An improved methodology for measuring the interfacial toughness of sandwich beams

Existing interfacial toughness tests are evaluated for their accuracy and suitability for application to a wide range of sandwich structures and environments. It is shown that geometric nonlinearities and/or axial load coupling can cause errors in the perceived toughness as obtained by many of these tests and their associated data reduction methods. A previously proposed modified peel test is selected to eliminate the effect of axial load and a new, modified beam theory based method of data reduction is developed. Experiments and nonlinear finite element analyses are used to show that this approach produces highly accurate values of toughness, even in the presence of geometrically nonlinear behaviors. Mechanically attached loading tabs are described, allowing the test to be used for a wide variety of structures under various simulated usage environments.