On the dynamics of localization and fragmentation: V. Response of polymer coated Al 6061-O tubes

In this series of papers, we investigate the mechanics and physics of localization and fragmentation in ductile materials. The behavior of ductile metals at strain rates of about 4,000–15,000 per second is considered. The expanding ring experiment is used as the vehicle for examining the material behavior in this range of strain rates. In Parts I–III, we examined the response of rings with cross-sectional aspect ratios in the range of 1–10, exhibiting a transition from diffuse necking to sheet-mode localization. In Part IV, we reported on experimental observations of high strain-rate expansion of Al 6061-O tubes. In the present paper, we investigate the effect of polymer coatings on Al 6061-O tubes; specifically, polyurea and polycarbonate coatings are investigated as coating materials. It is demonstrated that there are two effects of the polymer coating on the overall deformation of the Al 6061-O tube specimens. First, the additional mass of the coating material results in an inertial effect; therefore, thicker coatings result in a slower overall expansion and hence for a limited impulse loading, less overall straining of the metallic specimen. Second, the flow resistance of the polymer dissipates additional energy and can prevent failure in the metallic specimen. This effect is much more pronounced in polycarbonate, the material with a larger strength. Finally, it is demonstrated that the polymer coating does not significantly influence the dynamic forming limit of the metallic material.