Fig. 3

Fracture surface analyses of epoxy-Cu-MPTMS-SiO₂ structures under fatigue loading. a Representative optical micrographs from an as-obtained Cu fracture surface (scale bar = 300 μm), b the same with the metal film etched off to expose the polymer (scale bar = 300 μm), and c the SiO₂ fracture surface (scale bar = 100 μm). The sizes and shapes of the metal wrinkles and the polymer microvoids are correlated (circles regions). Average d metal wrinkle coverage χ_Wrinkle (scale bar = 100 μm) and e microvoid coverage χ_Microvoid (scale bar = 200 μm) from fracture surfaces of structures with (red squares), and without (blue circles) MPTMS. Representative optical micrographs inset in d and e capture metal wrinkling and polymer microvoiding at select frequencies. The data in this figure were from experiments at \(p_{{\mathrm{H}}_{2}{\mathrm{O}}}\) = 1.3 kPa. The width of the bands drawn through the data points connote the experimental uncertainties measured as standard deviation