| The need for more maneuverable and rapidly deployable combat systems, with enhanced combat responsiveness and superior fighting capabilities, has been vividly demonstrated in recent overseas military operations. This has placed renewed demands on new and improved lightweight, highly damage-tolerant armor materials. The US Army is contemplating to use synthetic heterogeneous systems, e.g. layered composite materials with organic matrices reinforced by glass fibers (GRP), to achieve lightweight and enhanced ballistic resistance for future combat vehicles and structures. However, while the dynamic response of homogeneous materials, such as metals and ceramics, has been well documented, the ballistic response of heterogeneous material systems is poorly understood.; In an attempt to better understand the dynamic response of heterogeneous materials such as GRP, a combined analytical and experimental study is conducted on elastic/elastic and elastic/viscoelastic bilaminates to simulate the effects of layered structure of GRP on shock wave propagation. The analytical approach makes use of the Laplace transform and Floquet theory for ODE with periodic coefficients. The experiments were conducted using the single-stage 82.5mm bore gas gun facility at CWRU. The effects of material impedance mismatch, layer density and material inelasticity on shock wave propagation through elastic/elastic and elastic/viscoelastic bilaminates were studied.; Besides the study on bilaminates, several series of plate impact experiments were performed on GRP. By varying the shock compression stress and GRP specimen thicknesses, the effects of shock compression and propagation distance on the structure of shock waves in GRP were investigated. From the measurements of the free surface particle velocity history, the Equation of State (EOS), Hugoniot Elastic Limit (HEL), and Hugoniot curve of GRP were determined.; The spall strength of GRP was also studied by conducting a series of both normal impact and combined pressure-shear plate impact spall experiments. The GRP's spall strength was found to decrease dramatically with increasing compression stress and increasing shear strain. Shock-reshock and shock-release experiments were performed from shock Hugoniot states of 1.0 GPa and 2.0 GPa to determine the dynamic yield strength of GRP. The calculated dynamic yield strength was found to increase by approximately a factor of 10 within the test range. |
