NANOTUBE/FIBER MULTI-SCALE HYBRID COMPOSITES USING ELECTROPHORETIC DEPOSITION: PROCESSING, CHARACTERIZATION, AND SMART SENSING APPLICATIONS

Carbon nanotubes are widely known to have unique physical and mechanical properties at the nanoscale. Because carbon nanotubes have diameters three orders of magnitude smaller than traditional advanced fibers used in structural composites there is unique opportunity to create multi-scale hybrid composite systems where reinforcement scales are combined. Our recent research has developed a highly efficient and industrially scalable electrophoretic deposition technique for nanoscale hybridization. The resulting composites show a hierarchical structure, where the structural fibers, which have diameters in micrometer range, are coated with carbon nanotubes having diameters around 10–20 nm. Microscopic characterization shows the integration of carbon nanotubes throughout the thickness of the fabric, where individual fibers are coated with carbon nanotubes. Within the composite, networks of carbon nanotubes span between adjacent fibers, and the resulting composites exhibit good electrical conductivity and considerable increases in the interlaminar shear strength, relative to fiber composites without integrated carbon nanotubes. We have demonstrated that conducting carbon nanotube networks formed in a polymer matrix can be utilized as highly-sensitive sensors for detecting the onset, nature and evolution of damage in advanced polymer-based fiber composites. The potential of carbon nanotubes for in situ monitoring of damage accumulation in fiber composites will be discussed and recent research on utilizing carbon nanotubes in monitoring of large-scale structures highlighted. Please click Additional Files below to see the full abstract

Bridging the Gender Gap in Forest Stewardship: Facilitating Programs for Women Landowners

Nationwide, women woodland owners are increasingly taking on the primary decision-making role for their land. In Wisconsin and beyond, most existing landowner outreach efforts target mixed-gender audiences. We explored how facilitation techniques can be incorporated into a women-centric workshop to increase women landowners\u27 confidence, knowledge, and readiness to take action in forest stewardship. We highlight three core techniques Extension workshop developers can use to promote landowner learning and engagement: creating space for participant-driven open dialogue, generating opportunities for peer-to-peer learning, and enabling participants to receive personalized advice from professionals about their land

A mechanistic study of fire retardancy of carbon nanotube/ethylene vinyl acetate copolymers and their clay composites

A further investigation of the roles of multi-walled carbon nanotubes and clay in the fire retardancy of ethylene vinyl acetate copolymer (EVA) nanocomposites has been carried out. It was found that the nanotubes played an important role in the reduction of the peak of heat release rate by forming low permeability char containing graphitic carbon. The oxidation resistance of the char is a function of the degree of graphitisation. Adding clay into the nanotube/EVA composite tends to enhance the formation of graphitic carbon. The nanotubes also have the function of reducing surface cracks of chars to increase barrier resistance to the evolution of flammable volatiles and the oxygen ingress to the condensed phase

School Counseling at Cedar Falls High School

This semester, I had the opportunity to intern with a school counselor at Cedar Falls High to gain insight into how mental health programs function and how they are applied by the team. I have learned therapy techniques, created yearly mental health reports to foresee trends, and have helped support the students’ emotional and academic needs. This poster exemplifies how sleep is strongly linked with depression and attendance in school, the various programs and plans that Cedar Falls High School offers, and how this experience has aided in creating additional future career goals for me

A comparative experiment for the analysis of microwave and thermal process induced strains of carbon fiber/bismaleimide composite materials

Carbon fiber reinforced bismaleimide composites provide many outstanding properties and are widely used in aerospace applications. However, cure-induced strains are present in virtually all composites that severely impact on the whole service lifecycle of composite components. This paper will demonstrate that the cure-induced strains can be drastically reduced in fiber/ bismaleimide composites using the microwave curing process. Nearly 95% reduction of cure-induced strains has been achieved compared with the conventional thermal heating process. The microwave manufacturing cycle for composites was only 36% of the thermal processing cycle. When using the microwave process, the spring-in angle of an L-shaped part was reduced by about 1.2°Compared by using thermal heating

Molecular dynamics simulations of the contact angle between water droplets and graphite surfaces

Wetting is a widespread phenomenon, most prominent in a number of cases, both in nature and technology. Droplets of pure water with initial radius ranging from 20 to 80 [\AA] spreading on graphitic surfaces are studied by molecular dynamics simulations. The equilibrium contact angle is determined and the transition to the macroscopic limit is discussed using Young equation in its modified form. While the largest droplets are almost perfectly spherical, the profiles of the smallest ones are no more properly described by a circle. For the sake of accuracy, we employ a more general fitting procedure based on local averages. Furthermore, our results reveal that there is a possible transition to the macroscopic limit. The modified Young equation is particularly precise for characteristic lengths (radii and contact-line curvatures) around 40 [\AA].Comment: Revised and extended version; http://dx.doi.org/10.1016/j.fluid.2012.07.01

Modeling of Polymer Clay Nanocomposite for a Multiscale Approach

The mechanical property enhancement of polymer reinforced with nano-thin clay platelets (of high aspect ratio) is associated with a high polymer-filler interfacial area per unit volume. The ideal case of fully separated (exfoliated) platelets is generally difficult to achieve in practice: a typical nanocomposite also contains multilayer stacks of intercalated platelets. Here we use numerical modelling to investigate how the platelet properties affect the overall mechanical properties. The configuration of platelets is modelled using a statistical interpretation of the Representative Volume Element (RVE) approach, in which an ensemble of "sample" heterogeneous material is generated (with periodic boundary conditions). A simple Monte Carlo algorithm is used to place non-intersecting platelets in the RVE according to a specified set of statistical distributions. The effective stiffness of the platelet-matrix system is determined by measuring the stress (using standard Finite Element analysis) produced as a result of applying a small deformation to the boundaries, and averaging over the entire statistical ensemble. In this work we determine the way in which the platelet properties (curvature, filling fraction, stiffness, aspect ratio) and the number of layers in the stack affect the overall stiffness enhancement of the nanocomposite. Thus, we bridge the gap between behaviour on the macroscopic scale with that on the scale of the nano-reinforcement, forming part of a multi-scale modelling framework.Comment: 39 pages, 19 figure

Interfacial Stress Transfer in a Graphene Monolayer Nanocomposite

Graphene is one of the stiffest known materials, with a Young's modulus of 1 TPa, making it an ideal candidate for use as a reinforcement in high-performance composites. However, being a one-atom thick crystalline material, graphene poses several fundamental questions: (1) can decades of research on carbon-based composites be applied to such an ultimately-thin crystalline material? (2) is continuum mechanics used traditionally with composites still valid at the atomic level? (3) how does the matrix interact with the graphene crystals and what kind of theoretical description is appropriate? We have demonstrated unambiguously that stress transfer takes place from the polymer matrix to monolayer graphene, showing that the graphene acts as a reinforcing phase. We have also modeled the behavior using shear-lag theory, showing that graphene monolayer nanocomposites can be analyzed using continuum mechanics. Additionally, we have been able to monitor stress transfer efficiency and breakdown of the graphene/polymer interface