Out of Autoclave Manufacturing of Void-free Woven Aerospace-grade Carbon Fiber Reinforced Plastic Composite Laminates Using Capillary Effects of Aerogel Nanoporous Networks

Abstract

Manufacturing of aerospace-grade composite structures generally requires the use of autoclaves which provide the convective heating for laminate curing and the pressure for void removal. However, the autoclave also imposes high equipment and energy costs as well as geometry constraints on the manufactured composite parts. Instead of using an autoclave, the external pressure of an autoclave required for void removal during composite manufacturing can be replaced by the capillary pressure induced by nanoporous network (NPN) materials, including vertically aligned carbon nanotube (VA-CNT) arrays, and here, a polymer aerogel. In this work, we demonstrated for the first time the manufacturing of void-free autoclave-grade aerospace carbon fiber reinforced plastic (CFRP) woven composite laminates by placing polyimide (PI) aerogel films as an NPN layer at the ply-ply interface. Preliminary microstructure inspection reveals void-free laminates, which in past work with unidirectional (UD) CFRP and VA-CNTs, was directly correlated with maintaining mechanical properties. Key characteristics including achievable capillary pressure and permeability for the PI aerogel NPN material were characterized using a gas-liquid porometer to advance the understanding of the capillary-induced resin wetting mechanism. In addition, a preliminary theoretical model which considers various characteristics of the NPN materials was elucidated. Together with the experimental investigation, the theoretical model will be used to guide material selection and expand the options of NPN materials that can enable out-of-autoclave (OoA) manufacturing of aerospace-grade composite components.