Johan Tryding

Y-peel characterization of adhesively-bonded carton board: an objective method

Carton board packages are often closed with an adhesive. The adhesive joint thus formed has to meet the demands during the entire product life from converting to end-use. The adhesive joint has to be characterized if it is good or bad for the actual application. Today such characterization is done by manually peeling the joint, immediately after the adhesive application in the gluing machine. The manual peel test is a subjective test that is operator dependent. An operator needs long experience to be able to perform a manual peel test. Therefore, the packaging industry is interested in a test method that can objectively predict good or bad adhesive joints. The adhesive joints have been tested in the so-called Y-peel test arrangement. An advantage of the Y-peel test is that it gives an objective result from the force–elongation curve. Testing has been performed with carton boards of two different thicknesses. Hotmelt adhesive was used and the open time was varied in the glue applicator. It was found that the Y-peel test gives results in qualitative agreement with the manual peel test. Moreover, by evaluating the energy consumption (dissipative energy) during the Y-peel test it was possible to obtain not only a qualitative but also a quantitative assessment of the adhesive joint.

A low cycle fatigue criterion based on non-linear fracture mechanics

A new approach to the low cycle fatigue problem, based on non-linear fracture mechanics, is investigated. The method is designed to predict final failure of engineering structures containing cracks that are small compared to the significant length dimensions of the structure. The suggested procedure is simple to apply and the failure load can be predicted for a moderately low number of major load applications. The method is confirmed by a large number of experimental tests. Different specimen sizes and types are investigated and by using a scaling factor the results can be given for each tested material in a comprehensive form, irrespective of specimen geometry and initial crack length. In the experiments steel and aluminium materials were used.