4D printed anisotropic structures with tailored mechanical behaviors and shape memory effects

Four-dimensional (4D) printing as a new generation additive manufacturing of smart materials has shown great potential for the intelligent development of multi-functional and customized structures. The microarchitecture design of printing infill patterns could bring flexible and diversified structural performances by combining the geometry design, thus opening up more possibilities for practical application. This work investigates the anisotropic characteristics of mechanical and shape memory performances induced by different infill strategies via both experimental and theoretical methods. Uniaxial tensile tests and compressive tests are performed to study the effect of infill patterns on mechanical properties. Both classical laminate plate theory and honeycomb equivalent modulus theory take into account the actual shape and dimensions of printed cross-section to improve the prediction accuracy. The viscoelasticity of each printing pattern is described by generalized Maxwell-Wiechert model and Prony Series are fitted to provide references to implement in Abaqus. With the purpose of exploring the shape memory properties including recovery speed, recovery ratio and shape fixity ratio, deformation-recovery tests are conducted under different temperatures and a 2D and 3D convertible structure with programmable Poisson's ratio are demonstrated. This work may potentially provide pattern design guidance for 4D printing structures to meet different application requirements.