Characterizing and modeling the free recovery and constrained recovery behavior of a polyurethane shape memory polymer

Abstract

In this work, tensile tests and one-dimensional constitutive modeling are performed on a high recovery force polyurethane shape memory polymer that is being considered for biomedical applications. The tensile tests investigate the free recovery (zero load) response as well as the constrained displacement recovery (stress recovery) response at extension values up to 25%, and two consecutive cycles are performed during each test. The material is observed to recover 100% of the applied deformation when heated at zero load in the second thermomechanical cycle, and a stress recovery of 1.5 MPa to 4.2 MPa is observed for the constrained displacement recovery experiments. After performing the experiments, the Chen and Lagoudas model is used to simulate and predict the experimental results. The material properties used in the constitutive model – namely the coefficients of thermal expansion, shear moduli, and frozen volume fraction – are calibrated from a single 10% extension free recovery experiment. The model is then used to predict the material response for the remaining free recovery and constrained displacement recovery experiments. The model predictions match well with the experimental data.

Cyclic and monotonic testing of free and constrained recovery properties of a chemically crosslinked acrylate

“…At high temperatures, the final stress is in good agreement with the material stress–strain response at the same temperatures. Figure is in accordance with previous results that showed cyclic independency for the constrained recovery of a polyurethane network pre‐strained in the rubbery state . Moreover, such results were expected in regards of the material behavior repeatedly recorded at 65°C over the cycles (Figure ).…”

Predicting shape memory characteristics of polyurethane in three-point bending deformation

“…clearly indicates that the shape recovery starts approximately at 357 K for all samples with different predeformations, which means that the micro‐motion is not affected by predeformation. By comparing Volk's work described in Figure 12 of Reference and above mentioned results in this paper, we can confirm that the deformation level has little influence on the temperature starting to recover.…”

Recovery performance and characteristics in shape memory effects of aliphatic polyether urethane

“…c, the recovery occurs at the same temperature about 76°C, regardless of the applied strain values. This result is in correspondence with the work of Maitland et al . And, the aforementioned results demonstrate the dependence of the recovery performance on time and temperature.…”

“…The simulations of SMPs were conducted by Tobushi et al ., Wang et al ., Liu et al ., Qi et al ., and Diani et al ., modeling the SMPs thermomechanical behaviors in constrained or unconstrained recovery situations. Maitland et al . especially performed tensile tests and one‐dimensional constitutive modeling of a shape memory polyurethane with high recovery force and numerically analyzed the SMEs by means of the Chen and Lagoudas model, which is based on phase transition theory.…”