Cross-sectional monitoring of resin impregnation using an area-sensor array in an RTM process

It is difficult to visualize the flow in the cross-section direction, and most conventional methods for monitoring resin flow are limited to the in-plane direction. This study investigates the monitoring of the cross-section of resin impregnation using an area-sensor array during a resin transfer molding (RTM) process. The area-sensor array is mounted on a thin polyimide film that is integrated with the inter-digital electrode array and associated wiring, and forms the bottom layer of the stacked composite laminates. Each area-sensor is square-shaped and measures the capacitance and electrical resistance of the sensor region. First, we constructed the equivalent electrical circuit model of in-plane and out-of-plane impregnation. Using this model, we proposed a method to identify the flow direction and the ratio of the impregnation thickness by measuring the electrical capacitance and resistance. The validity of the model was confirmed by comparison with the experimental results. To demonstrate the applicability of the proposed method, the area-sensor array was applied to monitoring the resin injection through-thickness to the glass fabric laminates. As a result, the cross-section of the impregnated area could be estimated and the estimated area provided a good match to the actual impregnated area.