Analytical solutions to the shear strength of interfaces failing under flexure loading conditions

Flexure experiments have been performed on steel substrates having a rib of methacrylate resin cast as a stiffener on the steel. Samples were loaded until resin delaminated from the substrate and the load at failure was recorded. An analytical solution for a composite beam was used to relate the force at failure to interfacial shear stress. This resulted in an average estimated shear strength of 490 kPa (71 psi) for a resin/steel interface. The accuracy of the analytic solution was examined using a three-dimensional finite element analysis (FEA). The FEA was also used to examine the assumptions of the first approximation analytic solution. The analytic solution can be applied more generally, considering the mechanical characteristics of both constituents, to design experiments that lead to a simplified determination of interfacial shear strength.