Thesis (M.App.Sc.) - Carleton University, 2009. / Includes bibliographical references (p.117-126). Also available in electronic format on the Internet.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3748. Adviser: Armand J. Beaudoin. Includes bibliographical references (leaves 161-166) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3752. Adviser: Charles L. Tucker, III. Includes bibliographical references (leaves 106-110) Available on microfilm from Pro Quest Information and Learning.

Thesis (M.S.)--Lehigh University, 2009. / Adviser: Richard P. Vinci.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3754. Adviser: Shiv G. Kapoor. Includes bibliographical references (leaves 206-223) Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3756. Adviser: Narayana R. Aluru. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph.D.)--Lehigh University, 2009. / Adviser: Robert P. Wei.

<p> Inspired by the Sandcastle Worm, biomimetic of the water-borne adhesive was developed by complex coacervation of the synthetic copolyelectrolytes, mimicking the chemistries of the worm glue. The developed underwater adhesive was designed for sealing fetal membranes after fetoscopic surgery in twin-to-twin transfusion syndrome (TTTS) and sealing neural tissue of a fetus in aminiotic sac for spina bifida condition.</p><p> Complex coacervate with increased bond strength was created by entrapping polyethylene glycol diacrylate (PEG-dA) monomer within the cross-linked coacervate network. Maximum shear bond strength of ~ 1.2 MPa on aluminum substrates was reached. The monomer-filled coacervate had complex flow behavior, thickening at low shear rates and then thinning suddenly with a 16-fold drop in viscosity at shear rates near 6 s^-1. The microscale structure of the complex coacervates resembled a three-dimensional porous network of interconnected tubules. This complex coacervate adhesive was used in vitro studies to mimic the uterine wall-fetal membrane interface using a water column with one end and sealed with human fetal membranes and poultry breast, and a defect was created with an 11 French trocar. The coacervate adhesive in conjunction with the multiphase adhesive was used to seal the defect. The sealant withstood an additional traction of 12 g for 30&minus;60 minutes and turbulence of the water column without leakage of fluid or slippage. The adhesive is nontoxic when in direct contact with human fetal membranes in an organ culture setting. </p><p> A stable complex coacervate adhesive for long-term use in TTTS and spina bifida application was developed by methacrylating the copolyelectrolytes. The methacrylated coacervate was crosslinked chemically for TTTS and by photopolymerization for spina bifida. Tunable mechanical properties of the adhesive were achieved by varying the methacrylation of the polymers. Varying the amine to phosphate (A/P) ratio in the coacervate formation generated a range of viscosities. The chemically cured complex coacervate, with sodium (meta) periodate crosslinker, was tested in pig animal studies, showing promising results. The adhesive adhered to the fetal membrane tissue, with maximum strength of 473 &plusmn; 82 KPa on aluminum substrates. The elastic modulus increased with increasing methacrylation on both the polyphosphate and polyamine within the coacervate. Photopolymerized complex coacervate adhesive was photocured using Eosin-Y and treiethanolamine photoinitiators, using a green laser diode. Soft substrate bond strength increased with increasing PEG-dA concentration to a maximum of ~90 kPa. The crosslinked complex coacervate adhesives with PEG networks swelled less than 5% over 30 days in physiological conditions. The sterile glue was nontoxic, deliverable through a fine cannula, and stable over a long time period. Preliminary animal studies show a novel innovative method to seal fetal membrane defects in humans, <i>in utero</i>. </p>

<p> Cement based brittle matrix composites that show deflection hardening called high performance fiber reinforced cementitious composites (HPFRCC) have the potential of offering high resiliency and environmentally sustainable benefits in numerous applications. However, more information is needed to fully understand, predict the behavior, and add functionality to HPFRCCs. This experimental research program aims to develop and characterize a new type of HPFRCC. This new HPFRCC is composed of polyvinyl alcohol (PVA) microfibers, carbon nanofibers (CNF), and a high volume of fly ash (HVA) to form a self-consolidating and self-sensing HPRFCC. The multi-functionality of the CNFs allow for increased mechanical properties and strain and damage sensing capabilities. The hybrid fiber reinforced cement composite developed is environmentally sound, due to the large amounts of recycled fly ash, with enhanced stiffness, and tensile strain capacity. This research considers the determination of fresh properties, hardened mechanical properties (elastic modulus, first cracking stress, ultimate stress, and maximum plastic strain), and electrical conductivity of the composite in response to strain, which is measured simultaneously through uniaxial tension tests. Digital Image Correlation (DIC) is used extensively to capture the tensile strain and provide a visualization of the behavior of the composite under increasing displacements. Results from this research program provide a preliminary understanding of the behavior of CNF HPFRCCs, which will aid in future research of similar composites. A standard mixing procedure is established that can be adopted in large scale processing of CNF HPFRCC. Increased mechanical properties and damage detection offers engineers with the ability to quantify structural health and optimize designs. The use of multi-functional self-sensing HPFRCCs is a step towards providing the public with a resilient and sustainable infrastructure for their communities.</p>

<p> Developing light metals that have desirable mechanical properties is always the object of the endeavor of materials scientists. Magnesium (Mg), one of the lightest metals, had been used widely in military and other applications. Yet, its relatively poor formability, as well as its relatively low absolute strength, in comparison with other metals such as aluminum and steels, caused the use of Mg to be discontinued after World War II. Owing to the subsequent energy crisis of the seventies, recently, interest in Mg development has been rekindled in the materials community. The main focus of research has been quite straight-forward: increasing the strength and formability such that Mg and its alloys may replace aluminum alloys and steels to become yet another choice for structural materials. This dissertation work is mainly focused on fundamental issues related to Mg and its alloys. More specifically, it investigates the mechanical behavior of different Mg-based materials and the corresponding underlying deformation mechanisms. In this context, we examine the factors that affect the microstructure and mechanical properties of pure Mg, binary Mg-alloy (with addition of yttrium), more complex Mg-based alloys with and without the addition of lanthanum, and finally Mg-based metal matrix composites (MMCs) reinforced with ex-situ ceramic particles. More specifically, the effects of the following factors on the mechanical properties of Mg-based materials will be investigated: addition of rare earths (yttrium and lanthanum), in-situ/ex-situ formed particles, particle size or volume fraction and materials processing, effect of thermal-mechanical treatment (severe plastic deformation and warm extrusion), and so on and so forth. </p><p> A few interesting results have been found from this dissertation work: (i) although rare earths may improve the room temperature ductility of well-annealed Mg, the addition of yttrium results in ultrafine and un-recrystallized grains in the Mg-Y alloy subjected to equal channel angular pressing (ECAP); (ii) the reverse volume fraction effect arises as the volume fraction of nano-sized ex-situ formed reinforcements is beyond 10%; (iii) nano-particles are more effective in strengthening Mg than micro-particles when the volume fraction is below 10%; (iv) complete dynamic recovery and/or recrystallization is required to accomplish the moderate ductility in Mg, together with a strong matrix-particle bonding if it is a Mg-based composite; and (v) localized shear failure is observed in all Mg samples, recrystallized completely, which is attributed to the reduced strain hardening rate as a result of the exhaustion of twinning and/or dislocation multiplication.</p>