An apparatus for mixed-mode fracture characterization of adhesive joints

This paper describes a method of measuring the toughness of adhesive joints in various mixed mode combinations from mode I (opening) to mode II (shear) relying exclusively on the load-displacement curve obtained from an universal testing machine and the displacement from two linear variable differential transformers (LVDT) connected to the specimen beams. The novelty of the method reported here is that it does not use a visual crack length measurement, instead employing a method that deduces the crack length from the displacement obtained from LVDTs. Relying exclusively on the three machine outputs described, it allows for an automated data reduction scheme and, therefore, results in an easier analysis that is both accurate and not depending on human observation. Validation of the mixed-mode results was performed using classic mixed-mode tests and classic pure-mode tests which provided comparable results, therefore validating the apparatus results.