Abstract
We demonstrate the nondestructive imaging of internal triaxial strain in visibly opaque black rubbers by employing the polarization-sensitive terahertz time-domain spectroscopy (PS THz-TDS) technique. From the sample thickness and the differences in amplitude and phase between orthogonal components of the terahertz wave that passed through the sample, the degree of birefringence and the angle of the slow optic axis were determined. We were able to convert the birefringence data into the amount and orientation of the internal strain through a Monte Carlo simulation that correlates the birefringent properties of the rubber with deformation. By comparing the strain map obtained from the PS THz-TDS measurements with that obtained by conventional digital image correlation, we found that both experimental and spatial distributions of the strain are in overall good agreement, except around the clamped sample regions. The deviations result from the intrinsic difference in the obtained strain information between two experiments and it is confirmed that our method based on PS THz-TDS is suited for evaluating the spatial distribution of the internal strain in black rubbers.
Highlights
During the past century, polymeric materials have emerged as one of the most popular and useful materials because of their abundant convenient features, such as mass productivity, light weight, and low cost
One can achieve a non-contact, in situ, and nondestructive evaluation of the materials because visible light requires no waveguide in the vicinity of the sample and inflicts less damage on the sample compared with X-ray
Visible light cannot access the internal strain in visibly opaque materials, most polymer-based practical products are opaque for visible light
Summary
Polymeric materials have emerged as one of the most popular and useful materials because of their abundant convenient features, such as mass productivity, light weight, and low cost. Internal triaxial strain imaging of visibly opaque black rubbers with terahertz polarization spectroscopy We report a method for evaluating the internal strain in a visibly opaque styrenebutadiene rubber with polarization-sensitive terahertz time-domain spectroscopy (PS THz-TDS).
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