  Topological interface states are currently attracting rapidly growing
attention in classical wave systems. However, little work has been done on
topological interface states in one-dimensional (1D) elastic wave systems,
especially in the case of oblique incidence. This paper theoretically
demonstrates the realization of topological interface states of elastic waves
in a 1D composite plate structure composed of two phononic crystals (PCs) with
different topological characteristics, which can be regulated by the incident
angle. For the out-of-plane SH mode, multiple topological interface states can
coexist in different common bandgaps. For the in-plane complex P-SV coupled
mode, topological interface states can exist in both "partial-polarization" and
"omni-polarization" bandgaps. All these interface states are in the wide
frequency and incident angle regions. We also discuss the polarization and the
mode conversion of the interface states. Our results provide an innovative
method to excite and tune topologically protected interface states for elastic
waves, which may have potential applications in obtaining strong local
vibration for different polarized elastic wave modes.
