Design of Active Composites

DTIC Science & Technology

2009-03-30

SMA and piezoelectric ceramics(SMA-piezo composite) for fast-responsive actuator, (iii) SMA-piezo composite for thermal energy harvester , and (iv...Composite for Thermal Energy Harvesting Piezoelectric materials and shape memory alloys (SMAs) are very common materials for actuators and sensors; however...their composites as electrical generators is least explored, although use of piezoelectric as the mechanical energy harvester is increasingly popular

Estimation of Supersonic Stage Separation Aerodynamics of Winged-Body Launch Vehicles Using Response Surface Methods

NASA Technical Reports Server (NTRS)

Erickson, Gary E.

2010-01-01

Response surface methodology was used to estimate the longitudinal stage separation aerodynamic characteristics of a generic, bimese, winged multi-stage launch vehicle configuration at supersonic speeds in the NASA LaRC Unitary Plan Wind Tunnel. The Mach 3 staging was dominated by shock wave interactions between the orbiter and booster vehicles throughout the relative spatial locations of interest. The inference space was partitioned into several contiguous regions within which the separation aerodynamics were presumed to be well-behaved and estimable using central composite designs capable of fitting full second-order response functions. The underlying aerodynamic response surfaces of the booster vehicle in belly-to-belly proximity to the orbiter vehicle were estimated using piecewise-continuous lower-order polynomial functions. The quality of fit and prediction capabilities of the empirical models were assessed in detail, and the issue of subspace boundary discontinuities was addressed. Augmenting the central composite designs to full third-order using computer-generated D-optimality criteria was evaluated. The usefulness of central composite designs, the subspace sizing, and the practicality of fitting lower-order response functions over a partitioned inference space dominated by highly nonlinear and possibly discontinuous shock-induced aerodynamics are discussed.

The high velocity impact loading on symmetrical and woven hybrid composite laminates

NASA Astrophysics Data System (ADS)

Jin, Martin; Richardson, Mel; Zhang, Zhong Yi

2007-07-01

Space structures use fibre composite materials, due to their lightweight. This paper examines the impact response of symmetrical and hybrid composite laminates. Special attention is given to the stacking sequences used. The experimental study of structures has always provided a major contribution to our understanding. Even with the formidable growth in the use and capacity of computing power the need for experimental measurement is as compelling as ever. The design of hybrid composite structures is complicated by the number of design variables and the interaction of the constituents is the composite system. Since it is desirable to experimentally test the design and it is not practical to test a full scale model, the structural/material similitude concept is used to create a small scale model with a similar structural response. In the current study, experimental investigations were carried out to determine the response of four different combinations of hybrid laminates to low-velocity impact loading using an instrumented impact testing machine. Hybrid laminates were fabricated with twill weave carbon fabric and plain weave S2-glass fabric using vacuum assisted resin molding process with SC-15 epoxy resin system. Response of carbon/epoxy and glass/epoxy laminates was also investigated to compare with that of hybrid samples. Square laminates of size 100 mm and nominal thickness of 3 mm were subjected to low-velocity impact loading at four energy levels of 10, 20, 30 and 40 J. Results of the study indicate that there is considerable improvement in the load carrying capability of hybrid composites as compared to carbon/epoxy laminates with slight reduction in stiffness.

Tension and Compression Creep Apparatus for wood-Plastic Composites

Treesearch

Scott E. Hamel; John C. Hermanson; Steven M. Cramer

2011-01-01

Design of structural members made of wood-plastic composites (WPC) is not possible without accurate test data for tension and compression. The viscoelastic behavior of these materials means that these data are required for both the quasi-static stress-strain response, and the long-term creep response. Their relative incompressibility causes inherent difficulties in...

MAC/GMC Code Enhanced for Coupled Electromagnetothermoelastic Analysis of Smart Composites

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.; Aboudi, Jacob

2002-01-01

Intelligent materials are those that exhibit coupling between their electromagnetic response and their thermomechanical response. This coupling allows smart materials to react mechanically (e.g., an induced displacement) to applied electrical or magnetic fields (for instance). These materials find many important applications in sensors, actuators, and transducers. Recently interest has arisen in the development of smart composites that are formed via the combination of two or more phases, one or more of which is a smart material. To design with and utilize smart composites, designers need theories that predict the coupled smart behavior of these materials from the electromagnetothermoelastic properties of the individual phases. The micromechanics model known as the generalized method of cells (GMC) has recently been extended to provide this important capability. This coupled electromagnetothermoelastic theory has recently been incorporated within NASA Glenn Research Center's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC). This software package is user friendly and has many additional features that render it useful as a design and analysis tool for composite materials in general, and with its new capabilities, for smart composites as well.

Quantification of uncertainties in the performance of smart composite structures

NASA Technical Reports Server (NTRS)

Shiao, Michael C.; Chamis, Christos C.

1993-01-01

A composite wing with spars, bulkheads, and built-in control devices is evaluated using a method for the probabilistic assessment of smart composite structures. Structural responses (such as change in angle of attack, vertical displacements, and stresses in regular plies with traditional materials and in control plies with mixed traditional and actuation materials) are probabilistically assessed to quantify their respective scatter. Probabilistic sensitivity factors are computed to identify those parameters that have a significant influence on a specific structural response. Results show that the uncertainties in the responses of smart composite structures can be quantified. Responses such as structural deformation, ply stresses, frequencies, and buckling loads in the presence of defects can be reliably controlled to satisfy specified design requirements.

Effects of cutouts on the behavior of symmetric composite laminates subjected to bending and twisting loads

NASA Technical Reports Server (NTRS)

Prasad, C. B.; Shuart, M. J.; Bains, N. J.; Rouse, M.

1993-01-01

Composite structures are used for a wide variety of aerospace applications. Practical structures contain cutouts and these structures are subjected to in-plane and out-of-plane loading conditions. Structurally efficient designs for composite structures require a thorough understanding of the effects of cutouts on the response of composite plates subjected to inplane or out-of-plane loadings. Most investigations of the behavior of composite plates with cutouts have considered in-plane loadings only. Out-of-plane loadings suchas bending or twisting have received very limited attention. The response of homogeneous plates (e.g., isotropic or orthotropic plates) subjected to bending or twisting moments has been studied analytically. These analyses are for infinite plates and neglect finite-plate effects. Recently, analytical and experimental studies were conducted to determine the effects of cutouts on the response of laminated composite plates subjected to bending moments. No analytical or experimental results are currently available for the effects of cutouts on the response of composite laminates subjected to twisting moments.

Temperature-Responsive Polymers for Biological Applications

DTIC Science & Technology

2003-06-01

polymer temperature response in water by varying chemical composition of the monomer. In order to achieve this a series of polymers were designed and...varying the m/n composition and polymer type. Polymer grafting onto the silicon surface exhibits similar solubility behaviour. Adhesion energy...Driven by the high promise for biomedical applications, polymers that exhibit a response in water at about 37ºC are of particular interest. Taylor and

Development of a composite tailoring procedure for airplane wing

NASA Technical Reports Server (NTRS)

Chattopadhyay, Aditi; Zhang, Sen

1995-01-01

The development of a composite wing box section using a higher order-theory is proposed for accurate and efficient estimation of both static and dynamic responses. The theory includes the effect of through-the-thickness transverse shear deformations which is important in laminated composites and is ignored in the classical approach. The box beam analysis is integrated with an aeroelastic analysis to investigate the effect of composite tailoring using a formal design optimization technique. A hybrid optimization procedure is proposed for addressing both continuous and discrete design variables.

Response Surface Methodology: 1966-1986

DTIC Science & Technology

1986-09-01

reviews criteria from which choices of design parameters in (i) can be made; for example, the choice of a composite...fact that, in ý13 this case, all design points are at a distance p = - from the design center, and no control is ex- erted on Var y(,k) at a distance...interactions in the second order model. The notion of "small’ composite results from the fact that additional information on

Near-Resonant Thermomechanics of Energetic and Mock Energetic Composite Materials

DTIC Science & Technology

2016-11-01

munition design . 15. SUBJECT TERMS Energetic Materials; Explosives; Mechanical Vibration; Thermomechanics; Damping; Plasticity 16. SECURITY...preliminary computational modeling tools, which can be used to predict material response during energetic material formulation and munition design . Key...which can be used to predict material response during energetic material formulation and munition design . More specifically, Task Order 0001

Modular Design Features of a Peptide Amphiphile Micelle Vaccine Platform and Their Impact on an Immune Response

NASA Astrophysics Data System (ADS)

Barrett, John Christopher

Inducing a strong and specific immune response is the hallmark of a successful vaccine. Nanoparticles have emerged as promising vaccine delivery devices to discover and elicit immune responses. Modular platforms are attractive for their engineerability and broad potential applications. Fine-tuning a nanoparticle vaccine to create an immune response with specific antibody and other cellular responses is influenced by many factors such as shape, size and composition. Peptide amphiphile micelles are a unique biomaterials platform that can function as a modular vaccine delivery system, enabling control over many of these important factors. Peptide amphiphiles (PAs) consist of a hydrophilic peptide antigen conjugated to a hydrophobic lipid tail. The PAs then self-assemble into micelles, with the micelle characteristics determined by the chemical composition of the PA and micelle preparation methods. PA micelles contain a large design space, so it is important to have a basic understanding of how each design feature can affect the platform's interaction with the immune system. In this dissertation, the structure, composition, and biodistribution properties of PA micelles are evaluated for their ability to impact an immune response against a Group A Streptococcus B cell antigen (J8). Through structural design and physical characterization, micelles are shown to self-assemble into either short rod-like or long cylindrical shapes. Analyzing these shape effects on the immune response showed that cylindrical micelles induced higher antibody titers than rod-like micelles, providing evidence that the cylindrical micelle shape is important to induce immune responses and a possible mechanism of action. Shape was also seen to impact the activation profile of dendritic cells, B cells and T cells. Assembly into cylindrical micelles also stabilizes the secondary structure of peptide antigens, which may impact the immune response raised. In composition, the hydrophobic/hydrophilic interface of PA micelles enabled the precise entrapment of amphiphilic adjuvants which were found to not alter micelle formation or shape. These heterogeneous micelles significantly enhanced murine antibody responses when compared to animals vaccinated with non-adjuvanted micelles or soluble J8 peptide supplemented with a classical adjuvant. PAs were also shown to traffic more efficiently to the lymph node than free peptide. Characterization of these design features and their impact on an immune response provides a valuable foundation of knowledge to apply when expanding the peptide amphiphile micelle platform to other vaccine applications.

On the Constitutive Response Characterization for Composite Materials Via Data-Driven Design Optimization

Treesearch

John G. Michopoulos; John G. Hermanson; Athanasios lliopoulos; Samuel Lambrakos; Tomonari Furukawa

2011-01-01

In the present paper we focus on demonstrating the use of design optimization for the constitutive characterization of anisotropic material systems such as polymer matrix composites, with or without damage. All approaches are based on the availability of experimental data originating from mechatronic material testing systems that can expose specimens to...

Design feasibility study of a divertor component reinforced with fibrous metal matrix composite laminate

NASA Astrophysics Data System (ADS)

You, Jeong-Ha

2005-01-01

Fibrous metal matrix composites possess advanced mechanical properties compared to conventional alloys. It is expected that the application of these composites to a divertor component will enhance the structural reliability. A possible design concept would be a system consisting of tungsten armour, copper composite interlayer and copper heat sink where the composite interlayer is locally inserted into the highly stressed domain near the bond interface. For assessment of the design feasibility of the composite divertor concept, a non-linear multi-scale finite element analysis was performed. To this end, a micro-mechanics algorithm was implemented into a finite element code. A reactor-relevant heat flux load was assumed. Focus was placed on the evolution of stress state, plastic deformation and ductile damage on both macro- and microscopic scales. The structural response of the component and the micro-scale stress evolution of the composite laminate were investigated.

Design of Composite Structures for Reliability and Damage Tolerance

NASA Technical Reports Server (NTRS)

Rais-Rohani, Masoud

1999-01-01

A summary of research conducted during the first year is presented. The research objectives were sought by conducting two tasks: (1) investigation of probabilistic design techniques for reliability-based design of composite sandwich panels, and (2) examination of strain energy density failure criterion in conjunction with response surface methodology for global-local design of damage tolerant helicopter fuselage structures. This report primarily discusses the efforts surrounding the first task and provides a discussion of some preliminary work involving the second task.

Development of pressure containment and damage tolerance technology for composite fuselage structures in large transport aircraft

NASA Technical Reports Server (NTRS)

Smith, P. J.; Thomson, L. W.; Wilson, R. D.

1986-01-01

NASA sponsored composites research and development programs were set in place to develop the critical engineering technologies in large transport aircraft structures. This NASA-Boeing program focused on the critical issues of damage tolerance and pressure containment generic to the fuselage structure of large pressurized aircraft. Skin-stringer and honeycomb sandwich composite fuselage shell designs were evaluated to resolve these issues. Analyses were developed to model the structural response of the fuselage shell designs, and a development test program evaluated the selected design configurations to appropriate load conditions.

Prefabricated Roof Beams for Hardened Shelters

DTIC Science & Technology

1993-08-01

beam with a composite concrete slab. Based on the results of the concept evaluation, a test program was designed and conducted to validate the steel...ultimaw, strength. The results of these tests showed that the design procedure accurately predicts the response of the ste,-confined concrete composite...BENDING OF EXTERNALLY REINFORCED CONCRETE BEAMS ........ 67 TABLE 9. SINGLE POINT LOAD BEAM TEST RESULTS

Compositionally Graded Multilayer Ceramic Capacitors.

PubMed

Song, Hyun-Cheol; Zhou, Jie E; Maurya, Deepam; Yan, Yongke; Wang, Yu U; Priya, Shashank

2017-09-27

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. Here, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters and power converters.

Boron/aluminum graphite/resin advanced fiber composite hybrids

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Lark, R. F.; Sullivan, T. L.

1975-01-01

Fabrication feasibility and potential of an adhesively bonded metal and resin matrix fiber-composite hybrid are determined as an advanced material for aerospace and other structural applications. The results show that using this hybrid concept makes possible a composite design which, when compared with nonhybrid composites, has greater transverse strength, transverse stiffness, and impact resistance with only a small penalty on density and longitudinal properties. The results also show that laminate theory is suitable for predicting the structural response of such hybrids. The sequence of fracture modes indicates that these types of hybrids can be readily designed to meet fail-safe requirements.

Test and Analysis of a Buckling-Critical Large-Scale Sandwich Composite Cylinder

NASA Technical Reports Server (NTRS)

Schultz, Marc R.; Sleight, David W.; Gardner, Nathaniel W.; Rudd, Michelle T.; Hilburger, Mark W.; Palm, Tod E.; Oldfield, Nathan J.

2018-01-01

Structural stability is an important design consideration for launch-vehicle shell structures and it is well known that the buckling response of such shell structures can be very sensitive to small geometric imperfections. As part of an effort to develop new buckling design guidelines for sandwich composite cylindrical shells, an 8-ft-diameter honeycomb-core sandwich composite cylinder was tested under pure axial compression to failure. The results from this test are compared with finite-element-analysis predictions and overall agreement was very good. In particular, the predicted buckling load was within 1% of the test and the character of the response matched well. However, it was found that the agreement could be improved by including composite material nonlinearity in the analysis, and that the predicted buckling initiation site was sensitive to the addition of small bending loads to the primary axial load in analyses.

Facile Fabrication of Composite Membranes with Dual Thermo- and pH-Responsive Characteristics.

PubMed

Ma, Bing; Ju, Xiao-Jie; Luo, Feng; Liu, Yu-Qiong; Wang, Yuan; Liu, Zhuang; Wang, Wei; Xie, Rui; Chu, Liang-Yin

2017-04-26

Facile fabrication of novel functional membranes with excellent dual thermo- and pH-responsive characteristics has been achieved by simply designing dual-layer composite membranes. pH-Responsive poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) block copolymers and polystyrene blended with thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) nanogels are respectively used to construct the top layer and bottom layer of composite membranes. The stretching/coiling conformation changes of the P4VP chains around the pK a (∼3.5-4.5) provide the composite membranes with extraordinary pH-responsive characteristics, and the volume phase transitions of PNIPAM nanogels at the pore/matrix interfaces in the bottom layer around the volume phase transition temperature (VPTT, ∼33 °C) provide the composite membranes with great thermoresponsive characteristics. The microstructures, permeability performances, and dual stimuli-responsive characteristics can be well tuned by adjusting the content of PNIPAM nanogels and the thickness of the PS-b-P4VP top layer. The water fluxes of the composite membranes can be changed in order of magnitude by changing the environment temperature and pH, and the dual thermo- and pH-responsive permeation performances of the composite membranes are satisfactorily reversible and reproducible. The membrane fabrication strategy in this work provides valuable guidance for further development of dual stimuli-responsive membranes or even multi stimuli-responsive membranes.

A structural model for composite rotor blades and lifting surfaces

NASA Technical Reports Server (NTRS)

Rehfield, Lawrence W.; Atilgan, Ali R.

1987-01-01

Composite material systems are currently candidates for aerospace structures, primarily for the design flexibiity they offer i.e., it is possible to tailor the material and manufacturing approach to the application. Two notable examples are the wing of the Grumman/USAF/DARPA X-29 and rotor blades under development by the U.S.A. Aerostructures Directorate (AVSCOM), Langley Research Center. A working definition of elastic or structural tailoring is the use of structural concept, fiber orientation, ply stacking sequence, and a blend of materials to achieve specific performance goals. In the design process, choices of materials and dimensions are made which produce specific response characteristics which permit the selected goals to be achieved. Common choices for tailoring goals are preventing instabilities or vibration resonances or enhancing damage tolerance. An essential, enabling factor in the design of tailored composite structures is structural modeling that accurately, but simply, characterizes response. The objective of this paper is to improve the single-cell beam model for composite rotor blades or lifting surfaces and to demonstrate its usefullness in applications.

Behaviour of partially composite precast concrete sandwich panels under flexural and axial loads

NASA Astrophysics Data System (ADS)

Tomlinson, Douglas George

Precast concrete sandwich panels are commonly used on building exteriors. They are typically composed of two concrete wythes that surround rigid insulation. They are advantageous as they provide both structural and thermal resistance. The structural response of sandwich panels is heavily influenced by shear connectors that link the wythes together. This thesis presents a study on partially composite non-prestressed precast concrete wall panels. Nine flexure tests were conducted on a wall design incorporating 'floating' concrete studs and Glass Fibre Reinforced Polymer (GFRP) connectors. The studs encapsulate and stiffen the connectors, reducing shear deformations. Ultimate loads increased from 58 to 80% that of a composite section as the connectors' reinforcement ratio increased from 2.6 to 9.8%. This design was optimized by reinforcing the studs and integrating them with the structural wythe; new connectors composed of angled steel or Basalt-FRP (BFRP) were used. The load-slip response of the new connector design was studied through 38 double shear push-through tests using various connector diameters and insertion angles. Larger connectors were stronger but more likely to pull out. Seven flexure tests were conducted on the new wall design reinforced with different combinations of steel and BFRP connectors and reinforcement. Composite action varied from 50 to 90% depending on connector and reinforcement material. Following this study, the axial-bending interaction curves were established for the new wall design using both BFRP and steel connectors and reinforcement. Eight panels were axially loaded to predesignated loads then loaded in flexure to failure. A technique is presented to experimentally determine the effective centroid of partially composite sections. Beyond the tension and compression-controlled failure regions of the interaction curve, a third region was observed in between, governed by connector failure. Theoretical models were developed for the bond-slip behaviour of the shear connection and to analyze the full panel's flexural and axial response to determine the longitudinal shear force transferred between wythes and account for partial composite behavior. The models were validated against experiments and used to conduct a parametric study. Among several interesting findings, the study demonstrated how composite action increases with the slenderness of axially loaded panels.

Probabilistic assessment of smart composite structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Shiao, Michael C.

1994-01-01

A composite wing with spars and bulkheads is used to demonstrate the effectiveness of probabilistic assessment of smart composite structures to control uncertainties in distortions and stresses. Results show that a smart composite wing can be controlled to minimize distortions and to have specified stress levels in the presence of defects. Structural responses such as changes in angle of attack, vertical displacements, and stress in the control and controlled plies are probabilistically assessed to quantify their respective uncertainties. Sensitivity factors are evaluated to identify those parameters that have the greatest influence on a specific structural response. Results show that smart composite structures can be configured to control both distortions and ply stresses to satisfy specified design requirements.

Design-Optimization Of Cylindrical, Layered Composite Structures Using Efficient Laminate Parameterization

NASA Astrophysics Data System (ADS)

Monicke, A.; Katajisto, H.; Leroy, M.; Petermann, N.; Kere, P.; Perillo, M.

2012-07-01

For many years, layered composites have proven essential for the successful design of high-performance space structures, such as launchers or satellites. A generic cylindrical composite structure for a launcher application was optimized with respect to objectives and constraints typical for space applications. The studies included the structural stability, laminate load response and failure analyses. Several types of cylinders (with and without stiffeners) were considered and optimized using different lay-up parameterizations. Results for the best designs are presented and discussed. The simulation tools, ESAComp [1] and modeFRONTIER [2], employed in the optimization loop are elucidated and their value for the optimization process is explained.

Optimization of composite coagulant made from polyferric chloride and tapioca starch in landfill leachate treatment

NASA Astrophysics Data System (ADS)

Shaylinda, M. Z. N.; Hamidi, A. A.; Mohd, N. A.; Ariffin, A.; Irvan, D.; Hazreek, Z. A. M.; Nizam, Z. M.

2018-04-01

In this research, the performance of polyferric chloride and tapioca flour as composite coagulants for partially stabilized leachate was investigated. Response surface methodology (RSM) was used to optimize the coagulation and flocculation process of partially stabilized leachate. Central composite design a standard design tool in RSM was applied to evaluate the interactions and effects of dose and pH. Dose 0.2 g/L Fe and pH 4.71 were the optimum value suggested by RSM. Experimental test based on the optimum condition, resulted in 95.9%, 94.6% and 50.4% of SS, color and COD removals, respectively. The percentage difference recorded between experimental and model responses was <5%. Therefore, it can be concluded that RSM was an appropriate optimization tool for coagulation and flocculation process.

Quality by design: optimization of a liquid filled pH-responsive macroparticles using Draper-Lin composite design.

PubMed

Rafati, Hasan; Talebpour, Zahra; Adlnasab, Laleh; Ebrahimi, Samad Nejad

2009-07-01

In this study, pH responsive macroparticles incorporating peppermint oil (PO) were prepared using a simple emulsification/polymer precipitation technique. The formulations were examined for their properties and the desired quality was then achieved using a quality by design (QBD) approach. For this purpose, a Draper-Lin small composite design study was employed in order to investigate the effect of four independent variables, including the PO to water ratio, the concentration of pH sensitive polymer (hydroxypropyl methylcellulose phthalate), acid and plasticizer concentrations, on the encapsulation efficiency and PO loading. The analysis of variance showed that the polymer concentration was the most important variable on encapsulation efficiency (p < 0.05). The multiple regression analysis of the results led to equations that adequately described the influence of the independent variables on the selected responses. Furthermore, the desirability function was employed as an effective tool for transforming each response separately and encompassing all of these responses in an overall desirability function for global optimization of the encapsulation process. The optimized macroparticles were predicted to yield 93.4% encapsulation efficiency and 72.8% PO loading, which were remarkably close to the experimental values of 89.2% and 69.5%, consequently.

In vitro blood and fibroblast responses to BisGMA-TEGDMA/bioactive glass composite implants.

PubMed

Abdulmajeed, Aous A; Kokkari, Anne K; Käpylä, Jarmo; Massera, Jonathan; Hupa, Leena; Vallittu, Pekka K; Närhi, Timo O

2014-01-01

This in vitro study was designed to evaluate both blood and human gingival fibroblast responses to bisphenol A-glycidyl methacrylate-triethyleneglycol dimethacrylate (BisGMA-TEGDMA)/bioactive glass (BAG) composite, aimed to be used as composite implant abutment surface modifier. Three different types of substrates were investigated: (a) plain polymer (BisGMA 50 wt%-TEGDMA 50 wt%), (b) BAG-composite (50 wt% polymer + 50 wt% fraction of BAG-particles, <50 μm), and (c) plain BAG plates (100 wt% BAG). The blood response, including the blood-clotting ability and platelet adhesion morphology were evaluated. Human gingival fibroblasts were plated and cultured on the experimental substrates for up to 10 days, then the cell proliferation rate was assessed using AlamarBlue assay™. The BAG-composite and plain BAG substrates had a shorter clotting time than plain polymer substrates. Platelet activation and aggregation were most extensive, qualitatively, on BAG-composite. Analysis of the normalized cell proliferation rate on the different surfaces showed some variations throughout the experiment, however, by day 10 the BAG-composite substrate showed the highest (P < 0.001) cell proliferation rate. In conclusion, the presence of exposed BAG-particles enhances fibroblast and blood responses on composite surfaces in vitro.

Composite panel development at JPL

NASA Technical Reports Server (NTRS)

Mcelroy, Paul; Helms, Rich

1988-01-01

Parametric computer studies can be use in a cost effective manner to determine optimized composite mirror panel designs. An InterDisciplinary computer Model (IDM) was created to aid in the development of high precision reflector panels for LDR. The materials properties, thermal responses, structural geometries, and radio/optical precision are synergistically analyzed for specific panel designs. Promising panels designs are fabricated and tested so that comparison with panel test results can be used to verify performance prediction models and accommodate design refinement. The iterative approach of computer design and model refinement with performance testing and materials optimization has shown good results for LDR panels.

Effect of Discontinuities and Uncertainties on the Response and Failure of Composite Structures

NASA Technical Reports Server (NTRS)

Noor, Ahmed K.; Perry, Ferman W.; Poteat, Marcia M. (Technical Monitor)

2000-01-01

The overall goal of this research was to assess the effect of discontinuities and uncertainties on the nonlinear response and failure of composite structures subjected to combined mechanical and thermal loads. The four key elements of the study were: (1) development of simple and efficient procedures for the accurate determination of transverse shear and transverse normal stresses in structural sandwiches as well as in unstiffened and stiffened composite panels and shells; (2) study the effects of transverse stresses on the response, damage initiation and propagation in composite and sandwich structures; (3) use of hierarchical sensitivity coefficients to identify the major parameters that affect the response and damage in each of the different levels in the hierarchy (micro-mechanical, layer, panel, subcomponent and component levels); and (4) application of fuzzy set techniques to identify the range and variation of possible responses. The computational models developed were used in conjunction with experiments, to understand the physical phenomena associated with the nonlinear response and failure of composite and sandwich structures. A toolkit was developed for use in conjunction with deterministic analysis programs to help the designer in assessing the effect of uncertainties in the different computational model parameters on the variability of the response quantities.

Optimization of Mineral Separator for Recovery of Total Heavy Minerals of Bay of Bengal using Central Composite Design

NASA Astrophysics Data System (ADS)

Routray, Sunita; Swain, Ranjita; Rao, Raghupatruni Bhima

2017-04-01

The present study is aimed at investigating the optimization of a mineral separator for processing of beach sand minerals of Bay of Bengal along Ganjam-Rushikulya coast. The central composite design matrix and response surface methodology were applied in designing the experiments to evaluate the interactive effects of the three most important operating variables, such as feed quantity, wash water rate and Shake amplitude of the deck. The predicted values were found to be in good agreement with the experimental values (R2 = 0.97 for grade and 0.98 for recovery). To understand the impact of each variable, three dimensional (3D) plots were also developed for the estimated responses.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2017-09-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Numerical Simulation of Thermal Response and Ablation Behavior of a Hybrid Carbon/Carbon Composite

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-06-01

The thermal response and ablation behavior of a hybrid carbon/carbon (C/C) composite are studied herein by using a numerical model. This model is based on the energy- and mass-conservation principles as well as on the calculation of the thermophysical properties of materials. The thermal response and ablation behavior are simulated from the perspective of the matrix and fiber components of a hybrid C/C composite. The thermophysical properties during ablation are calculated, and a moving boundary is implemented to consider the recession of the ablation surface. The temperature distribution, thermophysical properties, char layer thickness, linear ablation rate, mass flow rate of the pyrolysis gases, and mass loss of the hybrid C/C composite are quantitatively predicted. This numerical study describing the thermal response and ablation behavior provides a fundamental understanding of the ablative mechanism of a hybrid C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Compositionally Graded Multilayer Ceramic Capacitors

DOE PAGES

Song, Hyun-Cheol; Zhou, Jie E.; Maurya, Deepam; ...

2017-09-27

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. In this paper, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters andmore » power converters.« less

Thermal response of a 4D carbon/carbon composite with volume ablation: a numerical simulation study

NASA Astrophysics Data System (ADS)

Zhang, Bai; Li, Xudong

2018-02-01

As carbon/carbon composites usually work at high temperature environments, material ablation inevitably occurs, which further affects the system stability and safety. In this paper, the thermal response of a thermoprotective four-directional carbon/carbon (4D C/C) composite is studied herein using a numerical model focusing on volume ablation. The model is based on energy- and mass-conservation principles as well as on the thermal decomposition equation of solid materials. The thermophysical properties of the C/C composite during the ablation process are calculated, and the thermal response during ablation, including temperature distribution, density, decomposition rate, char layer thickness, and mass loss, are quantitatively predicted. The present numerical study provides a fundamental understanding of the ablative mechanisms of a 4D C/C composite, serving as a reference and basis for further designs and optimizations of thermoprotective materials.

Novel Composites for Wing and Fuselage Applications: Speedy Nonlinear Analysis of Postbuckled Panels in Shear (SNAPPS)

NASA Technical Reports Server (NTRS)

Sharp, Dave; Sobel, Larry

1997-01-01

A simple and rapid analysis method, consisting of a number of modular, 'strength-of-materials-type' models, is presented for predicting the nonlinear response and stiffener separation of postbuckled, flat, composite, shear panels. The analysis determines the maximum principal tensile stress in the skin surface layer under to toe. Failure is said to occur when this stress reaches the mean transverse tensile strength of the layer. The analysis methodology consists of a number of closed-form equations that can easily be used in a 'hand analysis. For expediency, they have been programmed into a preliminary design code called SNAPPS (Speedy Nonlinear Analysis of Postbuckled Panels in Shear), which rapidly predicts postbuckling response of the panel for each value of the applied shear load. SNAPPS response and failure predictions were found to agree well with test results for three panels with widely different geometries, laminates and stiffnesses. Design guidelines are given for increasing the load-carrying capacity of stiffened, composite shear panels.

Composite materials. Volume 3 - Engineering applications of composites. Volume 4 - Metallic matrix composites. Volume 8 - Structural design and analysis, Part 2

NASA Technical Reports Server (NTRS)

Noton, B. R. (Editor); Kreider, K. G.; Chamis, C. C.

1974-01-01

This volume discusses a vaety of applications of both low- and high-cost composite materials in a number of selected engineering fields. The text stresses the use of fiber-reinforced composites, along with interesting material systems used in the electrical and nuclear industries. As to technology transfer, a similarity is noted between many of the reasons responsible for the utilization of composites and those problems requiring urgent solution, such as mechanized fabrication processes and design for production. Features topics include road transportation, rail transportation, civil aircraft, space vehicles, builing industry, chemical plants, and appliances and equipment. The laminate orientation code devised by Air Force materials laboratory is included. Individual items are announced in this issue.

Soft network composite materials with deterministic and bio-inspired designs

PubMed Central

Jang, Kyung-In; Chung, Ha Uk; Xu, Sheng; Lee, Chi Hwan; Luan, Haiwen; Jeong, Jaewoong; Cheng, Huanyu; Kim, Gwang-Tae; Han, Sang Youn; Lee, Jung Woo; Kim, Jeonghyun; Cho, Moongee; Miao, Fuxing; Yang, Yiyuan; Jung, Han Na; Flavin, Matthew; Liu, Howard; Kong, Gil Woo; Yu, Ki Jun; Rhee, Sang Il; Chung, Jeahoon; Kim, Byunggik; Kwak, Jean Won; Yun, Myoung Hee; Kim, Jin Young; Song, Young Min; Paik, Ungyu; Zhang, Yihui; Huang, Yonggang; Rogers, John A.

2015-01-01

Hard and soft structural composites found in biology provide inspiration for the design of advanced synthetic materials. Many examples of bio-inspired hard materials can be found in the literature; far less attention has been devoted to soft systems. Here we introduce deterministic routes to low-modulus thin film materials with stress/strain responses that can be tailored precisely to match the non-linear properties of biological tissues, with application opportunities that range from soft biomedical devices to constructs for tissue engineering. The approach combines a low-modulus matrix with an open, stretchable network as a structural reinforcement that can yield classes of composites with a wide range of desired mechanical responses, including anisotropic, spatially heterogeneous, hierarchical and self-similar designs. Demonstrative application examples in thin, skin-mounted electrophysiological sensors with mechanics precisely matched to the human epidermis and in soft, hydrogel-based vehicles for triggered drug release suggest their broad potential uses in biomedical devices. PMID:25782446

Influence of material anisotropy on the hydroelastic response of composite plates in water

NASA Astrophysics Data System (ADS)

Akcabay, Deniz Tolga; Young, Yin Lu

2018-03-01

Flexible lightweight plate-like lifting surfaces in external flows have a diverse range of use from propelling and controlling marine and aerospace vehicles to converting wind and ocean energy to electrical energy. Design and analysis of such structures are complex for underwater applications where the water density is much higher than air. The hydrodynamic loads, which vary with the inflow speed, can significantly alter the dynamic response and stability. This paper focuses on the hydroelastic response of composite plates in water. The results show that the dynamics and stability of the structure can be significantly modified by taking advantage of the material anisotropic; on the contrary, careless composite material designs may lead to unwanted dynamic instability failures. The resonance frequencies, divergence speeds, and fluid loss coefficients change with material anisotropy and hydrodynamic loads. The resonance frequencies are much lower in water than in air. The critical divergence speed increases, if the principal fiber direction is oriented towards the inflow. Hydrodynamic damping is shown to be much higher than the material damping, and tend to increase with flow speed and to decrease with increasing modal frequency. The paper derives Response Amplitude Operators (RAOs) for sample composite plates in water and use them to predict the motion response when subject to stochastic flow excitations. We show how material anisotropy can be used to passively tailor the plate vibration response spectrum to limit or enhance flow-induced vibrations of the plate depending on the desired applications.

Nonlinearity and Strain-Rate Dependence in the Deformation Response of Polymer Matrix Composites Modeled

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

2000-01-01

There has been no accurate procedure for modeling the high-speed impact of composite materials, but such an analytical capability will be required in designing reliable lightweight engine-containment systems. The majority of the models in use assume a linear elastic material response that does not vary with strain rate. However, for containment systems, polymer matrix composites incorporating ductile polymers are likely to be used. For such a material, the deformation response is likely to be nonlinear and to vary with strain rate. An analytical model has been developed at the NASA Glenn Research Center at Lewis Field that incorporates both of these features. A set of constitutive equations that was originally developed to analyze the viscoplastic deformation of metals (Ramaswamy-Stouffer equations) was modified to simulate the nonlinear, rate-dependent deformation of polymers. Specifically, the effects of hydrostatic stresses on the inelastic response, which can be significant in polymers, were accounted for by a modification of the definition of the effective stress. The constitutive equations were then incorporated into a composite micromechanics model based on the mechanics of materials theory. This theory predicts the deformation response of a composite material from the properties and behavior of the individual constituents. In this manner, the nonlinear, rate-dependent deformation response of a polymer matrix composite can be predicted.

Relationship between mechanical-property and energy-absorption trends for composite tubes

NASA Technical Reports Server (NTRS)

Farley, Gary L.

1992-01-01

U.S. Army helicopters are designed to dissipate prescribed levels of crash impact kinetic energy without compromising the integrity of the fuselage. Because of the complexity of the energy-absorption process it is imperative for designers of energy-absorbing structures to develop an in-depth understanding of how and why composite structures absorb energy. A description of the crushing modes and mechanisms of energy absorption for composite tubes and beams is presented. Three primary crushing modes of composite structures including transverse shearing, lamina bending, and local buckling are described. The experimental data presented show that fiber and matrix mechanical properties and laminate stiffness and strength mechanical properties cannot reliably predict the energy-absorption response of composite tubes.

A review of failure models for unidirectional ceramic matrix composites under monotonic loads

NASA Technical Reports Server (NTRS)

Tripp, David E.; Hemann, John H.; Gyekenyesi, John P.

1989-01-01

Ceramic matrix composites offer significant potential for improving the performance of turbine engines. In order to achieve their potential, however, improvements in design methodology are needed. In the past most components using structural ceramic matrix composites were designed by trial and error since the emphasis of feasibility demonstration minimized the development of mathematical models. To understand the key parameters controlling response and the mechanics of failure, the development of structural failure models is required. A review of short term failure models with potential for ceramic matrix composite laminates under monotonic loads is presented. Phenomenological, semi-empirical, shear-lag, fracture mechanics, damage mechanics, and statistical models for the fast fracture analysis of continuous fiber unidirectional ceramic matrix composites under monotonic loads are surveyed.

Impact evaluation of composite floor sections

NASA Technical Reports Server (NTRS)

Boitnott, Richard L.; Fasanella, Edwin L.

1989-01-01

Graphite-epoxy floor sections representative of aircraft fuselage construction were statically and dynamically tested to evaluate their response to crash loadings. These floor sections were fabricated using a frame-stringer design typical of present aluminum aircraft without features to enhance crashworthiness. The floor sections were tested as part of a systematic research program developed to study the impact response of composite components of increasing complexity. The ultimate goal of the research program is to develop crashworthy design features for future composite aircraft. Initially, individual frames of six-foot diameter were tested both statically and dynamically. The frames were then used to construct built-up floor sections for dynamic tests at impact velocities of approximately 20 feet/sec to simulate survivable crash velocities. In addition, static tests were conducted to gain a better understanding of the failure mechanisms seen in the dynamic tests.

Design and characterization of dielectric subwavelength focusing lens with polarization dependence

NASA Astrophysics Data System (ADS)

Kim, Sung W.; Pang, Lin; Fainman, Yeshaiahu

2016-03-01

We introduce and develop design, fabrication and characterization methodology for engineering the effective refractive index of a composite dielectric planar surface created by controlling the density of deeply subwavelength low index nanoholes (e.g., air) in a high index dielectric layer (e.g., Si). The nanoscale properties of a composite dielectric layer allows for full control of the optical wavefront phase by designing arbitrary space-variant refractive index profiles. We present the composite dielectric metasurface microlens exploiting symmetric design to achieve polarization invariant impulse response, and use asymmetric design to demonstrate polarization sensitive impulse response of the lens. This composite dielectric layers lenses were fabricated by patterning nanohole distributions on a dielectric surface and etching to submicron depths. Our dielectric microlens with asymmetric distribution of neff (neff x ≠ neff y) demonstrates a graded index lens with polarization dependent focusing with of 32um and 22 um for linearly x- and y-polarized light, respectively operating at a wavelength of λ = 1550nm. We also show numerically and demonstrate experimentally achromatic performance of the devices operating in the wavelength range of 1500nm - 1900nm with FWHM of the focal spots of about 4um. Namely, we have constructed a graded index lens that can overcome diffraction effects even when aperture/wavelength (D/λ) is smaller than 40. The demonstrated novel approach to engineer dielectric composite nanosurfaces has the potential to realize arbitrary phase functions with minimal insertion loss, submicron thickness and miniaturization to reduce element size and weight, and may have a significant impact on numerous miniature imaging systems applications.

Statistical optimization of process parameters for lipase-catalyzed synthesis of triethanolamine-based esterquats using response surface methodology in 2-liter bioreactor.

PubMed

Masoumi, Hamid Reza Fard; Basri, Mahiran; Kassim, Anuar; Abdullah, Dzulkefly Kuang; Abdollahi, Yadollah; Abd Gani, Siti Salwa; Rezaee, Malahat

2013-01-01

Lipase-catalyzed production of triethanolamine-based esterquat by esterification of oleic acid (OA) with triethanolamine (TEA) in n-hexane was performed in 2 L stirred-tank reactor. A set of experiments was designed by central composite design to process modeling and statistically evaluate the findings. Five independent process variables, including enzyme amount, reaction time, reaction temperature, substrates molar ratio of OA to TEA, and agitation speed, were studied under the given conditions designed by Design Expert software. Experimental data were examined for normality test before data processing stage and skewness and kurtosis indices were determined. The mathematical model developed was found to be adequate and statistically accurate to predict the optimum conversion of product. Response surface methodology with central composite design gave the best performance in this study, and the methodology as a whole has been proven to be adequate for the design and optimization of the enzymatic process.

Supporting Creative Responses in Design Education--The Development and Application of the Graphic Design Composition Method

ERIC Educational Resources Information Center

Lu, Hui-Ping; Chen, Jun-Hong; Lee, Chang-Franw

2016-01-01

Inspiration is the primary element of good design. Designers, however, also risk not being able to find inspiration. Novice designers commonly find themselves to be depressed during the conceptual design phase when they fail to find inspiration and the information to be creative. Accordingly, under the graphic design parameter, we have developed…

Structural tailoring of engine blades (STAEBL) user's manual

NASA Technical Reports Server (NTRS)

Brown, K. W.

1985-01-01

This User's Manual contains instructions and demonstration case to prepare input data, run, and modify the Structural Tailoring of Engine Blades (STAEBL) computer code. STAEBL was developed to perform engine fan and compressor blade numerical optimizations. This blade optimization seeks a minimum weight or cost design that satisfies realistic blade design constraints, by tuning one to twenty design variables. The STAEBL constraint analyses include blade stresses, vibratory response, flutter, and foreign object damage. Blade design variables include airfoil thickness at several locations, blade chord, and construction variables: hole size for hollow blades, and composite material layup for composite blades.

Motion Cues in Flight Simulation and Simulator Induced Sickness

DTIC Science & Technology

1988-06-01

asseusod in a driving simulator by means of a response surface methodology central-composite design . The most salient finding of the study was that visual...across treatment conditions. For an orthogonal response surface methodology (IBM) design with only tro independent variables. it can be readily shown that...J.E.Fowikes 8 SESSION III - ETIOLOGICAL FACTORS IN SIMULATOR-INDUCED AFTER EFFETS THE USE OF VE& IIBULAR MODELS FOR DESIGN AND EVALUATION OF FLIGHT

Nonlinear analyses of composite aerospace structures in sonic fatigue

NASA Technical Reports Server (NTRS)

Mei, Chuh

1993-01-01

This report summarizes the semiannual research progress, accomplishments, and future plans performed under the NASA Langley Research Center Grant No. NAG-1-1358. The primary research effort of this project is the development of analytical methods for the prediction of nonlinear random response of composite aerospace structures subjected to combined acoustic and thermal loads. The progress, accomplishments, and future plates on four sonic fatigue research topics are described. The sonic fatigue design and passive control of random response of shape memory alloy hybrid composites presented in section 4, which is suited especially for HSCT, is a new initiative.

Nonlinear analyses of composite aerospace structures in sonic fatigue

NASA Astrophysics Data System (ADS)

Mei, Chuh

1993-06-01

This report summarizes the semiannual research progress, accomplishments, and future plans performed under the NASA Langley Research Center Grant No. NAG-1-1358. The primary research effort of this project is the development of analytical methods for the prediction of nonlinear random response of composite aerospace structures subjected to combined acoustic and thermal loads. The progress, accomplishments, and future plates on four sonic fatigue research topics are described. The sonic fatigue design and passive control of random response of shape memory alloy hybrid composites presented in section 4, which is suited especially for HSCT, is a new initiative.

Verification and Validation Process for Progressive Damage and Failure Analysis Methods in the NASA Advanced Composites Consortium

NASA Technical Reports Server (NTRS)

Wanthal, Steven; Schaefer, Joseph; Justusson, Brian; Hyder, Imran; Engelstad, Stephen; Rose, Cheryl

2017-01-01

The Advanced Composites Consortium is a US Government/Industry partnership supporting technologies to enable timeline and cost reduction in the development of certified composite aerospace structures. A key component of the consortium's approach is the development and validation of improved progressive damage and failure analysis methods for composite structures. These methods will enable increased use of simulations in design trade studies and detailed design development, and thereby enable more targeted physical test programs to validate designs. To accomplish this goal with confidence, a rigorous verification and validation process was developed. The process was used to evaluate analysis methods and associated implementation requirements to ensure calculation accuracy and to gage predictability for composite failure modes of interest. This paper introduces the verification and validation process developed by the consortium during the Phase I effort of the Advanced Composites Project. Specific structural failure modes of interest are first identified, and a subset of standard composite test articles are proposed to interrogate a progressive damage analysis method's ability to predict each failure mode of interest. Test articles are designed to capture the underlying composite material constitutive response as well as the interaction of failure modes representing typical failure patterns observed in aerospace structures.

Reliability-Based Design Optimization of a Composite Airframe Component

NASA Technical Reports Server (NTRS)

Pai, Shantaram S.; Coroneos, Rula; Patnaik, Surya N.

2011-01-01

A stochastic optimization methodology (SDO) has been developed to design airframe structural components made of metallic and composite materials. The design method accommodates uncertainties in load, strength, and material properties that are defined by distribution functions with mean values and standard deviations. A response parameter, like a failure mode, has become a function of reliability. The primitive variables like thermomechanical loads, material properties, and failure theories, as well as variables like depth of beam or thickness of a membrane, are considered random parameters with specified distribution functions defined by mean values and standard deviations.

A Multiscale, Nonlinear, Modeling Framework Enabling the Design and Analysis of Composite Materials and Structures

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2012-01-01

A framework for the multiscale design and analysis of composite materials and structures is presented. The ImMAC software suite, developed at NASA Glenn Research Center, embeds efficient, nonlinear micromechanics capabilities within higher scale structural analysis methods such as finite element analysis. The result is an integrated, multiscale tool that relates global loading to the constituent scale, captures nonlinearities at this scale, and homogenizes local nonlinearities to predict their effects at the structural scale. Example applications of the multiscale framework are presented for the stochastic progressive failure of a SiC/Ti composite tensile specimen and the effects of microstructural variations on the nonlinear response of woven polymer matrix composites.

A Multiscale, Nonlinear, Modeling Framework Enabling the Design and Analysis of Composite Materials and Structures

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2011-01-01

A framework for the multiscale design and analysis of composite materials and structures is presented. The ImMAC software suite, developed at NASA Glenn Research Center, embeds efficient, nonlinear micromechanics capabilities within higher scale structural analysis methods such as finite element analysis. The result is an integrated, multiscale tool that relates global loading to the constituent scale, captures nonlinearities at this scale, and homogenizes local nonlinearities to predict their effects at the structural scale. Example applications of the multiscale framework are presented for the stochastic progressive failure of a SiC/Ti composite tensile specimen and the effects of microstructural variations on the nonlinear response of woven polymer matrix composites.

Estimation of Supersonic Stage Separation Aerodynamics of Winged-Body Launch Vehicles Using Response Surface Methods

NASA Technical Reports Server (NTRS)

Erickson, Gary E.; Deloach, Richard

2008-01-01

A collection of statistical and mathematical techniques referred to as response surface methodology was used to estimate the longitudinal stage separation aerodynamic characteristics of a generic, bimese, winged multi-stage launch vehicle configuration using data obtained on small-scale models at supersonic speeds in the NASA Langley Research Center Unitary Plan Wind Tunnel. The simulated Mach 3 staging was dominated by multiple shock wave interactions between the orbiter and booster vehicles throughout the relative spatial locations of interest. This motivated a partitioning of the overall inference space into several contiguous regions within which the separation aerodynamics were presumed to be well-behaved and estimable using cuboidal and spherical central composite designs capable of fitting full second-order response functions. The primary goal was to approximate the underlying overall aerodynamic response surfaces of the booster vehicle in belly-to-belly proximity to the orbiter vehicle using relatively simple, lower-order polynomial functions that were piecewise-continuous across the full independent variable ranges of interest. The quality of fit and prediction capabilities of the empirical models were assessed in detail, and the issue of subspace boundary discontinuities was addressed. The potential benefits of augmenting the central composite designs to full third order using computer-generated D-optimality criteria were also evaluated. The usefulness of central composite designs, the subspace sizing, and the practicality of fitting low-order response functions over a partitioned inference space dominated by highly nonlinear and possibly discontinuous shock-induced aerodynamics are discussed.

Highly Loaded Composite Strut Test Development

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey; Phelps, James E.; McKenney, Martin J.; Jegley, Dawn C.

2011-01-01

Highly loaded composite struts, representative of structural elements of a proposed truss-based lunar lander descent stage concept, were selected for design, development, fabrication and testing under NASA s Advanced Composites Technology program. The focus of this paper is the development of a capability for experimental evaluation of the structural performance of these struts. Strut lengths range from 60 to over 120 inches, and compressive launch and ascent loads can exceed -100,000 lbs, or approximately two times the corresponding tensile loads. Allowing all possible compressive structural responses, including elastic buckling, were primary considerations for designing the test hardware.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Song, Hyun-Cheol; Zhou, Jie E.; Maurya, Deepam

Multilayer ceramic capacitors (MLCC) are widely used in consumer electronics. In this paper, we provide a transformative method for achieving high dielectric response and tunability over a wide temperature range through design of compositionally graded multilayer (CGML) architecture. Compositionally graded MLCCs were found to exhibit enhanced dielectric tunability (70%) along with small dielectric losses (<2.5%) over the required temperature ranges specified in the standard industrial classifications. The compositional grading resulted in generation of internal bias field which enhanced the tunability due to increased nonlinearity. The electric field tunability of MLCCs provides an important avenue for design of miniature filters andmore » power converters.« less

Advanced organic composite materials for aircraft structures: Future program

NASA Technical Reports Server (NTRS)

1987-01-01

Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

Optimum design of structures of composite materials in response to aerodynamic noise and noise transmission

NASA Technical Reports Server (NTRS)

Yang, J. C. S.; Tsui, C. Y.

1977-01-01

Elastic wave propagation and attenuation in a model fiber matrix was investigated. Damping characteristics in graphite epoxy composite materials were measured. A sound transmission test facility suitable to incorporate into NASA Ames wind tunnel for measurement of transmission loss due to sound generation in boundary layers was constructed. Measurement of transmission loss of graphite epoxy composite panels was also included.

Optimization of Lipase production from a novel strain Thalassospira permensis M35-15 using Response Surface Methodology

PubMed Central

Kai, Wang; Peisheng, Yan

2016-01-01

ABSTRACT Lipases can catalyze the hydrolysis of glycerol, esters and long chain fatty acids. A lipase producing isolate M35-15 was screened and identified as Thalassospira permensis using 16S rRNA gene sequence analysis. To our knowledge this is the first report on Thalassospira permensis producing lipases. In this paper the optimization of medium composition for the increase in bacterial lipase was achieved using statistical methods. Firstly the key ingredients were selected by Plackett-Burman experimental design, then the levels of the ingredients were optimized using central composite design of Response Surface Methodology. The predicted optimal lipase activity was 11.49 U under the conditions that medium composition were 5.15 g/l glucose, 11.74 g/l peptone, 6.74 g/l yeast powder and 22.90 g/l olive oil emulsifier. PMID:27285376

Optimization of Lipase production from a novel strain Thalassospira permensis M35-15 using Response Surface Methodology.

PubMed

Kai, Wang; Peisheng, Yan

2016-09-02

Lipases can catalyze the hydrolysis of glycerol, esters and long chain fatty acids. A lipase producing isolate M35-15 was screened and identified as Thalassospira permensis using 16S rRNA gene sequence analysis. To our knowledge this is the first report on Thalassospira permensis producing lipases. In this paper the optimization of medium composition for the increase in bacterial lipase was achieved using statistical methods. Firstly the key ingredients were selected by Plackett-Burman experimental design, then the levels of the ingredients were optimized using central composite design of Response Surface Methodology. The predicted optimal lipase activity was 11.49 U under the conditions that medium composition were 5.15 g/l glucose, 11.74 g/l peptone, 6.74 g/l yeast powder and 22.90 g/l olive oil emulsifier.

Properties Of Carbon/Carbon and Carbon/Phenolic Composites

NASA Technical Reports Server (NTRS)

Mathis, John R.; Canfield, A. R.

1993-01-01

Report presents data on physical properties of carbon-fiber-reinforced carbon-matrix and phenolic-matrix composite materials. Based on tests conducted on panels, cylinders, blocks, and formed parts. Data used by designers to analyze thermal-response and stress levels and develop structural systems ensuring high reliability at minimum weight.

Dynamic Response of Functionally Graded Carbon Nanotube Reinforced Sandwich Plate

NASA Astrophysics Data System (ADS)

Mehar, Kulmani; Panda, Subrata Kumar

2018-03-01

In this article, the dynamic response of the carbon nanotube-reinforced functionally graded sandwich composite plate has been studied numerically with the help of finite element method. The face sheets of the sandwich composite plate are made of carbon nanotube- reinforced composite for two different grading patterns whereas the core phase is taken as isotropic material. The final properties of the structure are calculated using the rule of mixture. The geometrical model of the sandwich plate is developed and discretized suitably with the help of available shell element in ANSYS library. Subsequently, the corresponding numerical dynamic responses computed via batch input technique (parametric design language code in ANSYS) of ANSYS including Newmark’s integration scheme. The stability of the sandwich structural numerical model is established through the proper convergence study. Further, the reliability of the sandwich model is checked by comparison study between present and available results from references. As a final point, some numerical problems have been solved to examine the effect of different design constraints (carbon nanotube distribution pattern, core to face thickness ratio, volume fractions of the nanotube, length to thickness ratio, aspect ratio and constraints at edges) on the time-responses of sandwich plate.

Design Optimization and Residual Strength Assessment of a Cylindrical Composite Shell Structure

NASA Technical Reports Server (NTRS)

Rais-Rohani, Masoud

2000-01-01

A summary of research conducted during the specified period is presented. The research objectives included the investigation of an efficient technique for the design optimization and residual strength assessment of a semi-monocoque cylindrical shell structure made of composite materials. The response surface methodology is used in modeling the buckling response of individual skin panels under the combined axial compression and shear loading. These models are inserted into the MSC/NASTRAN code for design optimization of the cylindrical structure under a combined bending-torsion loading condition. The comparison between the monolithic and sandwich skin design cases indicated a 35% weight saving in using sandwich skin panels. In addition, the residual strength of the optimum design was obtained by identifying the most critical region of the structure and introducing a damage in the form of skin-stringer and skin-stringer-frame detachment. The comparison between the two skin design concepts indicated that the sandwich skin design is capable of retaining a higher residual strength than its monolithic counterpart. The results of this investigation are presented and discussed in this report.

Predicting the influence of liposomal lipid composition on liposome size, zeta potential and liposome-induced dendritic cell maturation using a design of experiments approach.

PubMed

Soema, Peter C; Willems, Geert-Jan; Jiskoot, Wim; Amorij, Jean-Pierre; Kersten, Gideon F

2015-08-01

In this study, the effect of liposomal lipid composition on the physicochemical characteristics and adjuvanticity of liposomes was investigated. Using a design of experiments (DoE) approach, peptide-containing liposomes containing various lipids (EPC, DOPE, DOTAP and DC-Chol) and peptide concentrations were formulated. Liposome size and zeta potential were determined for each formulation. Moreover, the adjuvanticity of the liposomes was assessed in an in vitro dendritic cell (DC) model, by quantifying the expression of DC maturation markers CD40, CD80, CD83 and CD86. The acquired data of these liposome characteristics were successfully fitted with regression models, and response contour plots were generated for each response factor. These models were applied to predict a lipid composition that resulted in a liposome with a target zeta potential. Subsequently, the expression of the DC maturation factors for this lipid composition was predicted and tested in vitro; the acquired maturation responses corresponded well with the predicted ones. These results show that a DoE approach can be used to screen various lipids and lipid compositions, and to predict their impact on liposome size, charge and adjuvanticity. Using such an approach may accelerate the formulation development of liposomal vaccine adjuvants. Copyright © 2015 The Authors. Published by Elsevier B.V. All rights reserved.

Application of a design-build-team approach to low cost and weight composite fuselage structure

NASA Technical Reports Server (NTRS)

Ilcewicz, L. B.; Walker, T. H.; Willden, K. S.; Swanson, G. D.; Truslove, G.; Metschan, S. L.; Pfahl, C. L.

1991-01-01

Relationships between manufacturing costs and design details must be understood to promote the application of advanced composite technologies to transport fuselage structures. A team approach, integrating the disciplines responsible for aircraft structural design and manufacturing, was developed to perform cost and weight trade studies for a twenty-foot diameter aft fuselage section. Baseline composite design and manufacturing concepts were selected for large quadrant panels in crown, side, and keel areas of the fuselage section. The associated technical issues were also identified. Detailed evaluation of crown panels indicated the potential for large weight savings and costs competitive with aluminum technology in the 1995 timeframe. Different processes and material forms were selected for the various elements that comprise the fuselage structure. Additional cost and weight savings potential was estimated for future advancements.

Process Integration and Optimization of ICME Carbon Fiber Composites for Vehicle Lightweighting: A Preliminary Development

DOE PAGES

Xu, Hongyi; Li, Yang; Zeng, Danielle

2017-01-02

Process integration and optimization is the key enabler of the Integrated Computational Materials Engineering (ICME) of carbon fiber composites. In this paper, automated workflows are developed for two types of composites: Sheet Molding Compounds (SMC) short fiber composites, and multi-layer unidirectional (UD) composites. For SMC, the proposed workflow integrates material processing simulation, microstructure representation volume element (RVE) models, material property prediction and structure preformation simulation to enable multiscale, multidisciplinary analysis and design. Processing parameters, microstructure parameters and vehicle subframe geometry parameters are defined as the design variables; the stiffness and weight of the structure are defined as the responses. Formore » multi-layer UD structure, this work focuses on the discussion of different design representation methods and their impacts on the optimization performance. Challenges in ICME process integration and optimization are also summarized and highlighted. Two case studies are conducted to demonstrate the integrated process and its application in optimization.« less

LS-DYNA Implementation of Polymer Matrix Composite Model Under High Strain Rate Impact

NASA Technical Reports Server (NTRS)

Zheng, Xia-Hua; Goldberg, Robert K.; Binienda, Wieslaw K.; Roberts, Gary D.

2003-01-01

A recently developed constitutive model is implemented into LS-DYNA as a user defined material model (UMAT) to characterize the nonlinear strain rate dependent behavior of polymers. By utilizing this model within a micromechanics technique based on a laminate analogy, an algorithm to analyze the strain rate dependent, nonlinear deformation of a fiber reinforced polymer matrix composite is then developed as a UMAT to simulate the response of these composites under high strain rate impact. The models are designed for shell elements in order to ensure computational efficiency. Experimental and numerical stress-strain curves are compared for two representative polymers and a representative polymer matrix composite, with the analytical model predicting the experimental response reasonably well.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Hongyi; Li, Yang; Zeng, Danielle

Process integration and optimization is the key enabler of the Integrated Computational Materials Engineering (ICME) of carbon fiber composites. In this paper, automated workflows are developed for two types of composites: Sheet Molding Compounds (SMC) short fiber composites, and multi-layer unidirectional (UD) composites. For SMC, the proposed workflow integrates material processing simulation, microstructure representation volume element (RVE) models, material property prediction and structure preformation simulation to enable multiscale, multidisciplinary analysis and design. Processing parameters, microstructure parameters and vehicle subframe geometry parameters are defined as the design variables; the stiffness and weight of the structure are defined as the responses. Formore » multi-layer UD structure, this work focuses on the discussion of different design representation methods and their impacts on the optimization performance. Challenges in ICME process integration and optimization are also summarized and highlighted. Two case studies are conducted to demonstrate the integrated process and its application in optimization.« less

Modeling and additive manufacturing of bio-inspired composites with tunable fracture mechanical properties.

PubMed

Dimas, Leon S; Buehler, Markus J

2014-07-07

Flaws, imperfections and cracks are ubiquitous in material systems and are commonly the catalysts of catastrophic material failure. As stresses and strains tend to concentrate around cracks and imperfections, structures tend to fail far before large regions of material have ever been subjected to significant loading. Therefore, a major challenge in material design is to engineer systems that perform on par with pristine structures despite the presence of imperfections. In this work we integrate knowledge of biological systems with computational modeling and state of the art additive manufacturing to synthesize advanced composites with tunable fracture mechanical properties. Supported by extensive mesoscale computer simulations, we demonstrate the design and manufacturing of composites that exhibit deformation mechanisms characteristic of pristine systems, featuring flaw-tolerant properties. We analyze the results by directly comparing strain fields for the synthesized composites, obtained through digital image correlation (DIC), and the computationally tested composites. Moreover, we plot Ashby diagrams for the range of simulated and experimental composites. Our findings show good agreement between simulation and experiment, confirming that the proposed mechanisms have a significant potential for vastly improving the fracture response of composite materials. We elucidate the role of stiffness ratio variations of composite constituents as an important feature in determining the composite properties. Moreover, our work validates the predictive ability of our models, presenting them as useful tools for guiding further material design. This work enables the tailored design and manufacturing of composites assembled from inferior building blocks, that obtain optimal combinations of stiffness and toughness.

Optimization of a GO2/GH2 Swirl Coaxial Injector Element

NASA Technical Reports Server (NTRS)

Tucker, P. Kevin; Shyy, Wei; Vaidyanathan, Rajkumar

1999-01-01

An injector optimization methodology, method i, is used to investigate optimal design points for a gaseous oxygen/gaseous hydrogen (GO2/GH2) swirl coaxial injector element. The element is optimized in terms of design variables such as fuel pressure drop, DELTA P(sub f), oxidizer pressure drop, DELTA P(sub 0) combustor length, L(sub comb), and full cone swirl angle, theta, for a given mixture ratio and chamber pressure. Dependent variables such as energy release efficiency, ERE, wall heat flux, Q(sub w) injector heat flux, Q(sub inj), relative combustor weight, W(sub rel), and relative injector cost, C(sub rel), are calculated and then correlated with the design variables. An empirical design methodology is used to generate these responses for 180 combinations of input variables. Method i is then used to generate response surfaces for each dependent variable. Desirability functions based on dependent variable constraints are created and used to facilitate development of composite response surfaces representing some, or all, of the five dependent variables in terms of the input variables. Two examples illustrating the utility and flexibility of method i are discussed in detail. First, joint response surfaces are constructed by sequentially adding dependent variables. Optimum designs are identified after addition of each variable and the effect each variable has on the design is shown. This stepwise demonstration also highlights the importance of including variables such as weight and cost early in the design process. Secondly, using the composite response surface that includes all five dependent variables, unequal weights are assigned to emphasize certain variables relative to others. Here, method i is used to enable objective trade studies on design issues such as component life and thrust to weight ratio.

Application of composite materials to impact-insensitive munitions

NASA Technical Reports Server (NTRS)

Neradka, Vincent F.; Chang, Yale; Grady, Joseph E.; Trowbridge, Daniel A.

1992-01-01

An approach is outlined for developing bullet-impact-insensitive munitions based on composite materials that provide rapid venting of the rocket-motor case. Impact experiments are conducted with test specimens of hybrid laminates of graphite/epoxy and epoxy reinforcing with woven glass fibers. The dynamic strain response and initial impact force are measured with strain gauges, and perforation damage is examined in the plates. The results show that impact damage can be designed by means of parametric variations of the fiber, matrix, and ply orientations. It is suggested that rocket-motor cases can be designed with composite materials to provide rapid venting during the failure mode. The experimental ballistic testing performed provides data that can be used comparatively with analytical data on composite materials.

Handbook of Analytical Methods for Textile Composites

NASA Technical Reports Server (NTRS)

Cox, Brian N.; Flanagan, Gerry

1997-01-01

The purpose of this handbook is to introduce models and computer codes for predicting the properties of textile composites. The handbook includes several models for predicting the stress-strain response all the way to ultimate failure; methods for assessing work of fracture and notch sensitivity; and design rules for avoiding certain critical mechanisms of failure, such as delamination, by proper textile design. The following textiles received some treatment: 2D woven, braided, and knitted/stitched laminates and 3D interlock weaves, and braids.

Beyond the Fear Factor: Work/Family Policies in Academia--Resources or Rewards?

ERIC Educational Resources Information Center

Spalter-Roth, Roberta; Erskine, William

2005-01-01

Several decades ago, as the composition of the workforce changed and married women increased their labor-force participation rates, federal policies were designed to help employees balance work and family responsibilities. And as the gender composition of faculty in colleges and universities increasingly changed as well, a broad-based movement…

The design and fabrication of highly piezoelectric polymeric composites and their use in responsive devices

NASA Astrophysics Data System (ADS)

Baur, Cary Allen

In this work, novel approaches to the design of highly piezoelectric and flexible polymer composites were explored. Diverging from past work focused on the addition of piezoelectric particles into polymer matrices, this research explores the ability to increase the piezoelectric performance of a host polymer through the incorporation of charge via polarizable, organic particles. The ability to insert charge into polymers, known as electrets, is well documented but widely considered impractical because of the low lifetime and temperature resistance of the inserted charge. Through the addition of particles that are polarizable, charge can be inserted into a system in a stable manner that results in highly charged materials with long lifetimes. Here, carbon structures, such as Buckminsterfullerenes (C60) and single-walled nanotubes (SWNTs), were composited into poly(vinylidene difluoride) at very low loading levels (0.05-0.25 wt%), resulting in the ability to insert stable charge into the system. We show that these highly charged systems can result in a doubling of the piezoelectric response of the host polymer when optimized. The low amount of nanoparticle filler required to improve these materials allows for the advantageous properties of the polymer matrix such as flexibility and compliance to be preserved, enabling highly piezoelectric and flexible system. This dissertation outlines research efforts towards the design and fabrication of 1) polymer composites with high piezoelectric response, 2) piezoelectric composites with increased operating temperatures, 3) motion control devices that incorporate piezoelectric materials and shape memory polymers, and 4) artificial muscles with piezoelectric polymers. The piezoelectric polymer composites developed in this work have potential to be utilized as highly efficient, flexible energy harvesters that can be used to capture ambient energy from environmental vibrations and motion from the human body. As actuators, these materials may find use as rapid-response muscle replacements in legs, arms, fingers, or toes. As sensors, such devices may provide electrical impulses capable of sensing small vibrations due to structural damage or movements. There is a wide range of applications for flexible piezoelectric materials that will continue to expand as technologies in monitoring, energy harvesting, and motion control continue to develop.

