Development of a Kolsky Bar Shaft-Loaded Blister Test to Evaluate Dynamic Behavior of Adhesives

Adhesive joints are used in a wide variety of applications, ranging from epoxy-set structural anchors in concrete buildings to providing the interface in layered armor plates in military vehicles. With this wide range of applications, adhesive joints experience the full range of strain rates as well, from long-duration creep conditions to high-velocity impact. While research into the delamination behavior of layered materials is common at high strain rates, very little has been done to link this research to the strength of adhesion and interfacial toughness of the constituent adhesive. Adhesion research is common as well; however, few methods have been adapted to evaluate adhesion strength at high strain rates. In this study, a traditional Kolsky bar was modified to employ the shaft-loaded blister technique to increase strain rates. Blister samples were fabricated with an aluminum 6061 substrate and three different polymer coatings: Sylgard® 184, SC-15 epoxy, and a TGDDM epoxy cured with Jeffamine® D230. For each case, sample failure was induced at a quasi-static strain rate before using the Kolsky bar apparatus to examine the failure behavior with an initial shaft velocity of ~5 m/s. The growth of the blister was observed using a high-speed camera for the radial growth, and the height of the blister was determined by the crosshead displacement at the quasi-static load rate and using the strain signals obtained using the Kolsky bar. This technique was successful in observing the adhesive fracture of three different polymers and comparing the failure behavior for the quasi-static load case with that observed at a high strain rate.