Investigation of defects in honeycomb sandwich structures
Date of Issue1994
School of Mechanical and Aerospace Engineering
The use of the mechanical impedance method for non-destructive testing and analysis of honeycomb structures is described in this thesis. Mechanical impedance instruments, MIA 3000, Versiscan and VP 200, were used to study the detachment of honeycomb structures on specimens which were made of two layers of thin aluminium skins with Nomex honeycomb cores. Both tumerical and experimental studies showed that the resonance frequency of a defected area was lower than that of the perfectly bonded area. It was concluded that the resonance frequency could be used to detect the defected area in a honeycomb structure. By varying the test frequencies, one could obtain different amplitudes or phases of impedance. With low test frequency, defected areas can be clearly identified by the marked amplitude variation. The test frequency which was slightly lower than the resonance frequency of the perfectly bonded area gave the best results. However, with test frequency higher than the resonance frequency of the perfectly bonded area, both the amplitude and phase of impedance were unable to show the defect effectively.
DRNTU::Engineering::Mechanical engineering::Control engineering
Nanyang Technological University