Diagnosis and Prognosis of Space Structures for Integrated Systems Health Management

Student : Ajay Raghavan

Sponsor : NASA Constellation University Institutes Projects / Advanced Composites Technologies Program


Summary:

The overall objective is to increase the safety, affordability and sustainability of exploration missions through active structural diagnosis and prognosis for vehicle health monitoring. Because of the extensive use of composite materials in aviation, it is imperative to develop an appropriate structural health monitoring (SHM) methodology to monitor their condition for defects to ensure proper functionality. Guided waves (GW) offer an attractive alternative for SHM due to their ability to travel long distances over the surface as well as through the thickness of a structure.

Project:

  • Goal for the research is to analyze the theoretical model which comprises of first determining the wave field in a bulk composite and then extending it to a composite laminate. We then use the interface continuity and surface traction conditions to derive the displacements in the composite plate by residual theorem. Then the theoretical model is simulated by a Fortran code to find the displacements. Experiments are carried out on composite plate to verify the simulation by generating the guided waves with piezo-actuators and then measuring the out of plane displacements with laser vibrometer.

Theory
Experiment

Comparison of out-of-plane displacement pattern for cross-ply [0/90]6S laminate at 75kHz.

Objectives:

  • Piezoelectric-excited GW methodologies that will be used to monitor cracks, delamination and impact damage in composite load-bearing structures and attachment integrity for bonded/bolted joints over temperatures ranging from 700F to 3000F.

  • Robust diagnostic and prognostic metrics to infer damage presence, type, extent, and location through time-frequency signal processing analyses.

  • Design guidelines for installing active GW SHM sensor/actuator arrays for detecting damage in composite structures.