Comparison between two fracture tests, SENB vs. DCDC applied to acrylate polymers

We have compared the mode I opening critical energy release rate (GIc) measured using the single edge notch bending test and double cleavage drilled compression test on an elastic fragile PMMA and a bulk viscoplastic acrylate used as a glue for wind turbine blades.

The study details the experimental procedure, for the crack initiation and the test conditions.

We have used the linear elastic fracture mechanics for the PMMA and numerical finite element analyses for the other acrylate that shows some plasticity. We found for each test, values of the critical energy release rate GIc that are in accordance with other results from the literature. However both tests do not compare well, the SENB test giving a value much larger than the DCDC test. This raises the question of the limit of considering one quantity GIc even when considering only the opening mode of fracture. Note, that we considered two models of plasticity, either defined by a von Mises criterion or a Drucker-Prager one, and that do not change the general conclusion of the paper. However, it seems like the Drucker-Prager criterion was more appropriate in our case.

See the reference below for all details on the experimental and modeling parts as well as the discussion. This work was part of Arnaud Coq PhD.
[1] A. Coq, J. Diani, 2024. Comparison of Mode I fracture toughness of an elastic and an elastoplastic methyl methacrylate polymer as measured by SENB and DCDC tests. Engineering Fracture Mechanics, 306, 110237, https://doi.org/10.1016/j.engfracmech.2024.110237.