Material and Mechanical Characterization of Multi-Functional Carbon Nanotube Reinforced Hybrid Composite Materials

Abstract

Fiber reinforced polymer (FRP) composite structures are widely being used in aircraft wings, wind turbine blades, helicopter rotor blades and tail rotors. These structures are often exposed to external dynamic loads which shorten their lifetime. Carbon nanotubes (CNT) reinforced epoxy resin have distinctive characteristic in providing a significant increase in mechanical properties and stiffness of the FRP composite. The present study investigates the micro, macro and structural analysis of composites with and without reinforcement of multi walled carbon nanotubes (MWCNT). The carboxylic acid (COOH) functionalized MWCNT with more than 95% chemical purity having average dimensions of 17 nm outer diameter and 10 μm length were used to characterize their chemical properties and evaluate the mechanical and free and forced vibration response of composites with and without MWCNT reinforcement. Initially, the powder form of the MWCNT was taken for the identification of true density (ρ) using the gas displacement technique. The COOH-MWCNT were then randomly dispersed in low viscosity epoxy resin (LY556) through an organic solvent using the ultrasonic liquid processor. Test samples were fabricated by adding the hardener (HY951) at 10:1 ratio in the sonicated solution to obtain the Young’s Modulus (E) of MWCNT using Nano Indentation. Following this, Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Fourier Transform Infrared spectroscopy (FT-IR), Thermo gravimetric analysis (TGA) were also used to quantify the dispersion, distribution, structural integrity, aspect ratio, functional group and purity level of nanotubes. Further, the impact hammer test based on ASTM E1876, tensile test based on ASTM D3039 and free and forced vibration analysis of the hybrid composite beams were carried out to identify the elastic properties, fundamental natural frequencies, damping ratio and transverse deflection of the hybrid structure. It was shown that the addition of 1 wt% of COOH-MWCNT in fiber reinforced composite beam increases the stiffness of the structure and consequently increases the natural frequencies and damping at each resonant response dominant peaks. The strong adhesion of bonding and proper dispersion of CNTs in the wide surface area of composite strengthen the polymer composites substantially than those of the Glass/epoxy composite structures without reinforcement of MWCNT.