Method of making carbon matrix composite from high temperature polymer matrix fiber-reinforced composites

A method of producing a carbon matrix composite, the method comprising:

• preparing a carbon matrix composite precursor, the carbon matrix composite precursor comprising at least one carbon-based reinforcement material and a cured thermoset polymer matrix comprising a chemical composition in accordance with Formula I
• wherein:
• m and n are each an integer greater than or equal to 1,
• at least one of R1 or R2 comprises an aromatic moiety, and
• X is selected from the group consisting of CH2, NH, O, S, SO2, and combinations thereof;
• heating the carbon matrix composite precursor to a first processing temperature, wherein:
• the first processing temperature is between 300° C. and 500° C. to form a carbon matrix composite intermediate, and
• the heating to the first processing temperature is completed in an atmosphere comprising air;
• and
• heating the carbon matrix composite intermediate to a second processing temperature and holding at the second processing temperature for at least 1 hour to form the carbon matrix composite, wherein:
• the second processing temperature is between 900° C. to 1650° C., and
• the heating to the second processing temperature and hold at the second processing temperature is completed in an inert gas environment.