In front of the traditional materials, polymeric matrix composites have demonstrated their suitability for a great number of applications. This is mainly due to their lightness, excellent mechanical properties and chemical resistance. However, today is still necessary an improvement in regards to the manufacturing processes of composites in order to reduce their costs and make them even more competitive materials, which will permit take advantage of their characteristics for the benefit of the whole society.
The main objective of the present work is the development of an original and innovative approach for the optimal design of the vacuum assisted resin transfer moulding processes as a suitable technology for composites manufacturing. It consists of an expert system which is able to reduce the necessary effort for the optimization of the process and to avoid the trial and error strategy in favour of the virtual prototyping in the development of the tools required.
Existing background on this topic is mainly on the research done up to date by two different groups: on one side is necessary to quote the Center for Composites Materials (CCM) from the University of Delaware, USA, in which the Professor S.G. Advani and col. have carried out many works in this field and the development of an original simulation software and several approaches for controlling the flow front of the resin in such manufacturing processes. On the other hand, the Chaire sur les composites ā haute performance (CCHP) from the University of Montreal (Canada), which is leaded by F. Trochu, has a background as noticeable as the previous one. In order to develop the present research, the author has been involved in the work carried out by both Centers on a daily basis during two different periods. The results have been shown in the 10th International Conference on Flow Processes in Composites Materials (FPCM10), where not only Advani or Trochu but also international researchers as E. Ruiz, S. Bickerton, C. Binetruy and T. Lundströn presented their works.
In order to set up and validate the expert system, the following original contributions have been carried out:
1.	An original experimental set up has been developed for the characterization of the flexible permeability of preforms with the main aim of a fast simulation, with a reduced computational effort and limited necessity of experimental characterization of raw materials (mainly permeability), which permits the preliminary design of the infusion tools ensuring i. the complete filling of the cavity and ii. a reduced cycle time in the infusion process.
2.	The flexible permeability bench has been set up with a serial of preforms typically employed in the technology of composite materials, such as continuous fibres mats, multidirectional fabrics, hybrid reinforcements with core to enhance the flow of the resin and natural fiber preforms. In addition, the influence of the curvature radii in the tools over the flow of the resin has been studied in the present work
3.	It has also been studied in the present work a suitable approach for monitoring the position of the flow front and the curing degree of the resin. The so-called heat flow sensors have been successfully tested in the event of the infusion process. Such sensors permit the measurement of the heat transfer between the resin and the mould the energy generated by the polymerization reaction itself. It may be optimized the cycle time to produce a part because demoulding is done just in time.
4.	A commercially available software for resin transfer moulding simulation has been employed for the simulation of the infusion process by incorporating the concept of flexible permeability. This means the development of a low cost, fast and reliable approach for the virtual prototyping of the vacuum assisted resin transfer moulding processes which, as will be explained later, require a higher cost in terms of computational effort and characterization than the one proposed in the present work
5.	The experimental characterization of the flexible permeability has been employed for the simulation of the filling of an infusion mould by employing several preforms . The results obtained have been compared to the pilot plant experimental filling trials.
Partial results obtained throughout this work have been shown in several national and international scientific congresses. In this sense, the achievements in the sensorisation of the resin transfer moulding processes, the development of the flexible permeability bench, the influence on the characterization of the permeability by the geometry of the mould, and the validation of the flexible permeability measurements by using pilot plant comparisons have been carried out. In addition, further tasks to those in the scope of the present thesis have also been introduced.
At the light of the results it is possible to conclude that the proposed approach permits the simulation of the vacuum assisted resin transfer moulding processes with a low computational cost and a reduced characterization of raw materials when it is compared to the analytical solution. This permits its implementation in an industrial environment. In addition, the control system proposed is able to compensate the deviations between the simulation and the experimental observations.