Collaborative Research: Time Dependent Behavior of Flexible Active Composites

柔性活性复合材料结合了聚合物的轻质和耐用性以及压电陶瓷的驱动和传感能力。实现活性柔性复合材料的一个例子是在均匀聚合物基体中嵌入铁电陶瓷纤维。活性复合材料在许多工程应用中都有应用，这些应用需要对复杂的3D形状进行可控的重新配置，比如人造皮肤、植入式和能量收集设备，或者在危险环境中使用的柔性机器人等等。同样，耦合行为使它们成为结构健康监测应用传感器的有吸引力的候选者，即土木基础设施（如桥梁）的损伤检测。然而，尽管具有巨大的潜力，目前使用的许多活性复合材料的性能都不理想，而且随着时间的推移，性能会退化。该基金通过专注于加速开发具有改善长期性能的柔性活性复合材料所需的基础研究，解决了现有的知识差距。此外，pi将重点关注外展和教育目标，这些目标将提高未来工程师培训中的学习深度、率和保留率，扩大代表性不足的群体在stem相关领域的参与，并提高公众的科学素养。尽管锆钛酸铅（PZT）纤维基复合材料的使用历史悠久，但在理解和预测其行为方面仍然存在重大的工程挑战。这些挑战主要与聚合物和PZT成分的不同频率（速率）相关的滞后响应以及它们在连续循环载荷下性能的逐渐变化有关。这项研究将利用综合实验和数值方法解决这一重要的知识差距，预计将对柔性活性复合材料在关键应用中的可靠性和广泛使用产生积极影响。将建立模型来整合不同成分对柔性活性复合材料整体变形的时间依赖和机电耦合响应。此外，这些模型将被增强，以纳入在各种机电载荷条件下活性复合材料及其成分的非线性特性的逐渐变化。在此基础上，对具有目标改进性能行为的原型复合材料进行加工和表征。了解柔性活性复合材料的加工和寿命性能之间的关系将为制造提供信息，并使此类系统在工程应用中得到广泛应用。

Flexible active composite materials combine the light weight and durability of polymers and the actuation and sensing capabilities of piezoelectric ceramics. One example of achieving active flexible composites is by embedding ferroelectric ceramic fibers in a homogeneous polymeric matrix. Active composite materials find use in many engineering applications that require controllable reconfiguration of complex 3D shapes, such as artificial skins, implantable and energy harvesting devices, or flexible robots for use in hazardous environments to name a few. Similarly, the coupled behavior makes them attractive candidates for sensors for structural health monitoring applications, i.e. damage detection in civil infrastructures such as bridges. However, despite their great potential, many of the active composite materials in use today experience suboptimal performance as well as property degradation over time. This grant addresses existing knowledge gaps by focusing on the fundamental research needed to accelerate the development of flexible active composite materials with improved long-term performance. In addition, the PIs will focus on outreach and education goals that will improve the depth, rate, and retention of learning in the training of future engineers, broaden the participation of underrepresented groups in STEM-related fields and improve the scientific literacy of the public. Despite the long history of the use of lead zirconate titanate (PZT) fiber-based composites, important engineering challenges still remain in understanding and predicting their behavior. These challenges are primarily related to the different frequency (rate) dependent hysteretic responses of the polymers and PZT constituents and the gradual changes in their properties under continuous cyclic loadings. This research will address this important gap in knowledge using an integrated experimental and numerical approach that is expected to have positive consequences on the reliability and widespread use of flexible active composite materials in critical applications. Models will be built to integrate the time-dependent and electro-mechanical coupled responses of the different constituents to the overall deformations in flexible active composite materials. Additionally, these models will be enhanced to incorporate the gradual changes in the nonlinear properties of the active composites and their constituents under various electro-mechanical loading conditions. Based on the models, prototype composites with targeted improved performance behaviors will be processed and characterized. Understanding the relationships between processing and life performance of flexible active composite materials will inform manufacturing and enable wide-spread utilization of such systems for engineering applications.