Damage Characterization and Classification for Composite Honeycomb Structures

Advanced composite materials are increasingly being adopted for applications in airframe structures due to their high stiffness-to-weight and strength-to-weight ratios as compared to metallic materials. However, advanced composites are susceptible to barely visible impact damage, which could lead to a catastrophic failure if their initiation and growth are not monitored. Structural Health Monitoring (SHM) systems based on acousto-ultrasound methods have emerged as a promising new nondestructive inspection (NDI) technique for monitoring the onset and progress of structural damage. Lamb wave based baseline-subtraction techniques are widely used for distinguishing the damage from other structural features. However, these techniques are only suitable for monitoring impact damage on large composite structures but cannot characterize and classify debond, delamination and core crushing types of damages in honeycomb structures. This paper presents an innovative damage characterization and classification techniques that are capable of detecting, locating and characterizing different types of damage in carbon fiber honeycomb structural components of rotorcraft vehicles. Tests were conducted on the system for characterizing and classifying debond, delamination and core crushing type damage on carbon-fiber Nomex-honeycomb-core structures. Details of the technique along with the results will be presented and discussed in this paper.