Mechanical properties enhancement of polymeric nanocomposites reinforced with covalently functionalized helical carbon nanotubes using acidic mixtures

Abstract

Polymer-based composites are widely used for structural applications, predominantly in the aerospace, space, sporting gears, and renewable energy industries. Despite having superior properties over metals, polymeric composites with macro-scaled fibers as reinforcement have several current unsolved issues. One of the main disadvantages is their failure/delamination due to interlaminar or out-of-plane stresses, which is mainly due to lack of reinforcement in the transverse or thickness direction. A few methods to provide reinforcement in the transverse direction in traditional composites are available; however, these methods have proven to be less effective and degrade the existing laminate properties. The latest cutting-edge and most-promising reinforcement method is to use nanomaterials such as carbon nanotubes (CNTs). Graphene is the thinnest and strongest material known to humans, and when it is rolled into a tubular structure to form CNTs, its properties are far superior to carbon fibers. However, CNTs are not used in major structural applications since they are a relatively new material. Because CNTs are inert in nature, it is necessary to functionalize them before incorporating them into polymers. CNTs can be functionalized using different chemicals, which will improve their interaction with and dispersion in polymers. Many factors influence polymeric nanocomposites that are reinforced with CNTs, including the CNT geometry, CNT weight percentage in polymers, CNT configuration, functionalization process, and curing cycle. In this research, helical carbon nanotubes (HCNTs) were functionalized using mixtures of nitric, sulfuric, and hydrochloric acids following 16 different procedures in order to study their effects on mechanical properties of HCNTs reinforced polymeric nanocomposites. The main objective here was to investigate the tensile strength, fracture toughness, Young's modulus, and strain at failure results, employing 3 different weight percentages of the functionalized HCNTs and identify the best functionalization processes.