In this study, analytical solutions for estimating two cohesive parameters, stiffness
and strength in a bilinear traction law, were developed in conjunction with the
ASTM double-cantilever beam (DCB) mode I testing. A zero-thickness elastic
foundation zone containing two layers in series was assumed in the analytical
derivation: a cohesive zone located underneath a beam elastic zone that is adjacent to
the beam bottom surface, for accurately identifying the DCB opening displacements
at both loading point and crack tip. The total deflection was comprised of three
contributions: bending, lateral shearing, and beam thickness deformation. The
analytical analysis eliminates drawbacks caused by rigid thickness in the classical
beam theory. Consequently, good agreement in the beam deflections at both the
loading point and the crack tip was obtained between the proposed analytical
solution and an evaluation of numerical study results. This good agreement ensured
that accurate cohesive parameters were derived analytically. Results showed
that the proposed method explains why different cohesive parameters can
lead to similar load-displacement results. Discussion on the application of
the proposed analytical methodology and the associated cohesive values is
presented.
