No abstract

This paper presents an experimental investigation on the effect of structural (geometrical) design on the thermomechanical behavior of shape memory polymers. Three beams with identical dimensions (length, width, and thickness), material, and mass, but with different geometrical cells (honeycomb, diamond, and rounded rectangle) are designed by solving a set of nonlinear equations and produced using additive manufacturing method. Then, thermomechanical tests under bending and tensile loading at different temperatures are conducted. As a result, shape recovery and force recovery of the beams, due to the shape memory behavior of the material, are measured. In bending and tensile tests, shape and force recovery results of each beam are compared with their own pre-force and other beams. According to the results, the beam with rounded rectangle cells has the most shape recovery and force recovery ratios (compared to its applied pre-force). Shape recovery for this beam type in bending and tensile tests is 93.03% and 87.86%, respectively. The beam with honeycomb cells requires more pre-force in bending and tensile modes for programming, which leads to a higher maximum force recovery, due to its higher strength.

This paper presents a general semi-analytic solution for the thermomechanical behavior of shape memory polymer (SMP) in large deformation, based on a thermo-viscoelastic constitutive model. The formulation presented in this paper is suitable for describing shape memory behaviors such as fixed-strain, stress-recovery and stress-free, strain-recovery, as well as for multiple shape memory effect in uniaxial and combined extension-torsion problems. To verify the results, a comparison has been carried out among the proposed formulation results and those of experiments and 3D finite element analysis outcomes. Compared to the finite element analysis, semi-analytical solutions are interesting due to their very low computational cost. It was observed that the solution time for the proposed method is much lower than the computational time needed for the FE analyses (around 1%). Therefore, the presented solution can be employed as an efficient tool for examining the effects of changing any of the material or geometrical parameters on smart structures consisting of SMP components under torsion-extension for their design and optimization, which involves a large number of simulations. Additionally, the proposed solution is suitable for calibrating material parameters in both uni-axial and 3D benchmark problem of torsion-extension.

No abstract

No abstract