Towards a consensus on mode II adhesive fracture testing: Experimental study

•Experimental mode II test campaign of adhesive joints.•Comparison among ENF, ELS, 4ENF and MMB test results.•Comparison between LEFM and NLFM (J-integral) data reduction methods. The objective of this work is to define reliable test methodologies and data reduction methods to obtain comparable results among the most common mode II test methodologies: the End-Notched Flexure (ENF), the End-Load Split (ELS), the 4-point End-Notched Flexure (4ENF), and the Mixed Mode Bending (MMB) test at 100% of mode II. For this reason, an experimental test campaign consisting of the abovementioned four mode II test methods was carried out. The J-integral was implemented in the ELS, the ENF and the MMB tests and a J-integral closed form was developed and implemented for the 4ENF test. Then the J-integral was compared to the data reduction methods based on Linear Elastic Fracture Mechanics (LEFM). The results obtained from the J-integral based methods were independent from the test methodology and obtained very good agreement among the tests. In addition, from the experimental results the advantages and drawbacks of the different test procedures are analysed and discussed, concluding that the ELS test is the most suitable to measure mode II fracture toughness of adhesives.