Linguistic and Cognitive Characteristics of the Composition of the Text of J. K. Rowling's English Tales

ERIC Educational Resources Information Center

Solodova, Elena

2015-01-01

This article focuses on linguistic and cognitive characteristics inherent in the composition of the English postmodern tales written by J.K. Rowling. The composition of the text is viewed as linguistic and cognitive construal that integrates compositional plot structure, compositional meaning structure, linguistic and stylistic means of their…

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

Integrated Composite Stiffener Structure (ICoSS) Concept for Planetary Entry Vehicles

NASA Technical Reports Server (NTRS)

Kellas, Sotiris

2016-01-01

Results from the design, manufacturing, and testing of a lightweight Integrated Composite Stiffened Structure (ICoSS) concept, intended for multi-mission planetary entry vehicles are presented. Tests from both component and full-scale tests for a typical Earth Entry Vehicle forward shell manufactured using the ICoSS concept are presented and advantages of the concept for the particular application of passive Earth Entry Vehicles over other structural concepts are discussed.

Integration of fluidic jet actuators in composite structures

NASA Astrophysics Data System (ADS)

Schueller, Martin; Lipowski, Mathias; Schirmer, Eckart; Walther, Marco; Otto, Thomas; Geßner, Thomas; Kroll, Lothar

2015-04-01

Fluidic Actuated Flow Control (FAFC) has been introduced as a technology that influences the boundary layer by actively blowing air through slots or holes in the aircraft skin or wind turbine rotor blade. Modern wing structures are or will be manufactured using composite materials. In these state of the art systems, AFC actuators are integrated in a hybrid approach. The new idea is to directly integrate the active fluidic elements (such as SJAs and PJAs) and their components in the structure of the airfoil. Consequently, the integration of such fluidic devices must fit the manufacturing process and the material properties of the composite structure. The challenge is to integrate temperature-sensitive active elements and to realize fluidic cavities at the same time. The transducer elements will be provided for the manufacturing steps using roll-to-roll processes. The fluidic parts of the actuators will be manufactured using the MuCell® process that provides on the one hand the defined reproduction of the fluidic structures and, on the other hand, a high light weight index. Based on the first design concept, a demonstrator was developed in order to proof the design approach. The output velocity on the exit was measured using a hot-wire anemometer.

Predicting Structural Behavior of Filament Wound Composite Pressure Vessel Using Three Dimensional Shell Analysis

NASA Astrophysics Data System (ADS)

Madhavi, M.; Venkat, R.

2014-01-01

Fiber reinforced polymer composite materials with their higher specific strength, moduli and tailorability characteristics will result in reduction of weight of the structure. The composite pressure vessels with integrated end domes develop hoop stresses that are twice longitudinal stresses and when isotropic materials like metals are used for development of the hardware and the material is not fully utilized in the longitudinal/meridional direction resulting in over weight components. The determination of a proper winding angles and thickness is very important to decrease manufacturing difficulties and to increase structural efficiency. In the present study a methodology is developed to understand structural characteristics of filament wound pressure vessels with integrated end domes. Progressive ply wise failure analysis of composite pressure vessel with geodesic end domes is carried out to determine matrix crack failure, burst pressure values at various positions of the shell. A three dimensional finite element analysis is computed to predict the deformations and stresses in the composite pressure vessel. The proposed method could save the time to design filament wound structures, to check whether the ply design is safe for the given input conditions and also can be adapted to non-geodesic structures. The results can be utilized to understand structural characteristics of filament wound pressure vessels with integrated end domes. This approach can be adopted for various applications like solid rocket motor casings, automobile fuel storage tanks and chemical storage tanks. Based on the predictions a composite pressure vessel is designed and developed. Hydraulic test is performed on the composite pressure vessel till the burst pressure.

Structural integrity of engineering composite materials: a cracking good yarn.

PubMed

Beaumont, Peter W R; Soutis, Costas

2016-07-13

Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large-scale engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a 'fracture safe design' is immense. Fitness considerations for long-life implementation of large composite structures include understanding phenomena such as impact, fatigue, creep and stress corrosion cracking that affect reliability, life expectancy and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined, and takes service duty into account. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk. This article is part of the themed issue 'Multiscale modelling of the structural integrity of composite materials'. © 2016 The Author(s).

Applied Integrated Design in Composite UAV Development

NASA Astrophysics Data System (ADS)

Vasić, Zoran; Maksimović, Stevan; Georgijević, Dragutin

2018-04-01

This paper presents a modern approach to integrated development of Unmanned Aerial Vehicle made of laminated composite materials from conceptual design, through detail design, strength and stiffness analyses, definition and management of design and production data, detailed tests results and other activities related to development of laminated composite structures with main of its particularities in comparison to metal structures. Special attention in this work is focused to management processes of product data during life cycle of an UAV and experimental tests of its composite wing. Experience shows that the automation management processes of product data during life cycle, as well as processes of manufacturing, are inevitable if a company wants to get cheaper and quality composite aircraft structures. One of the most effective ways of successful management of product data today is Product Life cycle Management (PLM). In terms of the PLM, a spectrum of special measures and provisions has to be implemented when defining fiber-reinforced composite material structures in comparison to designing with metals which is elaborated in the paper.

