Statistical approach to evaluating active reduction of crack propagation in aluminumpanels with piezoelectric actuator patches

Abstract

Fatigue cracks in light-weight shell or panel structures may lead to major failures whenused for sealing or load-carrying purposes. This paper describes investigations into thepotential of piezoelectric actuator patches that are applied to the surface of an alreadycracked thin aluminum panel to actively reduce the propagation of fatigue cracks. Withactive reduction of fatigue crack propagation, uncertainties in the cracked structure’sstrength, which always remain present even when the structure is used underdamage tolerance conditions, e.g. airplane fuselages, could be lowered. The mainidea is to lower the cyclic stress intensity factor near the crack tip with activelyinduced mechanical compression forces using thin low voltage piezoelectric actuatorpatches applied to the panel’s surface. With lowering of the cyclic stress intensity,the rate of crack propagation in an already cracked thin aluminum panel willbe reduced significantly. First, this paper discusses the proper placement andalignment of thin piezoelectric actuator patches near the crack tip to induce themechanical compression forces necessary for reduction of crack propagation bynumerical simulations. Second, the potential for crack propagation reductionwill be investigated statistically by an experimental sample test examining threecases: a cracked aluminum host structure (i) without, (ii) with but passive, and(iii) with activated piezoelectric actuator patches. It will be seen that activatedpiezoelectric actuator patches lead to a significant reduction in crack propagation.