EAGER: Measurements of Soft Bi-material Interface Behaviors under Dynamic Loading Conditions

North Carolina State University, Raleigh NC

Investigators

Abstract

Thin polymer films are widely used in flexible electronics and soft robotics. The durability of these thin polymer film interfaces is critical to their long-term performance. A thorough understanding of the properties of these films is also important in microelectronics fabrication where nanostructured polymer thin film patterns are used to fabricate complex circuitry. As production rates for these processes increase, an understanding of the dynamic performance of these thin film patterns becomes more and more critical. This EArly-concept Grant for Exploratory Research (EAGER) award supports fundamental research to create a new experimental technique to measure the properties of material property gradients in polymer thin films under dynamic loading conditions. This research will generate critical experimental data on material property gradients and interface conditions under dynamic loading conditions. This data can be used for the enhancement of computational modeling of these material systems and enable the design of new multi-layer film systems. Insight from this research will also drive new fabrication strategies to enhance the long-term performance of engineered flexible components. Enhancements to their performance would directly impact the nation's soft robotics, manufacturing and healthcare systems by enabling more durable devices for skin mounted sensors and flexible robots. This project will provide opportunities to educate and train graduate students in advanced experimental techniques that could be applied across many engineering fields. The project will also impact undergraduate education through research experiences for undergraduates with a focus on underrepresented students. The performance of thin polymer films and multi-layer films depends highly on the gradient of material properties through the thickness of the film. These properties are altered relative to the bulk polymer material due to chemical interactions with the substrate and geometrical confinement. Similarly, the failure and dynamic behavior of polymer-matrix based composites is often dominated by the interface/interphase properties between the reinforcement and the matrix materials. This research aims to implement, demonstrate and evaluate a novel acoustics based experimental technique for the simultaneous measurement of stress-strain behavior gradients through the thickness near soft, bi-material interfaces and adhesion properties at these interfaces. Two specific material systems will be addressed, polymer thin films and the interphase region in polymer-matrix composites. Material property data will be collected over a wide range of dynamic loading conditions. The outcome of this research will be a new experimental method for mechanics researchers to more accurately determine property variations in the thickness directions for thin-film and interphase specimens by significantly reducing the effects of the local interface conditions and the substrate material. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.