Influence of hot-pressing pressure on the densification of short-carbon-fiber-reinforced, randomly oriented carbon/carbon composite

Abstract

The prime objective of this research was to study the influence of hot-pressing pressure and matrix-to-reinforcement ratio on the densification of short-carbon-fiber-reinforced, ran­domly oriented carbon/carbon-composite. Secondary objectives included determination of the physical and mechanical properties of the resulting composite. The ‘hybrid carbon-fiber-reinforced mesophase-pitch-derived carbon-matrix’ composite was fabricated by hot press­ing. During hot pressing, pressure was varied from 5 to 20 MPa, and reinforcement wt% from 30 to 70. Densification of all the compacts was carried at low impregnation pressure with phenolic resin. The effect of the impregnation cycles was determined using measure­ments of microstructure and density. The results showed that effective densification strongly depended on the hot-pressing pressure and reinforcement wt%. Furthermore, results showed that compacts processed at lower hot-pressing pressure, and at higher reinforcement wt%, gained density gradually during three densification cycles and showed the symptoms of fur­ther gains with additional densification cycles. In contrast, samples that were hot-pressed at moderate pressure and at moderate reinforcement wt%, achieved maximum density within three densification cycles. Furthermore, examination of microstructure revealed the forma­tion of cracks in samples processed at lower pressure and with low reinforcement wt%.