大型薄壳制件真空辅助树脂传递模塑工艺充模方案仿真分析及优化

针对大型树脂基复合材料制件不适于用实验试错法进行充模方案设计的问题,在分析树脂流动规律的基础上将大型薄壳件的求解区域分解,仿真分析了不同充模方案下树脂在纤维中的流动行为和模腔内压力变化,提出在制件填充面积等分处设置流道的方法,选择和优化大型薄壳制件的充模方案。结果表明:①对于不便进行实验试错法进行真空辅助树脂传递模塑(VARTM)工艺充模方案设计的大型薄壳制件,可以采用数值模拟的方式,以达西定律、能量守恒定律等为计算依据,求解压力场和速度场,对比不同仿真方案的充模时间等数据合理安排注胶方式方法,指导VARTM工艺制备大型复合材料制件合理安排注胶方式,提高生产率、减少因树脂浸润不均匀产生的缺陷。②对于大型薄壳类制件,忽略厚度方向尺寸,影响充模时间的主要因素为流道长度和树脂流动距离。选取尽可能长的注胶流道,合理设置流道位置以减少树脂流动的距离;长流道可以增加树脂瞬时注入量、提高较长时间的压力差;而树脂流程越长,树脂前锋处压力损失越大,流速越慢。③试验提出了制件填充面积等分处设置流道的方法。将大型薄壳工艺制件充模面积等分,注胶流道布置在垂直于制件长度方向的面积等分线上,可缩短充模时间并减少制件两端的树脂富集现象。对于较狭长部分可再次进行面积等分设置流道,以免造成树脂流程过长压力流失过多;而对于较宽阔部分不宜设置过多流道以免树脂前锋稳定前互相接触造成制件充模不均匀。

Simulation and Optimization of Filling Scheme for VARTM Process of Large Thin Shell Parts

Since large resin based composites are not suitable for the optimization of filling scheme design by trial and error method,based on the analysis of resin flow rules,the solution area of large thin shell parts was decomposed,the flow behavior of resin in the fiber preform and the pressure change in the cavity under different filling schemes were analyzed,and the method of setting flow channel at the bisection of the filling area of the part was proposed,so as to select and optimize the resin filling scheme of large thin shell parts.The results showed that:①For the large thin shell parts which were inconvenient to design the filling scheme of vacuum assisted resin transfer molding(VARTM)process by experimental trial and error method,the numerical simulation method could be used to solve the pressure field and velocity field based on Darcy’s law and energy conservation law,reasonably arrange the injection method for the filling time and other data compared with different simulation schemes,and guided the VARTM engineering,in order to improve the productivity and reduce the defects caused by the uneven resin infiltration,the way of glue injection should be arranged reasonably.②For large thin shell parts,ignored the thickness dimension,the main factors affecting the filling time were the length of the runner and the resin flow distance.Selected the longest injection channel as far as possible,reasonably set the position of the channel to reduce the distance of resin flow;the long channel could increase the instantaneous injection of resin,and increase the pressure difference for a longer time;the longer the resin flow,the greater the pressure loss at the resin front,the slower the flow rate.③The experiment proposed a method of setting runners in equal parts of the filling area of the workpiece.Dividing the mold filling area of a large thin shell parts into equal parts,and arranging the injection runner on the area bisecting line perpendicular to the length direction of the part could shorten the filling time and reduce the resin accumulation at both ends of the part.For the narrower part,the flow channel could be set up again in equal area to avoid too much pressure loss due to too long resin flow;while for the wider part,too many flow channels should not be set to avoid uneven filling of parts caused by mutual contact before the resin front is stable.