Development of an embedded thin-film strain-gauge-based SHM network into 3D-woven composite structure for wind turbine blades

NASA Astrophysics Data System (ADS)

Zhao, Dongning; Rasool, Shafqat; Forde, Micheal; Weafer, Bryan; Archer, Edward; McIlhagger, Alistair; McLaughlin, James

2017-04-01

Recently, there has been increasing demand in developing low-cost, effective structure health monitoring system to be embedded into 3D-woven composite wind turbine blades to determine structural integrity and presence of defects. With measuring the strain and temperature inside composites at both in-situ blade resin curing and in-service stages, we are developing a novel scheme to embed a resistive-strain-based thin-metal-film sensory into the blade spar-cap that is made of composite laminates to determine structural integrity and presence of defects. Thus, with fiberglass, epoxy, and a thinmetal- film sensing element, a three-part, low-cost, smart composite laminate is developed. Embedded strain sensory inside composite laminate prototype survived after laminate curing process. The internal strain reading from embedded strain sensor under three-point-bending test standard is comparable. It proves that our proposed method will provide another SHM alternative to reduce sensing costs during the renewable green energy generation.

Nonlinear analysis for high-temperature multilayered fiber composite structures. M.S. Thesis; [turbine blades

NASA Technical Reports Server (NTRS)

Hopkins, D. A.

1984-01-01

A unique upward-integrated top-down-structured approach is presented for nonlinear analysis of high-temperature multilayered fiber composite structures. Based on this approach, a special purpose computer code was developed (nonlinear COBSTRAN) which is specifically tailored for the nonlinear analysis of tungsten-fiber-reinforced superalloy (TFRS) composite turbine blade/vane components of gas turbine engines. Special features of this computational capability include accounting of; micro- and macro-heterogeneity, nonlinear (stess-temperature-time dependent) and anisotropic material behavior, and fiber degradation. A demonstration problem is presented to mainfest the utility of the upward-integrated top-down-structured approach, in general, and to illustrate the present capability represented by the nonlinear COBSTRAN code. Preliminary results indicate that nonlinear COBSTRAN provides the means for relating the local nonlinear and anisotropic material behavior of the composite constituents to the global response of the turbine blade/vane structure.

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.

Fibre Optic Sensors for Structural Health Monitoring of Aircraft Composite Structures: Recent Advances and Applications

PubMed Central

Di Sante, Raffaella

2015-01-01

In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques. PMID:26263987

Fibre Optic Sensors for Structural Health Monitoring of Aircraft Composite Structures: Recent Advances and Applications.

PubMed

Di Sante, Raffaella

2015-07-30

In-service structural health monitoring of composite aircraft structures plays a key role in the assessment of their performance and integrity. In recent years, Fibre Optic Sensors (FOS) have proved to be a potentially excellent technique for real-time in-situ monitoring of these structures due to their numerous advantages, such as immunity to electromagnetic interference, small size, light weight, durability, and high bandwidth, which allows a great number of sensors to operate in the same system, and the possibility to be integrated within the material. However, more effort is still needed to bring the technology to a fully mature readiness level. In this paper, recent research and applications in structural health monitoring of composite aircraft structures using FOS have been critically reviewed, considering both the multi-point and distributed sensing techniques.

Monitoring of Structural Integrity of Composite Structures by Embedded Optical Fiber Sensors

NASA Technical Reports Server (NTRS)

Osei, Albert J.

2002-01-01

Real time monitoring of the mechanical integrity and stresses on key aerospace composite structures like aircraft wings, walls of pressure vessels and fuel tanks or any other structurally extended components and panels as in space telescopes is very important to NASA. Future military and commercial aircraft as well as NASA space systems such as Space Based Radar and International Space Station will incorporate a monitoring system to sense any degradation to the structure. In the extreme flight conditions of an aerospace vehicle it might be desirable to measure the strain every ten centimeters and thus fully map out the strain field of a composite component. A series of missions and vehicle health management requirements call for these measurements. At the moment thousands of people support a few vehicle launches per year. This number can be significantly reduced by implementing intelligent vehicles with integral nervous systems (smart structures). This would require maintenance to be performed only as needed. Military and commercial aircrafts have an equally compelling case. Maintenance yearly costs are currently reaching astronomical heights. Monitoring techniques are therefore required that allow for maintenance to be performed only when needed. This would allow improved safety by insuring that necessary tasks are performed while reducing costs by eliminating procedures that are costly and not needed. The advantages fiber optical sensors have over conventional electro-mechanical systems like strain gauges have been widely extolled in the research literature. These advantages include their small size, low weight, immunity to electrical resistance, corrosion resistance, compatibility with composite materials and process conditions, and multiplexing capabilities. One fiber optic device which is suitable for distributed sensing is the fiber Bragg grating (FBG). Researchers at NASA MSFC are currently developing techniques for using FBGs for monitoring the integrity of advanced structural materials expected to become the mainstay of the current and future generation space structures. Since carbon-epoxy composites are the materials of choice for the current space structures, the initial study is concentrated on this type of composite. The goals of this activity are to use embedded FBG sensors for measuring strain and temperature of composite structures, and to investigate the effects of various parameters such as composite fiber orientation with respect to the optical sensor, unidirectional fiber composite, fabrication process etc., on the optical performance of the sensor. This paper describes an experiment to demonstrate the use of an embedded FBG for measuring strain in a composite material. The performance of the fiber optic sensor is determined by direct comparison with results from more conventional instrumentation.

