10/13/19: Prof. Lee presents a NSF MOMS grantee poster at SES conference.

56th Annual Technical Meeting of the Society of Engineering Science (SES2019)

October 13 - 15, 2019, Washington University, St. Louis, MO, U.S.A.

Extreme mechanical deformation of nanostructured block-polymer microspheres

Jae-Hwang Lee, Ara Kim
1 Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst (leejh@umass.edu)
Among additive manufacturing techniques, cold spray [1] utilizes high-velocity impacts of solid microparticles or feedstock powders. Cold spray with polymeric microparticles have been largely unexplored due to the inherent complexities arising from its strong strain-rate-dependency. We envisioned that multi-phase polymers or phase-separated di-block copolymers (BCPs) consisting of two or more mechanically distinctive nano-scale phases can be tailored to have high-strain-rate mechanical properties, which are favorable to additive manufacturing via cold spray.
In order to gain deep insight into the material’s behavior at the high-strain-rate regime, controlled impact tests at velocities that are relevant for cold spray applications, we performed single-particle impact experiments of polystyrene-block-polydimethylsiloxane BCP microparticles because polystyrene and polydimethylsiloxane phases are glassy and rubbery, respectively. Using the laser-induced projectile impact test (LIPIT) method, [2,3] a single BCP microparticle was accelerated to high velocities (100 - 600m/s) and the BCP microparticle’s collision with a rigid substrate was observed with an ultrafast imaging system using femtosecond illumination pulses. Coefficients of restitution and collision-induced extreme plastic deformation features of the BCP particle were investigated for different impact conditions. Using electron microscopy and focused ion beam milling, we also demonstrated impact-induced morphological changes of the BCPs.
* This material is based upon work supported by the National Science Foundation under Grant No. CMMI-1760924.