Finite Element Methods in Smart Materials and Polymers

Functional polymers show unique physical and chemical properties, which can manifest as dynamic responses to external stimuli such as radiation, temperature, chemical reaction, external force, and magnetic and electric fields. Recent advances in the fabrication techniques have enabled different types of polymer systems to be utilized in a wide range of potential applications in smart structures and systems, including structural health monitoring, anti‐vibration, and actuators. The progress in these integrated smart structures requires the implementation of finite element modelling using a multiphysics approach in various computational platforms. This book presents finite element methods applied in modeling of the smart structures and materials with particular emphasis on hydrogels, metamaterials, 3D-printed and anti-vibration constructs, and fibers

Synthesis and Multi-Scale Characterization of Calcium Silicate Hydrate at Multiple CaO/SiO2 Mixture Ratios

Calcium Silicate Hydrate (C-S-H) is the primary binding agent that is responsible for setting and hardening, strength, dimensional stability, and durability of Portland cement paste. Although Portland cement hydration produces C-S-H, Calcium hydroxide (CH), ettringite, and other hydration products are also acquired from this process and make it difficult to characterize C-S-H exclusively. C-S-H was first synthesized by mixing calcium oxide (CaO), created by calcining calcium carbonate (CaCO3) that was heated to 950 \xbaC for 24 hours with fumed silica (SiO2) and deionized water (H2O) under nitrogen which produced the synthetic gel-like C-S-H slurry. This composition mixture of synthetic C-S-H was mixed continuously for 7 days with a constant speed and transferred to a filtration system for removal of excess water. The C-S-H gel was then transferred to a drying unit and purged in nitrogen for 5 weeks with a relative humidity (RH) of 11% using Lithium Chloride (LiCl) for 5 weeks. Specimens were obtained by compacting the dried C-S-H powder at 500 MPa. These compacted samples were tested for identifying its mechanical properties on macro, micro, and nano-scale levels. Nanoindentation was used to identify creep compliance and the reduced elastic modulus of C-S-H. Nanoindentation tests confirmed the 0.7 C/S ratio is stiffer (higher elastic modulus) than C-S-H with 1.5 C/S ratio. Furthermore, C-S-H with 0.7 C/S ratio has a lower creep compliance compared with C-S-H with 1.5 C/S ratios. Microstructural investigations using 29Si nuclear magnetic resonance (NMR) and Transmission Electron Microscopes (TEM) were performed on C-S-H specimens. This work shed light on the significance of silicate polymerization in C-S-H on elastic and creep behavior of cement and concrete. This work might lead to developing alternative cements for concrete structures with time-dependent critical applications

Modeling problems in mucus viscoelasticity and mucociliary clearance

From the common cold and allergies to severe chronic and acute respiratory impairments, the function of the body\u27s mucociliary clearance mechanism plays a primary defense role. Mucus demonstrates numerous non-Newtonian behaviors which set it apart from viscous fluids. Among them: Bingham plastic behavior, shear-thinning, and elasticity on short time scales due to relaxation time. Experimental evidence suggests that certain rheologies promote effective transport. In an effort to reveal the mechanisms controlling transport, models are developed. Firstly, a steady state model which idealizes the mucus as a rigid body is created in order to bring together disparate bodies of experimental work from the literature. The force balance reveals that the force cilia are capable of exerting cannot be related, simply, to the velocity of mucus. That is, only a fraction of the force cilia are capable of exerting is required to steadily transport mucus at the velocities observed experimentally. Likewise, the velocities estimated by this model when cilia force is the input are overestimated by one to two orders of magnitude. This incongruity formally motivates the inclusion of one of mucus\u27s rheological behaviors, stress relaxation. The first viscoelastic problem considered is the response of the linear Maxwell fluid to an oscillating plate. Though a problem commonly discussed in textbooks on theoretical viscoelasticity, the complete analytical solutions are not provided. Here, solutions are found and graphed in terms of the phase and amplitude of the velocity field resultant from the oscillations of the plate; all derivations are shown in their entirety. The effects of stress relaxation (sometimes referred to as memory) and inertia on phase and amplitude are shown to have frequency dependence. Furthermore, it is shown that oscillatory shear perturbations to a viscoelastic Maxwell fluid always travel further and faster away from the source as Deborah number (a dimensionless parameter governing the importance of viscoelastic forces, De=0 corresponds to a Newtonian fluid) is increased. The limitation of the linear Maxwell fluid is illustrated by attempting to apply the constitutive equation to a thin film flow problem. It is found that the stress field of the solution only differs from the viscous case if the boundary conditions are transient; that is, the constitutive equation cannot account for the changes in stress that occur over space. The time derivative must be replaced by a Convected Derivative to achieve the proper Lagrangian to Eulerian coordinate transformation and is considered in a final set of problems. Three problems were completed using the Upper Convected Maxwell model for viscoelasticity. The first considers a purely unidirectional shear flow which, unlike a viscous fluid, possesses tensile stresses along streamlines. The model posits that these additional stresses are essential for transport by allowing regions which are actively sheared, to hold up inactive regions. A novel relationship between applied stress and relaxation time is developed; the model shows that increasing the relaxation time of mucus decreases the amount of stress that must be imparted by cilia. In the second two problems, the UCM equations are simplified via a perturbation series expansion for small Weissenberg number (also a dimensionless group governing the importance of viscoelastic forces). This technique allows the analytically solvable viscous (also referred to as the unperturbed or order one) solutions to be used to estimate the impact of small amounts of stress memory. It is found that elasticity increases the developing region of a viscous flow; all stress components are convected downstream due to flow memory. Likewise, in the sinusoidally varying stress case, the velocity field is always shifted further away from the phase of the applied stress as viscoelastic forces are increased. It is also found that the departure from the viscous solution is dramatically reduced if the stress distribution is moving at the same velocity as the mucal flow. This shows the benefit of an antiplectic wave speed (the physiologically relevant case in which the phase of the cilial beat is moving opposite to transport) as there is no danger that these two can be in phase with one another. Model restrictions prevent quantitative gauges of transport efficiency as a function of metachronal wave parameters and relaxation time to be made. Several additional problems are proposed to address unanswered modeling questions and experimental solutions for the lack of rheological data on tracheal mucus are suggested

