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We report quantitative nanocrack formation upon adjusting the mechanical tensile strain applied to a Pd thin film on an elastomeric polydimethylsiloxane (PDMS) substrate and its detection properties for H gas in air. Nanocrack formation in Pd/PDMS substrates was controlled through the application of tensile strains that varied in the range 30-120 % during mechanical stretching/compression. This method can be used to modulate nanocrack formation along both the x- and y-axes over a large area. Increasing the applied tensile strain to 90 % induced the appearance of horizontal cracks along the y-axis in addition to an increased number of vertical cracks along the x-axis. When the strain reached 120 %, ordered nanocracks abundantly propagated on the Pd surface in both the directions. Gas detection properties were dramatically enhanced, with a very low detection limit of 50 ppm H in air observed for 120 % strain. This was attributed to the large surface area in the Pd nanocrack pattern, which readily allowed for volume expansion. These results provide a simple mechanism for controlling the detection properties of H gas sensors with low detection limits in air. [ABSTRACT FROM AUTHOR]

Infrared thermography was used to study damage developing in woven fabrics. Two different experiments were performed, a ±45° tensile test and a rail shear test. These two different types of tests show different damage scenarios, even if the shear stress/strain curves are similar. The ±45° tension test shows matrix hardening and matrix cracking whereas the rail shear test shows only matrix hardening. The infrared thermography was used to perform an energy balance, which enabled the visualization of the portion of dissipated energy caused by matrix cracking. The results showed that when the resin is subjected to pure shear, a larger amount of energy is stored by the material, whereas when the resin is subjected to hydrostatic pressure, the main part of mechanical energy is dissipated as heat. [ABSTRACT FROM AUTHOR]