  The multi-scale nature of architectured materials raises the need for
advanced experimental methods suitable for the identification of their
effective properties, especially when their size is finite and they undergo
extreme deformations. The present work demonstrates that state-of-the art image
processing methods combined with numerical and analytical models provide a
comprehensive quantitative description of these solids and their global
behaviour, including the influence of the boundary conditions, of the
manufacturing process, and of geometric and constitutive non-linearities. To
this end, an adapted multi-scale digital image correlation analysis is used to
track both elongations and rotations of particular features of the unit cell at
the local and global (homogenized) scale of the material. This permits to
observe with unprecedented clarity the strains for various unit cells in the
structure and to detect global deformation patterns and heterogeneities of the
homogenized strain distribution. This method is here demonstrated on elastic
sheets undergoing extreme longitudinal and shear deformations. These
experimental results are compared to non-linear finite element simulations,
which are also used to evaluate the effects of manufacturing imperfections on
the response. A skeletal representation of the architectured solid is then
extracted from the experiments and used to create a purely-kinematic
truss-hinge model that can accurately capture its behaviour. The analysis
proposed in this work can be extended to guide the design of two-dimensional
architectured solids featuring other regular, quasi-regular or graded patterns,
and subjected to other types of loads.
