WorldCat Identities

Sottos, Nancy R.

Overview
Works: 61 works in 88 publications in 1 language and 573 library holdings
Genres: Conference papers and proceedings 
Roles: Editor, Author
Publication Timeline
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Most widely held works by Nancy R Sottos
Experimental and applied mechanics : proceedings of the 2014 Annual Conference on Experimental and Applied Mechanics by Nancy Sottos( )

10 editions published between 2014 and 2016 in English and held by 315 WorldCat member libraries worldwide

Experimental and Applied Mechanics, Volume 6: Proceedings of the 2014 Annual Conference on Experimental and Applied Mechanics, the sixth volume of eight from the Conference, brings together contributions to important areas of research and engineering. The collection presents early findings and case studies on a wide range of topics, including: Advances in Residual Stress Measurement Methods Residual Stress Effects on Material Performance Inverse Problems and Hybrid Techniques Thermoelastic Stress Analysis Infrared Techniques Research in Progress Applications in Experimental Mechanics
Adaptive material systems : presented at the 1995 Joint ASME Applied Mechanics and Materials Summer Meeting, Los Angeles, California, June 28-30, 1995( Book )

4 editions published in 1995 in English and held by 63 WorldCat member libraries worldwide

Experimental Mechanics of Composite, Hybrid, and Multifunctional Materials, Volume 6 Proceedings of the 2013 Annual Conference on Experimental and Applied Mechanics by G. P Tandon( )

9 editions published in 2014 in English and held by 59 WorldCat member libraries worldwide

This critical collection examines a range of materials from joints and bonded composites to energy storage materials, as presented in early findings and case studies from the Proceedings of the 2013 Annual Conference on Experimental and Applied Mechanics. The collection includes papers in the following general technical research areas: • Characterization of Energy Storage Materials • Microvascular & Natural Composites • Nanocomposites for Multifunctional Performance • Composite/Hybrid Characterization Using Digital Image Correlation • Failure Behavior of Polymer Matrix Composites • Non-Destructive Testing of Composites • Composite Test Methods • Joints/Bonded Composites Experimental Mechanics of Composite, Hybrid, and Multifunctional Materials: Proceedings of the 2013 Annual Conference on Experimental and Applied Mechanics is the sixth volume of eight from the Conference
Experimental and Applied Mechanics by Nancy Sottos( )

1 edition published in 2014 in English and held by 5 WorldCat member libraries worldwide

The influence of interphase regions on local thermal stresses and deformations in composites by Nancy R Sottos( )

2 editions published in 1990 in English and held by 3 WorldCat member libraries worldwide

Proceedings of the 2014 Annual Conference on Experimental and Applied Mechanics by Annual Conference on Experimental and Applied Mechanics( Book )

1 edition published in 2015 in English and held by 3 WorldCat member libraries worldwide

