碳纤维复合材料超声振动辅助RTM工艺的浸润特性

研究了织物类型、纤维体积分数和超声振动对树脂在碳纤维织物中流动特性的影响规律，设计了超声振动辅助RTM工艺过程中单向渗透率测量装置，开展了16组渗透率测试实验，并结合COMSOL软件仿真分析了织物中的树脂流动特性。研究表明，在相同纤维体积分数水平下，斜纹编织物的纤维束间隙通道比平纹织物的更宽，2/2斜纹编织织物渗透率比平纹织物提高了约21.5%。纤维体积分数与织物渗透率呈负相关，其函数关系与半经验公式Kozeny-Carman(KC)方程吻合较好。树脂流动过程中加入超声振动，其超声空化效应、加速度效应和微射流效应作用于纤维丝束表面，提高了织物渗透率约58.2%。有限元仿真模拟了椭圆形和近矩形纤维束截面设计的织物模型的流动过程，结果发现近矩形纤维束截面高流速区域范围更广，流体向纤维布夹层浸渍的速度分量更大。超声作用于织物纤维可能带动纤维丝束蠕动，使纤维束截面趋于近矩形状，从而提高了树脂对纤维织物的浸润性。上述研究结果对优化碳纤维复合材料成型工艺和成型性能具有一定的指导意义。 

Impregnation characteristics of carbon fiber composite during ultrasonic vibration assisted RTM process

The flow characteristics of carbon fiber fabric was studied under different forming conditions, including fabric type, fiber volume fraction and ultrasonic vibration. The unidirectional permeability measurement device of ultrasonic vibration assisted RTM was newly designed. Permeability testing experiment including 16 trials was carried out, and the resin flow characteristics in the fabric were analyzed using COMSOL simulation. Results show that with the same fiber volume fraction, the fiber bundle gap channel of 2/2 twill weave fabric is wider than that of plain weave fabric, and the permeability of twill weave fabric is averagely 21.5% higher than result from plain weave fabric. The fiber volume fraction is negatively correlated with fabric permeability, and the functional relationship is in good agreement with the semi-empirical Kozeny-Carman (K-C) equation. The ultrasonic vibration is introduced into the resin flow process, and the ultrasonic cavitation effect, acceleration effect and micro-jet effect acted on the surface of fiber bundle, which significantly improves the permeability of fiber fabric about 58.2%. The flow process of fabric model, which is designed with elliptic and nearly rectangular fiber bundle section, was simulated by finite element model, and results show that the high velocity area of near rectangular fiber bundle section is relatively wider, and the velocity component of fluid impregnation to the interlayer of fiber cloth is larger. Ultrasonic acting on the fabric fibers probably drives the fiber bundle peristalsis, making the fiber bundle cross section tend to be nearly rectangular, subsequently improving the resin infiltration of the fiber fabric. Experimental results from this work have certain guiding significance to optimize the forming process of composites.