High Strain-Rate and Temperature Effects on the Response of Composites

NASA Technical Reports Server (NTRS)

Gilat, Amos

2004-01-01

The objective of the research is to expand the experimental study of the effect of strain rate on mechanical response (deformation and failure) of epoxy resins and carbon fibers/epoxy matrix composites, to include elevated temperature tests. The experimental data provide the information needed for NASA scientists for the development of a nonlinear, strain rate and temperature dependent deformation and strength models for composites that can subsequently be used in design. This year effort was directed into the development and testing of the epoxy resin at elevated temperatures. Two types of epoxy resins were tested in shear at high strain rates of about 700 per second and elevated temperatures of 50 and 80 C. The results show that the temperature significantly affects the response of epoxy.

Nonlinear Analysis and Scaling Laws for Noncircular Composite Structures Subjected to Combined Loads

NASA Technical Reports Server (NTRS)

Hilburger, Mark W.; Rose, Cheryl A.; Starnes, James H., Jr.

2001-01-01

Results from an analytical study of the response of a built-up, multi-cell noncircular composite structure subjected to combined internal pressure and mechanical loads are presented. Nondimensional parameters and scaling laws based on a first-order shear-deformation plate theory are derived for this noncircular composite structure. The scaling laws are used to design sub-scale structural models for predicting the structural response of a full-scale structure representative of a portion of a blended-wing-body transport aircraft. Because of the complexity of the full-scale structure, some of the similitude conditions are relaxed for the sub-scale structural models. Results from a systematic parametric study are used to determine the effects of relaxing selected similitude conditions on the sensitivity of the effectiveness of using the sub-scale structural model response characteristics for predicting the full-scale structure response characteristics.

Assembly of polythiophenes on responsive polymer microgels for the highly selective detection of ammonia gas

DOE PAGES

Chang, Aiping; Peng, Yahui; Li, Zezhou; ...

2016-04-05

For this study, a class of smart composite materials based on the assembly of conjugated polymers on responsive polymer microgels has been prepared. We have chosen poly(3-((2-(2-methoxyethoxy)ethoxy)methyl)-thiophene) as the model conjugated polymer and an ammonia-responsive microgel of phenoxazinium-functionalized poly(N-isopropylacrylamide-co-propargyl acrylate) as the model template. Under this design, the composite materials can combine the electrical conductivity of the conjugated polymers and the ammonia recognisability of the ammonia-responsive polymer microgels; the cooperation of these properties allows the reversible control of electrical conductivity by ammonia gas. Those composite materials can not only adapt to ammonia gas, but also convert changes in the concentrationmore » of ammonia into conductance, allowing the electrical detection of ammonia gas with high selectivity. This makes the composite materials different from the conductive polymer platforms reported previously, which may also respond to non-ammonia gases and the response induced by non-ammonia gases is close to that induced by ammonia gas. Using these composite materials as sensing materials for the electrical detection of ammonia gas, the detection limit can reach as low as 1.1 ppb. Finally, these features enable their use for the electrical detection of ammonia in breath.« less

Assembly of polythiophenes on responsive polymer microgels for the highly selective detection of ammonia gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Aiping; Peng, Yahui; Li, Zezhou

For this study, a class of smart composite materials based on the assembly of conjugated polymers on responsive polymer microgels has been prepared. We have chosen poly(3-((2-(2-methoxyethoxy)ethoxy)methyl)-thiophene) as the model conjugated polymer and an ammonia-responsive microgel of phenoxazinium-functionalized poly(N-isopropylacrylamide-co-propargyl acrylate) as the model template. Under this design, the composite materials can combine the electrical conductivity of the conjugated polymers and the ammonia recognisability of the ammonia-responsive polymer microgels; the cooperation of these properties allows the reversible control of electrical conductivity by ammonia gas. Those composite materials can not only adapt to ammonia gas, but also convert changes in the concentrationmore » of ammonia into conductance, allowing the electrical detection of ammonia gas with high selectivity. This makes the composite materials different from the conductive polymer platforms reported previously, which may also respond to non-ammonia gases and the response induced by non-ammonia gases is close to that induced by ammonia gas. Using these composite materials as sensing materials for the electrical detection of ammonia gas, the detection limit can reach as low as 1.1 ppb. Finally, these features enable their use for the electrical detection of ammonia in breath.« less

Degradation of ticarcillin by subcritial water oxidation method: Application of response surface methodology and artificial neural network modeling.

PubMed

Yabalak, Erdal

2018-05-18

This study was performed to investigate the mineralization of ticarcillin in the artificially prepared aqueous solution presenting ticarcillin contaminated waters, which constitute a serious problem for human health. 81.99% of total organic carbon removal, 79.65% of chemical oxygen demand removal, and 94.35% of ticarcillin removal were achieved by using eco-friendly, time-saving, powerful and easy-applying, subcritical water oxidation method in the presence of a safe-to-use oxidizing agent, hydrogen peroxide. Central composite design, which belongs to the response surface methodology, was applied to design the degradation experiments, to optimize the methods, to evaluate the effects of the system variables, namely, temperature, hydrogen peroxide concentration, and treatment time, on the responses. In addition, theoretical equations were proposed in each removal processes. ANOVA tests were utilized to evaluate the reliability of the performed models. F values of 245.79, 88.74, and 48.22 were found for total organic carbon removal, chemical oxygen demand removal, and ticarcillin removal, respectively. Moreover, artificial neural network modeling was applied to estimate the response in each case and its prediction and optimizing performance was statistically examined and compared to the performance of central composite design.

Associative Flow Rule Used to Include Hydrostatic Stress Effects in Analysis of Strain-Rate-Dependent Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.

2004-01-01

designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and the strain-rate dependence of the composite response are due primarily to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. By applying micromechanics techniques along with given fiber properties, one can also determine the effects of the hydrostatic stresses in the polymer on the overall composite deformation response. First efforts to account for the hydrostatic stress effects in the composite deformation applied purely empirical methods that relied on composite-level data. In later efforts, to allow polymer properties to be characterized solely on the basis of polymer data, researchers at the NASA Glenn Research Center developed equations to model the polymers that were based on a non-associative flow rule, and efforts to use these equations to simulate the deformation of representative polymer materials were reasonably successful. However, these equations were found to have difficulty in correctly analyzing the multiaxial stress states found in the polymer matrix constituent of a composite material. To correct these difficulties, and to allow for the accurate simulation of the nonlinear strain-rate-dependent deformation analysis of polymer matrix composites, in the efforts reported here Glenn researchers reformulated the polymer constitutive equations from basic principles using the concept of an associative flow rule. These revised equations were characterized and validated in an experimental program carried out through a university grant with the Ohio State University, wherein tensile and shear deformation data were obtained for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. Tensile deformation data also were obtained over a variety of strain rates and fiber orientation angles for a representative polymer matrix composite composed using the polymer.

Application of mathematical model methods for optimization tasks in construction materials technology

NASA Astrophysics Data System (ADS)

Fomina, E. V.; Kozhukhova, N. I.; Sverguzova, S. V.; Fomin, A. E.

2018-05-01

In this paper, the regression equations method for design of construction material was studied. Regression and polynomial equations representing the correlation between the studied parameters were proposed. The logic design and software interface of the regression equations method focused on parameter optimization to provide the energy saving effect at the stage of autoclave aerated concrete design considering the replacement of traditionally used quartz sand by coal mining by-product such as argillite. The mathematical model represented by a quadric polynomial for the design of experiment was obtained using calculated and experimental data. This allowed the estimation of relationship between the composition and final properties of the aerated concrete. The surface response graphically presented in a nomogram allowed the estimation of concrete properties in response to variation of composition within the x-space. The optimal range of argillite content was obtained leading to a reduction of raw materials demand, development of target plastic strength of aerated concrete as well as a reduction of curing time before autoclave treatment. Generally, this method allows the design of autoclave aerated concrete with required performance without additional resource and time costs.

Finite element modelling of crash response of composite aerospace sub-floor structures

NASA Astrophysics Data System (ADS)

McCarthy, M. A.; Harte, C. G.; Wiggenraad, J. F. M.; Michielsen, A. L. P. J.; Kohlgrüber, D.; Kamoulakos, A.

Composite energy-absorbing structures for use in aircraft are being studied within a European Commission research programme (CRASURV - Design for Crash Survivability). One of the aims of the project is to evaluate the current capabilities of crashworthiness simulation codes for composites modelling. This paper focuses on the computational analysis using explicit finite element analysis, of a number of quasi-static and dynamic tests carried out within the programme. It describes the design of the structures, the analysis techniques used, and the results of the analyses in comparison to the experimental test results. It has been found that current multi-ply shell models are capable of modelling the main energy-absorbing processes at work in such structures. However some deficiencies exist, particularly in modelling fabric composites. Developments within the finite element code are taking place as a result of this work which will enable better representation of composite fabrics.

Enhanced production of laccase from Coriolus versicolor NCIM 996 by nutrient optimization using response surface methodology.

PubMed

Arockiasamy, Santhiagu; Krishnan, Indira Packialakshmi Gurusamy; Anandakrishnan, Nimalanandan; Seenivasan, Sabitha; Sambath, Agalya; Venkatasubramani, Janani Priya

2008-12-01

Plackett and Burman design criterion and central composite design were applied successfully for enhanced production of laccase by Coriolus versicolor NCIM 996 for the first time. Plackett and Burman design criterion was applied to screen the significance of ten nutrients on laccase production by C. versicolor NCIM 996. Out of the ten nutrients tested, starch, yeast extract, MnSO(4), MgSO(4) x 7H(2)O, and phenol were found to have significant effect on laccase production. A central composite design was applied to determine the optimum concentrations of the significant variables obtained from Plackett-Burman design. The optimized medium composition for production of laccase was (g/l): starch, 30.0; yeast extract, 4.53; MnSO(4), 0.002; MgSO(4) x 7H(2)O, 0.755; and phenol, 0.026, and the optimum laccase production was 6,590.26 (U/l), which was 7.6 times greater than the control.

METCAN: The metal matrix composite analyzer

NASA Technical Reports Server (NTRS)

Hopkins, Dale A.; Murthy, Pappu L. N.

1988-01-01

Metal matrix composites (MMC) are the subject of intensive study and are receiving serious consideration for critical structural applications in advanced aerospace systems. MMC structural analysis and design methodologies are studied. Predicting the mechanical and thermal behavior and the structural response of components fabricated from MMC requires the use of a variety of mathematical models. These models relate stresses to applied forces, stress intensities at the tips of cracks to nominal stresses, buckling resistance to applied force, or vibration response to excitation forces. The extensive research in computational mechanics methods for predicting the nonlinear behavior of MMC are described. This research has culminated in the development of the METCAN (METal Matrix Composite ANalyzer) computer code.

Use of a New Portable Instrumented Impactor on the NASA Composite Crew Module Damage Tolerance Program

NASA Technical Reports Server (NTRS)

Jackson, Wade C.; Polis, Daniel L.

2014-01-01

Damage tolerance performance is critical to composite structures because surface impacts at relatively low energies may result in a significant strength loss. For certification, damage tolerance criteria require aerospace vehicles to meet design loads while containing damage at critical locations. Data from standard small coupon testing are difficult to apply to larger more complex structures. Due to the complexity of predicting both the impact damage and the residual properties, damage tolerance is demonstrated primarily by testing. A portable, spring-propelled, impact device was developed which allows the impact damage response to be investigated on large specimens, full-scale components, or entire vehicles. During impact, both the force history and projectile velocity are captured. The device was successfully used to demonstrate the damage tolerance performance of the NASA Composite Crew Module. The impactor was used to impact 18 different design features at impact energies up to 35 J. Detailed examples of these results are presented, showing impact force histories, damage inspection results, and response to loading.

Response Surface Methodology for the Optimization of Preparation of Biocomposites Based on Poly(lactic acid) and Durian Peel Cellulose

PubMed Central

Penjumras, Patpen; Abdul Rahman, Russly; Talib, Rosnita A.; Abdan, Khalina

2015-01-01

Response surface methodology was used to optimize preparation of biocomposites based on poly(lactic acid) and durian peel cellulose. The effects of cellulose loading, mixing temperature, and mixing time on tensile strength and impact strength were investigated. A central composite design was employed to determine the optimum preparation condition of the biocomposites to obtain the highest tensile strength and impact strength. A second-order polynomial model was developed for predicting the tensile strength and impact strength based on the composite design. It was found that composites were best fit by a quadratic regression model with high coefficient of determination (R 2) value. The selected optimum condition was 35 wt.% cellulose loading at 165°C and 15 min of mixing, leading to a desirability of 94.6%. Under the optimum condition, the tensile strength and impact strength of the biocomposites were 46.207 MPa and 2.931 kJ/m2, respectively. PMID:26167523

Nondestructive evaluation of composite materials - A design philosophy

NASA Technical Reports Server (NTRS)

Duke, J. C., Jr.; Henneke, E. G., II; Stinchcomb, W. W.; Reifsnider, K. L.

1984-01-01

Efficient and reliable structural design utilizing fiber reinforced composite materials may only be accomplished if the materials used may be nondestructively evaluated. There are two major reasons for this requirement: (1) composite materials are formed at the time the structure is fabricated and (2) at practical strain levels damage, changes in the condition of the material, that influence the structure's mechanical performance is present. The fundamental basis of such a nondestructive evaluation capability is presented. A discussion of means of assessing nondestructively the material condition as well as a damage mechanics theory that interprets the material condition in terms of its influence on the mechanical response, stiffness, strength and life is provided.

Progressive Failure Analysis of Composite Stiffened Panels

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Yarrington, Phillip W.; Collier, Craig S.; Arnold, Steven M.

2006-01-01

A new progressive failure analysis capability for stiffened composite panels has been developed based on the combination of the HyperSizer stiffened panel design/analysis/optimization software with the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC). MAC/GMC discretizes a composite material s microstructure into a number of subvolumes and solves for the stress and strain state in each while providing the homogenized composite properties as well. As a result, local failure criteria may be employed to predict local subvolume failure and the effects of these local failures on the overall composite response. When combined with HyperSizer, MAC/GMC is employed to represent the ply level composite material response within the laminates that constitute a stiffened panel. The effects of local subvolume failures can then be tracked as loading on the stiffened panel progresses. Sample progressive failure results are presented at both the composite laminate and the composite stiffened panel levels. Deformation and failure model predictions are compared with experimental data from the World Wide Failure Exercise for AS4/3501-6 graphite/epoxy laminates.

A Study of Flexible Composites for Expandable Space Structures

NASA Technical Reports Server (NTRS)

Scotti, Stephen J.

2016-01-01

Payload volume for launch vehicles is a critical constraint that impacts spacecraft design. Deployment mechanisms, such as those used for solar arrays and antennas, are approaches that have successfully accommodated this constraint, however, providing pressurized volumes that can be packaged compactly at launch and expanded in space is still a challenge. One approach that has been under development for many years is to utilize softgoods - woven fabric for straps, cloth, and with appropriate coatings, bladders - to provide this expandable pressure vessel capability. The mechanics of woven structure is complicated by a response that is nonlinear and often nonrepeatable due to the discrete nature of the woven fiber architecture. This complexity reduces engineering confidence to reliably design and certify these structures, which increases costs due to increased requirements for system testing. The present study explores flexible composite materials systems as an alternative to the heritage softgoods approach. Materials were obtained from vendors who utilize flexible composites for non-aerospace products to determine some initial physical and mechanical properties of the materials. Uniaxial mechanical testing was performed to obtain the stress-strain response of the flexible composites and the failure behavior. A failure criterion was developed from the data, and a space habitat application was used to provide an estimate of the relative performance of flexible composites compared to the heritage softgoods approach. Initial results are promising with a 25% mass savings estimated for the flexible composite solution.

Optical sensor platform based on cellulose nanocrystals (CNC) - 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC) bi-phase nematic liquid crystal composite films.

PubMed

Santos, Moliria V; Tercjak, Agnieszka; Gutierrez, Junkal; Barud, Hernane S; Napoli, Mariana; Nalin, Marcelo; Ribeiro, Sidney J L

2017-07-15

The preparation of composite materials has gained tremendous attention due to the potential synergy of the combined materials. Here we fabricate novel thermal/electrical responsive photonic composite films combining cellulose nanocrystals (CNC) with a low molecular weight nematic liquid crystal (NLC), 4'-(hexyloxy)-4-biphenylcarbonitrile (HOBC). The obtained composite material combines both intense structural coloration of photonic cellulose and thermal and conductive properties of NLC. Scanning electron microscopy (SEM) results confirmed that liquid crystals coated CNC films maintain chiral nematic structure characteristic of CNC film and simultaneously, transversal cross-section scanning electron microscopy images indicated penetration of liquid crystals through the CNC layers. Investigated composite film maintain NLC optical properties being switchable as a function of temperature during heating/cooling cycles. The relationship between the morphology and thermoresponsive in the micro/nanostructured materials was investigated by using transmission optical microscopy (TOM). Conductive response of the composite films was proved by Electrostatic force microscopy (EFM) measurement. Designed thermo- and electro-responsive materials open novel simple pathway of fabrication of CNC-based materials with tunable properties. Copyright © 2017. Published by Elsevier Ltd.

Experimental Study of the Compression Response of Fluted-Core Composite Panels with Joints

NASA Technical Reports Server (NTRS)

Schultz, Marc R.; Rose, Cheryl A.; Guzman, J. Carlos; McCarville, Douglas; Hilburger, Mark W.

2012-01-01

Fluted-core sandwich composites consist of integral angled web members spaced between laminate face sheets, and may have the potential to provide benefits over traditional sandwich composites for certain aerospace applications. However, fabrication of large autoclave-cured fluted-core cylindrical shells with existing autoclaves will require that the shells be fabricated in segments, and joined longitudinally to form a complete barrel. Two different longitudinal fluted-core joint designs were considered experimentally in this study. In particular, jointed fluted-core-composite panels were tested in longitudinal compression because longitudinal compression is the primary loading condition in dry launch-vehicle barrel sections. One of the joint designs performed well in comparison with unjointed test articles, and the other joint design failed at loads approximately 14% lower than unjointed test articles. The compression-after-impact (CAI) performance of jointed fluted-core composites was also investigated by testing test articles that had been subjected to 6 ft-lb impacts. It was found that such impacts reduced the load-carrying capability by 9% to 40%. This reduction is dependent on the joint concept, component flute size, and facesheet thickness.

Fabrication and Properties of Composite Artificial Muscles Based on Nylon and a Shape Memory Alloy

NASA Astrophysics Data System (ADS)

Yin, Haibin; Zhou, Jia; Li, Junfeng; Joseph, Vincent S.

2018-05-01

This paper focuses on the design, fabrication and investigation of the mechanical properties of new artificial muscles formed by twisting and annealing. The artificial muscles designed by twisting nylon have become a popular topic in the field of smart materials due to their high mechanical performance with a large deformation and power density. However, the complexity of the heating and cooling system required to control the nylon muscle is a disadvantage, so we have proposed a composite artificial muscle for providing a direct electricity-driven actuation by integrating nylon and a shape memory alloy (SMA). In this paper, the design and fabrication process of these composite artificial muscles are introduced before their mechanical properties, which include the deformation, stiffness, load and response, are investigated. The results show that these composite artificial muscles that integrate nylon and a SMA provide better mechanical properties and yield up to a 44.1% deformation and 3.43 N driving forces. The good performance and direct electro-thermal actuation make these composite muscles ideal for driving robots in a method similar to human muscles.

Two-range magnetoelectric sensor

NASA Astrophysics Data System (ADS)

Bichurin, M.; Petrov, V.; Leontyev, V.; Saplev, A.

2017-01-01

In this study, we present a two-range magnetoelectric ME sensor design comprising of permendur (alloy of Fe-Co-V), nickel, and lead zirconate titanate (PZT) laminate composite. A systematic study was conducted to clarify the contribution of magnetostrictive layers variables to the ME response over the applied range of magnetic bias field. The two-range behavior was characterized by opposite sign of the ME response when magnetic dc bias is in different sub-ranges. The ME coefficient as a function of magnetic bias field was found to be dependent on the laminate composite structure.

Analogy for the effect of material and geometrical variables on energy-absorption capability of composite tubes

NASA Technical Reports Server (NTRS)

Farley, Gary L.; Jones, Robert M.

1992-01-01

Simplified procedures for determining the qualitative effect a variable has on structural response of a composite tube are very useful in both preliminary design as well as in providing insight into the general response. An analysis procedure is presented that can be used to determine the qualitative change in the sustained crushing load due to a change in specimen material properties or geometry. The analysis procedure is similar in form to the equation for the buckling load of a column on an elastic foundation.

Underwater characterizations of monolithic piezoceramic and 1-3 composite using a self-designed transducer

NASA Astrophysics Data System (ADS)

Saleem Mirza, Muhammad; Yasin, Tariq; Ikram, Masroor; Altaf, Muhammad; Mushtaq, Zahir; Nasir Khan, Muhammad

2016-03-01

Underwater characterizations of (Pb0.94Sr0.04)(Zr0.52Ti0.48)O3 (PZT) and PZT/araldite-F 1-3 composite were carried out through a self-designed transducer. Disc-shaped samples of bulk PZT and PZT/araldite-F composite were first characterized in air and then were assembled in the transducer individually. The transducer's underwater voltage receiving sensitivity (Sh) and transmitting voltage response (Sv) were investigated in the frequency range of 10-200 kHz (well below thickness mode resonance) using a calibrated projector and receiver method with pulse technique. Results revealed that the transducer made with composite sample exhibited better (Sh) values (-214 dB ref 1 V/µPa) due to ~295% higher piezoelectric voltage coefficient gh (30 × 10-3 Vm/N) of the composite compared to PZT. In addition, the transducer with the PZT sample showed better Sv values (80 dB ref 1 µPa/1 V at 1 m) due to the presence of planar mode peaks in the frequency range of 10-200 kHz. These results indicate that the monolithic piezoceramic can exhibit underwater Sv response in both planar and thickness resonance modes owing to the admittance peaks in these frequency regions.

Design of pH-responsive nanoparticles of terpolymer of poly(methacrylic acid), polysorbate 80 and starch for delivery of doxorubicin.

PubMed

Shalviri, Alireza; Chan, Ho Ka; Raval, Gaurav; Abdekhodaie, Mohammad J; Liu, Qiang; Heerklotz, Heiko; Wu, Xiao Yu

2013-01-01

This work focused on the design of new pH-responsive nanoparticles for controlled delivery of anticancer drug doxorubicin (Dox). Nanoparticles of poly(methacrylic acid)-polysorbate 80-grafted starch (PMAA-PS 80-g-St) were synthesized by using a one-pot method that enabled simultaneous grafting of PMAA and PS 80 onto starch and nanoparticle formation in an aqueous medium. The particles were characterized by FTIR, (1)H NMR, TEM, DLS, and potentiometric titration. Dox loading and in vitro release from the nanoparticles were investigated. The FTIR and (1)H NMR confirmed the chemical composition of the graft terpolymer. The nanoparticles were relatively spherical with narrow size distribution and porous morphology. They exhibited pH-dependent swelling in a physiological pH range. The particle size and magnitude of phase transition were dependent on polymer composition and formulation parameters such as concentrations of surfactant and cross-linking agent and total monomer concentration. The nanoparticles with optimized compositions showed high loading capacity for Dox and sustained Dox release. The results suggest that the new pH-responsive terpolymer nanoparticles are useful in controlled drug delivery. Copyright © 2012 Elsevier B.V. All rights reserved.

The polarization response in InAs quantum dots: theoretical correlation between composition and electronic properties.

PubMed

Usman, Muhammad; Tasco, Vittorianna; Todaro, Maria Teresa; De Giorgi, Milena; O'Reilly, Eoin P; Klimeck, Gerhard; Passaseo, Adriana

2012-04-27

III-V growth and surface conditions strongly influence the physical structure and resulting optical properties of self-assembled quantum dots (QDs). Beyond the design of a desired active optical wavelength, the polarization response of QDs is of particular interest for optical communications and quantum information science. Previous theoretical studies based on a pure InAs QD model failed to reproduce experimentally observed polarization properties. In this work, multi-million atom simulations are performed in an effort to understand the correlation between chemical composition and polarization properties of QDs. A systematic analysis of QD structural parameters leads us to propose a two-layer composition model, mimicking In segregation and In-Ga intermixing effects. This model, consistent with mostly accepted compositional findings, allows us to accurately fit the experimental PL spectra. The detailed study of QD morphology parameters presented here serves as a tool for using growth dynamics to engineer the strain field inside and around the QD structures, allowing tuning of the polarization response.

Optimization of critical medium components using response surface methodology for phenazine-1-carboxylic acid production by Pseudomonas sp. M-18Q.

PubMed

Yuan, Li-Li; Li, Ya-Qian; Wang, Yi; Zhang, Xue-Hong; Xu, Yu-Quan

2008-03-01

The optimal flask-shaking batch fermentation medium for phenazine-1-carboxylic acid (PCA) production by Pseudomonas sp. M-18Q, a qscR chromosomal inactivated mutant of the strain M18 was studied using statistical experimental design and analysis. The Plackett-Burman design (PBD) was used to evaluate the effects of eight medium components on the production of PCA, which showed that glucose and soytone were the most significant ingredients (P<0.05). The steepest ascent experiment was adopted to determine the optimal region of the medium composition. The optimum composition of the fermentation medium for maximum PCA yield, as determined on the basis of a five-level two-factor central composite design (CCD), was obtained by response surface methodology (RSM). The high correlation between the predicted and observed values indicated the validity of the model. A maximum PCA yield of 1240 mg/l was obtained at 17.81 g/l glucose and 11.47 g/l soytone, and the production was increased by 65.3% compared with that using the original medium, which was at 750 mg/l.

Teaching the placement of posterior resin-based composite restorations in Spanish dental schools

PubMed Central

Lynch, Christopher; McConnell, Robert; Wilson, Nairn

2012-01-01

Objectives: In an area of esthetic dentistry such as posterior composites, in which new materials and techniques are being devolved continuously, it is important to confirm that dental students have a clear understanding of the basic principles of clinical application of this knowledge. Considering that the preparation of dental graduates in Spain may be of interest to competent dental authorities and employers with whom they can work worldwide, this study investigated the teaching of posterior composite restorations in Spanish dental schools. Study design: In late 2009⁄ early 2010, a questionnaire seeking information on the teaching of posterior composites was emailed to the professor responsible for teaching operative dentistry in each of the fifteen dental schools having complete undergraduate dental degree programs in Spain. Results: The response rate was 100%. Most investigated topics did not show noteworthy differences depending on whether the schools were public or private. Variations were found among Spanish dental schools in both the amount and content of the teaching programs concerning posterior composite restorations. Differences were recorded in the teaching of cavity design, contraindications to composite placement, indications for liners and bases, matrix and wedging techniques, composite and bonding systems, light curing and finishing procedures for composite restorations. More consistency was observed in teaching methods of moisture-control, indirect composites and amalgam bonding. Conclusions: As recommended in previously surveyed countries, efforts must be made to promote harmonization of dental curricula to make it easier for graduates to work elsewhere, and to ensure they meet the needs of their patients on entering independent practice. Key words:Aesthetic dentistry, composite restoration, dental education, teaching program, undergraduate dental student. PMID:22322491

Simulating the Response of a Composite Honeycomb Energy Absorber. Part 1; Dynamic Crushing of Components and Multi-Terrain Impacts

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Polanco, Michael A.

2012-01-01

This paper describes the experimental and analytical evaluation of an externally deployable composite honeycomb structure that is designed to attenuate impact energy during helicopter crashes. The concept, designated the Deployable Energy Absorber (DEA), utilizes an expandable Kevlar (Registered Trademark) honeycomb to dissipate kinetic energy through crushing. The DEA incorporates a unique flexible hinge design that allows the honeycomb to be packaged and stowed until needed for deployment. Experimental evaluation of the DEA included dynamic crush tests of multi-cell components and vertical drop tests of a composite fuselage section, retrofitted with DEA blocks, onto multi-terrain. Finite element models of the test articles were developed and simulations were performed using the transient dynamic code, LSDYNA (Registered Trademark). In each simulation, the DEA was represented using shell elements assigned two different material properties: Mat 24, an isotropic piecewise linear plasticity model, and Mat 58, a continuum damage mechanics model used to represent laminated composite fabrics. DEA model development and test-analysis comparisons are presented.

Two-level optimization of composite wing structures based on panel genetic optimization

NASA Astrophysics Data System (ADS)

Liu, Boyang

The design of complex composite structures used in aerospace or automotive vehicles presents a major challenge in terms of computational cost. Discrete choices for ply thicknesses and ply angles leads to a combinatorial optimization problem that is too expensive to solve with presently available computational resources. We developed the following methodology for handling this problem for wing structural design: we used a two-level optimization approach with response-surface approximations to optimize panel failure loads for the upper-level wing optimization. We tailored efficient permutation genetic algorithms to the panel stacking sequence design on the lower level. We also developed approach for improving continuity of ply stacking sequences among adjacent panels. The decomposition approach led to a lower-level optimization of stacking sequence with a given number of plies in each orientation. An efficient permutation genetic algorithm (GA) was developed for handling this problem. We demonstrated through examples that the permutation GAs are more efficient for stacking sequence optimization than a standard GA. Repair strategies for standard GA and the permutation GAs for dealing with constraints were also developed. The repair strategies can significantly reduce computation costs for both standard GA and permutation GA. A two-level optimization procedure for composite wing design subject to strength and buckling constraints is presented. At wing-level design, continuous optimization of ply thicknesses with orientations of 0°, 90°, and +/-45° is performed to minimize weight. At the panel level, the number of plies of each orientation (rounded to integers) and inplane loads are specified, and a permutation genetic algorithm is used to optimize the stacking sequence. The process begins with many panel genetic optimizations for a range of loads and numbers of plies of each orientation. Next, a cubic polynomial response surface is fitted to the optimum buckling load. The resulting response surface is used for wing-level optimization. In general, complex composite structures consist of several laminates. A common problem in the design of such structures is that some plies in the adjacent laminates terminate in the boundary between the laminates. These discontinuities may cause stress concentrations and may increase manufacturing difficulty and cost. We developed measures of continuity of two adjacent laminates. We studied tradeoffs between weight and continuity through a simple composite wing design. Finally, we compared the two-level optimization to a single-level optimization based on flexural lamination parameters. The single-level optimization is efficient and feasible for a wing consisting of unstiffened panels.

Dynamic Loading and Characterization of Fiber-Reinforced Composites

NASA Astrophysics Data System (ADS)

Sierakowski, Robert L.; Chaturvedi, Shive K.

1997-02-01

Emphasizing polymer based fiber-reinforced composites, this book is designed to provide readers with a significant understanding of the complexities involved in characterizing dynamic events and the corresponding response of advanced fiber composite materials and structures. These elements include dynamic loading devices, material properties characterization, analytical and experimental techniques to assess the damage and failure modes associated with various dynamic loading events. Concluding remarks are presented throughout the text which summarize key points and raise issues related to important research needed.

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

NASA Astrophysics Data System (ADS)

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng; Worsley, Marcus A.; Wu, Amanda S.; Kanarska, Yuliya; Horn, John D.; Duoss, Eric B.; Ortega, Jason M.; Elmer, William; Hensleigh, Ryan; Fellini, Ryan A.; King, Michael J.

2017-03-01

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignmentmore » within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Moreover, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.« less

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

DOE PAGES

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng; ...

2017-03-06

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignmentmore » within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Moreover, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.« less

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties.

PubMed

Lewicki, James P; Rodriguez, Jennifer N; Zhu, Cheng; Worsley, Marcus A; Wu, Amanda S; Kanarska, Yuliya; Horn, John D; Duoss, Eric B; Ortega, Jason M; Elmer, William; Hensleigh, Ryan; Fellini, Ryan A; King, Michael J

2017-03-06

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response.

3D-Printing of Meso-structurally Ordered Carbon Fiber/Polymer Composites with Unprecedented Orthotropic Physical Properties

PubMed Central

Lewicki, James P.; Rodriguez, Jennifer N.; Zhu, Cheng; Worsley, Marcus A.; Wu, Amanda S.; Kanarska, Yuliya; Horn, John D.; Duoss, Eric B.; Ortega, Jason M.; Elmer, William; Hensleigh, Ryan; Fellini, Ryan A.; King, Michael J.

2017-01-01

Here we report the first example of a class of additively manufactured carbon fiber reinforced composite (AMCFRC) materials which have been achieved through the use of a latent thermal cured aromatic thermoset resin system, through an adaptation of direct ink writing (DIW) 3D-printing technology. We have developed a means of printing high performance thermoset carbon fiber composites, which allow the fiber component of a resin and carbon fiber fluid to be aligned in three dimensions via controlled micro-extrusion and subsequently cured into complex geometries. Characterization of our composite systems clearly show that we achieved a high order of fiber alignment within the composite microstructure, which in turn allows these materials to outperform equivalently filled randomly oriented carbon fiber and polymer composites. Furthermore, our AM carbon fiber composite systems exhibit highly orthotropic mechanical and electrical responses as a direct result of the alignment of carbon fiber bundles in the microscale which we predict will ultimately lead to the design of truly tailorable carbon fiber/polymer hybrid materials having locally programmable complex electrical, thermal and mechanical response. PMID:28262669

Optimization of a GO2/GH2 Impinging Injector Element

NASA Technical Reports Server (NTRS)

Tucker, P. Kevin; Shyy, Wei; Vaidyanathan, Rajkumar

2001-01-01

An injector optimization methodology, method i, is used to investigate optimal design points for a gaseous oxygen/gaseous hydrogen (GO2/GH2) impinging injector element. The unlike impinging element, a fuel-oxidizer- fuel (F-O-F) triplet, is optimized in terms of design variables such as fuel pressure drop, (Delta)P(sub f), oxidizer pressure drop, (Delta)P(sub o), combustor length, L(sub comb), and impingement half-angle, alpha, for a given mixture ratio and chamber pressure. Dependent variables such as energy release efficiency, ERE, wall heat flux, Q(sub w), injector heat flux, Q(sub inj), relative combustor weight, W(sub rel), and relative injector cost, C(sub rel), are calculated and then correlated with the design variables. An empirical design methodology is used to generate these responses for 163 combinations of input variables. Method i is then used to generate response surfaces for each dependent variable. Desirability functions based on dependent variable constraints are created and used to facilitate development of composite response surfaces representing some, or all, of the five dependent variables in terms of the input variables. Three examples illustrating the utility and flexibility of method i are discussed in detail. First, joint response surfaces are constructed by sequentially adding dependent variables. Optimum designs are identified after addition of each variable and the effect each variable has on the design is shown. This stepwise demonstration also highlights the importance of including variables such as weight and cost early in the design process. Secondly, using the composite response surface which includes all five dependent variables, unequal weights are assigned to emphasize certain variables relative to others. Here, method i is used to enable objective trade studies on design issues such as component life and thrust to weight ratio. Finally, specific variable weights are further increased to illustrate the high marginal cost of realizing the last increment of injector performance and thruster weight.

Tunable poly(methacrylic acid-co-acrylamide) nanoparticles through inverse emulsion polymerization.

PubMed

Zhong, Justin X; Clegg, John R; Ander, Eric W; Peppas, Nicholas A

2018-06-01

Environmentally responsive biomaterials have played key roles in the design of biosensors and drug delivery vehicles. Their physical response to external stimuli, such as temperature or pH, can transduce a signal or trigger the release of a drug. In this work, we designed a robust, highly tunable, pH-responsive nanoscale hydrogel system. We present the design and characterization of poly(methacrylic acid-co-acrylamide) hydrogel nanoparticles, crosslinked with methylenebisacrylamide, through inverse emulsion polymerization. The effects of polymerization parameters (i.e., identities and concentrations of monomer and surfactant) and polymer composition (i.e., weight fraction of ionic and crosslinking monomers) on the nanoparticles' bulk and environmentally responsive properties were determined. We generated uniform, spherical nanoparticles which, through modulation of crosslinking, exhibit a volume swelling of 1.77-4.07, relative to the collapsed state in an acidic environment. We believe our system has potential as a base platform for the targeted, injectable delivery of hydrophilic therapeutics. With equal importance, however, we hope that our systematic analysis of the individual impacts of polymerization and purification conditions on nanoparticle composition, morphology, and performance can be used to expedite the development of alternate hydrophilic nanomaterials for a range of biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1677-1686, 2018. © 2018 Wiley Periodicals, Inc.

Optimization of Polygalacturonase Production from a Newly Isolated Thalassospira frigidphilosprofundus to Use in Pectin Hydrolysis: Statistical Approach

PubMed Central

Rekha, V. P. B.; Ghosh, Mrinmoy; Adapa, Vijayanand; Oh, Sung-Jong; Pulicherla, K. K.; Sambasiva Rao, K. R. S.

2013-01-01

The present study deals with the production of cold active polygalacturonase (PGase) by submerged fermentation using Thalassospira frigidphilosprofundus, a novel species isolated from deep waters of Bay of Bengal. Nonlinear models were applied to optimize the medium components for enhanced production of PGase. Taguchi orthogonal array design was adopted to evaluate the factors influencing the yield of PGase, followed by the central composite design (CCD) of response surface methodology (RSM) to identify the optimum concentrations of the key factors responsible for PGase production. Data obtained from the above mentioned statistical experimental design was used for final optimization study by linking the artificial neural network and genetic algorithm (ANN-GA). Using ANN-GA hybrid model, the maximum PGase activity (32.54 U/mL) was achieved at the optimized concentrations of medium components. In a comparison between the optimal output of RSM and ANN-GA hybrid, the latter favored the production of PGase. In addition, the study also focused on the determination of factors responsible for pectin hydrolysis by crude pectinase extracted from T. frigidphilosprofundus through the central composite design. Results indicated 80% degradation of pectin in banana fiber at 20°C in 120 min, suggesting the scope of cold active PGase usage in the treatment of raw banana fibers. PMID:24455722

Optimization of polygalacturonase production from a newly isolated Thalassospira frigidphilosprofundus to use in pectin hydrolysis: statistical approach.

PubMed

Rekha, V P B; Ghosh, Mrinmoy; Adapa, Vijayanand; Oh, Sung-Jong; Pulicherla, K K; Sambasiva Rao, K R S

2013-01-01

The present study deals with the production of cold active polygalacturonase (PGase) by submerged fermentation using Thalassospira frigidphilosprofundus, a novel species isolated from deep waters of Bay of Bengal. Nonlinear models were applied to optimize the medium components for enhanced production of PGase. Taguchi orthogonal array design was adopted to evaluate the factors influencing the yield of PGase, followed by the central composite design (CCD) of response surface methodology (RSM) to identify the optimum concentrations of the key factors responsible for PGase production. Data obtained from the above mentioned statistical experimental design was used for final optimization study by linking the artificial neural network and genetic algorithm (ANN-GA). Using ANN-GA hybrid model, the maximum PGase activity (32.54 U/mL) was achieved at the optimized concentrations of medium components. In a comparison between the optimal output of RSM and ANN-GA hybrid, the latter favored the production of PGase. In addition, the study also focused on the determination of factors responsible for pectin hydrolysis by crude pectinase extracted from T. frigidphilosprofundus through the central composite design. Results indicated 80% degradation of pectin in banana fiber at 20 °C in 120 min, suggesting the scope of cold active PGase usage in the treatment of raw banana fibers.

Multi-Functional Composite Fatigue

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.

2008-01-01

Damage and fracture of composites subjected to monotonically increasing static, tension-tension cyclic, pressurization, and flexural cyclic loading are evaluated via a recently developed composite mechanics code that allows the user to focus on composite response at infinitely small scales. Constituent material properties, stress and strain limits are scaled up to the laminate level to evaluate the overall damage and durability. Results show the number of cycles to failure at different temperatures. A procedure is outlined for use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of results with insight for design decisions.

Thermomechanical Response of Shape Memory Alloy Hybrid Composites. Degree awarded by Virginia Polytechnic Inst. and State Univ., Blackburg, Virginia, Nov. 2000.

NASA Technical Reports Server (NTRS)

Turner, Travis L.

2001-01-01

This study examines the use of embedded shape memory alloy (SMA) actuators for adaptive control of the thermomechanical response of composite structures. A nonlinear thermomechanical model is presented for analyzing shape memory alloy hybrid composite (SMAHC) structures exposed to steady-state thermal and dynamic mechanical loads. Also presented are (1) fabrication procedures for SMAHC specimens, (2) characterization of the constituent materials for model quantification, (3) development of the test apparatus for conducting static and dynamic experiments on specimens with and without SMA, (4) discussion of the experimental results, and (5) validation of the analytical and numerical tools developed in the study. Excellent agreement is achieved between the predicted and measured SAMHC responses including thermal buckling, thermal post-buckling and dynamic response due to inertial loading. The validated model and thermomechanical analysis tools are used to demonstrate a variety of static and dynamic response behaviors including control of static (thermal buckling and post-buckling) and dynamic responses (vibration, sonic fatigue, and acoustic transmission). and SMAHC design considerations for these applications. SMAHCs are shown to have significant advantages over conventional response abatement approaches for vibration, sonic fatigue, and noise control.

Stiffness Characteristics of Composite Rotor Blades With Elastic Couplings

NASA Technical Reports Server (NTRS)

Piatak, David J.; Nixon, Mark W.; Kosmatka, John B.

1997-01-01

Recent studies on rotor aeroelastic response and stability have shown the beneficial effects of incorporating elastic couplings in composite rotor blades. However, none of these studies have clearly identified elastic coupling limits and the effects of elastic couplings on classical beam stiffnesses of representative rotor blades. Knowledge of these limits and effects would greatly enhance future aeroelastic studies involving composite rotor blades. The present study addresses these voids and provides a preliminary design database for investigators who may wish to study the effects of elastic couplings on representative blade designs. The results of the present study should provide a basis for estimating the potential benefits associated with incorporating elastic couplings without the need for first designing a blade cross section and then performing a cross-section analysis to obtain the required beam section properties as is customary in the usual one-dimensional beam-type approach.

Design, analysis, and testing of a metal matrix composite web/flange intersection

NASA Technical Reports Server (NTRS)

Biggers, S. B.; Knight, N. F., Jr.; Moran, S. G.; Olliffe, R.

1992-01-01

An experimental and analytical program to study the local design details of a typical T-shaped web/flange intersection made from a metal matrix composite is described. Loads creating flange bending were applied to specimens having different designs and boundary conditions. Finite element analyses were conducted on models of the test specimens to predict the structural response. The analyses correctly predict failure load, mode, and location in the fillet material in the intersection region of the web and the flange when specimen quality is good. The test program shows the importance of fabrication quality in the intersection region. The full-scale test program that led to the investigation of this local detail is also described.

Mechanics of composite materials: Recent advances; Proceedings of the Symposium, Virginia Polytechnic Institute and State University, Blacksburg, VA, August 16-19, 1982

NASA Technical Reports Server (NTRS)

Hashin, Z. (Editor); Herakovich, C. T. (Editor)

1983-01-01

The present conference on the mechanics of composites discusses microstructure's influence on particulate and short fiber composites' thermoelastic and transport properties, the elastoplastic deformation of composites, constitutive equations for viscoplastic composites, the plasticity and fatigue of metal matrix composites, laminate damping mechanisms, the micromechanical modeling of Kevlar/epoxy composites' time-dependent failure, the variational characterization of waves in composites, and computational methods for eigenvalue problems in composite design. Also discussed are the elastic response of laminates, elastic coupling nonlinear effects in unsymmetrical laminates, elasticity solutions for laminate problems having stress singularities, the mechanics of bimodular composite structures, the optimization of laminated plates and shells, NDE for laminates, the role of matrix cracking in the continuum constitutive behavior of a damaged composite ply, and the energy release rates of various microcracks in short fiber composites.

An experimental and analytical investigation on the response of GR/EP composite I-frames

NASA Technical Reports Server (NTRS)

Moas, E., Jr.; Boitnott, R. L.; Griffin, O. H., Jr.

1991-01-01

Six-foot diameter, semicircular graphite/epoxy specimens representative of generic aircraft frames were loaded quasi-statically to determine their load response and failure mechanisms for large deflections that occur in an airplane crash. These frame-skin specimens consisted of a cylindrical skin section cocured with a semicircular I-frame. Various frame laminate stacking sequences and geometries were evaluated by statically loading the specimen until multiple failures occurred. Two analytical methods were compared for modeling the frame-skin specimens: a two-dimensional branched-shell finite element analysis and a one-dimensional, closed-form, curved beam solution derived using an energy method. Excellent correlation was obtained between experimental results and the finite element predictions of the linear response of the frames prior to the initial failure. The beam solution was used for rapid parameter and design studies, and was found to be stiff in comparison with the finite element analysis. The specimens were found to be useful for evaluating composite frame designs.

Evaluation of the effect of temperature, NaOH concentration and time on solubilization of palm oil mill effluent (POME) using response surface methodology (RSM).

PubMed

Chou, K W; Norli, I; Anees, A

2010-11-01

In this study, palm oil mill effluent (POME) was solubilized by batch thermo-alkaline pre-treatments. A three-factor central composite design (CCD) was applied to identify the optimum COD solubilization condition. The individual and interactive effects of three factors, temperature, NaOH concentration and reaction time, on solubilization of POME were evaluated by employing response surface methodology (RSM). The experimental results showed that temperature, NaOH concentration and reaction time all had an individual significant effect on the solubilization of POME. But these three factors were independent, or there was insignificant interaction on the response. The maximum COD solubilization of 82.63% was estimated under the optimum condition at 32.5 degrees C, 8.83g/L of NaOH and 41.23h reaction time. The confirmation experiment of the predicted optimum conditions verified that the RSM with the central composite design was useful for optimizing the solubilization of POME.

Impact damage resistance of composite fuselage structure, part 1

NASA Technical Reports Server (NTRS)

Dost, E. F.; Avery, W. B.; Ilcewicz, L. B.; Grande, D. H.; Coxon, B. R.

1992-01-01

The impact damage resistance of laminated composite transport aircraft fuselage structures was studied experimentally. A statistically based designed experiment was used to examine numerous material, laminate, structural, and extrinsic (e.g., impactor type) variables. The relative importance and quantitative measure of the effect of each variable and variable interactions on responses including impactor dynamic response, visibility, and internal damage state were determined. The study utilized 32 three-stiffener panels, each with a unique combination of material type, material forms, and structural geometry. Two manufacturing techniques, tow placement and tape lamination, were used to build panels representative of potential fuselage crown, keel, and lower side-panel designs. Various combinations of impactor variables representing various foreign-object-impact threats to the aircraft were examined. Impacts performed at different structural locations within each panel (e.g., skin midbay, stiffener attaching flange, etc.) were considered separate parallel experiments. The relationship between input variables, measured damage states, and structural response to this damage are presented including recommendations for materials and impact test methods for fuselage structure.

A Study of Time-dependent and Anisotropic Effects on the Deformation Response of Two Flywheel Designs

NASA Technical Reports Server (NTRS)

Saleeb, Atef F.; Arnold, Steven M.; Al-Zoubi, Nasser R.

2003-01-01

The influence of material time dependency and anisotropy in the context of two specific flywheel designs-preload and multi-directional composite (MDC)--is investigated. In particular, we focus on the following aspects: 1) geometric constraints, 2) material constraints, 3) loading type, and 4) the fundamental character of the time-dependent response, i.e., reversible or irreversible. The bulk of the results presented were obtained using a composite (PMC IM7/8552 at 135 C) material system. The material was characterized using a general multimechanism hereditary (viscoelastoplastic) model. As a general conclusion, the results have clearly shown that both the preload and the MDC rotor designs are significantly affected by time-dependent material behavior, which may impact the state of rotor balance and potentially reduce its operating life. In view of the results of the parametric studies and predictions made in the present study, the need for actual experimentation focusing on the time-dependent behavior of full-scale flywheel rotors is self-evident.

Corrosion Protection Properties of PPy-ND Composite Coating: Sonoelectrochemical Synthesis and Design of Experiment

NASA Astrophysics Data System (ADS)

Ashassi-Sorkhabi, H.; Bagheri, R.; Rezaei-Moghadam, B.

2016-02-01

In this research, the nanocomposite coatings comprising the polypyrrole-nanodiamond, PPy-ND, on St-12 steel electrodes were electro-synthesized using in situ polymerization process under ultrasonic irradiation. The corrosion protection performance and morphology characterization of prepared coatings were investigated by electrochemical methods and scanning electron microscopy, SEM, respectively. Also, the experimental design was employed to determine the best values considering the effective parameters such as the concentration of nanoparticles, the applied current density and synthesis time to achieve the most protective films. A response surface methodology, RSM, involving a central composite design, CCD, was applied to the modeling and optimization of the PPy-ND nanocomposite deposition. Pareto graphic analysis of the parameters indicated that the applied current density and some of the interactions were effective on the response. The electrochemical results proved that the embedment of diamond nanoparticle, DNP, improves the corrosion resistance of PPy coatings significantly. Therefore, desirable correlation exists between predicted data and experimental results.

Mixing modes in a population-based interview survey: comparison of a sequential and a concurrent mixed-mode design for public health research.

PubMed

Mauz, Elvira; von der Lippe, Elena; Allen, Jennifer; Schilling, Ralph; Müters, Stephan; Hoebel, Jens; Schmich, Patrick; Wetzstein, Matthias; Kamtsiuris, Panagiotis; Lange, Cornelia

2018-01-01

Population-based surveys currently face the problem of decreasing response rates. Mixed-mode designs are now being implemented more often to account for this, to improve sample composition and to reduce overall costs. This study examines whether a concurrent or sequential mixed-mode design achieves better results on a number of indicators of survey quality. Data were obtained from a population-based health interview survey of adults in Germany that was conducted as a methodological pilot study as part of the German Health Update (GEDA). Participants were randomly allocated to one of two surveys; each of the surveys had a different design. In the concurrent mixed-mode design ( n  = 617) two types of self-administered questionnaires (SAQ-Web and SAQ-Paper) and computer-assisted telephone interviewing were offered simultaneously to the respondents along with the invitation to participate. In the sequential mixed-mode design ( n  = 561), SAQ-Web was initially provided, followed by SAQ-Paper, with an option for a telephone interview being sent out together with the reminders at a later date. Finally, this study compared the response rates, sample composition, health indicators, item non-response, the scope of fieldwork and the costs of both designs. No systematic differences were identified between the two mixed-mode designs in terms of response rates, the socio-demographic characteristics of the achieved samples, or the prevalence rates of the health indicators under study. The sequential design gained a higher rate of online respondents. Very few telephone interviews were conducted for either design. With regard to data quality, the sequential design (which had more online respondents) showed less item non-response. There were minor differences between the designs in terms of their costs. Postage and printing costs were lower in the concurrent design, but labour costs were lower in the sequential design. No differences in health indicators were found between the two designs. Modelling these results for higher response rates and larger net sample sizes indicated that the sequential design was more cost and time-effective. This study contributes to the research available on implementing mixed-mode designs as part of public health surveys. Our findings show that SAQ-Paper and SAQ-Web questionnaires can be combined effectively. Sequential mixed-mode designs with higher rates of online respondents may be of greater benefit to studies with larger net sample sizes than concurrent mixed-mode designs.

Analysis of the Murine Immune Response to Pulmonary Delivery of Precisely Fabricated Nano- and Microscale Particles

PubMed Central

Roberts, Reid A.; Shen, Tammy; Allen, Irving C.; Hasan, Warefta; DeSimone, Joseph M.; Ting, Jenny P. Y.

2013-01-01

Nanomedicine has the potential to transform clinical care in the 21st century. However, a precise understanding of how nanomaterial design parameters such as size, shape and composition affect the mammalian immune system is a prerequisite for the realization of nanomedicine's translational promise. Herein, we make use of the recently developed Particle Replication in Non-wetting Template (PRINT) fabrication process to precisely fabricate particles across and the nano- and micro-scale with defined shapes and compositions to address the role of particle design parameters on the murine innate immune response in both in vitro and in vivo settings. We find that particles composed of either the biodegradable polymer poly(lactic-co-glycolic acid) (PLGA) or the biocompatible polymer polyethylene glycol (PEG) do not cause release of pro-inflammatory cytokines nor inflammasome activation in bone marrow-derived macrophages. When instilled into the lungs of mice, particle composition and size can augment the number and type of innate immune cells recruited to the lungs without triggering inflammatory responses as assayed by cytokine release and histopathology. Smaller particles (80×320 nm) are more readily taken up in vivo by monocytes and macrophages than larger particles (6 µm diameter), yet particles of all tested sizes remained in the lungs for up to 7 days without clearance or triggering of host immunity. These results suggest rational design of nanoparticle physical parameters can be used for sustained and localized delivery of therapeutics to the lungs. PMID:23593509

Hydrostatic Stress Effects Incorporated Into the Analysis of the High-Strain-Rate Deformation of Polymer Matrix Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.

2003-01-01

Procedures for modeling the effect of high strain rate on composite materials are needed for designing reliable composite engine cases that are lighter than the metal cases in current use. The types of polymer matrix composites that are likely to be used in such an application have a deformation response that is nonlinear and that varies with strain rate. The nonlinearity and strain rate dependence of the composite response is primarily due to the matrix constituent. Therefore, in developing material models to be used in the design of impact-resistant composite engine cases, the deformation of the polymer matrix must be correctly analyzed. However, unlike in metals, the nonlinear response of polymers depends on the hydrostatic stresses, which must be accounted for within an analytical model. An experimental program has been carried out through a university grant with the Ohio State University to obtain tensile and shear deformation data for a representative polymer for strain rates ranging from quasi-static to high rates of several hundred per second. This information has been used at the NASA Glenn Research Center to develop, characterize, and correlate a material model in which the strain rate dependence and nonlinearity (including hydrostatic stress effects) of the polymer are correctly analyzed. To obtain the material data, Glenn s researchers designed and fabricated test specimens of a representative toughened epoxy resin. Quasi-static tests at low strain rates and split Hopkinson bar tests at high strain rates were then conducted at the Ohio State University. The experimental data confirmed the strong effects of strain rate on both the tensile and shear deformation of the polymer. For the analytical model, Glenn researchers modified state variable constitutive equations previously used for the viscoplastic analysis of metals to allow for the analysis of the nonlinear, strain-rate-dependent polymer deformation. Specifically, we accounted for the effects of hydrostatic stresses. An important discovery in the course of this work was that the hydrostatic stress effects varied during the loading process, which needed to be accounted for within the constitutive equations. The model is characterized primarily by shear data, with tensile data used to characterize the hydrostatic stress effects.

ICAN Computer Code Adapted for Building Materials

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.

1997-01-01

The NASA Lewis Research Center has been involved in developing composite micromechanics and macromechanics theories over the last three decades. These activities have resulted in several composite mechanics theories and structural analysis codes whose applications range from material behavior design and analysis to structural component response. One of these computer codes, the Integrated Composite Analyzer (ICAN), is designed primarily to address issues related to designing polymer matrix composites and predicting their properties - including hygral, thermal, and mechanical load effects. Recently, under a cost-sharing cooperative agreement with a Fortune 500 corporation, Master Builders Inc., ICAN was adapted to analyze building materials. The high costs and technical difficulties involved with the fabrication of continuous-fiber-reinforced composites sometimes limit their use. Particulate-reinforced composites can be thought of as a viable alternative. They are as easily processed to near-net shape as monolithic materials, yet have the improved stiffness, strength, and fracture toughness that is characteristic of continuous-fiber-reinforced composites. For example, particlereinforced metal-matrix composites show great potential for a variety of automotive applications, such as disk brake rotors, connecting rods, cylinder liners, and other hightemperature applications. Building materials, such as concrete, can be thought of as one of the oldest materials in this category of multiphase, particle-reinforced materials. The adaptation of ICAN to analyze particle-reinforced composite materials involved the development of new micromechanics-based theories. A derivative of the ICAN code, ICAN/PART, was developed and delivered to Master Builders Inc. as a part of the cooperative activity.

Application of response surface methodology method in designing corrosion inhibitor

NASA Astrophysics Data System (ADS)

Asmara, Y. P.; Athirah; Siregar, J. P.; Kurniawan, T.; Bachtiar, D.

2017-10-01

In oil and gas pipelines and offshore structure, inhibitors have been considered to be the first choice to reduce corrosion rate. There are many corrosion inhibitor compositions available in the market. To produce the best corrosion inhibitor requires many experimental data which is not efficient. These experiments used response surface methodology (RSM) to select corrosion inhibitor compositions. The experiments investigated effects of corrosion inhibition on corrosion rate of low carbon steel in 3% NaCl solution with different concentrations of selected main inhibitor compositions which are ethyl acetate (EA), ethylene glycol (EG) and sodium benzoate (SB). Corrosion rate were calculated using linear polarization resistance (LPR). All of the experiments were set in natural conditions at pH 7. MINITAB® version 15 was used for data analysis. It is shown that a quadratic model is a representative model can predict best corrosion inhibitor composition comprehensibly.

The scale of landscape fragmentation affects herbivore response to vegetation heterogeneity.

PubMed

Banks, John E

1998-11-01

Using alternating bands of weeds and broccoli I experimentally manipulated vegetation composition and the spatial scale at which the landscape was fragmented in a factorial design. This experimental approach allowed me to distinguish the effect of spatial scale from that of simple crop heterogeneity on crop herbivores. The importance of scale depended on which insect species were examined. Cabbage aphids (Brevicoryne brassicae) were influenced by vegetation composition at all tested scales of fragmentation; cabbage butterflies (Pieris rapae) were not affected by scale or by composition and flea beetles (Phyllotreta cruciferae) revealed a striking dependence on scale of fragmentation as well as an interaction between scale and composition. This approach shows the importance of dissecting out the effects of scale from other aspects of landscape manipulation, and emphasizes the challenge of developing a theory that will enable prediction of species-specific responses to scale.

Tunable Mechanics in Electrospun Composites via Hierarchical Organization.

PubMed

Wanasekara, Nandula D; Matolyak, Lindsay E; Korley, LaShanda T J

2015-10-21

Design strategies from nature provide vital clues for the development of synthetic materials with tunable mechanical properties. Employing the concept of hierarchy and controlled percolation, a new class of polymer nanocomposites containing a montmorillonite (MMT)-reinforced electrospun poly(vinyl alcohol) (PVA) filler embedded within a polymeric matrix of either poly(vinyl acetate) (PVAc) or ethylene oxide-epichlorohydrin copolymer (EO-EPI) were developed to achieve a tunable mechanical response upon exposure to specific stimuli. Mechanical response and switching times upon hydration were shown to be dependent on the weight-fraction of MMT in the PVA electrospun fibers and type of composite matrix. PVA/MMT.PVAc composite films retained excellent two-way switchability for all MMT fractions; however, the switching time upon hydration was decreased dramatically as the MMT content was increased due to the highly hydrophilic nature of MMT. Additionally, for the first time, significant two-way switchability of PVA/MMT.EO-EPI composites was achieved for higher weight fractions (12 wt %) of MMT. An extensive investigation into the effects of fiber diameter, crystallinity, and MMT content revealed that inherent rigidity of MMT platelets plays an important role in controlling the mechanical response of these hierarchical electrospun composites.

Gold nanoparticles-induced enhancement of the analytical response of an electrochemical biosensor based on an organic-inorganic hybrid composite material.

PubMed

Barbadillo, M; Casero, E; Petit-Domínguez, M D; Vázquez, L; Pariente, F; Lorenzo, E

2009-12-15

The design and characterization of a new organic-inorganic hybrid composite material for glucose electrochemical sensing are described. This material is based on the entrapment of both gold nanoparticles (AuNPs) and glucose oxidase, which was chosen as a model, into a sol-gel matrix. The addition of spectroscopic grade graphite to this system, which confers conductivity, leads to the development of a material particularly attractive for electrochemical biosensor fabrication. The characterization of the hybrid composite material was performed using atomic force microscopy and scanning electron microscopy techniques. This composite material was applied to the determination of glucose in presence of hydroxymethylferrocene as a redox mediator. The system exhibits a clear electrocatalytic activity towards glucose, allowing its determination at 250 mV vs Ag/AgCl. The performance of the resulting enzyme biosensor was evaluated in terms of sensitivity, detection limit, linear response range, stability and accuracy. Finally, the enhancement of the analytical response of the resulting biosensor induced by the presence of gold nanoparticles was evaluated by comparison with a similar organic-inorganic hybrid composite material without AuNPs.

Erosion of composite materials

NASA Technical Reports Server (NTRS)

Springer, G. S.

1980-01-01

A model for describing the response of uncoated and coated fiber reinforced composites subjected to repeated impingements of liquid (rain) droplets is presented. The model is based on the concept that fatigue is the dominant factor in the erosion process. Algebraic expressions are provided which give the incubation period, the rate of mass loss past the incubation period, and the total mass loss of the material during rain impact. The influence of material properties on erosion damage and the protection offered by different coatings are discussed and the use of the model in the design in the design of structures and components is illustrated.

The Effect of Response Scale, Administration Mode, and Format on Responses to the CAHPS Clinician and Group Survey

PubMed Central

Drake, Keith M; Hargraves, J Lee; Lloyd, Stephanie; Gallagher, Patricia M; Cleary, Paul D

2014-01-01

Objective To examine how different response scales, methods of survey administration, and survey format affect responses to the CAHPS (Consumer Assessment of Healthcare Providers and Systems) Clinician and Group (CG-CAHPS) survey. Study Design A total of 6,500 patients from a university health center were randomly assigned to receive the following: standard 12-page mail surveys using 4-category or 6-category response scales (on CG-CAHPS composite items), telephone surveys using 4-category or 6-category response scales, or four-page mail surveys. Principal Findings A total of 3,538 patients completed surveys. Composite score means and provider-level reliabilities did not differ between respondents receiving 4-category or 6-category response scale surveys or between 12-page and four-page mail surveys. Telephone respondents gave more positive responses than mail respondents. Conclusions We recommend using 4-category response scales and the four-page mail CG-CAHPS survey. PMID:24471975

Optimization of photocatalytic degradation of palm oil mill effluent in UV/ZnO system based on response surface methodology.

PubMed

Ng, Kim Hoong; Cheng, Yoke Wang; Khan, Maksudur R; Cheng, Chin Kui

2016-12-15

This paper reports on the optimization of palm oil mill effluent (POME) degradation in a UV-activated-ZnO system based on central composite design (CCD) in response surface methodology (RSM). Three potential factors, viz. O 2 flowrate (A), ZnO loading (B) and initial concentration of POME (C) were evaluated for the significance analysis using a 2 3 full factorial design before the optimization process. It is found that all the three main factors were significant, with contributions of 58.27% (A), 15.96% (B) and 13.85% (C), respectively, to the POME degradation. In addition, the interactions between the factors AB, AC and BC also have contributed 4.02%, 3.12% and 1.01% to the POME degradation. Subsequently, all the three factors were subjected to statistical central composite design (CCD) analysis. Quadratic models were developed and rigorously checked. A 3D-response surface was subsequently generated. Two successive validation experiments were carried out and the degradation achieved were 55.25 and 55.33%, contrasted with 52.45% for predicted degradation value. Copyright © 2016 Elsevier Ltd. All rights reserved.

Self-shaping of bioinspired chiral composites

NASA Astrophysics Data System (ADS)

Rong, Qing-Qing; Cui, Yu-Hong; Shimada, Takahiro; Wang, Jian-Shan; Kitamura, Takayuki

2014-08-01

Self-shaping materials such as shape memory polymers have recently drawn considerable attention owing to their high shape-changing ability in response to changes in ambient conditions, and thereby have promising applications in the biomedical, biosensing, soft robotics and aerospace fields. Their design is a crucial issue of both theoretical and technological interest. Motivated by the shape-changing ability of Towel Gourd tendril helices during swelling/deswelling, we present a strategy for realizing self-shaping function through the deformation of micro/nanohelices. To guide the design and fabrication of self-shaping materials, the shape equations of bent configurations, twisted belts, and helices of slender chiral composite are developed using the variation method. Furthermore, it is numerically shown that the shape changes of a chiral composite can be tuned by the deformation of micro/nanohelices and the fabricated fiber directions. This work paves a new way to create self-shaping composites.

Dry sliding behavior of aluminum alloy 8011 with 12% fly ash composites

NASA Astrophysics Data System (ADS)

Magibalan, S.; Senthilkumar, P.; Palanivelu, R.; Senthilkumar, C.; Shivasankaran, N.; Prabu, M.

2018-05-01

This research focused on the fabrication of aluminum alloy 8011 with 12% fly ash (FA) composite (AA8011%–12% FA) using the stir casting method. A three-level central composite design experiment was developed using response surface methodology with various parameters such as load, time, and sliding velocity varied in the range of 5 to 15 N, 5 to 15 min, and 1.5 to 4.5 m.s‑1, respectively. Dry sliding wear tests were performed as per the experimental design using a pin on disc at room temperature. The obtained regression result indicated that the developed model performed well in relating the wear process parameters and predicted the wear behavior of the composite. The surface plot showed that the wear rate increases with increase in load, time, and sliding velocity. Hardness was evaluated by Vickers hardness testing machine. Moreover, the surface morphology of the worn-out composite was examined using a scanning electron microscope.

Structural dynamics of shroudless, hollow fan blades with composite in-lays

NASA Technical Reports Server (NTRS)

Aiello, R. A.; Hirschbein, M. S.; Chamis, C. C.

1982-01-01

Structural and dynamic analyses are presented for a shroudless, hollow titanium fan blade proposed for future use in aircraft turbine engines. The blade was modeled and analyzed using the composite blade structural analysis computer program (COBSTRAN); an integrated program consisting of mesh generators, composite mechanics codes, NASTRAN, and pre- and post-processors. Vibration and impact analyses are presented. The vibration analysis was conducted with COBSTRAN. Results show the effect of the centrifugal force field on frequencies, twist, and blade camber. Bird impact analysis was performed with the multi-mode blade impact computer program. This program uses the geometric model and modal analysis from the COBSTRAN vibration analysis to determine the gross impact response of the fan blades to bird strikes. The structural performance of this blade is also compared to a blade of similar design but with composite in-lays on the outer surface. Results show that the composite in-lays can be selected (designed) to substantially modify the mechanical performance of the shroudless, hollow fan blade.

