PhD.Thesis Dissertation:Melike Nur Önder

DESIGN AND FABRICATION OF A GRAPHITE

ENHANCED PVA/GNP COMPOSITE PIEZORESISTIVE INK

Melike Nur Önder
Materials Science and Nano Engineering, PhD Dissertation, 2023

Thesis Jury

Prof. Mehmet Ali Gülgün (Thesis Advisor),

Prof. Selmiye Alkan Gürsel

Assist. Prof. Murat Kaya Yapıcı

 Assoc. Prof. Canan Dağdeviren

Assoc. Prof. Yiğit Dağhan Gökdel

Prof. Melih Papila (Co-Advisor)

Date & Time: 28th, 2023 –  17:00

Place: L055

https://sabanciuniv.zoom.us/j/7744518925

Keywords : piezoresistive, composite piezoresistor, resistivity, structural health monitoring

Abstract

Polymer matrix composite piezoresistors often suffer from unreliable and inconsistent piezoresistive responses, which  can be challenging to minimize or eliminate, particularly under extended cycling loading. This limitation significantly impacts their applicability. The use of carbon-based nanoparticles has long been of interest in the development of composite piezoresistive sensors. It is well-established that the combination of nanofillers and binder has a significant impact on the electronic and mechanical properties of piezoresistors. To tune the composite characteristics, multiple filler types can be used and/or the proportions of the constituents can be adjusted. In this study, a nanocomposite piezoresistor was introduced, which was enhanced with graphite particles (GPs) and graphene nano platelets (GNPs) in polyvinyl alcohol (PVA). The aim was to explore and utilise the synergy between GPs and GNPs. The role of the GPs is to create the backbone for conductive paths, reducing variation in formation from one cycle to another. The GNPs, on the other hand, enhance the piezoresistive effect of the nanocomposite piezoresistor. Various filler ratios of the GPs were examined, along with their synergy with the GNPs. By serving as the backbone for conduction, the GPs prevent sensitivity loss under cycling loading. Cycling tests (30 cycles) showed consistent and repeatable gauge factor, ensuring linear response to applied strain. The language used is clear, objective, and value-neutral, with a formal register and precise word choice. The text adheres to conventional structure, with clear and concise sentences and a logical flow of information. The grammar, spelling, and punctuation is correct. Cycling tests (30 cycles) showed consistent and repeatable gauge factors, ensuring linear response to applied strain. The piezoresistor was produced in ink form, allowing for easy application with a spatula or brush onto a substrate. This method provides structural health monitoring of materials. Our study used acetate paper and plexiglass as carriers. No changes in content were made.  The data were collected using a circuit design based on an Arduino microcontroller and evaluated with an algorithm to predict material failure. The study examined the response of the material under cycling loading, as determined by the resistance change of the composite piezoresistor. The data were collected using a circuit design based on an Arduino microcontroller and evaluated with an algorithm to predict material failure. The data were collected using a circuit design based on an Arduino microcontroller and evaluated with an algorithm to predict material failure.