This thesis studies the aerodynamic performance and structural behaviour of propeller blades with sweep and lean, focusing on flexible designs. An extended BEM theory, corrected for sweep effects, is developed, validated against experimental data, and tightly coupled to the structural model PROTEUS to reduce computational cost. This aeroelastic coupling uses analytically derived sensitivities of the aerodynamic loads with respect to structural deformations, which are validated by comparison with numerically computed sensitivities. A parameter study is performed in which sweep and lean are systematically varied, demonstrating that structural flexibility has only a minor effect on peak aerodynamic performance compared to rigid blades. Under constant disk loading, backward sweep is found to significantly improve efficiency of flexible blades relative to the straight blade, whereas lean only has a minor influence. Structural analysis further shows that both sweep and lean increase blade stress. The root bending moment is primarily governed by lean, which implies that suitable lean distributions can be used to reduce root bending moments for a given sweep configuration.