Strain induced anisotropic properties of shape memory polymer

Heat activated shape memory polymers (SMPs) are increasingly being utilized in ambitious, large deformation designs. These designs may display unexpected or even undesirable performance if the evolution of the SMP's mechanical properties as a function of deformation is neglected. Yet, despite the broadening use of SMPs in complex load bearing structures, there has been little research completed to characterize how the material properties change upon application of large strain. The following is an experimental investigation into the strain induced anisotropic properties of the SMP Veriflex®. It is found that under large uniaxial strain the SMP's stiffness in the transverse direction can be reduced as much as 86%, while the toughness in the axial direction may increase by an order of magnitude in some cases. A generalized analysis suggests that this trend should be expected for any SMP.

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