Automated Robotics Peeling Platform for the Interfacial Adhesion Characterization of Micro-Scale Free Elementary Bio-Based Fibers

Abstract

This article focuses on the development of an experimental platform capable of performing, to the authors' knowledge, for the first time, peeling tests on bio-based fibers. These fibers are very small, their diameters being no larger than a few tens of micrometers, and are not attached to a substrate. The interfacial adhesion forces between elementary fibers have not been quantified and also require quite large motions (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$mm$</tex-math></inline-formula>). To address these challenges, a micro-robotics approach is investigated that combines a micro-gripper, two micro-force sensors, a reduced friction guidance system, and two synchronized micro-positioning stages. This paper presents the operating principle of the robotic platform, its calibration, its measurement protocol and automated experimental tests that quantify, for the first time, the typical magnitude of peeling forces that is of the order of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$10\:mN$</tex-math></inline-formula>, resulting in an interfacial adhesion of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.26\pm 0.13\:mN/mm$</tex-math></inline-formula>. Several experimental tests are conducted on hemp and nettle fibers proving the versatility of the approach. These works also establish a correlation between the microstructure of the fibers and their adhesion strength, opening up to further mechanical analysis of the adhesion mechanisms of plant fibers which are highly interesting for the development of bio-based composites and for the investigation of bio-mimetic principles.