Numerical Simulation of the Deposition of Polystyrene-block-Polydimethylsiloxane (PS-b-PDMS) Particles on to Silica Substrate under Cold Spray and LIPIT Conditions

The impact of spherical polystyrene-block-polydimethylsiloxane (PS-b-PDMS) particles onto a flat silicon oxide (SiO₂) was simulated at 50-600 m/s with the acceleration mechanism of particle and separation rate (dδ/dt) dependent cohesive zone model (CZM). Material parameters of the polymer material were previously determined by using bonded particle morphology with the user-defined viscoplastic constitutive material model. Experimental results show polymer particles reveal bonding window with lower critical velocity (LCV) and higher critical velocity (HCV). Rebounded particles are used to identify critical fracture toughness (G_c) at associated impact velocity (IV), and variation of G_c across to rebounded impact velocity range (IV<LCV and IV>HCV) shows interfacial strength highly dependent on separation rate. G_c(IV<LCV) is an order of magnitude higher than G_c(IV>HCV) values. By using the coupling between impact velocity and separation rate, G_c is expressed as a function of separation, which is also useful for understanding optimum cold spray operation velocity for the ideal interfacial bonding.

This work explains the relation between the high strain rate deformation mechanism of PS-b-PDMS and the bonding mechanism of polymer particles by analyzing contact area and the distribution of initial energy to friction, interfacial damage, plastic deformation, and rebound kinetic energy.