Joined wind turbine rotor blade with improved transition between varying material combinations

A method of joining a first blade member and a second blade member of a rotor blade of a wind turbine includes arranging the first blade member and the second blade member together at a butt joint. The first blade member and the second blade member are formed of different materials having different stiffness. The method further includes providing at least one gap at the abutment of the blade member. Further, the method includes securing the blade members together by at least partially filling the gaps with at least one filler material. Further, the method includes further securing the blade members together via an impregnation process wherein the additional filler material further fills the gap or covers at least a portion of the at least one filler material during the impregnation process. In addition, the method includes allowing the filler material (s) to cure. Thus, upon curing, the filler material (s) are configured to smoothly transition loads between the different materials of the blade member, thereby