Nondestructive Damage Detection of a Magentostricive Composite Structure

Abstract

The integrity of composite structures gradually degrades due to the onset of damage such as matrix cracking, fiber/matrix debonding, and delamination. Over the last two decades, great strides have been made in structural health monitoring (SHM) community using various sensing techniques such as acoustic emission, eddy current, strain gages, etc., to diagnose damage in aerospace, mechanical and civil infrastructures. Embedded sensing offers the prospects of proving for real-time, in-service monitoring of damage were weight savings is a major factor in Aerospace Industry. It also provides for a new nondestructive indication of early stage damage. Defect detection and monitoring of fatigue in structural materials can be captured through local indicators of a change of the magnetic properties within the damaged sites. In this present work, magnetostrictive particles such as Terfenol-D were embedded in a composite structure, along with acoustic emissions technique, to validate the damage in a composite system undergoing qausi static and fatigue loading. As the applied load and fatigue cycles increased, the change in the magnetization flux density was captured using a non-contact magnetic field sensor. It was confirmed through numerous tests that a change in the magnetic properties of the composite served as an indicator of early stage damage detection.