Piezoelectric actuation of crack growth along polymer-metal interfaces in adhesive bonds

A new experimental technique for determining mechanical properties of polym er-metal interfaces was developed by replacing the conventional mechanical testing machine with a piezoelectric actuator. The actuator was made from a thin ferroelectric ceramic beam attached to a bilayer polymer-metal compos ite specimen. The trilayer specimen was loaded by applying ac electric fiel ds on the piezoelectric actuator to drive crack growth along the polymer-me tal interface. Subcritical crack growth was observed along the epoxy/alumin um interface, and the growth rate was found to depend on the magnitude of t he applied electric field. The fracture mechanics driving force for the cra ck growth was computed from the finite element analysis as a function of cr ack length, applied field, material properties, and specimen geometry. Kine tics of the crack growth was correlated with the piezoelectric driving forc e.