This work introduces an enhanced cruciform specimen optimized for the mechanical characterization of fibre-reinforced composite materials subjected to a biaxial stress state (e.g. orthogonal loads). The tension-tension case, for which there is scarce published data, is specifically analyzed. First, different cruciform specimens reported in literature are modelled via finite elements to determine their stress distribution. Based on these results, as well as in existing standards and guidelines for uniaxial mechanical testing in metals and composites, an enhanced design is developed, aimed to ensure that the deformation field in its central region remains truly biaxial, thus increasing the reliability of yielded data. Future work will cover an extensive experimental program to validate this design, although early results using full-deformation strain field measurements are encouraging.