Cold spraying on polymer-based composites: Understanding the single-particle adhesion

Abstract

The metallization of the polymer matrix composite structures arises from the need to overcome some of the limits of the polymer-based materials, such as poor thermal and electrical conductivity. The cold spray technology has proved to be one of the most valid solutions for this scope. While the adhesion mechanisms of metal particles on metallic substrates are quite well known, the phenomena occurring when cold spraying on polymers are far to be understood. In this scenario, this paper proposes an interpretation of the phenomena leading to adhesion in cold spraying of metal particles onto polymer-based substrates, including composites. The aim is to try to unveil the phenomena ruling the adhesion by proposing a theoretical model conceived by conjecturing the phenomena occurring. The main hypothesis is that the adhesion is influenced by several energy-activated phenomena: the plastic deformation of the polymer, the plastic deformation of the particles and the loading of the fibers are conjectured to be the most influencing factors. So, the idea is to try to identify the most likely to occur phenomena based on an energy balance. A theoretical model is developed and validated through a dedicated experimental campaign to verify the effectiveness of the model to provide sufficiently reliable results. The model is applied to literature cases and the outcomes obtained are discussed to elucidate the adhesion mechanisms and the role of the fibers in fiber-reinforced polymers.