Unconventional structured semiconductors and their applications in optoelectronics and photovoltaics by Xiaoying Guo( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Self-sealing of thermal fatigue and mechanical damage in fiber-reinforced composite materials by Jericho L Moll( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Fiber reinforced composite tanks provide a promising method of storage for liquid oxygen and hydrogen for aerospace applications. The inherent thermal fatigue of these vessels leads to the formation of microcracks, which allow gas phase leakage across the tank walls. In this dissertation, self-healing functionality is imparted to a structural composite to effectively seal microcracks induced by both mechanical and thermal loading cycles. Two different microencapsulated healing chemistries are investigated in woven glass fiber/epoxy and uni-weave carbon fiber/epoxy composites. Self-healing of mechanically induced damage was first studied in a room temperature cured plain weave E-glass/epoxy composite with encapsulated dicyclopentadiene (DCPD) monomer and wax protected Grubbs' catalyst healing components. A controlled amount of microcracking was introduced through cyclic indentation of opposing surfaces of the composite. The resulting damage zone was proportional to the indentation load. Healing was assessed through the use of a pressure cell apparatus to detect nitrogen flow through the thickness direction of the damaged composite. Successful healing resulted in a perfect seal, with no measurable gas flow. The effect of DCPD microcapsule size (51 um and 18 um) and concentration (0 - 12.2 wt%) on the self-sealing ability was investigated. Composite specimens with 6.5 wt% 51 um capsules sealed 67% of the time, compared to 13% for the control panels without healing components. A thermally stable, dual microcapsule healing chemistry comprised of silanol terminated poly(dimethyl siloxane) plus a crosslinking agent and a tin catalyst was employed to allow higher composite processing temperatures. The microcapsules were incorporated into a satin weave E-glass fiber/epoxy composite processed at 120C to yield a glass transition temperature of 127C. Self-sealing ability after mechanical damage was assessed for different microcapsule sizes (25 um and 42 um) and concentrations (0 - 11 vol%). Incorporating 9 vol% 42 um capsules or 11 vol% 25 um capsules into the composite matrix leads to 100% of the samples sealing. The effect of microcapsule concentration on the short beam strength, storage modulus, and glass transition temperature of the composite specimens was also investigated. The thermally stable tin catalyzed poly(dimethyl siloxane) healing chemistry was then integrated into a [0/90]s uniweave carbon fiber/epoxy composite. Thermal cycling ( -196C to 35C) of these specimens lead to the formation of microcracks, over time, formed a percolating crack network from one side of the composite to the other, resulting in a gas permeable specimen. Crack damage accumulation and sample permeability was monitored with number of cycles for both self-healing and traditional non-healing composites. Crack accumulation occurred at a similar rate for all sample types tested. A 63% increase in lifetime extension was achieved for the self-healing specimens over traditional non-healing composites
Multiscale Modeling and Experiments for Design of Self-Healing Structural Composite Materials( Book )

2 editions published in 2005 in English and held by 2 WorldCat member libraries worldwide

