Scale-up Study and Demonstration of Highly Aligned and High Concentration CNT Reinforced Composites for Aerospace Applications

Abstract

The objective of this research is to design, fabricate, and demonstrate scalable manufacturing processes, aerospace-quality and advanced structural and multifunctional properties of nanocomposites using commercially available carbon nanotube (CNT) yarns and sheets and aerospace qualified resin matrix. The goal is to achieve extra-high modulus, and adequate interfacial shear property with scale-up sample sizes (4"×4"×0.1"). Different from current low CNT content (<5 wt%) composites and micrometer-scale sample size efforts, we will study and demonstrate effective approaches to manufacture aerospace-quality structural composite materials of ~60 wt% CNT concentration and achieve sizable demonstration samples with a high degree of alignment and packing for potential structural applications. We have developed a unique manufacturing process to produce highly aligned, and high concentration CNT yarn composites by stretch-assist CNT filament winding, heatassisted multiple-step stretching and curing under tension processes, which are potentially easy to scale-up and are low cost with utilization of commercially available CNT materials. CNT purification was also performed to eliminate residual catalyst and amorphous carbon and to facilitate the removal of manufacturing added chemicals during CNT synthesis. CNT surface treatment, such as chemical functionalization and plasma etching were further studied to improve the CNT and resin interfacial bonding. Cytec 5250-4 BMI resin and an autoclave process were used to produce the large size test panels. Tensile testing and three-point bending tests were conducted, as well as SEM failure analysis. This is the first attempt to scale-up manufacturing of high CNT loading and alignment test panels and conduct ASTM standard level tests.