u00b0 c and 330 u00b0 c and is held at that temperature for one hour by the time that the polytetrafluorethylene body 10 has reached between 290 u00b0 c and 330 u00b0 c it has of course thermally expanded further so that the pressure which it exerts upon the prepregs 11 is correspondingly greater and consolidation of the prepregs 11 is completed in addition it has softened to such an extent that it behaves as a fluid thereby providing a substantially even pressure distribution over the prepreg 11 surface which it contacts the holding of the assembly temperature for one hour additionally results in the curing of the polyimide resin in the prepregs 11 it will be understood however that the method of the present invention is not specifically restricted to thermosetting resins and that thermoplastic resins could be utilised if so desired and of course if they will withstand the high processing temperatures of the present invention up to 330 u00b0 c it will not of course by necessary with thermoplastic resins to allow time during the process to permit curing to take place after one hour at between 290 u00b0 c the temperature of the assembly is gradually reduced until its temperature has reached 60 u00b0 c the clamps 15 are then removed and the polytetrafluoroethylene body 10 which by this time has thermally contracted to a diameter less than the internal diameter of the consolidated and cured prepregs 11 is removed to leave a tube comprising reinforcing carbon filaments enclosed in a matrix of a cured polyimide resin in a variation upon the method of the present invention a polytetrafluoroethylene body 16 shown in fig2 which.