This project is focused on studying the effects of particles for improving mechanical and thermal properties of glass fiber reinforced epoxy composite. Submicro and nanosized particle filled composites based on diglycidyl-ether of bisphenol A and anhydride-curing agents are evaluated. The particles examined in this report are Particle 1 (P1 – 700nm) supplied in powder: Particle 3 (P3 – 100nm), Particle 2 (P2 – 70nm), and Particle 4 (P4 – 45nm) supplied in masterbatches. These particles have been successfully used in laminates with clean woven E-glass fabric produced by vacuum assisted resin transfer molding (VARTM). Optical microscope and scanning electron microscope is used to observe the particles and the composites. Laminates of unfilled resin and unidirectional unwashed glass fabric are manufactured by wet lay. When the particles or the masterbatch are mixed with the epoxy resin, the viscosity is increased significantly. Dynamic mechanical analyses of the epoxy and nanocomposite plates and their corresponding laminates show an increase of the storage modulus with the addition of particles, especially beyond Tg. The relative permittivity was always higher than the reference epoxy for the filled resins and more especially for laminates at 40°C. The laminates with 30vol% atlas 1/7 clean glass fabrics exhibit better results than the non-clean E-glass fabric. The dielectric dissipation factor was lower for the laminates with 30vol% clean glass fabric than for the matrix only, the laminates with 30vol% of ML clean fabric and atlas 1/7 normal fabric. The flexural strength is measured, and the most interesting results were found for the laminates with 30vol% atlas clean glass fabrics with 35,3wt% P3 particles in epoxy and with reference epoxy. Concerning the flexural strength of the matrices, the most interesting were found to be 143MPa for the epoxy filled with 12,6wt% P4 particles (45nm). Electrical breakdown setup was built to test flat laminate of 4mm in a SF6 gas chamber. Three types of samples were tested, samples with only matrix of the reference epoxy, samples with P3 particles filled epoxy plate and laminate of reference epoxy with 30vol% of clean atlas glass fabric. Particles 5 (P5 – 15/30nm) supplied in masterbatch are also introduced in this project but the mixing is revealed to be more difficult than with the previous masterbatches and no more work was carried out at this stage.