Research On Key Technologies For Tool Design Of Composite Components Undergoing Autoclave Processing

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.