Collaborative Research: Time Dependent Behavior of Flexible Active Composites

柔性活性复合材料联合收割机结合了聚合物的轻质和耐久性以及压电陶瓷的致动和传感能力。实现活性柔性复合材料的一个实例是通过将铁电陶瓷纤维嵌入均匀聚合物基质中。活性复合材料可用于许多需要复杂3D形状的可控重新配置的工程应用中，例如人造皮肤、可植入和能量收集装置或用于危险环境的柔性机器人等。类似地，耦合行为使它们成为结构健康监测应用的传感器的有吸引力的候选者，即桥梁等民用基础设施中的损伤检测。然而，尽管它们具有巨大的潜力，但当今使用的许多活性复合材料随着时间的推移经历了次优性能以及性能退化。该补助金通过专注于加速开发具有改善的长期性能的柔性活性复合材料所需的基础研究来解决现有的知识差距。此外，PI将专注于推广和教育目标，这将提高未来工程师培训中学习的深度，速度和保留率，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要的工程挑战。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的性质的逐渐变化有关。这项研究将使用综合实验和数值方法来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，以整合不同成分的时间依赖性和机电耦合响应的柔性活性复合材料的整体变形。 此外，这些模型将得到增强，以纳入各种机电载荷条件下的活性复合材料及其组分的非线性特性的逐渐变化。基于这些模型，将加工和表征具有目标改进性能行为的原型复合材料。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，并使此类系统能够广泛用于工程应用。

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.