Effect of temperature and strain-rate on mechanical properties of thermoplastic polyurethane interlayer

Chemically strengthened glasses (CSG) are used nowadays in transparent polymeric laminates to develop windshields for airplanes and high-speed trains and in transparent armor system. Thermoplastic polyurethane (TPU) is used as interlayer material currently for better windshield structural survivability and absorb impact loads and shattered debris of strengthened glass. In this paper, the uniaxial-tensile tests on TPU are performed at three different strain-rates (0.052 s^-1, 0.1 s^-1 and 0.5 s^-1) and at 5 different temperatures viz., (-40 °C, -20 °C, 0 °C, +20 °C and +40 °C) using Instron 5849 testing machine. The environmental chamber was designed to analyze the effect of temperature with a constant loading rate of machine crosshead. As the TPU undergoes large deformation during the tensile loading process, digital image correlation (DIC) set-up was also incorporated to accurately capture the real-time displacement and strain distribution. From test data the key mechanical properties at different loading rated and temperatures determined. The experimental results showed the significant rate-sensitivity to loading-rate, and temperature. The test results obtained with DIC technique will be helpful to accurately develop the nonlinear viscoelastic constitutive material models to simulate the impact events and improve the structural reliability of windshields for aircraft and high-speed trains and transparent armor.