On elastodynamics of biperiodic composite media

The aim of this paper is twofold. First, we formulate a mathematical model for the analysis of waves propagating in a linear-elastic composite, which in every plane normal to a certain straight line has an identical periodic structure. Second, we apply the derived model equations to the investigations of waves propagating across a laminated medium with periodically folded laminae. Lower and higher propagation speeds for the longitudinal and transversal waves are calculated and for the long waves represented in the form of simple asymptotic formulas.