Abstract

The shape memory alloy-shape memory polymer (SMA-SMP) composite actuators are the novel smart actuator designs which capable of large recoverable actuation deformation as well as retaining shape in the actuated state without consuming extra energy. This is particularly doable because of the recent progresses in additive manufacturing technologies. The 4D printed actuators designed in the previous study [7] are fabricated by multi-material inkjet 3D printing and is able to deposit various range of digital materials with different elastic stiffness in micro-scale. In this study, we have developed the numerical simulation of the 4D-printed composite actuator hinges to determine important actuation parameters and develop a design tool for future applications. The three-dimensional finite element models were conducted in ABAQUS and the nonlinear temperature dependence behaviour of shape memory alloy (SMA) and shape memory polymer (SMP) materials are incorporated through the user material subroutines (UMATs). The finite element results then have been compared with the experimental measurements and illustrate the accuracy of our numerical analysis. Therefore, the validated computational framework could be used for further development of actuators that could generate complex deformations.

Abstract

The term “4D Printing” (4DP) is defined as the ability for a part produced using an additive manufacture process to change its shape when activated by or exposed to one or more stimuli over time. This emerging technology offers unique advantages over conventional Additive Manufacturing (AM) by extending the three dimensions of space into the fourth dimension of time. 4DP parts can be programmed to actuate passively without the need for an external power source such as an electromechanical or other active system, thereby reducing the probability of failure and the complexity of components. This work attempts to address some of the challenges faced by the design engineer in a project team when producing technical documentation to specify the desired shape transformation of a 4DP part with a structured graphical representation at an appropriate level of abstraction. In this paper the requirements for a shape transforming 4DP part are represented as the allowable variation in dimensional size and tolerance in geometric form of the functionally critical features on the part for each function that the transformed shape serves. In this paper, the authors describe how the proposed standard to specify the desired shape transformations of a 4DP part could use graphical symbols in a structured specification by means of a Transformation Control Frame (TCF) to define the rules of transforming between shapes and a Bill of Transformations (BoT) to enumerate all the Transformation Control Frames (TCF) necessary to describe the intended sequence of shape transformations. To illustrate how the graphical symbols could be applied, a SMA actuated gripper is presented as a use-case.