This project contains design, testing and simulation of a GFRP cruciform specimen subjected to biaxial fatigue. A study of state-of-the-art literature is conducted, where previous designs of cruciform specimens subjected to biaxial fatigue are studied. A specimen geometry and lay-up optimization is conducted in MATLAB which interacts with a solid FE model in ANSYS, wherein a gauge zone is embedded into the specimen with a predefined lay-up, specified by Siemens Wind Power A/S. Designed specimens are tested in biaxial fatigue at different stress levels until failure occurs in the gauge zone. Video camera, DIC and strain gauges are utilized to monitor failure during the fatigue tests. A state-of-the-art fatigue life prediction algorithm, called FADAS, is implemented into an ANSYS programmable subroutine. The algorithm involves a progressive strength degradation, Puck’s failure criteria and a stiffness degradation in order to estimate fatigue life of FRP. FADAS is utilized on an FE shell model of the designed specimen. Simulations of the fatigue test are conducted in order to verify if the FADAS algorithm can predict the fatigue life of these. It is concluded that this version of the implemented FADAS algorithm can not estimate fatigue life within an acceptable tolerance.