Evaluation of film-substrate adhesion via impact using coated bullets

A method was devised to evaluate the adhesion between a film and a substrate.\nA front-end coated bullet is accelerated by a gas gun and hits the substrate of\nthe specimen under test. The impact generates a compressive stress pulse that\npropagates toward the film. After transmission through the interface, part of the\npulse is reflected on the free surface of the film, and tensile stress arises at the\nfilm-substrate interface, possibly inducing debonding of the film.\nThis dynamic process was demonstrated analytically and simulated numerically\nby the finite element method. The results validate the initial concept and lay the\nfoundation for further optimization of this method.