Manufacturing Process of CNT/BMI Composites and CF/CNT Hybrid Composites with Continuously-spun CNT Prepregs Synthesized by FCCVCD

The Floating Catalyst Chemical Vapor Deposition (FCCVD) method has attracted extensive research interests from both academia and industry due to its high potential for carbon nanotube (CNT) mass production. As aerospace aims become increasingly demanding, there is an ever growing need for mass producing lightweight structural composites. By infiltrating bismaleimide (BMI) resin and curing under pressure, CNT/BMI nanocomposites with high CNT loading are exhibiting excellent mechanical properties. By further integrating CNT into carbon fiber (CF), the mechanical and electrical improvements in axial, transverse and through-thickness direction demonstrate potential for multifunctional applications. In this work, a FCCVD reactor designed and assembled at the High-Performance Materials Institute was used for CNT synthesis. The CNT aerogel formed was continuously spun onto a rotating mandrel while continuously spraying a BMI/acetone solution, forming an ultra-thin prepreg material ranging from 1-5 μm in thickness. The quality of the CNTs collected was characterized using Raman Spectroscopy, Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), and Transmission Electron Microscopy (TEM). To evaluate the ultra-thin FCCVD-CNT prepregs, six layers were stacked in the same alignment direction, and cured using a vacuum-assisted bagging system and hot press. Electrical conductivity tests were conducted in both the aligned and the transverse directions. Furthermore, the ultra-thin CNT prepregs were integrated into the aerospace-grade unidirectional IM7/CYCOM® 5250-4 prepregs following an alternating order. The assembly was finally vacuum-bagged to expel air and cured with a hot press. The microstructure and interface of CF/CNT hybrid composites and CNT/BMI composites were observed under SEM. This paper reports on a fabrication process of CNT prepregs, which could be potentially used to scale-up the CNT/BMI composites and CF/CNT interply hybrid composites manufacturing.