Abstract: A manufacturing process of a large part of composite materials with a high fiber content (more than 58%) using the resin transfer moulding technique, wherein a fiber pellet (26) is placed in a mould (20) and strongly compressed, whilst the resin is injected at a constant reference flow rate value and while the instantaneous pressure at the mould inlet is lower than a reference pressure value. When this reference pressure value is reached, the injection flow rate is reduced to maintain the pressure at this level, and the compression of the pellet (26) is temporarily reduced. The injection flow rate is then altered to the constant reference flow rate value and the compression is increased, to start another cycle.