Mechanical Characterization of XD-Grade Carbon Nanotube/Epon 862 Processed by Dual Phase Dispersion Technique

Uniform dispersion of the constituent nanomaterial is essential in attaining optimal results for nanocomposite fabrication. In this research, a dual-phase dispersion method is studied combining a high intensity ultrasonic liquid processor with a three roll milling technique. XD-grade carbon nanotubes (XD-CNTs) were infused into Epon 862 epoxy and the mixture was then mechanically mixed with a mechanical stirrer before placing into a sonicator. This mixture was submerged continuously in a cooling bath to prevent premature polymerization. Once the sonication cycle was completed, the mixture was then placed in a three roll milling processor for six successive cycles incrementally reduced from 20 to 5 μm gap spacings at 140 rpm. Epikure curing agent W was then added to the modified resin and mixed using a high-speed mechanical stirrer. To reduce the chance of void formation, the mixture was preheated and placed in a vacuum oven to remove trapped air and reaction volatiles. Flexural and dynamic mechanical analysis (DMA) tests were performed on neat, 0.015 wt. %, and 0.15 wt. % xd-CNT/epoxy plaques to identify the loading effect on the mechanical properties of the composite material. Flexural results indicated homogeneity with improvements in mechanical properties of up to 15% in strength as well as modulus enhancement of up to 25%, respectively. Interfacial adhesion and dispersion were improved with viscosity reduction while utilizing the secondary mixing method. DMA tests resulted in an increase in storage modulus in the nanophased specimens as CNT loading increased. This is mainly attributed to enhanced CNT dispersion and distribution causing reduced polymer chain movement and increased stiffness. Scanning electron microscopy (SEM) revealed the fracture morphology of the tested specimens indicating proper dispersion of the xd-CNTs by fracture propagation and cleavage plane displacement.