Rheology and Processing of Polymers

This book covers the latest developments in the field of rheology and polymer processing, highlighting cutting-edge research focusing on the processing of advanced polymers and their composites. It demonstrates that the field of rheology and polymer processing is still gaining increased attention. Presented within are cutting-edge research results and the latest developments in the field of polymer science and engineering, innovations in the processing and characterization of biopolymers and polymer-based products, polymer physics, composites, modeling and simulations, and rheology

Technology for the Future: In-Space Technology Experiments Program, part 1

The purpose of the Office of Aeronautics and Space Technology (OAST) In-Space Technology Experiment Program (In-STEP) 1988 Workshop was to identify and prioritize technologies that are critical for future national space programs and require validation in the space environment, and review current NASA (In-Reach) and industry/university (Out-Reach) experiments. A prioritized list of the critical technology needs was developed for the following eight disciplines: structures; environmental effects; power systems and thermal management; fluid management and propulsion systems; automation and robotics; sensors and information systems; in-space systems; and humans in space. This is part one of two parts and is the executive summary and experiment description. The executive summary portion contains keynote addresses, strategic planning information, and the critical technology needs summaries for each theme. The experiment description portion contains brief overviews of the objectives, technology needs and backgrounds, descriptions, and development schedules for current industry, university, and NASA space flight technology experiments

Solid rocket motor internal insulation

Internal insulation in a solid rocket motor is defined as a layer of heat barrier material placed between the internal surface of the case propellant. The primary purpose is to prevent the case from reaching temperatures that endanger its structural integrity. Secondary functions of the insulation are listed and guidelines for avoiding critical problems in the development of internal insulation for rocket motors are presented

Development of engineering tools to analyze and design flexible structures in open ocean environments

Methods to effectively predict system response in marine settings are critical in the engineering design process. The high energy ocean environment can subject structures to large wave and current forces, causing complex coupled motions and loads. This research focused on the development of effective methods to predict flexible system response and the structural integrity of marine High Density Polyethylene (HDPE) components. Numerical modeling tools were developed to analyze and design flexible structures in open ocean environments. Enhancements to the University of New Hampshire\u27s Aqua-FE finite element computer program were performed, including expansion of the element library to include spherical geometries and implementation of various hydrodynamic effects such as Stokes 2nd order waves and water velocity reduction due to component shadowing. Two case studies, involving laboratory and field experiments, were performed evaluating the software modifications and examining the response of flexible systems in various environmental conditions. Practical applications of the numerical model are presented, focusing on the design, analysis and deployment of a submerged grid mooring 10 km from Portsmouth, NH. The system was recovered after a seven year deployment and inspected. The numerical model proved to be a valuable engineering tool for investigating a system\u27s motion dynamics and mooring tension response in marine environments. High density polyethylene is a primary structural component for marine systems such as fish containment, wave attenuators and marine defense barrier systems. The fundamental engineering issues with the compliant HDPE material are associated with how the material changes its stiffness and strength depending upon the service life, load rate and temperature. Structural modeling techniques were developed to determine effective methods of analyzing marine systems constructed of HDPE. This included the investigation of the mechanical behavior of new and environmentally fatigued HDPE specimens, obtained from commercial fish farms, at different strain rates and validation of the modeling approach with laboratory experiments. The operational limits, loads and modes of a failure of the HDPE cage frame were estimated, providing valuable information on the survivability of these large, flexible systems in offshore environments