Thermomechanical properties of polyurethane shape memory polymer–experiment and modelling

Abstract

In this paper extensive research on the polyurethane shape memory polymer (PU-SMP) is reported, including its structure analysis, our experimental investigation of its thermomechanical properties and its modelling. The influence of the effects of thermomechanical couplings on the SMP behaviour during tension at room temperature is studied using a fast and sensitive infrared camera. It is shown that the thermomechanical behaviour of the SMP significantly depends on the strain rate: at a higher strain rate higher stress and temperature values are obtained. This indicates that an increase of the strain rate leads to activation of different deformation mechanisms at the micro-scale, along with reorientation and alignment of the molecular chains. Furthermore, influence of temperature on the SMP’s mechanical behaviour is studied. It is observed during the loading in a thermal chamber that at the temperature 20 °C below the glass transition temperature (Tg) the PU-SMP strengthens about six times compared to the material above Tg but does not exhibit the shape recovery. A finite-strain constitutive model is formulated, where the SMP is described as a two-phase material composed of a hyperelastic rubbery phase and elastic-viscoplastic glassy phase. The volume content of phases is governed by the current temperature. Finally, model predictions are compared with the experimental results.

Influence of the soft segment nature on the thermomechanical behavior of shape memory polyurethanes

“…Figure shows the variation of the storage modulus ( E’ ) and the loss factor, tan δ , as a function of the temperature for all the synthesized polyurethanes, whereas Table summarizes the glass transition temperatures measured from the maximum in tan δ , T g,DMA . The transition around this temperature was ascribed to the glass transition of the hard segment phase . Therefore, as the hard segment content increases, the corresponding glass transition temperature is higher, which is in agreement with the DSC results.…”

Future Prospects: Shape Memory Features in Shape Memory Polymers and Their Corresponding Composites

“…Pieczyska et al [27] have been studied the thermomechanical properties of polyurethane theoretically and experimentally under different mechanical loadings at temperature of 20°C above and below T g at a strain rate of 2 per second within a strain range of 0.6/s. It was observed that when the temperature been slightly dropped, the thermoelastic effect stepped affected.…”

“…True stress-strain curve during loading and unloading of PU-SMP along with thermal images that represented different values of strain[27].…”

Temperature and rate dependent thermomechanical modeling of shape memory polymers with physics based phase evolution law

“…In addition to this dominated thermoviscoelastic approach, in recent years, SMP modeling methods have even incorporated molecular dynamic simulation (Diani and Gall, 2007), quantum mechanics (Zhang et al, 2010), multi-scale modeling (Shojaei and Li, 2013), and statistical mechanics (Shojaei and Li, 2014), etc. Of all these methods, the phase evolution approach, first proposed by Liu et al (Liu et al, 2006) and further developed by other researchers (Baghani et al, 2012;Chen and Lagoudas, 2008a, b;Gilormini and Diani, 2012;Guo et al, 2015;Kafka, 2008;Kazakevic̆iūtė-Makovska et al, 2012;Kim et al, 2010;Long et al, 2010;Pieczyska et al, 2015;Qi et al, 2008;Reese et al, 2010;Scalet et al, 2015;Volk et al, 2011;Wang et al, 2009;Xu and Li, 2010) has become another widely used modeling approach due to its ease of application in design.…”