• Hafiychuk, Vasyl
• Walker, James
• Smelyanskiy, Vadim
• Tyson, Richard
• Luchinsky, Dmitry

Abstract

<p>Composite sandwich structures are candidates for use in a variety of launch vehicle designs, including the heavy lift ones; however, they present challenges for structural health monitoring (SHM). The goal of the SHM methods under development is to increase safety and reduce maintenance cost of space vehicle structural health. It consists of the implementation of a number of sensors that can measure strain, vibration and ultrasonic waves to determine debonds, delaminations and other flaws, as well as loads and impacts. Monitoring methods based on guided-wave approaches have shown promise in enabling wide-area SHM for thick (about 1-2in) composite sandwich structures. This presentation reports on analytical as well as experimental investigation of acoustic waves propagating in sandwich type composite structures of the size four feet by four feet with the intention of using the obtained robust modeling and experimental data results for structural health monitoring (SHM) systems for these materials in a large area coverage and in complex geometry areas. To understand fundamental properties of the SHM and limitations that may affect the application of current SHM sensors and methods we performed simulations and experimental verifications of wave propagations and scattering for honeycomb composite sandwich structures of 1 1/2 in core thickness. The Finite Element model developed for computer simulation of wave propagation in the sandwich panel takes into account the real structure of honeycomb cells, interface fill up layers, and two facesheets with mounted PZT actuators and sensors. The transient wave propagation and scattering were studied for a set of panels controlled impacts to determine the sensitivity of the SHM method. Mounted to the surface, PZT actuators and sensors were used to study wave propagation in sandwich panels and the electrical signal on the sensors was analyzed and compared with experimental signals. Then, the damage of the impact was simulated to obtain the fault with parameters close to the damage we have in the experiment. The theoretical results obtained by the simulation came out to agree well with the experimental results. The analytical model is developed in framework of the Mindlin plate theory approach and the results of wave propagation and scattering are fitted to the experimental and FE modeling. It is concluded that a combination of analytical results and high-fidelity simulations makes it possible to analyze experimental data and predict the applicability of SHM methods for this type of structure. The obtained results open up the prospect of the development of the SHM methods for advanced composite panels. This study makes it possible to deeply understand the physics based processes for the development of SHM methods.</p>

Topics

• impedance spectroscopy
• surface
• theory
• experiment
• simulation
• composite
• ultrasonic