structures, materials ) Aeronautic industry has always shown an increasing demand to produce light and efficient structures, while maintaining high standards of performance and safety. In case of composite structures, this requires a direct control on the production process which can be obtained trough the presence of a reliable monitoring system. Nowadays the most common technique used in the production of high performance composite materials is the vacuum bagging/autoclave lamination. In the last years, techniques based on resin transfer moulding RTM have shown many advantages compared to traditional ones; in fact, these techniques have a number of advantages, particularly in the production of complex shape components with strict tolerances. Moreover, these closed moulding techniques present limited volatile emission with important benefits for workers health. In previous works (1, 2) graphite-epoxy composite parts were produced by vacuum assisted RTM technology (VaRTM), with mechanical prformances quite similar to those obtained by classical vacuum bagging technique. These promising results encuraged us to develop a monitoring system for VaRTM process, able to control the quality and the repeatability of the process, and above all, to assess the deformations evolution during the production. VaRTM technology, unlike vacuum bagging technique, employs dry fabric, with no impregnating resin; these fabrics are cut in the right shape and, then they are stacked into a preform placed inside the mould. This preform will be compacted when the mould is closed; after this step, the set up is heated up to the infusion temperature and the resin is injected at high temperature until the mould is fully filled. At the end of the filling stage the mould is heated again up to the curing temperature (usually higher than the infusion temperature). When the curing process is finished the mould is cooled down to room temperature, opened and the product is extracted. The research activity was developed in two phases. In the first phase all the materials properties relevant for the VaRTM process were characterized. Epoxy resin RTM6 (Hexcel) and two carbon fabrics cc420 and cc600 (Seal S.p.A) were employed. Permeability measurements of these two fabrics with the RTM6 resin at the infusion temperature were carried out; the viscosity curves of the resin were determined at different temperatures, to obtain the relationship between curing time and process temperature. The second phase was focused on the design and set up of a monitoring system, able to follow all the production stages during VaRTM process. In the monitoring system construction a number of requirements were considered: the sensor resistance to high process temperature (180°C), the ability to follow the fluid front during resin infusion, the ability to measure variation of temperature and to measure the extent of deformations during the production of the laminate, the low cost. In order to respond to all the requirements, a monitoring system based on fiber optic sensors was adopted; an adequate choice of the sensors guarantees minimum embedding problems, perfect compatibility with resin and resistance to high temperature. For the fibre optic sensors embedded in the composite layup the possibility of monitoring the component during the post-production testing and operating life was also considered; the same sensors can, in fact, be employed as deformation transducers, for example within a health monitoring system architecture (3). We used to different types of sensors: simple fibre optics (FO) to record the resin front during the infusion, and fibre optic with Bragg grating printed in the core (FBG). These sensors work as deformations transducers, they are able to record deformations due to temperature variations and pure mechanical