Investigation of the crack front process zone in the Double Cantilever Beam test with backface strain monitoring technique

Crack growth along a Double Cantilever Beam bonded joint under mode I constant separation rate is investigated. Measurements of compliance show that the elastic fracture scaling law is obeyed and so classical Linear Elastic Fracture Mechanic theory could be applied. To refine the standard test, a protocol of backface strain monitoring is adopted. This method allows better estimation of crack front position, as well as fine investigation of stress distribution along the bondline. Strain measurements also reveals that the presence of the fractured adhesive coating has to be taken into account in the evaluation of the energy release rate.

► Strain gauges are bonded to DCB specimen to investigate the process zone.
► Strain evolution in case of brittle interface is modelled with Timoshenko beam on elastic foundation.
► Backface strain monitoring instrumentation allow precise control of DCB test.