This article studies the mechanical behaviour of E-glass/epoxy composites fabricated with a vacuum infusion process. An experimental characterization of the in-plane lamina properties has been conducted based on the recommendations found on the literature and ASTM standards. The properties were determined by tensile, three rail shear and flexure tests. The main focus is the evaluation of these tests for mechanical material characterization. In the computation of the elastic modulus using the chord and secant method for longitudinal (E-1) and transverse (E-2) modulus a relative error of 5% and 6.5% is found respectively. In addition, comparing the +/- 45 degrees tensile test and three rail shear test for in-plane shear characterization, a relative error of 2.5% for the elastic shear modulus (G(12)) and 37% for the ultimate shear stress is found. Shear tests put on evidence the lack of linearity on the stress - strain relation.