Structural design of composite rotor blades with consideration of manufacturability, durability, and manufacturing uncertainties

NASA Astrophysics Data System (ADS)

Li, Leihong

A modular structural design methodology for composite blades is developed. This design method can be used to design composite rotor blades with sophisticate geometric cross-sections. This design method hierarchically decomposed the highly-coupled interdisciplinary rotor analysis into global and local levels. In the global level, aeroelastic response analysis and rotor trim are conduced based on multi-body dynamic models. In the local level, variational asymptotic beam sectional analysis methods are used for the equivalent one-dimensional beam properties. Compared with traditional design methodology, the proposed method is more efficient and accurate. Then, the proposed method is used to study three different design problems that have not been investigated before. The first is to add manufacturing constraints into design optimization. The introduction of manufacturing constraints complicates the optimization process. However, the design with manufacturing constraints benefits the manufacturing process and reduces the risk of violating major performance constraints. Next, a new design procedure for structural design against fatigue failure is proposed. This procedure combines the fatigue analysis with the optimization process. The durability or fatigue analysis employs a strength-based model. The design is subject to stiffness, frequency, and durability constraints. Finally, the manufacturing uncertainty impacts on rotor blade aeroelastic behavior are investigated, and a probabilistic design method is proposed to control the impacts of uncertainty on blade structural performance. The uncertainty factors include dimensions, shapes, material properties, and service loads.

An Investigation into the Postbuckling Response of a Single Blade-Stiffened Composite Panel

NASA Astrophysics Data System (ADS)

Spediacci, Alexander Daniel

The large strength reserves of stiffened composite structures in the postbuckling range appeal to the aerospace industry because of the high strength-to weight-ratio. Design and analysis of these large-scale, complex structures is technical, and requires major computational effort. Using the building-block approach, a smaller, single-stringer panel can be a useful and efficient tool for initial design, and can reveal critical behavior of a larger, multi-stringer panel. A characterization, through finite element modeling, of buckling and postbuckling response of a single blade-stiffened composite panel is proposed. Several factors affecting buckling and postbuckling behavior are investigated, including specimen length, initial imperfections, mode switching, and skin stringer separation. Two specimens are repeatedly tested under quasi- static compression loading well into the postbuckling range, showing no sign of damage. The test data from the specimens are used to compare and validate the nonlinear finite element models, show good correlation with the models. Ultimately, this work will serve to demonstrate the safety of stiffened structures operating in the postbuckling range and allow for thinner, lighter structures, which can increase the overall efficiency of aircraft.

Development, Optimization, and Validation of a Microplate Bioassay for Relative Potency Determination of Linezolid Using a Design Space Concept, and its Measurement Uncertainty.

PubMed

Saviano, Alessandro Morais; Francisco, Fabiane Lacerda; Ostronoff, Celina Silva; Lourenço, Felipe Rebello

2015-01-01

The aim of this study was to develop, optimize, and validate a microplate bioassay for relative potency determination of linezolid in pharmaceutical samples using quality-by-design and design space approaches. In addition, a procedure is described for estimating relative potency uncertainty based on microbiological response variability. The influence of culture media composition was studied using a factorial design and a central composite design was adopted to study the influence of inoculum proportion and triphenyltetrazolium chloride in microbial growth. The microplate bioassay was optimized regarding the responses of low, medium, and high doses of linezolid, negative and positive controls, and the slope, intercept, and correlation coefficient of dose-response curves. According to optimization results, design space ranges were established using: (a) low (1.0 μg/mL), medium (2.0 μg/mL), and high (4.0 μg/mL) doses of pharmaceutical samples and linezolid chemical reference substance; (b) Staphylococcus aureus ATCC 653 in an inoculum proportion of 10%; (c) antibiotic No. 3 culture medium pH 7.0±0.1; (d) 6 h incubation at 37.0±0.1ºC; and (e) addition of 50 μL of 0.5% (w/v) triphenyltetrazolium chloride solution. The microplate bioassay was linear (r2=0.992), specific, precise (repeatability RSD=2.3% and intermediate precision RSD=4.3%), accurate (mean recovery=101.4%), and robust. The overall measurement uncertainty was reasonable considering the increased variability inherent in microbiological response. Final uncertainty was comparable with those obtained with other microbiological assays, as well as chemical methods.

Modeling Carbon-Black/Polymer Composite Sensors

PubMed Central

Lei, Hua; Pitt, William G.; McGrath, Lucas K.; Ho, Clifford K.

2012-01-01

Conductive polymer composite sensors have shown great potential in identifying gaseous analytes. To more thoroughly understand the physical and chemical mechanisms of this type of sensor, a mathematical model was developed by combining two sub-models: a conductivity model and a thermodynamic model, which gives a relationship between the vapor concentration of analyte(s) and the change of the sensor signals. In this work, 64 chemiresistors representing eight different carbon concentrations (8–60 vol% carbon) were constructed by depositing thin films of a carbon-black/polyisobutylene composite onto concentric spiral platinum electrodes on a silicon chip. The responses of the sensors were measured in dry air and at various vapor pressures of toluene and trichloroethylene. Three parameters in the conductivity model were determined by fitting the experimental data. It was shown that by applying this model, the sensor responses can be adequately predicted for given vapor pressures; furthermore the analyte vapor concentrations can be estimated based on the sensor responses. This model will guide the improvement of the design and fabrication of conductive polymer composite sensors for detecting and identifying mixtures of organic vapors. PMID:22518071

Investigation of mechanical properties of kenaf, hemp and E-glass fiber reinforced composites

NASA Astrophysics Data System (ADS)

Dinesh, Veena; Shivanand, H. K.; Vidyasagar, H. N.; Chari, V. Srinivasa

2018-04-01

Recently the use of fiber reinforced polymer composite in the automobile, aerospace overwhelming designing sectors has increased tremendously due to the ecological issues and health hazard possessed by the synthetic fiber during disposal and manufacturing. The paper presents tensile strength, flexural strength and hardness of kenaf-E glass-kenaf, hemp-E glass-hemp and kenaf-E glass-hemp fiber reinforced polyester composites. The composite plates are shaped according to the standard geometry and uni-axially loaded in order to investigate the tensile responses of each combination. In addition to the physical and mechanical properties, processing methods and application of kenaf and hemp fiber composites is also discussed.

Structural Design of a Horizontal-Axis Tidal Current Turbine Composite Blade

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bir, G. S.; Lawson, M. J.; Li, Y.

2011-10-01

This paper describes the structural design of a tidal composite blade. The structural design is preceded by two steps: hydrodynamic design and determination of extreme loads. The hydrodynamic design provides the chord and twist distributions along the blade length that result in optimal performance of the tidal turbine over its lifetime. The extreme loads, i.e. the extreme flap and edgewise loads that the blade would likely encounter over its lifetime, are associated with extreme tidal flow conditions and are obtained using a computational fluid dynamics (CFD) software. Given the blade external shape and the extreme loads, we use a laminate-theory-basedmore » structural design to determine the optimal layout of composite laminas such that the ultimate-strength and buckling-resistance criteria are satisfied at all points in the blade. The structural design approach allows for arbitrary specification of the chord, twist, and airfoil geometry along the blade and an arbitrary number of shear webs. In addition, certain fabrication criteria are imposed, for example, each composite laminate must be an integral multiple of its constituent ply thickness. In the present effort, the structural design uses only static extreme loads; dynamic-loads-based fatigue design will be addressed in the future. Following the blade design, we compute the distributed structural properties, i.e. flap stiffness, edgewise stiffness, torsion stiffness, mass, moments of inertia, elastic-axis offset, and center-of-mass offset along the blade. Such properties are required by hydro-elastic codes to model the tidal current turbine and to perform modal, stability, loads, and response analyses.« less

Machinability Study on Milling Kenaf Fiber Reinforced Plastic Composite Materials using Design of Experiments

NASA Astrophysics Data System (ADS)

Azmi, H.; Haron, C. H. C.; Ghani, J. A.; Suhaily, M.; Yuzairi, A. R.

2018-04-01

The surface roughness (Ra) and delamination factor (Fd) of a milled kenaf reinforced plastic composite materials are depending on the milling parameters (spindle speed, feed rate and depth of cut). Therefore, a study was carried out to investigate the relationship between the milling parameters and their effects on a kenaf reinforced plastic composite materials. The composite panels were fabricated using vacuum assisted resin transfer moulding (VARTM) method. A full factorial design of experiments was use as an initial step to screen the significance of the parameters on the defects using Analysis of Variance (ANOVA). If the curvature of the collected data shows significant, Response Surface Methodology (RSM) is then applied for obtaining a quadratic modelling equation that has more reliable in expressing the optimization. Thus, the objective of this research is obtaining an optimum setting of milling parameters and modelling equations to minimize the surface roughness (Ra) and delamination factor (Fd) of milled kenaf reinforced plastic composite materials. The spindle speed and feed rate contributed the most in affecting the surface roughness and the delamination factor of the kenaf composite materials.

Strain Rate Dependent Deformation and Strength Modeling of a Polymer Matrix Composite Utilizing a Micromechanics Approach. Degree awarded by Cincinnati Univ.

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.

1999-01-01

Potential gas turbine applications will expose polymer matrix composites to very high strain rate loading conditions, requiring an ability to understand and predict the material behavior under extreme conditions. Specifically, analytical methods designed for these applications must have the capability of properly capturing the strain rate sensitivities and nonlinearities that are present in the material response. The Ramaswamy-Stouffer constitutive equations, originally developed to analyze the viscoplastic deformation of metals, have been modified to simulate the nonlinear deformation response of ductile, crystalline polymers. The constitutive model is characterized and correlated for two representative ductile polymers. Fiberite 977-2 and PEEK, and the computed results correlate well with experimental values. The polymer constitutive equations are implemented in a mechanics of materials based composite micromechanics model to predict the nonlinear, rate dependent deformation response of a composite ply. Uniform stress and uniform strain assumptions are applied to compute the effective stresses of a composite unit cell from the applied strains. The micromechanics equations are successfully verified for two polymer matrix composites. IM7/977-2 and AS4/PEEK. The ultimate strength of a composite ply is predicted with the Hashin failure criteria that were implemented in the composite micromechanics model. The failure stresses of the two composite material systems are accurately predicted for a variety of fiber orientations and strain rates. The composite deformation model is implemented in LS-DYNA, a commercially available transient dynamic explicit finite element code. The matrix constitutive equations are converted into an incremental form, and the model is implemented into LS-DYNA through the use of a user defined material subroutine. The deformation response of a bulk polymer and a polymer matrix composite are predicted by finite element analyses. The results compare reasonably well to experimental values, with some discrepancies. The discrepancies are at least partially caused by the method used to integrate the rate equations in the polymer constitutive model.

A Rapid Aerodynamic Design Procedure Based on Artificial Neural Networks

NASA Technical Reports Server (NTRS)

Rai, Man Mohan

2001-01-01

An aerodynamic design procedure that uses neural networks to model the functional behavior of the objective function in design space has been developed. This method incorporates several improvements to an earlier method that employed a strategy called parameter-based partitioning of the design space in order to reduce the computational costs associated with design optimization. As with the earlier method, the current method uses a sequence of response surfaces to traverse the design space in search of the optimal solution. The new method yields significant reductions in computational costs by using composite response surfaces with better generalization capabilities and by exploiting synergies between the optimization method and the simulation codes used to generate the training data. These reductions in design optimization costs are demonstrated for a turbine airfoil design study where a generic shape is evolved into an optimal airfoil.

X-34 Main Propulsion System Design and Operation

NASA Technical Reports Server (NTRS)

Champion, R. J., Jr.; Darrow, R. J., Jr.

1998-01-01

The X-34 program is a joint industry/government program to develop, test, and operate a small, fully-reusable hypersonic flight vehicle, utilizing technologies and operating concepts applicable to future Reusable Launch Vehicle (RLV) systems. The vehicle will be capable of Mach 8 flight to 250,000 feet altitude and will demonstrate an all composite structure, composite RP-1 tank, the Marshall Space Flight Center (MSFC) developed Fastrac engine, and the operability of an advanced thermal protection systems. The vehicle will also be capable of carrying flight experiments. MSFC is supporting the X-34 program in three ways: Program Management, the Fastrac engine as Government Furnished Equipment (GFE), and the design of the Main Propulsion System (MPS). The MPS Product Development Team (PDT) at MSFC is responsible for supplying the MPS design, analysis, and drawings to Orbital. The MPS consists of the LOX and RP-1 Fill, Drain, Feed, Vent, & Dump systems and the Helium & Nitrogen Purge, Pressurization, and Pneumatics systems. The Reaction Control System (RCS) design was done by Orbital. Orbital is the prime contractor and has responsibility for integration, procurement, and construction of all subsystems. The paper also discusses the design, operation, management, requirements, trades studies, schedule, and lessons learning with the MPS and RCS designs.

The impact behaviour of silk cocoons.

PubMed

Chen, Fujia; Hesselberg, Thomas; Porter, David; Vollrath, Fritz

2013-07-15

Silk cocoons, constructed by silkmoths (Lepidoptera), are protective structural composites. Some cocoons appear to have evolved towards structural and material optimisation in order to sustain impact strikes from predators and hinder parasite ingress. This study investigates the protective properties of silk cocoons with different morphologies by evaluating their impact resistance and damage tolerance. Finite element analysis was used to analyse empirical observations of the quasi-static impact response of the silk cocoons, and to evaluate the separate benefits of the structures and materials through the deformation and damage mechanism. We use design principles from composite engineering in order to understand the structure-property-function relationship of silkworm cocoons. Understanding the highly evolved survival strategies of the organisms building natural cocoons will hopefully lead to inspiration that in turn could lead to improved composite design.

Erosive Burning of Composite Solid Propellants: Experimental and Modeling Studies

DTIC Science & Technology

1978-08-01

of Crossflow on Solid Pro- appears that an additional mechanism(s) of erosive pallant Combustion: Interior Ballistic Design burning will have to be...Orlondo, Florida, July , 1977, AIAA Paper 77-930. 14. Lengelle,G., "Model Describing the Erosive Com- bustion and Velocity Response of Composite Pro...Propulsion Conference, Orlando, Florida, July , 1977. 17. Beddini, R.A., A Reacting Turbulent Boundary Layer Approach to Solid Propellant Erosive Burning, AFOSR

Dynamic Response and Failure Mechanisms of Layered Ceramic-Elastomer-Polymer/Metal Composites

DTIC Science & Technology

2010-08-20

characterization of each material constituent of interest, i.e., polyurea and DH-36 steel, over broad ranges of deformation rates, strains, and temperature of...metal-metal, metal- polyurea -metal and polyurea -ceramic composites. New steel plate designs with different thicknesses were employed to avoid tearing...of the sample at its supporting ring. New experiments support the hypothesis that the steel- polyurea sandwich samples show a noticeably better

Modelling of Damage Evolution in Braided Composites: Recent Developments

NASA Astrophysics Data System (ADS)

Wang, Chen; Roy, Anish; Silberschmidt, Vadim V.; Chen, Zhong

2017-12-01

Composites reinforced with woven or braided textiles exhibit high structural stability and excellent damage tolerance thanks to yarn interlacing. With their high stiffness-to-weight and strength-to-weight ratios, braided composites are attractive for aerospace and automotive components as well as sports protective equipment. In these potential applications, components are typically subjected to multi-directional static, impact and fatigue loadings. To enhance material analysis and design for such applications, understanding mechanical behaviour of braided composites and development of predictive capabilities becomes crucial. Significant progress has been made in recent years in development of new modelling techniques allowing elucidation of static and dynamic responses of braided composites. However, because of their unique interlacing geometric structure and complicated failure modes, prediction of damage initiation and its evolution in components is still a challenge. Therefore, a comprehensive literature analysis is presented in this work focused on a review of the state-of-the-art progressive damage analysis of braided composites with finite-element simulations. Recently models employed in the studies on mechanical behaviour, impact response and fatigue analyses of braided composites are presented systematically. This review highlights the importance, advantages and limitations of as-applied failure criteria and damage evolution laws for yarns and composite unit cells. In addition, this work provides a good reference for future research on FE simulations of braided composites.

An Optimization-Based Approach to Injector Element Design

NASA Technical Reports Server (NTRS)

Tucker, P. Kevin; Shyy, Wei; Vaidyanathan, Rajkumar; Turner, Jim (Technical Monitor)

2000-01-01

An injector optimization methodology, method i, is used to investigate optimal design points for gaseous oxygen/gaseous hydrogen (GO2/GH2) injector elements. A swirl coaxial element and an unlike impinging element (a fuel-oxidizer-fuel triplet) are used to facilitate the study. The elements are optimized in terms of design variables such as fuel pressure drop, APf, oxidizer pressure drop, deltaP(sub f), combustor length, L(sub comb), and full cone swirl angle, theta, (for the swirl element) or impingement half-angle, alpha, (for the impinging element) at a given mixture ratio and chamber pressure. Dependent variables such as energy release efficiency, ERE, wall heat flux, Q(sub w), injector heat flux, Q(sub inj), relative combustor weight, W(sub rel), and relative injector cost, C(sub rel), are calculated and then correlated with the design variables. An empirical design methodology is used to generate these responses for both element types. Method i is then used to generate response surfaces for each dependent variable for both types of elements. Desirability functions based on dependent variable constraints are created and used to facilitate development of composite response surfaces representing the five dependent variables in terms of the input variables. Three examples illustrating the utility and flexibility of method i are discussed in detail for each element type. First, joint response surfaces are constructed by sequentially adding dependent variables. Optimum designs are identified after addition of each variable and the effect each variable has on the element design is illustrated. This stepwise demonstration also highlights the importance of including variables such as weight and cost early in the design process. Secondly, using the composite response surface that includes all five dependent variables, unequal weights are assigned to emphasize certain variables relative to others. Here, method i is used to enable objective trade studies on design issues such as component life and thrust to weight ratio. Finally, combining results from both elements to simulate a trade study, thrust-to-weight trends are illustrated and examined in detail.

Mechanics of damping for fiber composite laminates including hygro-thermal effects

NASA Technical Reports Server (NTRS)

Saravanos, D. A.; Chamis, C. C.

1989-01-01

An integrated mechanics theory has been developed for the modeling of composite damping from the micromechanics to the laminate level. Simplified, design oriented equations based on hysteretic damping are presented for on-axis plies, off-axis plies, and laminates including the effect of temperature, moisture, and interply hysteretic damping. The temperature rise within vibrating composite laminates resulting from strain energy dissipation is also modeled, and their coupled hygro-thermo-mechanical response is predicted. The method correlates well with reported damping measurements. Application examples illustrate the effect of various ply, laminate, and hygro-thermal parameters on the overall damping performance of composite laminates.

Mechanics of damping for fiber composite laminates including hygro-thermal effects

NASA Technical Reports Server (NTRS)

Saravanos, D. A.; Chamis, Christos C.

1989-01-01

An integrated mechanics theory was developed for the modeling of composite damping from the micromechanics to the laminate level. Simplified, design oriented equations based on hysteretic damping are presented for on-axis plies, off-axis plies, and laminates including the effect of temperature, moisture, and interply hysteretic damping. The temperature rise within vibrating composite laminates resulting from strain energy dissipation is also modeled, and their coupled hygro-thermo-mechanical response is predicted. The method correlates well with reported damping measurements. Application examples illustrate the effect of various ply, laminate, and hygro-thermal parameters on the overall damping performance of composite laminates.

Discontinuously Stiffened Composite Panel under Compressive Loading

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Rivers, James M.; Chamis, Christos C.; Murthy, Pappu L. N.

1995-01-01

The design of composite structures requires an evaluation of their safety and durability under service loads and possible overload conditions. This paper presents a computational tool that has been developed to examine the response of stiffened composite panels via the simulation of damage initiation, growth, accumulation, progression, and propagation to structural fracture or collapse. The structural durability of a composite panel with a discontinuous stiffener is investigated under compressive loading induced by the gradual displacement of an end support. Results indicate damage initiation and progression to have significant effects on structural behavior under loading. Utilization of an integrated computer code for structural durability assessment is demonstrated.

Probabilistic Simulation of Multi-Scale Composite Behavior

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

2012-01-01

A methodology is developed to computationally assess the non-deterministic composite response at all composite scales (from micro to structural) due to the uncertainties in the constituent (fiber and matrix) properties, in the fabrication process and in structural variables (primitive variables). The methodology is computationally efficient for simulating the probability distributions of composite behavior, such as material properties, laminate and structural responses. Bi-products of the methodology are probabilistic sensitivities of the composite primitive variables. The methodology has been implemented into the computer codes PICAN (Probabilistic Integrated Composite ANalyzer) and IPACS (Integrated Probabilistic Assessment of Composite Structures). The accuracy and efficiency of this methodology are demonstrated by simulating the uncertainties in composite typical laminates and comparing the results with the Monte Carlo simulation method. Available experimental data of composite laminate behavior at all scales fall within the scatters predicted by PICAN. Multi-scaling is extended to simulate probabilistic thermo-mechanical fatigue and to simulate the probabilistic design of a composite redome in order to illustrate its versatility. Results show that probabilistic fatigue can be simulated for different temperature amplitudes and for different cyclic stress magnitudes. Results also show that laminate configurations can be selected to increase the redome reliability by several orders of magnitude without increasing the laminate thickness--a unique feature of structural composites. The old reference denotes that nothing fundamental has been done since that time.

Optimizing the parameters of heat transmission in a small heat exchanger with spiral tapes cut as triangles and Aluminum oxide nanofluid using central composite design method

NASA Astrophysics Data System (ADS)

Ghasemi, Nahid; Aghayari, Reza; Maddah, Heydar

2018-07-01

The present study aims at optimizing the heat transmission parameters such as Nusselt number and friction factor in a small double pipe heat exchanger equipped with rotating spiral tapes cut as triangles and filled with aluminum oxide nanofluid. The effects of Reynolds number, twist ratio (y/w), rotating twisted tape and concentration (w%) on the Nusselt number and friction factor are also investigated. The central composite design and the response surface methodology are used for evaluating the responses necessary for optimization. According to the optimal curves, the most optimized value obtained for Nusselt number and friction factor was 146.6675 and 0.06020, respectively. Finally, an appropriate correlation is also provided to achieve the optimal model of the minimum cost. Optimization results showed that the cost has decreased in the best case.

Optimizing the parameters of heat transmission in a small heat exchanger with spiral tapes cut as triangles and Aluminum oxide nanofluid using central composite design method

NASA Astrophysics Data System (ADS)

Ghasemi, Nahid; Aghayari, Reza; Maddah, Heydar

2018-02-01

The present study aims at optimizing the heat transmission parameters such as Nusselt number and friction factor in a small double pipe heat exchanger equipped with rotating spiral tapes cut as triangles and filled with aluminum oxide nanofluid. The effects of Reynolds number, twist ratio (y/w), rotating twisted tape and concentration (w%) on the Nusselt number and friction factor are also investigated. The central composite design and the response surface methodology are used for evaluating the responses necessary for optimization. According to the optimal curves, the most optimized value obtained for Nusselt number and friction factor was 146.6675 and 0.06020, respectively. Finally, an appropriate correlation is also provided to achieve the optimal model of the minimum cost. Optimization results showed that the cost has decreased in the best case.

Non-destructive evaluation of laminated composite plates using dielectrometry sensors

NASA Astrophysics Data System (ADS)

Nassr, Amr A.; El-Dakhakhni, Wael W.

2009-05-01

The use of composite materials in marine, aerospace and automotive applications is increasing; however, several kinds of damages of composite materials may influence its durability and future applications. In this paper, a methodology was presented for damage detection of laminated composite plates using dielectrometry sensors. The presence of damage in the laminated composite plate leads to changes in its dielectric characteristics, causing variation in the measured capacitance by the sensors. An analytical model was used to analyse the influence of different sensor parameters on the output signals and to optimize sensor design. Two-dimensional finite element (FE) simulations were performed to assess the validity of the analytical results and to evaluate other sensor design-related parameters. To experimentally verify the model, the dielectric permittivity of the composite plate was measured. In addition, a glass fibre reinforced polymer (GFRP) laminated plate containing pre-fabricated slots through its thickness to simulate delamination and water intrusion defects was inspected in a laboratory setting. Excellent agreements were found between the experimental capacitance response signals and those predicated from the FE simulations. This cost-effective technique can be used for rapid damage screening, regular scheduled inspection, or as a permanent sensor network within the composite system.

Optimum Design of a Helicopter Rotor for Low Vibration Using Aeroelastic Analysis and Response Surface Methods

NASA Astrophysics Data System (ADS)

Ganguli, R.

2002-11-01

An aeroelastic analysis based on finite elements in space and time is used to model the helicopter rotor in forward flight. The rotor blade is represented as an elastic cantilever beam undergoing flap and lag bending, elastic torsion and axial deformations. The objective of the improved design is to reduce vibratory loads at the rotor hub that are the main source of helicopter vibration. Constraints are imposed on aeroelastic stability, and move limits are imposed on the blade elastic stiffness design variables. Using the aeroelastic analysis, response surface approximations are constructed for the objective function (vibratory hub loads). It is found that second order polynomial response surfaces constructed using the central composite design of the theory of design of experiments adequately represents the aeroelastic model in the vicinity of the baseline design. Optimization results show a reduction in the objective function of about 30 per cent. A key accomplishment of this paper is the decoupling of the analysis problem and the optimization problems using response surface methods, which should encourage the use of optimization methods by the helicopter industry.

A study on the performance of piezoelectric composite materials for designing embedded transducers for concrete assessment

NASA Astrophysics Data System (ADS)

Dumoulin, Cédric; Deraemaeker, Arnaud

2018-03-01

Ultrasonic measurements of concrete can provide crucial information about its state of health. The most common practice in the construction industry consists in using external probes which strongly limits the use of the method since large parts of the in-service structures are difficult to access. It is also possible to assess in real time the setting process of the concrete using ultrasonic measurements. In practice, the field measurement of the concrete hardening is limited by the formworks. As an alternative, some research teams have studied the possibility to directly embed the transducers into the concrete structures. The current embedded ultrasonic transducers are of two categories: bulk piezoelectric elements surrounded by several coating and matching layers and composites piezoelectric elements. Both technologies aim at optimizing the wave energy transmitted to the tested medium. The performances of the transducers of the first kind have been studied in a previous study. A fair amount of recent research has been focused on the development of novel cement-based piezoelectric composites. In this study, we first compare the effective properties of such cement-based materials with more widespread composites made with matrices of epoxy resins or polyurethane. The study only concerns the 1-3 fiber arrangement composites. The effective properties are computed using both an analytical mixing rule method and a finite element based homogenization method using representative volume elements (RVEs) which allows for considering more realistic fiber arrangements, leading yet to very similar results. The effective piezoelectric properties of cement-based composites appear to be very low compared to composites made of epoxy or polyurethane. This result is underlined by looking at the acoustic response and the electric input impedance of different piezoelectric disks where we compare performances of such transducers with a low-cost bulk piezoelectric disc element. The first radial mode of the latter is responsible for an acoustic response of the same order of magnitude as those for the piezo-composites. This result confirms that the design of efficient low-cost embedded ultrasonic transducers can be done with such piezoceramic disks.

Low velocity impact analysis of composite laminated plates

NASA Astrophysics Data System (ADS)

Zheng, Daihua

2007-12-01

In the past few decades polymer composites have been utilized more in structures where high strength and light weight are major concerns, e.g., aircraft, high-speed boats and sports supplies. It is well known that they are susceptible to damage resulting from lateral impact by foreign objects, such as dropped tools, hail and debris thrown up from the runway. The impact response of the structures depends not only on the material properties but also on the dynamic behavior of the impacted structure. Although commercial software is capable of analyzing such impact processes, it often requires extensive expertise and rigorous training for design and analysis. Analytical models are useful as they allow parametric studies and provide a foundation for validating the numerical results from large-scale commercial software. Therefore, it is necessary to develop analytical or semi-analytical models to better understand the behaviors of composite structures under impact and their associated failure process. In this study, several analytical models are proposed in order to analyze the impact response of composite laminated plates. Based on Meyer's Power Law, a semi-analytical model is obtained for small mass impact response of infinite composite laminates by the method of asymptotic expansion. The original nonlinear second-order ordinary differential equation is transformed into two linear ordinary differential equations. This is achieved by neglecting high-order terms in the asymptotic expansion. As a result, the semi-analytical solution of the overall impact response can be applied to contact laws with varying coefficients. Then an analytical model accounting for permanent deformation based on an elasto-plastic contact law is proposed to obtain the closed-form solutions of the wave-controlled impact responses of composite laminates. The analytical model is also used to predict the threshold velocity for delamination onset by combining with an existing quasi-static delamination criterion. The predictions are compared with experimental data and explicit finite element LS-DYNA simulation. The comparisons show reasonable agreement. Furthermore, an analytical model is developed to evaluate the combined effects of prestresses and permanent deformation based on the linearized elasto-plastic contact law and the Laplace Transform technique. It is demonstrated that prestresses do not have noticeable effects on the time history of contact force and strains, but they have significant consequences on the plate central displacement. For a impacted composite laminate with the presence of prestresses, the contact force increases with the increasing of the mass of impactor, thickness and interlaminar shear strength of the laminate. The combined analytical and numerical investigations provide validated models for elastic and elasto-plastic impact analysis of composite structures and shed light on the design of impact-resistant composite systems.

Plackett-Burman experimental design to facilitate syntactic foam development

DOE PAGES

Smith, Zachary D.; Keller, Jennie R.; Bello, Mollie; ...

2015-09-14

The use of an eight-experiment Plackett–Burman method can assess six experimental variables and eight responses in a polysiloxane-glass microsphere syntactic foam. The approach aims to decrease the time required to develop a tunable polymer composite by identifying a reduced set of variables and responses suitable for future predictive modeling. The statistical design assesses the main effects of mixing process parameters, polymer matrix composition, microsphere density and volume loading, and the blending of two grades of microspheres, using a dummy factor in statistical calculations. Responses cover rheological, physical, thermal, and mechanical properties. The cure accelerator content of the polymer matrix andmore » the volume loading of the microspheres have the largest effects on foam properties. These factors are the most suitable for controlling the gel point of the curing foam, and the density of the cured foam. The mixing parameters introduce widespread variability and therefore should be fixed at effective levels during follow-up testing. Some responses may require greater contrast in microsphere-related factors. As a result, compared to other possible statistical approaches, the run economy of the Plackett–Burman method makes it a valuable tool for rapidly characterizing new foams.« less

Development and computer implementation of design/analysis techniques for multilayered composite structures. Probabilistic fiber composite micromechanics. M.S. Thesis, Mar. 1987 Final Report, 1 Sep. 1984 - 1 Oct. 1990

NASA Technical Reports Server (NTRS)

Stock, Thomas A.

1995-01-01

Probabilistic composite micromechanics methods are developed that simulate expected uncertainties in unidirectional fiber composite properties. These methods are in the form of computational procedures using Monte Carlo simulation. The variables in which uncertainties are accounted for include constituent and void volume ratios, constituent elastic properties and strengths, and fiber misalignment. A graphite/epoxy unidirectional composite (ply) is studied to demonstrate fiber composite material property variations induced by random changes expected at the material micro level. Regression results are presented to show the relative correlation between predictor and response variables in the study. These computational procedures make possible a formal description of anticipated random processes at the intraply level, and the related effects of these on composite properties.

Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

NASA Technical Reports Server (NTRS)

Davis, Brian; Turner, Travis L.; Seelecke, Stefan

2008-01-01

An experimental and numerical investigation into the static and dynamic responses of shape memory alloy hybrid composite (SMAHC) beams is performed to provide quantitative validation of a recently commercialized numerical analysis/design tool for SMAHC structures. The SMAHC beam specimens consist of a composite matrix with embedded pre-strained SMA actuators, which act against the mechanical boundaries of the structure when thermally activated to adaptively stiffen the structure. Numerical results are produced from the numerical model as implemented into the commercial finite element code ABAQUS. A rigorous experimental investigation is undertaken to acquire high fidelity measurements including infrared thermography and projection moire interferometry for full-field temperature and displacement measurements, respectively. High fidelity numerical results are also obtained from the numerical model and include measured parameters, such as geometric imperfection and thermal load. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

Plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to phosphorus in acid soils.

PubMed

Barbosa, Julierme Z; Motta, Antonio C V; Consalter, Rangel; Poggere, Giovana C; Santin, Delmar; Wendling, Ivar

2018-01-01

Native to subtropical region of South America, yerba mate is responsive to P under some conditions, but the degree of influence of genetic and soil on the growth and composition of the leaf is unknown. The aim of study was to evaluate plant growth, nutrients and potentially toxic elements in leaves of yerba mate clones in response to P application in acid soils. In greenhouse condition, two yerba mate clone seedlings were grown (210 days) in pots, each clone in a completely randomized design in factorial scheme (with and without P; four acid soils). The elemental composition of leaves and the growth of plants were determined. Phosphorus promoted plant growth, but this was not accompanied by increased P in leaf tissue in all conditions tested. The P effect on the elemental composition varied: decrease/null (N, K, Mg, Mn, Cu, Ni, B, Mo, Al, Cd); increase/null (C/N, C, Ca, Fe, V); increase/decrease/null (Zn, Ba, Pb) and; null (Cr). The soils affect the elemental composition of the leaves, especially Mn, with accumulation greater than 1000 mg kg-1. The Ba, Pb, Al and Zn in the leaves varied among clones. Yerba mate response to P was affected by edaphic and plant factors.

Design Analysis and Thermo-Mechanical Fatigue of a Polyimide Composite for Combustion Chamber Support

NASA Technical Reports Server (NTRS)

Thesken, J. C.; Melis, M.; Shin, E.; Sutter, J.; Burke, Chris

2004-01-01

Polyimide composites are being evaluated for use in lightweight support structures designed to preserve the ideal flow geometry within thin shell combustion chambers of future space launch propulsion systems. Principles of lightweight design and innovative manufacturing techniques have yielded a sandwich structure with an outer face sheet of carbon fiber polyimide matrix composite. While the continuous carbon fiber enables laminated skin of high specific stiffness; the polyimide matrix materials ensure that the rigidity and durability is maintained at operation temperatures of 316 C. Significant weight savings over all metal support structures are expected. The protypical structure is the result of ongoing collaboration, between Boeing and NASA-GRC seeking to introduce polyimide composites to the harsh environmental and loads familiar to space launch propulsion systems. Design trade analyses were carried out using relevant closed form solutions, approximations for sandwich beams/panels and finite element analysis. Analyses confirm the significant thermal stresses exist when combining materials whose coefficients of thermal expansion (CTEs) differ by a factor of about 10 for materials such as a polymer composite and metallic structures. The ramifications on design and manufacturing alternatives are reviewed and discussed. Due to stringent durability and safety requirements, serious consideration is being given to the synergistic effects of temperature and mechanical loads. The candidate structure operates at 316 C, about 80% of the glass transition temperature T(sub g). Earlier thermomechanical fatigue (TMF) investigations of chopped fiber polyimide composites made this near to T(sub g), showed that cyclic temperature and stress promoted excessive creep damage and strain accumulation. Here it is important to verify that such response is limited in continuous fiber laminates.

Probabilistic Multi-Scale, Multi-Level, Multi-Disciplinary Analysis and Optimization of Engine Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Abumeri, Galib H.

2000-01-01

Aircraft engines are assemblies of dynamically interacting components. Engine updates to keep present aircraft flying safely and engines for new aircraft are progressively required to operate in more demanding technological and environmental requirements. Designs to effectively meet those requirements are necessarily collections of multi-scale, multi-level, multi-disciplinary analysis and optimization methods and probabilistic methods are necessary to quantify respective uncertainties. These types of methods are the only ones that can formally evaluate advanced composite designs which satisfy those progressively demanding requirements while assuring minimum cost, maximum reliability and maximum durability. Recent research activities at NASA Glenn Research Center have focused on developing multi-scale, multi-level, multidisciplinary analysis and optimization methods. Multi-scale refers to formal methods which describe complex material behavior metal or composite; multi-level refers to integration of participating disciplines to describe a structural response at the scale of interest; multidisciplinary refers to open-ended for various existing and yet to be developed discipline constructs required to formally predict/describe a structural response in engine operating environments. For example, these include but are not limited to: multi-factor models for material behavior, multi-scale composite mechanics, general purpose structural analysis, progressive structural fracture for evaluating durability and integrity, noise and acoustic fatigue, emission requirements, hot fluid mechanics, heat-transfer and probabilistic simulations. Many of these, as well as others, are encompassed in an integrated computer code identified as Engine Structures Technology Benefits Estimator (EST/BEST) or Multi-faceted/Engine Structures Optimization (MP/ESTOP). The discipline modules integrated in MP/ESTOP include: engine cycle (thermodynamics), engine weights, internal fluid mechanics, cost, mission and coupled structural/thermal, various composite property simulators and probabilistic methods to evaluate uncertainty effects (scatter ranges) in all the design parameters. The objective of the proposed paper is to briefly describe a multi-faceted design analysis and optimization capability for coupled multi-discipline engine structures optimization. Results are presented for engine and aircraft type metrics to illustrate the versatility of that capability. Results are also presented for reliability, noise and fatigue to illustrate its inclusiveness. For example, replacing metal rotors with composites reduces the engine weight by 20 percent, 15 percent noise reduction, and an order of magnitude improvement in reliability. Composite designs exist to increase fatigue life by at least two orders of magnitude compared to state-of-the-art metals.

Pyrolysis Model Development for a Multilayer Floor Covering

PubMed Central

McKinnon, Mark B.; Stoliarov, Stanislav I.

2015-01-01

Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design of the built environment, and may be used in forensic investigations of fire events. A major limitation to widespread use of comprehensive pyrolysis models is the large number of parameters required to fully define a material and the lack of effective methodologies for measurement of these parameters, especially for complex materials. The work presented here details a methodology used to characterize the pyrolysis of a low-pile carpet tile, an engineered composite material that is common in commercial and institutional occupancies. The studied material includes three distinct layers of varying composition and physical structure. The methodology utilized a comprehensive pyrolysis model (ThermaKin) to conduct inverse analyses on data collected through several experimental techniques. Each layer of the composite was individually parameterized to identify its contribution to the overall response of the composite. The set of properties measured to define the carpet composite were validated against mass loss rate curves collected at conditions outside the range of calibration conditions to demonstrate the predictive capabilities of the model. The mean error between the predicted curve and the mean experimental mass loss rate curve was calculated as approximately 20% on average for heat fluxes ranging from 30 to 70 kW·m−2, which is within the mean experimental uncertainty. PMID:28793556

Optimal design of composite upper covers of lateral wings with the effect of rib attachment to stiffener webs

NASA Astrophysics Data System (ADS)

Barkanov, E.; Eglītis, E.; Almeida, F.; Bowering, M. C.; Watson, G.

2013-07-01

The present investigation is devoted to the development of new optimal design concepts that exploit the full potential of advanced composite materials in the upper covers of aircraft lateral wings. A finite-element simulation of three-rib-bay laminated composite panels with T-stiffeners and a stiffener pitch of 200 mm is carried out using ANSYS to investigate the effect of rib attachment to stiffener webs on the performance of stiffened panels in terms of their buckling behavior and in relation to skin and stiffener lay-ups, stiffener height, and root width. Due to the large dimension of numerical problems to be solved, an optimization methodology is developed employing the method of experimental design and the response surface technique. Minimal-weight optimization problems were solved for four load levels with account of manufacturing, repairability, and damage tolerance requirements. The optimal results were verified successfully by using the ANSYS and ABAQUS shared-node models.

Fertilizer Response Curves for Commercial Southern Forest Species Defined with an Un-Replicated Experimental Design.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coleman, Mark; Aubrey, Doug; Coyle, David, R.

2005-11-01

There has been recent interest in use of non-replicated regression experimental designs in forestry, as the need for replication in experimental design is burdensome on limited research budgets. We wanted to determine the interacting effects of soil moisture and nutrient availability on the production of various southeastern forest trees (two clones of Populus deltoides, open pollinated Platanus occidentalis, Liquidambar styraciflua and Pinus taeda). Additionally, we required an understanding of the fertilizer response curve. To accomplish both objectives we developed a composite design that includes a core ANOVA approach to consider treatment interactions, with the addition of non-replicated regression plots receivingmore » a range of fertilizer levels for the primary irrigation treatment.« less

Fuel Injector Design Optimization for an Annular Scramjet Geometry

NASA Technical Reports Server (NTRS)

Steffen, Christopher J., Jr.

2003-01-01

A four-parameter, three-level, central composite experiment design has been used to optimize the configuration of an annular scramjet injector geometry using computational fluid dynamics. The computational fluid dynamic solutions played the role of computer experiments, and response surface methodology was used to capture the simulation results for mixing efficiency and total pressure recovery within the scramjet flowpath. An optimization procedure, based upon the response surface results of mixing efficiency, was used to compare the optimal design configuration against the target efficiency value of 92.5%. The results of three different optimization procedures are presented and all point to the need to look outside the current design space for different injector geometries that can meet or exceed the stated mixing efficiency target.

Formulation development and optimization of sustained release matrix tablet of Itopride HCl by response surface methodology and its evaluation of release kinetics

PubMed Central

Bose, Anirbandeep; Wong, Tin Wui; Singh, Navjot

2012-01-01

The objective of this present investigation was to develop and formulate sustained release (SR) matrix tablets of Itopride HCl, by using different polymer combinations and fillers, to optimize by Central Composite Design response surface methodology for different drug release variables and to evaluate drug release pattern of the optimized product. Sustained release matrix tablets of various combinations were prepared with cellulose-based polymers: hydroxy propyl methyl cellulose (HPMC) and polyvinyl pyrolidine (pvp) and lactose as fillers. Study of pre-compression and post-compression parameters facilitated the screening of a formulation with best characteristics that underwent here optimization study by response surface methodology (Central Composite Design). The optimized tablet was further subjected to scanning electron microscopy to reveal its release pattern. The in vitro study revealed that combining of HPMC K100M (24.65 MG) with pvp(20 mg)and use of LACTOSE as filler sustained the action more than 12 h. The developed sustained release matrix tablet of improved efficacy can perform therapeutically better than a conventional tablet. PMID:23960836

Formulation development and optimization of sustained release matrix tablet of Itopride HCl by response surface methodology and its evaluation of release kinetics.

PubMed

Bose, Anirbandeep; Wong, Tin Wui; Singh, Navjot

2013-04-01

The objective of this present investigation was to develop and formulate sustained release (SR) matrix tablets of Itopride HCl, by using different polymer combinations and fillers, to optimize by Central Composite Design response surface methodology for different drug release variables and to evaluate drug release pattern of the optimized product. Sustained release matrix tablets of various combinations were prepared with cellulose-based polymers: hydroxy propyl methyl cellulose (HPMC) and polyvinyl pyrolidine (pvp) and lactose as fillers. Study of pre-compression and post-compression parameters facilitated the screening of a formulation with best characteristics that underwent here optimization study by response surface methodology (Central Composite Design). The optimized tablet was further subjected to scanning electron microscopy to reveal its release pattern. The in vitro study revealed that combining of HPMC K100M (24.65 MG) with pvp(20 mg)and use of LACTOSE as filler sustained the action more than 12 h. The developed sustained release matrix tablet of improved efficacy can perform therapeutically better than a conventional tablet.

Optimization of volatile fatty acid production with co-substrate of food wastes and dewatered excess sludge using response surface methodology.

PubMed

Hong, Chen; Haiyun, Wu

2010-07-01

Central-composite design (CCD) and response surface methodology (RSM) were used to optimize the parameters of volatile fatty acid (VFA) production from food wastes and dewatered excess sludge in a semi-continuous process. The effects of four variables (food wastes composition in the co-substrate of food wastes and excess sludge, hydraulic retention time (HRT), organic loading rate (OLR), and pH) on acidogenesis were evaluated individually and interactively. The optimum condition derived via RSM was food wastes composition, 88.03%; HRT, 8.92 days; OLR, 8.31 g VSS/ld; and pH 6.99. The experimental VFA concentration was 29,099 mg/l under this optimum condition, which was well in agreement with the predicted value of 28,000 mg/l. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

Modeling of Failure for Analysis of Triaxial Braided Carbon Fiber Composites

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Littell, Justin D.; Binienda, Wieslaw K.

2010-01-01

In the development of advanced aircraft-engine fan cases and containment systems, composite materials are beginning to be used due to their low weight and high strength. The design of these structures must include the capability of withstanding impact loads from a released fan blade. Relatively complex triaxially braided fiber architectures have been found to yield the best performance for the fan cases. To properly work with and design these structures, robust analytical tools are required that can be used in the design process. A new analytical approach models triaxially braided carbon fiber composite materials within the environment of a transient dynamic finite-element code, specifically the commercially available transient dynamic finite-element code LS-DYNA. The geometry of the braided composites is approximated by a series of parallel laminated composites. The composite is modeled by using shell finite elements. The material property data are computed by examining test data from static tests on braided composites, where optical strain measurement techniques are used to examine the local strain variations within the material. These local strain data from the braided composite tests are used along with a judicious application of composite micromechanics- based methods to compute the stiffness properties of an equivalent unidirectional laminated composite required for the shell elements. The local strain data from the braided composite tests are also applied to back out strength and failure properties of the equivalent unidirectional composite. The properties utilized are geared towards the application of a continuum damage mechanics-based composite constitutive model available within LS-DYNA. The developed model can be applied to conduct impact simulations of structures composed of triaxially braided composites. The advantage of this technology is that it facilitates the analysis of the deformation and damage response of a triaxially braided polymer matrix composite within the environment of a transient dynamic finite-element code such as LS-DYNA in a manner which accounts for the local physical mechanisms but is still computationally efficient. This methodology is tightly coupled to experimental tests on the braided composite, which ensures that the material properties have physical significance. Aerospace or automotive companies interested in using triaxially braided composites in their structures, particularly for impact or crash applications, would find the technology useful. By the development of improved design tools, the amount of very expensive impact testing that will need to be performed can be significantly reduced.

Quasi-Static Compression and Low-Velocity Impact Behavior of Tri-Axial Bio-Composite Structural Panels Using a Spherical Head

PubMed Central

Li, Jinghao; Hunt, John F; Gong, Shaoqin; Cai, Zhiyong

2017-01-01

This paper presents experimental results of both quasi-static compression and low-velocity impact behavior for tri-axial bio-composite structural panels using a spherical load head. Panels were made having different core and face configurations. The results showed that panels made having either carbon fiber fabric composite faces or a foam-filled core had significantly improved impact and compressive performance over panels without either. Different localized impact responses were observed based on the location of the compression or impact relative to the tri-axial structural core; the core with a smaller structural element had better impact performance. Furthermore, during the early contact phase for both quasi-static compression and low-velocity impact tests, the panels with the same configuration had similar load-displacement responses. The experimental results show basic compression data could be used for the future design and optimization of tri-axial bio-composite structural panels for potential impact applications. PMID:28772542

Influence of engineered interfaces on residual stresses and mechanical response in metal matrix composites

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Wilt, Thomas E.

1992-01-01

Because of the inherent coefficient of thermal expansion (CTE) mismatch between fiber and matrix within metal and intermetallic matrix composite systems, high residual stresses can develop under various thermal loading conditions. These conditions include cooling from processing temperature to room temperature as well as subsequent thermal cycling. As a result of these stresses, within certain composite systems, radial, circumferential, and/or longitudinal cracks have been observed to form at the fiber matrix interface region. A number of potential solutions for reducing this thermally induced residual stress field have been proposed recently. Examples of some potential solutions are high CTE fibers, fiber preheating, thermal anneal treatments, and an engineered interface. Here the focus is on designing an interface (by using a compensating/compliant layer concept) to reduce or eliminate the thermal residual stress field and, therefore, the initiation and propagation of cracks developed during thermal loading. Furthermore, the impact of the engineered interface on the composite's mechanical response when subjected to isothermal mechanical load histories is examined.

Skylab

NASA Image and Video Library

1970-01-01

This chart describes Skylab's Particle Collection device, a scientific experiment designed to study micro-meteoroid particles in near-Earth space and determine their abundance, mass distribution, composition, and erosive effects. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Skylab

NASA Image and Video Library

1970-01-01

This photograph shows Skylab's Particle Collection device, a scientific experiment designed to study micro-meteoroid particles in near-Earth space and determine their abundance, mass distribution, composition, and erosive effects. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Responsive Copolymers for Enhanced Petroleum Recovery

DOE Office of Scientific and Technical Information (OSTI.GOV)

McCormick, C.; Hester, R.

The objectives of this work was to: synthesize responsive copolymer systems; characterize molecular structure and solution behavior; measure rheological properties of aqueous fluids in fixed geometry flow profiles; and to tailor final polymer compositions for in situ rheology control under simulated conditions. This report focuses on the synthesis and characterization of novel stimuli responsive copolymers, the investigation of dilute polymer solutions in extensional flow and the design of a rheometer capable of measuring very dilute aqueous polymer solutions at low torque.

Aerodynamic configuration design using response surface methodology analysis

NASA Technical Reports Server (NTRS)

Engelund, Walter C.; Stanley, Douglas O.; Lepsch, Roger A.; Mcmillin, Mark M.; Unal, Resit

1993-01-01

An investigation has been conducted to determine a set of optimal design parameters for a single-stage-to-orbit reentry vehicle. Several configuration geometry parameters which had a large impact on the entry vehicle flying characteristics were selected as design variables: the fuselage fineness ratio, the nose to body length ratio, the nose camber value, the wing planform area scale factor, and the wing location. The optimal geometry parameter values were chosen using a response surface methodology (RSM) technique which allowed for a minimum dry weight configuration design that met a set of aerodynamic performance constraints on the landing speed, and on the subsonic, supersonic, and hypersonic trim and stability levels. The RSM technique utilized, specifically the central composite design method, is presented, along with the general vehicle conceptual design process. Results are presented for an optimized configuration along with several design trade cases.

Characterization, Modeling, and Failure Analysis of Composite Structure Materials under Static and Dynamic Loading

NASA Astrophysics Data System (ADS)

Werner, Brian Thomas

Composite structures have long been used in many industries where it is advantageous to reduce weight while maintaining high stiffness and strength. Composites can now be found in an ever broadening range of applications: sporting equipment, automobiles, marine and aerospace structures, and energy production. These structures are typically sandwich panels composed of fiber reinforced polymer composite (FRPC) facesheets which provide the stiffness and the strength and a low density polymeric foam core that adds bending rigidity with little additional weight. The expanding use of composite structures exposes them to high energy, high velocity dynamic loadings which produce multi-axial dynamic states of stress. This circumstance can present quite a challenge to designers, as composite structures are highly anisotropic and display properties that are sensitive to loading rates. Computer codes are continually in development to assist designers in the creation of safe, efficient structures. While the design of an optimal composite structure is more complex, engineers can take advantage of the effect of enhanced energy dissipation displayed by a composite when loaded at high strain rates. In order to build and verify effective computer codes, the underlying assumptions must be verified by laboratory experiments. Many of these codes look to use a micromechanical approach to determine the response of the structure. For this, the material properties of the constituent materials must be verified, three-dimensional constitutive laws must be developed, and failure of these materials must be investigated under static and dynamic loading conditions. In this study, simple models are sought not only to ease their implementation into such codes, but to allow for efficient characterization of new materials that may be developed. Characterization of composite materials and sandwich structures is a costly, time intensive process. A constituent based design approach evaluates potential combinations of materials in a much faster and more efficient manner.

[Optimization of process of icraiin be hydrolyzed to Baohuoside I by cellulase based on Plackett-Burman design combined with CCD response surface methodology].

PubMed

Song, Chuan-xia; Chen, Hong-mei; Dai, Yu; Kang, Min; Hu, Jia; Deng, Yun

2014-11-01

To optimize the process of Icraiin be hydrolyzed to Baohuoside I by cellulase by Plackett-Burman design combined with Central Composite Design (CCD) response surface methodology. To select the main influencing factors by Plackett-Burman design, using CCD response surface methodology to optimize the process of Icraiin be hydrolyzed to Baohuoside I by cellulase. Taking substrate concentration, the pH of buffer and reaction time as independent variables, with conversion rate of icariin as dependent variable,using regression fitting of completely quadratic response surface between independent variable and dependent variable,the optimum process of Icraiin be hydrolyzed to Baohuoside I by cellulase was intuitively analyzed by 3D surface chart, and taking verification tests and predictive analysis. The best enzymatic hydrolytic process was as following: substrate concentration 8. 23 mg/mL, pH 5. 12 of buffer,reaction time 35. 34 h. The optimum process of Icraiin be hydrolyzed to Baohuoside I by cellulase is determined by Plackett-Burman design combined with CCD response surface methodology. The optimized enzymatic hydrolytic process is simple, convenient, accurate, reproducible and predictable.

Fabrication and testing of SMA composite beam with shape control

NASA Astrophysics Data System (ADS)

Noolvi, Basavaraj; S, Raja; Nagaraj, Shanmukha; Mudradi, Varada Raj

2017-07-01

Smart materials are the advanced materials that have characteristics of sensing and actuation in response to the external stimuli like pressure, heat or electric charge etc. These materials can be integrated in to any structure to make it smart. From the different types of smart materials available, Shape Memory Alloy (SMA) is found to be more useful in designing new applications, which can offer more actuating speed, reduce the overall weight of the structure. The unique property of SMA is the ability to remember and recover from large strains of upto 8% without permanent deformation. Embedding the SMA wire/sheet in fiber-epoxy/flexible resin systems has many potential applications in Aerospace, Automobile, Medical, Robotics and various other fields. In this work the design, fabrication, and testing of smart SMA composite beam has been carried out. Two types of epoxy based resin systems namely LY 5210 resin system and EPOLAM 2063 resin system are used in fabricating the SMA composite specimens. An appropriate mould is designed and fabricated to retain the pre-strain of SMA wire during high temperature post curing of composite specimens. The specimens are fabricated using vacuum bag technique.

Concurrent Probabilistic Simulation of High Temperature Composite Structural Response

NASA Technical Reports Server (NTRS)

Abdi, Frank

1996-01-01

A computational structural/material analysis and design tool which would meet industry's future demand for expedience and reduced cost is presented. This unique software 'GENOA' is dedicated to parallel and high speed analysis to perform probabilistic evaluation of high temperature composite response of aerospace systems. The development is based on detailed integration and modification of diverse fields of specialized analysis techniques and mathematical models to combine their latest innovative capabilities into a commercially viable software package. The technique is specifically designed to exploit the availability of processors to perform computationally intense probabilistic analysis assessing uncertainties in structural reliability analysis and composite micromechanics. The primary objectives which were achieved in performing the development were: (1) Utilization of the power of parallel processing and static/dynamic load balancing optimization to make the complex simulation of structure, material and processing of high temperature composite affordable; (2) Computational integration and synchronization of probabilistic mathematics, structural/material mechanics and parallel computing; (3) Implementation of an innovative multi-level domain decomposition technique to identify the inherent parallelism, and increasing convergence rates through high- and low-level processor assignment; (4) Creating the framework for Portable Paralleled architecture for the machine independent Multi Instruction Multi Data, (MIMD), Single Instruction Multi Data (SIMD), hybrid and distributed workstation type of computers; and (5) Market evaluation. The results of Phase-2 effort provides a good basis for continuation and warrants Phase-3 government, and industry partnership.

Probabilistic Simulation of Progressive Fracture in Bolted-Joint Composite Laminates

NASA Technical Reports Server (NTRS)

Minnetyan, L.; Singhal, S. N.; Chamis, C. C.

1996-01-01

This report describes computational methods to probabilistically simulate fracture in bolted composite structures. An innovative approach that is independent of stress intensity factors and fracture toughness was used to simulate progressive fracture. The effect of design variable uncertainties on structural damage was also quantified. A fast probability integrator assessed the scatter in the composite structure response before and after damage. Then the sensitivity of the response to design variables was computed. General-purpose methods, which are applicable to bolted joints in all types of structures and in all fracture processes-from damage initiation to unstable propagation and global structure collapse-were used. These methods were demonstrated for a bolted joint of a polymer matrix composite panel under edge loads. The effects of the fabrication process were included in the simulation of damage in the bolted panel. Results showed that the most effective way to reduce end displacement at fracture is to control both the load and the ply thickness. The cumulative probability for longitudinal stress in all plies was most sensitive to the load; in the 0 deg. plies it was very sensitive to ply thickness. The cumulative probability for transverse stress was most sensitive to the matrix coefficient of thermal expansion. In addition, fiber volume ratio and fiber transverse modulus both contributed significantly to the cumulative probability for the transverse stresses in all the plies.

Weight optimal design of lateral wing upper covers made of composite materials

NASA Astrophysics Data System (ADS)

Barkanov, Evgeny; Eglītis, Edgars; Almeida, Filipe; Bowering, Mark C.; Watson, Glenn

2016-09-01

The present investigation is devoted to the development of a new optimal design of lateral wing upper covers made of advanced composite materials, with special emphasis on closer conformity of the developed finite element analysis and operational requirements for aircraft wing panels. In the first stage, 24 weight optimization problems based on linear buckling analysis were solved for the laminated composite panels with three types of stiffener, two stiffener pitches and four load levels, taking into account manufacturing, reparability and damage tolerance requirements. In the second stage, a composite panel with the best weight/design performance from the previous study was verified by nonlinear buckling analysis and optimization to investigate the effect of shear and fuel pressure on the performance of stiffened panels, and their behaviour under skin post-buckling. Three rib-bay laminated composite panels with T-, I- and HAT-stiffeners were modelled with ANSYS, NASTRAN and ABAQUS finite element codes to study their buckling behaviour as a function of skin and stiffener lay-ups, stiffener height, stiffener top and root width. Owing to the large dimension of numerical problems to be solved, an optimization methodology was developed employing the method of experimental design and response surface technique. Optimal results obtained in terms of cross-sectional areas were verified successfully using ANSYS and ABAQUS shared-node models and a NASTRAN rigid-linked model, and were used later to estimate the weight of the Advanced Low Cost Aircraft Structures (ALCAS) lateral wing upper cover.

Composite Cryotank Technologies and Demonstration

NASA Technical Reports Server (NTRS)

Vickers, John

2015-01-01

NASA is exploring advanced composite materials and processes to reduce the overall cost and weight of liquid hydrogen (LH2) cryotanks while maintaining the reliability of existing metallic designs. The fundamental goal of the composite cryotank project was to provide new and innovative technologies that enable human space exploration to destinations beyond low-Earth orbit such as the Moon, near-Earth asteroids, and Mars. In September 2011, NASA awarded Boeing the contract to design, manufacture, and test two lightweight composite cryogenic propellant tanks. The all-composite tanks shown iare fabricated with an automated fiber placement machine using a prepreg system of IM7 carbon fiber/CYCOM 5320-1 epoxy resin. This is a resin system developed for out-of-autoclave applications. Switching from metallic to composite construction holds the potential to dramatically increase the performance capabilities of future space systems through a dramatic reduction in weight. Composite Cryotank Technologies and Demonstration testing was an agency-wide effort with NASA Marshall Space Flight Center (MSFC) leading project management, manufacturing, and test; Glenn Research Center leading the materials; and Langley Research Center leading the structures effort for this project. Significant contributions from NASA loads/stress personnel contributed to the understanding of thermal/mechanical strain response while undergoing testing at cryogenic temperatures. The project finalized in September 2014.

Crash Testing of Helicopter Airframe Fittings

NASA Technical Reports Server (NTRS)

Clarke, Charles W.; Townsend, William; Boitnott, Richard

2004-01-01

As part of the Rotary Wing Structures Technology Demonstration (RWSTD) program, a surrogate RAH-66 seat attachment fitting was dynamically tested to assess its response to transient, crash impact loads. The dynamic response of this composite material fitting was compared to the performance of an identical fitting subjected to quasi-static loads of similar magnitude. Static and dynamic tests were conducted of both smaller bench level and larger full-scale test articles. At the bench level, the seat fitting was supported in a steel fixture, and in the full-scale tests, the fitting was integrated into a surrogate RAH-66 forward fuselage. Based upon the lessons learned, an improved method to design, analyze, and test similar composite material fittings is proposed.

Review on failure prediction techniques of composite single lap joint

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ab Ghani, A.F., E-mail: ahmadfuad@utem.edu.my; Rivai, Ahmad, E-mail: ahmadrivai@utem.edu.my

2016-03-29

Adhesive bonding is the most appropriate joining method in construction of composite structures. The use of reliable design and prediction technique will produce better performance of bonded joints. Several papers from recent papers and journals have been reviewed and synthesized to understand the current state of the art in this area. It is done by studying the most relevant analytical solutions for composite adherends with start of reviewing the most fundamental ones involving beam/plate theory. It is then extended to review single lap joint non linearity and failure prediction and finally on the failure prediction on composite single lap joint.more » The review also encompasses the finite element modelling part as tool to predict the elastic response of composite single lap joint and failure prediction numerically.« less

Simulations as a tool for higher mass resolution spectrometer: Lessons from existing observations

NASA Astrophysics Data System (ADS)

Nicolaou, Georgios; Yamauchi, Masatoshi; Nilsson, Hans; Wieser, Martin; Fedorov, Andrei

2017-04-01

Scientific requirements of each mission are crucial for the instrument's design. Ion tracing simulations of instruments can be helpful to characterize their performance, identify their limitations and improving the design for future missions. However, simulations provide the best performance in ideal case, and the actual response is determined by many other factors. Therefore, simulations should be compared with observations when possible. Characterizing the actual response of a running instrument gives valuable lessons for the future design of test instruments with the same detection principle before spending resources to build and calibrate them. In this study we use an ion tracing simulation of the Ion Composition Analyser (ICA) on board ROSETTA, in order to characterize its response and to compare it with the observations. It turned out that, due to the complicated unexpected response of the running instrument, the heavy cometary ions and molecules are sometimes difficult to be resolved. However, preliminary simulation of a slightly modified design predicts much higher mass resolution. Even after considering the complicated unexpected response, we safely expect that the modified design can resolve most abundant heavy atomic ions (e.g., O^+) and molecular ions (e.g., N_2+ and O_2^+). We show the simulation results for both designs and ICA data.

Integrated actuation and energy harvesting in prestressed piezoelectric synthetic jets

NASA Astrophysics Data System (ADS)

Mane, Poorna

With the looming energy crisis compounded by the global economic downturn there is an urgent need to increase energy efficiency and to discover new energy sources. An approach to solve this problem is to improve the efficiency of aerodynamic vehicles by using active flow control tools such as synthetic jet actuators. These devices are able to reduce fuel consumption and streamlined vehicle design by reducing drag and weight, and increasing maneuverability. Hence, the main goal of this dissertation is to study factors that affect the efficiency of synthetic jets by incorporating energy harvesting into actuator design using prestressed piezoelectric composites. Four state-of-the-art piezoelectric composites were chosen as active diaphragms in synthetic jet actuators. These composites not only overcome the inherent brittle and fragile nature of piezoelectric materials but also enhance domain movement which in turn enhances intrinsic contributions. With these varying characteristics among different types of composites, the intricacies of the synthetic jet design and its implementation increases. In addition the electrical power requirements of piezoelectric materials make the new SJA system a coupled multiphysics problem involving electro-mechanical and structural-fluid interactions. Due to the nature of this system, a design of experiments approach, a method of combining experiments and statistics, is utilized. Geometric and electro-mechanical factors are investigated using a fractional factorial design with peak synthetic jet velocity as a response variable. Furthermore, energy generated by the system oscillations is harvested with a prestressed composite and a piezo-polymer. Using response surface methodology the process is optimized under different temperatures and pressures to simulate harsh environmental conditions. Results of the fractional factorial experimental design showed that cavity dimensions and type of signal used to drive the synthetic jet actuator were statistically significant factors when studying peak jet velocity. The Bimorph (˜50m/s) and the prestressed metal composite (˜45m/s) generated similar peak jet velocities but the later is the most robust of all tested actuators. In addition, an alternate input signal to the composite, a sawtooth waveform, leads to jets formed with larger peak velocities at frequencies above 15Hz. The optimized factor levels for the energy harvesting process were identified as 237.6kPa, 3.7Hz, 1MO and 12°C and the power density measured at these conditions was 24.27microW/mm3. Finally, the SJA is integrated with an energy harvesting system and the power generated is stored into a large capacitor and a rechargeable battery. After approximately six hours of operation 5V of generated voltage is stored in a 330microF capacitor with the prestressed metal composite as the harvester. It is then demonstrated that energy harvested from the inherent vibrations of a SJA can be stored for later use. Then, the system proposed in this dissertation not only improves on the efficiency of aerodynamic bodies, but also harvests energy that is otherwise wasted.

Mechanical Model Development for Composite Structural Supercapacitors

NASA Technical Reports Server (NTRS)

Ricks, Trenton M.; Lacy, Thomas E., Jr.; Santiago, Diana; Bednarcyk, Brett A.

2016-01-01

Novel composite structural supercapacitor concepts have recently been developed as a means both to store electrical charge and to provide modest mechanical load carrying capability. Double-layer composite supercapacitors are often fabricated by impregnating a woven carbon fiber fabric, which serves as the electrodes, with a structural polymer electrolyte. Polypropylene or a glass fabric is often used as the separator material. Recent research has been primarily limited to evaluating these composites experimentally. In this study, mechanical models based on the Multiscale Generalized Method of Cells (MSGMC) were developed and used to calculate the shear and tensile properties and response of two composite structural supercapacitors from the literature. The modeling approach was first validated against traditional composite laminate data. MSGMC models for composite supercapacitors were developed, and accurate elastic shear/tensile properties were obtained. It is envisioned that further development of the models presented in this work will facilitate the design of composite components for aerospace and automotive applications and can be used to screen candidate constituent materials for inclusion in future composite structural supercapacitor concepts.

