Additively manufactured temperature sensitive actuators made of shape memory wire reinforced polymer structures

该项目的目的是开发一种三维温敏致动器的制造工艺，并根据工艺-结构-性能关系对材料进行全面的理解。在该项目中，将使用Arburg塑料自由成形(APF)，该技术已经开发用于实现连续玻璃纤维。现有的制造温敏致动器的方法是基于例如由镍钛合金制成的形状记忆丝(SMW)的手动定位和埋入。因此，这些制造策略制造起来相对复杂，并且不提供在弯曲结构中沉积导线的可能性。成型的自由开辟了更多的可能性，例如由沉积在热塑性基质材料中的蜿蜒SMW组成的致动器的电激活。为此，我们选择了满足机械和热要求的潜在热塑性树脂基材，并使其符合APF工艺的要求。从工艺技术的观点来看，复合材料针对线材的可加工性进行了优化，从而一方面确定了最小放电半径的限制，另一方面以最小化基质材料中的孔隙率为目标。在整个开发过程中，对执行器的微观结构、准静态和循环力学性能进行了表征和优化。重点放在材料的热机械性能上，以估计激活温度和由此产生的致动器的挠度。因此，在所确定的材料属性的帮助下，分析模型被用于执行器的设计。此外，还测量了SMW与母材之间的界面强度，并通过先前的材料选择和适当的表面处理提高了SMW与母材的界面强度。钢丝沿压力路径的位置通过计算机断层分析进行验证，并在必要时进行调整。为了有效地使用SMW，使用了一种优化模型，该模型局部地并完全自动地调整填充内容，以便实现给定的变形。在成功开发了印刷工艺和机械模型后，设计并制造了两指夹持器形式的功能演示器，以完成项目。

The aim of the project is to develop a manufacturing process for three-dimensional temperature-sensitive actuators and to generate a comprehensive understanding of the material based on the process-structure-property relationships. For the project, the Arburg plastic freeforming (APF) will be used, which has already been developed for the implementation of continuous glass fibers. Existing methods for the production of temperature sensitive actuators are based on the manual positioning and embedding of shape memory wires (SMW) made e.g. of nickel-titanium alloys. These manufacturing strategies are therefore comparatively complex to manufacture and do not offer the possibility of depositing wires in curved structures. The freedom in shaping opens up further possibilities, such as the electrical activation of an actuator consisting of a meandering SMW deposited in a thermoplastic matrix material. For this purpose, potential thermoplastic matrix materials which fulfil both the mechanical and thermal requirements are selected and qualified for the APF process. From a process-technical point of view, the composite is optimized with regard to the processability of the wire, whereby, on the one hand, limits of the minimum discharge radius are determined and, on the other hand, the minimization of porosities within the matrix material is aimed at. During the entire development process, the actuators are characterized and optimized with regard to their microstructure, quasi-static and cyclic mechanical properties. The focus is on the thermomechanical material properties to estimate the activation temperature and the deflection of the resulting actuators. Therefore, an analytical model is used for the design of the actuator with the help of the determined material properties. In addition, the interfacial strength between SMW and matrix material is measured and increased both by the previous material selection and by suitable surface treatment of the wire. The position of the wire along the pressure path is validated by computed tomographic analyses and adjusted if necessary. For an efficient use of the SMW, an optimization model is used which adjusts the filling content locally and fully automatically in order to achieve a given deformation. After successful development of the printing process and the mechanical models, a functional demonstrator in the form of a two-finger gripper is designed and manufactured to finalize the project.