Abstract: Woven or nonwoven long fiber sheets filled with two precursors each constituting an intermediate stage in a process for the preparation of a vitreous ceramic composition by the sol-gel route by hydrolysis and polycondensation using alcoholates or analogous compounds as the starting materials, that is to say an interface precursor in the form of a gel rich in water and a matrix precursor in the form of discrete particles capable of sintering at relatively low temperature, are stacked; the fibrous structure is compressed in the direction of stacking and the whole is heat-treated in order to convert the two precursors into a continuous matrix.