Curing Temperature Field Tradeoff Design Method Of Large Scale Composite Material Structure In Autoclave Process

Advanced composite materials have achieved comprehensive recognition both at home and abroad in the aeronautical and aerospace industry for their advantages of high specific strength and high specific rigidity. As composite structure finds increasingly wider application in practice, the concept of structure design has achieved a qualitative leap. The original equivalent design method (the composite structure design based on metal structural parameters) has evolved into integrity design method which takes full advantage of composite designable characteristic and components characteristic of curing and forming simultaneously. As a consequence, in aviation field advanced composite component design tends to be intensive and large-sized in order to further meet such requirements as diminishing weight and reducing assembly. However, structure maximization also brings an increasing difficulty to large complex structure manufacturing of advanced composite materials. How to control the manufacturing quality has become a problem of great importance. On the other hand, manufacturing cost of advanced composite materials is rather high. This has made cost control a problem engineers need to confront in composite structure design.Autoclave technology is still the main technology at present in large complex structure manufacturing of advanced composite materials. During autoclave curing process, the temperature distribution is the most important factor in process control. To ensure component curing quality, it is necessary to keep an appropriate temporal and spatial distribution of the component temperature field. Proper temperature field control will also helps to decrease the manufacturing cost in autoclave process. In conventional process design, technical parameters are usually determined on the basis of limited experiments. This method can ensure quality but cannot perform quantitative control. Meanwhile, conventional technical parameters also results in increasing cost. Therefore, new curing temperature field design method should be established to meet the technical requirement of advanced composite material development. This study focuses on autoclave technology in large complex structure manufacturing of advanced composite component. Based on further study on manufacturing costs in autoclave technology and on temperature field in curing process, the study establishes a tradeoff design method which tries to find a balance between the curing quality and the manufacturing cost.The work mainly studied the external temperature field during the composite curing process in autoclave technology. Using hexahedral structural grid in mesh generation, finite volume method, unsteady three-dimensional NS equations (continuity equation, motion equation and energy equation) and the turbulence model which reflects the turbulence characteristics, an unsteady three-dimensional numerical simulation method was established which reflected the temperature variation of forced convection heat exchange in autoclave. For the reason that frame mould has a great impact on the component temperature field in curing process, it was selected as key research objective. Numerical simulation on frame mould temperature field was performed and then a series of verification experiments were carried out to verify the effectiveness of the simulation methodology. Because mould design plays a very important role in process design, the research explored the impact of frame mould structural parameters on mould temperature field through a series of numerical simulation examples. On this basis, the impact of process parameters and mould location in autoclave on the mould temperature field was studied. Valuable conclusions are achieved accordingly.The temperature field of advanced composite structure in curing process is the coupling result of external temperature field and heat release from internal exothermic curing reaction. Previous studies on component temperature field usually focused on temperature field along the thickness direction and usually put an over-simplified treatment on component external temperature field. This study, however, using simulation method on the external mould temperature field and exothermic curing reaction model of advanced composite material QY8911/T700 prepreg (used widely in aeronautical product), performed a simulation on coupling temperature field for variable thickness skin structure in curing process. On the basis of simulation results, the characteristics of the temperature field were analyzed. Then through a series of numerical simulation examples, the impact of advanced composite component structural parameters and process environment parameters on component curing temperature field was achieved.On the based of the domestic situation in manufacturing of advanced composite materials, with the cost definition in Design For Cost (DFC), the work first made clear of the classification and characteristics of cost during the manufacturing of the advanced composite materials. With the process cost estimation method, the work has established the process cost estimation theory frame, procedure establishment of standard model and the manual working hour estimation method which are applicable for technical process and management of small scale production. Focusing on a typical autoclave process, the study expounded on the establishment of standard procedure estimation model and implementing process for cost estimation.The study analyzed the characteristics of QY8911 resin in curing process and put forward the control indicators which characterized the curing quality during the process; established curing process cost model in autoclave technology, put forward curing quality- cost tradeoff parameters, using coupling temperature field simulation method (established earlier in this study) and curing degree estimation method and curing quality controlling indicators; established tradeoff design method of process parameters of curing temperature field in autoclave technology. By means of tradeoff design method, the study made process parameter scheme optimization for stiffened composite panels of large complex composite component and analyzed the process.