The literature concerning ± laminates under mode II (propagation mode) loading encounters a difficulty in calculation of the structural dimensions. Indeed, it is rare to have a specimen geometry which fully satisfies the conditions for application of the Linear Elastic Fracture Mechanics (LEFM). Thus, the aim of this work is the optimisation of the specimen geometry which allows the characterisation of mode II by the approach of the LEFM concept. The results obtained show an interaction between the geometrical characteristics of the specimen (thickness h), the angle of orientation of the plies () and the characterisation of delamination. The experimental results are in good agreement with the analytical predictions. The use of the acoustic emission allows us to observe that delamination is only one final stage in a process of damage which starts well before.