Integral pressure transducer array for RTM processing of composites

A reliable, inexpensive, and non-invasive pressure transducer array was developed based on commercially available technology for use in resin transfer molding (RTM). The system consists of machining an array of blind holes in the exterior of the mold to create thin diaphragms at the bottom of the holes. Semiconductor strain gages are mounted on these diaphragms to form pressure sensors. This system has high temperature capability, is compatible with complex geometries, and does not require resin specific calibration. In addition, it has potential multifunctionality; it can record pressure, flow front, and onset of gelation. A mold was designed and fabricated with an array of nine transducers. The system was calibrated at various temperatures with compressed air, and subsequently checked with actual resin injection. A method correlating the gate pressure and the transducer signal was used to pinpoint the flow front arrival at the different transducer locations. The effectiveness of the system was verified by using a mold with a transparent top and relating the transducer signals with the visually recorded resin flow pattern. The method can be transferred to and implemented easily in an industrial environment.