Evolution of failure pattern by laser induced shockwave within an adhesive bond

Quality control on adhesively bonded aluminum plates is a crucial step for the lifespan of an engineered structure. LASer Adhesion Test (LASAT) is an appropriate solution for testing at local scale and with various amplitude ranges in dynamic conditions at very high strain rate. This method allows determining the laser energy for creating a shock that yields to damage and/or debonding: a sane assembly will resist to the tensile stress whereas an improper one will fail. However, this process requires a focus on the failure mechanisms and its kinetics for a better understanding of the energy level of reference for delamination of the assembly. The signature of the damage can be observed in the free surface velocity records processed by the use of a Photonic Doppler Velocity (PDV) system. Following study shows the setup optimization for microscopic and macroscopic failure observation and the effects of laser shocks. Samples were impacted at various laser energies in order to observe the damage evolution with a PDV system and post-shock microscope observations of recovered samples. Different patterns of damage were observed. Numerical simulations with finite element method in explicit schemes were conducted for a better understanding of those mechanisms. Those simulations aim at reproducing phenomenon leading to the apparition of damage, shape of the crack and the signature on the back face velocity measurement. Then experimental and numerical approach can be compared in terms of aspect and velocity measurement. To achieve this goal, a relation between the laser energy and its resulting shock pressures has been established and a set of parameters for the Johnson-Cook constitutive law has been adapted for aluminum 2024T3 at very high strain rates (>10(5) s(-1)).