The results of in-situ cyclic tensile experiments performed on two dogbone specimens made of glass fiber mat reinforced polyester resin are presented (the second specimen contains a machined rectangular notch). The experimental data were obtained by using X-Ray Computed Tomography. The reconstructed volumes were analyzed via Digital Volume Correlation. The investigated material was notch-insensitive since both specimens failed at equal stress levels. To further confirm this hypothesis, and to study strain-damage interactions, the major eigen strain and correlation residual maps of both specimens were analyzed. Even in the first loading cycle, an inner strained band extending through the whole ligament area developed within both specimens, already indicating the path to final fracture. It is shown that the final failure of the studied material was primarily driven by the yarn mesostructure, i.e., the influence of the underlying heterogeneities prevailed over the effects due to specimen machining and/or geometric singularity.