Structural Health Sensing of Damage Precursors using Magnetostrictive Particles Embedded in Composite Structures

Over the last two decades, tremendous progress has been made in structural health monitoring (SHM) using various sensing techniques such as acoustic emission, eddy current, strain gages, to diagnose damage in aerospace, mechanical and civil infrastructures. Despite this progress, there are still many challenges to address in SHM. Among these challenges is detection of precursors to matrix cracking, fiber/matrix debonding, and delamination. Magnetostrictive smart materials such as Terfenol-D (Tb0.3Dy0.7Fe1.92) (Etrema Products Inc., IA, USA) have proven useful as non-contact strain sensors using Hall Effect or pick-up coil to measure change in magnetization due to strain. In this study, our team will conduct a specific number of fatigue cycles at 1, 100, 1,000, 10,000, 100,000, and 1,000,000 cycles. After each fatigue loading a destructive examination of the specimen surface will be conducted by Scanning Electron Microscope (SEM). By this systematic evaluation, the phenomenon of crazing, the propagation of micro-cracks and delaminations, and the factors that lead to catastrophic failure will be investigated, thereby enabling correlation of the current damage state to the magnetization.