Abstract
In situ monotonic tensile experiments of thermo-induced shape memory polyurethane (SMPU) at different loading rates were carried out by the digital image correlation (DIC) method and infrared camera FLIR®-A655sc in natural convection (NC) and forced convection (FC) conditions, respectively. The multiform strain localization of SMPU was observed by the DIC method, and the influence of thermo–mechanical coupling on the strain localization was analyzed by using the FLIR to measure the temperature field caused by the internal heat generation. The experimental results show that the strain localization mode strongly depends on the strain rate and convection condition, and the strain localization mode can be transformed by changing the convection condition from NC to FC. The competition mechanism between the strain hardening induced by the increasing loading rate and strain softening induced by the internal heat generation is indicated, the transition modes of strain localization are clarified, and the influences of thermo–mechanical coupling on shape memory effect are discussed.
Highlights
Thermo-induced shape memory polyurethane (SMPU) is one kind of thermo-sensitive polymer, and the change of its Young modulus in the vicinity of glass transition temperature ranges from two to three orders of magnitude [1,2,3]
In situ observations on monotonic tensile experiments at different loading rates were carried out rate and convection condition on the strain localization were investigated
The main conclusions are in the natural convection (NC) and forced convection (FC) conditions by using the digital image correlation (DIC) and FLIR methods, respectively, the influences of as following: loading(1)rate and convection condition on the localization were investigated
Summary
Thermo-induced shape memory polyurethane (SMPU) is one kind of thermo-sensitive polymer, and the change of its Young modulus in the vicinity of glass transition temperature ranges from two to three orders of magnitude [1,2,3]. The temperature change induced by the internal heat generation and temperature-sensitive mechanical properties of SMPU lead to a strong thermo–mechanical coupling effect during the tensile deformation, which intensifies the complexity of strain localization of SMPU. With the development of measurement technology, in situ observations on the nucleation and propagation of strain localization and the evolution of temperature field during the tensile deformation were carried out by using the digital image correlation (DIC) method and infrared camera FLIR, respectively, which improved the deep understanding of strain localization. Tensile experiments of SMPU at different loading rates were carried out by Pieczyska et al [1], it was found the remarkable temperature rise induced by the strain localization could affect the mechanical and shape memory properties. According to a series of monotonic tensile experiments at different loading rates in the NC condition, the influences of thermo–mechanical coupling effect on strain localization were investigated.
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