Research On Several Support Technologies For Digital Manufacturing Of Composite Components

Composite components have many inimitable performances such as high specific strength, high specific stiffness, designable, heat-resistant, corrosion-resistant, fatigue resistant and good stealthy, so they are being given more and more attention in many fields and being applied more and more widely in many domains including automobile, weapon, electron, aviation, space and so on. To some degree, the research level and application level of composite material reflect the science and technology developing level of a country. Especially in aviation industry, almost every advanced aircraft is closely related to sophisticated material technologies.To meet the improving manufacturing requirement of composite components on aircrafts, it is urgent to apply digital technologies and improve the current manufacturing mode and manufacturing process. Digitalization and integration of designing and manufacturing of composite components should be realized gradually. Centring on digital manufacturing of composite components, this thesis dedicated its research to several support technologies in digital manufacturing of composite components. Support technologies studied in this thesis include pretreatment processing of curved surface flattening, optimal flattening of complex ply surfaces on composite components, intelligent decision-making for composite component mold material, rapid assembly designing for parts and components of composite components tools, and so on. The main contents and contributions of the thesis are as follows:Aiming at the demands of ply surface flattening of prepreg in ply forming of composite components, some pretreatment methods of surface flattening such as triangulating, dividing, and cutting are studied. A method of surface dividing based on mesh discrete Gaussian curvatures is given. By the method, effect surface dividing results for ply surface flattening can be obtained. An adaptive method of creating cutting path is studied and realized, it takes those points whose Gaussian curvature is larger than the given threshold as start points on cutting paths and the whole cutting paths can be acquired with the shortest path generating algorithm. The adaptive method can accomplish cutting tasks on closed surfaces, one boundary surfaces, two boundaries surfaces, and multi-boundaries surfaces. To meet the requirements of flattening ply surfaces on composite components, an interactive cutting method is also given. By some key path points appointed interactively by users, it can create cutting path according to the user's demands. For improving material utilization ratio and cutting efficiency, and simplifying the subsequent packing work, a cutting path optimization algorithm is further brought forward, and it can effectively eliminate the jagged cutting paths and make the cutting paths straight and smooth.A ripple-style flattening method which uses the center-triangle as the base triangle is presented. By the method, an initial flattening with less cumulative error can be rapidly obtained. Based on the initial flattening results, an improved algorithm for surface optimal flattening based on spring-mass model is put forward. The main improvements of the algorithm are as follows: firstly, adaptive time-step improves the speed and stability of current algorithm; secondly, each overlapping region can be integrally adjusted through calculating the penalty forces of each mass in the model; lastly, both with and without the initial velocity being taken into account, the algorithm combines the advantages of the two cases, thus some key problems such as rapid adjusting overlapping region during optimal flattening processing and rapid convergence of optimal iteration can be solved satisfactorily. Using above algorithm, optimal flattenging results of complex ply surfaces with mass triangular grids can be rapidly attained and overlapping triangles brought by initial flattening and optimization process can be effectively eliminated, thus the quality of complex ply surfaces flattening is enhanced.A novel Edge-based Flattening is presented for optimally flatteing complex surface. In the optimal flattening model, length of each mesh edge is selected as optimization variables, and the error of edge-lengths between the original mesh and the flattened mesh is selected as objective function, and each internal point of the mesh being developable is selected as optimization constrain. By Newton's Method and matrix blocking technologies, the optimization problem can be solved effectively, and a developable surface which has the minimum edge-length error can be constructed. The ripple-style flattening method can be used to flatten the developable surface, thus the optimal flattening result of the original surface is obtained. Through above method, all kinds of complex ply surfaces with small quantity of triangular grids can be flattened stably, quickly and accurately, and the flattening operation can be finished more simply.The selection of materials for ply molds is very important during designing of ply molds. Based on the study of the knowledge and experience of composite components mold materials, a fuzzy decision-making method for selecting composite component mold materials is presented. Using technologies of fuzzy pattern recognition with weights, technologies of RBR and technologies of dynamic adjusting weights, the method has possessed some self adapting abilities. The decision-making method can commendably provide rapid and intelligent decision-making for mold materials of composite component.Aiming at the demands of rapid assembly design for parts and components of tools for composite components, the concept of Batch-Assembly is put forward, and several key technologies related to Batch-Assembly, such as the definition of assembly features, instantiation of parts and components and real time preview, are resolved. The rapid assembly design for bolt connection, screw connection, pin connection, and so on, is implemented by Batch-Assembly. It improves the efficiency of assembly design and lightens the labor of assembly designing considerably. Based on the analysis and research of entity-modelings in current component library of tools, parametric tables of parts and components, the method of component preview, and the method of component instantiation, a general frame for constructing component library is put forward, and tools for establishing the library, including querying components in the library, calling components from the library, previewing components, and showing main parameters of components, are designed and developed based on CATIA.