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

A new experimental technique for determining mechanical properties of polymer–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 composite specimen. The trilayer specimen was loaded by applying ac electric fields on the piezoelectric actuator to drive crack growth along the polymer-metal interface. Subcritical crack growth was observed along the epoxy/aluminum interface, and the growth rate was found to depend on the magnitude of the applied electric field. The fracture mechanics driving force for the crack growth was computed from the finite element analysis as a function of crack length, applied field, material properties, and specimen geometry. Kinetics of the crack growth was correlated with the piezoelectric driving force.