Shape morphing and motion of responsive hydrogel composites

NASA Astrophysics Data System (ADS)

Hayward, Ryan

Composites of stimuli-responsive hydrogels paired with stiff structural elements or functional inorganic materials offer myriad opportunities to control the shape, properties, and motion of materials. In one example, our group has studied the geometry and mechanics of swelling-induced buckling of polymer trilayer films consisting of patterning rigid layers sandwiching a swellable hydrogel layer. Of particular recent interest has been the formation of helical structures from seedpod-type architectures with perpendicular orientation of stripes on opposite faces. We have studied the concatenation of two or more helical segments, yielding simple geometric design rules for the fabrication of 3D constructs. In a second example, we have considered the light-driven reshaping and motion of hydrogels containing plasmonic nanoparticles as photothermal heating elements. In contrast to systems pre-programmed to take on a single, or perhaps a few, different 3D shapes, this approach enables continuous shape reconfiguration, and correspondingly, directed motion of composite hydrogel sheets.

Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values

NASA Astrophysics Data System (ADS)

Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

2017-06-01

We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO2-SiO2) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO2-SiO2) composite nanofibers. Such flexible inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO2-SiO2 and CuO-TiO2-SiO2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO2-SiO2/PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO2-SiO2/PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO2, and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO2-SiO2/PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

Design of flexible PANI-coated CuO-TiO2-SiO2 heterostructure nanofibers with high ammonia sensing response values.

PubMed

Pang, Zengyuan; Nie, Qingxin; Lv, Pengfei; Yu, Jian; Huang, Fenglin; Wei, Qufu

2017-06-02

We report a room-temperature ammonia sensor with extra high response values and ideal flexibility, including polyaniline (PANI)-coated titanium dioxide-silicon dioxide (TiO 2 -SiO 2 ) or copper oxide-titanium dioxide-silicon dioxide (CuO-TiO 2 -SiO 2 ) composite nanofibers. Such flexible inorganic TiO 2 -SiO 2 and CuO-TiO 2 -SiO 2 composite nanofibers were prepared by electrospinning, followed by calcination. Then, in situ polymerization of aniline monomers was carried out with inorganic TiO 2 -SiO 2 and CuO-TiO 2 -SiO 2 composite nanofibers as templates. Gas sensing tests at room temperature indicated that the obtained CuO-TiO 2 -SiO 2 /PANI composite nanofibers had much higher response values to ammonia gas (ca. 45.67-100 ppm) than most of those reported before as well as the prepared TiO 2 -SiO 2 /PANI composite nanofibers here. These excellent sensing properties may be due to the P-N, P-P heterojunctions and a structure similar to field-effect transistors formed on the interfaces between PANI, TiO 2 , and CuO, which is p-type, n-type, and p-type semiconductor, respectively. In addition, the prepared free-standing CuO-TiO 2 -SiO 2 /PANI composite nanofiber membrane was easy to handle and possessed ideal flexibility, which is promising for potential applications in wearable sensors in the future.

Using the adaptive SMA composite cylinder concept to reduce radial dilation in composite pressure vessels

NASA Astrophysics Data System (ADS)

Paine, Jeffrey S.; Rogers, Craig A.

1995-05-01

Composite materials are widely used in the design of pressurized gas and fluid vessels for applications ranging from underground gasoline storage tanks to rocket motors for the space shuttle. In the design of a high pressure composite vessel (Pi > 12 Ksi), thick-wall (R/h < 15) vessels are required. For efficient material use in composite material vessels, the radial dilation (expansion or swelling) of the composite vessel can often approach values nearing 2 percent of the diameter. Over long periods of internal pressure loading over elevated temperatures, composite material cylinders may also experience substantial creep. The short term dilation and long term creep are not problematic for applications requiring only the containment of the pressurized fluid. In applications where metallic liners are required, however, substantial dilation and creep causes plastic yielding which leads to reduced fatigue life. To applications such as a hydraulic accumulator, where a piston is employed to fit and seal the fluid in the composite cylinder, the dilation and creep may allow leakage and pressure loss around the piston. A concept called the adaptive composite cylinder is experimentally presented. Shape memory alloy wire in epoxy resin is wrapped around or within polymer matrix composite cylinders to reduce radial dilation of the cylinder. Experimental results are presented that demonstrate the ability of the SMA wire layers to reduce radial dilation. Results from experimental testing of the recovery stress fatigue response of nitinol shape memory alloy wires is also presented.

Development of a Lifespan-Based Novel Composite Person-Reported Outcome Measure Using Data from the CINRG Duchenne Natural History Study

DTIC Science & Technology

2016-10-01

and should not be construed as an official Department of the Army position, policy or decision unless so designated by other documentation. REPORT...Applicability: Well- designed CAT-PRO questionnaires can be used in both clinical trials and day-to-day clinical practice. For clinical trials, they provide...confirm that items are responsive to self-reported changes in milestone ability over a time period consistent with design of contemporary clinical

Development of a composite repair and the associated inspection intervals for the F-111C stiffener runout region

NASA Technical Reports Server (NTRS)

Jones, R.; Molent, L.; Paul, J.; Saunders, T.; Chiu, W. K.

1994-01-01

This paper presents an overview of the structural aspects of the design and development of a local reinforcement designed to lower the stresses in a region of the F-111C wing fitting which is prone to cracking. The stress analysis, with particular emphasis on the use of a unified constitutive model for the cyclic inelastic response of the structure, representative specimen testing, thermal analysis and full scale static testing of this design are summarized.

Development of Design Analysis Methods for C/SiC Composite Structures

NASA Technical Reports Server (NTRS)

Sullivan, Roy M.; Mital, Subodh K.; Murthy, Pappu L. N.; Palko, Joseph L.; Cueno, Jacques C.; Koenig, John R.

2006-01-01

The stress-strain behavior at room temperature and at 1100 C (2000 F) was measured for two carbon-fiber-reinforced silicon carbide (C/SiC) composite materials: a two-dimensional plain-weave quasi-isotropic laminate and a three-dimensional angle-interlock woven composite. Micromechanics-based material models were developed for predicting the response properties of these two materials. The micromechanics based material models were calibrated by correlating the predicted material property values with the measured values. Four-point beam bending sub-element specimens were fabricated with these two fiber architectures and four-point bending tests were performed at room temperature and at 1100 C. Displacements and strains were measured at various locations along the beam and recorded as a function of load magnitude. The calibrated material models were used in concert with a nonlinear finite element solution to simulate the structural response of these two materials in the four-point beam bending tests. The structural response predicted by the nonlinear analysis method compares favorably with the measured response for both materials and for both test temperatures. Results show that the material models scale up fairly well from coupon to subcomponent level.

Design and simulation of Macro-Fiber composite based serrated microflap for wind turbine blade fatigue load reduction

NASA Astrophysics Data System (ADS)

Sun, Xiao; Dai, Qingli; Bilgen, Onur

2018-05-01

A Macro-Fiber Composite (MFC) based active serrated microflap is designed in this research for wind turbine blades. Its fatigue load reduction potential is evaluated in normal operating conditions. The force and displacement output of the MFC-based actuator are simulated using a bimorph beam model. The work done by the aerodynamic, centripetal and gravitational forces acting on the microflap were calculated to determine the required capacity of the MFC-based actuator. MFC-based actuators with a lever mechanical linkage are designed to achieve the required force and displacement to activate the microflap. A feedback control scheme is designed to control the microflap during operation. Through an aerodynamic-aeroelastic time marching simulation with the designed control scheme, the time responses of the wind turbine blades are obtained. The fatigue analysis shows that the serrated microflap can reduce the standard deviation of the blade root flapwise bending moment and the fatigue damage equivalent loads.

Particle Collections - Skylab Experiment S149

NASA Technical Reports Server (NTRS)

1970-01-01

This photograph shows Skylab's Particle Collection device, a scientific experiment designed to study micro-meteoroid particles in near-Earth space and determine their abundance, mass distribution, composition, and erosive effects. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Particle Collection - Skylab Experiment S149

NASA Technical Reports Server (NTRS)

1970-01-01

This chart describes Skylab's Particle Collection device, a scientific experiment designed to study micro-meteoroid particles in near-Earth space and determine their abundance, mass distribution, composition, and erosive effects. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Active Vibration damping of Smart composite beams based on system identification technique

NASA Astrophysics Data System (ADS)

Bendine, Kouider; Satla, Zouaoui; Boukhoulda, Farouk Benallel; Nouari, Mohammed

2018-03-01

In the present paper, the active vibration control of a composite beam using piezoelectric actuator is investigated. The space state equation is determined using system identification technique based on the structure input output response provided by ANSYS APDL finite element package. The Linear Quadratic (LQG) control law is designed and integrated into ANSYS APDL to perform closed loop simulations. Numerical examples for different types of excitation loads are presented to test the efficiency and the accuracy of the proposed model.

Towards intelligent microstructural design of Nanocomposite Materials. Lightweight, high strength structural/armor materials for service in extreme environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mara, Nathan Allan; Bronkhorst, Curt Allan; Beyerlein, Irene Jane

2015-12-21

The intent of this research effort is to prove the hypothesis that: Through the employment of controlled processing parameters which are based upon integrated advanced material characterization and multi-physics material modeling, bulk nanolayered composites can be designed to contain high densities of preferred interfaces that can serve as supersinks for the defects responsible for premature damage and failure.

Composite Structure Modeling and Analysis of Advanced Aircraft Fuselage Concepts

NASA Technical Reports Server (NTRS)

Mukhopadhyay, Vivek; Sorokach, Michael R.

2015-01-01

NASA Environmentally Responsible Aviation (ERA) project and the Boeing Company are collabrating to advance the unitized damage arresting composite airframe technology with application to the Hybrid-Wing-Body (HWB) aircraft. The testing of a HWB fuselage section with Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) construction is presently being conducted at NASA Langley. Based on lessons learned from previous HWB structural design studies, improved finite-element models (FEM) of the HWB multi-bay and bulkhead assembly are developed to evaluate the performance of the PRSEUS construction. In order to assess the comparative weight reduction benefits of the PRSEUS technology, conventional cylindrical skin-stringer-frame models of a cylindrical and a double-bubble section fuselage concepts are developed. Stress analysis with design cabin-pressure load and scenario based case studies are conducted for design improvement in each case. Alternate analysis with stitched composite hat-stringers and C-frames are also presented, in addition to the foam-core sandwich frame and pultruded rod-stringer construction. The FEM structural stress, strain and weights are computed and compared for relative weight/strength benefit assessment. The structural analysis and specific weight comparison of these stitched composite advanced aircraft fuselage concepts demonstrated that the pressurized HWB fuselage section assembly can be structurally as efficient as the conventional cylindrical fuselage section with composite stringer-frame and PRSEUS construction, and significantly better than the conventional aluminum construction and the double-bubble section concept.

Scaling effects in the static and dynamic response of graphite-epoxy beam-columns. Ph.D. Thesis - Virginia Polytechnic Inst. and State Univ.

NASA Technical Reports Server (NTRS)

Jackson, Karen E.

1990-01-01

Scale model technology represents one method of investigating the behavior of advanced, weight-efficient composite structures under a variety of loading conditions. It is necessary, however, to understand the limitations involved in testing scale model structures before the technique can be fully utilized. These limitations, or scaling effects, are characterized. in the large deflection response and failure of composite beams. Scale model beams were loaded with an eccentric axial compressive load designed to produce large bending deflections and global failure. A dimensional analysis was performed on the composite beam-column loading configuration to determine a model law governing the system response. An experimental program was developed to validate the model law under both static and dynamic loading conditions. Laminate stacking sequences including unidirectional, angle ply, cross ply, and quasi-isotropic were tested to examine a diversity of composite response and failure modes. The model beams were loaded under scaled test conditions until catastrophic failure. A large deflection beam solution was developed to compare with the static experimental results and to analyze beam failure. Also, the finite element code DYCAST (DYnamic Crash Analysis of STructure) was used to model both the static and impulsive beam response. Static test results indicate that the unidirectional and cross ply beam responses scale as predicted by the model law, even under severe deformations. In general, failure modes were consistent between scale models within a laminate family; however, a significant scale effect was observed in strength. The scale effect in strength which was evident in the static tests was also observed in the dynamic tests. Scaling of load and strain time histories between the scale model beams and the prototypes was excellent for the unidirectional beams, but inconsistent results were obtained for the angle ply, cross ply, and quasi-isotropic beams. Results show that valuable information can be obtained from testing on scale model composite structures, especially in the linear elastic response region. However, due to scaling effects in the strength behavior of composite laminates, caution must be used in extrapolating data taken from a scale model test when that test involves failure of the structure.

Optimization of Machining Process Parameters for Surface Roughness of Al-Composites

NASA Astrophysics Data System (ADS)

Sharma, S.

2013-10-01

Metal matrix composites (MMCs) have become a leading material among the various types of composite materials for different applications due to their excellent engineering properties. Among the various types of composites materials, aluminum MMCs have received considerable attention in automobile and aerospace applications. These materials are known as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcement element-like silicon carbide particles. In the present investigation Al-SiC composite was produced by stir casting process. The Brinell hardness of the alloy after SiC addition had increased from 74 ± 2 to 95 ± 5 respectively. The composite was machined using CNC turning center under different machining parameters such as cutting speed (S), feed rate (F), depth of cut (D) and nose radius (R). The effect of machining parameters on surface roughness (Ra) was studied using response surface methodology. Face centered composite design with three levels of each factor was used for surface roughness study of the developed composite. A response surface model for surface roughness was developed in terms of main factors (S, F, D and R) and their significant interactions (SD, SR, FD and FR). The developed model was validated by conducting experiments under different conditions. Further the model was optimized for minimum surface roughness. An error of 3-7 % was observed in the modeled and experimental results. Further, it was fond that the surface roughness of Al-alloy at optimum conditions is lower than that of Al-SiC composite.

Experimental designs for modeling retention patterns and separation efficiency in analysis of fatty acid methyl esters by gas chromatography-mass spectrometry.

PubMed

Skartland, Liv Kjersti; Mjøs, Svein A; Grung, Bjørn

2011-09-23

The retention behavior of components analyzed by chromatography varies with instrumental settings. Being able to predict how changes in these settings alter the elution pattern is useful, both with regards to component identification, as well as with regards to optimization of the chromatographic system. In this work, it is shown how experimental designs can be used for this purpose. Different experimental designs for response surface modeling of the separation of fatty acid methyl esters (FAME) as function of chromatographic conditions in GC have been evaluated. Full factorial, central composite, Doehlert and Box-Behnken designs were applied. A mixture of 38 FAMEs was separated on a polar cyanopropyl substituted polysilphenylene-siloxane phase capillary column. The temperature gradient, the start temperature of the gradient, and the carrier gas velocity were varied in the experiments. The modeled responses, as functions of chromatographic conditions, were retention time, retention indices, peak widths, separation efficiency and resolution between selected peak pairs. The designs that allowed inclusion of quadratic terms among the predictors performed significantly better than factorial design. Box-Behnken design provided the best results for prediction of retention, but the differences between the central composite, Doehlert and Box-Behnken designs were small. Retention indices could be modeled with much better accuracy than retention times. However, because the errors of predicted tR of closely eluting peaks were highly correlated, models of resolution (Rs) that were based on retention time had errors in the same range as corresponding models based on ECL. Copyright © 2011 Elsevier B.V. All rights reserved.

Investigation on imperfection sensitivity of composite cylindrical shells using the nonlinearity reduction technique and the polynomial chaos method

NASA Astrophysics Data System (ADS)

Liang, Ke; Sun, Qin; Liu, Xiaoran

2018-05-01

The theoretical buckling load of a perfect cylinder must be reduced by a knock-down factor to account for structural imperfections. The EU project DESICOS proposed a new robust design for imperfection-sensitive composite cylindrical shells using the combination of deterministic and stochastic simulations, however the high computational complexity seriously affects its wider application in aerospace structures design. In this paper, the nonlinearity reduction technique and the polynomial chaos method are implemented into the robust design process, to significantly lower computational costs. The modified Newton-type Koiter-Newton approach which largely reduces the number of degrees of freedom in the nonlinear finite element model, serves as the nonlinear buckling solver to trace the equilibrium paths of geometrically nonlinear structures efficiently. The non-intrusive polynomial chaos method provides the buckling load with an approximate chaos response surface with respect to imperfections and uses buckling solver codes as black boxes. A fast large-sample study can be applied using the approximate chaos response surface to achieve probability characteristics of buckling loads. The performance of the method in terms of reliability, accuracy and computational effort is demonstrated with an unstiffened CFRP cylinder.

Advanced numerical models and material characterisation techniques for composite materials subject to impact and shock wave loading

NASA Astrophysics Data System (ADS)

Clegg, R. A.; White, D. M.; Hayhurst, C.; Ridel, W.; Harwick, W.; Hiermaier, S.

2003-09-01

The development and validation of an advanced material model for orthotropic materials, such as fibre reinforced composites, is described. The model is specifically designed to facilitate the numerical simulation of impact and shock wave propagation through orthotropic materials and the prediction of subsequent material damage. Initial development of the model concentrated on correctly representing shock wave propagation in composite materials under high and hypervelocity impact conditions [1]. This work has now been extended to further concentrate on the development of improved numerical models and material characterisation techniques for the prediction of damage, including residual strength, in fibre reinforced composite materials. The work is focussed on Kevlar-epoxy however materials such as CFRP are also being considered. The paper describes our most recent activities in relation to the implementation of advanced material modelling options in this area. These enable refined non-liner directional characteristics of composite materials to be modelled, in addition to the correct thermodynamic response under shock wave loading. The numerical work is backed by an extensive experimental programme covering a wide range of static and dynamic tests to facilitate derivation of model input data and to validate the predicted material response. Finally, the capability of the developing composite material model is discussed in relation to a hypervelocity impact problem.

Chemical functionalization of graphene to augment stem cell osteogenesis and inhibit biofilm formation on polymer composites for orthopedic applications.

PubMed

Kumar, Sachin; Raj, Shammy; Kolanthai, Elayaraja; Sood, A K; Sampath, S; Chatterjee, Kaushik

2015-02-11

Toward designing the next generation of resorbable biomaterials for orthopedic applications, we studied poly(ε-caprolactone) (PCL) composites containing graphene. The role, if any, of the functionalization of graphene on mechanical properties, stem cell response, and biofilm formation was systematically evaluated. PCL composites of graphene oxide (GO), reduced GO (RGO), and amine-functionalized GO (AGO) were prepared at different filler contents (1%, 3%, and 5%). Although the addition of the nanoparticles to PCL markedly increased the storage modulus, this increase was largest for GO followed by AGO and RGO. In vitro cell studies revealed that the AGO and GO particles significantly increased human mesenchymal stem cell proliferation. AGO was most effective in augmenting stem cell osteogenesis leading to mineralization. Bacterial studies revealed that interaction with functionalized GO induced bacterial cell death because of membrane damage, which was further accentuated by amine groups in AGO. As a result, AGO composites were best at inhibiting biofilm formation. The synergistic effect of oxygen containing functional groups and amine groups on AGO imparts the optimal combination of improved modulus, favorable stem cell response, and biofilm inhibition in AGO-reinforced composites desired for orthopedic applications. This work elucidates the importance of chemical functionalization of graphene in polymer composites for biomedical applications.

Synergistic Effects among the Structure, Martensite Transformation and Shear Band in a Shape Memory Alloy-Metallic Glass Composite

NASA Astrophysics Data System (ADS)

Zhang, Xudong; Ren, Junqiang; Ding, Xiangdong

2018-05-01

In this work, we use the finite element method to investigate the free volume evolution, as well as the martensite transformation effect and its connection with the pretreatment strain, in a shape memory alloy-metallic glass composite. Our simulation results show that the martensite phase transformation can enhance the blocking effect while relieving the free volume localization. The synergistic effect among the martensite transformation effect, blocking effect, and shear band interaction in the composite is responsible for the tensile plasticity and work-hardening capability. In addition, we design a Sierpinski carpet-like fractal microstructure so that the composite exhibits improved tensile performance as a result of the enhanced synergistic effect. However, the tensile performance of the composite deteriorates with increasing pretreatment strain since the martensite transformation effect is weakened.

Theoretical modeling and design of photonic structures in zeolite nanocomposites for gas sensing. Part I: surface relief gratings.

PubMed

Cody, D; Naydenova, I

2017-12-01

The suitability of holographic structures fabricated in zeolite nanoparticle-polymer composite materials for gas sensing applications has been investigated. Theoretical modeling of the sensor response (i.e., change in hologram readout due to a change in refractive index modulation or thickness as a result of gas adsorption) of different sensor designs was carried out using Raman-Nath theory and Kogelnik's coupled wave theory. The influence of a range of parameters on the sensor response of holographically recorded surface and volume photonic grating structures has been studied, namely the phase difference between the diffracted and probe beam introduced by the grating, grating geometry, thickness, spatial frequency, reconstruction wavelength, and zeolite nanoparticle refractive index. From this, the optimum fabrication conditions for both surface and volume holographic gas sensor designs have been identified. Here, in part I, results from theoretical modeling of the influence of design on the sensor response of holographically inscribed surface relief structures for gas sensing applications is reported.

Carbon nanotube-based structural health monitoring for fiber reinforced composite materials

NASA Astrophysics Data System (ADS)

Liu, Hao; Liu, Kan; Mardirossian, Aris; Heider, Dirk; Thostenson, Erik

2017-04-01

In fiber reinforced composite materials, the modes of damage accumulation, ranging from microlevel to macro-level (matrix cracks development, fiber breakage, fiber-matrix de-bonding, delamination, etc.), are complex and hard to be detected through conventional non-destructive evaluation methods. Therefore, in order to assure the outstanding structural performance and high durability of the composites, there has been an urgent need for the design and fabrication smart composites with self-damage sensing capabilities. In recent years, the macroscopic forms of carbon nanotube materials have been maturely investigated, which provides the opportunity for structural health monitoring based on the carbon nanotubes that are integrated in the inter-laminar areas of advanced fiber composites. Here in this research, advanced fiber composites embedded with laminated carbon nanotube layers are manufactured for damage detection due to the relevant spatial electrical property changes once damage occurs. The mechanical-electrical coupling response is recorded and analyzed during impact test. The design and manufacturing of integrating the carbon nanotubes intensely affect the detecting sensitivity and repeatability of the integrated multifunctional sensors. The ultimate goal of the reported work is to develop a novel structural health monitoring method with the capability of reporting information on the damage state in a real-time way.

Multi response optimization of sheet forming of Kenaf-Polypropylene composites using grey based fuzzy algorithm

NASA Astrophysics Data System (ADS)

Oktariani, Erfina; Istikowati, Rita; Tomo, Hendro Sat Setijo; Rizal, Rafliansyah; Pratama, Yosea

2018-02-01

Composites from natural fiber reinforcement are developed as the alternative sheet materials of plastic composite for small-size bodywork parts in automotive industries. Kenaf fiber is selected as the reinforcement of plastic composite. Press forming of Kenaf-Polypropylene is experimentally produced in this study. The aim of this study is to obtain the optimal factor of the process of sheet forming of Kenaf-Polypropylene. The Kenaf delignified is cut into 5 cm lengths and distributed on the surface of Polypropylene sheet for 3 and 5 ply layers. The layers of Kenaf-Polypropylene then pressed by hot press at 190 and 210°C, 40 and 50 bar, for 3 and 5 minutes. However, there are limitations in handling multi responses in design of experiments. The application of the fuzzy logic theory to the grey relational analysis may further develop its performance in solving multi-response problems for process parameter optimization. The layer of Kenaf and Polypropylene, temperature, the duration of hot press and pressure are factors that affect the process. The result of experimental investigation and as well as analysis, shows that the best combination values were 3 ply layer, 210°C, 5 minutes of hot press and 50 bar.

Optimization of media composition for Nattokinase production by Bacillus subtilis using response surface methodology.

PubMed

Deepak, V; Kalishwaralal, K; Ramkumarpandian, S; Babu, S Venkatesh; Senthilkumar, S R; Sangiliyandi, G

2008-11-01

Response surface methodology and central composite rotary design (CCRD) was employed to optimize a fermentation medium for the production of Nattokinase by Bacillus subtilis at pH 7.5. The four variables involved in this study were Glucose, Peptone, CaCl2, and MgSO4. The statistical analysis of the results showed that, in the range studied; only peptone had a significant effect on Nattokinase production. The optimized medium containing (%) Glucose: 1, Peptone: 5.5, MgSO4: 0.2 and CaCl2: 0.5 resulted in 2-fold increased level of Nattokinase (3194.25U/ml) production compared to initial level (1599.09U/ml) after 10h of fermentation. Nattokinase production was checked with fibrinolytic activity.

Bovine Mammary Nutrigenomics and Changes in the Milk Composition due to Rapeseed or Sunflower Oil Supplementation of High-Forage or High-Concentrate Diets.

PubMed

Leroux, Christine; Bernard, Laurence; Faulconnier, Yannick; Rouel, Jacques; de la Foye, Anne; Domagalski, Jordann; Chilliard, Yves

2016-01-01

Fatty acid (FA) composition plays a crucial role in milk nutritional quality. Despite the known nutritional regulation of ruminant milk composition, the overall mammary mechanisms underlying this regulation are far from being understood. The aim of our study was to determine nutritional regulation of mammary transcriptomes in relation to the cow milk composition. Twelve cows received diets differing in the forage-to-concentrate ratio [high forage (HF) and low forage (LF)] supplemented or not with lipids [HF with whole intact rapeseeds (RS) and LF sunflower oil (SO)] in a 4 × 4 Latin square design. Milk production and FA composition were determined. The gene expression profile was studied using RT-qPCR and a bovine microarray. Our results showed a higher amplitude of milk composition and mammary transcriptome responses to lipid supplementation with the LF-SO compared with the LF diet than with the HF-RS compared with the HF diet. Forty-nine differentially expressed genes, including genes involved in lipid metabolism, were identified with LF-SO versus LF, whereas RS supplementation to the HF diet did not affect the mammary transcriptome. This study highlights different responses to lipid supplementation of milk production and composition and mammary transcriptomes depending on the nature of lipid supplementation and the percentage of dietary concentrate. © 2016 S. Karger AG, Basel.

Designing water supplies: Optimizing drinking water composition for maximum economic benefit.

PubMed

Rygaard, M; Arvin, E; Bath, A; Binning, P J

2011-06-01

It is possible to optimize drinking water composition based on a valuation of the impacts of changed water quality. This paper introduces a method for assessing the potential for designing an optimum drinking water composition by the use of membrane desalination and remineralization. The method includes modeling of possible water quality blends and an evaluation of corrosion indices. Based on concentration-response relationships a range of impacts on public health, material lifetimes and consumption of soap have been valued for Perth, Western Australia and Copenhagen, Denmark. In addition to water quality aspects, costs of water production, fresh water abstraction and CO(2)-emissions are integrated into a holistic economic assessment of the optimum share of desalinated water in water supplies. Results show that carefully designed desalination post-treatment can have net benefits up to €0.3 ± 0.2 per delivered m(3) for Perth and €0.4(±0.2) for Copenhagen. Costs of remineralization and green house gas emission mitigation are minor when compared to the potential benefits of an optimum water composition. Finally, a set of optimum water quality criteria is proposed for the guidance of water supply planning and management. Copyright © 2011 Elsevier Ltd. All rights reserved.

IER 203 CED-2 Report: LLNL Final Design for BERP Ball With a Composite Reflector of Thin Polyethylene Backed by Nickel

DOE Office of Scientific and Technical Information (OSTI.GOV)

Percher, C. M.; Heinrichs, D. P.; Kim, S. K.

2016-07-18

This report documents the results of final design (CED-2) for IER 203, BERP Ball Composite Reflection, and focuses on critical configurations with a 4.5 kg α-phase plutonium sphere reflected by a combination of thin high-density polyethylene (HDPE) backed by a thick nickel reflector. The Lawrence Livermore National Laboratory’s (LLNL’s) Nuclear Criticality Safety Division, in support of fissile material operations, calculated surprisingly reactive configurations when a fissile core was surrounded by a thin, moderating reflector backed by a thick metal reflector. These composite reflector configurations were much more reactive than either of the single reflector materials separately. The calculated findings havemore » resulted in a stricter-than-anticipated criticality control set, impacting programmatic work. IER 203 was requested in response to these seemingly anomalous calculations to see if the composite reflection effect could be shown experimentally. This report focuses on the Beryllium Reflected Plutonium (BERP) ball as a fissile material core reflected by polyethylene and nickel. A total of four critical configurations were designed as part of CED-2. Fabrication costs are estimated to be $98,500, largely due to the cost of the large nickel reflectors. The IER 203 experiments could reasonably be expected to begin in early FY2017.« less

Investigation of fragrance stability used in the formulation of cosmetic and hygienic products using headspace solid-phase microextraction by nanostructured materials followed by gas chromatography with mass spectrometry.

PubMed

Masoum, Saeed; Gholami, Ali; Ghaheri, Salehe; Bouveresse, Delphine Jouan-Rimbaud; Cordella, Christophe B Y; Rutledge, Douglas N

2016-07-01

A new composite coating of polypyrrole and sodium lauryl ether sulfate was electrochemically prepared on a stainless-steel wire using cyclic voltammetry. The application and performance of the fiber was evaluated for the headspace solid-phase microextraction of a fragrance in aqueous bleach samples followed by gas chromatography combined with mass spectrometry to assess the fragrance stability in this kind of household cleaning product. To obtain a stable and efficient composite coating, parameters related to the coating process such as scan rate and numbers of cycles were optimized using a central composite design. In addition, the effects of various parameters on the extraction efficiency of the headspace solid-phase microextraction process such as extraction temperature and time, ionic strength, sample volume, and stirring rate were investigated by experimental design methods using Plackett-Burman and Doehlert designs. The optimum values of 53°C and 28 min for sample temperature and time, respectively, were found through response surface methodology. Results show that the combination of polypyrrole and sodium lauryl ether sulfate in a composite form presents desirable opportunities to produce new materials to study fragrance stability by headspace solid-phase microextraction. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Optimization of extraction parameters of pentacyclic triterpenoids from Swertia chirata stem using response surface methodology.

PubMed

Pandey, Devendra Kumar; Kaur, Prabhjot

2018-03-01

In the present investigation, pentacyclic triterpenoids were extracted from different parts of Swertia chirata by solid-liquid reflux extraction methods. The total pentacyclic triterpenoids (UA, OA, and BA) in extracted samples were determined by HPTLC method. Preliminary studies showed that stem part contains the maximum pentacyclic triterpenoid and was chosen for further studies. Response surface methodology (RSM) has been employed successfully by solid-liquid reflux extraction methods for the optimization of different extraction variables viz., temperature ( X 1 35-70 °C), extraction time ( X 2 30-60 min), solvent composition ( X 3 20-80%), solvent-to-solid ratio ( X 4 30-60 mlg -1 ), and particle size ( X 5 3-6 mm) on maximum recovery of triterpenoid from stem parts of Swertia chirata . A Plackett-Burman design has been used initially to screen out the three extraction factors viz., particle size, temperature, and solvent composition on yield of triterpenoid. Moreover, central composite design (CCD) was implemented to optimize the significant extraction parameters for maximum triterpenoid yield. Three extraction parameters viz., mean particle size (3 mm), temperature (65 °C), and methanol-ethyl acetate solvent composition (45%) can be considered as significant for the better yield of triterpenoid A second-order polynomial model satisfactorily fitted the experimental data with the R 2 values of 0.98 for the triterpenoid yield ( p  < 0.001), implying good agreement between the experimental triterpenoid yield (3.71%) to the predicted value (3.79%).

A new method for achieving enhanced dielectric response over a wide temperature range

DOE PAGES

Maurya, Deepam; Sun, Fu -Chang; Pamir Alpay, S.; ...

2015-10-19

We report a novel approach for achieving high dielectric response over a wide temperature range. In this approach, multilayer ceramic heterostructures with constituent compositions having strategically tuned Curie points (TC) were designed and integrated with varying electrical connectivity. Interestingly, these multilayer structures exhibited different dielectric behavior in series and parallel configuration due to variations in electrical boundary conditions resulting in the differences in the strength of the electrostatic coupling. The results are explained using nonlinear thermodynamic model taking into account electrostatic interlayer interaction. We believe that present work will have huge significance in design of high performance ceramic capacitors.

A new method for achieving enhanced dielectric response over a wide temperature range

PubMed Central

Maurya, Deepam; Sun, Fu-Chang; Pamir Alpay, S.; Priya, Shashank

2015-01-01

We report a novel approach for achieving high dielectric response over a wide temperature range. In this approach, multilayer ceramic heterostructures with constituent compositions having strategically tuned Curie points (TC) were designed and integrated with varying electrical connectivity. Interestingly, these multilayer structures exhibited different dielectric behavior in series and parallel configuration due to variations in electrical boundary conditions resulting in the differences in the strength of the electrostatic coupling. The results are explained using nonlinear thermodynamic model taking into account electrostatic interlayer interaction. We believe that present work will have huge significance in design of high performance ceramic capacitors. PMID:26477391

DOE Office of Scientific and Technical Information (OSTI.GOV)

Brown, Alexander; Jernigan, Dann A.; Dodd, Amanda B.

New aircraft are being designed with increasing quantities of composite materials used in their construction. Different from the more traditional metals, composites have a higher propensity to burn. This presents a challenge to transportation safety analyses, as the aircraft structure now represents an additional fuel source involved in the fire scenario. Most of the historical fire testing of composite materials is aime d at studying kinetics, flammability or yield strength under fire conditions. Most of this testing is small - scale. Heterogeneous reactions are often length - scale dependent, and this is thought to be particularly true for composites whichmore » exhibit signific ant microscopic dynamics that can affect macro - scale behavior. We have designed a series of tests to evaluate composite materials under various structural loading conditions with a consistent thermal condition. We have measured mass - loss , heat flux, and temperature throughout the experiments. Several types of panels have been tested, including simple composite panels, and sandwich panels. The main objective of the testing was to understand the importance of the structural loading on a composite to its b ehavior in response to fire - like conditions. During flaming combustion at early times, there are some features of the panel decomposition that are unique to the type of loading imposed on the panels. At load levels tested, fiber reaction rates at later t imes appear to be independent of the initial structural loading.« less

Classes of Split-Plot Response Surface Designs for Equivalent Estimation

NASA Technical Reports Server (NTRS)

Parker, Peter A.; Kowalski, Scott M.; Vining, G. Geoffrey

2006-01-01

When planning an experimental investigation, we are frequently faced with factors that are difficult or time consuming to manipulate, thereby making complete randomization impractical. A split-plot structure differentiates between the experimental units associated with these hard-to-change factors and others that are relatively easy-to-change and provides an efficient strategy that integrates the restrictions imposed by the experimental apparatus. Several industrial and scientific examples are presented to illustrate design considerations encountered in the restricted randomization context. In this paper, we propose classes of split-plot response designs that provide an intuitive and natural extension from the completely randomized context. For these designs, the ordinary least squares estimates of the model are equivalent to the generalized least squares estimates. This property provides best linear unbiased estimators and simplifies model estimation. The design conditions that allow for equivalent estimation are presented enabling design construction strategies to transform completely randomized Box-Behnken, equiradial, and small composite designs into a split-plot structure.

CREATIVE LANGUAGE EXPERIENCES IN THE HIGH SCHOOL.

ERIC Educational Resources Information Center

SHERIDAN, MARION C.

THE ENGLISH TEACHER CAN ROUSE STUDENTS OUT OF UNTHINKING ACCEPTANCE AND PASSIVITY BY PROVIDING THEM WITH CREATIVE LANGUAGE EXPERIENCES DESIGNED TO SHAPE THEM INTO CURIOUS AND RESPONSIVE INDIVIDUALS. TO FIND A PERSPECTIVE ON TEACHING CREATIVELY THE MANY FACETS OF LANGUAGE, LITERATURE, AND COMPOSITION, TEACHERS SHOULD LOOK TO STATEMENTS MADE BY…

Assessment Feedback Using Screencapture Technology in Political Science

ERIC Educational Resources Information Center

Anson, Ian G.

2015-01-01

This article serves to introduce a new technology for student feedback on written assignments to political scientists. Developed in the field of composition studies, screencapture commentary is a novel technique designed to provide audiovisual responses to student writing. To receive feedback, students watch a recorded video of the instructor's…

The effect of interference on delta modulation encoded video signals

NASA Technical Reports Server (NTRS)

Schilling, D. L.

1979-01-01

An adaptive delta modulator which encodes composite color video signals was shown to provide a good response when operating at 16 Mb/s and near-commercial quality at 23Mb/s. The ADM was relatively immune to channel errors. The system design is discussed and circuit diagrams are included.

Optimization of extraction process by response surface methodology and preliminary structural analysis of polysaccharides from defatted peanut (Arachis hypogaea) cakes.

PubMed

Song, Yi; Du, Bingjian; Zhou, Ting; Han, Bing; Yu, Fei; Yang, Rui; Hu, Xiaosong; Ni, Yuanying; Li, Quanhong

2011-02-01

In this work, response surface methodology was used to determine optimum conditions for extraction of polysaccharides from defatted peanut cake. A central composite design including independent variables, such as extraction temperature (x(1)), extraction time (x(2)), and ethanol concentration (x(3)) was used. Selected response which evaluates the extraction process was polysaccharide yield, and the second-order model obtained for polysaccharide yield revealed coefficient of determination of 97.81%. The independent variable with the largest effect on response was ethanol concentration (x(3)). The optimum extraction conditions were found to be extraction temperature 48.7°C, extraction time 1.52 h, and ethanol concentration of 61.9% (v/v), respectively. Under these conditions, the extraction efficiency of polysaccharide can increase to 25.89%. The results of structural analysis showed that the main composition of defatted peanut cake polysaccharide was α-galactose. 2010 Elsevier Ltd. All rights reserved.

Tribological properties and lubrication mechanism of in situ graphene-nickel matrix composite impregnated with lubricating oil

NASA Astrophysics Data System (ADS)

Lei, Yu; Du, Jinfang; Pang, Xianjuan; Wang, Haizhong; Yang, Hua; Jiang, Jinlong

2018-05-01

A solid-liquid synergetic lubricating system has been designed to develop a novel self-lubricating nickel matrix composite. The graphene-nickel (G-Ni) matrix composite with porous structure was fabricated by in situ growing graphene in bulk nickel using a powder metallurgy method. The porous structures of the composite were used to store polyalphaolefin (PAO) oil for self-lubricating. It is found that the G-Ni matrix composite under oil lubrication condition exhibited superior tribological properties as compared to pure nickel and the composite under dry sliding condition. The prestored oil was released from pores to the sliding surface forming a lubricating oil film during friction process. This lubricating oil film can protect the worn surface from severe oxidation, and help the formation and transfer of a carbon-based solid tribofilm derived from graphene and lubricating oil. This solid (graphene)-liquid (oil) synergistic lubricating mechanism is responsible for the reduction of friction coefficient and improvement of wear resistance of the in situ fabricated G-Ni matrix composite.

A New Local Debonding Model with Application to the Transverse Tensile and Creep Behavior of Continuously Reinforced Titanium Composites

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2000-01-01

A new, widely applicable model for local interfacial debonding in composite materials is presented. Unlike its direct predecessors, the new model allows debonding to progress via unloading of interfacial stresses even as global loading of the composite continues. Previous debonding models employed for analysis of titanium matrix composites are surpassed by the accuracy, simplicity, and efficiency demonstrated by the new model. The new model was designed to operate seamlessly within NASA Glenn's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC), which was employed to simulate the time- and rate-dependent (viscoplastic) transverse tensile and creep behavior of SiC/Ti composites. MAC/GMC's ability to simulate the transverse behavior of titanium matrix composites has been significantly improved by the new debonding model. Further, results indicate the need for a more accurate constitutive representation of the titanium matrix behavior in order to enable predictions of the composite transverse response, without resorting to recalibration of the debonding model parameters.

Thermo-viscoelastic analysis of composite materials, volume 1

NASA Technical Reports Server (NTRS)

Lin, K. Y.; Hwang, I. H.

1988-01-01

Advanced composite materials, especially graphite/epoxy, are being applied to aircraft structures in order to improve performance and save weight. An important consideration in composite design is the residual strength of a structure containing holes, delaminations, or interlaminar damage when subjected to compressive loads. Recent studies have revealed the importance of viscoelastic effects in polymer-based composites. The viscoelastic effect is particularly significant at elevated temperature/moisture conditions since the matrix material is strongly affected by the environment. The solution of viscoelastic problems in composites was limited to special cases which can be solved by classical lamination theory. A finite element procedure is presented for calculating time-dependent stresses and strains in composite structures with general configurations and complicated boundary conditions. Using this procedure the in-plane and interlaminar stress distributions and histories in notched and unnotched composites were obtained for mechanical and thermal loads. Both two-dimensional and three-dimensional viscoelastic problems are analyzed. The effects of layup orientation and load spectrum on creep response and stress relaxation were also studied.

Bioinspired Design of Polycaprolactone Composite Nanofibers as Artificial Bone Extracellular Matrix for Bone Regeneration Application.

PubMed

Gao, Xiang; Song, Jinlin; Zhang, Yancong; Xu, Xiao; Zhang, Siqi; Ji, Ping; Wei, Shicheng

2016-10-07

The design and development of functional biomimetic systems for programmed stem cell response is a field of topical interest. To mimic bone extracellular matrix, we present an innovative strategy for constructing drug-loaded composite nanofibrous scaffolds in this study, which could integrate multiple cues from calcium phosphate mineral, bioactive molecule, and highly ordered fiber topography for the control of stem cell fate. Briefly, inspired by mussel adhesion mechanism, a polydopamine (pDA)-templated nanohydroxyapatite (tHA) was synthesized and then surface-functionalized with bone morphogenetic protein-7-derived peptides via catechol chemistry. Afterward, the resulting peptide-loaded tHA (tHA/pep) particles were blended with polycaprolactone (PCL) solution to fabricate electrospun hybrid nanofibers with random and aligned orientation. Our research demonstrated that the bioactivity of grafted peptides was retained in composite nanofibers. Compared to controls, PCL-tHA/pep composite nanofibers showed improved cytocompatibility. Moreover, the incorporated tHA/pep particles in nanofibers could further facilitate osteogenic differentiation potential of human mesenchymal stem cells (hMSCs). More importantly, the aligned PCL-tHA/pep composite nanofibers showed more osteogenic activity than did randomly oriented counterparts, even under nonosteoinductive conditions, indicating excellent performance of biomimetic design in cell fate decision. After in vivo implantation, the PCL-tHA/pep composite nanofibers with highly ordered structure could significantly promote the regeneration of lamellar-like bones in a rat calvarial critical-sized defect. Accordingly, the presented strategy in our work could be applied for a wide range of potential applications in not only bone regeneration application but also pharmaceutical science.

Structural Performance of a Compressively Loaded Foam-Core Hat-Stiffened Textile Composite Panel

NASA Technical Reports Server (NTRS)

Ambur, Damodar R.; Dexter, Benson H.

1996-01-01

A structurally efficient hat-stiffened panel concept that utilizes a structural foam as a stiffener core material has been designed and developed for aircraft primary structural applications. This stiffener concept is fabricated from textile composite material forms with a resin transfer molding process. This foam-filled hat-stiffener concept is structurally more efficient than most other prismatically stiffened panel configurations in a load range that is typical for both fuselage and wing structures. The panel design is based on woven/stitched and braided graphite-fiber textile preforms, an epoxy resin system, and Rohacell foam core. The structural response of this panel design was evaluated for its buckling and postbuckling behavior with and without low-speed impact damage. The results from single-stiffener and multi-stiffener specimen tests suggest that this structural concept responds to loading as anticipated and has excellent damage tolerance characteristics compared to a similar panel design made from preimpregnated graphite-epoxy tape material.

Composite Structures Materials Testing for the Orion Crew Vehicle Heat Shield

NASA Technical Reports Server (NTRS)

Khemani, Farah N.

2011-01-01

As research is being performed for the new heat shield for the Orion capsule, National Aeronautics and Space Administration (NASA) is developing the first composite heat shield. As an intern of the Structures Branch in the Engineering Directorate (ES 2), my main task was to set up a test plan to determine the material properties of the honeycomb that will be used on the Orion Crew Module heat shield to verify that the composite is suitable for the capsule. Before conducting composite shell tests, which are performed to simulate the crush performance of the heat shield on the capsule, it is necessary to determine the compression and shear properties of the composite used on the shell. During this internship, I was responsible for developing a test plan, designing parts for the test fixtures as well as getting them fabricated for the honeycomb shear and compression testing. This involved work in Pro/Engineer as well as coordinating with Fab Express, the Building 9 Composite Shop and the Structures Test Laboratory (STL). The research and work executed for this project will be used for composite sandwich panel testing in the future as well. As a part of the Structures Branch, my main focus was to research composite structures. This involves system engineering and integration (SE&I) integration, manufacturing, and preliminary testing. The procedures for these projects that were executed during this internship included design work, conducting tests and performing analysis.

Extensional ionomeric polymer conductor composite actuators with ionic liquids

NASA Astrophysics Data System (ADS)

Liu, Sheng; Lin, Minren; Zhang, Qiming

2008-03-01

Although the Ionic Polymer-Metal Composite (IPMC) actuators developed up to date are in the form of bending actuators, development of extensional actuators based on IMPC is highly desirable from practical applications and fundamental understanding points of view. This talk presents the design, fabrication and characterization of a recent work on an extensional Ionic Polymer-Metal Composite actuator. The extensional actuator consists of the Nafion ionomer as the matrix and the sub-micron size RuO II particles as the conductive filler for the conductor/ionomr composites. In this investigation, several ionic liquids (IL) were investigated. For a Nafion/RuO II composite with 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate (EMI-Tf) IL, it was found that as the ions are driven into the ionomer/RuO II composite (the composite under negative voltage), an extensional strain of 0.9% was observed; while as the ions were expelled from the ionomer/RuO II composite (under positive voltage), a contraction of -1.2% was observed. The results indicate that multiple ions are participating in charge transport and actuation process. In this paper, we also discuss several design considerations for future extensional actuators with fast response, much improved strain and stress level. Especially an actuator based on multilayer configuration can significantly increase the electric field level in the actuator and consequently significantly improve the actuator speed. The extensional actuator investigated here provides a unique platform to investigate various phenomena related to ion transport and their interaction with the ionomer/conductor matrix to realize high electromechanical performance.

Process and assembly plans for low cost commercial fuselage structure

NASA Technical Reports Server (NTRS)

Willden, Kurtis; Metschan, Stephen; Starkey, Val

1991-01-01

Cost and weight reduction for a composite structure is a result of selecting design concepts that can be built using efficient low cost manufacturing and assembly processes. Since design and manufacturing are inherently cost dependent, concurrent engineering in the form of a Design-Build Team (DBT) is essential for low cost designs. Detailed cost analysis from DBT designs and hardware verification must be performed to identify the cost drivers and relationships between design and manufacturing processes. Results from the global evaluation are used to quantitatively rank design, identify cost centers for higher ranking design concepts, define and prioritize a list of technical/economic issues and barriers, and identify parameters that control concept response. These results are then used for final design optimization.

Composite Fuselage Technology

NASA Technical Reports Server (NTRS)

Lagace, Paul A.

1999-01-01

Work was conducted over a ten-year period to address the central issue of damage in primary load-bearing aircraft composite structure, specifically fuselage structure. This included the three facets of damage resistance, damage tolerance, and damage arrest. Experimental, analytical, and numerical work was conducted in order to identify and better understand the mechanisms that control the structural behavior of fuselage structures in their response to the three aspects of damage. Furthermore, work was done to develop straightforward design methodologies that can be employed by structural designers in preliminary design stages to make intelligent choices concerning the material, layup, and structural configurations so that a more efficient structure with structural integrity can be designed and built. Considerable progress was made towards achieving these goals via this work. In regard to damage tolerance considerations, the following were identified as important effects: composite layup and associated orthotropy/structural anisotropy, specifics of initial local damage mechanisms, role of longitudinal versus hoop stress, and large deformation and associated geometric nonlinearity. Means were established to account for effects of radius and for the nonlinear response. In particular, nondimensional parameters were identified to characterize the importance of nonlinearity in the response of pressurized cylinders. This led to the establishment of a iso-nonlinear-error plot for reference in structural design. Finally, in the case of damage tolerance, the general approach of the original methodology to predict the failure pressure involving extending basic plate failure data by accounting for the local stress intensification was accomplished for the general case by accounting for the mechanisms noted by utilizing the capability of the STAGS finite element code and numerically calculating the local stress intensification for the particular configuration to be considered. For the issue of damage arrest, placement of and configuration of stiffeners (including stiffener curvature), and magnitude and orientation of principal strains due to local bending were found to be key considerations. Means were established to account for stiffener effectiveness quantitatively based on radius, slit size, stiffener curvature' and relative bending stifffiesses involved. Geometric nonlinearity was also found to play an - 24 - important role here. Furthermore, it was determined that damage propagation is controlled by different mechanisms (hoop stress versus flapping stress and the associated factors involved in each) depending upon the direction of damage propagation. This latter item results in an inability to scale these phenomena in one test due to the different factors involved. Finally, the importance of shell curvature and associated instability in response to transverse loading including impact were found to be important considerations in damage resistance. A technique, involving asymmetric meshing of a finite element mesh, was developed to predict this behavior and showed excellent correlation with experimental results. Further details of these ten years of work are presented herein with references made to the fourteen documents produced during this work where full details can be found. Implications of this work are discussed and recommendations made. Although it is clear that there is more work to be done to fully understand composite fuselage technology and specifically the overall issue of damage in primary load-bearing composite structures, important understanding and capability has been extended via this work.

Experimental and simulation study of flexural behaviour of woven Glass/Epoxy laminated composite plate

NASA Astrophysics Data System (ADS)

Sahoo, Sushree S.; Singh, Vijay K.; Panda, Subrata K.

2015-02-01

Flexural behaviour of cross ply laminated woven Glass/Epoxy composite plate has been investigated in this article. Flexural responses are examined by a three point bend test and tensile test carried out on INSTRON 5967 and Universal Testing Machine INSTRON 1195 respectively. The finite element model is developed in ANSYS parametric design language code and discretised using an eight nodded structural shell element. Convergence behaviour of the simulation result has been performed and validated by comparing the results with experimental values. The effects of various parameters such as side-to-thickness ratio, modular ratio on flexural behaviour of woven Glass/Epoxy laminated composite plate are discussed in details.

Technology of civil usage of composites. [in commercial aircraft structures

NASA Technical Reports Server (NTRS)

Kemp, D. E.

1977-01-01

The paper deals with the use of advanced composites in structural components of commercial aircraft. The need for testing the response of a material system to service environment is discussed along with methods for evaluating design and manufacturing aspects of a built-up structure under environmental conditions and fail-safe (damage-tolerance) evaluation of structures. Crashworthiness aspects, the fire-hazard potential, and electrical damage of composite structures are considered. Practical operational experience with commercial aircraft is reviewed for boron/epoxy foreflaps, Kevlar/epoxy fillets and fairings, graphite/epoxy spoilers, graphite/polysulfone spoilers, graphite/epoxy floor posts, boron/aluminum aft pylon skin panels, graphite/epoxy engine nose cowl outer barrels, and graphite/epoxy upper aft rudder segments.

Neutrophils dominate the immune cell composition in non-small cell lung cancer. | Office of Cancer Genomics

Cancer.gov

The response rate to immune checkpoint inhibitor therapy for non-small-cell lung cancer (NSCLC) is just 20%. To improve this figure, several early phase clinical trials combining novel immunotherapeutics with immune checkpoint blockade have been initiated. Unfortunately, these trials have been designed without a strong foundational knowledge of the immune landscape present in NSCLC. Here, we use a flow cytometry panel capable of measuring 51 immune cell populations to comprehensively identify the immune cell composition and function in NSCLC.

Formulation development and optimization of a novel Cremophore EL-based nanoemulsion using ultrasound cavitation.

PubMed

Tang, Siah Ying; Manickam, Sivakumar; Wei, Tan Khang; Nashiru, Billa

2012-03-01

In the present study, response surface methodology (RSM) based on central composite design (CCD) was employed to investigate the influence of main emulsion composition variables, namely drug loading, oil content, emulsifier content as well as the effect of the ultrasonic operating parameters such as pre-mixing time, ultrasonic amplitude, and irradiation time on the properties of aspirin-loaded nanoemulsions. The two main emulsion properties studied as response variables were: mean droplet size and polydispersity index. The ultimate goal of the present work was to determine the optimum level of the six independent variables in which an optimal aspirin nanoemulsion with desirable properties could be produced. The response surface analysis results clearly showed that the variability of two responses could be depicted as a linear function of the content of main emulsion compositions and ultrasonic processing variables. In the present investigation, it is evidently shown that ultrasound cavitation is a powerful yet promising approach in the controlled production of aspirin nanoemulsions with smaller average droplet size in a range of 200-300 nm and with a polydispersity index (PDI) of about 0.30. This study proved that the use of low frequency ultrasound is of considerable importance in the controlled production of pharmaceutical nanoemulsions in the drug delivery system. Copyright © 2011 Elsevier B.V. All rights reserved.

Teaching the placement of posterior resin-based composite restorations in Spanish dental schools.

PubMed

Castillo-de Oyagüe, Raquel; Lynch, Christopher; McConnell, Robert; Wilson, Nairn

2012-07-01

In an area of esthetic dentistry such as posterior composites, in which new materials and techniques are being devolved continuously, it is important to confirm that dental students have a clear understanding of the basic principles of clinical application of this knowledge. Considering that the preparation of dental graduates in Spain may be of interest to competent dental authorities and employers with whom they can work worldwide, this study investigated the teaching of posterior composite restorations in Spanish dental schools. In late 2009⁄ early 2010, a questionnaire seeking information on the teaching of posterior composites was emailed to the professor responsible for teaching operative dentistry in each of the fifteen dental schools having complete undergraduate dental degree programmes in Spain. The response rate was 100%. Most investigated topics did not show noteworthy differences depending on whether the schools were public or private. Variations were found among Spanish dental schools in both the amount and content of the teaching programmes concerning posterior composite restorations. Differences were recorded in the teaching of cavity design, contraindications to composite placement, indications for liners and bases, matrix and wedging techniques, composite and bonding systems, light curing and finishing procedures for composite restorations. More consistency was observed in teaching methods of moisture-control, indirect composites and amalgam bonding. As recommended in previous surveyed countries, efforts must be made to promote harmonization of dental curricula to make it easier for graduates to work elsewhere, and to ensure they meet the needs of their patients on entering independent practice.

Behavior and Milk Yield Responses of Dairy Cattle to Simulated Jet Aircraft Noise.

DTIC Science & Technology

1992-01-01

dairy cows and release of prolactin (Prl) and Cortisol (Gc) in response to the milking stimuli. Thirty-six lactating Holstein dairy cows were...assigned to experiment when between 79 and 155 days in milk (DIM). Experiment was an incomplete block design with three treatments. Cows were... Cows were exposed to noise on 10-12 d/period with a frequency of 1-4 times/d. Milk yields, milk composition and residual milk were measured

Mechanical response of thick laminated beams and plates subject to out-of-plane loading

NASA Technical Reports Server (NTRS)

Hiel, C. C.; Brinson, . F.

1989-01-01

The use of simplified elasticity solutions to determine the mechanical response of thick laminated beams and plates subject to out-of-plane loading is demonstrated. Excellent results were obtained which compare favorably with theoretical, numerical and experimental analyses from other sources. The most important characteristic of the solution methodology presented is that it combines great mathematical precision with simplicity. This symbiosis has been needed for design with advanced composite materials.

Simulating the Impact Response of Composite Airframe Components

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Littell, Justin D.; Fasanella, Edwin L.

2014-01-01

In 2010, NASA Langley Research Center obtained residual hardware from the US Army's Survivable Affordable Repairable Airframe Program (SARAP). The hardware consisted of a composite fuselage section that was representative of the center section of a Black Hawk helicopter. The section was fabricated by Sikorsky Aircraft Corporation and designated the Test Validation Article (TVA). The TVA was subjected to a vertical drop test in 2008 to evaluate a tilting roof concept to limit the intrusion of overhead mass items, such as the rotor transmission, into the fuselage cabin. As a result of the 2008 test, damage to the hardware was limited primarily to the roof. Consequently, when the post-test article was obtained in 2010, the roof area was removed and the remaining structure was cut into six different types of test specimens including: (1) tension and compression coupons for material property characterization, (2) I-beam sections, (3) T-sections, (4) cruciform sections, (5) a large subfloor section, and (6) a forward framed fuselage section. In 2011, NASA and Sikorsky entered into a cooperative research agreement to study the impact responses of composite airframe structures and to evaluate the capabilities of the explicit transient dynamic finite element code, LS-DYNA®, to simulate these responses including damage initiation and progressive failure. Finite element models of the composite specimens were developed and impact simulations were performed. The properties of the composite material were represented using both a progressive in-plane damage model (Mat 54) and a continuum damage mechanics model (Mat 58) in LS-DYNA. This paper provides test-analysis comparisons of time history responses and the location and type of damage for representative I-beam, T-section, and cruciform section components.

Investigation of the Leak Response of a Carbon-Fiber Laminate Loaded in Biaxial Tension

NASA Technical Reports Server (NTRS)

Jackson, Wade C.; Ratcliffe, James G.

2013-01-01

Designers of pressurized structures have been reluctant to use composite materials because of concerns over leakage. Biaxial stress states are expected to be the worst-case loading condition for allowing leakage to occur through microcracks. To investigate the leakage behavior under in-plane biaxial loading, a cruciform composite specimen was designed that would have a relatively large test section with a uniform 1:1 biaxial loading ratio. A 7.6-cm-square test section was desired for future investigations of the leakage response as a result of impact damage. Many iterations of the cruciform specimen were evaluated using finite element analysis to reduce stress concentrations and maximize the size of the uniform biaxial strain field. The final design allowed the specimen to go to relatively high biaxial strain levels without incurring damage away from the test section. The specimen was designed and manufactured using carbon/epoxy fabric with a four-ply-thick, quasi-isotropic, central test section. Initial validation and testing were performed on a specimen without impact damage. The specimen was tested to maximum biaxial strains of approximately 4500micro epsilon without apparent damage. A leak measurement system containing a pressurized cavity was clamped to the test section and used to measure the flow rate through the specimen. The leakage behavior of the specimen was investigated for pressure differences up to 172 kPa

A liquid metal-based structurally embedded vascular antenna: I. Concept and multiphysical modeling

NASA Astrophysics Data System (ADS)

Hartl, D. J.; Frank, G. J.; Huff, G. H.; Baur, J. W.

2017-02-01

This work proposes a new concept for a reconfigurable structurally embedded vascular antenna (SEVA). The work builds on ongoing research of structurally embedded microvascular systems in laminated structures for thermal transport and self-healing and on studies of non-toxic liquid metals for reconfigurable electronics. In the example design, liquid metal-filled channels in a laminated composite act as radiating elements for a high-power planar zig-zag wire log periodic dipole antenna. Flow of liquid metal through the channels is used to limit the temperature of the composite in which the antenna is embedded. A multiphysics engineering model of the transmitting antenna is formulated that couples the electromagnetic, fluid, thermal, and mechanical responses. In part 1 of this two-part work, it is shown that the liquid metal antenna is highly reconfigurable in terms of its electromagnetic response and that dissipated thermal energy generated during high power operation can be offset by the action of circulating or cyclically replacing the liquid metal such that heat is continuously removed from the system. In fact, the SEVA can potentially outperform traditional copper-based antennas in high-power operational configurations. The coupled engineering model is implemented in an automated framework and a design of experiment study is performed to quantify first-order design trade-offs in this multifunctional structure. More rigorous design optimization is addressed in part 2.

Multi-material composites prepared by additive manufacturing and melt casting

NASA Astrophysics Data System (ADS)

Murialdo, Maxwell; Sullivan, Kyle; White, Bradley; LLNL MSD Collaboration

2017-06-01

Recent advances in additive manufacturing have disrupted not only means of production, but also have enabled a new parameter space of multiscale materials designs. Understanding the role of architecture to control material response is being investigated for a wide range of applications, from light-weight structural components to energetic materials. In this work, we combine 3D printing of scaffold structures with a subsequent melt-infiltration step to render an architected multi-material composite article. Both the scaffold architecture and material type were investigated. The processing challenges of filling such scaffolds using a melt-infiltration step will be discussed, along with our progress in this area. Using the combined method of printing and casting, we will discuss our path forward for testing the mechanical properties and the high-strain response of our composite architected parts. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. IM release: LLNL-ABS-725497-DRAFT.

Biodegradable composite scaffolds: a strategy to modulate stem cell behaviour.

PubMed

Armentano, Ilaria; Fortunati, Elena; Mattioli, Samantha; Rescignano, Nicolatta; Kenny, José M

2013-04-01

The application of new biomaterial technologies offers the potential to direct the stem cell fate, targeting the delivery of cells and reducing immune rejection, thereby supporting the development of regenerative medicine. Cells respond to their surrounding structure and with nanostructures exhibit unique proliferative and differentiation properties. This review presents the relevance, the promising perspectives and challenges of current biodegradable composite scaffolds in terms of material properties, processing technology and surface modification, focusing on significant recent patents in these fields. It has been reported how biodegradable porous composite scaffolds can be engineered with initial properties that reproduce the anisotropy, viscoelasticity, tension-compression non-linearity of different tissues by introducing specific nanostructures. Moreover the modulation of electrical, morphological, surface and topographic scaffold properties enables specific stem cell response. Recent advances in nanotechnology have allowed to engineer novel biomaterials with these complexity levels. Understanding the specific biological response triggered by various aspects of the fibrous environment is important in guiding the design and engineering of novel substrates that mimic the native cell matrix interactions in vivo.

Characterization of the Acoustic Radiation Properties of Laminated and Sandwich Composite Panels in Thermal Environment

NASA Astrophysics Data System (ADS)

Sharma, Nitin; Ranjan Mahapatra, Trupti; Panda, Subrata Kumar; Sahu, Pruthwiraj

2018-03-01

In this article, the acoustic radiation characteristics of laminated and sandwich composite spherical panels subjected to harmonic point excitation under thermal environment are investigated. The finite element (FE) simulation model of the vibrating panel structure is developed in ANSYS using ANSYS parametric design language (APDL) code. Initially, the critical buckling temperatures of the considered structures are obtained and the temperature loads are assorted accordingly. Then, the modal analysis of the thermally stressed panels is performed and the thermo-elastic free vibration responses so obtained are validated with the benchmark solutions. Subsequently, an indirect boundary element (BE) method is utilized to conduct a coupled FE-BE analysis to compute the sound radiation properties of panel structure. The agreement of the present sound power responses with the existing results available in the published literature establishes the validity of the proposed scheme. Finally, the current standardised scheme is extended to solve several numerical examples to bring out the influence of various parameters on the thermo-acoustic characteristics of laminated composite panels.

Optimization and characterization of liposome formulation by mixture design.

PubMed

Maherani, Behnoush; Arab-tehrany, Elmira; Kheirolomoom, Azadeh; Reshetov, Vadzim; Stebe, Marie José; Linder, Michel

2012-02-07

This study presents the application of the mixture design technique to develop an optimal liposome formulation by using the different lipids in type and percentage (DOPC, POPC and DPPC) in liposome composition. Ten lipid mixtures were generated by the simplex-centroid design technique and liposomes were prepared by the extrusion method. Liposomes were characterized with respect to size, phase transition temperature, ζ-potential, lamellarity, fluidity and efficiency in loading calcein. The results were then applied to estimate the coefficients of mixture design model and to find the optimal lipid composition with improved entrapment efficiency, size, transition temperature, fluidity and ζ-potential of liposomes. The response optimization of experiments was the liposome formulation with DOPC: 46%, POPC: 12% and DPPC: 42%. The optimal liposome formulation had an average diameter of 127.5 nm, a phase-transition temperature of 11.43 °C, a ζ-potential of -7.24 mV, fluidity (1/P)(TMA-DPH)((¬)) value of 2.87 and an encapsulation efficiency of 20.24%. The experimental results of characterization of optimal liposome formulation were in good agreement with those predicted by the mixture design technique.

Evaluation of a Singular Value Decomposition Approach for Impact Dynamic Data Correlation

NASA Technical Reports Server (NTRS)

Horta, Lucas G.; Lyle, Karen H.; Lessard, Wendy B.

2003-01-01

Impact dynamic tests are used in the automobile and aircraft industries to assess survivability of occupants during crash, to assert adequacy of the design, and to gain federal certification. Although there is no substitute for experimental tests, analytical models are often developed and used to study alternate test conditions, to conduct trade-off studies, and to improve designs. To validate results from analytical predictions, test and analysis results must be compared to determine the model adequacy. The mathematical approach evaluated in this paper decomposes observed time responses into dominant deformation shapes and their corresponding contribution to the measured response. To correlate results, orthogonality of test and analysis shapes is used as a criterion. Data from an impact test of a composite fuselage is used and compared to finite element predictions. In this example, the impact response was decomposed into multiple shapes but only two dominant shapes explained over 85% of the measured response

Electrospun biocompatible Chitosan/MIL-101 (Fe) composite nanofibers for solid-phase extraction of Δ9-tetrahydrocannabinol in whole blood samples using Box-Behnken experimental design.

PubMed

Asiabi, Mina; Mehdinia, Ali; Jabbari, Ali

2017-01-06

The nanofibers of biocompatible Chitosan/MIL-101 (Fe) composite were synthesized by a simple, cheap and accessible electrospining method and applied for mat-based extraction of trace amount of Δ9-tetrahydrocannabinol (THC) from human whole blood sample following its combination by high performance liquid chromatography-ultraviolet detection. The composite nanofibres were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X-ray diffraction and N 2 adsorption-desorption experiments. The volume of eluting solvent, sorbent amount, pH and% NaCl (w/v) influencing on the responses were investigated using factorial experimental design. The optimum point was achieved by analysis of the results according to design expert (DX) software. The volume of eluting solvent, sorbent amount and pH were significant variables, and 150μL, 7mg and 7.0 were respectively chosen for obtaining the best extraction response. Under the optimum conditions, the method was exhibited a linear range of 0.1-100μgL -1 (R 2 =0.9943) for THC with a detection limit of 0.04μgL -1 . Acceptable values for intra-day (3.2%) and inter-day (4.8%) relative standard deviations were obtained. The high preconcentration factor (970) and satisfactory recoveries (88.2%-92.4%) in whole blood samples were achieved which proved the capability of the method for trace determination of THC in the human whole blood samples. Copyright © 2016 Elsevier B.V. All rights reserved.

