Abstract: Vacuum assisted resin transfer molding (VARTM) is often used to manufacture large and complex composite components. Monitoring the resin flow in the fiber preform in real time and human intervention in the manufacturing process can effectively avoid the formation of internal defects in composite products. Among them, real-time monitoring of the flow rate of the resin flow front provides a key technical basis for accurately controlling the negative pressure level in the molding process and intervening in the resin infiltration process. In this paper, the flow velocity parameters of resin flow front in VARTM process will be studied. Through the ultrasonic propagation theory, an ultrasonic monitoring characteristic model based on circular piezoelectric chip active sensor will be established to monitor the changes of ultrasonic pulse echo at the mold resin interface to identify the arrival position of resin flow front. Gaussian and elliptic curve parametric models are introduced to calculate the flow velocity of flow front. Finally, piezoelectric wafers with different frequencies are selected to conduct experiments on plexiglass plates with various thicknesses. Combined with the data, the accuracy and effectiveness of the flow velocity calculation model are evaluated. Finally, it was found that the results of velocity calculation through the parametric curve model were in good agreement with the actual situation, and the accuracy was in line with expectations. Moreover, the comprehensive performance of the Gaussian curve model was better than the elliptic curve model, but the elliptic curve model performed better in small thickness molds.

Key words: vacuum assisted resin transfer molding, flow front velocity monitoring, piezoelectric chip, parametric curve model, composites