In situ void content measurements during resin transfer molding

In resin transfer molding (RTM), the void content measured after resin curing does not represent the amount of voids at the point of air-trapping. To properly verify a prediction model for the void content based on the occurrence of voids due to the air-trapping mechanism, the void content must be measured immediately at the point of air-trapping. In the present study, we created an in situ method for measuring the void content during resin impregnation by combining image analysis with a technique that visualizes the resin flow and void formation during one-dimensional RTM. Using this proposed method, we measured changes in the distribution of the void content at the air-trapping site and following resin curing. As a result, an inversion phenomenon was observed, in which the void content decreased a short distance from the resin inlet due to the time that elapsed, whereas it increased at a longer distance. This phenomenon can be explained by the ease with which the void moved and by the effect of molecular diffusion. In addition, by measuring the change in void content during the time that elapsed from air-trapping until resin curing, we clarified the behavior of the void change and the factors that affect the void content following void formation.