Flight service evaluation of an advanced composite empennage component on commercial transport aircraft. Phase 1: Engineering development

NASA Technical Reports Server (NTRS)

Ary, A.; Axtell, C.; Fogg, L.; Jackson, A.; James, A. M.; Mosesian, B.; Vanderwier, J.; Vanhamersveld, J.

1976-01-01

The empennage component selected for this program is the vertical fin box of the L-1011 aircraft. The box structure extends from the fuselage production joint to the tip rib and includes the front and rear spars. Various design options were evaluated to arrive at a configuration which would offer the highest potential for satisfying program objectives. The preferred configuration selected consists of a hat-stiffened cover with molded integrally stiffened spars, aluminum trussed composite ribs, and composite miniwich web ribs with integrally molded caps. Material screening tests were performed to select an advanced composite material system for the Advanced Composite Vertical Fin (ACFV) that would meet the program requirements from the standpoint of quality, reproducibility, and cost. Preliminary weight and cost analysis were made, targets established, and tracking plans developed. These include FAA certification, ancillary test program, quality control, and structural integrity control plans.

Progressive Fracture of Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2008-01-01

A new approach is described for evaluating fracture in composite structures. This approach is independent of classical fracture mechanics parameters like fracture toughness. It relies on computational simulation and is programmed in a stand-alone integrated computer code. It is multiscale, multifunctional because it includes composite mechanics for the composite behavior and finite element analysis for predicting the structural response. It contains seven modules; layered composite mechanics (micro, macro, laminate), finite element, updating scheme, local fracture, global fracture, stress based failure modes, and fracture progression. The computer code is called CODSTRAN (Composite Durability Structural ANalysis). It is used in the present paper to evaluate the global fracture of four composite shell problems and one composite built-up structure. Results show that the composite shells and the built-up composite structure global fracture are enhanced when internal pressure is combined with shear loads.

Composite structural materials

NASA Technical Reports Server (NTRS)

Loewy, R.; Wiberley, S. E.

1986-01-01

Overall emphasis is on basic long-term research in the following categories: constituent materials, composite materials, generic structural elements, processing science technology; and maintaining long-term structural integrity. Research in basic composition, characteristics, and processing science of composite materials and their constituents is balanced against the mechanics, conceptual design, fabrication, and testing of generic structural elements typical of aerospace vehicles so as to encourage the discovery of unusual solutions to present and future problems. Detailed descriptions of the progress achieved in the various component parts of this comprehensive program are presented.

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.

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

An Integrated, Layered-Spinel Composite Cathode for Energy Storage Applications

NASA Technical Reports Server (NTRS)

Hagh, Nader; Skandan, Ganesh

2012-01-01

At low operating temperatures, commercially available electrode materials for lithium-ion batteries do not fully meet the energy and power requirements for NASA fs exploration activities. The composite cathode under development is projected to provide the required energy and power densities at low temperatures and its usage will considerably reduce the overall volume and weight of the battery pack. The newly developed composite electrode material can provide superior electrochemical performance relative to a commercially available lithium cobalt system. One advantage of using a composite cathode is its higher energy density, which can lead to smaller and lighter battery packs. In the current program, different series of layered-spinel composite materials with at least two different systems in an integrated structure were synthesized, and the volumetric and gravimetric energy densities were evaluated. In an integrated network of a composite electrode, the effect of the combined structures is to enhance the capacity and power capabilities of the material to levels greater than what is possible in current state-of-the-art cathode systems. The main objective of the current program is to implement a novel cathode material that meets NASA fs low temperature energy density requirements. An important feature of the composite cathode is that it has at least two components (e.g., layered and spinel) that are structurally integrated. The layered material by itself is electrochemically inactive; however, upon structural integration with a spinel material, the layered material can be electrochemically activated, thereby delivering a large amount of energy with stable cycling. A key aspect of the innovation has been the development of a scalable process to produce submicronand micron-scale particles of these composite materials. An additional advantage of using such a composite electrode material is its low irreversible loss (.5%), which is primarily due to the unique activation of the composite. High columbic efficiency (greater than 99%) upon cycling may indicate the formation of a stable SEI (solid-electrolyte interface) layer, which can contribute to long cycle life. The innovation in the current program, when further developed, will enable the system to maintain high energy and power densities at low temperatures, improve efficiency, and further stabilize and enhance the safety of the cell.

Electrostatic adhesion for added functionality of composite structures

NASA Astrophysics Data System (ADS)

Heath, Callum J. C.; Bond, