Nondestructive Damage Detection of a Magnetostrictive Composite Structure

Asha Hall,Michael Coatney,Oliver Myers,Jin Hyeong Yoo,Brandon Williams,Nicholas Jones,Natasha Bradley

doi:10.3390/icem18-05276

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 providing for real-time, in-service monitoring of damage were weight savings is a major factor in Aerospace Industry. In this present work, magnetostrictive particles such as Terfenol-D were embedded in a composite structure, along with multiple SHM techniques, to capture the damage in an IM7-carbon fiber reinforced polymer composite system undergoing fatigue loading. As the internal stress state increases, the change in the magnetization flux intensity was captured using a non-contact magnetic field sensor. A damage diagnosis system was established along with an acoustic emissions technique to further validate the damage captured by the embedded system. The goal of this project is to identify the change in the mechanical and magnetic property within a composite material during the evolution of damage. Several characterization techniques were used to determine interfacial fiber-matrix interactions which will provide for a more comprehensive understanding of the composite interfaces.

Highlights

The integrity of composite structures gradually degrades due to the onset of damage such as matrix cracking, fiber/matrix debonding, and delamination
Ferromagnetic materials have proven useful as strain transducers in harsh-environment applications. Magnetostrictive materials such as Galfenol (Fe-Ga alloy), Alfenol (Fe-Al alloy), and Terfenol-D (Tb0.3Dy0.7Fe1.92) (TdVib, LLC., Ames, IA, USA) in a polymer composite are great candidates for embedded damage assessment of composite structures. 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
Future tests will be conducted incorporating acoustic emission to further validate the correlation between the changes in magnetic flux intensity to the increase in microcrack density

Summary

Introduction

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. Our current research examines the possibilities of embedding nanomaterials into composite laminates as a minimally invasive, non-contacting, nondestructive evaluation and sensing technique. Proceedings 2018, 2, 416 structure with the capability of self-sensing damage by evaluating the integrity of the material in realtime. Once an external magnetic field is applied the electronic spins line with each other and become magnetized.Magnetostriction is a property of ferromagnetic materials such that when an external magnetic field is applied the domains align to the external field causing their shape or dimensions to change during the process of magnetization.

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Results

Conclusion