ABSTRACT
Evaluation of dynamic compressive fracture for advanced structural materials like ceramics and polymers is essential for developing high strain rateresistant structures. Performances of the individual components present in a composite structure control the overall efficiency during its field application. That is why, it is indeed necessary to take care of the characteristically brittle microstructure of the ceramics in general and alumina in particular. Recently, polycrystalline alumina is found to be used extensively in dynamic load-bearing applications. Hence, an idea for developing a smarter design by introducing a weak interface between the two monolithic alumina ceramic disks was evolved to deflect and/or arrest the cracks to enhance their failure times. Thus, specimens of monolithic ceramics and ceramicpolymer-layered composites were developed from commercial alumina and an appropriate polymer. They were subsequently exposed to high strain rate (e.g., 103 s−1) impact tests using a split Hopkinson pressure bar (SHPB)
apparatus in association with in-situ high-speed real-time videography. The maximum compressive strength for monolithic alumina was ~3 GPa and that for layered structure was slightly higher, for example, ~3.2 GPa. Time to reach the maximum compressive strength from impact for monolithic alumina and the layered structures were 35 and 55 µs, respectively. In addition, to understand the deformation behavior of brittle polymers and reinforced polymers, the polymethyl-methacrylate and glass fiber-reinforced polymer samples were also examined in high strain rate SHPB experiments. The yield strengths of these two polymers were highly sensitive to variations in strain rate. Postmortem examinations of the fragmented specimens were performed by field emission scanning electron microscopy and transmission electron microscopy. Based on these experimental data, some new failure mechanisms were proposed for these materials.
