Determination of dynamic shear stress – Strain relationship in adhesively bonded assemblies

Abstract
In this paper, we are interested in the measurement of the shear stress-strain relationship in the adhesive layer of bonded assemblies. Precisely, we investigate the sensitivity of this relationship to strain rates. For this target, an M-shape specimen is tested with conventional split Hopkinson pressure bar (SPHB) system. Hence, we can reach impact velocities in the range of 20 m/s. The accuracy of dynamic tests is investigated by numerical experiments. Indeed, the experimental set-up (two Hopkinson bars and the M-shape) is modelled on ABAQUS 6.6. From the simulations, we deduce the strain at one cross-section of each bar as in a SHPB test. We apply then the conventional methodology to retrieve the strain and the stress in the adhesive layer under the homogeneity assumption. The retrieved strain and stress are compared to the mean strain and stress, respectively, in adhesive layer. Finally, we find that the SHPB methodology provides a good approximation of the stress however it over-estimates the strain. Fortunately, this over-estimation is quasi-independent of strain, i.e., the SHPB strain is quasi-proportional to the mean strain. A numerical coefficient can then be deduced from numerical simulations to correct the SHPB strain.