Time-resolved spectroscopic characterization of ballistic impact events in polymer and nanocomposite materials

摘要

A detailed understanding of how materials respond to ballistic shock-loading is critical for the design and development of new protective materials. However, the nonlinear viscoelastic deformation present in polymers and nanocomposites during and immediately following a ballistic impact event is not currently well understood. The dynamic mechanical responses of materials experiencing ballistic shock-loading conditions are quite complex, with large amplitude compressions resulting in strain rates in excess of 106 s-1 and pressures exceeding several GPa. Historically, if one wants to study materials under ballistic shock loading conditions, a gas gun apparatus is necessary to generate appropriate high strain rate events. However, advances in high power ultra-fast laser amplifier systems have opened the possibility of optically generating ballistic shocks which are comparable to a shock wave generated by gas gun apparatus. Time-resolved mechanical property information, such as elastic modulus, bulk modulus, shear modulus, and Poisson's ratio are measured using impulsive stimulated thermal scattering, a laser-based photoacoustic technique.