Patent ID: 7276203

Claim:
A process for producing hollow bodies comprising fiber-reinforced ceramic materials, which comprises in a first step, producing compressible cores whose shape corresponds, at least in the plane perpendicular to the pressing direction, essentially to the geometry of the hollow spaces to be formed, in a second step producing a green body by introducing the said compressible cores and a mouldable composition comprising binder and fiber material into a mould, in a third step, pressing the composition containing fiber material with a pressure of from 0.1 MPa to 50 MPa so that the core is compressed in the pressing direction by at least 5% of its dimension in the pressing direction, which cores have at least three layers in the pressing direction of the third step, where the compressibility of directly adjacent layers differs for these said layers, and the compressibility of, the outermost layer is at least twice that of the inner layer, wherein the outer layers are made of foamed polymers and wherein the inner layer is made of thermoplastic materials which thermoplastic materials have a heat distortion temperature of at least 150° C., and a ball indentation hardness of at least 30 MPa, the thickness of the outer layers being from 10% to 40% of the total thickness of the core in the pressing direction for each of the outer layers, and from 20% to 80% of the total thickness in the pressing direction for the inner layer, in a fourth step, curing the composition comprising fiber material to form a cured green body, in a fifth step carbonizing the cured green body by heating to a temperature of from about 750° C. to about 1100° C. in a nonoxidizing atmosphere to produce a C/C body, where the cores consist of material which pyrolyses in the fifth step or is at least partially pyrolysed with volume shrinkage, wherein during pressing, the outer layers are compressed to from 1/10 to 1/200 of their original thickness.