Results of modeling of the wave propagation, impact, and damage detection in a sandwich honeycomb plate using piezoelectric actuator/sensor scheme are reported. A finite element model of honeycomb sandwich panel that reproduces accurately experimental setup and takes into account main characteristic features of the real composite panel, impactor, lead zirconate titanate actuator, and sensors is developed. The impact is simulated to obtain damage with parameters close to those observed in the experiment. Both in simulations and in experiment, the voltage signal of a given shape is applied to the lead zirconate titanate actuators to excite acoustic wave, and the electrical signals collected from the lead zirconate titanate sensors mounted to the panel are used to study wave propagation in the sandwich panel. The results of simulation are shown to be in good agreement with the experimental results both before and after the impact. Properties of acoustic wave propagating in composite sandwich honeycomb panels are discussed.

Large and complex deep space platforms such as the Deep Space Habitat (DSH) being developed by NASA will require a robust, on-platform, Integrated System Health Management (ISHM) function. Currently the DSH is contemplated to be stationed at the L2 Lagrangian point outbound from the lunar orbit. This will provide a vantage point of the back side of the moon as well as to serve as a jumping off platform for manned trips to Mars, the Moon, or near Earth asteroids. The ISHM function includes the monitoring, diagnostics, prognostics, and failure mitigation strategies and capabilities for any viable failure modes of the DSH. To evaluate a prototype of this approach, NASA has assembled a full scale, ISS derived, DSH prototype at the Marshall Space Flight Center (MSFC), involving a wired ISHM sensor network of over 80 sensors located at various points where early system failure mechanisms may be detected and analyzed. However, it is anticipated that a wired, distributed architecture could involve many pounds of complex cable harnesses and connectors, along with the commonly encountered problems of accessibility, flexibility and maintainability. In the high likelihood that modifications or upgrades are needed, these complexities result in higher design and build cost along with increased operational costs as in-flight anomalies occur that could require the addition of different sensors or different sensor locations. To address these issues, the ISHM team at MSFC is studying a wireless, distributed architecture with on- platform, advanced prognostic and diagnostic capabilities. The approach being considered is based on the X-33 ISHM system which consisted of hardware identical remote health nodes (RHN) and a central vehicle health management computer. Each RHN was very flexible and reprogrammable to enable it to interface directly with all the health monitoring sensors. For application on the DSH, modifications to the RHN are being considered. These changes and resulting upgraded capabilities are described in this paper. As ISHM sensor technology gets smaller, more robust, and includes wireless interfaces for communication and power, the approach will be to connect these wireless sensors by adding state-of-the-art wireless technology to the X-33 developed RHN. This wireless approach eliminates connectors and cables, thus reducing development, installation and life cycle costs while improving reliability and flexibility of the ISHM systems.

Wave propagation is investigated in sandwich composite panels using analytical approach for layered materials, Mindlin plate theory and finite element modeling in the context of developing an on-board structural health monitoring system. It is shown that theoretical results are in agreement with the results of numerical simulations and with experimental results.

This paper reports on analytical as well as computer simulation of waves propagating in sandwich-type composite structures. Sandwich-type composites are being studied for use in NASA’s new heavy lift launch vehicle, and flaw detection is crucial for safety and for failure prognostics. Theoretical analysis, as well as numerical modeling, is needed for benchmarking of available technologies for structural health monitoring (SHM) sensors and sensor systems. This benchmarking activity is important for answering the basic question of what minimum flaw size can be detected by the existing SHM based monitoring methods. Sandwich panels with foam, WebCore and honeycomb structures were considered for use in this study. Eigenmode frequency analysis and Frequency Response Analysis of the panels were made to understand fundamental properties of the panel physics and limitations that may affect the application of current SHM sensors and methods. An analytical study of the transient wave propagation is considered based on Mindlin plate theory. The mathematical model, accompanied by numerical simulations, shows that small size defects can be recognized but the frequency of waves should be sufficiently high. It is concluded that a combination of analytical results coupled with the high-fidelity simulations should make it possible to analyze experimental data and to predict the applicability of SHM methods for this type of structure.