周期性边界条件的数学形式。提出结果映射方法处理基体单元场变量结果显示问题。基于区域叠合参数化单胞网格模型建立方案，构建了编织复合材料性能预测系统的程序框架。针对二维三轴编织复合材料细观参数化单胞建立问题，推导了二维三轴编织复合材料单胞模型细观尺寸关系。引入周期性要求推导了空间三次周期样条的求解方法，给出了周期三次样条曲线段内任意一点处单元材料主方向的求解算法。同时该模型中的编织纤维束考虑了不同位置处纤维束截面的扭转，得出了用于二维三轴编织复合材料力学和热物理性能预测的更为精细的参数化单胞模型。分别根据力学以及热学有限元理论，给出弹性常数、传热系数和热膨胀系数的计算方法。基于该方法给出了二维三轴编织复合材料刚度和热物理性能规律。针对编织复合材料渐进损伤分析问题，基于Murakami损伤理论建立了正交各向异性损伤本构模型，通过三维Hashin与Mises准则判断增强相和基体的初始损伤，通过等价位移控制损伤变量的演变。进行损伤分析时，联合应用了ANSYS与ABAQUS软件，利用APDL语言编写了参数化模型向ABAQUS关键词模型的转换程序，在二维三轴编织复合材料单胞模型中引入了界面单元，利用UMAT用户子程序接口开发了材料子程序，分析了典型大小编织角二维三轴编织复合材料横向和轴向拉伸强度和损伤演变规律。建立了三维四向编织复合材料参数化单胞模型，基于ANSYS有限元软件，分析了三维四向编织复合材料刚度和热物理性能随编织角和纤维体积含量的变化规律。联合应用了ANSYS与ABAQUS软件，引入界面单元分析了典型大小编织角三维四向编织复合材料纵向拉伸强度和渐进损伤演变过程，所预测结果与试验结果吻合较好，验证了上述方法的正确性。更多还原

【Abstract】 Braided composite is composed by interlock fibers and matrix, its overall materialperformance is more excellent to overcome easier layering and lower intensity of thetraditional laminated composite material. Braided composite has more uniformmechanical properties which can be easy to be designed. It can satisfy high weight andhigh load carrying requirements for aerospace structural material. Because environment inaerospace is extreme hot and cold, predication for thermal properties of materials is alsorequired. Therefore it is very significant to predicate the mechanical and thermo-physicalproperties of braided composites and design associated prediction system softwareplatform.Firstly, the methods such as specimen dimension, clamping method and strainmeasurement of three-dimensional braided composite tensile test specimen are determinedrefer to the relational standard of other material tensile test specimen. The intensity andelastic modulus are obtained by combination material testing machine and datameasurement system. Microscope photos of fracture surface are obtained as reference forsubsequent simulation analysis. Using Tcl language based on ANSYS computing platformto achieve a braided composite property predication system, the experimental data isstored in the corresponding storage module which is developed for braided compositepredication system.Based on domain superimposed thinking, a direct meshing method is put forward forthe problem of meshing complicated entities composing of the reinforcement and matrix.The parametric cell meshed by hexahedral element is built with cutting method. In cuttingalgorithm, thirty-six conditions are included based on relative position between unit cellboundaries and elements, in which cutting conditions for hexahedral are fourteen, cuttingconditions for prism are nineteen, cutting conditions for tetrahedral are three. The code ofelement extracting algorithm is written in fortran language. The datas are transferred fromself-written code to ANSYS database efficiently. It is the foundation for developingcomposite mechanical and thermal prediction system software. Based on domain superimposed method, the relationships between degree of freedomof elements from reinforcement and matrix are given and the matching methods ofsuperimposed region mechanics and thermal properties are determined. In order to applyperiodic boundary condition in ANSYS and ABAQUS software, new mechanical andthermal periodic boundary conditions are given. The results mapping method is putforward for postprocess the results from gobal elements. The framework of predicationsystem software of braided composite is determinted based on parametric unit cell createdby domain superimposed method.The relationship between structural parameters of the unit-cell model are given,which are the basis to establish parameterized unit-cell model of triaxial braidedcomposites. The expression of cubic periodic spline can be obtained for introducingperiodic condition, and the calculation method of material principle directions at any pointwithin a given period cubic spline curve are described. The cross section torsional atdifferent positions are considered, so a more sophisticated parameterized unit-cell modelwhich are used to predict the mechanical and thermal physics properties of triaxial braidedcomposites can be established. The methods of calculating macroscopic elastic constants,thermal conductivities and thermal expansions are obtained basised on mechanical andthermal finite element theory. The laws of elastics and thermal physics of triaxial braidedcomposites are obtained.In order to investigate the progressive damage and failure process of composites, thedamage mode based on Murakami damage theory is established.3D Hashin damagecriterion with various damage modes and Mises criterion are considered for predictingdamage initiation of tows and matrix, respectively. The damage progression of tows andmatrix are controlled by equivalent displacements. ANSYS and ABAQUS software arecombined to analysis damage process through conversion process written by APDLlanguage can used to translate APDL model into ABAQUS keywords model. Interfaceelements are introduced in unit-cell model of triaxial braided composites. Theprogressive damage and failure strength of composites under different tensile loadingsare obtained by material subroutine which is developed by UMAT material subroutineinterface. The parameterized unit-cell model of3D four-direction braided composites isestablished by ANSYS software. The laws of elastic and thermal physics of3Dfour-direction braided composites are obtained. The progressive damage and failurestrength of composites with typical small angle and typical large angle under tensileloading are obtained by combination of ANSYS software and ABAQUS software. Theexperimental results are compared to verify the correctness of the method.更多还原