Mechanical Properties of Infusion-Processed Fiber Reinforced Plastics with In Situ-Grown Aligned Carbon Nanotubes

Abstract

Fiber-reinforced plastic laminates containing aligned carbon nanotubes (CNTs) are manufactured by vacuum-assisted resin infusion processing, building on prior extensive work with a hand lay-up process. Three-dimensional reinforcement of the laminates is achieved using long (>10 �m) CNTs in both the interlaminar and intralaminar regions. Radially-aligned CNTs were grown in situ on the surface of alumina fibers in woven fabrics by chemical vapor deposition (CVD), creating a nanoscale, fiber (FF) hierarchical architecture. The multi-scale (nm andm diameter fibers) fiber dry forms are infused using an aerospace standard infusion resin with no modification to the processing or resin. Optical and scanning electron microscope images of composites cross sections confirmed ~0.1% void fraction, and that the CNTs retain alignment and remain on the surface of the fibers after the infusion process. Flexure tests of the fuzzy fiber composites show that in-plane properties (bending modulus and strength) are retained. Combined with prior work on such laminates, these results indicate that the aligned CNTs can provide significant interlaminar toughness enhancement without degrading in-plane laminate properties. This finding is in contrast to typical z-direction laminate reinforcement techniques such as stitching and z-pinning that substantially degrade in- plane properties to achieve interlaminar reinforcement. Additionally, electrical properties of the infusion-processed laminates reveal conductivity enhancement of greater than 10 6 times from the incorporation of ~1% volume fraction of CNTs. The processing demonstrated shows that infusion is a viable fabrication route for new CNT-enhanced composite materials containing aligned CNTs with improved mechanical and multifunctional performance.