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

该项目的目的是开发三维温度敏感致动器的制造工艺，并根据工艺-结构-性能关系对材料进行全面了解。该项目将使用Arburg塑料自由成型（APF），该技术已被开发用于实施连续玻璃纤维。用于生产温度敏感致动器的现有方法基于例如由镍钛合金制成的形状记忆线（SMW）的手动定位和嵌入。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线的可能性。成形的自由度开辟了更多的可能性，例如由沉积在热塑性基质材料中的曲折SMW组成的致动器的电激活。为此，选择满足机械和热要求的潜在热塑性基质材料，并使其符合APF工艺的要求。从工艺技术的观点来看，复合材料在线材的可加工性方面进行了优化，其中，一方面，确定了最小放电半径的极限，另一方面，旨在使基质材料内的孔隙率最小化。在整个开发过程中，致动器的特点和优化方面的微观结构，准静态和循环机械性能。重点是热机械材料的性能，以估计的激活温度和所产生的致动器的偏转。因此，在确定的材料特性的帮助下，分析模型用于致动器的设计。此外，SMW和基体材料之间的界面强度进行了测量，并通过先前的材料选择和通过适当的表面处理的线增加。通过计算机断层扫描分析验证导丝沿着压力路径的位置，并在必要时进行调整。为了有效地使用SMW，使用优化模型，该模型局部地和完全自动地调整填充内容，以实现给定的变形。在成功开发印刷工艺和机械模型后，设计并制造了一个双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.