CF/PEEK复合材料激光加热铺放成型冷却结晶过程建模与分析OA

Carbon fiber reinforced polyetheretherketone(CF/PEEK),as a representative of high performance carbon fiber reinforced thermoplastic composite,shows great potential application prospects in the fields of aerospace,energy storage,and rail transportation,due to its high specific strength,excellent impact and fatigue resistance,as well as corrosion resistance and high-temperature tolerance.However,the high melting point and high viscosity characteristics of PEEK resin pose new challenges to the forming process of CF/PEEK composites.Fortunately,laser source can achieve efficient and precise heating of PEEK resin.Based on this,a new method for high-quality and efficient manufacturing of CF/PEEK composites is constructed by integrating laser heat source and automatic placement technology,called as laser-assisted fiber placement(LAFP),achieving CF/PEEK components fully manufactured in one step(so-called in-situ consolidation).It is well known that the crystallinity of PEEK resin matrix significantly affects the mechanical properties of the manufactured components,such as bonding strength,interlayer fracture toughness,and impact damage performance.To this end,modeling and analysis of cooling crystallization in LAFP process are carried out,considering the crystallinity is closely related to temperature and cooling rate.The main work and conclusions are as follows: Firstly,a coupled temperature-crystallinity model was developed to simulate heat transfer and crystallization kinetics during the cooling stage in LAFP process for CF/PEEK thermoplastic composites.Two heat dissipation mechanisms were considered during the modeling process,including the heat loss from the upper surface to the surrounding air and the heat transfer from the lower surface to the metal mold. Secondly,the non-isothermal crystallization kinetics of CF/PEEK under different cooling rates was analyzed using a first-order kinetic model.Typical DSC curves of CF/PEEK prepreg tapes under different cooling rates were acquired by using differential scanning calorimeter.The results indicated that as cooling rates increased,the onset point,the peak point,and the terminative point of crystallization collectively shifted toward lower temperatures,with a corresponding reduction in crystallization duration. Finally,numerical solution of coupled physical field model was achieved through the finite element method,alongside experimental temperature and crystallinity measurements during LAFP process for CF/PEEK thermoplastic composites.A custom-developed LAFP system was adopted for the temperature measurement experiment,consisting of a placement head,a robotic arm,and a flat mold integrated with tooling temperature controller.The comparison between experimental temperature measurements and numerical results was carried out,and the maximum error was 8.2％.Furthermore,the calculation results of temperature and crystallinity fields indicated that the bottom material cooled faster than the top material,dropping to about 240℃at 0.2 seconds,while the top material still maintained about 320℃.The crystallization of the bottom material was completed within 0.1 seconds,and the crystallization of the top material began about 0.25 seconds later,which was consistent with the trend of temperature field changes.The location where the temperature cooled faster,the crystallization began earlier and lasted shorter.In addition,the mold temperature had a significant impact on the cooling crystallization process,increasing the mold temperature slowed down the cooling rate of the newly deposited layer material,thereby retarding the crystallization process of PEEK resin.