Most reports simulating in-flight particle temperatures in polymer cold spray ignore intra-particle thermal gradients that develop in-flight, and, to date, no research group has simulated the effects of thermal gradients on polymer particle impact dynamics. This report investigates the effects of intra-particle thermal gradients on the impact response of thermoplastics, using properties of polyether-ether-ketone (PEEK) in a simulated like-on-like cold spray deposition process. Particle velocities and internal temperatures are calculated from compressible flow models of the spray process under several heat transfer assumptions. The commonly used lumped thermal capacitance assumption differs in average particle impact temperature by over 70 °C from simulations involving a more physically representative thermal gradient model assuming finite-rate heat conduction. Additionally, the intra-particle temperature differences of over 100 °C in some particles imply significant variation in material properties within a particle. The predicted average temperatures and temperature gradients are used as initial conditions for a finite element-based impact model that shows distinct mechanical responses of isothermal and thermally graded particles. These results suggest that thermal gradients in polymer particles should be considered for further refinements of model-based predictions for the cold spray of polymers and optimized by process design.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces, Coatings and Films
- Materials Chemistry