A set of multi-scale materials systems design tools focused on issues relevant to self-healing structural composites have been developed by a research team from the University of Illinois and the University of Michigan. Our vision was to create a computational framework for materials systems design spanning from atomistic to macroscopic (structural) length scales, supported and validated by a set of experiments conducted at various scales. Although special emphasis in the present project ha been placed on the modeling of the fatigue response of a self-healing composite, the approach adopted in this project yielded tool that have broad applicability for generic fracture and fatigue problems in modem engineering materials. This paper summarizes our accomplishments of the past three years primarily on the macroscale numerical and experimental aspects of the program. 0 the numerical side, we have focused on the development, implementation and validation of a cohesive failure model able to capture at the structural level the fatigue retardation effect of the healing agent on the cyclic response of the self-healing composite
Microencapsulation of reactive amines and isocyanates and their application to self-healing systems by David A McIlroy( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Microcapsule-based self-healing systems enable repair of crack damage in polymers and polymer matrix composites. Existing self-healing chemistries are limited by relatively weak chemical bonding between the matrix and the healing material, temperature stability, and side reactions that degrade the active components. We demonstrate for the first time a two-part system that incorporates a healing chemistry similar to the matrix curing chemistry, enabling chemical bonding between the healed material and the matrix material. Amine-containing microcapsules are synthesized by interfacial polymerization of a polyurea about a droplet of amine by means of suspension polymerization. Capsules are subsequently isolated and analyzed for content, and shown to contain reactive amine. The microcapsules containing reactive amine are employed in concert with microcapsules containing epoxy resin to recover fracture toughness in a cured epoxy. Both capsule types are dispersed in an epoxy resin and the resin is chemically cured. Mechanical load is applied to propagate a crack and rupture microcapsules contained within the cured resin. The average peak load at failure in a virgin specimen is recorded, and compared to the average peak load at failure in the same specimen after a healing period. Recovery of fracture toughness is limited to 15% for specimens healed at temperatures of 50 oC and below, whereas healing efficiencies of up to 60% are observed for specimens healed at temperatures above 80 oC. Control specimens where amine was not present failed to recover. Microcapsules containing isocyanate are also prepared by means of interfacial polyurea condensation. These capsules are also isolated and analyzed for content, and shown to contain reactive isocyanate. No healing was observed with these capsules, however, due to problems with bonding and long-term stability. With refinement, the isocyanate system is projected for use in polyurethane matrix materials where a moisture-cure could promote the healing reaction
Microfluidic assembly and packing dynamics of colloidal granules by Robert F Shepherd( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Granular materials composed of primary colloidal particles are of both scientific and technological importance. The creation of granular systems for fundamental studies of their packing dynamics as well as applications ranging from ceramics processing to low-cost MEMS devices requires the ability to precisely control the granule size, size distribution, shape, and composition. Many methods exist for producing colloidal granules, including fluidized granulation, high shear mixer granulation, and spray drying. However, none of these methods provide adequate control over these important parameters. In this thesis, we use microfluidic-based assembly methods to control granular size, shape, and chemical heterogeneity. We then investigate the packing dynamics of non-spherical granular media using X-ray micro-computed tomography. Monodisperse spheroidal granules composed of colloid-filled hydrogels are created in a sheath-flow microfluidic device. By exploiting the physics of laminar flow in microchannels, drops composed of silica microspheres suspended in an aqueous acrylamide monomer solution are created within a continuous oil phase. The interfacial tension between these two immiscible fluids drives a Rayleigh-mode instability that promotes drop formation. Next, the drops undergo photopolymerization to create an acrylamide hydrogel that freezes in the desired morphology and composition during assembly. To demonstrate the flexibility of this new granulation technique, we assemble both dense homogenous and Janus granules in both spherical and discoid geometries. To produce non-spherical granular media, a lithographic-based microfluidic technique known as stop-flow-lithography is employed. Specifically, colloidal granules and microcomponents in the form of microgear, triangular, discoid, cuboid, and rectangular shapes are produced by this approach. In addition, pathways are demonstrated that allow these building blocks to be transformed into both porous and dense oxide and non-oxide structures. Finally, large quantities of non-spherical colloidal granules of controlled surface roughness are created via stop-flow lithography in cube and rectangular prism geometries of varying polydispersity. Their packing behavior under static and dynamic conditions is investigated by X-ray micro-computed tomography. Their voronoi volume distribution is quantified as a function of granule shape and agitation time using image analysis techniques. These data are then fit to a probabilistic k-Gamma analytical function, which allows one to quantify an order parameter, k, for the jamming condition of low dispersity cube, rectangular prism and bimodal cube granules. We find a steadily decreasing k-value for monodisperse cubes, suggesting local cube rearrangement during consolidation; while monodisperse rectangular granules and a bimodal distribution of cube granules demonstrate a relatively consistent k-value during consolidation, suggesting the local granule configuration remains similar. In each case, the data collapse onto a single master curve, suggesting a qualitatively similar jamming condition during compaction
Direct ink writing of microvascular networks by Willie Wu( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Nature is replete with examples of embedded microvascular systems that enable efficient fluid flow and distribution for autonomic healing, cooling, and energy harvesting. The ability to incorporate microvascular networks in functional materials systems is therefore both scientifically and technologically important. In this PhD thesis, the direct-write assembly of planar and 3D biomimetic microvascular networks within polymer and hydrogel matrices is demonstrated. In addition, the influence of network design of fluid transport efficiency is characterized. Planar microvascular networks composed of periodic lattices of uniformal microchannels and hierarchical, branching architectures are constructed by direct-write assembly of a fugitive organic ink. Several advancements are required to facilitate their patterning, including pressure valving, dual ink printing, and dynamic pressure variation to allow tunable control of ink deposition. The hydraulic conductance is measured using a high pressure flow meter as a function of network design. For a constant vascular volume and areal coverage, 2- and 4-generation branched architectures that obey Murray's Law exhibited the highest hydraulic conductivity. These experimental observations are in good agreement with predictions made by analytic models. 3D microvascular networks are fabricated by omnidirectional printing a fugitive organic ink into a photopolymerizable hydrogel matrix that is capped with fluid filler of nearly identical composition. Using this approach, 3D networks of arbitrary design can be patterned. After ink deposition is complete, the matrix and fluid filler are chemically cross-linked via UV irradiation, and the ink is removed by liquefication. Aqueous solutions composed of a triblock copolymer of polyethylene oxide (PEO)-polypropylene oxide (PPO)-PEO constitute the materials system of choice due to their thermal- and concentration-dependent phase behavior. Specifically, the fugitive ink consists of a 23 w/w% PEO-PPO-PEO (Pluronic F127) solution, while matrix (25 w/w%) and fluid filler (20 w/w%) are composed of an acrylate-modified form of the Pluronic F127 that can be subsequently photopolymerized. The ink and matrix concentrations exceed the critical micelle concentration (CMC) of 22 w/w% and thus reside in a physical gel state. At their respective concentrations, they possess an elastic plateau modulus G'> 104 Pa needed for ink filament formation, shape retention, and support during the printing process. By contrast, the fluid filler is formulated below the CMC to facilitate its flow into void spaces created as the nozzle translates through the matrix during printing. After printing is completed, photopolymerization is carried out to yield a chemically cross-linked matrix from which the fugitive ink is removed leaving behind the desired 3D microvascular network. Due to the potential application of 3D microvasularized hydrogels in tissue engineering, dye diffusion through the cured Pluronic F127-diacrylate matrix is investigated via fluorescent microscopy. Image analysis is used to extract diffusion profiles of the dye as a function of time. Extraction of the 1-D Gaussian fitting parameters is used to determine the spatial peak variance ¹̐đ2 and plotted as a function of time to determine the dye diffusivity
Mechanical characterization and self-healing in synthetic vascularized materials by Andrew R Hamilton( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Inspired by natural healing processes, a variety of synthetic self-healing materials have been developed that mechanically recover from structural damage autonomously. One strategy for creating self-healing materials is to distribute reactive fluids throughout the material volume using a microvascular network of microchannels that serve as conduits of flow and permit fluid transport throughout the material volume, in much the same way that vascular systems transport nutrients and biochemical components throughout living organisms. Artificial vascular systems have been successfully incorporated into materials with low load-bearing requirements to heal cracks in coating materials and skin-core debonding with foam crushing in composite sandwich structures. In these applications, cracks are confined to the coating material or near the skin-core interface; the vascular system is intentionally placed within regions with a low probability of failure and terminates where damage is expected to occur. This dissertation explores the interaction of cracks with a vascular system embedded within a structural material and the delivery of healing agents to these sites of internal damage. The mechanical impact of incorporating a synthetic vascular system into a load-bearing material is assessed through the measurement of the bulk material stiffness and fracture toughness, as well as the influence on crack propagation and the distribution of strain. As expected, the bulk stiffness decreases and strain is concentrated in regions surrounding the vascular features. The bulk fracture toughness of the material decreases with the addition of a high volume fraction vascular system, but individual vascular features impede crack propagation under certain conditions. Test protocols are developed to characterize the ability to repeatedly repair large damage volumes under both quasi-static and fatigue loading conditions. Damage events that occurred in the same location are healed multiple times owing to the interconnectivity of the vascular system, which allows the flow of liquid healing agents from undamaged regions of material to the sites of damage. Pressurized vascular systems improve the delivery of healing agents by allowing a larger damage volume to be serviced by a smaller vascular system, making flow less susceptible to obstruction, and providing a means of directing flow to enhance mixing of two liquid healing agents. The result of pressure-driven flow is a higher degree of mechanical recovery and sustained repeatability of healing events. In addition to addressing quasi-static fracture damage, crack propagation under cyclic fatigue is slowed or completely arrested using pressurized vascular systems to deliver rapidly curing healing agents to actively growing cracks
Materials with engineered mesoporosity for programmed mass transport by Dara V Gough( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Dynamic delamination of patterned thin films by Phuong Tran( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

