5 Apr 2023

4D Printing Structures for Extreme Temperatures Using Metakaolin Based Geopolymers

Abstract: Geopolymers (GPs) are a class of amorphous, aluminosilicate-based ceramics that cure at room temperature. GPs are formed by mixing an aluminosilicate source, which is metakaolin in this case, with an alkali activator solution, which can be either sodium or potassium water glass. GPs have attracted interest for use in structural applications over the past few decades because they have superior mechanical properties to ordinary Portland cement (OPC). Additionally, they can tolerate much higher temperatures and produce a fraction of the CO₂ compared to OPC. This project aims to develop geopolymer composites for 4D printing (the fourth dimension being time) and test their mechanical properties. Rheology and the effects of curing in ambient conditions will be evaluated for fresh geopolymer. Freeze-thaw resistance will be evaluated on potentially printable composites for extreme temperature resistance, etc.

28 Sep 2021

Synthesis and Characterization of Biological Nanomaterial/Poly(vinylidene fluoride) Composites

Abstract: The properties of composite materials are strongly influenced by both the physical and chemical properties of their individual constituents, as well as the interactions between them. For nanocomposites, the incorporation of nano-sized dopants inside a host material matrix can lead to significant improvements in mechanical strength, toughness, thermal or electrical conductivity, etc. In this work, the effect of cellulose nanofibrils on the structure and mechanical properties of cellulose nanofibril poly(vinylidene fluoride) (PVDF) composite films was investigated. Cellulose is one of the most abundant organic polymers with superior mechanical properties and readily functionalized surfaces. Under the current processing conditions, cellulose nanofibrils, as-received and 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) oxidized, alter the crystallinity and mechanical properties of the composite films while not inducing a crystalline phase transformation on the 𝛾 phase PVDF composites. Composite films obtained from hydrated cellulose nanofibrils remain in a majority 𝛾 phase, but also exhibit a small, yet detectable fraction of 𝛼 and ß PVDF phases.

16 Nov 2020

Magnetorheological Composite Materials (MRCMs) for Instant and Adaptable Structural Control

Abstract: Magnetic responsive materials can be used in a variety of applications. For structural applications, the ability to create tunable moduli from relatively soft materials with applied electromagnetic stimuli can be advantageous for light-weight protection. This study investigated magnetorheological composite materials involving carbonyl iron particles (CIP) embedded into two different systems. The first material system was a model cementitious system of CIP and kaolinite clay dispersed in mineral oil. The magnetorheological behaviors were investigated by using parallel plates with an attached magnetic accessory to evaluate deformations up to 1 T. The yield stress of these slurries was measured by using rotational and oscillatory experiments and was found to be controllable based on CIP loading and magnetic field strength with yield stresses ranging from 10 to 104 Pa. The second material system utilized a polystyrene-butadiene rubber solvent-cast films with CIP embedded. The flexible matrix can stiffen and become rigid when an external field is applied. For CIP loadings of 8% and 17% vol %, the storage modulus response for each loading stiffened by 22% and 74%, respectively.