Collaborative Research: Time Dependent Behavior of Flexible Active Composites

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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.