Effect of various methods of pre-treatment of carbon fibers on the mechanical properties of PIP-based ceramics/carbon composites

The purpose of this study was to establish the conditions of CF surface preparation suitable for obtaining composites with favorable mechanical properties. The relationships between the interfacial properties of the carbon fiber/polymethylsiloxane composites and mechanical properties of ceramic composites (CF/SiOC, CF/SiC) formed during heat-treatment (HT) up to 1700℃ were investigated. The CF-resin interfacial strength has been modified by fiber surface treatment including nitric acid oxidation, silanization, as well as by forming a coating on the CF surface by depositing CNT or a pyrolytic carbon layer (PyC). The study of composite interphases (Interlaminar Shear Strength, ILSS and SEM) and surface tests of the modified CF (XPS, FT-IR, wettability measurements) showed different nature of the bonding between CFs and the resin matrix before and after HT. The CF silanization promoting chemical interfacial interactions significantly improved the ILSS between CFs and resin by 38.5%, while reduced mechanical properties of resulting ceramic composites. The most promising surface treatment method of CF for PIP-based ceramic composites was modification with PyC layer, which provided 2 times higher ILSS, 1.5 times higher flexural strength and improved work to fracture (WF) as compared to unmodified CF.