Dynamic fragmentation of an alumina ceramic subjected to shockless spalling: An experimental and numerical study

• Shockless spalling tests on alumina are performed using a high-pulsed power generator.
• A strain-rate sensitivity of the spall strength of alumina is noted.
• Recovering and post-mortem analysis of a damaged but unbroken specimen.
• An anisotropic damage model (DFH model) is used to simulate spalling tests.
• Simulations are in agreement with experiments in terms of velocity profile and damage.

Ceramic materials are commonly used as protective materials for infantry soldiers and military vehicles. However, during impact, intense fragmentation of the ceramic material is observed. This fragmentation process has to be correctly numerically simulated if one wants to accurately model the dynamic behaviour of the ceramic material during impact. In this work, shockless spalling tests were performed on an alumina ceramic using the high-pulsed power generator (GEPI) equipment. These spalling tests allowed us to master the experimental strain-rate magnitude of the tensile loading applied to the specimen. The spall strength is observed to be rate dependant and the experimental configuration allowed for recovering damaged but unbroken specimen which gives further insights about the fragmentation process initiated in this ceramic material. The collected experimental data has been compared with corresponding numerical simulations conducted with the DFH (Denoual–Forquin–Hild) anisotropic damage model. This modelling approach relies on the description of the main basic micromechanisms activated at high loading rates using physical parameters related to the population of defects that produces multiple cracking in the ceramic material at high strain-rates. Very good agreement was observed between numerical simulations and experimental data in terms of free-surface velocity, size and location of the damaged zones along with crack density in these damaged zones.