We present here a novel experimental/numerical protocol to extract the fracture toughness of the thin film/substrate interface. The testing method involves using a laser-induced acoustic stress wave to load the film/substrate fracture plane in tension at very high strain rate (~10^7/s) leading to the inertia-driven interface delamination. A weak adhesive layer is selectively introduced at the interface to serve as a pre-crack exploiting the inertial effect to obtain stable crack growth. The kinetic energy imparted to the weakly bonded region of the film is converted into fracture energy as the thin film delaminates in a controlled fashion. To support the dynamic experiment in extracting the interface fracture toughness values, we develop a numerical scheme based on the combination of spectral representation of the elastodynamic solutions for the substrate and finite element model for the thin film. Cohesive elements are introduced along the bi-material interface to capture the decohesion process. The important role of the inertia on the crack extension and the mixed-mode failure are demonstrated by observing the traction stress evolutions at various points along the bond line. To speed up the simulation process we develop a numerical scheme based on the combination of a nonlinear beam model to capture the elastodynamic response of the thin film and a cohesive failure model to simulate the interface. Numerical results are then validated with experimental measurements of the interface crack evolution history using resistance gage technique. The fracture toughness values measured from the dynamic tests are finally validated with results obtained by using four-point bending technique
Multifunctional Polymers and Composites for Self-Healing Applications( Book )

