Nowadays, polymer matrix composites are widely used for aerospace, automotive and railway applications. For equivalent properties, these materials are lighter than metallic parts that makes them very attractive. In this context, thermoplastic-based composites, especially acrylic-based ones, deserve to be considered as they exhibit good mechanical properties in terms of stiffness and resilience. Furthermore, they can be more easily recycled as opposed to thermoset polymers. Manufacturing structural composites requires to produce good qualities parts with complex geometries while maintaining short processing cycles to stay cost-effective. For this purpose Resin Transfer Molding (RTM) has been selected to process these composites. Indeed it is a low temperature closed-mold process allowing for manufacturing complex continuous fibers-reinforced parts. However, it requires precursors with a very low viscosity (η<1Pa.s) to ensure a good dry preform impregnation. Thermoplastic polymers which own a very high viscosity in molten state cannot be directly injected. Idea is to use an acrylic-based reactive formulation exhibiting a very low initial viscosity and which can be subsequently polymerizes via a radical mechanism once the mold filled and the preform fully impregnated. To envision the mass production of high quality TP-based parts, it is necessary to ensure the reliability of the process. In particular the exact conversion and viscosity have to be monitored all along the RTM processing step. Indeed if these parameters are not well controlled, preform impregnation and polymerization rate can be unsatisfying which may decrease final properties. Therefore, our strategy was to fit an RTM mold with several dielectric sensors in order to in-situ monitor electrical properties upon cure. Conversion and viscosity evolution versus time have also been determined ex-situ. Finally in-situ and ex-situ measurements have been related to build abacus. Thus it was possible to track conversion and viscosity evolutions of the acrylic-based system with time at different locations of the RTM mold.