The stress intensity near a stiffener disclosed by photoelasticity

Can the thickness of a thin inclusion (in a matrix material) be made so small (though retaining sufficient stiffness and matrix adhesion) to generate ‘in practice’ a stress state in agreement with the analytical (square-root singular) solution for a rigid line inclusion (so-called ‘stiffener’) embedded in a linear elastic plate? Can this inhomogeneous stress state be generated for tensile loading parallel to the stiffener? We provide a direct and positive answer to these questions, by showing how to produce elastic materials containing thin inclusions and by providing photoelastic investigation of these structures. The experiments fully validate the stress state calculated for an elastic plate containing a rigid (finite-length) line inclusion, until a distance from the inclusion tip on the order of its thickness, corresponding to a stress concentration up to seven.