Crack Tip Micromaching by Femtosecond Laser for Fracture Testing of Metal Laminates

This thesis presents an experimental study of the effects of ultrafast laser ablation on the mechanical properties of metal laminates followed by FEA simulation to elucidate future experimental potential. The metals investigated are copper, niobium, and copper/niobium accumulative roll bonded (ARB) laminates. The two laminate materials in this study have a nominal layer thickness of 1.8 microns and 65 nanometers; the effects of the laser processing on the ARB materials are characterized in the rolling direction as well as the transverse direction as the material exhibits anisotropic properties. The aforementioned materials are examined via scanning electron microscopy and energy dispersive spectroscopy techniques to obtain changes in layer restructuring and modification. The motivation of this study is to characterize the heat affected zone in the materials produced by ultrafast laser processing to determine whether ultrafast laser ablation is a viable method for creating artificial cracks for SEM in-situ mini cantilever fracture testing. A parameter space is defined to attempt to capture an acceptable set of laser settings which both reduce the heat affected zone and create an etched geometry mimicking a crack into the sample to facilitate crack propagation in bend testing. Finally, simulation is performed using ANSYS to determine sample geometry constraints induced by both the laser-notched crack tip’s geometry and the limitations of the experimental