Characterization of clay composite ballistic witness materials

Mechanical and thermal properties of Roma Plastilina Clay #1 (RP1) were studied through small-amplitude oscillatory shear (SAOS), large-amplitude oscillatory shear (LAOS), and differential scanning calorimetry (DSC), supplemented with thermogravimetric analysis, X-ray diffraction, and X-ray florescence. Rheological characterizations of RP1 through SAOS indicate that the clay composite softens as it is worked and slowly stiffens as it rests. Upon heating, the clay composite softens, prior work history is erased, and the composite undergoes a melting transition, although melted clay is significantly stiffer when returned to the usage temperature. Continuing mechanical characterizations into the LAOS or nonlinear region, RP1 transitions from a transient network to a viscous shear-thinning material as the temperature is increased. Using the MITlaos framework, RP1 exhibits intra-cycle strain stiffening and intra-cycle shear thinning at all temperatures.