Switchable and Tunable Multifunctional Attributes of Soft Composites

Abstract

This study investigates how the transforming material architecture of two soft composite material systems enables new functionalities or improve the performance of existing ones. The objective of the study of the first composite system, is to investigate the potential of high performance nano-architectured fiber reinforced composites for high strength applications such as in aerospace and automotive industries. In this respect, pull-out capacity of 3D printed millimetre scale prototypes were experimentally and computationally investigated. Cylindrical multi-material prototypes consisting of a fiber embedded in a soft matrix are considered herein. Embedded fiber has tiny orderly spaced geometrical features (fins) on its circumference over the bond length. Both fiber and fins are made of the same polymeric material with a higher stiffness than the soft surrounding polymer-matrix. Pull-out performance of the prototypes were experimentally and computationally evaluated and it was found that the system with geometrically engineered fins on the fiber exhibit a higher load carrying capacity of up to 62 %, and an increased effective interface stiffness of up to 65 %, compared to those of a system with no fins. The second composite system is a novel switchable and tunable optical device meant for dynamically controlling the optical transmittance, through mechanical shearing, with application potential in smart windows for daylight and climate control. Experiments and finite element (FE) simulations were performed to evaluate the potential of the composite system, both with respect to transmittance modulation range and operational energy demand. Experimental prototypes were fabricated at the centimetre-scale using both 3D printing and casting methods, and comprised an array of opaque platelets embedded in a transparent hyperelastic matrix. Shearing the boundaries induces rotation of the embedded platelets for transmittance modulation. Results show a potential increase in modulation range of 22.6 % and a potential decrease in operational energy demand of 92 %, compared to commercial smart windows. Furthermore, a new simple test method is proposed and utilized to accurately measure the average uniaxial strain for mechanical characterization of hyperelastic polymers, without the use of an extensometer.

Date of Award	May 2015
Original language	American English
Supervisor	Kumar Shanmugam (Supervisor)