【作者】 李桂东；

【导师】 周来水；

【作者基本信息】 南京航空航天大学 ， 航空宇航制造工程， 2010， 博士

【摘要】 热压罐成型是复合材料构件的主要制造方法之一,在该方法中,构件的几何形状是由成型工装来保证的,因此,工装的质量直接影响复合材料构件的质量。在目前生产实际中,影响复合材料构件成型精度的主要因素是固化过程中的变形,现有的解决方法是通过大量的实验、反复试凑对工装型面以及结构进行修改,这样难免使得工装的制造出现加工迭代,生产效率低且成本高。本文试图通过对热压罐成型中复合材料构件的变形预测,将变形补偿纳入到成型工装的设计中,达到以成型中的反变形来提高构件几何精度的目的。针对该问题,本文对复合材料构件热压罐成型工装设计的若干关键技术进行了研究,具体包括:复合材料构件热压罐成型传热规律、变形预测及其工装型面补偿技术、复合材料构件工装快速设计技术等。所取得的主要成果如下:针对热压罐成型中工装对复合材料构件内部温度场的影响,分析了复合材料构件沿厚度方向的传热规律,建立了热压罐成型的复合材料构件一维热传导模型。该模型将工装支撑结构等效为改善工装模板下表面传热效果的扩展装置,能有效的描述工装对复合材料构件传热的影响。通过解析法对热传导模型进行求解,得出了复合材料构件、工装模板以及工装支撑沿复合材料构件厚度方向的温度分布方程;利用傅立叶级数对温度分布方程进行了简化,得到复合材料构件和工装结构沿厚度方向的近似温度分布方程,该方程可用于分析不同工装材料以及升(降)温速率对复合材料构件温度分布的影响。提出了基于有限元方法的复合材料构件热压罐成型变形预测方法和基于构件型面节点变形的工装型面补偿算法。在分析固化过程中不同形态下的树脂力学性能的基础上,建立了不同形态下树脂的复合材料力学模型和复合材料固化过程中的三维热-化学模型,通过Newton ? Raphson迭代法对该模型进行了求解,基于有限元方法实现了对复合材料构件变形的预测;根据变形预测的结果,以成型后的反变形来提高复合材料构件的几何精度为目标,实现了对工装型面的补偿。通过与现有文献中的实验结果进行比较验证了本文方法的正确性,并将该方法应用于某飞机蒙皮的变形预测及其工装型面的补偿。针对工装模板的快速设计,提出了复合材料构件工装型面快速等距算法,该算法能将工装型面和等距曲面通过同一隐式曲面进行表达,较好的保持原始曲面的细节特征,避免传统设计方法中烦琐的曲面修复、等距、裁剪等操作。针对模具支撑结构的快速设计,提出了工装支撑结构的级联参数化设计方法,将工装支撑的设计参数分为支撑层、具体层和草图层,设计者只需关注支撑层的设计参数就可通过级联驱动规则设计出支撑结构。提出了复合材料构件工装型面的可加工性多属性评价算法,设计人员可利用工装型面以及工装结构本身的几何特征信息判断工装的可加工性,对复合材料构件工装设计有较大的参考价值。提出了基于八元集合模板和专用模块的工装设计系统集成方法,该方法通过模板技术将设计过程中的专家知识和经验集成于设计系统中,以此支持工装设计过程中的创新设计活动中,克服了模块化设计方法柔性不足的问题,同时结合模块化设计方法的优点,对工装结构相对固定的部分,采用专用模块的方法集成于工装设计系统中。基于以上的工装设计系统集成方法,开发了复合材料构件工装设计系统。更多还原

【Abstract】 Autoclave processing is one of the most popular manufacture methods of the composite part, in which the part shape is determined by the tool surface, thus the tool quality will directly influence the manufactutre quality of the composite part. In practice, the main factor which influences the manufacture precision of composite part is the deformation during cure process, and with the exisiting methods a lot of experiments and trial-and-error efforts must be done to modify the tool surface and structures, and all of these methods are costly and time-consuming. In order to improve the geometrical precision by using the part reverse deformation, the author proposes the measures to predict the part deformation during the cure process, and compensates the deformation to the tool design. In this thesis, some key technologies in tool design of composite parts undergoing autoclave processing are researched, which include heat transfer rules of the parts during the cure process, deformation predication of the composite parts and the tool compensation methods, and the rapid design methods of the tool surface and structures etc..The main contents and contributions of the thesis are as follows:Aiming at the tool influence on the internal temperature distribution of the composite parts in the autoclave process, a one-dimensional heat transfer model in the transverse direction of the composite parts is established after analyzing the heat transfer rules of the compoiste parts. In this model the tool eggcracting structures are treated as expanding devices of improving the heat transfer effects of the bottom surface of the tool body, and this method can effectively describe the tool influence on the composite part. The temperature distribution solutions of the composite part, the tool boby and the eggcracting strutures in the transverse direction of the composite part are given by an analytical approach. Then, the approximate temperature distribution equations of the structures can be derived by the Fourier progression. These approximately temperature distribution equations can be used to analyze the influence of the tool materials and the temperature rise (drop) rate on the temperature distribution of the composite parts, etc.A Finite Element based predication method of the composite part during the autoclave processing and a tool surface compensation method based on the nodes deformation of the part surface are proposed. A material mechanical model based on the resin state and a three-dimensional thermal-chemical model based on this material model are established by analyzing the resin mechanical performances in different states during the cure process. The Newton-Raphson method is employed to solve this non-linear material model and thermal-chemical model, then, the part deformation can be predicated by the Finite Element method. With the predication result, the tool surface is compensated by using the part reverse deformation after curing process. Finally, all the methods and algorithms are verified by comparing the results to the experimental results in the references, and the methods are applied to predict the deformation of an aircraft skin structure and the tool surface compensation.As for the rapid design of the tool body, a rapid offset algorithm of the composite part tool surface is introduced, and this algorithm can express the tool surface and the offset surface with implicit surface type, and this implicit surface can keep the most detailed feature of the initial surface. Moreover, the algorithm can release the designers from the complicated trial-and-error efforts on the operation of surface repairing, surface offsetting and surface trimming etc. To design the tool eggcracting structure, a concatenated parametrical design method is proposed. In this method the structure design parameters are divided into three layers: the support layer, the substance layer and the sketch layer, and the designers can get the structures by inputting the support layer parameters by this concatenated parametrical design method. An algorithm of multi-attribute evaluation in manufacturability analysis for the tool surface of the composite part is proposed. The designers can evaluate the tool surface’s manufacturability according to the geometrical features of the tool surface and the tool structures, and also the algorithm has great value to the tool design.An integrated method of the tool design system based on the eight element set design pattern and dedicated module is introduced. This method integrates the design knowledge and experiences of the experts into the design system by the template technology, so the design system can support the creative design activity during the design process, and overcome the disadvantages of lacking flexibility with the module design method. Combining with the merits of the module design method, the dedicated module design method can be applied to integrating the comparatively steady tool structure into the design system. Finally, a composite tool design system is developed.更多还原