| Polymers and polymer matrix fiber-reinforced composites are often used at temperatures that lead to time-dependent material behavior. Such behavior needs to be sufficiently understood and accounted for to ensure adequate design in critical fields such as the aircraft industry. This thesis considers the behavior caused by physical aging, which is the evolution towards equilibrium in glassy solids, and its effect upon the mechanical response of viscoelastic polymers.; The physical aging behavior of polymers is characterized by a compliance function, obtained under creep loading, and its relationship to a reference compliance function. The two functions become similar when one is horizontally shifted (in the time scale) the associated shift factors describe the effect of physical aging during a specified time-temperature history. The physical aging response of a polycarbonate film under both isothermal and non-isothermal temperature histories is studied. The shift factors obtained in this thesis compare favorably with the results from previous works in this area. (Abstract shortened by UMI.)... |
