Micro-mechanical properties and morphological observation on fracture surfaces of carbon nanotube composites pre-treated at different temperatures

In an early stage of the decade, most of works on carbon nanotubes were centred on chemistry and physics. Due to extraordinary mechanical and thermal properties, these nanotubes have been used as nano-fibres for the improvement of the global mechanical properties of advanced composite structures. This paper reports the micro-hardness and flexural properties of nanotube/epoxy composites with different amounts of nanotubes content. Experimental measurements and microscopic observations of the composites pre-treated at different temperatures are discussed in detail. The results show that the hardness of the nanotube composites varied with different nanotube weight fractions. The flexural strength decreased by 10% for a composite beam with 2 wt.% of nanotubes. The fracture surfaces of nanotube composite were perpendicular to the nanotube pre-treated at 70 °C, and parallel to nanotubes pre-treated at -180 °C. The SEM images also revealed that all nanotubes were completely pulled out after the flexural strength test due to a weak-bonding strength between the nanotube and matrix.