Simulating the dynamic behaviour of heterogeneous finite-element structures such as electric motors often requires to homogenise the models in the first place. Current homogenisation methods do not always imply computing an equivalent homogeneous material's elasticity matrix and are often restrained to specific uses. In this document, a novel approach of equivalent material identification is developed for multi-layered orthotropic structures. A finite-element model of a 3D stratified structure is created, as well as its equivalent homogeneous medium. The dynamic behaviour of the homogeneous structure with the equivalent material identified by the new method is compared at low frequencies to the reference stack and to equivalent materials created using other existing homogenisation techniques. It is shown that this approach is more accurate than existing reference homogenisation methods. Applied to the magnetic core's finite-element model of a real laminated electric machine stator, the method enables simulating the experimental behaviour with good accuracy, without need of time-consuming model updating procedures.