The outstanding properties of carbon nanotubes (CNTs) have stimulated a large number of researches to explore the potential of using them as reinforcement in polymer composites. Although many studies have reported the enlighten improvement of the materials properties by using CNTs as reinforcement, there are no promising and optimal results have been concluded to date. This thesis aims at studying the mechanical properties on thermoset polymer, Epoxy, by employing a small amount of carbon nanotubes as reinforcement. Two different types of nanotube-based composites are prepared i.e. a raw single-walled carbon nanotube (SWNT) composites and a functionalized single-walled carbon nanotube (FSWNT) composite. Chemical functionalization on SWNTs with carboxyl functional group (COOH) aims at modifying the end caps of nanotubes, so to provide covalent bonding of SWNTs to the polymer matrix during manufacturing of composite systems. Different weight percentages (wt %) of each type of SWNTs are added into the composite system. Standard test methods are performed on these nanotube composite systems and satisfactory results were achieved when the weight percentages of both types of SWNTs increased. Through the comparison between two systems (raw SWNTs and FSWNTs), the FSWNT reinforced composite is found to provide a better improvement on the mechanical properties as compared with the SWNT reinforced system. The integrity of both composite systems is examined by using Scanning Electronic Microscopy (SEM). The SEM images of the composites indicated the derivation in wetting and bonding between the nanotubes (both SWNTs and FSWNTs) and epoxy resin, and the FSWNTs provide an eminent dispersion when compared with the SWNTs in the composite system. Moreover, thermal testings are employed to further investigate the interfacial interaction between the nanotubes and the polymer matrix. xiv Molecular Dynamics (MD) simulations are also carried out to investigate the structural change of a SWNT under different temperature-controlled manufacturing environments. Swivel of the SWNT was noticed as the temperature increased. Such alteration in structure form can provide physical interlocking between SWNT and its surrounding polymer system. Thus, its overall mechanical and thermal properties can be enhanced.