The choice of ultrasound assisted extraction coupled with spectrophotometric for rapid determination of gallic acid in water samples: Central composite design for optimization of process variables.

PubMed

Pooralhossini, Jaleh; Ghaedi, Mehrorang; Zanjanchi, Mohammad Ali; Asfaram, Arash

2017-01-01

A sensitive procedure namely ultrasound-assisted (UA) coupled dispersive nano solid-phase microextraction spectrophotometry (DNSPME-UV-Vis) was designed for preconcentration and subsequent determination of gallic acid (GA) from water samples, while the detailed of composition and morphology and also purity and structure of this new sorbent was identified by techniques like field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDX) techniques. Among conventional parameters viz. pH, amount of sorbent, sonication time and volume of elution solvent based on Response Surface Methodology (RSM) and central composite design according to statistics based contour the best operational conditions was set at pH of 2.0; 1.5mg sorbent, 4.0min sonication and 150μL ethanol. Under these pre-qualified conditions the method has linear response over wide concentration range of 15-6000ngmL -1 with a correlation coefficient of 0.9996. The good figure of merits like acceptable LOD (S/N=3) and LOQ (S/N=10) with numerical value of 2.923 and 9.744ngmL -1 , respectively and relative recovery between 95.54 and 100.02% show the applicability and efficiency of this method for real samples analysis with RSDs below 6.0%. Finally the method with good performance were used for monitoring under study analyte in various real samples like tap, river and mineral waters. Copyright © 2016 Elsevier B.V. All rights reserved.

Probabilistic Micromechanics and Macromechanics for Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Mital, Subodh K.; Shah, Ashwin R.

1997-01-01

The properties of ceramic matrix composites (CMC's) are known to display a considerable amount of scatter due to variations in fiber/matrix properties, interphase properties, interphase bonding, amount of matrix voids, and many geometry- or fabrication-related parameters, such as ply thickness and ply orientation. This paper summarizes preliminary studies in which formal probabilistic descriptions of the material-behavior- and fabrication-related parameters were incorporated into micromechanics and macromechanics for CMC'S. In this process two existing methodologies, namely CMC micromechanics and macromechanics analysis and a fast probability integration (FPI) technique are synergistically coupled to obtain the probabilistic composite behavior or response. Preliminary results in the form of cumulative probability distributions and information on the probability sensitivities of the response to primitive variables for a unidirectional silicon carbide/reaction-bonded silicon nitride (SiC/RBSN) CMC are presented. The cumulative distribution functions are computed for composite moduli, thermal expansion coefficients, thermal conductivities, and longitudinal tensile strength at room temperature. The variations in the constituent properties that directly affect these composite properties are accounted for via assumed probabilistic distributions. Collectively, the results show that the present technique provides valuable information about the composite properties and sensitivity factors, which is useful to design or test engineers. Furthermore, the present methodology is computationally more efficient than a standard Monte-Carlo simulation technique; and the agreement between the two solutions is excellent, as shown via select examples.

Short-term response of ground-dwelling macroarthropods to shelterwood harvests in a productive Southern Appalachian upland hardwood forest

Treesearch

Jr. Westby-Gibson; Cathryn H. Greenberg; Christopher E. Moorman; T.G. Forrest; Tara L. Keyser; Dean M. Simon; Gordon S. Warburton

2017-01-01

 Macroarthropods rarely are considered in forest management decisions, despite their ecological importance as decomposers, herbivores, pollinators, predators, and nutrient cyclers, and potential of some taxa as indicators of forest condition. We used a replicated design to experimentally determine if, and how, community composition,...

Using Central Composite Experimental Design to Optimize the Degradation of Tylosin from Aqueous Solution by Photo-Fenton Reaction

PubMed Central

Sarrai, Abd Elaziz; Hanini, Salah; Merzouk, Nachida Kasbadji; Tassalit, Djilali; Szabó, Tibor; Hernádi, Klára; Nagy, László

2016-01-01

The feasibility of the application of the Photo-Fenton process in the treatment of aqueous solution contaminated by Tylosin antibiotic was evaluated. The Response Surface Methodology (RSM) based on Central Composite Design (CCD) was used to evaluate and optimize the effect of hydrogen peroxide, ferrous ion concentration and initial pH as independent variables on the total organic carbon (TOC) removal as the response function. The interaction effects and optimal parameters were obtained by using MODDE software. The significance of the independent variables and their interactions was tested by means of analysis of variance (ANOVA) with a 95% confidence level. Results show that the concentration of the ferrous ion and pH were the main parameters affecting TOC removal, while peroxide concentration had a slight effect on the reaction. The optimum operating conditions to achieve maximum TOC removal were determined. The model prediction for maximum TOC removal was compared to the experimental result at optimal operating conditions. A good agreement between the model prediction and experimental results confirms the soundness of the developed model. PMID:28773551

Optimization of tannase production by a novel Klebsiella pneumoniae KP715242 using central composite design.

PubMed

Kumar, Mukesh; Rana, Shiny; Beniwal, Vikas; Salar, Raj Kumar

2015-09-01

A novel tannase producing bacterial strain was isolated from rhizospheric soil of Acacia species and identified as Klebsiella pneumoniae KP715242. A 3.25-fold increase in tannase production was achieved upon optimization with central composite design using response surface methodology. Four variables namely pH, temperature, incubation period, and agitation speed were used to optimize significant correlation between the effects of these variables on tannase production. A second-order polynomial was fitted to data and validated by ANOVA. The results showed a complex relationship between variables and response given that all factors were significant and could explain 99.6% of the total variation. The maximum production was obtained at 5.2 pH, 34.97 °C temperature, 103.34 rpm agitation speed and 91.34 h of incubation time. The experimental values were in good agreement with the predicted ones and the models were highly significant with a correlation coefficient ( R 2 ) of 0.99 and a highly significant F-value of 319.37.

Investigation of dosimetric characteristics of a core-shell quantum dots nano composite (CdTe/CdS/PMMA): fabrication of a new gamma sensor

NASA Astrophysics Data System (ADS)

Feizi, Shahzad; Zare, Hakimeh; Hoseinpour, Masoumeh

2018-06-01

CdTe/CdS-PMMA nanocomposite was prepared using dispersion of CdTe/CdS core-shell quantum dots (QDs) in poly methyl methacrylate (PMMA) polymer matrix. High-quality CdTe/CdS core/shell quantum dots were synthesized in aqueous solution and were transferred from water to chloroform using ligand-exchange process in the presence of 1-dodecanethiol (1-DDT). Transmission electron microscopy analysis reveals that the obtained nano-particles are highly crystalline nature with mean diameter of 3.6 nm. To prepare an ohmic contact detector, a conductive cell with two silver coated walls was designed and fabricated for exploring gamma detecting properties of the nano composite. New detector was assessed for the linearity of doserate response, angular dependence, sensitivity and repeatability. The results show that the dose rate response of the prepared sensor is linear in the dose rate range of 50-145 mGy/min. So this nanocomposite can be utilized as a potential gamma sensor in the medical radiation device design.

Evaluation of the Composition of Culture Medium for Yeast Biomass Production Using Raw Glycerol from Biodiesel Synthesis

PubMed Central

dos Santos, Elisane Odriosolla; Michelon, Mariano; Furlong, Eliana Badiale; Burkert, Janaína Fernandes de Medeiros; Kalil, Susana Juliano; Burkert, Carlos André Veiga

2012-01-01

The work herewith investigated the production of yeast biomass as a source of protein, using Yarrowia lipolytica NRRL YB-423 and raw glycerol from biodiesel synthesis as the main carbon source. A significant influence of glycerol concentration, initial pH and yeast extract concentration on biomass and protein content was observed according to the 2v5-1 fractional design. These factors were further evaluated using a central composite design and response surface methodology, and an empirical model for protein content was established and validated. The biomass of Yarrowia lipolytica NRRL YB-423 reached 19.5 ± 1.0 g/L in shaken flasks cultivation, with a protein content of 20.1 ± 0.6% (w/w). PMID:24031849

Structural similitude and design of scaled down laminated models

NASA Technical Reports Server (NTRS)

Simitses, G. J.; Rezaeepazhand, J.

1993-01-01

The excellent mechanical properties of laminated composite structures make them prime candidates for wide variety of applications in aerospace, mechanical and other branches of engineering. The enormous design flexibility of advanced composites is obtained at the cost of large number of design parameters. Due to complexity of the systems and lack of complete design based informations, designers tend to be conservative in their design. Furthermore, any new design is extensively evaluated experimentally until it achieves the necessary reliability, performance and safety. However, the experimental evaluation of composite structures are costly and time consuming. Consequently, it is extremely useful if a full-scale structure can be replaced by a similar scaled-down model which is much easier to work with. Furthermore, a dramatic reduction in cost and time can be achieved, if available experimental data of a specific structure can be used to predict the behavior of a group of similar systems. This study investigates problems associated with the design of scaled models. Such study is important since it provides the necessary scaling laws, and the factors which affect the accuracy of the scale models. Similitude theory is employed to develop the necessary similarity conditions (scaling laws). Scaling laws provide relationship between a full-scale structure and its scale model, and can be used to extrapolate the experimental data of a small, inexpensive, and testable model into design information for a large prototype. Due to large number of design parameters, the identification of the principal scaling laws by conventional method (dimensional analysis) is tedious. Similitude theory based on governing equations of the structural system is more direct and simpler in execution. The difficulty of making completely similar scale models often leads to accept certain type of distortion from exact duplication of the prototype (partial similarity). Both complete and partial similarity are discussed. The procedure consists of systematically observing the effect of each parameter and corresponding scaling laws. Then acceptable intervals and limitations for these parameters and scaling laws are discussed. In each case, a set of valid scaling factors and corresponding response scaling laws that accurately predict the response of prototypes from experimental models is introduced. The examples used include rectangular laminated plates under destabilizing loads, applied individually, vibrational characteristics of same plates, as well as cylindrical bending of beam-plates.

The Behaviour of Naturally Debonded Composites Due to Bending Using a Meso-Level Model

NASA Astrophysics Data System (ADS)

Lord, C. E.; Rongong, J. A.; Hodzic, A.

2012-06-01

Numerical simulations and analytical models are increasingly being sought for the design and behaviour prediction of composite materials. The use of high-performance composite materials is growing in both civilian and defence related applications. With this growth comes the necessity to understand and predict how these new materials will behave under their exposed environments. In this study, the displacement behaviour of naturally debonded composites under out-of-plane bending conditions has been investigated. An analytical approach has been developed to predict the displacement response behaviour. The analytical model supports multi-layered composites with full and partial delaminations. The model can be used to extract bulk effective material properties in which can be represented, later, as an ESL (Equivalent Single Layer). The friction between each of the layers is included in the analytical model and is shown to have distinct behaviour for these types of composites. Acceptable agreement was observed between the model predictions, the ANSYS finite element model, and the experiments.

An Integrated Approach Linking Process to Structural Modeling With Microstructural Characterization for Injections-Molded Long-Fiber Thermoplastics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nguyen, Ba Nghiep; Bapanapalli, Satish K.; Smith, Mark T.

2008-09-01

The objective of our work is to enable the optimum design of lightweight automotive structural components using injection-molded long fiber thermoplastics (LFTs). To this end, an integrated approach that links process modeling to structural analysis with experimental microstructural characterization and validation is developed. First, process models for LFTs are developed and implemented into processing codes (e.g. ORIENT, Moldflow) to predict the microstructure of the as-formed composite (i.e. fiber length and orientation distributions). In parallel, characterization and testing methods are developed to obtain necessary microstructural data to validate process modeling predictions. Second, the predicted LFT composite microstructure is imported into amore » structural finite element analysis by ABAQUS to determine the response of the as-formed composite to given boundary conditions. At this stage, constitutive models accounting for the composite microstructure are developed to predict various types of behaviors (i.e. thermoelastic, viscoelastic, elastic-plastic, damage, fatigue, and impact) of LFTs. Experimental methods are also developed to determine material parameters and to validate constitutive models. Such a process-linked-structural modeling approach allows an LFT composite structure to be designed with confidence through numerical simulations. Some recent results of our collaborative research will be illustrated to show the usefulness and applications of this integrated approach.« less

From development to aging: Holistic face perception in children, younger and older adults.

PubMed

Meinhardt-Injac, Bozana; Boutet, Isabelle; Persike, Malte; Meinhardt, Günter; Imhof, Margarete

2017-01-01

Few published reports examine the development of holistic face processing across the lifespan such that face-specific processes are adequately differentiated from general developmental effects. To address this gap in the literature, we used the complete design of the composite paradigm (Richler & Gauthier, 2014) with faces and non-face control objects (watches) to investigate holistic processing in children (8-10years), young adults (20-32years) and older adults (65-78years). Several modifications to past research designs were introduced to improve the ability to draw conclusions about the development of holistic processing in terms of face-specificity, response bias, and age-related differences in attention. Attentional focus (narrow vs. wide focus at study) influenced the magnitude of the composite effect without eliminating holistic face processing in all age groups. Young adults showed large composite effects for faces, but none for watches. In contrast, older adults and children showed composite effects for both faces and watches, although the effects for faces were larger. Our findings suggest that holistic processing, as measured by the composite effect, might be moderated by less efficient attentional control in children and older adults. The study also underscores the importance of including comparable complex objects when investigating face processing across the lifespan. Copyright © 2016 Elsevier B.V. All rights reserved.

The grindability of glass fibre reinforced polymer composite

NASA Astrophysics Data System (ADS)

Chockalingam, P.

The use of glass fibre-reinforced polymer (GFRP) composite materials is extensive due to their favourable mechanical properties and near net shape production. However, almost all composite structures require post-processing operations such as grinding to meet surface finish requirements during assembly. Unlike that of conventional metal, grinding of GFRP composite needs special tools and parameters due to the abrasive nature of fibres and the delamination of the workpiece. Therefore, proper selection of the tools and parameters is important. This research aims to investigate the effects of wheel speed, feed, depth of cut, grinding wheel and coolant on the grindability of chopped strand mat (CSM) GFRP. Grinding was carried out in a precision CNC (Master-10HVA) high-speed machining centre under three conditions, namely dry, and wet conditions with synthetic coolant and emulsion coolant, using alumina wheel (OA46QV) and CBN wheel (B46QV). The grinding experiments were conducted per the central composite design of design of experiments. The grindability aspects investigated were surface area roughness (Sa) and cutting force ratio (µ). The responses were analyzed by developing fuzzy logic models. The surface area roughness and cutting force ratio values predicted by the fuzzy logic models are mostly in good agreement with experimental data, and hence conclusion was made that these models were reliable.

Acoustic emission-based sensor analysis and damage classification for structural health monitoring of composite structures

NASA Astrophysics Data System (ADS)

Uprety, Bibhisha

Within the aerospace industry the need to detect and locate impact events, even when no visible damage is present, is important both from the maintenance and design perspectives. This research focused on the use of Acoustic Emission (AE) based sensing technologies to identify impact events and characterize damage modes in composite structures for structural health monitoring. Six commercially available piezoelectric AE sensors were evaluated for use with impact location estimation algorithms under development at the University of Utah. Both active and passive testing were performed to estimate the time of arrival and plate wave mode velocities for impact location estimation. Four sensors were recommended for further comparative investigations. Furthermore, instrumented low-velocity impact experiments were conducted on quasi-isotropic carbon/epoxy composite laminates to initiate specific types of damage: matrix cracking, delamination and fiber breakage. AE signal responses were collected during impacting and the test panels were ultrasonically C-scanned after impact to identify the internal damage corresponding to the AE signals. Matrix cracking and delamination damage produced using more compliant test panels and larger diameter impactor were characterized by lower frequency signals while fiber breakage produced higher frequency responses. The results obtained suggest that selected characteristics of sensor response signals can be used both to determine whether damage is produced during impacting and to characterize the types of damage produced in an impacted composite structure.

Use of microfasteners to produce damage tolerant composite structures

PubMed Central

Hallett, Stephen R.

2016-01-01

The paper concerns the mechanical performance of continuous fibre/thermosetting polymer matrix composites reinforced in the through-thickness direction with fibrous or metallic rods or threads in order to mitigate against low delamination resistance. Specific illustrations of the effects of microfasteners in reducing delamination crack growth are made for Z-pinned and tufted composites. Response to loading in such ‘structured materials’ is subject to multiple parameters defining their in-plane and out-of-plane properties. Single microfastener mechanical tests are well suited to establish the crack bridging laws under a range of loading modes, from simple delamination crack opening to shear, and provide the basis for predicting the corresponding response of microfastener arrays, within a given material environment. The fundamental experiments on microfasteners can be used to derive analytical expressions to describe the crack bridging behaviour in a general sense, to cover all possible loadings. These expressions can be built into cohesive element constitutive laws in a finite-element framework for modelling the effects of microfastener arrays on the out-of-plane mechanical response of reinforced structural elements, including the effects of known manufacturing imperfections. Such predictive behaviour can then be used to assess structural integrity under complex loading, as part of the component design process. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242299

Analysis and characterization of structurally embedded vascular antennas using liquid metals

NASA Astrophysics Data System (ADS)

Hartl, Darren J.; Huff, Gregory H.; Pan, Hong; Smith, Lisa; Bradford, Robyn L.; Frank, Geoffrey J.; Baur, Jeffrey W.

2016-04-01

Over the past decade, a large body of research associated with the addition of microvascular networks to structural composites has been generated. The engineering goal is most often the extension of structural utility to include extended functionalities such as self-healing or improved thermal management and resilience. More recently, efforts to design reconfigurable embedded electronics via the incorporation of non-toxic liquid metals have been initiated. A wide range of planar antenna configurations are possible, and the trade-offs between structural effects, other system costs, and increased flexibility in transmitting and receiving frequencies are being explored via the structurally embedded vascular antenna (SEVA) concept. This work describes for the first time the design of a bowtie-like tunable liquid metal-based antenna for integration into a structural composite for electromagnetic use. The design of both the solid/fluid feed structure and fluid transmission lines are described and analysis results regarding the RF performance of the antenna are provided. Fabrication methods for the SEVA are explained in detail and as-fabricated components are described. Challenges associated with both fabrication and system implementation and testing are elucidated. Results from preliminary RF testing indicate that in situ response tuning is feasible in these novel multifunctional composites.

Hybrid-Wing-Body Vehicle Composite Fuselage Analysis and Case Study

NASA Technical Reports Server (NTRS)

Mukhopadhyay, Vivek

2014-01-01

Recent progress in the structural analysis of a Hybrid Wing-Body (HWB) fuselage concept is presented with the objective of structural weight reduction under a set of critical design loads. This pressurized efficient HWB fuselage design is presently being investigated by the NASA Environmentally Responsible Aviation (ERA) project in collaboration with the Boeing Company, Huntington Beach. The Pultruded Rod-Stiffened Efficient Unitized Structure (PRSEUS) composite concept, developed at the Boeing Company, is approximately modeled for an analytical study and finite element analysis. Stiffened plate linear theories are employed for a parametric case study. Maximum deflection and stress levels are obtained with appropriate assumptions for a set of feasible stiffened panel configurations. An analytical parametric case study is presented to examine the effects of discrete stiffener spacing and skin thickness on structural weight, deflection and stress. A finite-element model (FEM) of an integrated fuselage section with bulkhead is developed for an independent assessment. Stress analysis and scenario based case studies are conducted for design improvement. The FEM model specific weight of the improved fuselage concept is computed and compared to previous studies, in order to assess the relative weight/strength advantages of this advanced composite airframe technology

A systems-approach to the design of the Eos data and information system

NASA Technical Reports Server (NTRS)

Chase, Robert R. P.

1987-01-01

The task of designing a data and information system responsive to the needs of Eos users is stratified by level and approached with contemporary systems design practices. Appropriate systems design principles are applied at the conceptual design level in this paper. A functional, architectural design is described in terms of elemental composition, top-level functions, and external and internal interfaces. The functional validity of this design has been tested and verified through the use of realistic user scenarios consistent with existing plans for the 1990s, the Space Station era. Technologic and management impediments to the development of the requisite data and information system for Eos are examined and a consistent methodology for developing this system is discussed.

RH-LLW Disposal Facility Project CD-2/3 to Design/Build Proposal Reconciliation Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Annette L. Schafer

2012-06-01

A reconciliation plan was developed and implemented to address potential gaps and responses to gaps between the design/build vendor proposals and the Critical Decision-2/3 approval request package for the Remote-Handled Low Level Waste Disposal Facility Project. The plan and results of the plan implementation included development of a reconciliation team comprised of subject matter experts from Battelle Energy Alliance and the Department of Energy Idaho Operations Office, identification of reconciliation questions, reconciliation by the team, identification of unresolved/remaining issues, and identification of follow-up actions and subsequent approvals of responses. The plan addressed the potential for gaps to exist in themore » following areas: • Department of Energy Order 435.1, “Radioactive Waste Management,” requirements, including the performance assessment, composite analysis, monitoring plan, performance assessment/composite analysis maintenance plan, and closure plan • Environmental assessment supporting the National Environmental Policy Act • Nuclear safety • Safeguards and security • Emplacement operations • Requirements for commissioning • General project implementation. The reconciliation plan and results of the plan implementation are provided in a business-sensitive project file. This report provides the reconciliation plan and non-business sensitive summary responses to identified gaps.« less

Influence of Hesperidin on the Systemic and Intestinal Rat Immune Response.

PubMed

Camps-Bossacoma, Mariona; Franch, Àngels; Pérez-Cano, Francisco J; Castell, Margarida

2017-06-06

Polyphenols, widely found in edible plants, influence the immune system. Nevertheless, the immunomodulatory properties of hesperidin, the predominant flavanone in oranges, have not been deeply studied. To establish the effect of hesperidin on in vivo immune response, two different conditions of immune system stimulations in Lewis rats were applied. In the first experimental design, rats were intraperitoneally immunized with ovalbumin (OVA) plus Bordetella pertussis toxin and alum as the adjuvants, and orally given 100 or 200 mg/kg hesperidin. In the second experimental design, rats were orally sensitized with OVA together with cholera toxin and fed a diet containing 0.5% hesperidin. In the first approach, hesperidin administration changed mesenteric lymph node lymphocyte (MLNL) composition, increasing the TCRαβ+ cell percentage and decreasing that of B lymphocytes. Furthermore, hesperidin enhanced the interferon (IFN)-γ production in stimulated MLNL. In the second approach, hesperidin intake modified the lymphocyte composition in the intestinal epithelium (TCRγδ+ cells) and the lamina propria (TCRγδ+, CD45RA+, natural killer, natural killer T, TCRαβ+CD4+, and TCRαβ+CD8+ cells). Nevertheless, hesperidin did not modify the level of serum anti-OVA antibodies in either study. In conclusion, hesperidin does possess immunoregulatory properties in the intestinal immune response, but this effect is not able to influence the synthesis of specific antibodies.

Natural fibres actuators for smart bio-inspired hygromorph biocomposites

NASA Astrophysics Data System (ADS)

Le Duigou, Antoine; Requile, Samuel; Beaugrand, Johnny; Scarpa, Fabrizio; Castro, Mickael

2017-12-01

Hygromorph biocomposite (HBC) actuators make use of the transport properties of plant fibres to generate an out-of-plane displacement when a moisture gradient is present. HBC actuators possess a design based on the bilayer configuration of natural hygromorph actuators (like pine cone, wheat awn, Selaginella lepidophyll). In this work we present a series of design guidelines for HBCs with improved performance, low environmental footprints and high durability in severe environments. We develop a theoretical actuating response (curvature) formulation of maleic anhydride polypropylene (MAPP)/plant fibres based on bimetallic actuators theory. The actuation response is evaluated as a function of the fibre type (flax, jute, kenaf and coir). We demonstrate that the actuation is directly related to the fibre microstructure and its biochemical composition. The jute and flax fibres appear to be the best candidates for use in HBCs. Flax/MAPP and jute/MAPP HBCs exhibit similar actuating behaviours during the sorption phase (amplitude and speed), but different desorption characteristics due to the combined effect of the lumen size, fibre division and biochemical composition on the desorption mechanism. During hygromechanical fatigue tests the jute/MAPP HBCs exhibit a drastic improvement in durability compared to their flax counterparts. We also provide a demonstration on how HBCs can be used to trigger deployment of more complex structures based on Origami and Kirigami designs.

Ultrasound-Assisted Extraction of Cannabinoids from Cannabis Sativa L. Optimized by Response Surface Methodology.

PubMed

Agarwal, Charu; Máthé, Katalin; Hofmann, Tamás; Csóka, Levente

2018-03-01

Ultrasonication was used to extract bioactive compounds from Cannabis sativa L. such as polyphenols, flavonoids, and cannabinoids. The influence of 3 independent factors (time, input power, and methanol concentration) was evaluated on the extraction of total phenols (TPC), flavonoids (TF), ferric reducing ability of plasma (FRAP) and the overall yield. A face-centered central composite design was used for statistical modelling of the response data, followed by regression and analysis of variance in order to determine the significance of the model and factors. Both the solvent composition and the time significantly affected the extraction while the sonication power had no significant impact on the responses. The response predictions obtained at optimum extraction conditions of 15 min time, 130 W power, and 80% methanol were 314.822 mg GAE/g DW of TPC, 28.173 mg QE/g DW of TF, 18.79 mM AAE/g DW of FRAP, and 10.86% of yield. A good correlation was observed between the predicted and experimental values of the responses, which validated the mathematical model. On comparing the ultrasonic process with the control extraction, noticeably higher values were obtained for each of the responses. Additionally, ultrasound considerably improved the extraction of cannabinoids present in Cannabis. Low frequency ultrasound was employed to extract bioactive compounds from the inflorescence part of Cannabis. The responses evaluated were-total phenols, flavonoids, ferric reducing assay and yield. The solvent composition and time significantly influenced the extraction process. Appreciably higher extraction of cannabinoids was achieved on sonication against control. © 2018 Institute of Food Technologists®.

Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, volume 1

NASA Technical Reports Server (NTRS)

Soderquist, Joseph R. (Compiler); Neri, Lawrence M. (Compiler); Bohon, Herman L. (Compiler)

1992-01-01

This publication contains the proceedings of the Ninth DOD/NASA/FAA conference on Fibrous Composites in structural Design. Presentations were made in the following areas of composite structural design: perspectives in composites; design methodology; design applications; design criteria; supporting technology; damage tolerance; and manufacturing.

Numbers of center points appropriate to blocked response surface experiments

NASA Technical Reports Server (NTRS)

Holms, A. G.

1979-01-01

Tables are given for the numbers of center points to be used with blocked sequential designs of composite response surface experiments as used in empirical optimum seeking. The star point radii for exact orthogonal blocking is presented. The center point options varied from a lower limit of one to an upper limit equal to the numbers proposed by Box and Hunter for approximate rotatability and uniform variance, and exact orthogonal blocking. Some operating characteristics of the proposed options are described.

Application of Statistic Experimental Design to Assess the Effect of Gammairradiation Pre-Treatment on the Drying Characteristics and Qualities of Wheat

NASA Astrophysics Data System (ADS)

Yu, Yong; Wang, Jun

Wheat, pretreated by 60Co gamma irradiation, was dried by hot-air with irradiation dosage 0-3 kGy, drying temperature 40-60 °C, and initial moisture contents 19-25% (drying basis). The drying characteristics and dried qualities of wheat were evaluated based on drying time, average dehydration rate, wet gluten content (WGC), moisture content of wet gluten (MCWG)and titratable acidity (TA). A quadratic rotation-orthogonal composite experimental design, with three variables (at five levels) and five response functions, and analysis method were employed to study the effect of three variables on the individual response functions. The five response functions (drying time, average dehydration rate, WGC, MCWG, TA) correlated with these variables by second order polynomials consisting of linear, quadratic and interaction terms. A high correlation coefficient indicated the suitability of the second order polynomial to predict these response functions. The linear, interaction and quadratic effects of three variables on the five response functions were all studied.

Optimization of olive oil based O/W nanoemulsions prepared through ultrasonic homogenization: A response surface methodology approach.

PubMed

Mehmood, Tahir; Ahmad, Asif; Ahmed, Anwaar; Ahmed, Zaheer

2017-08-15

The present study was conducted to prepare co-surfactant free, olive-oil based alpha tocopherol nanoemulsions, using a food grade non-ionic surfactant. Response surface methodology (RSM) was used to determine the effects of independent variables (ultrasonic homogenization time, olive oil concentrations and surfactant contents) on different physico-chemical characteristics of O/W nanoemulsions. This study was carried out using a central composite design. The coefficients of determination were greater than 0.900 for all response variables and there were significant effects of independent variables on all responses. The optimum levels of independent variables for the preparation of nanoemulsions were 3min. ultrasonic homogenization time, 4% olive oil content and 2.08% surfactant concentration. The physico-chemical responses at these levels were 151.68nm particle size, 7.17% p-anisidine and 88.64% antioxidant activity. These results will help in design of nanoemulsions with optimum independent variables. Copyright © 2017 Elsevier Ltd. All rights reserved.

Electrical and thermal response of carbon nanotube composites under quasi-static and dynamic loading

NASA Astrophysics Data System (ADS)

O'Connell, Christopher D.

Carbon nanotube (CNT) composites have attracted much interest due to their possible technical applications as conductive polymers and sensory materials. This study will consist of two major objectives: 1.) to investigate the thermal conductivity and thermal response of multi-wall carbon nanotube (MWCNT) composites under quasi-static loading, and 2.) to investigate the electrical response of carboxyl-terminated butadiene (CTBN) rubber-reinforced MWCNT/Epoxy composites under quasi-static and dynamic loading. Similar studies have shown that the electrical conductivity of CNT/Epoxy composites dramatically increases with compressive strains up to 15%. Part 1 seeks to find out if thermal conductivity show a similar response to electrical conductivity under an applied load. Part 2 seeks to investigate how the addition of rubber affects the mechanical and electrical response of the composite subjected to quasi-static and dynamic loading. By knowing how thermal and electrical properties change under a given applied strain, we attempt to broaden the breadth of understanding of CNT/epoxy composites and inqure the microscopic interactions occurring between the two. Electrical experiments sought to investigate the electrical response of rubber-reinforced carbon nanotube epoxy composites under quasi-static and dynamic loading. Specimens were fabricated with CTBN rubber content of 10 parts per hundredth resin (phr), 20 phr, 30 phr and 0 phr for a basis comparison. Both quasi-static and dynamic mechanical response showed a consistent decrease in peak stress and Young's modulus with increasing rubber content. Trends in the electrical response between each case were clearly observed with peak resistance changes ranging from 58% to 73% and with each peak occurring at a higher value with increasing rubber content, with the exception of the rubber-free specimens. It was concluded that among the rubber-embedded specimens, the addition of rubber helped to delay micro-cracking and degradation and thus prolong the electrical response of the specimen to higher strains. Thermal experiments were first established by designing and fabricating an apparatus to determine the thermal conductivity of an unknown material. The principle of the apparatus is a steady-state one-dimensional comparative method where reference materials of known thermal conductivity are used to determine the system heat flux and in turn, the thermal conductivity of a given specimen. A thermal percolation study was conducted in order to determine a possible threshold of thermal transport of the material. The recorded values of thermal conductivity from 0 -- 0.2 wt% showed no such threshold with all specimens of different CNT loadings yielding similar values of thermal conductivity. The apparatus containing the CNT/epoxy specimen was then quasi-statically compressed to observe how the thermal conductivity changes with strains up to 20%. While a small decrease in thermal conductivity was observed under strain, it can mostly be attributed to material degradation and bulging.

Flexural behavior of the fibrous cementitious composites (FCC) containing hybrid fibres

NASA Astrophysics Data System (ADS)

Ramli, Mahyuddin; Ban, Cheah Chee; Samsudin, Muhamad Fadli

2018-02-01

In this study, the flexural behavior of the fibrous cementitious composites containing hybrid fibers was investigated. Waste materials or by product materials such as pulverized fuel ash (PFA) and ground granulated blast-furnace slag (GGBS) was used as supplementary cement replacement. In addition, barchip and kenaf fiber will be used as additional materials for enhance the flexural behavior of cementitious composites. A seven mix design of fibrous cementitious composites containing hybrid fiber mortar were fabricated with PFA-GGBS as cement replacement at 50% with hybridization of barchip and kenaf fiber between 0.5% and 2.0% by total volume weight. The FCC with hybrid fibers mortar will be fabricated by using 50 × 50 × 50 mm, 40 × 40 × 160 mm and 350 × 125 × 30 mm steel mold for assessment of mechanical performances and flexural behavior characteristics. The flexural behavior and mechanical performance of the PFA-GGBS with hybrid fiber mortar block was assessed in terms of load deflection response, stress-strain response, crack development, compressive and flexural strength after water curing for 28 days. Moreover, the specimen HBK 1 and HBK 2 was observed equivalent or better in mechanical performance and flexural behavior as compared to control mortar.

Estimating Cosmic-Ray Spectral Parameters from Simulated Detector Responses with Detector Design Implications

NASA Technical Reports Server (NTRS)

Howell, L. W.

2001-01-01

A simple power law model consisting of a single spectral index (alpha-1) is believed to be an adequate description of the galactic cosmic-ray (GCR) proton flux at energies below 10(exp 13) eV, with a transition at knee energy (E(sub k)) to a steeper spectral index alpha-2 > alpha-1 above E(sub k). The maximum likelihood procedure is developed for estimating these three spectral parameters of the broken power law energy spectrum from simulated detector responses. These estimates and their surrounding statistical uncertainty are being used to derive the requirements in energy resolution, calorimeter size, and energy response of a proposed sampling calorimeter for the Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS). This study thereby permits instrument developers to make important trade studies in design parameters as a function of the science objectives, which is particularly important for space-based detectors where physical parameters, such as dimension and weight, impose rigorous practical limits to the design envelope.

Optimization of hybrid laser - TIG welding of 316LN steel using response surface methodology (RSM)

NASA Astrophysics Data System (ADS)

Ragavendran, M.; Chandrasekhar, N.; Ravikumar, R.; Saxena, Rajesh; Vasudevan, M.; Bhaduri, A. K.

2017-07-01

In the present study, the hybrid laser - TIG welding parameters for welding of 316LN austenitic stainless steel have been investigated by combining a pulsed laser beam with a TIG welding heat source at the weld pool. Laser power, pulse frequency, pulse duration, TIG current were presumed as the welding process parameters whereas weld bead width, weld cross-sectional area and depth of penetration (DOP) were considered as the process responses. Central composite design was used to complete the design matrix and welding experiments were conducted based on the design matrix. Weld bead measurements were then carried out to generate the dataset. Multiple regression models correlating the process parameters with the responses have been developed. The accuracy of the models were found to be good. Then, the desirability approach optimization technique was employed for determining the optimum process parameters to obtain the desired weld bead profile. Validation experiments were then carried out from the determined optimum process parameters. There was good agreement between the predicted and measured values.

Product diversification of banana cv. Mas Kirana off grade by using a double rotating screw extruder

NASA Astrophysics Data System (ADS)

Setyadjit, S.; Sukasih, E.; Risfaheri, R.

2018-01-01

Extrusion technology is today’s favorite technology since it has a varied, practical and consistent product form. The purpose of this research was to get precise composite flour composition so that the quality of the resulted product has optimum quality for breakfast meals. The experimental design used was Design Expert vs. 7 with response surface box-behnken. The flour composition and level to be inputted to the program were banana flour (10-50g), mung beans (10-30g), egg flour (10-20g). Formula made was based on 200 g with addition of maize flour if the amount is less than 200 g. The extrusion tool used is a Thermo Scientific double rotating screw; with Haake Reomax OS. The best results in terms of carbohydrate content is the Formula 8 with a composition of 60 g of banana flour, 20 g eggs, 20 g of green beans and 100 g maize flour. The proximate chemical content of this formula is carbohydrate 84.04%, protein 8.55%, fat 5.49%, ash content 1.24%. K-calories per 100 g is 419.5 which is higher than the standard of breakfast meals calories.

Advanced composite structures. [metal matrix composites - structural design criteria for spacecraft construction materials

NASA Technical Reports Server (NTRS)

1974-01-01

A monograph is presented which establishes structural design criteria and recommends practices to ensure the design of sound composite structures, including composite-reinforced metal structures. (It does not discuss design criteria for fiber-glass composites and such advanced composite materials as beryllium wire or sapphire whiskers in a matrix material.) Although the criteria were developed for aircraft applications, they are general enough to be applicable to space vehicles and missiles as well. The monograph covers four broad areas: (1) materials, (2) design, (3) fracture control, and (4) design verification. The materials portion deals with such subjects as material system design, material design levels, and material characterization. The design portion includes panel, shell, and joint design, applied loads, internal loads, design factors, reliability, and maintainability. Fracture control includes such items as stress concentrations, service-life philosophy, and the management plan for control of fracture-related aspects of structural design using composite materials. Design verification discusses ways to prove flightworthiness.

Nanostructured Tungsten Oxide Composite for High-Performance Gas Sensors

PubMed Central

Feng-Chen, Siyuan; Aldalbahi, Ali; Feng, Peter Xianping

2015-01-01

We report the results of composite tungsten oxide nanowires-based gas sensors. The morphologic surface, crystallographic structures, and chemical compositions of the obtained nanowires have been investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman scattering, respectively. The experimental measurements reveal that each wire consists of crystalline nanoparticles with an average diameter of less than 250 nm. By using the synthesized nanowires, highly sensitive prototypic gas sensors have been designed and fabricated. The dependence of the sensitivity of tungsten oxide nanowires to the methane and hydrogen gases as a function of time has been obtained. Various sensing parameters such as sensitivity, response time, stability, and repeatability were investigated in order to reveal the sensing ability. PMID:26512670

Hygrothermomechanical evaluation of transverse filament tape epoxy/polyester fiberglass composites

NASA Technical Reports Server (NTRS)

Lark, R. L.; Chamis, C. C.

1983-01-01

The static and cyclic load behavior of transverse filament tape (TFT) fiberglass/epoxy and TFY fiberglass/polyester composites, intended for use in the design of low-cost wind turbine blades, are presented. The data behavior is also evaluated with respect to predicted properties based on an integrated hygrothermomechanical response theory. Experimental TFT composite data were developed by the testing of laminates made by using composite layups typical of those used for the fabrication of TFT fiberglass wind turbine blades. Static properties include tension, compression, and interlaminar shear strengths at ambient conditions and at high humidity/elevated temperature conditions after a 500 hour exposure. Cyclic fatigue data were obtained using similar environmental conditions and a range of cyclic stresses. The environmental (temperature and moisture) and cyclic load effects on composite strength degradation are subsequently compared with the predictions obtained by using the composite life/durability theory. The results obtained show that the predicted hygrothermomechanical environmental effects on TFT composites are in good agreement with measured data for various properties including fatigue at different cyclic stresses.

Mechanical behaviour of degradable phosphate glass fibres and composites-a review.

PubMed

Colquhoun, R; Tanner, K E

2015-12-23

Biodegradable materials are potentially an advantageous alternative to the traditional metallic fracture fixation devices used in the reconstruction of bone tissue defects. This is due to the occurrence of stress shielding in the surrounding bone tissue that arises from the absence of mechanical stimulus to the regenerating bone due to the mismatch between the elastic modulus of bone and the metal implant. However although degradable polymers may alleviate such issues, these inert materials possess insufficient mechanical properties to be considered as a suitable alternative to current metallic devices at sites of sufficient mechanical loading. Phosphate based glasses are an advantageous group of materials for tissue regenerative applications due to their ability to completely degrade in vivo at highly controllable rates based on the specific glass composition. Furthermore the release of the glass's constituent ions can evoke a therapeutic stimulus in vivo (i.e. osteoinduction) whilst also generating a bioactive response. The processing of these materials into fibres subsequently allows them to act as reinforcing agents in degradable polymers to simultaneously increase its mechanical properties and enhance its in vivo response. However despite the various review articles relating to the compositional influences of different phosphate glass systems, there has been limited work summarising the mechanical properties of different phosphate based glass fibres and their subsequent incorporation as a reinforcing agent in degradable composite materials. As a result, this review article examines the compositional influences behind the development of different phosphate based glass fibre compositions intended as composite reinforcing agents along with an analysis of different potential composite configurations. This includes variations in the fibre content, matrix material and fibre architecture as well as other novel composites designs.

Innovative Structural Materials and Sections with Strain Hardening Cementitious Composites

NASA Astrophysics Data System (ADS)

Dey, Vikram

The motivation of this work is based on development of new construction products with strain hardening cementitious composites (SHCC) geared towards sustainable residential applications. The proposed research has three main objectives: automation of existing manufacturing systems for SHCC laminates; multi-level characterization of mechanical properties of fiber, matrix, interface and composites phases using servo-hydraulic and digital image correlation techniques. Structural behavior of these systems were predicted using ductility based design procedures using classical laminate theory and structural mechanics. SHCC sections are made up of thin sections of matrix with Portland cement based binder and fine aggregates impregnating continuous one-dimensional fibers in individual or bundle form or two/three dimensional woven, bonded or knitted textiles. Traditional fiber reinforced concrete (FRC) use random dispersed chopped fibers in the matrix at a low volume fractions, typically 1-2% to avoid to avoid fiber agglomeration and balling. In conventional FRC, fracture localization occurs immediately after the first crack, resulting in only minor improvement in toughness and tensile strength. However in SHCC systems, distribution of cracking throughout the specimen is facilitated by the fiber bridging mechanism. Influence of material properties of yarn, composition, geometry and weave patterns of textile in the behavior of laminated SHCC skin composites were investigated. Contribution of the cementitious matrix in the early age and long-term performance of laminated composites was studied with supplementary cementitious materials such as fly ash, silica fume, and wollastonite. A closed form model with classical laminate theory and ply discount method, coupled with a damage evolution model was utilized to simulate the non-linear tensile response of these composite materials. A constitutive material model developed earlier in the group was utilized to characterize and correlate the behavior of these structural composites under uniaxial tension and flexural loading responses. Development and use of analytical models enables optimal design for application of these materials in structural applications. Another area of immediate focus is the development of new construction products from SHCC laminates such as angles, channels, hat sections, closed sections with optimized cross sections. Sandwich composites with stress skin-cellular core concept were also developed to utilize strength and ductility of fabric reinforced skin in addition to thickness, ductility, and thermal benefits of cellular core materials. The proposed structurally efficient and durable sections promise to compete with wood and light gage steel based sections for lightweight construction and panel application.

Response surface optimization of corn stover pretreatment using dilute phosphoric acid for enzymatic hydrolysis and ethanol production

USDA-ARS?s Scientific Manuscript database

Dilute H3PO4 (0.0 - 2.0%, v/v) was used to pretreat corn stover (10%, w/w) for conversion to ethanol. Pretreatment conditions were optimized for temperature, acid loading, and time using a central composite design. Optimal pretreatment conditions were chosen to promote sugar yields following enzym...

Forest Inventory and Analysis Database of the United States of America (FIA)

Treesearch

Andrew N. Gray; Thomas J. Brandeis; John D. Shaw; William H. McWilliams; Patrick Miles

2012-01-01

Extensive vegetation inventories established with a probabilistic design are an indispensable tool in describing distributions of species and community types and detecting changes in composition in response to climate or other drivers. The Forest Inventory and Analysis Program measures vegetation in permanent plots on forested lands across the United States of America...

Multiculturalism and FYC Teacher Training: An Examination of GTA Perspectives on Being Trained to Teach in a Multicultural, College Classroom

ERIC Educational Resources Information Center

Recasner, Chantae C.

2010-01-01

This research study was designed to determine graduate teaching assistants' (GTAs) perspective on their preparation to teach First Year Composition (FYC) in a multicultural teaching context and to determine the relevance of culturally responsive teaching to this experience. The study utilized the qualitative research methodology Portraiture and…

To What Extent Are Teachers Well Prepared to Teach Multimodal Authoring?

ERIC Educational Resources Information Center

Chandler, Paul D.

2017-01-01

This study reports on the responses to a survey of 55 upper primary school teachers, conducted prior to their classes engaging in a substantial unit of work in multimodal composition. The survey was designed to ascertain the extent to which the teachers were already familiar with, and had already embedded in their teaching, a metalanguage of…

First-Year Cadets' Conceptions of General Education Writing at a Senior Military College

ERIC Educational Resources Information Center

Rifenburg, J. Michael; Forester, Brian

2018-01-01

This study investigates conceptions first-year cadets at a US senior military college bring to general education writing courses, often termed first-year composition (FYC). Using a mixed methods research design, we received survey responses from 122 cadets and conducted semi-structured in-person interviews with four first-year cadets. Our data…

An experimental approach to free vibration analysis of smart composite beam

NASA Astrophysics Data System (ADS)

Yashavantha Kumar, G. A.; Sathish Kumar, K. M.

2018-02-01

Experimental vibration analysis is a main concern of this study. In designing any structural component the important parameter that has to be considered is vibration. The present work involves the experimental investigation of free vibration analysis of a smart beam. Smart beam consists of glass/epoxy composite as a main substrate and two PZT patches. The PZT patches are glued above and below the main beam. By experimentation the natural frequencies and mode shapes are obtained for both with and without PZT patches of a beam. Finally through experimentation the response of the smart beam is recorded.

Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, volume 2

NASA Technical Reports Server (NTRS)

Soderquist, Joseph R. (Compiler); Neri, Lawrence M. (Compiler); Bohon, Herman L. (Compiler)

1992-01-01

This publication contains the proceedings of the Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design held at Lake Tahoe, Nevada, during 4-7 Nov. 1991. Presentations were made in the following areas of composite structural design: perspectives in composites, design methodology, design applications, design criteria, supporting technology, damage tolerance, and manufacturing.

Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, volume 3

NASA Technical Reports Server (NTRS)

Soderquist, Joseph R. (Compiler); Neri, Lawrence M. (Compiler); Bohon, Herman L. (Compiler)

1992-01-01

This publication contains the proceedings of the Ninth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design held at Lake Tahoe, Nevada, during 4-7 Nov. 1991. Presentations were made in the following areas of composite structural design: perspectives in composites, design methodology, design applications, design criteria, supporting technology, damage tolerance, and manufacturing.

The Effects of Elevated Temperatures on the Response of Resins Under Dynamic and Static Loadings

NASA Technical Reports Server (NTRS)

Gilat, Amos

2005-01-01

The overall objective of the research is to experimentally study the combined effects of temperature and strain rate on the response of two resins that are commonly used for the matrix material in composites. The resins are loaded at various temperatures in shear and in tension over a wide range of strain rates. These two types of loadings provide an opportunity to examine also the effect that temperature might have on the effects of the hydrostatic stress component on the material response. The experimental data provide the information needed for NASA scientists for the development of a nonlinear, strain rate, and temperature dependent deformation and strength models for composites that can subsequently be used in design. This year effort was directed into the development and testing of the epoxy resin at elevated temperatures. Two types of epoxy resins were tested in shear at high strain rates of about 10(exp-4)/s and elevated temperatures of 50 and 8OC. The results show that the temperature significantly affects the response of epoxy.

Modeling and analysis of film composition on mechanical properties of maize starch based edible films.

PubMed

Prakash Maran, J; Sivakumar, V; Thirugnanasambandham, K; Kandasamy, S

2013-11-01

The present study investigates the influence of composition (content of maize starch (1-3 g), sorbitol (0.5-1.0 ml), agar (0.5-1.0 g) and tween-80 (0.1-0.5 ml)) on the mechanical properties (tensile strength, elongation, Young's modulus, puncture force and puncture deformation) of the maize starch based edible films using four factors with three level Box-Behnken design. The edible films were obtained by casting method. The results showed that, tween-80 increases the permeation of sorbitol in to the polymer matrix. Increasing concentration of sorbitol (hydrophilic nature and plasticizing effect of sorbitol) decreases the tensile strength, Young's modulus and puncture force of the films. The results were analyzed by Pareto analysis of variance (ANOVA) and second order polynomial models were obtained for all responses with high R(2) values (R(2)>0.95). 3D response surface plots were constructed to study the relationship between process variables and the responses. Copyright © 2013 Elsevier B.V. All rights reserved.

On Response Bias in the Face Congruency Effect for Internal and External Features

PubMed Central

Meinhardt, Günter; Meinhardt-Injac, Bozana; Persike, Malte

2017-01-01

Some years ago Cheung et al. (2008) proposed the complete design (CD) for measuring the failure of selective attention in composite objects. Since the CD is a fully balanced design, analysis of response bias may reveal potential effects of the experimental manipulation, the stimulus material, and/or attributes of the observers. Here we used the CD to prove whether external features modulate perception of internal features with the context congruency paradigm (Nachson et al., 1995; Meinhardt-Injac et al., 2010) in a larger sample of N = 303 subjects. We found a large congruency effect (Cohen's d = 1.78), which was attenuated by face inversion (d = 1.32). The congruency relation also strongly modulated response bias. In incongruent trials the proportion of “different” responses was much larger than in congruent trials (d = 0.79), which was again attenuated by face inversion (d = 0.43). Because in incongruent trials the wholes formed by integrating external and internal features are always different, while in congruent trials same and different wholes occur with the same frequency, a congruency related bias effect is expected from holistic integration. Our results suggest two behavioral markers of holistic processing in the context congruency paradigm: a performance advantage in congruent compared to incongruent trials, and a tendency toward more “different” responses in incongruent, compared to congruent trials. Since the results for both markers differed only quantitatively in upright and inverted presentation, our findings indicate no change of the face processing mode by picture plane rotation. A potential transfer to the composite face paradigm is discussed. PMID:29089880

Responses of stream microbes to multiple anthropogenic stressors in a mesocosm study.

PubMed

Nuy, Julia K; Lange, Anja; Beermann, Arne J; Jensen, Manfred; Elbrecht, Vasco; Röhl, Oliver; Peršoh, Derek; Begerow, Dominik; Leese, Florian; Boenigk, Jens

2018-08-15

Stream ecosystems are affected by multiple anthropogenic stressors worldwide. Even though effects of many single stressors are comparatively well studied, the effects of multiple stressors are difficult to predict. In particular bacteria and protists, which are responsible for the majority of ecosystem respiration and element flows, are infrequently studied with respect to multiple stressors responses. We conducted a stream mesocosm experiment to characterize the responses of single and multiple stressors on microbiota. Two functionally important stream habitats, leaf litter and benthic phototrophic rock biofilms, were exposed to three stressors in a full factorial design: fine sediment deposition, increased chloride concentration (salinization) and reduced flow velocity. We analyzed the microbial composition in the two habitat types of the mesocosms using an amplicon sequencing approach. Community analysis on different taxonomic levels as well as principle component analyses (PCoAs) based on realtive abundances of operational taxonomic units (OTUs) showed treatment specific shifts in the eukaryotic biofilm community. Analysis of variance (ANOVA) revealed that Bacillariophyta responded positively salinity and sediment increase, while the relative read abundance of chlorophyte taxa decreased. The combined effects of multiple stressors were mainly antagonistic. Therefore, the community composition in multiply stressed environments resembled the composition of the unstressed control community in terms of OTU occurrence and relative abundances. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Analysis for the Progressive Failure Response of Textile Composite Fuselage Frames

NASA Technical Reports Server (NTRS)

Johnson, Eric R.; Boitnott, Richard L. (Technical Monitor)

2002-01-01

A part of aviation accident mitigation is a crashworthy airframe structure, and an important measure of merit for a crashworthy structure is the amount of kinetic energy that can be absorbed in the crush of the structure. Prediction of the energy absorbed from finite element analyses requires modeling the progressive failure sequence. Progressive failure modes may include material degradation, fracture and crack growth, and buckling and collapse. The design of crashworthy airframe components will benefit from progressive failure analyses that have been validated by tests. The subject of this research is the development of a progressive failure analysis for a textile composite, circumferential fuselage frame subjected to a quasi-static, crash-type load. The test data for the frame are reported, and these data are used to develop and to validate methods for the progressive failure response.

Characterization of viscoelastic response and damping of composite materials used in flywheel rotors

NASA Astrophysics Data System (ADS)

Chen, Jianmin

The long-term goal for spacecraft flywheel systems with higher energy density at the system level requires new and innovative composite material concepts. Multi-Direction Composite (MDC) offers significant advantages over traditional filament-wound and multi-ring press-fit filament-wound wheels in providing higher energy density (i.e., less mass), better crack resistance, and enhanced safety. However there is a lack of systematic characterization for dynamic properties of MDC composite materials. In order to improve the flywheel materials reliability, durability and life time, it is very important to evaluate the time dependent aging effects and damping properties of MDC material, which are significant dynamic parameter for vibration and sound control, fatigue endurance, and impact resistance. The physical aging effects are quantified based on a set of creep curves measured at different aging time or different aging temperature. One parameter (tau) curve fit was proposed to represent the relationship of aging time and aging temperature between different master curves. The long term mechanical behavior was predicted by obtained master curves. The time and temperature shift factors of matrix were obtained from creep curves and the aging time shift rate were calculated. The aging effects on composite are obtained from experiments and compared with prediction. The mechanical quasi-behavior of MDC composite was analyzed. The correspondence principle was used to relate quasi-static elastic properties of composite materials to time-dependent properties of its constituent materials (i.e., fiber and matrix). The Prony series combined with the multi-data fitting method was applied to inverse Laplace transform and to calculate the time dependent stiffness matrix effectively. Accelerated time-dependent deformation of two flywheel rim designs were studied for a period equivalent to 31 years and are compared with hoop reinforcement only composite. Damping of pure resin and T700/epoxy composite lamina and laminate in longitudinal and transverse directions were investigated experimentally and analytically. The effect of aging on damping was also studied by placing samples at 60°C in an oven for extended periods. Damping master curves versus frequency were constructed from individual curves at different temperatures based on the Arrhenius equation. The damping response of the composite lamina was used to predict the response of laminate composites. Analytical results give close numerical values to experimental results from damping of cantilever beam laminated composite samples.

Combined effects of levels of protection and environmental variables at different spatial resolutions on fish assemblages in a marine protected area.

PubMed

Claudet, Joachim; García-Charton, José Antonio; Lenfant, Philippe

2011-02-01

The links between species-environment relations and species' responses to protection are unclear, but the objectives of marine protected areas (MPAs) are most likely to be achieved when those relations are known and inform MPA design. The components of a species' habitat vary with the spatial resolution of the area considered. We characterized areas at two resolutions: 250 m(2) (transect) and approximately 30,000 m(2) (seascape). We considered three categories of environmental variables: substrate type, bottom complexity, and depth. We sought to determine at which resolution habitat characteristics were a better predictor of abundance and species composition of fishes and whether the relations with environmental variables at either resolution affected species' responses to protection. Habitat features accounted for a larger proportion of spatial variation in species composition and abundances than differences in protection status. This spatial variation was explained best by habitat characteristics at the seascape level than at the transect level. Species' responses to protected areas were specific to particular seascape characteristics, primarily depth, and bottom complexity. Our method may be useful for prioritizing marine areas for protection, designing MPAs, and monitoring their effectiveness. It identified areas that provided natural shelter, areas acting as buffer zones, and areas where fish species were most responsive to protection. The identification of such areas is necessary for cost-effective establishment and monitoring of MPAs. ©2010 Society for Conservation Biology.

Monolithic composite “pressure + acceleration + temperature + infrared” sensor using a versatile single-sided “SiN/Poly-Si/Al” process-module.

PubMed

Ni, Zao; Yang, Chen; Xu, Dehui; Zhou, Hong; Zhou, Wei; Li, Tie; Xiong, Bin; Li, Xinxin

2013-01-16

We report a newly developed design/fabrication module with low-cost single-sided "low-stress-silicon-nitride (LS-SiN)/polysilicon (poly-Si)/Al" process for monolithic integration of composite sensors for sensing-network-node applications. A front-side surface-/bulk-micromachining process on a conventional Si-substrate is developed, featuring a multifunctional SiN/poly-Si/Al layer design for diverse sensing functions. The first "pressure + acceleration + temperature + infrared" (PATIR) composite sensor with the chip size of 2.5 mm × 2.5 mm is demonstrated. Systematic theoretical design and analysis methods are developed. The diverse sensing components include a piezoresistive absolute-pressure sensor (up to 700 kPa, with a sensitivity of 49 mV/MPa under 3.3 V supplied voltage), a piezoresistive accelerometer (±10 g, with a sensitivity of 66 μV/g under 3.3 V and a -3 dB bandwidth of 780 Hz), a thermoelectric infrared detector (with a responsivity of 45 V/W and detectivity of 3.6 × 107 cm·Hz1/2/W) and a thermistor (-25-120 °C). This design/fabrication module concept enables a low-cost monolithically-integrated "multifunctional-library" technique. It can be utilized as a customizable tool for versatile application-specific requirements, which is very useful for small-size, low-cost, large-scale sensing-network node developments.

Experimental design methods for bioengineering applications.

PubMed

Keskin Gündoğdu, Tuğba; Deniz, İrem; Çalışkan, Gülizar; Şahin, Erdem Sefa; Azbar, Nuri

2016-01-01

Experimental design is a form of process analysis in which certain factors are selected to obtain the desired responses of interest. It may also be used for the determination of the effects of various independent factors on a dependent factor. The bioengineering discipline includes many different areas of scientific interest, and each study area is affected and governed by many different factors. Briefly analyzing the important factors and selecting an experimental design for optimization are very effective tools for the design of any bioprocess under question. This review summarizes experimental design methods that can be used to investigate various factors relating to bioengineering processes. The experimental methods generally used in bioengineering are as follows: full factorial design, fractional factorial design, Plackett-Burman design, Taguchi design, Box-Behnken design and central composite design. These design methods are briefly introduced, and then the application of these design methods to study different bioengineering processes is analyzed.

In situ simultaneous strain and temperature measurement of adaptive composite materials using a fiber Bragg grating based sensor

NASA Astrophysics Data System (ADS)

Yoon, Hyuk-Jin; Costantini, Daniele M.; Michaud, Veronique; Limberger, Hans G.; Manson, Jan-Anders; Salathe, Rene P.; Kim, Chun-Gon; Hong, Chang-Sun

2005-05-01

An optical fiber sensor to simultaneously measure strain and temperature was designed and embedded into an adaptive composite laminate which exhibits a shape change upon thermal activation. The sensor is formed by two fiber Bragg gratings, which are written in optical fibers with different core dopants. The two gratings were spliced close to each other and a sensing element resulted with Bragg gratings of similar strain sensitivity but different response to temperature. This is due to the dependence of the fiber thermo-optic coefficient on core dopants and relative concentrations. The sensor was tested on an adaptive composite laminate made of unidirectional Kevlar-epoxy pre-preg plies. Several 150μm diameter pre-strained NiTiCu shape memory alloy wires were embedded in the composite laminate together with one fiber sensor. Simultaneous monitoring of strain and temperature during the curing process and activation in an oven was demonstrated.

A comparative study of gelatin and starch-based nano-composite films modified by nano-cellulose and chitosan for food packaging applications.

PubMed

Noorbakhsh-Soltani, S M; Zerafat, M M; Sabbaghi, S

2018-06-01

Environmental concerns have led to extensive research for replacing polymer-based food packaging with bio-nano-composites. In this study, incorporation of nano-cellulose into gelatin and starch matrices is investigated for this purpose. Chitosan is used to improve mechanical, anti-fungal and waterproof properties. Experiments are designed and analyzed using response surface methodology. Nano-Cellulose is synthesized via acid hydrolysis and incorporated in base matrices through wet processing. Also, tensile strength test, food preservation, transparency in visible and UV and water contact angle are performed on the nano-composite films. DSC/TGA and air permeability tests are also performed on the optimal films. The results show that increasing nano-cellulose composition to 10% leads to increase the tensile strength at break to 8121 MN/m 2 and decrease the elongation at break. Also, increasing chitosan composition from 5% to 30% can enhance food preservation up to 15 days. Copyright © 2018 Elsevier Ltd. All rights reserved.

Graphene Oxide-Polymer Composite Langmuir Films Constructed by Interfacial Thiol-Ene Photopolymerization

NASA Astrophysics Data System (ADS)

Luo, Xiaona; Ma, Kai; Jiao, Tifeng; Xing, Ruirui; Zhang, Lexin; Zhou, Jingxin; Li, Bingbing

2017-02-01

The effective synthesis and self-assembly of graphene oxide (GO) nanocomposites are of key importance for a broad range of nanomaterial applications. In this work, a one-step chemical strategy is presented to synthesize stable GO-polymer Langmuir composite films by interfacial thiol-ene photopolymerization at room temperature, without use of any crosslinking agents and stabilizing agents. It is discovered that photopolymerization reaction between thiol groups modified GO sheets and ene in polymer molecules is critically responsible for the formation of the composite Langmuir films. The film formed by Langmuir assembly of such GO-polymer composite films shows potential to improve the mechanical and chemical properties and promotes the design of various GO-based nanocomposites. Thus, the GO-polymer composite Langmuir films synthesized by interfacial thiol-ene photopolymerization with such a straightforward and clean manner, provide new alternatives for developing chemically modified GO-based hybrid self-assembled films and nanomaterials towards a range of soft matter and graphene applications.

Optimization of tribological behaviour on Al- coconut shell ash composite at elevated temperature

NASA Astrophysics Data System (ADS)

Siva Sankara Raju, R.; Panigrahi, M. K.; Ganguly, R. I.; Srinivasa Rao, G.

2018-02-01

In this study, determine the tribological behaviour of composite at elevated temperature i.e. 50 - 150 °C. The aluminium matrix composite (AMC) are prepared with compo casting route by volume of reinforcement of coconut shell ash (CSA) such as 5, 10 and 15%. Mechanical properties of composite has enhances with increasing volume of CSA. This study details to optimization of wear behaviour of composite at elevated temperatures. The influencing parameters such as temperature, sliding velocity and sliding distance are considered. The outcome response is wear rate (mm3/m) and coefficient of friction. The experiments are designed based on Taguchi [L9] array. All the experiments are considered as constant load of 10N. Analysis of variance (ANOVA) revealed that temperature is highest influencing factor followed by sliding velocity and sliding distance. Similarly, sliding velocity is most influencing factor followed by temperature and distance on coefficient of friction (COF). Finally, corroborates analytical and regression equation values by confirmation test.

Characterization and Analysis of Triaxially Braided Polymer Composites under Static and Impact Loads

NASA Technical Reports Server (NTRS)

Goldberg, Robert K.; Roberts, Gary D.; Blinzler, Brina J.; Kohlman, Lee W.; Binienda, Wieslaw K.

2012-01-01

In order to design impact resistant aerospace components made of triaxially-braided polymer matrix composite materials, a need exists to have reliable impact simulation methods and a detailed understanding of the material behavior. Traditional test methods and specimen designs have yielded unrealistic material property data due to material mechanisms such as edge damage. To overcome these deficiencies, various alternative testing geometries such as notched flat coupons have been examined to alleviate difficulties observed with standard test methods. The results from the coupon level tests have been used to characterize and validate a macro level finite element-based model which can be used to simulate the mechanical and impact response of the braided composites. In the analytical model, the triaxial braid unit cell is approximated by using four parallel laminated composites, each with a different fiber layup, which roughly simulates the braid architecture. In the analysis, each of these laminated composites is modeled as a shell element. Currently, each shell element is considered to be a smeared homogeneous material. Simplified micromechanics techniques and lamination theory are used to determine the equivalent stiffness properties of each shell element, and results from the coupon level tests on the braided composite are used to back out the strength properties of each shell element. Recent improvements to the model include the incorporation of strain rate effects into the model. Simulations of ballistic impact tests have been carried out to investigate and verify the analysis approach.

Composite materials for space applications

NASA Technical Reports Server (NTRS)

Rawal, Suraj P.; Misra, Mohan S.; Wendt, Robert G.

1990-01-01

The objectives of the program were to: generate mechanical, thermal, and physical property test data for as-fabricated advanced materials; design and fabricate an accelerated thermal cycling chamber; and determine the effect of thermal cycling on thermomechanical properties and dimensional stability of composites. In the current program, extensive mechanical and thermophysical property tests of various organic matrix, metal matrix, glass matrix, and carbon-carbon composites were conducted, and a reliable database was constructed for spacecraft material selection. Material property results for the majority of the as-fabricated composites were consistent with the predicted values, providing a measure of consolidation integrity attained during fabrication. To determine the effect of thermal cycling on mechanical properties, microcracking, and thermal expansion behavior, approximately 500 composite specimens were exposed to 10,000 cycles between -150 and +150 F. These specimens were placed in a large (18 cu ft work space) thermal cycling chamber that was specially designed and fabricated to simulate one year low earth orbital (LEO) thermal cycling in 20 days. With this rate of thermal cycling, this is the largest thermal cycling unit in the country. Material property measurements of the thermal cycled organic matrix composite laminate specimens exhibited less than 24 percent decrease in strength, whereas, the remaining materials exhibited less than 8 percent decrease in strength. The thermal expansion response of each of the thermal cycled specimens revealed significant reduction in hysteresis and residual strain, and the average CTE values were close to the predicted values.

Real-valued composite filters for correlation-based optical pattern recognition

NASA Technical Reports Server (NTRS)

Rajan, P. K.; Balendra, Anushia

1992-01-01

Advances in the technology of optical devices such as spatial light modulators (SLMs) have influenced the research and growth of optical pattern recognition. In the research leading to this report, the design of real-valued composite filters that can be implemented using currently available SLMs for optical pattern recognition and classification was investigated. The design of real-valued minimum average correlation energy (RMACE) filter was investigated. Proper selection of the phase of the output response was shown to reduce the correlation energy. The performance of the filter was evaluated using computer simulations and compared with the complex filters. It was found that the performance degraded only slightly. Continuing the above investigation, the design of a real filter that minimizes the output correlation energy and the output variance due to noise was developed. Simulation studies showed that this filter had better tolerance to distortion and noise compared to that of the RMACE filter. Finally, the space domain design of RMACE filter was developed and implemented on the computer. It was found that the sharpness of the correlation peak was slightly reduced but the filter design was more computationally efficient than the complex filter.

