MechE PhD Dissertation Defense: Sanika Barve

TITLE: FUNCTIONAL DEFORMATIONS IN THIN SHEETS AND TEXTILES

ABSTRACT: Shape-shifting mechanisms are ubiquitous in nature and society. These elastic in-stabilities, specifically in slender structures, enable large, functional deformations and contorsions. In recent years, techniques like kirigami and origami, the japanese arts of paper cutting and folding, have been extensively utilized to achieve 3-dimensional geometries from 2-dimensional materials and tune effective material properties. Sim-ilar to cuts and folds, torsional deformations are frequently employed in structural design. Twisted deformations store strain energy and are regularly used to construct ropes, cables, and fabrics. These strategic deformations in sheets and textiles can be used to engineer tools ranging from multi-functional soft robotic graspers to centuries old load bearing textile structures. Here, we design and experimentally explore the structure and function of kirigami fluid mixers and head-carrying textile rings. In the first half of this thesis, we discuss the development of a soft, scalable, biocompatible, and packable mixing mechanism composed of a kirigami end-effector connected in series with an origami actuator. The kirigami end-effectors consist of a co-linear cut pattern on a thin elastic shell with varying appendage shapes and the origami actuators are made of a rigid skeleton component sealed within a thin elastic sleeve. We determine the load and displacement requirements for end-effector closure and design requirement-specific, fluid-driven origami actuators by varying skeleton hinge parameters. We evaluate and demonstrate the mixing efficiency of these mech-anisms through experimentation and confirm our results with image analysis. These kirigami end-effector - origami actuator mechanism units have versatile applications ranging from fluid and granular mixing to grasping objects of differing stiffness and shape. In the second half of this thesis, we investigate the mechanics of multi-functional head-carrying textile rings. Throughout human history, the practice of using textile rings to facilitate the transport of goods (e.g. pots of water; harvested produce) atop the head has surfaced in cultures spanning vast time scales and geographic length scales. This technique is still used today predominantly by women in rural, agri-cultural communities. Textile rings are often fabricated by bending, twisting, and wrapping readily available materials (e.g. natural fibers in a plain weave), to form structures that distribute complex loads and conform to arbitrarily shaped objects. In this work, we study the mechanics of textile rings constructed from different fabrics and different wrapping strategies. We examine the effects of material (i.e. weaving pattern, fabric composition) and design (i.e. twists, folds) on the stiffness, conforma-bility, and behavior of textile rings under quasistatic loading conditions that mimic head-porting. We find that ring stiffness increases with the number of twists result-ing in more rigid designs with low conformability which is favorable for transporting heavy, rigid objects, i.e. large pots of water or stacks of bricks. Softer ring designs exhibit increased conformability, which is preferable for carrying and stabilizing non-uniform loads with shifting load distribution, i.e. sack of grains or bundles of sticks. These findings provide a mechanistic understanding of head-carrying textile rings and illustrate the mechanical intuition and human ingenuity that enable women to carry up to 60% of their body weight atop their head.

COMMITTEE: ADVISOR Professor Douglas Holmes, ME/MSE; CHAIR Professor Gregory McDaniel, ME/MSE; Professor Paul Barbone, ME/MSE; Professor Sheila Russo, ME/MSE; Professor Abigail Plummer, ME/MSE