  Quasi-brittle materials endowed with (statistically) self-similar hierarcical
microstructures show distinct failure patterns that deviate from the standard
scenario of damage accumulation followed by crack nucleation-and-growth. Here
we study the failure of paper sheets with hierarchical slice patterns as well
as non-hierarchical and unpatterned reference samples, considering both
uncracked samples and samples containing a macroscopic crack. Failure is
studied under displacement-controlled tensile loading as well as under creep
conditions. Acoustic emission records and surface strain patterns are recorded
alongside stress-strain and creep curves. The measurements demonstrate that
hierarchical patterning efficiently mitigates against strain localization and
crack propagation. In tensile loading, this results in a significantly
increased residual strength of cracked samples. Under creep conditions, for a
given range of lifetimes hierarchically patterned samples are found to sustain
larger creep strains at higher stress levels; their creep curves show unusual
behavior characterized by multiple creep rate minima due to the repeated arrest
of emergent localization bands.
