Aluminium Matrix Composite (AMC) material systems offer unique combination of material and mechanical properties as compared to conventional monolithic materials with considerable industrial application potentials. Friction stir welding (FSW) may be developed as a viable route for joining AMC materials. As a solid state thermo-mechanical joining technique, FSW process would introduce considerable amount of residual stresses in joints. The residual stresses could have a significant effect on post-weld mechanical and particularly fatigue properties. The aim of this project is to measure residual stresses in AMC joints welded under different FSW conditions, which would enable the validation of residual stresses predicted by the computational models and develop optimum FSW process conditions and operational windows for sound AMC joints.