Research On Key Technologies Of Computer Aided Design System For Large Size CFRP Parts Framed-mould

Autoclave molding is the main method to manufacture CFRP parts with high quality and large size for aerospace industry, in which the key special equipment is the framed-mould. The design quality of the mould determines the size precision, shape precision and internal quality of the final parts, so that it has an obvious influence on the using performance of the parts. At present, design of the mould mainly depends on experience and repeated trial, which leads to low efficiency and high consumption. In order to solve these problems, this dissertation studied the automation, intellectualization and rapidity method of the design process for the framed-mould based on the state-of-the-art curing deformation simulation, shape precision control method, computer-aided rapid design system and optimization design. The latest technologies such as computer-aided modeling, analysis and search were fully utilized to improve the automation level of framed-mould design. The main contributions of this dissertation are as the following:The design considerations of the framed-mould are summarized and the original mould design process was optimized based on the detailed analysis of the characteristics of the autoclave molding. The general framework of the rapid design system for the framed-mould was designed, including the mould design resource library, the template library and the design aid tool library. The data interfaces between the various components were defined as well.The design guide template of framed-mould was researched. Based on the functional structure analysis of the mould, the architectural features and design parameters of mould design were divided, and the parametric rapid modeling system of framed-mould was established using the constructive solid geometry and boundary representation method. An integrated data structure for the mould structure design and finite element simulation was built, the automatic mesh generating algorithm for the mould structure was established based on the mapping method, and the integration guiding template for the CAD/CAE design and analysis of framed-mould was constructed using the XML presentation method. The presentation method of framed-mould design case was built and the hierarchical retrieval method of the design case was provided by dividing the retrieve information granularity, so the reuse of mould design based on the cases was realized.A shape precision control method based on precompensation geometrical tool was proposed. After analyzing the component parts and causes of the deformation during manufacturing process, the deformation was divided into the curing shrinkage deformation and buckling deformation induced by the interaction between mould and part. Two numerical computation methods were established for the above two types of deformation, which can predict the deformation rapidly and precisely. The shape precision control method was developed based on the above simulation method, which can decrease the part deformation by compensating the simulated deformation to the initial mould surface repeatedly. This method can effectively improve the shaping accuracy and reduce the deformation.The optimum design method for framed-mould based on metamodel was researched. A numerical calculation model to describe the mould deformation process induced by the heating expansion and pressure was built, and the mould deformation simulation was conducted based on the heat transfer simulation. Using the simulation tool, the influence of the mould design parameters on the surface temperature difference and deformation was analyzed by single-factor multi-level tests and comparison. The results revealed that the mould surface thickness and the aperture ratio of the braced frame are the sensitivity parameters of the design result. Ignoring the insensitive parameters, the metamodel optimum computation model was established for the mould bracing structure, which can be applied to optimal design framed-mould efficiently.The Computer Aided Framed-Mould Design system was developed based on the above-mentioned key technologies. Based on the database system, the prototype system was developed using object-oriented programming language, and the feasibility of the above key technologies was validated preliminarily.