Modern aerospace structures use a large amount of composite materials because of their light weight and high strength properties. Composite materials are unfortunately susceptible to internal damages from impacts to the structure. In many situations, there may not be visible external indications of the damage. The Information Processing Group is developing signal processing algorithms to detect, locate and characterize (for example, estimate the damage outline and damage type) such damage using arrays of sensors and actuators embedded in the structure. Since many composite structures are anisotropic, and it is often difficult to characterize complex structures accurately, it is desirable to perform these functions with little or no prior knowledge of wave propagation properties within the structutre.
The ultimate goal of the work is to facilitate unsupervised repair and maintenance decisions based on automated and quick inspection of the structure. Such capabilities will result in condition-based maintenance strategies instead of the currently employed schedule-based maintenance strategies.The group’s current activities in this area involves two different directions:
Passive algorithms for detecting, locating and characterizing damage due to impact. In this approach, the sensors continuously listen for acoustic emission or acoustic emission-like signals that are generated during impact and arrives at the sensors after traveling through the structure. Once the acoustic emission signals are detected, the algorithms analyze the data to locate the source of impact(s), and characterize damage that may have been induced in the structure during the impact.
Active algorithms that employ an array of actuators to induce vibrations in the structure and then use the resulting sensor signals to detect, locate and characterize damage.