2 editions published in 2006 in English and held by 2 WorldCat member libraries worldwide

Mechanical deformation can be used to activate specific reaction pathways in mechanochemical triggers designed to harness the energy in a polymer under stress. Since activation of these triggers occurs before chain scission, we feel that they will be useful for the development of self-toughening polymeric materials. Upon activation, the oQDM intermediates could react with pendant dienophiles to form new crosslinks. The formation of crosslinks would be directly coupled and tailored to the stress field in a failing polymer. We also feel, with slight modification, that mechanochemical triggers could be useful for the stress-induced formation of new chromophores. The newly formed chromophores could then signal that some critical load has been reached, or perhaps signal the presence of microcracks. We expect that the procedures reported here will be generally useful for the development of utilizing mechanical energy to activate specific chemical pathways, and help shift the major focus of mechanochemical studies from bond-breaking to bond-making transformations
Interference lithography for optical devices and coatings by Abigail T Juhl( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Interference lithography can create large-area, defect-free nanostructures with unique optical properties. In this thesis, interference lithography will be utilized to create photonic crystals for functional devices or coatings. For instance, typical lithographic processing techniques were used to create 1, 2 and 3 dimensional photonic crystals in SU8 photoresist. These structures were in-filled with birefringent liquid crystal to make active devices, and the orientation of the liquid crystal directors within the SU8 matrix was studied. Most of this thesis will be focused on utilizing polymerization induced phase separation as a single-step method for fabrication by interference lithography. For example, layered polymer/nanoparticle composites have been created through the one-step two-beam interference lithographic exposure of a dispersion of 25 and 50 nm silica particles within a photopolymerizable mixture at a wavelength of 532 nm. In the areas of constructive interference, the monomer begins to polymerize via a free-radical process and concurrently the nanoparticles move into the regions of destructive interference. The holographic exposure of the particles within the monomer resin offers a single-step method to anisotropically structure the nanoconstituents within a composite. A one-step holographic exposure was also used to fabricate self- healing coatings that use water from the environment to catalyze polymerization. Polymerization induced phase separation was used to sequester an isocyanate monomer within an acrylate matrix. Due to the periodic modulation of the index of refraction between the monomer and polymer, the coating can reflect a desired wavelength, allowing for tunable coloration. When the coating is scratched, polymerization of the liquid isocyanate is catalyzed by moisture in air; if the indices of the two polymers are matched, the coatings turn transparent after healing. Interference lithography offers a method of creating multifunctional self-healing coatings that readout when damage has occurred
Spiropyrans as color-generating mechanophores by Douglas A Davis( )

1 edition published in 2010 in English and held by 2 WorldCat member libraries worldwide

Autonomic healing of low-velocity impact damage in woven fiber-reinforced composites by Amit J Patel( )

1 edition published in 2011 in English and held by 2 WorldCat member libraries worldwide