A comparative evaluation of piezoelectric sensors for acoustic emission-based impact location estimation and damage classification in composite structures

NASA Astrophysics Data System (ADS)

Uprety, Bibhisha; Kim, Sungwon; Mathews, V. John; Adams, Daniel O.

2015-03-01

Acoustic Emission (AE) based Structural Health Monitoring (SHM) is of great interest for detecting impact damage in composite structures. Within the aerospace industry the need to detect and locate these events, even when no visible damage is present, is important both from the maintenance and design perspectives. In this investigation, four commercially available piezoelectric sensors were evaluated for usage in an AE-based SHM system. Of particular interest was comparing the acoustic response of the candidate piezoelectric sensors for impact location estimations as well as damage classification resulting from the impact in fiber-reinforced composite structures. Sensor assessment was performed based on response signal characterization and performance for active testing at 300 kHz and steel-ball drop testing using both aluminum and carbon/epoxy composite plates. Wave mode velocities calculated from the measured arrival times were found to be in good agreement with predictions obtained using both the Disperse code and finite element analysis. Differences in the relative strength of the received wave modes, the overall signal strengths and signal-to-noise ratios were observed through the use of both active testing as well as passive steel-ball drop testing. Further comparative is focusing on assessing AE sensor performance for use in impact location estimation algorithms as well as detecting and classifying damage produced in composite structures due to impact events.

Field testing the Raman gas composition sensor for gas turbine operation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buric, M.; Chorpening, B.; Mullem, J.

2012-01-01

A gas composition sensor based on Raman spectroscopy using reflective metal lined capillary waveguides is tested under field conditions for feed-forward applications in gas turbine control. The capillary waveguide enables effective use of low powered lasers and rapid composition determination, for computation of required parameters to pre-adjust burner control based on incoming fuel. Tests on high pressure fuel streams show sub-second time response and better than one percent accuracy on natural gas fuel mixtures. Fuel composition and Wobbe constant values are provided at one second intervals or faster. The sensor, designed and constructed at NETL, is packaged for Class Imore » Division 2 operations typical of gas turbine environments, and samples gas at up to 800 psig. Simultaneous determination of the hydrocarbons methane, ethane, and propane plus CO, CO₂, H₂O, H₂, N₂, and O₂ are realized. The capillary waveguide permits use of miniature spectrometers and laser power of less than 100 mW. The capillary dimensions of 1 m length and 300 μm ID also enable a full sample exchange in 0.4 s or less at 5 psig pressure differential, which allows a fast response to changes in sample composition. Sensor operation under field operation conditions will be reported.« less

Optimization of process parameters for a quasi-continuous tablet coating system using design of experiments.

PubMed

Cahyadi, Christine; Heng, Paul Wan Sia; Chan, Lai Wah

2011-03-01

The aim of this study was to identify and optimize the critical process parameters of the newly developed Supercell quasi-continuous coater for optimal tablet coat quality. Design of experiments, aided by multivariate analysis techniques, was used to quantify the effects of various coating process conditions and their interactions on the quality of film-coated tablets. The process parameters varied included batch size, inlet temperature, atomizing pressure, plenum pressure, spray rate and coating level. An initial screening stage was carried out using a 2(6-1(IV)) fractional factorial design. Following these preliminary experiments, optimization study was carried out using the Box-Behnken design. Main response variables measured included drug-loading efficiency, coat thickness variation, and the extent of tablet damage. Apparent optimum conditions were determined by using response surface plots. The process parameters exerted various effects on the different response variables. Hence, trade-offs between individual optima were necessary to obtain the best compromised set of conditions. The adequacy of the optimized process conditions in meeting the combined goals for all responses was indicated by the composite desirability value. By using response surface methodology and optimization, coating conditions which produced coated tablets of high drug-loading efficiency, low incidences of tablet damage and low coat thickness variation were defined. Optimal conditions were found to vary over a large spectrum when different responses were considered. Changes in processing parameters across the design space did not result in drastic changes to coat quality, thereby demonstrating robustness in the Supercell coating process. © 2010 American Association of Pharmaceutical Scientists

Statistical optimization and fabrication of a press coated pulsatile dosage form to treat nocturnal acid breakthrough.

PubMed

Agarwal, Vaibhav; Bansal, Mayank

2013-08-01

Present work focuses on the use of mimosa seed gum to develop a drug delivery system making combined use of floating and pulsatile principles, for the chrono-prevention of nocturnal acid breakthrough. The desired aim was achieved by fabricating a floating delivery system bearing time - lagged coating of Mimosa pudica seed polymer for the programmed release of Famotidine. Response Surface Methodology was the statistical tool that was employed for experiment designing, mathematical model generation and optimization study. A 3(2) full factorial design was used in designing the experiment.% weight ratio of mimosa gum to hydroxy propyl methyl cellulose in the coating combination and the coating weight were the independent variables, whereas the lag time and the cumulative % drug release in 360 minutes were the observed responses. Results revealed that both the coating composition and the coating weight significantly affected the release of drug from the dosage form. The optimized formulation prepared according to the computer generated software, Design-Expert(®) deciphered response which were in close proximity with the experimental responses, thus confirming the robustness as well as accuracy of the predicted model for the utilization of natural polymer like mimosa seed gum for the chronotherapeutic treatment of nocturnal acid breakthrough.

Development of a Continuum Damage Mechanics Material Model of a Graphite-Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing Kevlar(Registered Trademark) Hybrid Fabric for Simulating the Impact Response of Energy Absorbing

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Littell, Justin D.

2017-01-01

This paper describes the development of input properties for a continuum damage mechanics based material model, Mat 58, within LS-DYNA(Registered Trademark) to simulate the response of a graphite-Kevlar(Registered Trademark) hybrid plain weave fabric. A limited set of material characterization tests were performed on the hybrid graphite-Kevlar(Registered Trademark) fabric. Simple finite element models were executed in LS-DYNA(Registered Trademark) to simulate the material characterization tests and to verify the Mat 58 material model. Once verified, the Mat 58 model was used in finite element models of two composite energy absorbers: a conical-shaped design, designated the "conusoid," fabricated of four layers of hybrid graphite-Kevlar(Registered Trademark) fabric; and, a sinusoidal-shaped foam sandwich design, designated the "sinusoid," fabricated of the same hybrid fabric face sheets with a foam core. Dynamic crush tests were performed on components of the two energy absorbers, which were designed to limit average vertical accelerations to 25- to 40-g, to minimize peak crush loads, and to generate relatively long crush stroke values under dynamic loading conditions. Finite element models of the two energy absorbers utilized the Mat 58 model that had been verified through material characterization testing. Excellent predictions of the dynamic crushing response were obtained.

Axiomatic Design and Fabrication of Composite Structures - Applications in Robots, Machine Tools, and Automobiles

NASA Astrophysics Data System (ADS)

Lee, Dai Gil; Suh, Nam Pyo

2005-11-01

The idea that materials can be designed to satisfy specific performance requirements is relatively new. With high-performance composites, however, the entire process of designing and fabricating a part can be worked out before manufacturing. The purpose of this book is to present an integrated approach to the design and manufacturing of products from advanced composites. It shows how the basic behavior of composites and their constitutive relationships can be used during the design stage, which minimizes the complexity of manufacturing composite parts and reduces the repetitive "design-build-test" cycle. Designing it right the first time is going to determine the competitiveness of a company, the reliability of the part, the robustness of fabrication processes, and ultimately, the cost and development time of composite parts. Most of all, it should expand the use of advanced composite parts in fields that use composites only to a limited extent at this time. To achieve these goals, this book presents the design and fabrication of novel composite parts made for machine tools and other applications like robots and automobiles. This book is suitable as a textbook for graduate courses in the design and fabrication of composites. It will also be of interest to practicing engineers learning about composites and axiomatic design. A CD-ROM is included in every copy of the book, containing Axiomatic CLPT software. This program, developed by the authors, will assist readers in calculating material properties from the microstructure of the composite. This book is part of the Oxford Series on Advanced Manufacturing.

Alginate/nanohydroxyapatite scaffolds with designed core/shell structures fabricated by 3D plotting and in situ mineralization for bone tissue engineering.

PubMed

Luo, Yongxiang; Lode, Anja; Wu, Chengtie; Chang, Jiang; Gelinsky, Michael

2015-04-01

Composite scaffolds, especially polymer/hydroxyapatite (HAP) composite scaffolds with predesigned structures, are promising materials for bone tissue engineering. Various methods including direct mixing of HAP powder with polymers or incubating polymer scaffolds in simulated body fluid for preparing polymer/HAP composite scaffolds are either uncontrolled or require long times of incubation. In this work, alginate/nano-HAP composite scaffolds with designed pore parameters and core/shell structures were fabricated using 3D plotting technique and in situ mineralization under mild conditions (at room temperature and without the use of any organic solvents). Light microscopy, scanning electron microscopy, microcomputer tomography, X-ray diffraction, and Fourier transform infrared spectroscopy were applied to characterize the fabricated scaffolds. Mechanical properties and protein delivery of the scaffolds were evaluated, as well as the cell response to the scaffolds by culturing human bone-marrow-derived mesenchymal stem cells (hBMSC). The obtained data indicate that this method is suitable to fabricate alginate/nano-HAP composite scaffolds with a layer of nano-HAP, coating the surface of the alginate strands homogeneously and completely. The surface mineralization enhanced the mechanical properties and improved the cell attachment and spreading, as well as supported sustaining protein release, compared to pure alginate scaffolds without nano-HAP shell layer. The results demonstrated that the method provides an interesting option for bone tissue engineering application.

Composite scaffolds for osteochondral repair obtained by combination of additive manufacturing, leaching processes and hMSC-CM functionalization.

PubMed

Díaz Lantada, Andrés; Alarcón Iniesta, Hernán; García-Ruíz, Josefa Predestinación

2016-02-01

Articular repair is a relevant and challenging area for the emerging fields of tissue engineering and biofabrication. The need of significant gradients of properties, for the promotion of osteochondral repair, has led to the development of several families of composite biomaterials and scaffolds, using different effective approaches, although a perfect solution has not yet been found. In this study we present the design, modeling, rapid manufacturing and in vitro testing of a composite scaffold aimed at osteochondral repair. The presented composite scaffold stands out for having a functional gradient of density and stiffness in the bony phase, obtained in titanium by means of computer-aided design combined with additive manufacture using selective laser sintering. The chondral phase is obtained by sugar leaching, using a PDMS matrix and sugar as porogen, and is joined to the bony phase during the polymerization of PDMS, therefore avoiding the use of supporting adhesives or additional intermediate layers. The mechanical performance of the construct is biomimetic and the stiffness values of the bony and chondral phases can be tuned to the desired applications, by means of controlled modifications of different parameters. A human mesenchymal stem cell (h-MSC) conditioned medium (CM) is used for improving scaffold response. Cell culture results provide relevant information regarding the viability of the composite scaffolds used. Copyright © 2015 Elsevier B.V. All rights reserved.

Probability-based methodology for buckling investigation of sandwich composite shells with and without cut-outs

NASA Astrophysics Data System (ADS)

Alfano, M.; Bisagni, C.

2017-01-01

The objective of the running EU project DESICOS (New Robust DESign Guideline for Imperfection Sensitive COmposite Launcher Structures) is to formulate an improved shell design methodology in order to meet the demand of aerospace industry for lighter structures. Within the project, this article discusses the development of a probability-based methodology developed at Politecnico di Milano. It is based on the combination of the Stress-Strength Interference Method and the Latin Hypercube Method with the aim to predict the bucking response of three sandwich composite cylindrical shells, assuming a loading condition of pure compression. The three shells are made of the same material, but have different stacking sequence and geometric dimensions. One of them presents three circular cut-outs. Different types of input imperfections, treated as random variables, are taken into account independently and in combination: variability in longitudinal Young's modulus, ply misalignment, geometric imperfections, and boundary imperfections. The methodology enables a first assessment of the structural reliability of the shells through the calculation of a probabilistic buckling factor for a specified level of probability. The factor depends highly on the reliability level, on the number of adopted samples, and on the assumptions made in modeling the input imperfections. The main advantage of the developed procedure is the versatility, as it can be applied to the buckling analysis of laminated composite shells and sandwich composite shells including different types of imperfections.

Response surface methodology as an approach to determine optimal activities of lipase entrapped in sol-gel matrix using different vegetable oils.

PubMed

Pinheiro, Rubiane C; Soares, Cleide M F; de Castro, Heizir F; Moraes, Flavio F; Zanin, Gisella M

2008-03-01

The conditions for maximization of the enzymatic activity of lipase entrapped in sol-gel matrix were determined for different vegetable oils using an experimental design. The effects of pH, temperature, and biocatalyst loading on lipase activity were verified using a central composite experimental design leading to a set of 13 assays and the surface response analysis. For canola oil and entrapped lipase, statistical analyses showed significant effects for pH and temperature and also the interactions between pH and temperature and temperature and biocatalyst loading. For the olive oil and entrapped lipase, it was verified that the pH was the only variable statistically significant. This study demonstrated that response surface analysis is a methodology appropriate for the maximization of the percentage of hydrolysis, as a function of pH, temperature, and lipase loading.

Subcritical water liquefaction of oil palm fruit press fiber in the presence of sodium hydroxide: an optimisation study using response surface methodology.

PubMed

Mazaheri, Hossein; Lee, Keat Teong; Bhatia, Subhash; Mohamed, Abdul Rahman

2010-12-01

Thermal decomposition of oil palm fruit press fiber (FPF) into a liquid product (LP) was achieved using subcritical water treatment in the presence of sodium hydroxide in a high pressure batch reactor. This study uses experimental design and process optimisation tools to maximise the LP yield using response surface methodology (RSM) with central composite rotatable design (CCRD). The independent variables were temperature, residence time, particle size, specimen loading, and additive loading. The mathematical model that was developed fit the experimental results well for all of the response variables that were studied. The optimal conditions were found to be a temperature of 551 K, a residence time of 40 min, a particle size of 710-1000 microm, a specimen loading of 5 g, and a additive loading of 9 wt.% to achieve a LP yield of 76.16%. 2010 Elsevier Ltd. All rights reserved.

Optimization of ultrasound-assisted extraction of crude oil from winter melon (Benincasa hispida) seed using response surface methodology and evaluation of its antioxidant activity, total phenolic content and fatty acid composition.

PubMed

Bimakr, Mandana; Rahman, Russly Abdul; Taip, Farah Saleena; Adzahan, Noranizan Mohd; Sarker, Md Zaidul Islam; Ganjloo, Ali

2012-10-08

In the present study, ultrasound-assisted extraction of crude oil from winter melon seeds was investigated through response surface methodology (RSM). Process variables were power level (25-75%), temperature (45-55 °C) and sonication time (20-40 min). It was found that all process variables have significant (p < 0.05) effects on the response variable. A central composite design (CCD) was used to determine the optimum process conditions. Optimal conditions were identified as 65% power level, 52 °C temperature and 36 min sonication time for maximum crude yield (108.62 mg-extract/g-dried matter). The antioxidant activity, total phenolic content and fatty acid composition of extract obtained under optimized conditions were determined and compared with those of oil obtained by the Soxhlet method. It was found that crude extract yield (CEY) of ultrasound-assisted extraction was lower than that of the Soxhlet method, whereas antioxidant activity and total phenolic content of the extract obtained by ultrasound-assisted extraction were clearly higher than those of the Soxhlet extract. Furthermore, both extracts were rich in unsaturated fatty acids. The major fatty acids of the both extracts were linoleic acid and oleic acid.

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation.

PubMed

Chen, Jian Z; Darhuber, Anton A; Troian, Sandra M; Wagner, Sigurd

2004-10-01

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable width design, allowing for wider central electrodes, increases the capacitive signal for liquid structures with non-uniform height profiles. The capacitive resolution and time response of the current design is approximately 0.03 pF and 10 ms, respectively, which makes possible a number of sensing functions for nanoliter droplets. These include detection of droplet position, size, composition or percentage water uptake for hygroscopic liquids. Its rapid response time allows measurements of the rate of mass loss in evaporating droplets.

DNA nanotechnology-based composite-type gold nanoparticle-immunostimulatory DNA hydrogel for tumor photothermal immunotherapy.

PubMed

Yata, Tomoya; Takahashi, Yuki; Tan, Mengmeng; Nakatsuji, Hirotaka; Ohtsuki, Shozo; Murakami, Tatsuya; Imahori, Hiroshi; Umeki, Yuka; Shiomi, Tomoki; Takakura, Yoshinobu; Nishikawa, Makiya

2017-11-01

Success of tumor photothermal immunotherapy requires a system that induces heat stress in cancer cells and enhances strong anti-tumor immune responses. Here, we designed a composite-type immunostimulatory DNA hydrogel consisting of a hexapod-like structured DNA (hexapodna) with CpG sequences and gold nanoparticles. Mixing of the properly designed hexapodna and oligodeoxynucleotide-modified gold nanoparticles resulted in the formation of composite-type gold nanoparticle-DNA hydrogels. Laser irradiation of the hydrogel resulted in the release of hexapodna, which efficiently stimulated immune cells to release proinflammatory cytokines. Then, EG7-OVA tumor-bearing mice received an intratumoral injection of a gold nanoparticle-DNA hydrogel, followed by laser irradiation at 780 nm. This treatment increased the local temperature and the mRNA expression of heat shock protein 70 in the tumor tissue, increased tumor-associated antigen-specific IgG levels in the serum, and induced tumor-associated antigen-specific interferon-γ production from splenocytes. Moreover, the treatment significantly retarded the tumor growth and extended the survival of the tumor-bearing mice. Copyright © 2017 Elsevier Ltd. All rights reserved.

Advanced Environmental Barrier Coating Development for SiC-SiC Ceramic Matrix Composite Components

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Harder, Bryan; Hurst, Janet B.; Halbig, Michael Charles; Puleo, Bernadette J.; Costa, Gustavo; Mccue, Terry R.

2017-01-01

This presentation reviews the NASA advanced environmental barrier coating (EBC) system development for SiC-SiC Ceramic Matrix Composite (CMC) combustors particularly under the NASA Environmentally Responsible Aviation, Fundamental Aeronautics and Transformative Aeronautics Concepts Programs. The emphases have been placed on the current design challenges of the 2700-3000F capable environmental barrier coatings for low NOX emission combustors for next generation turbine engines by using advanced plasma spray based processes, and the coating processing and integration with SiC-SiC CMCs and component systems. The developments also have included candidate coating composition system designs, degradation mechanisms, performance evaluation and down-selects; the processing optimizations using TriplexPro Air Plasma Spray Low Pressure Plasma Spray (LPPS), Plasma Spray Physical Vapor Deposition and demonstration of EBC-CMC systems. This presentation also highlights the EBC-CMC system temperature capability and durability improvements under the NASA development programs, as demonstrated in the simulated engine high heat flux, combustion environments, in conjunction with high heat flux, mechanical creep and fatigue loading testing conditions.

Simulating the Response of a Composite Honeycomb Energy Absorber. Part 2; Full-Scale Impact Testing

NASA Technical Reports Server (NTRS)

Fasanella, Edwin L.; Annett, Martin S.; Jackson, Karen E.; Polanco, Michael A.

2012-01-01

NASA has sponsored research to evaluate an externally deployable composite honeycomb designed to attenuate loads in the event of a helicopter crash. The concept, designated the Deployable Energy Absorber (DEA), is an expandable Kevlar(Registered TradeMark) honeycomb. The DEA has a flexible hinge that allows the honeycomb to be stowed collapsed until needed during an emergency. Evaluation of the DEA began with material characterization of the Kevlar(Registered TradeMark)-129 fabric/epoxy, and ended with a full-scale crash test of a retrofitted MD-500 helicopter. During each evaluation phase, finite element models of the test articles were developed and simulations were performed using the dynamic finite element code, LS-DYNA(Registered TradeMark). The paper will focus on simulations of two full-scale impact tests involving the DEA, a mass-simulator and a full-scale crash of an instrumented MD-500 helicopter. Isotropic (MAT24) and composite (MAT58) material models, which were assigned to DEA shell elements, were compared. Based on simulations results, the MAT58 model showed better agreement with test.

Simulations of a Thin Sampling Calorimeter with GEANT/FLUKA

NASA Technical Reports Server (NTRS)

Lee, Jeongin; Watts, John; Howell, Leonard; Rose, M. Franklin (Technical Monitor)

2000-01-01

The Advanced Cosmic-ray Composition Experiment for the Space Station (ACCESS) will investigate the origin, composition and acceleration mechanism of cosmic rays by measuring the elemental composition of the cosmic rays up to 10(exp 15) eV. These measurements will be made with a thin ionization calorimeter and a transition radiation detector. This paper reports studies of a thin sampling calorimeter concept for the ACCESS thin ionization calorimeter. For the past year, a Monte Carlo simulation study of a Thin Sampling Calorimeter (TSC) design has been conducted to predict the detector performance and to design the system for achieving the ACCESS scientific objectives. Simulation results show that the detector energy resolution function resembles a Gaussian distribution and the energy resolution of TSC is about 40%. In addition, simulations of the detector's response to an assumed broken power law cosmic ray spectra in the region where the 'knee' of the cosmic ray spectrum occurs have been conducted and clearly show that a thin sampling calorimeter can provide sufficiently accurate estimates of the spectral parameters to meet the science requirements of ACCESS. n

Designing safer composite helmets to reduce rotational accelerations during oblique impacts.

PubMed

Mosleh, Yasmine; Cajka, Martin; Depreitere, Bart; Vander Sloten, Jos; Ivens, Jan

2018-05-01

Oblique impact is the most common accident situation that occupants in traffic accidents or athletes in professional sports experience. During oblique impact, the human head is subjected to a combination of linear and rotational accelerations. Rotational movement is known to be responsible for traumatic brain injuries. In this article, composite foam with a column/matrix composite configuration is proposed for head protection applications to replace single-layer uniform foam, to better attenuate rotational movement of the head during oblique impacts. The ability of composite foam in the mitigation of rotational head movement is studied by performing finite element (FE) simulations of oblique impact on flat and helmet shape specimens. The performance of composite foam with respect to parameters such as compliance of the matrix foam and the number, size and cross-sectional shape of the foam columns is explored in detail, and subsequently an optimized structure is proposed. The simulation results show that using composite foam instead of single-layer foam, the rotational acceleration and velocity of the headform can be significantly reduced. The parametric study indicates that using a more compliant matrix foam and by increasing the number of columns in the composite foam configuration, the rotation can be further mitigated. This was confirmed by experimental results. The simulation results were also analyzed based on global head injury criteria such as head injury criterion, rotational injury criterion, brain injury criterion and generalized acceleration model for brain injury threshold which further confirmed the superior performance of composite foam versus single-layer homogeneous expanded polystyrene foam. The findings of simulations give invaluable information for design of protective helmets or, for instance, headliners for the automotive industry.

Application of response surface methodology for optimization of polygalacturonase production by Aspergillus niger.

PubMed

Yadav, Kaushlesh K; Garg, Neelima; Kumar, Devendra; Kumar, Sanjay; Singh, Achal; Muthukumar, M

2015-01-01

Polygalacturonase (PG) degrades pectin into D-galacturonic acid monomers and is used widely in food industry especially for juice clarification. In the present study,. fermentation conditions for polygalacturonase production by Asgergillus niger NAIMCCF-02958, using mango peel as substrate, were optimized using the 2(3) factorial design with central composite rotatable experimental design (CCRD) of response surface methodology (RSM). The maximum PG activity 723.66 U g(-1) was achieved under pH 4.0, temperature 30 degrees C and 2% inoculum by response surface curve. The experimental value of PG activity wkas higher 607.65 U g(-1) than the predicted value 511.75 U g(-1). Under the proposed optimized conditions, the determination coefficient (R2) was equal to 0.66 indicating that the model could explain 66% of the total variation as well as establish the relationship between the variables and the responses. ANOVA analysis and the three dimensional plots also confirmed interactions among the parameters.

Blast protection of infrastructure using advanced composites

NASA Astrophysics Data System (ADS)

Brodsky, Evan

This research was a systematic investigation detailing the energy absorption mechanisms of an E-glass web core composite sandwich panel subjected to an impulse loading applied orthogonal to the facesheet. Key roles of the fiberglass and polyisocyanurate foam material were identified, characterized, and analyzed. A quasi-static test fixture was used to compressively load a unit cell web core specimen machined from the sandwich panel. The web and foam both exhibited non-linear stress-strain responses during axial compressive loading. Through several analyses, the composite web situated in the web core had failed in axial compression. Optimization studies were performed on the sandwich panel unit cell in order to maximize the energy absorption capabilities of the web core. Ultimately, a sandwich panel was designed to optimize the energy dissipation subjected to through-the-thickness compressive loading.

Nitrite sensing composite systems based on a core-shell emissive-superamagnetic structure: Construction, characterization and sensing behavior

NASA Astrophysics Data System (ADS)

Yang, Yan; Liu, Liang; Zha, Jianhua; Yuan, Ningyi

2017-04-01

Two recyclable nitrite sensing composite samples were designed and constructed through a core-shell structure, with Fe3O4 nanoparticles as core, silica molecular sieve MCM-41 as shell and two rhodamine derivatives as chemosensors, respectively. These samples and their structure were identified with their electron microscopy images, N2 adsorption/desorption isotherms, magnetic response, IR spectra and thermogravimetric analysis. Their nitrite sensing behavior was discussed based on emission intensity quenching, their limit of detection was found as low as 1.2 μM. Further analysis suggested a static sensing mechanism between nitrite and chemosensors through an additive reaction between NO+ and chemosensors. After finishing their nitrite sensing, these composite samples and their emission could be recycled and recovered by sulphamic acid.

Optimization of fermentation medium for the production of atrazine degrading strain Acinetobacter sp. DNS(32) by statistical analysis system.

PubMed

Zhang, Ying; Wang, Yang; Wang, Zhi-Gang; Wang, Xi; Guo, Huo-Sheng; Meng, Dong-Fang; Wong, Po-Keung

2012-01-01

Statistical experimental designs provided by statistical analysis system (SAS) software were applied to optimize the fermentation medium composition for the production of atrazine-degrading Acinetobacter sp. DNS(32) in shake-flask cultures. A "Plackett-Burman Design" was employed to evaluate the effects of different components in the medium. The concentrations of corn flour, soybean flour, and K(2)HPO(4) were found to significantly influence Acinetobacter sp. DNS(32) production. The steepest ascent method was employed to determine the optimal regions of these three significant factors. Then, these three factors were optimized using central composite design of "response surface methodology." The optimized fermentation medium composition was composed as follows (g/L): corn flour 39.49, soybean flour 25.64, CaCO(3) 3, K(2)HPO(4) 3.27, MgSO(4)·7H(2)O 0.2, and NaCl 0.2. The predicted and verifiable values in the medium with optimized concentration of components in shake flasks experiments were 7.079 × 10(8) CFU/mL and 7.194 × 10(8) CFU/mL, respectively. The validated model can precisely predict the growth of atrazine-degraing bacterium, Acinetobacter sp. DNS(32).

Improved antimicrobial compound production by a new isolate Streptomyces hygroscopicus MTCC 4003 using Plackett-Burman design and response Surface methodology.

PubMed

Singh, Neha; Rai, Vibhuti

2012-01-01

An active strain, isolated from soil of Chhattisgarh, India, showed broad-spectrum antimicrobial activity against various pathogenic bacteria and fungi in glucose soybean meal broth. Strain was characterized as Streptomyces hygroscopicus MTCC 4003 based on 16S rRNA sequencing from Microbial Type culture Collection (MTCC), IMTECH, Chandigarh, India. Identification of the purified antimicrobial compound was done by using Infra-red (IR), Mass, Ultraviolet (UV), 1H and 13C nuclear magnetic resonance (NMR) spectra. Plackett-Burman design (PBD) and response surface methodology (RSM) methods were used for the optimization of antibiotic production. Effects of the four medium components soybean meal, glucose, CaCO3 and MgSO4 showed positive effect on antibiotic production, were investigated with the help of PBD. The individual and interaction effects of the selected variables were determined by RSM using central composite design (CCD). Applying statistical design, antibiotic production was improved nearly ten times (412 mg/L) compared with unoptimized production medium (37 mg/L).

Defatted flaxseed meal incorporated corn-rice flour blend based extruded product by response surface methodology.

PubMed

Ganorkar, Pravin M; Patel, Jhanvi M; Shah, Vrushti; Rangrej, Vihang V

2016-04-01

Considering the evidence of flaxseed and its defatted flaxseed meal (DFM) for human health benefits, response surface methodology (RSM) based on three level four factor central composite rotatable design (CCRD) was employed for the development of DFM incorporated corn - rice flour blend based extruded snack. The effect of DFM fortification (7.5-20 %), moisture content of feed (14-20 %, wb), extruder barrel temperature (115-135 °C) and screw speed (300-330 RPM) on expansion ratio (ER), breaking strength (BS), overall acceptability (OAA) score and water solubility index (WSI) of extrudates were investigated using central composite rotatable design (CCRD). Significant regression models explained the effect of considered variables on all responses. DFM incorporation level was found to be most significant independent variable affecting on extrudates characteristics followed by extruder barrel temperature and then screw rpm. Feed moisture content did not affect extrudates characteristics. As DFM level increased (7.5 % to 20 %), ER and OAA value decreased. However, BS and WSI values were found to increase with increase in DFM level. Based on the defined criteria for numerical optimization, the combination for the production of DFM incorporated extruded snack with desired sensory attributes was achieved by incorporating 10 % DFM (replacing rice flour in flour blend) and by keeping 20 % moisture content, 312 screw rpm and 125 °C barrel temperature.

Influence of Hesperidin on the Systemic and Intestinal Rat Immune Response

PubMed Central

Camps-Bossacoma, Mariona; Franch, Àngels; Pérez-Cano, Francisco J.; Castell, Margarida

2017-01-01

Polyphenols, widely found in edible plants, influence the immune system. Nevertheless, the immunomodulatory properties of hesperidin, the predominant flavanone in oranges, have not been deeply studied. To establish the effect of hesperidin on in vivo immune response, two different conditions of immune system stimulations in Lewis rats were applied. In the first experimental design, rats were intraperitoneally immunized with ovalbumin (OVA) plus Bordetella pertussis toxin and alum as the adjuvants, and orally given 100 or 200 mg/kg hesperidin. In the second experimental design, rats were orally sensitized with OVA together with cholera toxin and fed a diet containing 0.5% hesperidin. In the first approach, hesperidin administration changed mesenteric lymph node lymphocyte (MLNL) composition, increasing the TCRαβ+ cell percentage and decreasing that of B lymphocytes. Furthermore, hesperidin enhanced the interferon (IFN)-γ production in stimulated MLNL. In the second approach, hesperidin intake modified the lymphocyte composition in the intestinal epithelium (TCRγδ+ cells) and the lamina propria (TCRγδ+, CD45RA+, natural killer, natural killer T, TCRαβ+CD4+, and TCRαβ+CD8+ cells). Nevertheless, hesperidin did not modify the level of serum anti-OVA antibodies in either study. In conclusion, hesperidin does possess immunoregulatory properties in the intestinal immune response, but this effect is not able to influence the synthesis of specific antibodies. PMID:28587283

Skylab

NASA Image and Video Library

1973-01-01

This chart describes Skylab's Extreme Ultraviolet (XUV) Coronal Spectroheliograph, one of the eight Apollo Telescope Mount facilities. It was designed to sequentially photograph the solar chromosphere and corona in selected ultraviolet wavelengths . The instrument also obtained information about composition, temperature, energy conversion and transfer, and plasma processes of the chromosphere and lower corona. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Real time acousto-ultrasonic NDE technique for monitoring damage in ceramic composites under dynamic loads

NASA Technical Reports Server (NTRS)

Tiwari, Anil

1995-01-01

Research effort was directed towards developing a near real-time, acousto-ultrasonic (AU), nondestructive evaluation (NDE) tool to study the failure mechanisms of ceramic composites. Progression of damage is monitored in real-time by observing the changes in the received AU signal during the actual test. During the real-time AU test, the AU signals are generated and received by the AU transducers attached to the specimen while it is being subjected to increasing quasi-static loads or cyclic loads (10 Hz, R = 1.0). The received AU signals for 64 successive pulses were gated in the time domain (T = 40.96 micro sec) and then averaged every second over ten load cycles and stored in a computer file during fatigue tests. These averaged gated signals are representative of the damage state of the specimen at that point of its fatigue life. This is also the first major attempt in the development and application of real-time AU for continuously monitoring damage accumulation during fatigue without interrupting the test. The present work has verified the capability of the AU technique to assess the damage state in silicon carbide/calcium aluminosilicate (SiC/CAS) and silicon carbide/ magnesium aluminosilicate (SiC/MAS) ceramic composites. Continuous monitoring of damage initiation and progression under quasi-static ramp loading in tension to failure of unidirectional and cross-ply SiC/CAS and quasi-isotropic SiC/MAS ceramic composite specimens at room temperature was accomplished using near real-time AU parameters. The AU technique was shown to be able to detect the stress levels for the onset and saturation of matrix cracks, respectively. The critical cracking stress level is used as a design stress for brittle matrix composites operating at elevated temperatures. The AU technique has found that the critical cracking stress level is 10-15% below the level presently obtained for design purposes from analytical models. An acousto-ultrasonic stress-strain response (AUSSR) model for unidirectional and cross-ply ceramic composites was formulated. The AUSSR model predicts the strain response to increasing stress levels using real-time AU data and classical laminated plate theory. The Weibull parameters of the AUSSR model are used to calculate the design stress for thermo-structural applications. Real-time AU together with the AUSSR model was used to study the failure mechanisms of SiC/CAS ceramic composites under static and fatigue loading. An S-N curve was generated for a cross-ply SiC/CAS ceramic composite material. The AU results are corroborated and complemented by other NDE techniques, namely, in-situ optical microscope video recordings and edge replication.

Optimization of the preparation conditions of ceramic products using drinking water treatment sludges.

PubMed

Zamora, R M Ramirez; Ayala, F Espesel; Garcia, L Chavez; Moreno, A Duran; Schouwenaars, R

2008-11-01

The aim of this work is to optimize, via Response Surface Methodology, the values of the main process parameters for the production of ceramic products using sludges obtained from drinking water treatment in order to valorise them. In the first experimental stage, sludges were collected from a drinking water treatment plant for characterization. In the second stage, trials were carried out to elaborate thin cross-section specimens and fired bricks following an orthogonal central composite design of experiments with three factors (sludge composition, grain size and firing temperature) and five levels. The optimization parameters (Y(1)=shrinking by firing (%), Y(2)=water absorption (%), Y(3)=density (g/cm(3)) and Y(4)=compressive strength (kg/cm(2))) were determined according to standardized analytical methods. Two distinct physicochemical processes were active during firing at different conditions in the experimental design, preventing the determination of a full response surface, which would allow direct optimization of production parameters. Nevertheless, the temperature range for the production of classical red brick was closely delimitated by the results; above this temperature, a lightweight ceramic with surprisingly high strength was produced, opening possibilities for the valorisation of a product with considerably higher added value than what was originally envisioned.

Response Surface Modeling of Combined-Cycle Propulsion Components using Computational Fluid Dynamics

NASA Technical Reports Server (NTRS)

Steffen, C. J., Jr.

2002-01-01

Three examples of response surface modeling with CFD are presented for combined cycle propulsion components. The examples include a mixed-compression-inlet during hypersonic flight, a hydrogen-fueled scramjet combustor during hypersonic flight, and a ducted-rocket nozzle during all-rocket flight. Three different experimental strategies were examined, including full factorial, fractionated central-composite, and D-optimal with embedded Plackett-Burman designs. The response variables have been confined to integral data extracted from multidimensional CFD results. Careful attention to uncertainty assessment and modeling bias has been addressed. The importance of automating experimental setup and effectively communicating statistical results are emphasized.

Design concepts and options for the Thermal Infrared Imager (TIRI) as part of ESA's Asteroid Impact Mission.

NASA Astrophysics Data System (ADS)

Bowles, Neil; Calcutt, Simon; Licandro, Javier; Reyes, Marcos; Delbo, Marco; Donaldson Hanna, Kerri; Arnold, Jessica; Howe, Chris

2016-04-01

ESA's Asteroid Impact Mission (AIM) is being studied as part of the joint ESA/NASA AIDA mission for launch in 2020. AIDA's primary mission is to investigate the effect of a kinetic impactor on the secondary component of the binary asteroid 65803 Didymos in late 2022. AIM will characterise the Didymos system and monitor the response of the binary system to the impact. A multi-spectral, thermal-infrared imaging instrument (TIRI) will be an essential component of AIM's remote sensing payload, as it will provide key information on the nature of the surfaces (e.g. presence or absence of materials, degree of compaction, and rock abundance of the regolith) of both components in the Didymos system. The temperature maps provided by TIRI will be important for navigation and spacecraft health and safety for proximity/lander operations. By measuring the asteroids' diurnal thermal responses (thermal inertia) and their surface compositions via spectral signatures, TIRI will provide information on the origin and evolution of the binary system. In this presentation we will discuss possible instrument design for TIRI, exploring options that include imaging spectroscopy to broadband imaging. By using thermal models and compositional analogues of the Didymos system we will show how the performance of each design option compares to the wider scientific goals of the AIDA/AIM mission.

Optimization of radiation treatment of ginger ( Zingiber officinale) rhizomes using response surface methodology

NASA Astrophysics Data System (ADS)

Nketsia-Tabiri, Josephine

1998-06-01

The effects of pre-irradiation storage time (7-21 days), radiation dose (0-75 Gy) and post-irradiation storage time (2-20 weeks) on sprouting, wrinkling and weight loss of ginger was investigated using a central composite rotatable design. Predictive models developed for all three responses were highly significant. Weight loss and wrinkling decreased as pre-irradiation storage time increased. Dose and post-irradiation storage time had significant interactive effects on weight loss and sprouting. Processing conditions for achieving minimal sprouting resulted in maximum weight loss and wrinkling.

Tungsten fiber reinforced superalloy composite high temperature component design considerations

NASA Technical Reports Server (NTRS)

Winsa, E. A.

1982-01-01

Tungsten fiber reinforced superalloy composites (TFRS) are intended for use in high temperature turbine components. Current turbine component design methodology is based on applying the experience, sometimes semiempirical, gained from over 30 years of superalloy component design. Current composite component design capability is generally limited to the methodology for low temperature resin matrix composites. Often the tendency is to treat TFRS as just another superalloy or low temperature composite. However, TFRS behavior is significantly different than that of superalloys, and the high environment adds consideration not common in low temperature composite component design. The methodology used for preliminary design of TFRS components are described. Considerations unique to TFRS are emphasized.

Designing for fiber composite structural durability in hygrothermomechanical environment

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1985-01-01

A methodology is described which can be used to design/analyze fiber composite structures subjected to complex hygrothermomechanical environments. This methodology includes composite mechanics and advanced structural analysis methods (finite element). Select examples are described to illustrate the application of the available methodology. The examples include: (1) composite progressive fracture; (2) composite design for high cycle fatigue combined with hot-wet conditions; and (3) general laminate design.

Post-cracking characteristics of high performance fiber reinforced cementitious composites

NASA Astrophysics Data System (ADS)

Suwannakarn, Supat W.

The application of high performance fiber reinforced cement composites (HPFRCC) in structural systems depends primarily on the material's tensile response, which is a direct function of fiber and matrix characteristics, the bond between them, and the fiber content or volume fraction. The objective of this dissertation is to evaluate and model the post-cracking behavior of HPFRCC. In particular, it focused on the influential parameters controlling tensile behavior and the variability associated with them. The key parameters considered include: the stress and strain at first cracking, the stress and strain at maximum post-cracking, the shape of the stress-strain or stress-elongation response, the multiple cracking process, the shape of the resistance curve after crack localization, the energy associated with the multiple cracking process, and the stress versus crack opening response of a single crack. Both steel fibers and polymeric fibers, perceived to have the greatest potential for current commercial applications, are considered. The main variables covered include fiber type (Torex, Hooked, PVA, and Spectra) and fiber volume fraction (ranging from 0.75% to 2.0%). An extensive experimental program is carried out using direct tensile tests and stress-versus crack opening displacement tests on notched tensile prisms. The key experimental results were analysed and modeled using simple prediction equations which, combined with a composite mechanics approach, allowed for predicting schematic simplified stress-strain and stress-displacement response curves for use in structural modeling. The experimental data show that specimens reinforced with Torex fibers performs best, follows by Hooked and Spectra fibers, then PVA fibers. Significant variability in key parameters was observed througout suggesting that variability must be studied further. The new information obtained can be used as input for material models for finite element analysis and can provide greater confidence in using the HPFRC composites in structural applications. It also provides a good foundation to integrate these composites in conventional structural analysis and design.

A BASIS FOR MODIFYING THE TANK 12 COMPOSITE SAMPLING DESIGN

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shine, G.

The SRR sampling campaign to obtain residual solids material from the Savannah River Site (SRS) Tank Farm Tank 12 primary vessel resulted in obtaining appreciable material in all 6 planned source samples from the mound strata but only in 5 of the 6 planned source samples from the floor stratum. Consequently, the design of the compositing scheme presented in the Tank 12 Sampling and Analysis Plan, Pavletich (2014a), must be revised. Analytical Development of SRNL statistically evaluated the sampling uncertainty associated with using various compositing arrays and splitting one or more samples for compositing. The variance of the simple meanmore » of composite sample concentrations is a reasonable standard to investigate the impact of the following sampling options. Composite Sample Design Option (a). Assign only 1 source sample from the floor stratum and 1 source sample from each of the mound strata to each of the composite samples. Each source sample contributes material to only 1 composite sample. Two source samples from the floor stratum would not be used. Composite Sample Design Option (b). Assign 2 source samples from the floor stratum and 1 source sample from each of the mound strata to each composite sample. This infers that one source sample from the floor must be used twice, with 2 composite samples sharing material from this particular source sample. All five source samples from the floor would be used. Composite Sample Design Option (c). Assign 3 source samples from the floor stratum and 1 source sample from each of the mound strata to each composite sample. This infers that several of the source samples from the floor stratum must be assigned to more than one composite sample. All 5 source samples from the floor would be used. Using fewer than 12 source samples will increase the sampling variability over that of the Basic Composite Sample Design, Pavletich (2013). Considering the impact to the variance of the simple mean of the composite sample concentrations, the recommendation is to construct each sample composite using four or five source samples. Although the variance using 5 source samples per composite sample (Composite Sample Design Option (c)) was slightly less than the variance using 4 source samples per composite sample (Composite Sample Design Option (b)), there is no practical difference between those variances. This does not consider that the measurement error variance, which is the same for all composite sample design options considered in this report, will further dilute any differences. Composite Sample Design Option (a) had the largest variance for the mean concentration in the three composite samples and should be avoided. These results are consistent with Pavletich (2014b) which utilizes a low elevation and a high elevation mound source sample and two floor source samples for each composite sample. Utilizing the four source samples per composite design, Pavletich (2014b) utilizes aliquots of Floor Sample 4 for two composite samples.« less

Optimising reversed-phase liquid chromatographic separation of an acidic mixture on a monolithic stationary phase with the aid of response surface methodology and experimental design.

PubMed

Wang, Y; Harrison, M; Clark, B J

2006-02-10

An optimization strategy for the separation of an acidic mixture by employing a monolithic stationary phase is presented, with the aid of experimental design and response surface methodology (RSM). An orthogonal array design (OAD) OA(16) (2(15)) was used to choose the significant parameters for the optimization. The significant factors were optimized by using a central composite design (CCD) and the quadratic models between the dependent and the independent parameters were built. The mathematical models were tested on a number of simulated data set and had a coefficient of R(2) > 0.97 (n = 16). On applying the optimization strategy, the factor effects were visualized as three-dimensional (3D) response surfaces and contour plots. The optimal condition was achieved in less than 40 min by using the monolithic packing with the mobile phase of methanol/20 mM phosphate buffer pH 2.7 (25.5/74.5, v/v). The method showed good agreement between the experimental data and predictive value throughout the studied parameter space and were suitable for optimization studies on the monolithic stationary phase for acidic compounds.

Full-Scale Crash Test and Finite Element Simulation of a Composite Prototype Helicopter

NASA Technical Reports Server (NTRS)

Jackson, Karen E.; Fasanella, Edwin L.; Boitnott, Richard L.; Lyle, Karen H.

2003-01-01

A full-scale crash test of a prototype composite helicopter was performed at the Impact Dynamics Research Facility at NASA Langley Research Center in 1999 to obtain data for validation of a finite element crash simulation. The helicopter was the flight test article built by Sikorsky Aircraft during the Advanced Composite Airframe Program (ACAP). The composite helicopter was designed to meet the stringent Military Standard (MIL-STD-1290A) crashworthiness criteria and was outfitted with two crew and two troop seats and four anthropomorphic dummies. The test was performed at 38-ft/s vertical and 32.5-ft/s horizontal velocity onto a rigid surface. An existing modal-vibration model of the Sikorsky ACAP helicopter was converted into a model suitable for crash simulation. A two-stage modeling approach was implemented and an external user-defined subroutine was developed to represent the complex landing gear response. The crash simulation was executed with a nonlinear, explicit transient dynamic finite element code. Predictions of structural deformation and failure, the sequence of events, and the dynamic response of the airframe structure were generated and the numerical results were correlated with the experimental data to validate the simulation. The test results, the model development, and the test-analysis correlation are described.

Development of a chromatographic method with multi-criteria decision making design for simultaneous determination of nifedipine and atenolol in content uniformity testing.

PubMed

Ahmed, Sameh; Alqurshi, Abdulmalik; Mohamed, Abdel-Maaboud Ismail

2018-07-01

A new robust and reliable high-performance liquid chromatography (HPLC) method with multi-criteria decision making (MCDM) approach was developed to allow simultaneous quantification of atenolol (ATN) and nifedipine (NFD) in content uniformity testing. Felodipine (FLD) was used as an internal standard (I.S.) in this study. A novel marriage between a new interactive response optimizer and a HPLC method was suggested for multiple response optimizations of target responses. An interactive response optimizer was used as a decision and prediction tool for the optimal settings of target responses, according to specified criteria, based on Derringer's desirability. Four independent variables were considered in this study: Acetonitrile%, buffer pH and concentration along with column temperature. Eight responses were optimized: retention times of ATN, NFD, and FLD, resolutions between ATN/NFD and NFD/FLD, and plate numbers for ATN, NFD, and FLD. Multiple regression analysis was applied in order to scan the influences of the most significant variables for the regression models. The experimental design was set to give minimum retention times, maximum resolution and plate numbers. The interactive response optimizer allowed prediction of optimum conditions according to these criteria with a good composite desirability value of 0.98156. The developed method was validated according to the International Conference on Harmonization (ICH) guidelines with the aid of the experimental design. The developed MCDM-HPLC method showed superior robustness and resolution in short analysis time allowing successful simultaneous content uniformity testing of ATN and NFD in marketed capsules. The current work presents an interactive response optimizer as an efficient platform to optimize, predict responses, and validate HPLC methodology with tolerable design space for assay in quality control laboratories. Copyright © 2018 Elsevier B.V. All rights reserved.

Structural Design of Ares V Interstage Composite Structure

NASA Technical Reports Server (NTRS)

Sleigh, David W.; Sreekantamurthy, Thammaiah; Kosareo, Daniel N.; Martin, Robert A.; Johnson, Theodore F.

2011-01-01

Preliminary and detailed design studies were performed to mature composite structural design concepts for the Ares V Interstage structure as a part of NASA s Advanced Composite Technologies Project. Aluminum honeycomb sandwich and hat-stiffened composite panel structural concepts were considered. The structural design and analysis studies were performed using HyperSizer design sizing software and MSC Nastran finite element analysis software. System-level design trade studies were carried out to predict weight and margins of safety for composite honeycomb-core sandwich and composite hat-stiffened skin design concepts. Details of both preliminary and detailed design studies are presented in the paper. For the range of loads and geometry considered in this work, the hat-stiffened designs were found to be approximately 11-16 percent lighter than the sandwich designs. A down-select process was used to choose the most favorable structural concept based on a set of figures of merit, and the honeycomb sandwich design was selected as the best concept based on advantages in manufacturing cost.

Comparison of supercritical fluid extraction and ultrasound-assisted extraction of fatty acids from quince (Cydonia oblonga Miller) seed using response surface methodology and central composite design.

PubMed

Daneshvand, Behnaz; Ara, Katayoun Mahdavi; Raofie, Farhad

2012-08-24

Fatty acids of Cydonia oblonga Miller cultivated in Iran were obtained by supercritical (carbon dioxide) extraction and ultrasound-assisted extraction methods. The oils were analyzed by capillary gas chromatography using mass spectrometric detections. The compounds were identified according to their retention indices and mass spectra (EI, 70eV). The experimental parameters of SFE such as pressure, temperature, modifier volume, static and dynamic extraction time were optimized using a Central Composite Design (CCD) after a 2(5) factorial design. Pressure and dynamic extraction time had significant effect on the extraction yield, while the other factors (temperature, static extraction time and modifier volume) were not identified as significant factors under the selected conditions. The results of chemometrics analysis showed the highest yield for SFE (24.32%), which was obtained at a pressure of 353bar, temperature of 35°C, modifier (methanol) volume of 150μL, and static and dynamic extraction times of 10 and 60min, respectively. Ultrasound-assisted extraction (UAE) of Fatty acids from C. oblonga Miller was optimized, using a rotatable central composite design. The optimum conditions were as follows: solvent (n-hexane) volume, 22mL; extraction time, 30min; and extraction temperature, 55°C. This resulted in a maximum oil recovery of 19.5%. The extracts with higher yield from both methods were subjected to transesterification and GC-MS analysis. The results show that the oil obtained by SFE with the optimal operating conditions allowed a fatty acid composition similar to the oil obtained by UAE in optimum condition and no significant differences were found. The major components of oil extract were Linoleic, Palmitic, Oleic, Stearic and Eicosanoic acids. Copyright © 2012 Elsevier B.V. All rights reserved.

Continuous monitoring of the progressive degradation of a liquid composite by means of a noninvasive microwave resonator

NASA Astrophysics Data System (ADS)

Catala-Civera, Jose M.; Canos-Marin, Antoni J.; de los Reyes, E.

2000-07-01

Microwave control capabilities have been used to monitor the degradation of polyol, an alcohol composite material commonly used in the footwear industry for polymerization purposes. The liquid flows continuously inside a thin pipe and its desirable properties are altered with time associated to moisture absorption processes. Consequently, variations in the dielectric properties are involved, and they can be detected by permittivity measurements. In this paper, in order to obtain high sensitivity and resolution, a rectangular cavity resonator working at a fixed frequency was designed using as sample holder a rectangular pipe containing the liquid going through. Changes in the liquid modify the original response of the cavity with a non- degraded liquid and these differences have been used to determine the degree of degradation of the material. The final response of the microwave resonator was experimentally validated with measurements in a continuous line.

Analysis for the Progressive Failure Response of Textile Composite Fuselage Frames

NASA Technical Reports Server (NTRS)

Johnson, Eric R.; Boitnott, Richard L. (Technical Monitor)

2002-01-01

A part of aviation accident mitigation is a crash worthy airframe structure, and an important measure of merit for a crash worthy structure is the amount of kinetic energy that can be absorbed in the crush of the structure. Prediction of the energy absorbed from finite element analyses requires modeling the progressive failure sequence. Progressive failure modes may include material degradation, fracture and crack growth, and buckling and collapse. The design of crash worthy airframe components will benefit from progressive failure analyses that have been validated by tests. The subject of this research is the development of a progressive failure analysis for textile composite. circumferential fuselage frames subjected to a quasi-static, crash-type load. The test data for these frames are reported, and these data, along with stub column test data, are to be used to develop and to validate methods for the progressive failure response.

Optimisation Of Cutting Parameters Of Composite Material Laser Cutting Process By Taguchi Method

NASA Astrophysics Data System (ADS)

Lokesh, S.; Niresh, J.; Neelakrishnan, S.; Rahul, S. P. Deepak

2018-03-01

The aim of this work is to develop a laser cutting process model that can predict the relationship between the process input parameters and resultant surface roughness, kerf width characteristics. The research conduct is based on the Design of Experiment (DOE) analysis. Response Surface Methodology (RSM) is used in this work. It is one of the most practical and most effective techniques to develop a process model. Even though RSM has been used for the optimization of the laser process, this research investigates laser cutting of materials like Composite wood (veneer)to be best circumstances of laser cutting using RSM process. The input parameters evaluated are focal length, power supply and cutting speed, the output responses being kerf width, surface roughness, temperature. To efficiently optimize and customize the kerf width and surface roughness characteristics, a machine laser cutting process model using Taguchi L9 orthogonal methodology was proposed.

Dynamic effects of a 9 mm missile on cadaveric skull protected by aramid, polyethylene or aluminum plate: an experimental study.

PubMed

Sarron, Jean-Claude; Dannawi, Marwan; Faure, Alexis; Caillou, Jean-Paul; Da Cunha, Joseph; Robert, Roger

2004-08-01

Most military helmets are designed to prevent penetration by small firearms using composite materials in their construction. However, the transient deformation of the composite helmet during a non penetrating impact may result in severe head injury. Two experimental designs were undertaken to characterize the extend of injuries imparted by composite panels using in protective helmets. In the first series, 21 dry skulls were protected by polyethylene plates, with gaps between the protective plate and skull ranging from 12 to 15 mm. In another design, using 9 cadavers, heads were protected by aluminum, aramid, or polyethylene plates. Specimens were instrumented with pressure gauges to record the impact response. The ammunition used in these experiments was 9 mm caliber and had a velocity of 400 m/s. A macroscopic analysis of the specimens quantified fractures and injuries, which were then related to the measured pressures. Protective plates influenced both the levels of injury and the intracranial pressure. Injuries were accentuated as the plates was changed from aluminum to composite materials and ranged from skin laceration to extensive skull fractures and brain contusion. Fractures were associated with brain parenchymal pressures in excess of 560 kPa and cerebrospinal fluid pressure of 150 kPa. An air gap of a few millimeters between the plate and the head was sufficient to decrease these internal pressures by half, significantly reducing the level of injury. Ballistic helmets made of composite materials could be optimized to avoid extensive transient deformation and thus reduce the impact and blunt trauma to the head. However, this deformation cannot be completely removed, which is why the gap between the helmet and the head must be maintained at more than 12 mm.

Resistive switching characteristics and mechanisms in silicon oxide memory devices

NASA Astrophysics Data System (ADS)

Chang, Yao-Feng; Fowler, Burt; Chen, Ying-Chen; Zhou, Fei; Wu, Xiaohan; Chen, Yen-Ting; Wang, Yanzhen; Xue, Fei; Lee, Jack C.

2016-05-01

Intrinsic unipolar SiOx-based resistance random access memories (ReRAM) characterization, switching mechanisms, and applications have been investigated. Device structures, material compositions, and electrical characteristics are identified that enable ReRAM cells with high ON/OFF ratio, low static power consumption, low switching power, and high readout-margin using complementary metal-oxide semiconductor transistor (CMOS)-compatible SiOx-based materials. These ideas are combined with the use of horizontal and vertical device structure designs, composition optimization, electrical control, and external factors to help understand resistive switching (RS) mechanisms. Measured temperature effects, pulse response, and carrier transport behaviors lead to compact models of RS mechanisms and energy band diagrams in order to aid the development of computer-aided design for ultralarge-v scale integration. This chapter presents a comprehensive investigation of SiOx-based RS characteristics and mechanisms for the post-CMOS device era.

Using open captions to revise writing in digital stories composed by d/Deaf and hard of hearing students.

PubMed

Strassman, Barbara K; O'Dell, Katie

2012-01-01

Using a nonexperimental design, the researchers explored the effect of captioning as part of the writing process of individuals who are d/Deaf and hard of hearing. Sixty-nine d/Deaf and hard of hearing middle school students composed responses to four writing-to-learn activities in a word processor. Two compositions were revised and published with software that displayed texts as captions to digital images; two compositions were revised with a word processor and published on paper. Analysis showed increases in content-area vocabulary, text length, and inclusion of main ideas and details for texts revised in the captioning software. Given the nonexperimental design, it is not possible to determine the extent to which the results could be attributed to captioned revisions. However, the findings do suggest that the images acted as procedural facilitators, triggering recall of vocabulary and details.

Advanced composites structural concepts and materials technologies for primary aircraft structures. Structural response and failure analysis: ISPAN modules users manual

NASA Technical Reports Server (NTRS)

Hairr, John W.; Huang, Jui-Ten; Ingram, J. Edward; Shah, Bharat M.

1992-01-01

The ISPAN Program (Interactive Stiffened Panel Analysis) is an interactive design tool that is intended to provide a means of performing simple and self contained preliminary analysis of aircraft primary structures made of composite materials. The program combines a series of modules with the finite element code DIAL as its backbone. Four ISPAN Modules were developed and are documented. These include: (1) flat stiffened panel; (2) curved stiffened panel; (3) flat tubular panel; and (4) curved geodesic panel. Users are instructed to input geometric and material properties, load information and types of analysis (linear, bifurcation buckling, or post-buckling) interactively. The program utilizing this information will generate finite element mesh and perform analysis. The output in the form of summary tables of stress or margins of safety, contour plots of loads or stress, and deflected shape plots may be generalized and used to evaluate specific design.

Utilization of a modified special-cubic design and an electronic tongue for bitterness masking formulation optimization.

PubMed

Li, Lianli; Naini, Venkatesh; Ahmed, Salah U

2007-10-01

A unique modification of simplex design was applied to an electronic tongue (E-Tongue) analysis in bitterness masking formulation optimization. Three formulation variables were evaluated in the simplex design, i.e. concentrations of two taste masking polymers, Amberlite and Carbopol, and pH of the granulating fluid. Response of the design was a bitterness distance measured using an E-Tongue by applying a principle component analysis, which represents taste masking efficiency of the formulation. The smaller the distance, the better the bitterness masking effect. Contour plots and polynomial equations of the bitterness distance response were generated as a function of formulation composition and pH. It was found that interactions between polymer and pH reduced the bitterness of the formulation, attributed to pH-dependent ionization and complexation properties of the ionic polymers, thus keeping the drug out of solution and unavailable to bitterness perception. At pH 4.9 and an Amberlite/Carbopol ratio of 1.4:1 (w/w), the optimal taste masking formulation was achieved and in agreement with human gustatory sensation study results. Therefore, adopting a modified simplex experimental design on response measured using an E-Tongue provided an efficient approach to taste masking formulation optimization using ionic binding polymers. (c) 2007 Wiley-Liss, Inc.

Visible-light-driven Bi 2 O 3 /WO 3 composites with enhanced photocatalytic activity

DOE PAGES

Adhikari, Shiba P.; Dean, Hunter; Hood, Zachary D.; ...

2015-10-19

Semiconductor heterojunctions (composites) have been shown to be effective photocatalytic materials to overcome the drawbacks of low photocatalytic efficiency that results from electron–hole recombination and narrow photo-response range. We prepared a novel visible-light-driven Bi 2O 3/WO 3 composite photocatalyst by hydrothermal synthesis. The composite was characterized by scanning transmission electron microscopy (STEM), scanning electron microscopy (SEM), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) surface area, Raman spectroscopy, photoluminescence spectroscopy (PL) and electrochemical impedance spectroscopy (EIS) to better understand the structures, compositions, morphologies and optical properties. Bi 2O 3/WO 3 heterojunction was found to exhibit significantly higher photocatalyticmore » activity towards the decomposition of Rhodamine B (RhB) and 4-nitroaniline (4-NA) under visible light irradiation compared to that of Bi 2O 3 and WO 3. A tentative mechanism for the enhanced photocatalytic activity of the heterostructured composite is discussed based on observed activity, band position calculations, photoluminescence, and electrochemical impedance data. Our study provides a new strategy for the design of composite materials with enhanced visible light photocatalytic performance.« less

Within-day protein distribution does not influence body composition responses during weight loss in resistance-training adults who are overweight.

PubMed

Hudson, Joshua L; Kim, Jung Eun; Paddon-Jones, Douglas; Campbell, Wayne W

2017-11-01

Background: Emerging research suggests that redistributing total protein intake from 1 high-protein meal/d to multiple moderately high-protein meals improves 24-h muscle protein synthesis. Over time, this may promote positive changes in body composition. Objective: We sought to assess the effects of within-day protein intake distribution on changes in body composition during dietary energy restriction and resistance training. Design: In a randomized parallel-design study, 41 men and women [mean ± SEM age: 35 ± 2 y; body mass index (in kg/m 2 ): 31.5 ± 0.5] consumed an energy-restricted diet (750 kcal/d below the requirement) for 16 wk while performing resistance training 3 d/wk. Subjects consumed 90 g protein/d (1.0 ± 0.03 g · kg -1 · d -1 , 125% of the Recommended Dietary Allowance, at intervention week 1) in either a skewed (10 g at breakfast, 20 g at lunch, and 60 g at dinner; n = 20) or even (30 g each at breakfast, lunch, and dinner; n = 21) distribution pattern. Body composition was measured pre- and postintervention. Results: Over time, whole-body mass (least-squares mean ± SE: -7.9 ± 0.6 kg), whole-body lean mass (-1.0 ± 0.2 kg), whole-body fat mass (-6.9 ± 0.5 kg), appendicular lean mass (-0.7 ± 0.1 kg), and appendicular fat mass (-2.6 ± 0.2 kg) each decreased. The midthigh muscle area (0 ± 1 cm 2 ) did not change over time, whereas the midcalf muscle area decreased (-3 ± 1 cm 2 ). Within-day protein distribution did not differentially affect these body-composition responses. Conclusion: The effectiveness of dietary energy restriction combined with resistance training to improve body composition is not influenced by the within-day distribution of protein when adequate total protein is consumed. This trial was registered at clinicaltrials.gov as NCT02066948. © 2017 American Society for Nutrition.

Design and Optimization of Composite Gyroscope Momentum Wheel Rings

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2007-01-01

Stress analysis and preliminary design/optimization procedures are presented for gyroscope momentum wheel rings composed of metallic, metal matrix composite, and polymer matrix composite materials. The design of these components involves simultaneously minimizing both true part volume and mass, while maximizing angular momentum. The stress analysis results are combined with an anisotropic failure criterion to formulate a new sizing procedure that provides considerable insight into the design of gyroscope momentum wheel ring components. Results compare the performance of two optimized metallic designs, an optimized SiC/Ti composite design, and an optimized graphite/epoxy composite design. The graphite/epoxy design appears to be far superior to the competitors considered unless a much greater premium is placed on volume efficiency compared to mass efficiency.

Measurement and prediction of the thermomechanical response of shape memory alloy hybrid composite beams

NASA Astrophysics Data System (ADS)

Davis, Brian; Turner, Travis L.; Seelecke, Stefan

2005-05-01

Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons within the beam structures. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical analysis/design tool. The experimental investigation is refined by a more thorough test procedure and incorporation of higher fidelity measurements such as infrared thermography and projection moire interferometry. The numerical results are produced by a recently commercialized version of the constitutive model as implemented in ABAQUS and are refined by incorporation of additional measured parameters such as geometric imperfection. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. The results demonstrate the effectiveness of SMAHC structures in controlling static and dynamic responses by adaptive stiffening. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

Measurement and Prediction of the Thermomechanical Response of Shape Memory Alloy Hybrid Composite Beams

NASA Technical Reports Server (NTRS)

Davis, Brian; Turner, Travis L.; Seelecke, Stefan

2005-01-01

Previous work at NASA Langley Research Center (LaRC) involved fabrication and testing of composite beams with embedded, pre-strained shape memory alloy (SMA) ribbons within the beam structures. That study also provided comparison of experimental results with numerical predictions from a research code making use of a new thermoelastic model for shape memory alloy hybrid composite (SMAHC) structures. The previous work showed qualitative validation of the numerical model. However, deficiencies in the experimental-numerical correlation were noted and hypotheses for the discrepancies were given for further investigation. The goal of this work is to refine the experimental measurement and numerical modeling approaches in order to better understand the discrepancies, improve the correlation between prediction and measurement, and provide rigorous quantitative validation of the numerical analysis/design tool. The experimental investigation is refined by a more thorough test procedure and incorporation of higher fidelity measurements such as infrared thermography and projection moire interferometry. The numerical results are produced by a recently commercialized version of the constitutive model as implemented in ABAQUS and are refined by incorporation of additional measured parameters such as geometric imperfection. Thermal buckling, post-buckling, and random responses to thermal and inertial (base acceleration) loads are studied. The results demonstrate the effectiveness of SMAHC structures in controlling static and dynamic responses by adaptive stiffening. Excellent agreement is achieved between the predicted and measured results of the static and dynamic thermomechanical response, thereby providing quantitative validation of the numerical tool.

Reliability Sensitivity Analysis and Design Optimization of Composite Structures Based on Response Surface Methodology

NASA Technical Reports Server (NTRS)

Rais-Rohani, Masoud

2003-01-01

This report discusses the development and application of two alternative strategies in the form of global and sequential local response surface (RS) techniques for the solution of reliability-based optimization (RBO) problems. The problem of a thin-walled composite circular cylinder under axial buckling instability is used as a demonstrative example. In this case, the global technique uses a single second-order RS model to estimate the axial buckling load over the entire feasible design space (FDS) whereas the local technique uses multiple first-order RS models with each applied to a small subregion of FDS. Alternative methods for the calculation of unknown coefficients in each RS model are explored prior to the solution of the optimization problem. The example RBO problem is formulated as a function of 23 uncorrelated random variables that include material properties, thickness and orientation angle of each ply, cylinder diameter and length, as well as the applied load. The mean values of the 8 ply thicknesses are treated as independent design variables. While the coefficients of variation of all random variables are held fixed, the standard deviations of ply thicknesses can vary during the optimization process as a result of changes in the design variables. The structural reliability analysis is based on the first-order reliability method with reliability index treated as the design constraint. In addition to the probabilistic sensitivity analysis of reliability index, the results of the RBO problem are presented for different combinations of cylinder length and diameter and laminate ply patterns. The two strategies are found to produce similar results in terms of accuracy with the sequential local RS technique having a considerably better computational efficiency.

