In-depth numerical analysis of the TDCB specimen for characterization of self-healing polymers

•Crack propagation simulations with the TDCB specimen were performed using XFEM.•The fracture mechanical model describes the shape and advance of the crack tip.•Numerical results were compared with experimental data of self-healing polymers.•The pin-hole friction and non-symmetrical pre-cracks introduce high experimental errors.•Experimentalist must be aware about the limitations of the TDCB specimen.

The Tapered Double Cantilever Beam (TDCB) is the common specimen to study self-healing thermosetting polymers. While this geometry allows characterising the mode I fracture toughness without taking into account the crack length, the experiments show an important dispersion and unstable behaviour that must be taken into account to obtain accurate results. In this paper, finite element simulations have been used to understand the experimental behaviour. Static simulations with a stationary crack give the local stresses and the stress intensity factors at the crack tip when the TDCB is under load. In addition, the eXtended Finite Element Method (XFEM) has been used to make quasi-static crack propagation simulations. The results indicate that the crack tip has a curved profile during the propagation, advancing more at the edges than at the centre. The crack propagation begins when the applied load reaches a critical value. The unstable crack propagation noted in the experiments can be reproduced by introducing an unstable behaviour in the simulations. Finally, the sensitivity of the critical load has been studied as a function of the friction between pin and hole, tolerance of geometrical dimensions, and cracks out of the symmetric plane. The results can partially explain the dispersion of the experimental data.