Finite element modeling to predict the steady-state structural behavior of 4D textiles

Abstract

Four dimensional (4D) textiles consist of a textile with a printed polymeric grid, where deformation of the grid is induced by introducing residual stresses in the textile, in this case through pre-stretching of the textile substrate prior to printing. The fourth dimension refers to the ability of the structure to change shape over time by changing the residual stress in the textile. In order to design a useful component for a specific application, the material properties of constituents, direction and amount of residual stress, anisotropy of the textile substrate, geometry of the printed polymer, and pattern of the printed grid can all be altered. Due to the large amount of design variables involved, a validated modeling technique that can account for the complex material behavior of the soft, flexible textile under large strains and deformations along with the bifurcation and stability behavior of buckling beams is needed. In this study, an initial model was created to capture the time-independent buckling behavior and compared with experiments for rectangular elements of varying geometry and pre-strain. Once the model was calibrated, it fit experiments well, although additional advancements must be made to predict the nonlinear behavior of a wide variety of architectures with further accuracy. Finally, modeling strategies for large grids are laid out and discussed, and preliminary results are shown. Although this model did not include the transient nature of shape change, it can serve as a precursor for designing 4D Textiles and eventually predicting their time-dependent behavior under loading changes.

4D Printing of Shape Memory Materials for Textiles: Mechanism, Mathematical Modeling, and Challenges

“…The model defines the strain energy density ( U ), with no temperature dependence, which has been shown in Equation (5), where are deviatoric principal components and C i represents the material properties. [ 93 ] …”

“…also developed a simulated finite model to observe the bending of 4D printed textile specimens in the post‐stress conditions. [ 93 ] The geometry, mesh and boundary conditions of this FE model have been demonstrated in Figure .…”

“…Stapleton et al proposed a model that can capture the time-independent buckling property and compare the experimental results derived during the design of rectangular elements that have varied geometries and pre-strains. [93] They printed a knitted fabric with stiffener made from PLA based polymer blend. They used the hyper-elastic model, Yeoh model, to measure the spatial displacement, initial stress, initial strain, and bending and buckled shapes of the textile specimens.…”

“…are deviatoric principal components and C i represents the material properties. [93] ( Stapleton et al also developed a simulated finite model to observe the bending of 4D printed textile specimens in the post-stress conditions. [93] The geometry, mesh and boundary conditions of this FE model have been demonstrated in Figure 19.…”

“…Reproduced with permission. [93] Copyright 2019, Sage Publications. www.afm-journal.de www.advancedsciencenews.com…”