Structural considerations in design of lightweight glass-fiber composite pressure vessels

NASA Technical Reports Server (NTRS)

Faddoul, J. R.

1973-01-01

The development of structurally efficient, metal-lined, glass-fiber composite pressure vessels. Both the current state-of-the-art and current problems are discussed along with fracture mechanics considerations for the metal liner. The design concepts used for metal-lined, glass-fiber, composite pressure vessels are described and the structural characteristics of the composite designs are compared with each other and with homogeneous metal pressure vessels. Specific design techniques and available design data are identified. Results of a current program to evaluate flaw growth and fracture characteristics of the metal liners are reviewed and the impact of these results on composite pressure vessel designs is discussed.

Application of Pi Preform Composite Joints in Fabrication of NASA Composite Crew Module Demonstration Structure

NASA Technical Reports Server (NTRS)

Higgins, John E.; Pelham, Larry

2008-01-01

This paper will describe unique and extensive use of pre-woven and impregnated pi cross-sections in fabrication of a carbon composite demonstration structure for the Composite Crew Module (CCM) Program. The program is managed by the NASA Safety and Engineering Center with participants from ten NASA Centers and AFRL. Multiple aerospace contractors are participating in the design development, tooling and fabrication effort as well. The goal of the program is to develop an agency wide design team for composite habitable spacecraft. The specific goals for this development project are: a) To gain hands on experience in design, building and testing a composite crew module. b) To validate key assumptions by resolving composite spacecraft design details through fabrication and testing of hardware. This paper will focus on the design and fabrication issues supporting selection of the Lockheed Martin patented Pi pre-form to provide sound composite joints a numerous locations in the structure. This abstract is based on Preliminary Design data. The final design will continue to evolve through the fall of 2007 with fabrication mostly completed by conference date.

Interphase and particle dispersion correlations in polymer nanocomposites

NASA Astrophysics Data System (ADS)

Senses, Erkan

Particle dispersion in polymer matrices is a major parameter governing the mechanical performance of polymer nanocomposites. Controlling particle dispersion and understanding aging of composites under large shear and temperature variations determine the processing conditions and lifetime of composites which are very important for diverse applications in biomedicine, highly reinforced materials and more importantly for the polymer composites with adaptive mechanical responses. This thesis investigates the role of interphase layers between particles and polymer matrices in two bulk systems where particle dispersion is altered upon deformation in repulsive composites, and good-dispersion of particles is retained after multiple oscillatory shearing and aging cycles in attractive composites. We demonstrate that chain desorption and re-adsorption processes in attractive composites under shear can effectively enhance the bulk microscopic mechanical properties, and long chains of adsorbed layers lead to a denser entangled interphase layer. We further designed experiments where particles are physically adsorbed with bimodal lengths of homopolymer chains to underpin the entanglement effect in interphases. Bimodal adsorbed chains are shown to improve the interfacial strength and used to modulate the elastic properties of composites without changing the particle loading, dispersion state or polymer conformation. Finally, the role of dynamic asymmetry (different mobilities in polymer blends) and chemical heterogeneity in the interphase layer are explored in systems of poly(methyl methacrylate) adsorbed silica nanoparticles dispersed in poly(ethylene oxide) matrix. Such nanocomposites are shown to exhibit unique thermal-stiffening behavior at temperatures above glass transitions of both polymers. These interesting findings suggest that the mobility of the surface-bound polymer is essential for reinforcement in polymer nanocomposites, contrary to existing glassy layer theories for polymers on attractive particle surfaces. The shown thermally-induced stiffening behavior is reversible and makes this interfacial mechanism highly attractive in developing new active, remotely controllable engineered materials from non-responsive components.

Monolithic Composite “Pressure + Acceleration + Temperature + Infrared” Sensor Using a Versatile Single-Sided “SiN/Poly-Si/Al” Process-Module

PubMed Central

Ni, Zao; Yang, Chen; Xu, Dehui; Zhou, Hong; Zhou, Wei; Li, Tie; Xiong, Bin; Li, Xinxin

2013-01-01

We report a newly developed design/fabrication module with low-cost single-sided “low-stress-silicon-nitride (LS-SiN)/polysilicon (poly-Si)/Al” process for monolithic integration of composite sensors for sensing-network-node applications. A front-side surface-/bulk-micromachining process on a conventional Si-substrate is developed, featuring a multifunctional SiN/poly-Si/Al layer design for diverse sensing functions. The first “pressure + acceleration + temperature + infrared” (PATIR) composite sensor with the chip size of 2.5 mm × 2.5 mm is demonstrated. Systematic theoretical design and analysis methods are developed. The diverse sensing components include a piezoresistive absolute-pressure sensor (up to 700 kPa, with a sensitivity of 49 mV/MPa under 3.3 V supplied voltage), a piezoresistive accelerometer (±10 g, with a sensitivity of 66 μV/g under 3.3 V and a −3 dB bandwidth of 780 Hz), a thermoelectric infrared detector (with a responsivity of 45 V/W and detectivity of 3.6 × 107 cm·Hz1/2/W) and a thermistor (−25–120 °C). This design/fabrication module concept enables a low-cost monolithically-integrated “multifunctional-library” technique. It can be utilized as a customizable tool for versatile application-specific requirements, which is very useful for small-size, low-cost, large-scale sensing-network node developments. PMID:23325169

Media milling process optimization for manufacture of drug nanoparticles using design of experiments (DOE).

PubMed

Nekkanti, Vijaykumar; Marwah, Ashwani; Pillai, Raviraj

2015-01-01

Design of experiments (DOE), a component of Quality by Design (QbD), is systematic and simultaneous evaluation of process variables to develop a product with predetermined quality attributes. This article presents a case study to understand the effects of process variables in a bead milling process used for manufacture of drug nanoparticles. Experiments were designed and results were computed according to a 3-factor, 3-level face-centered central composite design (CCD). The factors investigated were motor speed, pump speed and bead volume. Responses analyzed for evaluating these effects and interactions were milling time, particle size and process yield. Process validation batches were executed using the optimum process conditions obtained from software Design-Expert® to evaluate both the repeatability and reproducibility of bead milling technique. Milling time was optimized to <5 h to obtain the desired particle size (d90 < 400 nm). The desirability function used to optimize the response variables and observed responses were in agreement with experimental values. These results demonstrated the reliability of selected model for manufacture of drug nanoparticles with predictable quality attributes. The optimization of bead milling process variables by applying DOE resulted in considerable decrease in milling time to achieve the desired particle size. The study indicates the applicability of DOE approach to optimize critical process parameters in the manufacture of drug nanoparticles.

Gap junctions in cells of the immune system: structure, regulation and possible functional roles.

PubMed

Sáez, J C; Brañes, M C; Corvalán, L A; Eugenín, E A; González, H; Martínez, A D; Palisson, F

2000-04-01

Gap junction channels are sites of cytoplasmic communication between contacting cells. In vertebrates, they consist of protein subunits denoted connexins (Cxs) which are encoded by a gene family. According to their Cx composition, gap junction channels show different gating and permeability properties that define which ions and small molecules permeate them. Differences in Cx primary sequences suggest that channels composed of different Cxs are regulated differentially by intracellular pathways under specific physiological conditions. Functional roles of gap junction channels could be defined by the relative importance of permeant substances, resulting in coordination of electrical and/or metabolic cellular responses. Cells of the native and specific immune systems establish transient homo- and heterocellular contacts at various steps of the immune response. Morphological and functional studies reported during the last three decades have revealed that many intercellular contacts between cells in the immune response present gap junctions or "gap junction-like" structures. Partial characterization of the molecular composition of some of these plasma membrane structures and regulatory mechanisms that control them have been published recently. Studies designed to elucidate their physiological roles suggest that they might permit coordination of cellular events which favor the effective and timely response of the immune system.

Vanadium oxide-carbon nanotube composite electrodes for energy storage by supercritical fluid deposition: experiment design and device performance

NASA Astrophysics Data System (ADS)

Do, Quyet H.; Fielitz, Thomas R.; Zeng, Changchun; Arda Vanli, O.; Zhang, Chuck; Zheng, Jim P.

2013-08-01

Vanadium pentoxide (V2O5) deposited on porous multiwalled carbon nanotube (MWCNT) buckypaper using supercritical fluid CO2(scCO2) deposition shows excellent performance for electrochemical capacitors. However, the low weight loading of V2O5 is one of the main problems. In this paper, design of experiments and response surface methods were employed to explore strategies for improving the active material loading by increasing the organo-vanadium precursor adsorption. A second-order response surface model was fitted to the designed experiments to predict the loading of the vanadium precursors onto carbon nanotube buckypaper as a function of time, temperature and pressure of CO2, buckypaper functionalization, precursor type, initial precursor mass and stir speed. Operation conditions were identified by employing a model that led to a precursor loading of 19.33%, an increase of 72.28% over the initial screening design. CNTs-V2O5 composite electrodes fabricated from deposited samples using the optimized conditions demonstrated outstanding electrochemical performance (947.1 F g-1 of V2O5 at a high scan rate 100 mV s-1). The model also predicted operation conditions under which light precursor aggregation took place. The V2O5 from aggregated precursor still possessed considerable specific capacitance (311 F g-1 of V2O5 at a scan rate 100 mV s-1), and the significantly higher V2O5 loading (˜81%) contributed to an increase in overall electrode capacitance.

An Examination of the Applications of Constitutional Concepts as an Approach to Classroom Management: Four Studies of Judicious Discipline in Various Classroom Settings.

ERIC Educational Resources Information Center

McEwan, Barbara; Gathercoal, Paul; Nimmo, Virginia

This paper presents a composite of four separate research studies conducted to assess the impact of constitutional language on classroom environments. The studies were designed to examine the uses of "Judicious Discipline" in a variety of classrooms and how the use of a common language based on rights and responsibilities affected the…

Effects of atmospheric CO[sub 2] and soil NO[sub 3][sup [minus

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lindroth, R.L.; Kinney, K.K.

1993-06-01

Physiological and growth responses of trees to elevated atmospheric CO[sub 2] are influenced by soil nutrient availability. Interactive effects of these factors on tree chemical composition, however, are largely unknown. We used a split-plot experimental design to assess the impact of CO[sub 2] (whole plots; 355 and 650 ppm) and soil NO[sub 3][sup [minus

What's Happening in Freshman Composition in the California Two-Year College: A Collection of Writing Tasks. "A Working Book."

ERIC Educational Resources Information Center

Hale, Helena, Comp.

Designed as a looseleaf resource, a supplement to established teaching plans, and an aid to meeting individual needs, this compilation of writing exercises represents the responses of 157 teachers from 87 two-year colleges to the request, "Describe a successful writing task -- what it is, how you teach it, and why." The compilation includes tasks…

Effect of fertilizer applications and grazing exclusion on species composition and biomass in wet meadow restoration in eastern Washington.

Treesearch

John Beebe; Richard Everett; George Scherer; Carl. Davis

2002-01-01

Fertilizer applications and grazing exclusion were used as restoration strategies in degraded wet meadows in eastern Washington to grow biomass in the root systems where it could not be grazed. We used a split-block design to test vegetation responses to six fertilizer rates, eight fertilizer types, and three grazing treatments after three growing seasons. Little...

Conceptual design and structural analysis of the spectroscopy of the atmosphere using far infrared emission (SAFIRE) instrument

NASA Technical Reports Server (NTRS)

Moses, Robert W.; Averill, Robert D.

1992-01-01

The conceptual design and structural analysis for the Spectroscopy of the Atmosphere using Far Infrared Emission (SAFIRE) Instrument are provided. SAFIRE, which is an international effort, is proposed for the Earth Observing Systems (EOS) program for atmospheric ozone studies. A concept was developed which meets mission requirements and is the product of numerous parametric studies and design/analysis iterations. Stiffness, thermal stability, and weight constraints led to a graphite/epoxy composite design for the optical bench and supporting struts. The structural configuration was determined by considering various mounting arrangements of the optical, cryo, and electronic components. Quasi-static, thermal, modal, and dynamic response analyses were performed, and the results are presented for the selected configuration.

Thermostructural responses of carbon phenolics in a restrained thermal growth test

NASA Technical Reports Server (NTRS)

Wang, C. Jeff

1992-01-01

The thermostructural response of carbon phenolic components in a solid rocket motor (SRM) is a complex process. It involves simultaneous heat and mass transfer along with chemical reactions in a multiphase system with time-dependent material properties and boundary conditions. In contrast to metals, the fracture of fiber-reinforced composites is characterized by the initiation and progression of multiple failures of different modes such as matrix cracks, interfacial debonding, fiber breaks, and delamination. The investigation of thermostructural responses of SRM carbon phenolics is further complicated by different failure modes under static and dynamic load applications. Historically, there have been several types of post-firing anomalies found in the carbon phenolic composites of the Space Shuttle SRM nozzle. Three major failure modes which have been observed on SRM nozzles are pocketing (spallation), ply-lift, and wedge-out. In order to efficiently control these anomalous phenomena, an investigation of fracture mechanisms under NASA/MSFC RSRM (Redesigned Solid Rocket Motor) and SPIP (Solid Propulsion Integrity Program) programs have been conducted following each anomaly. This report reviews the current progress in understanding the effects of the thermostructural behavior of carbon phenolics on the failure mechanisms of the SRM nozzle. A literature search was conducted and a technical bibliography was developed to support consolidation and assimilation of learning from the RSRM and SPIP investigation efforts. Another important objective of this report is to present a knowledge-based design basis for carbon phenolics that combines the analyses of thermochemical decomposition, pore pressure stresses, and thermostructural properties. Possible areas of application of the knowledge-based design include critical material properties development, nozzle component design, and SRM materials control.

Piezoresistive Composite Silicon Dioxide Nanocantilever Surface Stress Sensor: Design and Optimization.

PubMed

Mathew, Ribu; Sankar, A Ravi

2018-05-01

In this paper, we present the design and optimization of a rectangular piezoresistive composite silicon dioxide nanocantilever sensor. Unlike the conventional design approach, we perform the sensor optimization by not only considering its electro-mechanical response but also incorporating the impact of self-heating induced thermal drift in its terminal characteristics. Through extensive simulations first we comprehend and quantify the inaccuracies due to self-heating effect induced by the geometrical and intrinsic parameters of the piezoresistor. Then, by optimizing the ratio of electrical sensitivity to thermal sensitivity defined as the sensitivity ratio (υ) we improve the sensor performance and measurement reliability. Results show that to ensure υ ≥ 1, shorter and wider piezoresistors are better. In addition, it is observed that unlike the general belief that high doping concentration of piezoresistor reduces thermal sensitivity in piezoresistive sensors, to ensure υ ≥ 1 doping concentration (p) should be in the range: 1E18 cm-3 ≤ p ≤ 1E19 cm-3. Finally, we provide a set of design guidelines that will help NEMS engineers to optimize the performance of such sensors for chemical and biological sensing applications.

Analysis of thin-walled cylindrical composite shell structures subject to axial and bending loads: Concept development, analytical modeling and experimental verification

NASA Astrophysics Data System (ADS)

Mahadev, Sthanu

Continued research and development efforts devoted in recent years have generated novel avenues towards the advancement of efficient and effective, slender laminated fiber-reinforced composite members. Numerous studies have focused on the modeling and response characterization of composite structures with particular relevance to thin-walled cylindrical composite shells. This class of shell configurations is being actively explored to fully determine their mechanical efficacy as primary aerospace structural members. The proposed research is targeted towards formulating a composite shell theory based prognosis methodology that entails an elaborate analysis and investigation of thin-walled cylindrical shell type laminated composite configurations that are highly desirable in increasing number of mechanical and aerospace applications. The prime motivation to adopt this theory arises from its superior ability to generate simple yet viable closed-form analytical solution procedure to numerous geometrically intense, inherent curvature possessing composite structures. This analytical evaluative routine offers to acquire a first-hand insight on the primary mechanical characteristics that essentially govern the behavior of slender composite shells under typical static loading conditions. Current work exposes the robustness of this mathematical framework via demonstrating its potential towards the prediction of structural properties such as axial stiffness and bending stiffness respectively. Longitudinal ply-stress computations are investigated upon deriving the global stiffness matrix model for composite cylindrical tubes with circular cross-sections. Additionally, this work employs a finite element based numerical technique to substantiate the analytical results reported for cylindrically shaped circular composite tubes. Furthermore, this concept development is extended to the study of thin-walled, open cross-sectioned, curved laminated shells that are geometrically distinguished with respect to the circumferential arc angle, thickness-to-mean radius ratio and total laminate thickness. The potential of this methodology is challenged to analytically determine the location of the centroid. This precise location dictates the decoupling of extension-bending type deformational response in tension loaded composite structures. Upon the cross-validation of the centroidal point through the implementation of an ANSYS based finite element routine, influence of centroid is analytically examined under the application of a concentrated longitudinal tension and bending type loadings on a series of cylindrical shells characterized by three different symmetric-balanced stacking sequences. In-plane ply-stresses are computed and analyzed across the circumferential contour. An experimental investigation has been incorporated via designing an ad-hoc apparatus and test-up that accommodates the quantification of in-plane strains, computation of ply-stresses and addresses the physical characteristics for a set of auto-clave fabricated cylindrical shell articles. Consequently, this work is shown to essentially capture the mechanical aspects of cylindrical shells, thus facilitating structural engineers to design and manufacture viable structures.

Electric Switching of Fluorescence Decay in Gold-Silica-Dye Nematic Nanocolloids Mediated by Surface Plasmons.

PubMed

Jiang, Li; Mundoor, Haridas; Liu, Qingkun; Smalyukh, Ivan I

2016-07-26

Tunable composite materials with interesting physical behavior can be designed through integrating unique optical properties of solid nanostructures with facile responses of soft matter to weak external stimuli, but this approach remains challenged by their poorly controlled coassembly at the mesoscale. Using scalable wet chemical synthesis procedures, we fabricated anisotropic gold-silica-dye colloidal nanostructures and then organized them into the device-scale (demonstrated for square-inch cells) electrically tunable composites by simultaneously invoking molecular and colloidal self-assembly. We show that the ensuing ordered colloidal dispersions of shape-anisotropic nanostructures exhibit tunable fluorescence decay rates and intensity. We characterize how these properties depend on low-voltage fields and polarization of both the excitation and emission light, demonstrating a great potential for the practical realization of an interesting breed of nanostructured composite materials.

An amino acid composition criterion for membrane active antimicrobials

NASA Astrophysics Data System (ADS)

Schmidt, Nathan; Lai, Ghee Hwee; Mishra, Abhijit; Bong, Dennis; McCray, Paul, Jr.; Selsted, Michael; Ouellette, Andre; Wong, Gerard

2011-03-01

Membrane active antimicrobials (AMPs) are short amphipathic peptides with broad spectrum anti microbial activity. While it is believed that their hydrophobic and cationic moieties are responsible for membrane-based mechanisms of action, membrane disruption by AMPs is manifested in a diversity of outcomes, such as pore formation, blebbing, and budding. This complication, along with others, have made a detailed, molecular understanding of AMPs difficult. We use synchrotron small angle xray scattering to investigate the interaction of model bacterial and eukaryotic cell membranes with archetypes from beta-sheet AMPs (e.g. defensins) and alpha-helical AMPs (e.g. magainins). The relationship between membrane composition and peptide induced changes in membrane curvature and topology is examined. By comparing the membrane rearrangement and phase behavior induced by these different peptides we will discuss the importance of amino acid composition on AMP design.

Iterative and variational homogenization methods for filled elastomers

NASA Astrophysics Data System (ADS)

Goudarzi, Taha

Elastomeric composites have increasingly proved invaluable in commercial technological applications due to their unique mechanical properties, especially their ability to undergo large reversible deformation in response to a variety of stimuli (e.g., mechanical forces, electric and magnetic fields, changes in temperature). Modern advances in organic materials science have revealed that elastomeric composites hold also tremendous potential to enable new high-end technologies, especially as the next generation of sensors and actuators featured by their low cost together with their biocompatibility, and processability into arbitrary shapes. This potential calls for an in-depth investigation of the macroscopic mechanical/physical behavior of elastomeric composites directly in terms of their microscopic behavior with the objective of creating the knowledge base needed to guide their bottom-up design. The purpose of this thesis is to generate a mathematical framework to describe, explain, and predict the macroscopic nonlinear elastic behavior of filled elastomers, arguably the most prominent class of elastomeric composites, directly in terms of the behavior of their constituents --- i.e., the elastomeric matrix and the filler particles --- and their microstructure --- i.e., the content, size, shape, and spatial distribution of the filler particles. This will be accomplished via a combination of novel iterative and variational homogenization techniques capable of accounting for interphasial phenomena and finite deformations. Exact and approximate analytical solutions for the fundamental nonlinear elastic response of dilute suspensions of rigid spherical particles (either firmly bonded or bonded through finite size interphases) in Gaussian rubber are first generated. These results are in turn utilized to construct approximate solutions for the nonlinear elastic response of non-Gaussian elastomers filled with a random distribution of rigid particles (again, either firmly bonded or bonded through finite size interphases) at finite concentrations. Three-dimensional finite element simulations are also carried out to gain further insight into the proposed theoretical solutions. Inter alia, we make use of these solutions to examine the effects of particle concentration, mono- and poly-dispersity of the filler particle size, and the presence of finite size interphases on the macroscopic response of filled elastomers. The solutions are found able to explain and describe experimental results that to date have been understood only in part. More generally, the solutions provide a robust tool to efficiently guide the design of filled elastomers with desired macroscopic properties. The homogenization techniques developed in this work are not limited to nonlinear elasticity, but can be readily utilized to study multi-functional properties as well. For demonstration purposes, we work out a novel exact solution for the macroscopic dielectric response of filled elastomers with interphasial space charges.

Evaluation of a Mathematical Model of Rat Body Weight Regulation in Application to Caloric Restriction and Drug Treatment Studies.

PubMed

Selimkhanov, Jangir; Thompson, W Clayton; Patterson, Terrell A; Hadcock, John R; Scott, Dennis O; Maurer, Tristan S; Musante, Cynthia J

2016-01-01

The purpose of this work is to develop a mathematical model of energy balance and body weight regulation that can predict species-specific response to common pre-clinical interventions. To this end, we evaluate the ability of a previously published mathematical model of mouse metabolism to describe changes in body weight and body composition in rats in response to two short-term interventions. First, we adapt the model to describe body weight and composition changes in Sprague-Dawley rats by fitting to data previously collected from a 26-day caloric restriction study. The calibrated model is subsequently used to describe changes in rat body weight and composition in a 23-day cannabinoid receptor 1 antagonist (CB1Ra) study. While the model describes body weight data well, it fails to replicate body composition changes with CB1Ra treatment. Evaluation of a key model assumption about deposition of fat and fat-free masses shows a limitation of the model in short-term studies due to the constraint placed on the relative change in body composition components. We demonstrate that the model can be modified to overcome this limitation, and propose additional measurements to further test the proposed model predictions. These findings illustrate how mathematical models can be used to support drug discovery and development by identifying key knowledge gaps and aiding in the design of additional experiments to further our understanding of disease-relevant and species-specific physiology.

Evaluation of a Mathematical Model of Rat Body Weight Regulation in Application to Caloric Restriction and Drug Treatment Studies

PubMed Central

Selimkhanov, Jangir; Patterson, Terrell A.; Scott, Dennis O.; Maurer, Tristan S.; Musante, Cynthia J.

2016-01-01

The purpose of this work is to develop a mathematical model of energy balance and body weight regulation that can predict species-specific response to common pre-clinical interventions. To this end, we evaluate the ability of a previously published mathematical model of mouse metabolism to describe changes in body weight and body composition in rats in response to two short-term interventions. First, we adapt the model to describe body weight and composition changes in Sprague-Dawley rats by fitting to data previously collected from a 26-day caloric restriction study. The calibrated model is subsequently used to describe changes in rat body weight and composition in a 23-day cannabinoid receptor 1 antagonist (CB1Ra) study. While the model describes body weight data well, it fails to replicate body composition changes with CB1Ra treatment. Evaluation of a key model assumption about deposition of fat and fat-free masses shows a limitation of the model in short-term studies due to the constraint placed on the relative change in body composition components. We demonstrate that the model can be modified to overcome this limitation, and propose additional measurements to further test the proposed model predictions. These findings illustrate how mathematical models can be used to support drug discovery and development by identifying key knowledge gaps and aiding in the design of additional experiments to further our understanding of disease-relevant and species-specific physiology. PMID:27227543

Neural correlates of nature stimuli: an FMRI study.

PubMed

Pati, Debajyoti; O'Boyle, Michael; Amor, Cherif; Hou, Jiancheng; Valipoor, Shabboo; Fang, Dan

2014-01-01

Examine whether there are unique patterns of brain activation associated with exposure to photographic sky compositions (representing nature stimuli) as compared with other positive, negative, and neutral images. The positive impact of nature images on health outcomes traditionally has been measured using behavioral and physiological indicators. However, there is a lack of understanding of the underlying neural mechanism that explains this positive influence. A combination of behavioral responses and functional magnetic resonance imaging (fMRI) technology was used to address research questions. Ten participants belonging to five age groups were subjected to short (25 seconds) exposures of 32 images while their brain activation was monitored via the BOLD response. In a separate run, participants were subjected to extended exposures (12 minutes) of a sky composition and an image of a traditional ceiling. The results show that the activation patterns produced by sky compositions and positive images were quite similar as compared to negative or neutral images. However, sky compositions also produced some unique areas of activation, including those associated with spatial cognition, the expanse of space, circadian rhythm, and perceived motion. In the extended exposure condition, sky compositions tended to activate regions associated with dreaming, while traditional ceiling images activated regions that are related to face processing and potentially visual hallucinations. Nature stimuli, with a combination of vegetation and sky, may produce unique beneficial effects not present in general positive stimuli. Evidence-based design, hospital, healing environments, outcomes, patient-centered care.

Proceedings of a Workshop on Composite Material Response: Constitutive Relations and Damage Mechanisms Held in Glasgow, United Kingdom on July 30-31, 1987

DTIC Science & Technology

1987-07-01

Grosvenor Hotel, Glasgow, UK, July 30th and 31st 1987. COMPOSITE MATERIAL RESPONSE: CONSTITUTIVE RELATIONS AND DAMAGE MECHANISMS Edited by G. C . SIH...Cataloguing in Publication Data Composite material response. I. Composite materials I. Sib, G. C . (George C .) 620.l’l 8 ISBN 1-85166-228-6 Library of...Strathclyde) Composite material response: constitutive relations and damage mechanisms/edited by G. C . Sih ... [et al.]. p. cm. "Proceedings of a Workshop on

Statistical optimization of medium components and growth conditions by response surface methodology to enhance phenol degradation by Pseudomonas putida.

PubMed

Annadurai, Gurusamy; Ling, Lai Yi; Lee, Jiunn-Fwu

2008-02-28

In this work, a four-level Box-Behnken factorial design was employed combining with response surface methodology (RSM) to optimize the medium composition for the degradation of phenol by pseudomonas putida (ATCC 31800). A mathematical model was then developed to show the effect of each medium composition and their interactions on the biodegradation of phenol. Response surface method was using four levels like glucose, yeast extract, ammonium sulfate and sodium chloride, which also enabled the identification of significant effects of interactions for the batch studies. The biodegradation of phenol on Pseudomonas putida (ATCC 31800) was determined to be pH-dependent and the maximum degradation capacity of microorganism at 30 degrees C when the phenol concentration was 0.2 g/L and the pH of the solution was 7.0. Second order polynomial regression model was used for analysis of the experiment. Cubic and quadratic terms were incorporated into the regression model through variable selection procedures. The experimental values are in good agreement with predicted values and the correlation coefficient was found to be 0.9980.

Effective monitoring of agriculture: a response.

PubMed

Sachs, Jeffrey D; Remans, Roseline; Smukler, Sean M; Winowiecki, Leigh; Andelman, Sandy J; Cassman, Kenneth G; Castle, David; DeFries, Ruth; Denning, Glenn; Fanzo, Jessica; Jackson, Louise E; Leemans, Rik; Lehmann, Johannes; Milder, Jeffrey C; Naeem, Shahid; Nziguheba, Generose; Palm, Cheryl A; Pingali, Prabhu L; Reganold, John P; Richter, Daniel D; Scherr, Sara J; Sircely, Jason; Sullivan, Clare; Tomich, Thomas P; Sanchez, Pedro A

2012-03-01

The development of effective agricultural monitoring networks is essential to track, anticipate and manage changes in the social, economic and environmental aspects of agriculture. We welcome the perspective of Lindenmayer and Likens (J. Environ. Monit., 2011, 13, 1559) as published in the Journal of Environmental Monitoring on our earlier paper, "Monitoring the World's Agriculture" (Sachs et al., Nature, 2010, 466, 558-560). In this response, we address their three main critiques labeled as 'the passive approach', 'the problem with uniform metrics' and 'the problem with composite metrics'. We expand on specific research questions at the core of the network design, on the distinction between key universal and site-specific metrics to detect change over time and across scales, and on the need for composite metrics in decision-making. We believe that simultaneously measuring indicators of the three pillars of sustainability (environmentally sound, social responsible and economically viable) in an effectively integrated monitoring system will ultimately allow scientists and land managers alike to find solutions to the most pressing problems facing global food security. This journal is © The Royal Society of Chemistry 2012

Investigation by response surface methodology of the combined effect of pH and composition of water-methanol mixtures on the stability of curcuminoids.

PubMed

D'Archivio, Angelo Antonio; Maggi, Maria Anna

2017-03-15

Response surface methodology, coupled to a full factorial three-level experimental design, was applied to investigate the combined influence of pH (between 7.0 and 8.6) and composition of methanol-water mixtures (between 30 and 70% v/v of methanol content) on the stability of curcumin and its analogues demethoxycurcumin and bisdemethoxycurcumin. The response plots revealed that addition of methanol noticeably improved the stability of curcuminoids, this effect being both pH- and structure-dependent. In the central point of the experimental domain, half-life times of curcumin, demethoxycurcumin and bisdemethoxycurcumin were 3.8±0.2, 27±2 and 251±17h, respectively. Stability of curcuminoids increased at lower pH and higher methanol content and decreased in the opposite vertex of the experimental domain. These results can be interpreted by assuming that addition of methanol to water produces a different variation of pH of the medium and apparent pKa values of the ionisable groups of curcuminoids. Copyright © 2016 Elsevier Ltd. All rights reserved.

A novel CuO-N-doped graphene nanocomposite-based hybrid electrode for the electrochemical detection of glucose

NASA Astrophysics Data System (ADS)

Felix, Sathiyanathan; Kollu, Pratap; Jeong, Soon Kwan; Grace, Andrews Nirmala

2017-10-01

We report a catalyst of N-doped graphene CuO nanocomposite, for the non-enzymatic electrocatalytic oxidation of glucose. The hybrid nanocomposite was synthesized by copper sulfate, cetyl ammonium bromide and graphite as starting materials. The synthesized composites were characterized with the techniques like X-ray diffraction, field emission scanning electron microscopy, transmission electron microscope to study the crystalline phase and morphological structure. Based on this composite, a non-enzymatic glucose sensor was constructed. Cyclic voltammetry and chronoamperometry methods were done to investigate the electrocatalytic properties of glucose in alkaline medium. For glucose detection, the fabricated sensor showed a linear response over a wide range of concentration from 3 to 1000 µM, with sensitivity of 2365.7 µA mM-1 cm-2 and a fast response time of 5 s. The designed sensor exhibited negligible current response to the normal concentration of common interferents in the presence of glucose. All these favorable advantages of the fabricated glucose sensor suggest that it may have good potential application in biological samples, food and other related areas.

Optimization of the ultrasound-assisted extraction of anthocyanins and total phenolic compounds in mulberry (Morus nigra) pulp.

PubMed

Espada-Bellido, Estrella; Ferreiro-González, Marta; Carrera, Ceferino; Palma, Miguel; Barroso, Carmelo G; Barbero, Gerardo F

2017-03-15

New ultrasound-assisted extraction methods for the determination of anthocyanins and total phenolic compounds present in mulberries have been developed. Several extraction variables, including methanol composition (50-100%), temperature (10-70°C), ultrasound amplitude (30-70%), cycle (0.2-0.7s), solvent pH (3-7) and solvent-solid ratio (10:1.5-20:1.5) were optimized. A Box-Behnken design in conjunction with a response surface methodology was employed to optimize the conditions for the maximum response based on 54 different experiments. Two response variables were considered: total anthocyanins and total phenolic compounds. Extraction temperature and solvent composition were found to be the most influential parameters for anthocyanins (48°C and 76%) and phenolic compounds (64°C and 61%). The developed methods showed high reproducibility and repeatability (RSD<5%). Finally, the new methods were successfully applied to real samples in order to investigate the presence of anthocyanins and total phenolic compounds in several mulberry jams. Copyright © 2016 Elsevier Ltd. All rights reserved.

Chlorobaculum tepidum Modulates Amino Acid Composition in Response to Energy Availability, as Revealed by a Systematic Exploration of the Energy Landscape of Phototrophic Sulfur Oxidation.

PubMed

Levy, Amalie T; Lee, Kelvin H; Hanson, Thomas E

2016-11-01

Microbial sulfur metabolism, particularly the formation and consumption of insoluble elemental sulfur (S 0 ), is an important biogeochemical engine that has been harnessed for applications ranging from bioleaching and biomining to remediation of waste streams. Chlorobaculum tepidum, a low-light-adapted photoautolithotrophic sulfur-oxidizing bacterium, oxidizes multiple sulfur species and displays a preference for more reduced electron donors: sulfide > S 0 > thiosulfate. To understand this preference in the context of light energy availability, an "energy landscape" of phototrophic sulfur oxidation was constructed by varying electron donor identity, light flux, and culture duration. Biomass and cellular parameters of C. tepidum cultures grown across this landscape were analyzed. From these data, a correction factor for colorimetric protein assays was developed, enabling more accurate biomass measurements for C. tepidum, as well as other organisms. C. tepidum's bulk amino acid composition correlated with energy landscape parameters, including a tendency toward less energetically expensive amino acids under reduced light flux. This correlation, paired with an observation of increased cell size and storage carbon production under electron-rich growth conditions, suggests that C. tepidum has evolved to cope with changing energy availability by tuning its proteome for energetic efficiency and storing compounds for leaner times. How microbes cope with and adapt to varying energy availability is an important factor in understanding microbial ecology and in designing efficient biotechnological processes. We explored the response of a model phototrophic organism, Chlorobaculum tepidum, across a factorial experimental design that enabled simultaneous variation and analysis of multiple growth conditions, what we term the "energy landscape." C. tepidum biomass composition shifted toward less energetically expensive amino acids at low light levels. This observation provides experimental evidence for evolved efficiencies in microbial proteomes and emphasizes the role that energy flux may play in the adaptive responses of organisms. From a practical standpoint, our data suggest that bulk biomass amino acid composition could provide a simple proxy to monitor and identify energy stress in microbial systems. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

Chlorobaculum tepidum Modulates Amino Acid Composition in Response to Energy Availability, as Revealed by a Systematic Exploration of the Energy Landscape of Phototrophic Sulfur Oxidation

PubMed Central

2016-01-01

ABSTRACT Microbial sulfur metabolism, particularly the formation and consumption of insoluble elemental sulfur (S0), is an important biogeochemical engine that has been harnessed for applications ranging from bioleaching and biomining to remediation of waste streams. Chlorobaculum tepidum, a low-light-adapted photoautolithotrophic sulfur-oxidizing bacterium, oxidizes multiple sulfur species and displays a preference for more reduced electron donors: sulfide > S0 > thiosulfate. To understand this preference in the context of light energy availability, an “energy landscape” of phototrophic sulfur oxidation was constructed by varying electron donor identity, light flux, and culture duration. Biomass and cellular parameters of C. tepidum cultures grown across this landscape were analyzed. From these data, a correction factor for colorimetric protein assays was developed, enabling more accurate biomass measurements for C. tepidum, as well as other organisms. C. tepidum's bulk amino acid composition correlated with energy landscape parameters, including a tendency toward less energetically expensive amino acids under reduced light flux. This correlation, paired with an observation of increased cell size and storage carbon production under electron-rich growth conditions, suggests that C. tepidum has evolved to cope with changing energy availability by tuning its proteome for energetic efficiency and storing compounds for leaner times. IMPORTANCE How microbes cope with and adapt to varying energy availability is an important factor in understanding microbial ecology and in designing efficient biotechnological processes. We explored the response of a model phototrophic organism, Chlorobaculum tepidum, across a factorial experimental design that enabled simultaneous variation and analysis of multiple growth conditions, what we term the “energy landscape.” C. tepidum biomass composition shifted toward less energetically expensive amino acids at low light levels. This observation provides experimental evidence for evolved efficiencies in microbial proteomes and emphasizes the role that energy flux may play in the adaptive responses of organisms. From a practical standpoint, our data suggest that bulk biomass amino acid composition could provide a simple proxy to monitor and identify energy stress in microbial systems. PMID:27565613

Exploring the applicability and limitations of selected optical scattering instruments for PM mass measurement

NASA Astrophysics Data System (ADS)

Zhang, Jie; Marto, Joseph P.; Schwab, James J.

2018-05-01

Two optical scattering instruments for particle mass measurement, the Thermo Personal Data RAM (PDR-1500) and the TSI Environmental DustTrak DRX (Model 8543) were evaluated by (1) using poly- and mono-disperse test aerosol in the laboratory, and (2) sampling ambient aerosol. The responses of these optical scattering instruments to different particle characteristics (size, composition, concentration) were compared with responses from reference instruments. A Mie scattering calculation was used to explain the dependence of the optical instruments' response to aerosol size and composition. Concurrently, the detection efficiency of one Alphasense Optical Particle Counter (OPC-N2) was evaluated in the laboratory as well. The relationship between aerosol mass concentration and optical scattering was determined to be strongly dependent on aerosol size and to a lesser extent on aerosol composition (as reflected in the refractive indices of the materials tested) based on ambient measurements. This confirms that there is no simple way to use optical scattering instruments over a wide range of conditions without adjustments based on knowledge of aerosol size and composition. In particular, a test period measuring ambient aerosol with optical scattering instruments and a mass based method (an Aerodyne Aerosol Mass Spectrometer) determined that roughly two thirds of the variance (R2 = 0.64) of the optical to mass signal ratio is explained by the aerosol mass median diameter alone. These observations and calculations help evaluate the applicability and limitations of these optical scattering instruments, and provide guidance to designing suitable applications for each instrument by considering aerosol sources and aerosol size.

Ultrasonic Resonance Spectroscopy of Composite Rims for Flywheel Rotors

NASA Technical Reports Server (NTRS)

Harmon, Laura M.; Baaklini, George Y.

2002-01-01

Flywheel energy storage devices comprising multilayered composite rotor systems are being studied extensively for utilization in the International Space Station. These composite material systems were investigated with a recently developed ultrasonic resonance spectroscopy technique. The ultrasonic system employs a continuous swept-sine waveform and performs a fast Fourier transform (FFT) on the frequency response spectrum. In addition, the system is capable of equalizing the amount of energy at each frequency. Equalization of the frequency spectrum, along with interpretation of the second FFT, aids in the evaluation of the fundamental frequency. The frequency responses from multilayered material samples, with and without known defects, were analyzed to assess the capabilities and limitations of this nondestructive evaluation technique for material characterization and defect detection. Amplitude and frequency changes were studied from ultrasonic responses of thick composite rings and a multiring composite rim. A composite ring varying in thickness was evaluated to investigate the full thickness resonance. The frequency response characteristics from naturally occurring voids in a composite ring were investigated. Ultrasonic responses were compared from regions with and without machined voids in a composite ring and a multiring composite rim. Finally, ultrasonic responses from the multiring composite rim were compared before and after proof spin testing to 63,000 rpm.

Bioactive Polymeric Composites for Tooth Mineral Regeneration: Physicochemical and Cellular Aspects

PubMed Central

Skrtic, Drago; Antonucci, Joseph M.

2011-01-01

Our studies of amorphous calcium phosphate (ACP)-based dental materials are focused on the design of bioactive, non-degradable, biocompatible, polymeric composites derived from acrylic monomer systems and ACP by photochemical or chemically activated polymerization. Their intended uses include remineralizing bases/liners, orthodontic adhesives and/or endodontic sealers. The bioactivity of these materials originates from the propensity of ACP, once exposed to oral fluids, to release Ca and PO4 ions (building blocks of tooth and bone mineral) in a sustained manner while spontaneously converting to thermodynamically stable apatite. As a result of ACP's bioactivity, local Ca- and PO4-enriched environments are created with supersaturation conditions favorable for the regeneration of tooth mineral lost to decay or wear. Besides its applicative purpose, our research also seeks to expand the fundamental knowledge base of structure-composition-property relationships existing in these complex systems and identify the mechanisms that govern filler/polymer and composite/tooth interfacial phenomena. In addition to an extensive physicochemical evaluation, we also assess the leachability of the unreacted monomers and in vitro cellular responses to these types of dental materials. The systematic physicochemical and cellular assessments presented in this study typically provide model materials suitable for further animal and/or clinical testing. In addition to their potential dental clinical value, these studies suggest the future development of calcium phosphate-based biomaterials based on composite materials derived from biodegradable polymers and ACP, and designed primarily for general bone tissue regeneration. PMID:22102967

Evaluation of a Composite Sandwich Fuselage Side Panel with Damage and Subjected to Internal Pressure

NASA Technical Reports Server (NTRS)

Rouse, Marshall; Ambur, Damodar R.; Bodine, Jerry; Dopker, Bernhard

1997-01-01

The results from an experimental and analytical study of a composite sandwich fuselage side panel for a transport aircraft are presented. The panel has two window cutouts and three frames, and has been evaluated with internal pressure loads that generate biaxial tension loading conditions. Design limit load and design ultimate load tests have been performed on the graphite-epoxy sandwich panel with the middle frame removed to demonstrate the suitability of this two-frame design for supporting the prescribed biaxial loading conditions with twice the initial frame spacing of 20 inches. The two-frame panel was damaged by cutting a notch that originates at the edge of a cutout and extends in the panel hoop direction through the window-belt area. This panel with a notch was tested in a combined-load condition to demonstrate the structural damage tolerance at the design limit load condition. The two panel configurations successfully satisfied all design load requirements in the experimental part of the study, and the three-frame and two-frame panel responses are fully explained by the analysis results. The results of this study suggest that there is potential for using sandwich structural concepts with greater than the usual 20-in.-wide frame spacing to further reduce aircraft fuselage structural weight.

Experimental design data for the biosynthesis of citric acid using Central Composite Design method.

PubMed

Kola, Anand Kishore; Mekala, Mallaiah; Goli, Venkat Reddy

2017-06-01

In the present investigation, we report that statistical design and optimization of significant variables for the microbial production of citric acid from sucrose in presence of filamentous fungi A. niger NCIM 705. Various combinations of experiments were designed with Central Composite Design (CCD) of Response Surface Methodology (RSM) for the production of citric acid as a function of six variables. The variables are; initial sucrose concentration, initial pH of medium, fermentation temperature, incubation time, stirrer rotational speed, and oxygen flow rate. From experimental data, a statistical model for this process has been developed. The optimum conditions reported in the present article are initial concentration of sucrose of 163.6 g/L, initial pH of medium 5.26, stirrer rotational speed of 247.78 rpm, incubation time of 8.18 days, fermentation temperature of 30.06 °C and flow rate of oxygen of 1.35 lpm. Under optimum conditions the predicted maximum citric acid is 86.42 g/L. The experimental validation carried out under the optimal values and reported citric acid to be 82.0 g/L. The model is able to represent the experimental data and the agreement between the model and experimental data is good.

Experimental design for a basic mixture on a fluorinated packing. The effect of composition of the mobile phase.

PubMed

Wang, Y; Harrison, M; Clark, B J

2006-02-10

An optimization methodology is introduced for investigating the separation and the retention behavior of analytes on a new fluorinated reversed-phase packing. Ten basic compounds were selected as test probes to study the predictive models developed by using SPSS and MATLAB software. A two-level orthogonal array design (OAD) was used to extract significant parameters. The significant factors were optimised using a central composite design to obtain the quadratic relationship between the dependent and the independent variables. Using this strategy, response surfaces were derived as the 3D and contour plots, and mathematical models were defined for the separation. The models had a satisfactory coefficient (R(2) > 0.97, n = 16). For the test compounds, the best separation condition was: MeCN/30 mM phosphate buffer pH 7.1(55.5:44.5, v/v) and 10 basic solutes were resolved in 22 min. The significant influence of the concentration of buffer shows that different mechanisms of separation for basic compounds on the fluorinated packing exist compared with a common ODS stationary phase.

Emission of volatile aldehydes and ketones from wood pellets under controlled conditions.

PubMed

Arshadi, Mehrdad; Geladi, Paul; Gref, Rolf; Fjällström, Pär

2009-11-01

Different qualities of biofuel pellets were made from pine and spruce sawdust according to an industrial experimental design. The fatty/resin acid compositions were determined by gas chromatography-mass spectrometry for both newly produced pellets and those after 2 and 4 weeks of storage. The aldehydes/ketones compositions were determined by high performance liquid chromatography at 0, 2, and 4 weeks. The designs were analyzed for the response variables: total fatty/resin acids and total aldehydes/ketones. The design showed a strong correlation between the pine fraction in the pellets and the fatty/resin acid content but the influence decreased over storage time. The amount of fatty/resin acids decreased approximately 40% during 4 weeks. The influence of drying temperature on the aldehyde/ketone emission of fresh pellets was also shown. The amounts of emitted aldehydes/ketones generally decreased by 45% during storage as a consequence of fatty/resin acid oxidation. The matrices of individual concentrations were subjected to multivariate data analysis. This showed clustering of the different experimental runs and demonstrated the important mechanism of fatty/resin acid conversion.

On the dynamic response at the wheel axle of a pneumatic tire

NASA Astrophysics Data System (ADS)

Kung, L. E.; Soedel, W.; Yang, T. Y.

1986-06-01

A method for calculating the steady state displacement response and force transmission at the wheel axle of a pneumatic tire-suspension system due to a steady state force or displacement excitation at the tire to ground contact point is developed. The method requires the frequency responses (or receptances)_of both tire-wheel and suspension units. The frequency response of the tire-wheel unit is obtained by using the modal expansion method. The natural frequencies and mode shapes of the tire-wheel unit are obtained by using a geometrically non-linear, ring type, thin shell finite element of laminate composite. The frequency response of the suspension unit is obtained analytically. These frequency responses are used to calculate the force-input and the displacement-input responses at the wheel axle. This method allows the freedom of designing a vehicle and its tires independently and still achieving optimum dynamic performance.

Third Conference on Fibrous Composites in Flight Vehicle Design, part 1

NASA Technical Reports Server (NTRS)

1976-01-01

The use of fibrous composite materials in the design of aircraft and space vehicle structures and their impact on future vehicle systems are discussed. The topics covered include: flight test work on composite components, design concepts and hardware, specialized applications, operational experience, certification and design criteria. Contributions to the design technology base include data concerning material properties, design procedures, environmental exposure effects, manufacturing procedures, and flight service reliability. By including composites as baseline design materials, significant payoffs are expected in terms of reduced structural weight fractions, longer structural life, reduced fuel consumption, reduced structural complexity, and reduced manufacturing cost.

Impact of Isolation and Immobilization Layers on the Electro-Mechanical Response of Piezoresistive Nano Cantilever Sensors.

PubMed

Mathew, Ribu; Sankar, A Ravi

2018-03-01

In the last decade, piezoresistive nano cantilever sensors have been extensively explored, especially for chemical and biological sensing applications. Piezoresistive cantilever sensors are multi-layer structures with different constituent materials. Performance of such sensors is a function of their geometry and constituent materials. For a fixed material set, the pre-requisite for optimizing the performance of a composite piezoresistive cantilever sensor is careful geometrical design of its constituent layers. Even though, treatise encompasses various designs of such sensors, typically for computational simplicity the functional layers i.e., the isolation and immobilization layers are neglected in the modeling stages. In this paper, we elucidate the impact of the functional layers on the electro-mechanical response of composite piezoresistive nano cantilever sensors. Systematic and detailed computations are performed using theoretical models and numerical simulations. Results show that both the isolation and immobilization layers play a critical role in governing the sensor performance. Simulation results depict that compared to a sensor with an isolation layer of thickness 100 nm, a sensor without isolation layer has 36.29% and 42.51% better deflection sensitivity and electrical sensitivity respectively. Furthermore, it is found that when an immobilization layer of thickness 40 nm is added atop the isolation layer, the deflection sensitivity and electrical sensitivity reduces by 12.98% and 15.83% respectively. Through our investigation it is shown that the isolation and immobilization layers not only play a vital role in determining the stability and electro-mechanical response of the sensor but their negligence in the design stages can be detrimental. Apart from investigating the impact of the immobilization layer thickness, to model the sensor closer to real time operational conditions, we have performed analysis to understand the impact of non-uniformity in the immobilization layer thickness and non-uniform surface stress loading on the electro-mechanical response of the sensor. Results and inferences obtained from this study will help NEMS engineers to optimize the performance of piezoresistive nano cantilever sensors and to design multi-layer cantilever platform structures for other transducers.

Effect of prior meal macronutrient composition on postprandial glycemic responses and glycemic index and glycemic load value determinations.

PubMed

Meng, Huicui; Matthan, Nirupa R; Ausman, Lynne M; Lichtenstein, Alice H

2017-11-01

Background: The potential impact of prior meal composition on the postprandial glycemic response and glycemic index (GI) and glycemic load (GL) value determinations remains unclear. Objective: We determined the effect of meals that varied in macronutrient composition on the glycemic response and determination of GI and GL values of a subsequent standard test food. Design: Twenty healthy participants underwent 6 test sessions within 12 wk. The subjects received each of 3 isocaloric breakfast meals (i.e., high carbohydrate, high fat, or high protein) on separate days in a random order, which was followed by a standard set of challenges (i.e., white bread and a glucose drink) that were tested on separate days in a random order 4 h thereafter. Each challenge provided 50 g available carbohydrate. Arterialized venous blood was sampled throughout the 2-h postchallenge period. GI, GL, and insulin index (II) values were calculated with the use of the incremental area under the curve (AUC i ) method, and serum lipids were determined with the use of standard assays. Results: The consumption of the high-protein breakfast before the white-bread challenge attenuated the rise in the postprandial serum glucose response ( P < 0.0001) and resulted in lower glucose AUC i ( P < 0.0001), GI ( P = 0.0096), and GL ( P = 0.0101) values than did the high-carbohydrate and high-fat breakfasts. The high-protein breakfast resulted in a lower insulin AUC i ( P = 0.0146) for white bread than did the high-fat breakfast and a lower II value ( P = 0.0285) than did the high-carbohydrate breakfast. The 3 breakfasts resulted in similar serum lipid responses to the white-bread challenge. Conclusions: These data indicate that the macronutrient composition of the prior meal influences the glycemic response and the determination of GI and GL values for white bread. Future studies are needed to determine whether the background food macronutrient composition influences mean dietary GI and GL values that are calculated for eating patterns, which may alter the interpretation of the associations between these values and chronic disease risk. This trial was registered at clinicaltrials.gov as NCT01023646. © 2017 American Society for Nutrition.

Critical Needs for Robust and Reliable Database for Design and Manufacturing of Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Singh, M.

1999-01-01

Ceramic matrix composite (CMC) components are being designed, fabricated, and tested for a number of high temperature, high performance applications in aerospace and ground based systems. The critical need for and the role of reliable and robust databases for the design and manufacturing of ceramic matrix composites are presented. A number of issues related to engineering design, manufacturing technologies, joining, and attachment technologies, are also discussed. Examples of various ongoing activities in the area of composite databases. designing to codes and standards, and design for manufacturing are given.

Optimization of Perovskite Gas Sensor Performance: Characterization, Measurement and Experimental Design.

PubMed

Bertocci, Francesco; Fort, Ada; Vignoli, Valerio; Mugnaini, Marco; Berni, Rossella

2017-06-10

Eight different types of nanostructured perovskites based on YCoO 3 with different chemical compositions are prepared as gas sensor materials, and they are studied with two target gases NO 2 and CO. Moreover, a statistical approach is adopted to optimize their performance. The innovative contribution is carried out through a split-plot design planning and modeling, also involving random effects, for studying Metal Oxide Semiconductors (MOX) sensors in a robust design context. The statistical results prove the validity of the proposed approach; in fact, for each material type, the variation of the electrical resistance achieves a satisfactory optimized value conditional to the working temperature and by controlling for the gas concentration variability. Just to mention some results, the sensing material YCo 0 . 9 Pd 0 . 1 O 3 (Mt1) achieved excellent solutions during the optimization procedure. In particular, Mt1 resulted in being useful and feasible for the detection of both gases, with optimal response equal to +10.23% and working temperature at 312 ∘ C for CO (284 ppm, from design) and response equal to -14.17% at 185 ∘ C for NO 2 (16 ppm, from design). Analogously, for NO 2 (16 ppm, from design), the material type YCo 0 . 9 O 2 . 85 + 1 % Pd (Mt8) allows for optimizing the response value at - 15 . 39 % with a working temperature at 181 . 0 ∘ C, whereas for YCo 0 . 95 Pd 0 . 05 O 3 (Mt3), the best response value is achieved at - 15 . 40 % with the temperature equal to 204 ∘ C.

Optimization of Perovskite Gas Sensor Performance: Characterization, Measurement and Experimental Design

PubMed Central

Bertocci, Francesco; Fort, Ada; Vignoli, Valerio; Mugnaini, Marco; Berni, Rossella

2017-01-01

Eight different types of nanostructured perovskites based on YCoO3 with different chemical compositions are prepared as gas sensor materials, and they are studied with two target gases NO2 and CO. Moreover, a statistical approach is adopted to optimize their performance. The innovative contribution is carried out through a split-plot design planning and modeling, also involving random effects, for studying Metal Oxide Semiconductors (MOX) sensors in a robust design context. The statistical results prove the validity of the proposed approach; in fact, for each material type, the variation of the electrical resistance achieves a satisfactory optimized value conditional to the working temperature and by controlling for the gas concentration variability. Just to mention some results, the sensing material YCo0.9Pd0.1O3 (Mt1) achieved excellent solutions during the optimization procedure. In particular, Mt1 resulted in being useful and feasible for the detection of both gases, with optimal response equal to +10.23% and working temperature at 312∘C for CO (284 ppm, from design) and response equal to −14.17% at 185∘C for NO2 (16 ppm, from design). Analogously, for NO2 (16 ppm, from design), the material type YCo0.9O2.85+1%Pd (Mt8) allows for optimizing the response value at −15.39% with a working temperature at 181.0∘C, whereas for YCo0.95Pd0.05O3 (Mt3), the best response value is achieved at −15.40% with the temperature equal to 204∘C. PMID:28604587

Innovative Composite Structure Design for Blast Protection

DTIC Science & Technology

2007-01-01

2007-01-0483 Innovative Composite Structure Design for Blast Protection Dongying Jiang, Yuanyuan Liu MKP Structural Design Associates, Inc...protect vehicle and occupants against various explosives. The multi-level and multi-scenario blast simulation and design system integrates three major...numerical simulation of a BTR composite under a blast event. The developed blast simulation and design system will enable the prediction, design, and

Eighth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, Part 2

NASA Technical Reports Server (NTRS)

Starnes, James H., Jr. (Compiler); Bohon, Herman L. (Compiler); Garzon, Sherry B. (Compiler)

1990-01-01

Papers presented at the conference are compiled. The conference provided a forum for the scientific community to exchange composite structures design information and an opportunity to observe recent progress in composite structures design and technology. Part 2 contains papers related to the following subject areas: the application in design; methodology in design; and reliability in design.

Damage tolerant functionally graded materials for advanced wear and friction applications

NASA Astrophysics Data System (ADS)

Prchlik, Lubos

The research work presented in this dissertation focused on processing effects, microstructure development, characterization and performance evaluation of composite and graded coatings used for friction and wear control. The following issues were addressed. (1) Definition of prerequisites for a successful composite and graded coating formation by means of thermal spraying. (2) Improvement of characterization methods available for homogenous thermally sprayed coating and their extension to composite and graded materials. (3) Development of novel characterization methods specifically for FGMs, with a focus on through thickness property measurement by indentation and in-situ curvature techniques. (4) Design of composite materials with improved properties compared to homogenous coatings. (5) Fabrication and performance assessment of FGM with improved wear and impact damage properties. Materials. The materials studied included several material systems relevant to low friction and contact damage tolerant applications: MO-Mo2C, WC-Co cermets as materials commonly used sliding components of industrial machinery and NiCrAlY/8%-Yttria Partially Stabilized Zirconia composites as a potential solution for abradable sections of gas turbines and aircraft engines. In addition, uniform coatings such as molybdenum and Ni5%Al alloy were evaluated as model system to assess the influence of microstructure variation onto the mechanical property and wear response. Methods. The contact response of the materials was investigated through several techniques. These included methods evaluating the relevant intrinsic coating properties such as elastic modulus, residual stress, fracture toughness, scratch resistance and tests measuring the abrasion and friction-sliding behavior. Dry-sand and wet two-body abrasion testing was performed in addition to traditional ball on disc sliding tests. Among all characterization techniques the spherical indentation deserved most attention and enabled to measure elastic-plastic properties of uniform and graded structures. In-situ curvature method used for residual stress and elastic modulus measurement was extended from uniform coatings to coatings with compositional/property gradients. Properties of composite and graded materials were measured using the inverse analysis. Conclusions. The specifics of the elastic-plastic response for thermally sprayed coatings were demonstrated. These included the strain dependence of elastic modulus and damage accumulation related to unloading/reloading loop formation. The measurement of elastic-plastic characteristics of composite coatings revealed the mixing and bonding mechanisms unique for thermally sprayed materials. Microstructural and compositional factors governing the frictional vs. abrasion response of carbide-metallic composite coatings were described. The measurement of abrasion resistance and friction sliding properties demonstrated that grading of cermet and ceramic coatings by adding moderate amount of metallic alloys can enhance elastic-properties radically and have a beneficial effect onto the coating performance.

Fiber-optically sensorized composite wing

NASA Astrophysics Data System (ADS)

Costa, Joannes M.; Black, Richard J.; Moslehi, Behzad; Oblea, Levy; Patel, Rona; Sotoudeh, Vahid; Abouzeida, Essam; Quinones, Vladimir; Gowayed, Yasser; Soobramaney, Paul; Flowers, George

2014-04-01

Electromagnetic interference (EMI) immune and light-weight, fiber-optic sensor based Structural Health Monitoring (SHM) will find increasing application in aerospace structures ranging from aircraft wings to jet engine vanes. Intelligent Fiber Optic Systems Corporation (IFOS) has been developing multi-functional fiber Bragg grating (FBG) sensor systems including parallel processing FBG interrogators combined with advanced signal processing for SHM, structural state sensing and load monitoring applications. This paper reports work with Auburn University on embedding and testing FBG sensor arrays in a quarter scale model of a T38 composite wing. The wing was designed and manufactured using fabric reinforced polymer matrix composites. FBG sensors were embedded under the top layer of the composite. Their positions were chosen based on strain maps determined by finite element analysis. Static and dynamic testing confirmed expected response from the FBGs. The demonstrated technology has the potential to be further developed into an autonomous onboard system to perform load monitoring, SHM and Non-Destructive Evaluation (NDE) of composite aerospace structures (wings and rotorcraft blades). This platform technology could also be applied to flight testing of morphing and aero-elastic control surfaces.

High strain rate behavior of a SiC particulate reinforced Al{sub 2}O{sub 3} ceramic matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hall, I.W.; Guden, M.

The high strain rate deformation behavior of composite materials is important for several reasons. First, knowledge of the mechanical properties of composites at high strain rates is needed for designing with these materials in applications where sudden changes in loading rates are likely to occur. Second, knowledge of both the dynamic and quasi-static mechanical responses can be used to establish the constitutive equations which are necessary to increase the confidence limits of these materials, particularly if they are to be used in critical structural applications. Moreover, dynamic studies and the knowledge gained form them are essential for the further developmentmore » of new material systems for impact applications. In this study, the high strain rate compressive deformation behavior of a ceramic matrix composite (CMC) consisting of SiC particles and an Al{sub 2}O{sub 3} matrix was studied and compared with its quasi-static behavior. Microscopic observations were conducted to investigate the deformation and fracture mechanism of the composite.« less

Thermal design of composite materials high temperature attachments

NASA Technical Reports Server (NTRS)

1972-01-01

The thermal aspects of using filamentary composite materials as primary airframe structures on advanced atmospheric entry spacecraft such as the space shuttle vehicle were investigated to identify and evaluate potential design approaches for maintaining composite structures within allowable temperature limits at thermal protection system (TPS) attachments and/or penetrations. The investigation included: (1) definition of thermophysical data for composite material structures; (2) parametric characterization and identification of the influence of the aerodynamic heating and attachment design parameters on composite material temperatures; (3) conceptual design, evaluation, and detailed thermal analyses of temperature limiting design concepts; and (4) the development of experimental data for assessment of the thermal design methodologies and data used for evaluation of the temperature-limiting design concepts. Temperature suppression attachment concepts were examined for relative merit. The simple isolator was identified as the most weight-effective concept and was selected for detail design, thermal analysis, and testing. Tests were performed on TPS standoff attachments to boron/aluminum, boron/polyimide and graphite/epoxy composite structures.

Effect of C/N Ratio and Media Optimization through Response Surface Methodology on Simultaneous Productions of Intra- and Extracellular Inulinase and Invertase from Aspergillus niger ATCC 20611

PubMed Central

Dinarvand, Mojdeh; Rezaee, Malahat; Masomian, Malihe; Jazayeri, Seyed Davoud; Zareian, Mohsen; Abbasi, Sahar; Ariff, Arbakariya B.

2013-01-01

The study is to identify the extraction of intracellular inulinase (exo- and endoinulinase) and invertase as well as optimization medium composition for maximum productions of intra- and extracellular enzymes from Aspergillus niger ATCC 20611. From two different methods for extraction of intracellular enzymes, ultrasonic method was found more effective. Response surface methodology (RSM) with a five-variable and three-level central composite design (CCD) was employed to optimize the medium composition. The effect of five main reaction parameters including sucrose, yeast extract, NaNO3, Zn+2, and Triton X-100 on the production of enzymes was analyzed. A modified quadratic model was fitted to the data with a coefficient of determination (R 2) more than 0.90 for all responses. The intra-extracellular inulinase and invertase productions increased in the range from 16 to 8.4 times in the optimized medium (10% (w/v) sucrose, 2.5% (w/v) yeast extract, 2% (w/v) NaNO3, 1.5 mM (v/v) Zn+2, and 1% (v/v) Triton X-100) by RSM and from around 1.2 to 1.3 times greater than in the medium optimized by one-factor-at-a-time, respectively. The results of bioprocesses optimization can be useful in the scale-up fermentation and food industry. PMID:24151605

Design considerations for fiber composite structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1972-01-01

An overview of the design methodology for designing structural components from fiber composites is presented. In particular, the need for new conceptual structural designs for the future is discussed and the evolution of conceptual design is illustrated. Sources of design data, analysis and design procedures, and the basic components of structural fiber composites are cited and described. Examples of tradeoff studies and optimum designs are discussed and a simple structure is described in some detail.

Summary of Activities for Health Monitoring of Composite Overwrapped Pressure Vessels

NASA Technical Reports Server (NTRS)

Russell, Rick

2012-01-01

This new start project (FY12-14) will design and demonstrate the ability of nondestructive evaluation sensors for the measurement of stresses on the inner diameter of a Composite Overwrapped Pressure Vessel overwrap. Results will be correlated with other nondestructive evaluation technologies such as Acoustic Emission. The project will build upon a proof of concept study performed at KSC which demonstrated the ability of Magnetic Stress Gages to measure stresses at internal overwraps and upon current acoustic emission research being performed at WSTF; The gages will be produced utilizing Maundering Winding Magnetometer and/or Maundering Winding Magnetometer-array eddy current technology. The proof-of-concept study demonstrated a correlation between the sensor response and pressure or strain. The study also demonstrated the ability of Maundering Winding Magnetometer technology to monitor the stresses in a Composite Overwrapped Pressure Vessel at different orientations and depths. The ultimate goal is to utilize this technology for the health monitoring of Composite Overwrapped Pressure Vessels for all future flight programs.

Simultaneous/Selective Detection of Dopamine and Ascorbic Acid at Synthetic Zeolite-Modified/Graphite-Epoxy Composite Macro/Quasi-Microelectrodes

PubMed Central

Ilinoiu, Elida Cristina; Manea, Florica; Serra, Pier Andrea; Pode, Rodica

2013-01-01

The present paper aims to miniaturize a graphite-epoxy and synthetic zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of dopamine (DA) and ascorbic acid (AA) neurotransmitters, or DA detection in the presence of AA. The electrochemical behavior and the response of the designed materials to the presence of dopamine and ascorbic acid without any protective membranes were studied by cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this analyte detection, besides a possible electrostatic attraction between dopamine cation and the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode gave the best electroanalytical parameters for dopamine detection using constant-potential amperometry, the most useful technique for practical applications. PMID:23736851

Simultaneous/selective detection of dopamine and ascorbic acid at synthetic zeolite-modified/graphite-epoxy composite macro/quasi-microelectrodes.

