Enhanced multimaterial 4D printing with active hinges
Enhanced multimaterial 4D printing with active hinges
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DOI：
10.1088/1361-665x/aabe63
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发表时间：
2018-06-01
影响因子：
4.1
通讯作者：
Qi Ge
中科院分区：
文献类型：
--
作者：
Akbari, Saeed;Sakhaei, Amir Hosein;Qi Ge
尽管在四维(4D)打印方面取得了很大进展，即活性(刺激响应)材料的三维(3D)打印，但4D打印结构相对较低的驱动力往往阻碍了它们的工程应用。在这项研究中，我们使用多材料喷墨3D打印技术来制造形状记忆结构，包括变形翼片和可展开结构，该结构由连接刚性(非主动)部件的主动铰链和柔性铰链组成。由形状记忆聚合物(SMP)打印的主动铰链在热机械编程过程中将结构锁定为第二临时形状，而由弹性体打印的柔性铰链有效地增加了如恢复率所反映的打印结构的驱动力和承载能力。通过改变两种基材，即SMP和弹性体的组成，可以为活动铰链和柔性铰链获得广泛的力学性能，如弹性模量和失效应变，以适应编程步骤中产生的大变形，并提高执行步骤中的恢复率。为了找出重要的设计参数，包括局部变形、形状固定度和恢复率，我们进行了高保真的有限元模拟，能够准确地预测印刷结构的非线性变形。此外，还进行了热电耦合有限元分析，模拟了局部焦耳加热过程中主动铰链内的热传递。模型预测结果与实测温度数据吻合较好，并用来寻找影响温度分布的主要参数，包括外加电压和对流速率。
Despite great progress in four-dimensional (4D) printing, i.e. three-dimensional (3D) printing of active (stimuli-responsive) materials, the relatively low actuation force of the 4D printed structures often impedes their engineering applications. In this study, we use multimaterial inkjet 3D printing technology to fabricate shape memory structures, including a morphing wing flap and a deployable structure, which consist of active and flexible hinges joining rigid (non-active) parts. The active hinges, printed from a shape memory polymer (SMP), lock the structure into a second temporary shape during a thermomechanical programming process, while the flexible hinges, printed from an elastomer, effectively increase the actuation force and the load-bearing capacity of the printed structure as reflected in the recovery ratio. A broad range of mechanical properties such as modulus and failure strain can be achieved for both active and flexible hinges by varying the composition of the two base materials, i.e. the SMP and the elastomer, to accommodate large deformation induced during programming step, and enhance the recovery in the actuating step. To find the important design parameters, including local deformation, shape fixity and recovery ratio, we conduct high fidelity finite element simulations, which are able to accurately predict the nonlinear deformation of the printed structures. In addition, a coupled thermal-electrical finite element analysis was performed to model the heat transfer within the active hinges during the localized Joule heating process. The model predictions showed good agreement with the measured temperature data and were used to find the major parameters affecting temperature distribution including the applied voltage and the convection rate.