Shear and foundation effects on crack root rotation and mode-mixity in moment- and force-loaded single cantilever beam sandwich specimen

Foundation effects play a crucial role in sandwich fracture specimens with a soft core. Accurate estimation of deformationcharacteristics at the crack front is vital in understanding compliance, energy release rate and mode-mixity infracture test specimens. Beam on elastic foundation analysis of moment- and force-loaded single cantilever beam sandwichfracture specimens is presented here. In addition, finite element analysis of the single cantilever beam specimen isconducted to determine displacements, rotations, energy release rate and mode-mixity. Based on finite element analysis,a foundation modulus is proposed that closely agrees with the numerical compliance and energy release rate results forall cases considered. An analytical expression for crack root rotation of the loaded upper face sheet provides consistentresults for both loading configurations. For the force-loaded single cantilever beam specimen (in contrast to themoment-loaded case), it was found that the crack length normalized energy release rate and the mode-mixity phaseangle increase strongly as the crack length decreases, a result of increased dominance of shear loading.