An inertia weight assembly positionable within a receiving portion of a rotor blade for use on a rotorcraft. The inertia weight assembly includes a weighted core and a casing having a closed outboard end and forming a cavity. The weighted core is disposed in the cavity such that the casing at least partially encloses the weighted core. The weighted core is formed from a first material and the casing is formed from a second material that is dissimilar to the first material. The casing provides an interface between the weighted core and the receiving portion of the rotor blade. The second material is more bondable to the receiving portion of the rotor blade than the first material.