A constitutive theory for shape memory polymers. Part I

On modeling shape memory polymers as thermoelastic two-phase composite materials

“…This study has addressed one point that was left open by Chen and Lagoudas [16] about combining the model of Liu et al [14] with homogenization models that would be more accurate than the uniform stress assumption. This has been performed in the limited framework of linear small-strain elasticity.…”

“…The type of φ(T ) function, which defines the change in the volume fractions of rubbery and glassy phases, can be modified conveniently, and the experimental reference curve used to fit φ(T ) can also be varied. The model restricts to small deformations, but extension to finite strain can be contemplated now by adapting the Chen and Lagoudas [16] approach to the uniform strain hypothesis that has been shown here to be appropriate.…”

“…This also implies that the ε s history must be recorded. More precisely, it is sufficient to store dε s /dT for the "net cooling history" as defined by Chen and Lagoudas [16], i.e. for negative temperature increments that have not been compensated yet by positive increments between T + and the current temperature.…”

“…An encouraging agreement was found with experiments, which confirmed that a thermoelastic model is able to capture the basic stress and strain evolutions. Extensions of the model to finite strain were proposed by Diani et al [15] and by Chen and Lagoudas [16], who also provided a small-strain version (Chen and Lagoudas, [17]). The original small-strain model of Liu et al [14] has also been revisited by Wang et al [18], who proposed a first combination of the model with the theory of composite materials.…”

Thermally actuated shape-memory polymers: Experiments, theory, and numerical simulations

“…Significant modeling efforts have also been published (e.g., Liu et al, 2006;Chen and Lagoudas, 2008;Qi et al, 2008;Nguyen et al, 2008). However, at this point in time, a thermo-mechanicallycoupled large-deformation constitutive theory for modeling the response of thermally-actuated shape-memory polymers is not widely agreed upon -the field is still in its infancy.…”