Investigation of elastic wave transmission in a metaconcrete slab

Abstract

A new type of modified concrete, termed metaconcrete, has been shown to exhibit trapping of wave energy and a reduction in mortar stress when subjected to dynamic loading. Metaconcrete replaces the standard stone and gravel aggregates of regular concrete with spherical inclusions consisting of a heavy core coated with a compliant outer layer. These new layered aggregates resonate at designed frequencies by allowing for relative motion between the heavy core and the mortar matrix, which causes the aggregate to absorb energy and therefore reduce stress within the mortar phase of the composite material. The transmission of wave energy through a metaconcrete slab can be used to visualize the effect of resonant behavior within the metaconcrete aggregates. To quantify this behavior we compute a transmission coefficient, which is a method of measuring the absorption of wave energy as an applied forcing of known frequency travels through the material. The transmission coefficient is plotted against forcing frequency for four different aggregate material and geometry configurations. A reduction in transmission ratio is observed at or near the computed natural modes of the aggregate, indicating the activation of resonance within the inclusions. This behavior is consistent with observations from studies on sonic metamaterials containing resonant inclusions with a similar layered structure. The frequency location and width of the dip in transmission coefficient will aid in the design of metaconcrete aggregates for specific forcing applications.