FABRICATION AND CHARACTERIZATION OF CARBON NANOTUBE/POLY(METHYL METHACRYLATE) NANOCOMPOSITE LAMINATES

Abstract

Aligned carbon nanotubes (A-CNTs) are advantageous reinforcements for polymer nanocomposites (PNCs) due to their high mass-specific physical properties, including strength, elastic modulus, thermal conductivity, and electrical conductivity, which create potential applications in both structural reinforcement and multifunctionality. To utilize these properties, the CNTs should be aligned and densely packed within the polymer matrix, similar to existing carbon microfiber composites. However, past methods to fabricate CNT-reinforced PNCs have focused on random dispersion of the nanofibers, resulting in uneven distribution and low packing density. As such, it has been difficult to fully realize the benefits of reinforcing PNCs with A-CNTs. In more recent work, the high volume fraction bulk nanocomposite laminating (BNL) process with A-CNTs has been demonstrated. PNC laminates containing uniform, aligned and highly-dense CNTs at unprecedented high volume fractions (> 50 vol%) using the aerospace-grade thermoset bismaleimide (BMI) polymer have been successfully manufactured. In this work, the BNL fabrication technique is applied to the manufacturing of the first high volume fraction aligned-CNT BNL with a thermoplastic matrix, namely poly(methyl methacrylate) (PMMA). Composites with thermoplastic matrices are used extensively in aerospace and civil structures due to their rapid processing, high ductility, improved recyclability and repairability. It is shown in this study that PMMA-matrix BNL with a high packing density and a void-free morphology have been successfully fabricated, based on assessment using micro-computed tomography (μCT). Crystallinity and glass transition temperature (Tg) are shown to be largely unaffected by the aligned CNTs using DSC. With the high specific strength, rapid manufacturing process, and multifunctionality of aligned CNTs, the thermoplastic PMMA BNL has the potential to replace conventional materials in additive manufacturing and electronic applications.