This paper proposes a new method using substructure potential energy, which is capable of accurately estimating the
damage magnitude of multiple members, and particularly advantageous for sandwich panels with lattice cores. While
other existing damage severity estimation methods require the information of several modes of the whole structure, the
new method utilizes only a small number of measurement locations for sandwich structure. The performance of the
proposed method is compared with existing damage detection methods using a set of numerical simulations that are
demonstrated for a sandwich panel based on synthetic data generated from finite element models.