Optimizing electromechanical coupling in piezocomposites using polymers with negative Poisson´s ratio

The invention of methods to make new materials with an engineered microstructure that yields a negative Poisson ratio opens a new avenue to optimize the performance of piezoelectric-rod/polymer-matrix composites. Such negative Poisson´s ratio materials can be used as the passive phase in the composite to redirect the external stress acting on the piezocomposite so that the resulting stress bearing on the piezoceramic rods produces a maximal piezoelectric response. To project the properties of such a piezocomposite, a simple physical model that assumes constant strain along the rods and constant stress in the perpendicular plane is used. Interesting opportunities to improve the performance of devices made from 1-3 piezocomposites are seen in results calculated for the thickness-mode electromechanical coupling constant relevant to pulse-echo ultrasonic applications and for the hydrostatic electromechanical coupling constant relevant to passive hydrophones