Observation of Dynamic Adhesive Behavior Using High-Speed Phase Contrast Imaging

Abstract

Composite sandwich panels provide an increase in buckling resistance to thin composite plates and shells, leading to widespread use in a variety of applications such as boat hulls, rotor blades, and rocket casings. Past research has shown that delamination between the face sheets and core of composite sandwich panels occurs under a variety of both dynamic and quasi-static load conditions. While this failure mechanism has been identified and observed, existing research has not fully investigated the mechanisms behind this adhesive failure. In this study, a carbon fiber bar was adhered using JB Weld epoxy to a variety of substrates. Bulk polymer substrates included polycarbonate, ultra-high molecular weight polyethylene, and Delrin®, while two PMI foam substrates were used: Rohacell® WF200 and Rohacell® HERO200-HT. Experiment samples were impacted using a Kolsky bar apparatus to impart simple shear on the adhesive joint. The adhesive joint was observed in-situ using a synchrotron X-ray source in phase contrast imaging mode. The X-ray source was used in tandem with the Kolsky bar and high-speed camera. In order to introduce simple shear in the adhesive joint, the Kolsky bar was used to impact the carbon fiber bar with an impact velocity of ~7 m/s. Adhesive failure was observed in each of the bulk polymer samples, but no failure was seen in the PMI foam samples.