Experimental Nondestructive Testing Using Magnetostrictive Particles Embedded in Carbon Fiber Reinforced Polymer Beams

In this paper, the experimental sensing results of damage testing using magnetostrictive particulate sensors, embedded in fiber reinforced polymer laminates, are presented. Carbon fiber reinforced polymer (CFRP) laminates (Hexcel AS4/3501-6) are embedded with terfenol-d particles and the ply count is varied to observe the change in the sensing. Sensing is observed using a non-contacting magnetostrictive strain sensor setup. The sensing parameter observed is the voltage induced in the secondary circuit. Two of the three batches presented have laminates that are embedded with .5″×.5″, release agent coated patches that prevent bonding between the terfenol-d and the CFRP layer. The laminate ply count ranges from 2–14 unidirectional plies. Two fabrication methods are used to distribute the particles in the laminate. The experimental results from the three batches reveal that the fabrication technique has a significant effect on the sensing signal. The effect of particle accumulation near the sensor dominates the sensing signal and makes the presence of a delamination difficult to assess. The experiments also show that when the ply count is varied, there is not much variation in the sensing signal.