Ultrasonic Guided Waves Generated by Parametrized Novel Mini Impactor with Application to a Composite Structure

Nondestructive structural interrogation using guided waves for damage detection is an established engineering assessment technique. In this research, a novel composite mini impactor tool is presented as an excitation source for the use in the evaluation of composite structures. Nondestructive evaluation (NDE) of aerospace composite structures is critical since non-visible internal damage, such as barely visible impact damage (BVID), can affect the safety of the structure. Traditional impact hammers have been used in NDE of composite structures, but the excitation frequency range produced is limited (less than 40 kHz). A unidirectional carbon/epoxy mini impactor device was designed to excite a frequency range between 40 and 500 kHz. Parameterization of the device was performed to define its operational domain and underlying physics. The effect of varying the mini impactor stiffness and total impactor mass, which includes an aluminum tip (i.e., tip + beam), was evaluated for time-domain features, frequency content, and amplitude ranges. During the parameterization, different waveguide materials (flat plates) were explored, which included both isotropic and anisotropic materials, thereby allowing for a mapping of structural response to the waveguide’s density, stiffness properties, and thickness. The parametrized mini impactor data were captured using piezoelectric acoustic contact sensors for structural response to the mini impactor. High-speed imagery was used to directly observe the physical motion of the mini impactor.