<title>In-situ sensory technique for in-service quality monitoring: measurement of the complex Young's modulus of polymers</title>

Abstract

Applications ofpolymeric adhesives injoining different materials have necessitated quantitativehealth inspection of adhesive joints (coverage, state of cure, adhesive strength, location of voids, etc.). A new in-situ sensory method has been proposed in this paper to inspect the amount and distribution of the critical constituents of polymers and to measure the characteristic parameters (complex Young's modulus and damping). In this technique, ferromagnetic particles have been embedded in a polymeric matrix, similar to a particle-reinforced composite. The dynamic signatures extracted from the tests as a result of magnetic excitation of the embedded ferromagnetic particles are used to evaluate the complex Young's modulus of the host polymers. Moreover, the amplitude of the frequency response is utilized to identify the amount and distribution of embedded particles in polymeric materials or adhesive joints. The results predicted from the theoretical model agree well with the experimental results. The theoretical analyses and the experimental work conducted have demonstrated the utility of the sensory technique presented for in-service health interrogation.

<title>Magnetic activation of embedded sensory particles in active tagging interrogation of adhesive bonding</title>

“…Figure 2a shows an air opening in a closed magnetic loop, in which the average field intensity along the z-axis, Ha, is determined by4 P0 laly where M is the magnetization in the ferrite yoke, NJ the magnetomotive force in Ampere-turns, 'a the air gap length and the axial length of the yoke. VHmdV (7) where m is the volume percent of the tagging particle. But on the other hand, the assumption that Ha 5 COflSthflt fl the opening is true only when 'a is much smaller than the diameter of the yoke's cross section R, and the average gradient along the z axis W/& increases as 'a grows due to the flux fringing.…”