densified piece to be obtained the thickness of the walls is determined by the number of folds constituting it this thickness is given by the following formula equ1 in which e is the final thickness of the wall mv the density of the fiber v f the fiber volume percentage in the final material ms the surface mass of a dry fold and n the number of folds by way of example for n 1 mv 2 55 10 3 kg m3 ms 0 443 kg m2 v f 0 43 e is 0 4 10 3 m so as to embody a piece as shown on fig1 a layer of impregnated folds 3 is placed at the bottom of the mould 2 and then two inserts 5 are disposed above the impregnated material with their points directed upward then the slanted upper walls of the inserts are coated with a layer of impregnated folds prior to placing three inserts 5 with their points directed downward and which are placed inside recesses provided by the first two inserts finally the unit is coated with an upper layer 4 of impregnated folds the layers 3 and 4 forming the lower and upper skins of the piece the inserts 5 correspond to the hollow zones of the final piece the material of the inserts is selected by taking into account the stresses involved in implementing the composites to be embodied namely pressure temperature and atmosphere in the case of a vitreous mould composite material produced under a neutral atmosphere at a low pressing pressure it is possible to use a high performing.