PubMed

Ilinoiu, Elida Cristina; Manea, Florica; Serra, Pier Andrea; Pode, Rodica

2013-06-03

The present paper aims to miniaturize a graphite-epoxy and synthetic zeolite-modified graphite-epoxy composite macroelectrode as a quasi-microelectrode aiming in vitro and also, envisaging in vivo simultaneous electrochemical detection of dopamine (DA) and ascorbic acid (AA) neurotransmitters, or DA detection in the presence of AA. The electrochemical behavior and the response of the designed materials to the presence of dopamine and ascorbic acid without any protective membranes were studied by cyclic voltammetry and constant-potential amperometry techniques. The catalytic effect towards dopamine detection was proved for the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode, allowing increasing the sensitivity and selectivity for this analyte detection, besides a possible electrostatic attraction between dopamine cation and the negative surface of the synthetic zeolite and electrostatic repulsion with ascorbic acid anion. Also, the synthetic zeolite-modified graphite-epoxy composite quasi-microelectrode gave the best electroanalytical parameters for dopamine detection using constant-potential amperometry, the most useful technique for practical applications.

Structural Design and Analysis of a Light-Weight Laminated Composite Heat Sink for Spaceflight PWBs

NASA Technical Reports Server (NTRS)

Fan, Mark S.; Niemeyer, W. Lee

1997-01-01

In order to reduce the overall weight in spaceborne electronic systems, a conventional metallic heat sink typically used for double-sided printed wiring boards was suggested to be replaced by light-weight and high-strength laminated composite materials. Through technology validation assurance (TVA) approach, it has been successfully demonstrated that using laminated composite heat sink can not only reduce the weight of the heat sink by nearly 50%, but also significantly lower the internal thermally-induced stresses that are largely responsible for potential delamination under cyclic temperature variations. With composite heat sink, both thermal and dynamic performance of the double-sided printed wiring board (PWB) exceeds that of its counterpart with metallic heat sink. Also included in this work is the original contribution to the understanding of creep behavior of the worst-case leadless chip carrier (LCC) surface mount solder joint. This was identified as the interconnection most susceptible to thermal fatigue damage in the PWB assembly.

Stability of halophilic proteins: from dipeptide attributes to discrimination classifier.

PubMed

Zhang, Guangya; Huihua, Ge; Yi, Lin

2013-02-01

To investigate the molecular features responsible for protein halophilicity is of great significance for understanding the structure basis of protein halo-stability and would help to develop a practical strategy for designing halophilic proteins. In this work, we have systematically analyzed the dipeptide composition of the halophilic and non-halophilic protein sequences. We observed the halophilic proteins contained more DA, RA, AD, RR, AP, DD, PD, EA, VG and DV at the expense of LK, IL, II, IA, KK, IS, KA, GK, RK and AI. We identified some macromolecular signatures of halo-adaptation, and thought the dipeptide composition might contain more information than amino acid composition. Based on the dipeptide composition, we have developed a machine learning method for classifying halophilic and non-halophilic proteins for the first time. The accuracy of our method for the training dataset was 100.0%, and for the 10-fold cross-validation was 93.1%. We also discussed the influence of some specific dipeptides on prediction accuracy. Copyright © 2012 Elsevier B.V. All rights reserved.

Structural integrity of power generating speed bumps made of concrete foam composite

NASA Astrophysics Data System (ADS)

Syam, B.; Muttaqin, M.; Hastrino, D.; Sebayang, A.; Basuki, W. S.; Sabri, M.; Abda, S.

2018-02-01

In this paper concrete foam composite speed bumps were designed to generate electrical power by utilizing the movements of commuting vehicles on highways, streets, parking gates, and drive-thru station of fast food restaurants. The speed bumps were subjected to loadings generated by vehicles pass over the power generating mechanical system. In this paper, we mainly focus our discussion on the structural integrity of the speed bumps and discuss the electrical power generating speed bumps in another paper. One aspect of structural integrity is its ability to support designed loads without breaking and includes the study of past structural failures in order to prevent failures in future designs. The concrete foam composites were used for the speed bumps; the reinforcement materials are selected from empty fruit bunch of oil palm. In this study, the speed bump materials and structure were subjected to various tests to obtain its physical and mechanical properties. To analyze the structure stability of the speed bumps some models were produced and tested in our speed bump test station. We also conduct a FEM-based computer simulation to analyze stress responses of the speed bump structures. It was found that speed bump type 1 significantly reduced the radial voltage. In addition, the speed bump is equipped with a steel casing is also suitable for use as a component component in generating electrical energy.

Simulation of mechanical behavior and optimization of simulated injection molding process for PLA based antibacterial composite and nanocomposite bone screws using central composite design.

PubMed

Heidari, Behzad Shiroud; Oliaei, Erfan; Shayesteh, Hadi; Davachi, Seyed Mohammad; Hejazi, Iman; Seyfi, Javad; Bahrami, Mozhgan; Rashedi, Hamid

2017-01-01

In this study, injection molding of three poly lactic acid (PLA) based bone screws was simulated and optimized through minimizing the shrinkage and warpage of the bone screws. The optimization was carried out by investigating the process factors such as coolant temperature, mold temperature, melt temperature, packing time, injection time, and packing pressure. A response surface methodology (RSM), based on the central composite design (CCD), was used to determine the effects of the process factors on the PLA based bone screws. Upon applying the method of maximizing the desirability function, optimization of the factors gave the lowest warpage and shrinkage for nanocomposite PLA bone screw (PLA9). Moreover, PLA9 has the greatest desirability among the selected materials for bone screw injection molding. Meanwhile, a finite element analysis (FE analysis) was also performed to determine the force values and concentration points which cause yielding of the screws under certain conditions. The Von-Mises stress distribution showed that PLA9 screw is more resistant against the highest loads as compared to the other ones. Finally, according to the results of injection molding simulations, the design of experiments (DOE) and structural analysis, PLA9 screw is recommended as the best candidate for the production of biomedical materials among all the three types of screws. Copyright © 2016 Elsevier Ltd. All rights reserved.

Probabilistic Composite Design

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1997-01-01

Probabilistic composite design is described in terms of a computational simulation. This simulation tracks probabilistically the composite design evolution from constituent materials, fabrication process, through composite mechanics and structural components. Comparisons with experimental data are provided to illustrate selection of probabilistic design allowables, test methods/specimen guidelines, and identification of in situ versus pristine strength, For example, results show that: in situ fiber tensile strength is 90% of its pristine strength; flat-wise long-tapered specimens are most suitable for setting ply tensile strength allowables: a composite radome can be designed with a reliability of 0.999999; and laminate fatigue exhibits wide-spread scatter at 90% cyclic-stress to static-strength ratios.

Design for progressive fracture in composite shell structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Murthy, Pappu L. N.

1992-01-01

The load carrying capability and structural behavior of composite shell structures and stiffened curved panels are investigated to provide accurate early design loads. An integrated computer code is utilized for the computational simulation of composite structural degradation under practical loading for realistic design. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. Progressive fracture investigations providing design insight for several classes of composite shells are presented. Results demonstrate the significance of local defects, interfacial regions, and stress concentrations on the structural durability of composite shells.

An investigation into the impact of cryogenic environment on mechanical stresses in FRP composites

NASA Astrophysics Data System (ADS)

Fifo, O.; Basu, B.

2015-07-01

Fibre reinforced polymer (FRP) composites are fast becoming a highly utilised engineering material for high performance applications due to their light weight and high strength. Carbon fibre and other high strength fibres are commonly used in design of aerospace structures, wind turbine blades, etc. and potentially for propellant tanks of launch vehicles. For the aforementioned fields of application, stability of the material is essential over a wide range of temperature particularly for structures in hostile environments. Many studies have been conducted, experimentally, over the last decade to investigate the mechanical behaviour of FRP materials at varying subzero temperature. Likewise, tests on aging and cycling effect (room to low temperature) on the mechanical response of FRP have been reported. However, a relatively lesser focused area has been the mechanical behaviour of FRP composites under cryogenic environment. This article reports a finite element method of investigating the changes in the mechanical characteristics of an FRP material when temperature based analysis falls below zero. The simulated tests are carried out using a finite element package with close material properties used in the cited literatures. Tensile test was conducted and the results indicate that the mechanical responses agree with those reported in the literature sited.

Shear sensing in bonded composites with cantilever beam microsensors and dual-plane digital image correlation

NASA Astrophysics Data System (ADS)

Baur, Jeffery W.; Slinker, Keith; Kondash, Corey

2017-04-01

Understanding the shear strain, viscoelastic response, and onset of damage within bonded composites is critical to their design, processing, and reliability. This presentation will discuss the multidisciplinary research conducted which led to the conception, development, and demonstration of two methods for measuring the shear within a bonded joint - dualplane digital image correlation (DIC) and a micro-cantilever shear sensor. The dual plane DIC method was developed to measure the strain field on opposing sides of a transparent single-lap joint in order to spatially quantify the joint shear strain. The sensor consists of a single glass fiber cantilever beam with a radially-grown forest of carbon nanotubes (CNTs) within a capillary pore. When the fiber is deflected, the internal radial CNT array is compressed against an electrode within the pore and the corresponding decrease in electrical resistance is correlated with the external loading. When this small, simple, and low-cost sensor was integrated within a composite bonded joint and cycled in tension, the onset of damage prior to joint failure was observed. In a second sample configuration, both the dual plane DIC and the hair sensor detected viscoplastic changes in the strain of the sample in response to continued loading.

Gaussian process regression of chirplet decomposed ultrasonic B-scans of a simulated design case

NASA Astrophysics Data System (ADS)

Wertz, John; Homa, Laura; Welter, John; Sparkman, Daniel; Aldrin, John

2018-04-01

The US Air Force seeks to implement damage tolerant lifecycle management of composite structures. Nondestructive characterization of damage is a key input to this framework. One approach to characterization is model-based inversion of the ultrasonic response from damage features; however, the computational expense of modeling the ultrasonic waves within composites is a major hurdle to implementation. A surrogate forward model with sufficient accuracy and greater computational efficiency is therefore critical to enabling model-based inversion and damage characterization. In this work, a surrogate model is developed on the simulated ultrasonic response from delamination-like structures placed at different locations within a representative composite layup. The resulting B-scans are decomposed via the chirplet transform, and a Gaussian process model is trained on the chirplet parameters. The quality of the surrogate is tested by comparing the B-scan for a delamination configuration not represented within the training data set. The estimated B-scan has a maximum error of ˜15% for an estimated reduction in computational runtime of ˜95% for 200 function calls. This considerable reduction in computational expense makes full 3D characterization of impact damage tractable.

Combined tension and bending testing of tapered composite laminates

NASA Astrophysics Data System (ADS)

O'Brien, T. Kevin; Murri, Gretchen B.; Hagemeier, Rick; Rogers, Charles

1994-11-01

A simple beam element used at Bell Helicopter was incorporated in the Computational Mechanics Testbed (COMET) finite element code at the Langley Research Center (LaRC) to analyze the responce of tappered laminates typical of flexbeams in composite rotor hubs. This beam element incorporated the influence of membrane loads on the flexural response of the tapered laminate configurations modeled and tested in a combined axial tension and bending (ATB) hydraulic load frame designed and built at LaRC. The moments generated from the finite element model were used in a tapered laminated plate theory analysis to estimate axial stresses on the surface of the tapered laminates due to combined bending and tension loads. Surfaces strains were calculated and compared to surface strains measured using strain gages mounted along the laminate length. The strain distributions correlated reasonably well with the analysis. The analysis was then used to examine the surface strain distribution in a non-linear tapered laminate where a similarly good correlation was obtained. Results indicate that simple finite element beam models may be used to identify tapered laminate configurations best suited for simulating the response of a composite flexbeam in a full scale rotor hub.

Optimization of diesel oil biodegradation in seawater using statistical experimental methodology.

PubMed

Xia, Wenxiang; Li, Jincheng; Xia, Yan; Song, Zhiwen; Zhou, Jihong

2012-01-01

Petroleum hydrocarbons released into the environment can be harmful to higher organisms, but they can be utilized by microorganisms as the sole source of energy for metabolism. To investigate the optimal conditions of diesel oil biodegradation, the Plackett-Burman (PB) design was used for the optimization in the first step, and N source (NaNO₃), P source (KH₂PO₄) and pH were found to be significant factors affecting oil degradation. Then the response surface methodology (RSM) using a central composite design (CCD) was adopted for the augmentation of diesel oil biodegradation and a fitted quadratic model was obtained. The model F-value of 27.25 and the low probability value (<0.0001) indicate that the model is significant and that the concentration of NaNO₃N, KH₂PO₄ and pH had significant effects on oil removal during the study. Three-dimensional response surface plots were constructed by plotting the response (oil degradation efficiency) on the z-axis against any two independent variables, and the optimal biodegradation conditions of diesel oil (original total petroleum hydrocarbons 125 mg/L) were determined as follows: NaNO₃ 0.143 g, KH₂PO₄ 0.022 g and pH 7.4. These results fit quite well with the C, N and P ratio in biological cells. Results from the present study might provide a new method to estimate the optimal nitrogen and phosphorus concentration in advance for oil biodegradation according to the composition of petroleum.

Design of plasmonic Ag-TiO2/H3PW12O40 composite film with enhanced sunlight photocatalytic activity towards o-chlorophenol degradation.

PubMed

Lu, Nan; Wang, Yaqi; Ning, Shiqi; Zhao, Wenjing; Qian, Min; Ma, Ying; Wang, Jia; Fan, Lingyun; Guan, Jiunian; Yuan, Xing

2017-12-11

A series of plasmonic Ag-TiO 2 /H 3 PW 12 O 40 composite films were fabricated and immobilized by validated preparation technique. The chemical composition and phase, optical, SPR effect and pore-structure properties together with the morphology of as-prepared composite film are well-characterized. The multi-synergies of as-prepared composite films were gained by combined action of electron-capture action via H 3 PW 12 O 40 , visible-response induced by Ag, and Schottky-junction formed between TiO 2 -Ag. Under simulated sunlight, the maximal K app of o-chlorophenol (o-CP) reached 0.0075 min -1 which was 3.95-fold larger than that of TiO 2 film, while it was restrained obviously under acid condition. In the photocatalytic degradation process, ·OH and ·O 2 - attacked preferentially ortho and para position of o-CP molecule, and accordingly the specific degradation pathways were speculated. The novel composite film exhibited an excellent applicability due to self-regeneration of H 3 PW 12 O 40 , well-protection of metal Ag° and favorable immobilization.

Impact Behavior of Composite Fan Blade Leading Edge Subcomponent with Thermoplastic Polyurethane Interleave

NASA Technical Reports Server (NTRS)

Miller, Sandi G.; Roberts, Gary D.; Kohlman, Lee W.; Heimann, Paula J.; Pereira, J. Michael; Ruggeri, Charles R.; Martin, Richard E.; McCorkle, Linda S.

2015-01-01

Impact damage tolerance and damage resistance is a critical metric for application of polymer matrix composites where failure caused by impact damage could compromise structural performance and safety. As a result, several materials and/or design approaches to improve impact damage tolerance have been investigated over the past several decades. Many composite toughening methodologies impart a trade-off between increased fracture toughness and compromised in-plane strength and modulus. In large part, mechanical tests to evaluate composite damage tolerance include static methods such as Mode I, Mode II, and mixed mode failures. However, ballistic impact damage resistance does not always correlate with static properties. The intent of this paper is to evaluate the influence of a thermoplastic polyurethane veil interleave on the static and dynamic performance of composite test articles. Static coupon tests included tension, compression, double cantilever beam, and end notch flexure. Measurement of the resistance to ballistic impact damage were made to evaluate the composites response to high speed impact. The interlayer material showed a decrease of in-plane performance with only a moderate improvement to Mode I and Mode II fracture toughness. However, significant benefit to impact damage tolerance was observed through ballistic tests.

Electrostatic Discharge Testing of Carbon Composite Solar Array Panels for Use in the Jovian Environment

NASA Technical Reports Server (NTRS)

Green, Nelson W.; Dawson, Stephen F.

2015-01-01

NASA is currently considering a mission to investigate the moons of Jupiter. When designing a spacecraft for this type of mission, there are a number of engineering challenges, especially if the mission chooses to utilize solar arrays to provide the spacecraft power. In order for solar arrays to be feasible for the mission, their total mass needed to fit within the total budget for the mission, which strongly suggested the use of carbon composite facesheets on an aluminum core for the panel structure. While these composite structures are a good functional substitution for the metallic materials they replace, they present unique challenges when interacting with the harsh Jovian space environment. As a composite material, they are composed of more than one material and can show different base properties depending in differing conditions. Looking at the electrical properties, in an Earth-based environment the carbon component of the composite dominates the response of the material to external stimulus. Under these conditions, the structures strongly resembles a conductor. In the Jovian environment, with temperatures reaching 50K and under the bombardment from energetic electrons, the non-conducting pre-preg binding materials may come to the forefront and change the perceived response. Before selecting solar arrays as the baseline power source for a mission to Jupiter, the response of the carbon composites to energetic electrons while held at cryogenic temperatures needed to be determined. A series of tests were devised to exam the response of a sample solar array panel composed of an M55J carbon weave layup with an RS-3 pre-preg binder. Test coupons were fabricated and exposed to electrons ranging from 10 keV to 100 keV, at 1 nA/cm2, while being held at cryogenic temperatures. While under electron bombardment, electrical discharges were observed and recorded with the majority of discharges occurring with electron energies of 25 keV. A decrease in temperature to liquid nitrogen temperatures showed a marked increase in the magnitude of these discharges. The results indicate that dielectric discharges are primarily produced due to the presence of large regions of the non-conductive pre-preg on the surface of the carbon sheets. The frequency and magnitude of discharges decreased when layers of the pre-preg material were removed from the composite surface. These tests indicate that solar array panels may be used in the Jovian environment, but that electrostatic discharges can be expected on the carbon composite solar arrays.

Design and In-vitro Evaluation of Sustained Release Floating Tablets of Metformin HCl Based on Effervescence and Swelling

PubMed Central

Senjoti, Faria Gias; Mahmood, Syed; Jaffri, Juliana Md; Mandal, Uttam Kumar

2016-01-01

An oral sustained-release floating tablet formulation of metformin HCl was designed and developed. Effervescence and swelling properties were attributed on the developed tablets by sodium bicarbonate and HPMC-PEO polymer combination, respectively. Tablet composition was optimized by response surface methodology (RSM). Seventeen (17) trial formulations were analyzed according to Box-Behnken design of experiment where polymer content of HPMC and PEO at 1: 4 ratio (A), amount of sodium bi-carbonate (B), and amount of SSG (C) were adopted as independent variables. Floating lag time in sec (Y1), cumulative percent drug released at 1 h (Y2) and 12 h (Y3) were chosen as response variables. Tablets from the optimized formulation were also stored at accelerated stability condition (40°C and 75% RH) for 3 months to assess their stability profile. RSM could efficiently optimize the tablet composition with excellent prediction ability. In-vitro drug release until 12 h, floating lag time, and duration of floating were dependent on the amount of three selected independent variables. Optimized tablets remained floating for more than 24 h with a floating lag time of less than 4 min. Based on best fitting method, optimized formulation was found to follow Korsmeyer-Peppas release kinetic. Accelerated stability study revealed that optimized formulation was stable for three months without any major changes in assay, dissolution profile, floating lag time and other physical properties. PMID:27610147

Development of eddy current probe for fiber orientation assessment in carbon fiber composites

NASA Astrophysics Data System (ADS)

Wincheski, Russell A.; Zhao, Selina

2018-04-01

Measurement of the fiber orientation in a carbon fiber composite material is crucial in understanding the load carrying capability of the structure. As manufacturing conditions including resin flow and molding pressures can alter fiber orientation, verification of the as-designed fiber layup is necessary to ensure optimal performance of the structure. In this work, the development of an eddy current probe and data processing technique for analysis of fiber orientation in carbon fiber composites is presented. A proposed directional eddy current probe is modeled and its response to an anisotropic multi-layer conductor simulated. The modeling results are then used to finalize specifications of the eddy current probe. Experimental testing of the fabricated probe is presented for several samples including a truncated pyramid part with complex fiber orientation draped to the geometry for resin transfer molding. The inductively coupled single sided measurement enables fiber orientation characterization through the thickness of the part. The fast and cost-effective technique can be applied as a spot check or as a surface map of the fiber orientations across the structure. This paper will detail the results of the probe design, computer simulations, and experimental results.

A guide to structural factors for advanced composites used on spacecraft

NASA Technical Reports Server (NTRS)

Vanwagenen, Robert

1989-01-01

The use of composite materials in spacecraft systems is constantly increasing. Although the areas of composite design and fabrication are maturing, they remain distinct from the same activities performed using conventional materials and processes. This has led to some confusion regarding the precise meaning of the term 'factor of safety' as it applies to these structures. In addition, composite engineering introduces terms such as 'knock-down factors' to further modify material properties for design purposes. This guide is intended to clarify these terms as well as their use in the design of composite structures for spacecraft. It is particularly intended to be used by the engineering community not involved in the day-to-day composites design process. An attempt is also made to explain the wide range of factors of safety encountered in composite designs as well as their relationship to the 1.4 factor of safety conventionally applied to metallic structures.

Carbon Displacement-Induced Single Carbon Atomic Chain Formation and its Effects on Sliding of SiC Fibers in SiC/graphene/SiC Composite

DOE PAGES

Wallace, Joseph B.; Chen, Di; Shao, Lin

2015-11-03

Understanding radiation effects on the mechanical properties of SiC composites is important to their application in advanced reactor designs. By means of molecular dynamics simulations, we found that due to strong interface bonding between the graphene layers and SiC, the sliding friction of SiC fibers is largely determined by the frictional behavior between graphene layers. Upon sliding, carbon displacements between graphene layers can act as seed atoms to induce the formation of single carbon atomic chains (SCACs) by pulling carbon atoms from the neighboring graphene planes. The formation, growth, and breaking of SCACs determine the frictional response to irradiation.

Nonlinear and Threshold Responses of Grassland Productivity and Species Composition to Increased CO2 Vary with Soil Type

NASA Astrophysics Data System (ADS)

Fay, P. A.; Jin, V.; Jackson, R. B.; Gill, R. A.; Way, D.; Polley, W.

2011-12-01

Climate change is likely to cause nonlinear responses in ecosystem function and threshold changes in species composition. Here we report aboveground net primary productivity (ANPP) responses to a continuous CO2 concentration gradient (250 to 500 μL L-1,) in experimental grassland communities on three soils differing in water holding capacity and other properties. Communities consisting of four C4 grasses, two C3 forbs, and one legume were established on a lowland clay (vertisol, n=32), an upland clay (mollisol, n=32), and an alluvial sand (alfisol, n=16). The communities were positioned in a stratified random design in the CO2 gradient for five growing seasons, and were irrigated to mimic the average growing season rainfall regime for the study site in Central Texas. ANPP increased with CO2 almost two-fold more on the upland clay and alluvial sand than on the lowland clay (p < 0.0001), because of strong linear responses to CO2 on these soils (R2 = 0.50 to 0.59, p < 0.002) compared to a saturating response to CO2 on the lowland clay (R2 = 0.48, p= 0.01). On the two more responsive soils, the mesic tallgrass Sorghastrum nutans replaced the more drought adapted mid-grass Bouteloua curtipendula at elevated CO2, while B. curtipendula largely replaced S. nutans at low CO2, especially on the upland clay. Evidence for a similar composition change was not found on the lowland clay. Thus, two soils displayed a threshold change in community composition that accounted for up to 57% of variation in ANPP for those soils. Variation in ANPP and species composition with CO2 were accompanied by linear increases in soil water content (SWC, 0 - 20 cm, volumetric), most strongly on the alluvial sand (R2 = 0.39, p < 0.009) and by weak decreases with CO2 in soil N. Structural equation models explained 34 to 52% of the variation in ANPP, and indicated that CO2 effects on ANPP on the upland clay were primarily explained by CO2 effects on species composition, and on the alluvial sand by CO2 effects on SWC. Responses to elevated CO2 in SWC, ANPP, and species composition were explained by reduced stomatal conductance and increased photosynthetic water use efficiency (WUE) in both grasses. In addition, S. nutans gained more in WUE at elevated CO2 than B. curtipendula, while B. curtipendula at elevated CO2 had lower light saturated photosynthetic capacity, quantum use efficiency, and dark respiration than S. nutans. Thus, at elevated CO2, shading by the taller S. nutans likely lowered B. curtipendula carbon assimilation and growth. We conclude that elevated CO2 strongly increased ANPP on upland clay and alluvial sand soils where there were also gains in soil moisture and threshold changes in species composition driven by physiological differences in the two dominant grass species. As a result, CO2 effects on ANPP will likely differ with soil type across the landscape.

Advanced composite aileron for L-1011 transport aircraft: Design and analysis

NASA Technical Reports Server (NTRS)

Griffin, C. F.; Fogg, L. D.; Dunning, E. G.

1981-01-01

Detail design of the composite aileron has been completed. The aileron design is a multi-rib configuration with single piece upper and lower covers mechanically fastened to the substructure. Covers, front, spar and ribs are fabricated with graphite/epoxy tape or fabric composite material. The design has a weight savings of 23 percent compared to the aluminum aileron. The composite aileron has 50 percent fewer fasteners and parts than the metal aileron and is predicted to be cost competitive. Structural integrity of the composite aileron was verified by structural analysis and an extensive test program. Static, failsafe, and vibration analyses have been conducted on the composite aileron using finite element models and specialized computer programs for composite material laminates. The fundamental behavior of the composite materials used in the aileron was determined by coupon tests for a variety of environmental conditions. Critical details of the design were interrogated by static and fatigue tests on full-scale subcomponents and subassemblies of the aileron.

Sparse feature selection methods identify unexpected global cellular response to strontium-containing materials

PubMed Central

Autefage, Hélène; Littmann, Elena; Hedegaard, Martin A. B.; Von Erlach, Thomas; O’Donnell, Matthew; Burden, Frank R.; Winkler, David A.; Stevens, Molly M.

2015-01-01

Despite the increasing sophistication of biomaterials design and functional characterization studies, little is known regarding cells’ global response to biomaterials. Here, we combined nontargeted holistic biological and physical science techniques to evaluate how simple strontium ion incorporation within the well-described biomaterial 45S5 bioactive glass (BG) influences the global response of human mesenchymal stem cells. Our objective analyses of whole gene-expression profiles, confirmed by standard molecular biology techniques, revealed that strontium-substituted BG up-regulated the isoprenoid pathway, suggesting an influence on both sterol metabolite synthesis and protein prenylation processes. This up-regulation was accompanied by increases in cellular and membrane cholesterol and lipid raft contents as determined by Raman spectroscopy mapping and total internal reflection fluorescence microscopy analyses and by an increase in cellular content of phosphorylated myosin II light chain. Our unexpected findings of this strong metabolic pathway regulation as a response to biomaterial composition highlight the benefits of discovery-driven nonreductionist approaches to gain a deeper understanding of global cell–material interactions and suggest alternative research routes for evaluating biomaterials to improve their design. PMID:25831522

Multiobjective Optimization of Atmospheric Plasma Spray Process Parameters to Deposit Yttria-Stabilized Zirconia Coatings Using Response Surface Methodology

NASA Astrophysics Data System (ADS)

Ramachandran, C. S.; Balasubramanian, V.; Ananthapadmanabhan, P. V.

2011-03-01

Atmospheric plasma spraying is used extensively to make Thermal Barrier Coatings of 7-8% yttria-stabilized zirconia powders. The main problem faced in the manufacture of yttria-stabilized zirconia coatings by the atmospheric plasma spraying process is the selection of the optimum combination of input variables for achieving the required qualities of coating. This problem can be solved by the development of empirical relationships between the process parameters (input power, primary gas flow rate, stand-off distance, powder feed rate, and carrier gas flow rate) and the coating quality characteristics (deposition efficiency, tensile bond strength, lap shear bond strength, porosity, and hardness) through effective and strategic planning and the execution of experiments by response surface methodology. This article highlights the use of response surface methodology by designing a five-factor five-level central composite rotatable design matrix with full replication for planning, conduction, execution, and development of empirical relationships. Further, response surface methodology was used for the selection of optimum process parameters to achieve desired quality of yttria-stabilized zirconia coating deposits.

Skylab

NASA Image and Video Library

1971-04-01

This photograph shows Skylab's Extreme Ultraviolet (XUV) Spectroheliograph during an acceptance test and checkout procedures in April 1971. The unit was an Apollo Telescope Mount (ATM) instrument designed to sequentially photograph the solar chromosphere and corona in selected ultraviolet wavelengths. The instrument also obtained information about composition, temperature, energy conversion and transfer, and plasma processes of the chromosphere and lower corona. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

Improving Ischemia Reperfusion Injury in Vascularized Composite Tissue Allotransplantation Via Histone Deacetylase Modulation

DTIC Science & Technology

2017-10-01

of the author(s) and should not be construed as an official Department of the Army position, policy or decision unless so designated by other...average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed...IRI) in scenarios relevant to limb transplantation using mouse models for experimentation. Limitations in tolerated ischemia times limits the scope

Central composite rotatable design for investigation of microwave-assisted extraction of okra pod hydrocolloid.

PubMed

Samavati, Vahid

2013-10-01

Microwave-assisted extraction (MAE) technique was employed to extract the hydrocolloid from okra pods (OPH). The optimal conditions for microwave-assisted extraction of OPH were determined by response surface methodology. A central composite rotatable design (CCRD) was applied to evaluate the effects of three independent variables (microwave power (X1: 100-500 W), extraction time (X2: 30-90 min), and extraction temperature (X3: 40-90 °C)) on the extraction yield of OPH. The correlation analysis of the mathematical-regression model indicated that quadratic polynomial model could be employed to optimize the microwave extraction of OPH. The optimal conditions to obtain the highest recovery of OPH (14.911±0.27%) were as follows: microwave power, 395.56 W; extraction time, 67.11 min and extraction temperature, 73.33 °C. Under these optimal conditions, the experimental values agreed with the predicted ones by analysis of variance. It indicated high fitness of the model used and the success of response surface methodology for optimizing OPH extraction. After method development, the DPPH radical scavenging activity of the OPH was evaluated. MAE showed obvious advantages in terms of high extraction efficiency and radical scavenging activity of extract within the shorter extraction time. Copyright © 2013 Elsevier B.V. All rights reserved.

Optimization of microbial detoxification for an aquatic mercury-contaminated environment.

PubMed

Figueiredo, Neusa L; Canário, João; Serralheiro, Maria Luísa; Carvalho, Cristina

2017-01-01

Mercury (Hg) reduction performed by microorganisms is well recognized as a biological means for remediation of contaminated environment. Recently, studies demonstrated that Hg-resistant microorganisms of Tagus Estuary are involved in metal reduction processes. In the present study, aerobic microbial community isolated from a highly Hg-contaminated area of Tagus Estuary was used to determine the optimization of the reduction process in conditions such as the contaminated ecosystem. Factorial design methodology was employed to examine the influence of glucose, sulfate, iron, and chloride on Hg reduction. In the presence of several concentrations of these elements, microbial community reduced Hg in a range of 37-61% of the initial 0.1 mg/ml Hg 2+ levels. The response prediction through central composite design showed that the increase of sulfate concentration led to an optimal response in Hg reduction by microbial community, while the rise in chloride levels markedly decreased metal reduction. Iron may exert antagonistic effects depending upon the media composition. These results are useful in understanding the persistence of Hg contamination in Tagus Estuary after inactivation of critical industrial units, as well as data might also be beneficial for development of new bioremediation strategies either in Tagus Estuary and/or in other Hg-contaminated aquatic environments.

Fuel flexibility via real-time Raman fuel-gas analysis for turbine system control

NASA Astrophysics Data System (ADS)

Buric, M.; Woodruff, S.; Chorpening, B.; Tucker, D.

2015-06-01

The modern energy production base in the U.S. is increasingly incorporating opportunity fuels such as biogas, coalbed methane, coal syngas, solar-derived hydrogen, and others. In many cases, suppliers operate turbine-based generation systems to efficiently utilize these diverse fuels. Unfortunately, turbine engines are difficult to control given the varying energy content of these fuels, combined with the need for a backup natural gas supply to provide continuous operation. Here, we study the use of a specially designed Raman Gas Analyzer based on capillary waveguide technology with sub-second response time for turbine control applications. The NETL Raman Gas Analyzer utilizes a low-power visible pump laser, and a capillary waveguide gas-cell to integrate large spontaneous Raman signals, and fast gas-transfer piping to facilitate quick measurements of fuel-gas components. A U.S. Department of Energy turbine facility known as HYPER (hybrid performance system) serves as a platform for apriori fuel composition measurements for turbine speed or power control. A fuel-dilution system is used to simulate a compositional upset while simultaneously measuring the resultant fuel composition and turbine response functions in real-time. The feasibility and efficacy of system control using the spontaneous Raman-based measurement system is then explored with the goal of illustrating the ability to control a turbine system using available fuel composition as an input process variable.

Enhanced active extracellular polysaccharide production from Ganoderma formosanum using computational modeling.

PubMed

Hsu, Kai-Di; Wu, Shu-Pei; Lin, Shin-Ping; Lum, Chi-Chin; Cheng, Kuan-Chen

2017-10-01

Extracellular polysaccharide (EPS) is one of the major bioactive ingredients contributing to the health benefits of Ganoderma spp. In this study, response surface methodology was applied to determine the optimal culture conditions for EPS production of Ganoderma formosanum. The optimum medium composition was found to be at initial pH 5.3, 49.2 g/L of glucose, and 4.9 g/L of yeast extract by implementing a three-factor-three-level Box-Behnken design. Under this condition, the predicted yield of EPS was up to 830.2 mg/L, which was 1.4-fold higher than the one from basic medium (604.5 mg/L). Furthermore, validating the experimental value of EPS production depicted a high correlation (100.4%) with the computational prediction response model. In addition, the percentage of β-glucan, a well-recognized bioactive polysaccharide, in EPS was 53±5.5%, which was higher than that from Ganoderma lucidum in a previous study. Moreover, results of monosaccharide composition analysis indicated that glucose was the major component of G. formosanum EPS, supporting a high β-glucan percentage in EPS. Taken together, this is the first study to investigate the influence of medium composition for G. formosanum EPS production as well as its β-glucan composition. Copyright © 2017. Published by Elsevier B.V.

Subscale Test Methods for Combustion Devices

NASA Technical Reports Server (NTRS)

Anderson, W. E.; Sisco, J. C.; Long, M. R.; Sung, I.-K.

2005-01-01

Stated goals for long-life LRE s have been between 100 and 500 cycles: 1) Inherent technical difficulty of accurately defining the transient and steady state thermochemical environments and structural response (strain); 2) Limited statistical basis on failure mechanisms and effects of design and operational variability; and 3) Very high test costs and budget-driven need to protect test hardware (aversion to test-to-failure). Ambitious goals will require development of new databases: a) Advanced materials, e.g., tailored composites with virtually unlimited property variations; b) Innovative functional designs to exploit full capabilities of advanced materials; and c) Different cycles/operations. Subscale testing is one way to address technical and budget challenges: 1) Prototype subscale combustors exposed to controlled simulated conditions; 2) Complementary to conventional laboratory specimen database development; 3) Instrumented with sensors to measure thermostructural response; and 4) Coupled with analysis

A statistical experiment design approach for optimizing biodegradation of weathered crude oil in coastal sediments.

PubMed

Mohajeri, Leila; Aziz, Hamidi Abdul; Isa, Mohamed Hasnain; Zahed, Mohammad Ali

2010-02-01

This work studied the bioremediation of weathered crude oil (WCO) in coastal sediment samples using central composite face centered design (CCFD) under response surface methodology (RSM). Initial oil concentration, biomass, nitrogen and phosphorus concentrations were used as independent variables (factors) and oil removal as dependent variable (response) in a 60 days trial. A statistically significant model for WCO removal was obtained. The coefficient of determination (R(2)=0.9732) and probability value (P<0.0001) demonstrated significance for the regression model. Numerical optimization based on desirability function were carried out for initial oil concentration of 2, 16 and 30 g per kg sediment and 83.13, 78.06 and 69.92 per cent removal were observed respectively, compare to 77.13, 74.17 and 69.87 per cent removal for un-optimized results.

Assessment of coagulation pretreatment of leachate by response surface methodology.

PubMed

Lessoued, Ridha; Souahi, Fatiha; Castrillon Pelaez, Leonor

2017-11-01

Coagulation-flocculation is a relatively simple technique that can be used successfully for the treatment of old leachate by poly-aluminum chloride (PAC). The main objectives of this study are to design the experiments, build models and optimize the operating parameters, dosage m and pH, using the central composite design and response surface method. Developed for chemical organic matter (COD) and turbidity responses, the quadratic polynomial model is suitable for prediction within the range of simulated variables as it showed that the optimum conditions were m of 5.55 g/L at pH 7.05, with a determination coefficient R² at 99.33%, 99.92% and adjusted R² at 98.85% and 99.86% for both COD and turbidity. We confirm that the initial pH and PAC dosage have significant effects on COD and turbidity removal. The experimental data and model predictions agreed well and the removal efficiency of COD, turbidity, Fe, Pb and Cu reached respectively 61%, 96.4%, 97.1%, 99% and 100%.

A response surface methodology based damage identification technique

NASA Astrophysics Data System (ADS)

Fang, S. E.; Perera, R.

2009-06-01

Response surface methodology (RSM) is a combination of statistical and mathematical techniques to represent the relationship between the inputs and outputs of a physical system by explicit functions. This methodology has been widely employed in many applications such as design optimization, response prediction and model validation. But so far the literature related to its application in structural damage identification (SDI) is scarce. Therefore this study attempts to present a systematic SDI procedure comprising four sequential steps of feature selection, parameter screening, primary response surface (RS) modeling and updating, and reference-state RS modeling with SDI realization using the factorial design (FD) and the central composite design (CCD). The last two steps imply the implementation of inverse problems by model updating in which the RS models substitute the FE models. The proposed method was verified against a numerical beam, a tested reinforced concrete (RC) frame and an experimental full-scale bridge with the modal frequency being the output responses. It was found that the proposed RSM-based method performs well in predicting the damage of both numerical and experimental structures having single and multiple damage scenarios. The screening capacity of the FD can provide quantitative estimation of the significance levels of updating parameters. Meanwhile, the second-order polynomial model established by the CCD provides adequate accuracy in expressing the dynamic behavior of a physical system.

Use of response surface methodology to study the effect of media composition on aflatoxin production by Aspergillus flavus.

PubMed

Ahmad, Mahboob; Ahmad, Malik M; Hamid, Rifat; Abdin, M Z; Javed, Saleem

2013-02-01

Aflatoxins are one of the most important secondary metabolites. These extrolites are produced by a number of Aspergillus fungi. In this study, we demonstrate the effect of media components and enhanced aflatoxin yield shown by A. flavus using response surface methodology in response to different nutrients. Different components of a chemically defined media that influence the aflatoxin production were monitored using Plackett-Burman experimental design and further optimized by Box-Behnken factorial design of response surface methodology in liquid culture. Interactions were studied with five variables, namely sorbitol, fructose, ammonium sulfate, KH(2)PO(4), and MgSO(4).7H(2)O. Maximum aflatoxin production was envisaged in medium containing 4.94 g/l sorbitol, 5.56 g/l fructose, 0.62 g/l ammonium sulfate, 1.33 g/l KH(2)PO(4), and 0.65 g/l MgSO(4)·7H(2)O using response surface plots and the point prediction tool of the DESIGN EXPERT 8.1.0 (Stat-Ease, USA) software. However, a production of 5.25 μg/ml aflatoxin production was obtained, which was in agreement with the prediction observed in verification experiment. The other component (MgSO(4).7H(2)O) was found to be an insignificant variable.

Sonic Fatigue Design Techniques for Advanced Composite Aircraft Structures

DTIC Science & Technology

1980-04-01

AFWAL-TR-80.3019 AD A 090553 SONIC FATIGUE DESIGN TECHNIQUES FOR ADVANCED COMPOSITE AIRCRAFT STRUCTURES FINAL REPORT Ian Holehouse Rohr Industries...5 2. General Sonic Fatigue Theory .... ....... 7 3. Composite Laminate Analysis .. ....... ... 10 4. Preliminary Sonic Fatigue...overall sonic fatigue design guides. These existing desiyn methcds have been developed for metal structures. However, recent advanced composite

Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades

NASA Technical Reports Server (NTRS)

Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas

2012-01-01

Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

NASA Technical Reports Server (NTRS)

Abumeri, Galib H.; Chamis, Christos C.

2003-01-01

The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

Polymeric behavior evaluation of PVP K30-poloxamer binary carrier for solid dispersed nisoldipine by experimental design.

PubMed

Kyaw Oo, May; Mandal, Uttam K; Chatterjee, Bappaditya

2017-02-01

High melting point polymeric carrier without plasticizer is unacceptable for solid dispersion (SD) by melting method. Combined polymer-plasticizer carrier significantly affects drug solubility and tableting property of SD. To evaluate and optimize the combined effect of a binary carrier consisting PVP K30 and poloxamer 188, on nisoldipine solubility and tensile strength of amorphous SD compact (SD compact ) by experimental design. SD of nisoldpine (SD nisol ) was prepared by melt mixing with different PVP K30 and poloxamer amount. A 3 2 factorial design was employed using nisoldipine solubility and tensile strength of SD compact as response variables. Statistical optimization by design expert software, and SD nisol characterization using ATR FTIR, DSC and microscopy were done. PVP K30:poloxamer, at a ratio of 3.73:6.63, was selected as the optimized combination of binary polymeric carrier resulting nisoldipine solubility of 115 μg/mL and tensile strength of 1.19 N/m 2 . PVP K30 had significant positive effect on both responses. Increase in poloxamer concentration after a certain level decreased nisoldipine solubility and tensile strength of SD compact . An optimized PVP K30-poloxamer binary composition for SD carrier was developed. Tensile strength of SD compact can be considered as a response for experimental design to optimize SD.

Composite chronicles: A study of the lessons learned in the development, production, and service of composite structures

NASA Technical Reports Server (NTRS)

Vosteen, Louis F.; Hadcock, Richard N.

1994-01-01

A study of past composite aircraft structures programs was conducted to determine the lessons learned during the programs. The study focused on finding major underlying principles and practices that experience showed have significant effects on the development process and should be recognized and understood by those responsible for using of composites. Published information on programs was reviewed and interviews were conducted with personnel associated with current and past major development programs. In all, interviews were conducted with about 56 people representing 32 organizations. Most of the people interviewed have been involved in the engineering and manufacturing development of composites for the past 20 to 25 years. Although composites technology has made great advances over the past 30 years, the effective application of composites to aircraft is still a complex problem that requires experienced personnel with special knowledge. All disciplines involved in the development process must work together in real time to minimize risk and assure total product quality and performance at acceptable costs. The most successful programs have made effective use of integrated, collocated, concurrent engineering teams, and most often used well-planned, systematic development efforts wherein the design and manufacturing processes are validated in a step-by-step or 'building block' approach. Such approaches reduce program risk and are cost effective.

Optimized Non-Obstructive Particle Damping (NOPD) Treatment for Composite Honeycomb Structures

NASA Technical Reports Server (NTRS)

Panossian, H.

2008-01-01

Non-Obstructive Particle Damping (NOPD) technology is a passive vibration damping approach whereby metallic or non-metallic particles in spherical or irregular shapes, of heavy or light consistency, and even liquid particles are placed inside cavities or attached to structures by an appropriate means at strategic locations, to absorb vibration energy. The objective of the work described herein is the development of a design optimization procedure and discussion of test results for such a NOPD treatment on honeycomb (HC) composite structures, based on finite element modeling (FEM) analyses, optimization and tests. Modeling and predictions were performed and tests were carried out to correlate the test data with the FEM. The optimization procedure consisted of defining a global objective function, using finite difference methods, to determine the optimal values of the design variables through quadratic linear programming. The optimization process was carried out by targeting the highest dynamic displacements of several vibration modes of the structure and finding an optimal treatment configuration that will minimize them. An optimal design was thus derived and laboratory tests were conducted to evaluate its performance under different vibration environments. Three honeycomb composite beams, with Nomex core and aluminum face sheets, empty (untreated), uniformly treated with NOPD, and optimally treated with NOPD, according to the analytically predicted optimal design configuration, were tested in the laboratory. It is shown that the beam with optimal treatment has the lowest response amplitude. Described below are results of modal vibration tests and FEM analyses from predictions of the modal characteristics of honeycomb beams under zero, 50% uniform treatment and an optimal NOPD treatment design configuration and verification with test data.

Exploratory Factor Analyses of the CAHPS® Hospital Pilot Survey Responses across and within Medical, Surgical, and Obstetric Services

PubMed Central

O'Malley, A James; Zaslavsky, Alan M; Hays, Ron D; Hepner, Kimberly A; Keller, San; Cleary, Paul D

2005-01-01

Objectives To estimate the associations among hospital-level scores from the Consumer Assessments of Healthcare Providers and Systems (CAHPS®) Hospital pilot survey within and across different services (surgery, obstetrics, medical), and to evaluate differences between hospital- and patient-level analyses. Data Source CAHPS Hospital pilot survey data provided by the Centers for Medicare and Medicaid Services. Study Design Responses to 33 questionnaire items were analyzed using patient- and hospital-level exploratory factor analytic (EFA) methods to identify both a patient-level and hospital-level composite structures for the CAHPS Hospital survey. The latter EFA was corrected for patient-level sampling variability using a hierarchical model. We compared results of these analyses with each other and to separate EFAs conducted at the service level. To quantify the similarity of assessments across services, we compared correlations of different composites within the same service with those of the same composite across different services. Data Collection Cross-sectional data were collected during the summer of 2003 via mail and telephone from 19,720 patients discharged from November 2002 through January 2003 from 132 hospitals in three states. Principal Findings Six factors provided the best description of inter-item covariation at the patient level. Analyses that assessed variability across both services and hospitals suggested that three dimensions provide a parsimonious summary of inter-item covariation at the hospital level. Hospital-level factor structures also differed across services; as much variation in quality reports was explained by service as by composite. Conclusions Variability of CAHPS scores across hospitals can be reported parsimoniously using a limited number of composites. There is at least as much distinct information in composite scores from different services as in different composite scores within each service. Because items cluster slightly differently in the different services, service-specific composites may be more informative when comparing patients in a given service across hospitals. When studying individual-level variability, a more differentiated structure is probably more appropriate. PMID:16316439

Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites

PubMed Central

Khanolkar, Gauri R.; Rauls, Michael B.; Kelly, James P.; Graeve, Olivia A.; Hodge, Andrea M.; Eliasson, Veronica

2016-01-01

The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding. PMID:26932846

Shock Wave Response of Iron-based In Situ Metallic Glass Matrix Composites.

PubMed

Khanolkar, Gauri R; Rauls, Michael B; Kelly, James P; Graeve, Olivia A; Hodge, Andrea M; Eliasson, Veronica

2016-03-02

The response of amorphous steels to shock wave compression has been explored for the first time. Further, the effect of partial devitrification on the shock response of bulk metallic glasses is examined by conducting experiments on two iron-based in situ metallic glass matrix composites, containing varying amounts of crystalline precipitates, both with initial composition Fe49.7Cr17.7Mn1.9Mo7.4W1.6B15.2C3.8Si2.4. The samples, designated SAM2X5-600 and SAM2X5-630, are X-ray amorphous and partially crystalline, respectively, due to differences in sintering parameters during sample preparation. Shock response is determined by making velocity measurements using interferometry techniques at the rear free surface of the samples, which have been subjected to impact from a high-velocity projectile launched from a powder gun. Experiments have yielded results indicating a Hugoniot Elastic Limit (HEL) to be 8.58 ± 0.53 GPa for SAM2X5-600 and 11.76 ± 1.26 GPa for SAM2X5-630. The latter HEL result is higher than elastic limits for any BMG reported in the literature thus far. SAM2X5-600 catastrophically loses post-yield strength whereas SAM2X5-630, while showing some strain-softening, retains strength beyond the HEL. The presence of crystallinity within the amorphous matrix is thus seen to significantly aid in strengthening the material as well as preserving material strength beyond yielding.

A systematic composite service design modeling method using graph-based theory.

PubMed

Elhag, Arafat Abdulgader Mohammed; Mohamad, Radziah; Aziz, Muhammad Waqar; Zeshan, Furkh

2015-01-01

The composite service design modeling is an essential process of the service-oriented software development life cycle, where the candidate services, composite services, operations and their dependencies are required to be identified and specified before their design. However, a systematic service-oriented design modeling method for composite services is still in its infancy as most of the existing approaches provide the modeling of atomic services only. For these reasons, a new method (ComSDM) is proposed in this work for modeling the concept of service-oriented design to increase the reusability and decrease the complexity of system while keeping the service composition considerations in mind. Furthermore, the ComSDM method provides the mathematical representation of the components of service-oriented design using the graph-based theoryto facilitate the design quality measurement. To demonstrate that the ComSDM method is also suitable for composite service design modeling of distributed embedded real-time systems along with enterprise software development, it is implemented in the case study of a smart home. The results of the case study not only check the applicability of ComSDM, but can also be used to validate the complexity and reusability of ComSDM. This also guides the future research towards the design quality measurement such as using the ComSDM method to measure the quality of composite service design in service-oriented software system.

A Systematic Composite Service Design Modeling Method Using Graph-Based Theory

PubMed Central

Elhag, Arafat Abdulgader Mohammed; Mohamad, Radziah; Aziz, Muhammad Waqar; Zeshan, Furkh

2015-01-01

The composite service design modeling is an essential process of the service-oriented software development life cycle, where the candidate services, composite services, operations and their dependencies are required to be identified and specified before their design. However, a systematic service-oriented design modeling method for composite services is still in its infancy as most of the existing approaches provide the modeling of atomic services only. For these reasons, a new method (ComSDM) is proposed in this work for modeling the concept of service-oriented design to increase the reusability and decrease the complexity of system while keeping the service composition considerations in mind. Furthermore, the ComSDM method provides the mathematical representation of the components of service-oriented design using the graph-based theoryto facilitate the design quality measurement. To demonstrate that the ComSDM method is also suitable for composite service design modeling of distributed embedded real-time systems along with enterprise software development, it is implemented in the case study of a smart home. The results of the case study not only check the applicability of ComSDM, but can also be used to validate the complexity and reusability of ComSDM. This also guides the future research towards the design quality measurement such as using the ComSDM method to measure the quality of composite service design in service-oriented software system. PMID:25928358

Design considerations for composite fuselage structure of commercial transport aircraft

NASA Technical Reports Server (NTRS)

Davis, G. W.; Sakata, I. F.

1981-01-01

The structural, manufacturing, and service and environmental considerations that could impact the design of composite fuselage structure for commercial transport aircraft application were explored. The severity of these considerations was assessed and the principal design drivers delineated. Technical issues and potential problem areas which must be resolved before sufficient confidence is established to commit to composite materials were defined. The key issues considered are: definition of composite fuselage design specifications, damage tolerance, and crashworthiness.

Optimization of process condition for the preparation of amine-impregnated activated carbon developed for CO2 capture and applied to methylene blue adsorption by response surface methodology.

PubMed

Das, Dipa; Meikap, Bhim C

2017-10-15

The present research describes the optimal adsorption condition for methylene blue (MB). The adsorbent used here was monoethanol amine-impregnated activated carbon (MEA-AC) prepared from green coconut shell. Response surface methodology (RSM) is the multivariate statistical technique used for the optimization of the process variables. The central composite design is used to determine the effect of activation temperature, activation time and impregnation ratio on the MB removal. The percentage (%) MB adsorption by MEA-AC is evaluated as a response of the system. A quadratic model was developed for response. From the analysis of variance, the factor which was the most influential on the experimental design response has been identified. The optimum condition for the preparation of MEA-AC from green coconut shells is the temperature of activation 545.6°C, activation time of 41.64 min and impregnation ratio of 0.33 to achieve the maximum removal efficiency of 98.21%. At the same optimum parameter, the % MB removal from the textile-effluent industry was examined and found to be 96.44%.

Co-dispersion of plasmonic nanorods in thermotropic nematic liquid crystals

NASA Astrophysics Data System (ADS)

Sheetah, Ghadah; Liu, Qinkun; Smalukh, Ivan

Colloidal dispersions of plasmonic metal nanoparticles in liquid crystals promise the capability of pre-engineering tunable optical properties of mesostructured metal-dielectric composites. Recently, concentrated dispersions of anisotropic gold, silver, and metal alloy nanoparticles in nematic hosts have been achieved and successfully controlled by low-voltage fields. However, to enable versatile designs of material behavior of the composites, simultaneous co-dispersion of anisotropic particles with different shapes, alignment properties, and compositions are often needed. We achieve such co-dispersions and explore their switching characteristics in response to external stimuli like light and electric fields. We demonstrated that spectral characteristics of co-dispersions of multiple types of anisotropic nanoparticles in a common nematic host provides unprecedented variety of electrically- and optically-tunable material behavior, with a host of potential practical applications in electro-optic devices and displays Ghadah acknowledges support from the King Faisal University (KFU) graduate fellowship.

Structural mechanics and helical geometry of thin elastic composites.

PubMed

Wada, Hirofumi

2016-09-21

Helices are ubiquitous in nature, and helical shape transition is often observed in residually stressed bodies, such as composites, wherein materials with different mechanical properties are glued firmly together to form a whole body. Inspired by a variety of biological examples, the basic physical mechanism responsible for the emergence of twisting and bending in such thin composite structures has been extensively studied. Here, we propose a simplified analytical model wherein a slender membrane tube undergoes a helical transition driven by the contraction of an elastic ribbon bound to the membrane surface. We analytically predict the curvature and twist of an emergent helix as functions of differential strains and elastic moduli, which are confirmed by our numerical simulations. Our results may help understand shapes observed in different biological systems, such as spiral bacteria, and could be applied to novel designs of soft machines and robots.

Sharp Refractory Composite Leading Edges on Hypersonic Vehicles

NASA Technical Reports Server (NTRS)

Walker, Sandra P.; Sullivan, Brian J.

2003-01-01

On-going research of advanced sharp refractory composite leading edges for use on hypersonic air-breathing vehicles is presented in this paper. Intense magnitudes of heating and of heating gradients on the leading edge lead to thermal stresses that challenge the survivability of current material systems. A fundamental understanding of the problem is needed to further design development. Methodology for furthering the technology along with the use of advanced fiber architectures to improve the thermal-structural response is explored in the current work. Thermal and structural finite element analyses are conducted for several advanced fiber architectures of interest. A tailored thermal shock parameter for sharp orthotropic leading edges is identified for evaluating composite material systems. The use of the tailored thermal shock parameter has the potential to eliminate the need for detailed thermal-structural finite element analyses for initial screening of material systems being considered for a leading edge component.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Huidong; Deng, Zhiqun; Carlson, Thomas J.

Piezoelectric materials have been used in underwater acoustic transducers for nearly a century. In this paper, we reviewed four different types of piezoelectric materials: piezoelectric ceramics, single crystals, composites, and polymers, which are widely used in underwater acoustic transducers nowadays. Piezoelectric ceramics are the most dominant material type and are used as a single-phase material or one of the end members in composites. Piezoelectric single crystals offer outstanding electromechanical response but are limited by their manufacturing cost. Piezoelectric polymers provide excellent acoustic impedance matching and transducer fabrication flexibility although their piezoelectric properties are not as good as ceramics and singlemore » crystals. Composites combined the merits of ceramics and polymers and are receiving increased attention. The typical structure and electromechanical properties of each type of materials are introduced and discussed with respect to underwater acoustic transducer applications. Their advantages and disadvantages are summarized. Some of the critical design considerations when developing underwater acoustic transducers with these materials are also touched upon.« less

ACEE Composite Structures Technology: Review of selected NASA research on composite materials and structures

NASA Technical Reports Server (NTRS)

1984-01-01

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program was designed to develop technology for advanced composites in commercial aircraft. Research on composite materials, aircraft structures, and aircraft design is presented herein. The following parameters of composite materials were addressed: residual strength, damage tolerance, toughness, tensile strength, impact resistance, buckling, and noise transmission within composite materials structures.

The rational designed graphene oxide-Fe2O3 composites with low cytotoxicity.

PubMed

Yan, Dong; Zhao, Haiyan; Pei, Jiayun; Wu, Xin; Liu, Yue

2017-03-01

Novel two-dimensional materials with a layered structure are of special interest for a variety of promising applications. In current research, the nanostructured graphene oxide-Fe 2 O 3 composite (GO-Fe 2 O 3 ) was firstly obtained via a carefully elaborated approach of vacuum freeze-drying. The scanning electron microscopy (SEM) and transmission electron microscope (TEM) images revealed that α-Fe 2 O 3 nanoparticles loaded well on the surfaces of graphene. A series of characterization were performed to further elucidate the as-obtained nanomaterial's physicochemical properties. These results suggested the current route could be further extended to obtain the other kinds of two-dimensional materials based composites. For the sake of extending the potential application of herein achieved graphene composites, its cytotoxicity assessment on HeLa cells was systematically investigated. CCK-8 assay in HeLa cells treated by GO-Fe 2 O 3 showed dose- (1-100μg/ml) and time- (24-48h) dependent cytotoxicity, which was comparable to that of GO. The excess generation of intracellular reactive oxygen species (ROS) induced by these nanomaterials was responsible for the cytotoxicity. TEM analysis vividly illustrated GO-Fe 2 O 3 internalized by HeLa cells in endomembrane compartments such as lysosomes, and degraded through autophagic pathway. The detrimental biological consequence accompanied by cell internalization was limited. Based on the above results, it expected to render useful information for the development of new and popular strategies to design graphene-based composites, as well as deep insights into the mechanism of graphene-based composites cytotoxicity for further potential application. Copyright © 2016 Elsevier B.V. All rights reserved.

Calorie Restriction in Overweight SeniorS: Response of Older Adults to a Dieting Study: The CROSSROADS Randomized Controlled Clinical Trial

PubMed Central

Haas, Marilyn C.; Bodner, Eric V.; Brown, Cynthia J.; Bryan, David; Buys, David R.; Keita, Akilah Dulin; Flagg, Lee Anne; Goss, Amy; Gower, Barbara; Hovater, Martha; Hunter, Gary; Ritchie, Christine S.; Roth, David L.; Wingo, Brooks C.; Ard, Jamy; Locher, Julie L.

2014-01-01

We conducted a study designed to evaluate whether the benefits of intentional weight loss exceed the potential risks in a group of community-dwelling, obese, older adults who were at increased risk for cardiometabolic disease. The CROSSROADS trial used a prospective randomized controlled design to compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition and adipose tissue deposition (Specific Aim #1: To compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition, namely visceral adipose tissue (VAT)), cardiometabolic disease risk (Specific Aim #2: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on cardiometabolic disease risk), functional status and quality of life (Specific Aim #3: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on functional status and quality of life). Participants were randomly assigned to one of three groups: Exercise Only (Control) Intervention, Exercise + Diet Quality + Weight Maintenance Intervention, or Exercise + Diet Quality + Weight Loss Intervention. CROSSROADS utilized a lifestyle intervention approach consisting of exercise, dietary, and behavioral components. The development and implementation of the CROSSROADS protocol, including a description of the methodology, detailing specific elements of the lifestyle intervention, assurances of treatment fidelity, and participant retention; outcome measures and adverse event monitoring; as well as unique data management features of the trial results, are presented in this article. PMID:25424512

Calorie restriction in overweight seniors: response of older adults to a dieting study: the CROSSROADS randomized controlled clinical trial.

PubMed

Haas, Marilyn C; Bodner, Eric V; Brown, Cynthia J; Bryan, David; Buys, David R; Keita, Akilah Dulin; Flagg, Lee Anne; Goss, Amy; Gower, Barbara; Hovater, Martha; Hunter, Gary; Ritchie, Christine S; Roth, David L; Wingo, Brooks C; Ard, Jamy; Locher, Julie L

2014-01-01

We conducted a study designed to evaluate whether the benefits of intentional weight loss exceed the potential risks in a group of community-dwelling obese older adults who were at increased risk for cardiometabolic disease. The CROSSROADS trial used a prospective randomized controlled design to compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition and adipose tissue deposition (Specific Aim #1: To compare the effects of changes in diet composition alone or combined with weight loss with an exercise only control intervention on body composition, namely visceral adipose tissue), cardiometabolic disease risk (Specific Aim #2: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on cardiometabolic disease risk), and functional status and quality of life (Specific Aim #3: To compare the effects of a change in diet composition alone or combined with weight loss with an exercise only control intervention on functional status and quality of life). Participants were randomly assigned to one of three groups: Exercise Only (Control) Intervention, Exercise + Diet Quality + Weight Maintenance Intervention, or Exercise + Diet Quality + Weight Loss Intervention. CROSSROADS utilized a lifestyle intervention approach consisting of exercise, dietary, and behavioral components. The development and implementation of the CROSSROADS protocol, including a description of the methodology, detailing specific elements of the lifestyle intervention, assurances of treatment fidelity, and participant retention; outcome measures and adverse event monitoring; as well as unique data management features of the trial results, are presented in this article.

Applying Central Composite Design and Response Surface Methodology to Optimize Growth and Biomass Production of Haemophilus influenzae Type b.

PubMed

Momen, Seyed Bahman; Siadat, Seyed Davar; Akbari, Neda; Ranjbar, Bijan; Khajeh, Khosro

2016-06-01

Haemophilus influenzae type b (Hib) is the leading cause of bacterial meningitis, otitis media, pneumonia, cellulitis, bacteremia, and septic arthritis in infants and young children. The Hib capsule contains the major virulence factor, and is composed of polyribosyl ribitol phosphate (PRP) that can induce immune system response. Vaccines consisting of Hib capsular polysaccharide (PRP) conjugated to a carrier protein are effective in the prevention of the infections. However, due to costly processes in PRP production, these vaccines are too expensive. To enhance biomass, in this research we focused on optimizing Hib growth with respect to physical factors such as pH, temperature, and agitation by using a response surface methodology (RSM). We employed a central composite design (CCD) and a response surface methodology to determine the optimum cultivation conditions for growth and biomass production of H. influenzae type b. The treatment factors investigated were initial pH, agitation, and temperature, using shaking flasks. After Hib cultivation and determination of dry biomass, analysis of experimental data was performed by the RSM-CCD. The model showed that temperature and pH had an interactive effect on Hib biomass production. The dry biomass produced in shaking flasks was about 5470 mg/L, which was under an initial pH of 8.5, at 250 rpm and 35° C. We found CCD and RSM very effective in optimizing Hib culture conditions, and Hib biomass production was greatly influenced by pH and incubation temperature. Therefore, optimization of the growth factors to maximize Hib production can lead to 1) an increase in bacterial biomass and PRP productions, 2) lower vaccine prices, 3) vaccination of more susceptible populations, and 4) lower risk of Hib infections.

Biomimetic staggered composites with highly enhanced energy dissipation: Modeling, 3D printing, and testing

NASA Astrophysics Data System (ADS)

Zhang, Pu; Heyne, Mary A.; To, Albert C.

2015-10-01

We investigate the damping enhancement in a class of biomimetic staggered composites via a combination of design, modeling, and experiment. In total, three kinds of staggered composites are designed by mimicking the structure of bone and nacre. These composite designs are realized by 3D printing a rigid plastic and a viscous elastomer simultaneously. Greatly-enhanced energy dissipation in the designed composites is observed from both the experimental results and theoretical prediction. The designed polymer composites have loss modulus up to ~500 MPa, higher than most of the existing polymers. In addition, their specific loss modulus (up to 0.43 km2/s2) is among the highest of damping materials. The damping enhancement is attributed to the large shear deformation of the viscous soft matrix and the large strengthening effect from the rigid inclusion phase.

Formulation optimization of gentamicin loaded Eudragit RS100 microspheres using factorial design study.

PubMed

Singh, Deependra; Saraf, Swarnlata; Dixit, Vinod Kumar; Saraf, Shailendra

2008-04-01

Gentamicin-Eudragit RS100 microspheres were prepared by modified double emulsion method. A 3(2) full factorial experiment was designed to study the effects of the composition of outer aqueous phase in terms of amount of glycerol (viscosity effect) and sodium chloride (osmotic pressure gradient effect) on the entrapment efficiency and % yield and microsphere size. The results of analysis of variance test for responses measured indicated that the test is significant (p>0.05). The contribution of sodium chloride concentration was found to be higher on entrapment efficiency and % yield, whereas glycerol produced significant effect on the mean diameter of microspheres. Microspheres demonstrated spherical particles in the size range of 33.24-60.43 microm. In vitro release profile of optimized formulation demonstrated sustained release for 24 h following Higuchi kinetics. Finally, drug bioactivity was found to remain intact after microencapsulation. Response surface graphs are presented to examine the effects of independent variables on the responses studied. Thus, by formulation design important parameters affecting formulation characteristics of gentamicin loaded Eudragit RS100 microspheres can be identified for controlled delivery with desirable characters in terms of maximum entrapment and yield.

Characterization of Femoral Component Initial Stability and Cortical Strain in a Reduced Stem-Length Design.

PubMed

Small, Scott R; Hensley, Sarah E; Cook, Paige L; Stevens, Rebecca A; Rogge, Renee D; Meding, John B; Berend, Michael E

2017-02-01

Short-stemmed femoral components facilitate reduced exposure surgical techniques while preserving native bone. A clinically successful stem should ideally reduce risk for stress shielding while maintaining adequate primary stability for biological fixation. We asked (1) how stem-length changes cortical strain distribution in the proximal femur in a fit-and-fill geometry and (2) if short-stemmed components exhibit primary stability on par with clinically successful designs. Cortical strain was assessed via digital image correlation in composite femurs implanted with long, medium, and short metaphyseal fit-and-fill stem designs in a single-leg stance loading model. Strain was compared to a loaded, unimplanted femur. Bone-implant micromotion was then compared with reduced lateral shoulder short stem and short tapered-wedge designs in cyclic axial and torsional testing. Femurs implanted with short-stemmed components exhibited cortical strain response most closely matching that of the intact femur model, theoretically reducing the potential for proximal stress shielding. In micromotion testing, no difference in primary stability was observed as a function of reduced stem length within the same component design. Our findings demonstrate that within this fit-and-fill stem design, reduction in stem length improved proximal cortical strain distribution and maintained axial and torsional stability on par with other stem designs in a composite femur model. Short-stemmed implants may accommodate less invasive surgical techniques while facilitating more physiological femoral loading without sacrificing primary implant stability. Copyright © 2016 Elsevier Inc. All rights reserved.