Active Void Suppression in <scp>RTM</scp> of 2. <scp>5D</scp> Quartz/Phenolic Composites via Sensor‐Guided Gradient Pressure Injection

ABSTRACT While high‐performance 2.5D quartz/phenolic composites are crucial for aerospace applications, ensuring their manufacturing quality remains challenging due to the complex formation mechanisms of dual‐scale voids. In conventional constant‐pressure resin transfer molding (RTM), the uncontrolled decay of flow‐front velocity often promotes void formation within and between fiber tows, lowering composite performance. To address this issue, this study proposes a sensor‐guided gradient‐pressure RTM strategy that integrates in‐mold sensing, empirical correlation, and stepwise pressure regulation. By establishing an empirical correlation between flow velocity and void content to identify an optimal impregnation window, a closed‐loop control framework was developed. This framework utilizes real‐time feedback from an in‐mold pressure sensor array to adjust injection pressure in a stepwise manner, thereby maintaining the flow‐front velocity within the target range throughout the filling process. Results demonstrate that, compared with conventional constant‐pressure injection, the proposed strategy significantly reduces the overall void content to approximately 0.9% and effectively mitigates the local accumulation of macro‐ and micro‐voids. This work provides an effective technological pathway for optimizing the molding quality of high‐performance 2.5D structural composites.