Enhanced strength of cyclically preloaded arrays of pillars

Under compression, a cyclically precompressed nanopillar supports greater load than its as-fabricated counterpart. Such an improvement on mechanical properties takes place only when the preloading process is tuned carefully with regard to a particular pillar being tested. This experimental evidence raises a question: does a cyclic preloading applied simultaneously to an ensemble of nanopillars enhance the overall strength of the system? To answer this question, we simulate numerically cyclic loadings of pillars assembled into an array. Assuming that the pillars are characterized by random strength-thresholds $\left\{{\sigma }_{th}\right\}$, we demonstrate that quasi-statically compressed arrays with initial cycling process support higher load than the corresponding ones with no precompression. By applying the fibre bundle model, we evolve $\left\{{\sigma }_{th}\right\}$ and estimate that the mean strengthening may attain 7–9% for an optimally tailored cycling.