Polymer-matrix fiber-reinforced composites have seen increasing use in applications requiring high specific strength and stiffness. These materials typically show excellent in-plane properties but are particularly susceptible to transverse impacts. Impact can significantly reduce strength and the extent of damage can grow under cyclic loading conditions. Because this type of damage often occurs below the surface, hidden from inspection, it is especially critical in structural applications. Traditionally, impact damage repair techniques have focused on increased factors of safety or use of toughened polymer matrices. In this work, a microcapsule-based self-healing epoxy is used in woven fiber-reinforced composite panels for the repair of matrix damage imparted by low-velocity impact. The initial work focused on self-healing in plain 2D woven S2 glass laminates with an epoxy matrix. The self-healing components, dicyclopentadiene (DCPD) microcapsules and wax-encapsulated first generation Grubbs' catalyst microspheres, were premixed into the liquid epoxy, and panels are fabricated using a hand layup technique and compression molding. Low-velocity impact damage was introduced to these panels by drop-weight impact testing. To visually assess the damage state, cracks on sections through the impact damage were marked with fluorescent dye penetrant. A 51% reduction in total crack length per imaged edge was observed for self-healing panels when compared to non-healing controls, indicating filling of damage with healed material. A reduction in damage resistance was also observed upon inclusion of both self-healing components. Recovery of mechanical properties after healing was investigated by conducting compression-after-impact tests. Self-healing panels showed full recovery of residual compressive strength up to a threshold impact energy nearly double that of non-healing controls. Above this threshold impact energy, residual compressive strength was partially recovered to a degree that diminished with increasing impact energy. The work on self-healing 2D woven composites indicated that catalyst microspheres significantly reduced damage resistance, while microcapsules did not have the same detrimental effect on damage resistance. Thus, potential improvements by the use of catalyst microspheres encapsulated by poly(urea-formaldehyde) (UF) were explored. To investigate the effect of encapsulating catalyst microspheres with UF on the mechanical properties, UF encapsulated wax microspheres were fabricated and investigated. Tapered double cantilever beam samples containing these UF encapsulated wax microspheres showed better mode I fracture toughness than samples containing wax microspheres. In addition, composite panels containing DCPD microcapsules and UF encapsulated microspheres exhibited higher impact damage resistance. The recovery of impact damage in 3D orthogonal woven composites was also explored. Low-velocity impact damage in 2D plain woven and 3D orthogonal woven glass/epoxy composites was compared by developing and implementing a semi-automated crack measurement program to obtain a statistical measure of damage state for both types of panels. The results indicate a modest reduction in total delamination length, total delamination cross-sectional area, and delamination separation in 3D composite panels compared to 2D woven composite panels. These findings are attributed to toughening mechanisms associated with through-thickness z-tow reinforcement. Self-healing functionality is incorporated into 3D orthogonal woven glass/epoxy composites via an aqueous impregnation suspension containing DCPD microcapsules and urea-formaldehyde encapsulated Grubbs' catalyst microspheres. The pre-impregnated fabric is infused with an epoxy matrix using vacuum bag resin infusion. A protocol based on double cantilever impact of beam samples and flexure after impact is used to characterize mechanical recovery. The lack of recovery of self-healing beam samples in four-point flexure after impact tests highlights the current challenges of incorporating a microcapsule-based DCPD-Grubbs' catalyst self-healing system into a 3D woven composite. An estimate of healing agent delivered to the crack plane indicated inadequate healing agent delivery to significantly fill the damage separations that were measured. In addition, it was demonstrated that the polymerization propagation distance of DCPD from the ruptured catalyst microspheres was insufficient to heal damage in regions where fiber tows overlapped. Finally, lap shear tests demonstrated that the adhesion of poly-DCPD to the epoxy matrix was significantly lower than the adhesion of the epoxy matrix to itself. This relatively poor adhesion limited the achievable recovery
 
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Alternative Names
Nancy Sottos Amerikaans scheikundige

Nancy Sottos chimiste américaine

Sottos, N. R.

Sottos, N. R. (Nancy R.)

نانسی سوتوس

Languages
English (45)