Epoxy resin is the key component in carbon-fibre-reinforced polymer (CFRP)-strengthening systems, since it starts to lose its properties when reaching its glass transition temperature (T-g), and subsequently, affects the whole system. The aim of this study is to enhance the properties of the epoxy to achieve a high-performance strengthening system. Epoxy composites were modified using the high-functionality resin N,N-diglycidyl-4-glycidyloxyaniline (DGOA). Thermal and mechanical tests were applied to investigate the effect of DGOA modification on the properties of the epoxy. The T-g of the DGOA-modified epoxy was increased by 9 degrees C, which was attributed to the higher degree of cross-linking. Moreover, it showed a considerable increase in elastic modulus and decomposition temperature. Composites were also prepared using different methods such as sonication, vibration, and post-curing. Ultrasonic-mixing was proved to improve the T-g of both neat and modified epoxy due to the more homogeneous network. Sonication also improved the tensile properties of the DGOA-modified epoxy dramatically. However, it had a negligible effect on the tensile strength of the neat epoxy and only increased the toughness. This was attributed to the lower network viscosity as a result of DGOA modification. Post-curing caused a substantial increase in the T-g by allowing the polymer to reach its maximum curing degree.