双马来酰亚胺/碳纤维蜂窝夹层结构孔隙优化

Optimization of Pores in BMI/CF Honeycomb Sandwich Structure

双马来酰亚胺(BMI)树脂/碳纤维(CF)预浸料作为蒙皮结构与芳纶纸蜂窝芯共固化工艺既要控制蒙皮的成型质量,又要控制蜂窝与蒙皮的黏接质量,同时蜂窝芯零件的耐压较小,因此针对共固化工艺过程中经常出现的孔隙问题进行研究。通过对孔隙数学模型进行分析,基于BMI树脂预浸料高挥发分和高流动的特性,对成型过程中预浸料铺层数、袋内真空压力、预浸料树脂含量调节不断优化。以无损检测和金相分析为手段,分析了成型工艺过程中的影响因素。研究发现,BMI/CF预浸料在蜂窝夹层结构中的孔隙率与铺层层数、袋内真空压力和BMI树脂含量有关。孔隙的产生主要是由于挥发分在预浸料和胶膜界面处的浓度差异引起的,当预浸料铺层层数≤10层时,蜂窝夹层件孔隙<1.5%;当预浸料铺层层数>10层时,蜂窝夹层件孔隙>1.5%。通过吸胶工艺及调节袋内真空压力能够有效地降低蜂窝夹层结构中的孔隙含量。

As the co-curing process of skin structure and aramid paper honeycomb core,bismaleimide(BMI) resin/carbon fiber(CF) prepreg not only needed to control the forming quality of skin,but also the bonding quality of honeycomb and skin,and the pressure resistance of honeycomb core parts was small.Therefore,the pore problems that often occur in the co-curing process were studied.By analyzing the mathematical model of pores and based on the high volatility and high flow characteristics of BMI resin prepreg,the number of prepreg layers,vacuum pressure inside the bag,and resin content adjustment of the prepreg during the molding process were continuously optimized.By means of non-destructive testing and metallographic analysis,the influencing factors on the forming process were analyzed.The study shows that the porosity of BMI/CF prepreg in honeycomb sandwich structure is related to the number of layers,vacuum pressure inside the bag,and resin content.The porosity is mainly caused by the concentration difference of volatile matter at the interface between prepreg and adhesive film.When the number of prepreg layers is less than 10,the porosity of honeycomb sandwich is less than 1.5%.When the number of prepreg layers is more than 10,he porosity of honeycomb sandwich is more than 1.5%.The porosity content in honeycomb sandwich structure can be effectively reduced by glue absorption process and adjusting the vacuum pressure in the bag.