Instrumented End Notched Flexure – Crack propagation and process zone monitoring. Part I: Modelling and analysis

Analysis of the three-point bending, End Notched Flexure (ENF), test is presented for exploitation with a new experimental methodology using the backface strain monitoring technique. The model consists of two Timoshenko beams joined with a two parameter elastic foundation, to evaluate stress and strain fields in both adherends and the adhesive layer, together with the specimen compliance and energy release rate. This model is compared to a simplified case, from which a comprehensive experimental method is proposed for precise monitoring of crack propagation and measurement of interface shear compliance during the ENF experiment. In addition, simple formulae are proposed for evaluating mode II energy release rate, and possible experimental artefacts due to asymmetric loading conditions are evidenced.