A structural health monitoring apparatus is presented. According to an embodiment, the structural health monitoring apparatus comprises: a plurality of transducers configured for coupling to a structure, the structure comprising an outer structure surrounding and coupled to an inner structure, the transducers further configured for coupling to only the outer structure so as to transmit stress waves through the inner structure, and still further configured to receive the transmitted stress waves from the outer structure after they have passed through the inner structure; and an analyzer configured to detect damage within the inner structure according to the received transmitted stress waves from the outer structure.