Using self-healing materials in commercial applications requires healing chemistry that is cost-effective, widely available and tolerant of moderate temperature excursions. We investigate the use of tungsten (VI ) chloride as a catalyst precursor for the ring-opening metathesis polymerization of exo-dicyclopentadiene (exo-DCPD) in self-healing applications as a means to achieve these goals. The environmental stability of WCl 6 using three different delivery methods was evaluated and the associated healing performance was assessed following fracture toughness recovery protocols. Both as-received and recrystallized forms of the WCl 6 resulted in nearly complete fracture recovery in self-activated tests, where healing agent is manually injected into the crack plane, at 12 wt% WCl 6 loading. In situ healing using 15 wt% microcapsules of the exo-DCPD produced healing efficiencies of approximately 20%.
Among novel
non-destructive evaluation techniques for structural health
monitoring, the magnetostrictive (MS)-tagged fiber-reinforced
composites stands out as especially suitable due to:
(a) distributed sensory properties, (b) non-contact damage
detection, and (c) straightforward manufacturing
implementation. Experimental data and mathematical modeling of a
MS-tagged fiber reinforced composite beam under
bending (flexural) loading are presented. A brief review of the
state of the art identifies previous work on axially loaded
MS composites, but finds no previous work on
bending. Description of bending beam design and fabrication is
followed by theoretical analysis and by the description of
the experimental set-up and equipment used. Several analysis
models were used. Test data, with and without applying magnetic
bias field between loading cycles, is presented and results are
discussed. Numerical values for the stress and strain
versus magnetic flux density coefficients are given for
both annealed and non-annealed cases. Piezomagnetic coefficients
for the MS composite are calculated. The
correlation between the results developed in the present
paper for bending and previously published results for axial
loading is found to be within 10% after correction factors
depending on the quantity of the MS material.
Magnetostrictive composites have found increasing use as a tagging agent for structural integrity monitoring. A simple magnetic model based on Heisenberg–Weiss theory is put forth that provides guidance as to the physical parameters that govern the magnetic response of a Terfenol-D impregnated composite specimen in tension. Further, the model provides an effective analytic parameterization of the magnetic response, resulting from unidirectional tension, and affords estimates of these parameters.
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