Permeability measurements and flow simulation for polyaniline carbon nanofibers modified nanopaper on glass fiber preform

Carbon nanofibers (CNFs) nanopapers have shown great potential to improve the surface of fiber-reinforced polymeric composites, including providing electromagnetic interference shielding and erosion resistance. During typical resin transfer molding (RTM) process, the CNF nanopaper is incorporated into the fiber preform as a surface layer. To learn how resin flows through the fiber preform and nanopaper layer, permeabilities of the fiber preform and nanopaper need to be measured. As is well known, measuring the permeability of fiber preforms is experimentally challenging. Results usually exhibit large experimental variability. Measuring permeability of nanopapers is even more complicated. To improve the accuracy of results, permeability of CNF-based nanopapers was measured using different experimental setups. In-plane permeability of nanopaper was measured by both unidirectional microslit flow and radial flow approaches. Trans-plane permeability was measured as well, using a trans-plane flow cell and a flow visualization mold. In this article, we discuss the methods used and provide experimental results. We also conducted computational fluid dynamics simulations to study the detailed flow patterns of the nanopaper/RTM process and compared the simulated effect of the nanopaper on retarding the flow (length of the lag) with respect to the glass preform with flow visualization results. POLYM. COMPOS., 37:435-445, 2016.