Development of multi-layered graded density Cu/PMMA for controlled stress and strain rate behavior

In gas gun experiments, the research on material phase transitions under quasi-isentropic loading is limited by the accuracy of graded density impactor (GDI) fabrication. Six types of GDIs of copper (Cu) and polymethyl methacrylate with different interlayer thicknesses and numbers are prepared by the processes of melt mixing and multi-step hot pressing. The interlayer minimum thickness is 50 μm, and the graded impactors are free of intermetallic compounds with excellent interlayer parallelism and flatness, offering considerable preparation accuracy. The GDIs are launched into a stationary LiF target using a one-stage light gas gun at an impact velocity of 500 m/s with the measured target stress threshold from 1.58 to 3.28 GPa. The wave interaction analysis indicates that by varying the types of GDI structures, shock waves and reflected waves during the shocking process are influenced, resulting in independent control of the magnitude and oscillation amplitude of the strain rate in the range of 105 s−1, achieving precise control of the strain rate. Holding significant interest for researching the dynamic response of materials under gas gun loading with stress and strain rate controlled.