Carbon-fiber-reinforced carbon composites fabricated with mesophase pitch

Abstract

This study is concerned with the production of carbon-fiber-reinforced carbon with polyaromatic mesophase as matrix precursor. Carbon fibers from several manufacturers and with specific surface treatments were infiltrated at various pressures and temperatures using pitches with mesophase contents from 15 to 75 vol%. The resulting matrix shows a significantly increased mesophase content of about 80 vol% even if a starting pitch with only 40 vol% mesophase is used. Carbonization of composites without swelling was only possible after a well defined stabilization treatment of the green composites in oxygen. Mechanical testing of the carbonized composites (1000°C) showed four modes of failure behaviour, depending on the surface treatment of the carbon fibers and the stabilization treatment of the matrix. After a graphitization treatment at 2100°C, flexural strengths up to 650 MPa were found; a composite made of surface-activated fibers and a stabilized matrix displayed the greatest strength.