Full-field monitoring of the resin flow front and dry spot with noninvasive and embedded piezoelectric sensor networks

Vacuum-assisted resin infusion (VARI) process has been proven to be an effective-cost technology for manufacturing large-scale composite structure with complex geometries and has a broad development prospect in industry fields, especially in aerospace. The resin impregnation, a crucial stage of the VARI process, can easily lead to dry spots and seriously reduce product quality or even lead to scrap due to improper resin flow. The non-invasive piezoelectric sensor (NPS) network and embedded piezoelectric sensor (EPS) network composed of Stanford Multi-actuator Receiver Transducer Layer are employed for full-field monitoring of the resin flow fronts and accurate localization of the dry spot defects. Also, an innovative experimental technique for creating dry spot defects is presented in this research. Based on the analysis of the Lamb wave signals, the A₀ mode from the NPS network and the S₀ mode of the EPS network are ideal for the monitoring of dry spots. Additionally, by fusing the impact of dry spot defects on the Lamb wave and the probability-based diagnostic imaging algorithm, a new damage index is proposed to precisely locate the dry spot defects. The experimental results further indicate that the method proposed can provide effective full-field monitoring of the resin flow front and dry spot defect locations.