Reinforcement of C/C materials prepregs with pyrocarbon coated carbon fiber as the way to improve the prepregs properties after pyrolysis

C/C materials represent as materials with specific performance, therefore they are applied in various industries. It is essential to figure out the paths to predict, to provide and to enhance their properties to obtain high performance products. It is well known that strong matrix/reinforcer adhesion provides better strength utilization and therefore better properties for the majority of composite materials of all types (Heim in Compos Part B Eng 54:365–370, 2013), (Hancock and Cuthbertson in J Mater Sci 5:762–768, 1970), (Yang et al. in Polymers 13:2764, 2021). However some researchers note that strong adhesion in the materials that are exposed to high temperatures leads to cracking and significant properties degradation (Vignoles et al. in The Control of interphases in carbon and ceramic matrix composites, Wiley, Hoboken, 2012), (Zhang et al. in Compos Struct 340, 2024). In this work, the effect of the pyrocarbon layer applied on the surface of carbon fibers used for reinforcement of formaldehyde novolac resin based carbon/carbon (C/C) material prepregs was investigated. For the first time we used this effect to prove that lower matrix/reinforcer adhesion in C/C materials prepregs leads to better material behavior during pyrolysis, which results in higher mechanical properties of the pyrolised samples in comparison with the samples demonstrating stronger matrix/reinforcer adhesion. The prepregs were thermally treated at various temperatures, the physical and mechanical performance evolution of the prepregs at different carbonization stages were analyzed. Comparative study of the features of the prepregs with pyrocarbon coated and uncoated carbon fiber as a reinforcement were carried out. The damping effect of the pyrocarbon on the fiber surface were advertised, allowing to mitigate the carbonization-caused effects. The prepregs reinforced with pyrocarbon-modified carbon fibers demonstrated lower cracking performance and higher mechanical performance comparing with the uncoated fiber reinforced prepregs.