Towards Visually Observing Viscoelastic Behavior in Polymer Cold Spray Using Ultra High-Speed Videography

The research presented herein proposes an experimental methodology to resolve high strain rate polymer deformation characteristics at scales relevant to cold spray particle impacts. Macro-scale (~ 3 mm) polymer impact testing via a light gas gun has shown evidence of cold spray indicative features at certain (material, particle/substrate temperature, velocity, etc.) conditions [1]. Ultra-high-speed video capture used in macro impact experiments has proven sufficient for resolving deformation characteristics and observing viscoelastic properties that are not evident when examining post-impact particles. The presence of cold spray features and ability to resolve viscoelastic behavior at the macro scale suggests that similar insight could be gained at cold spray scales. Macro-particle launching and videography techniques are adapted to observe micron-scale single particle impacts to provide an alternative approach to stroboscopic imaging, allowing for examination of impact deformation characteristics. Examination of viscoelastic behavior nearing cold spray scales informs experimentation beyond spray density and deposition efficiency traditionally used to qualify spray parameters. This approach provides insight into understanding adhesion and deposition mechanisms in polymer cold spray by observing single particle deformations with control over spray conditions beyond alternative imaging methods. [1] Bacha et al, 2024. Manuscript in progress.