Nov. 9: Prof. Lee gives a Colloquium talk at RPI

Prof. Lee gave a MANE colloquium talk at Rensselaer Polytechnic Institute (RPI) at Troy, NY.

“Dynamic mechanical characterization using micro-bullets”

Precise techniques applying mechanical deformation at the micro-scale, such as an atomic force microscope, nanoindenters, or micromanipulators, have become more conventional in a wide range of disciplines. Due to the quasi-static nature of these techniques, the object being deformed stays in near equilibrium. As a deformation speed becomes comparable to the speed of sound of constituent materials, however, corresponding mechanical responses cannot simply be extrapolated from those at the quasi-static conditions due to various dynamic and nonlinear effects.

My group has worked with a microscopic ballistic technique called Advanced Laser Induced Projectile Impact Testing (α-LIPIT) to provide the HR ballistic characteristics of various materials ranging from conventional materials to novel nanomaterials. In this talk, I will introduce our recent progress on the HR study using α-LIPIT with several materials including aluminum particles, Kevlar fibers, graphene, and graphene-polymer composites. Highly-controlled single micro-projectile impact experiments are carried out and the ultrafast optical microscopy, which utilizes femtosecond laser pulses, enables precise quantification of the micro-projectile’s motion during the supersonic collision events. Based on the tracking of the projectile motion, the real-time force applied by the projectile is also explicitly defined.