Carbon nanotube yarn and 3-D braid composites. Part I: Tensile testing and mechanical properties analysis

Macroscopic textile preforms were produced with a multi-level hierarchical carbon nanotube (CNT) structure: nanotubes, bundles, spun single yarns, plied yarns and 3-D braids. The 3-D braided preform was the first of its kind produced by textile processing technique and used as a composite reinforcement consisting solely of carbon nanotubes. Four different epoxy systems that possessed a wide range of mechanical properties (owed to an added modifier) were infused into the CNT yarns and 3-D braids. Mechanical characterization of the resulting composites was conducted through the use of tensile testing. It was found that the tensile strength, stiffness and, especially, strain-to-failure values for each preform type were close regardless of the properties of the matrix whose strain-to-failure values ranged from 3.6% to 89%. This is hypothetically attributed to the nano-scale interaction between individual nanotubes and polymeric macromolecules in the composites. This hypothesis is validated by the Dynamic Mechanical Analysis results in Part II. (C) 2009 Elsevier Ltd. All rights reserved.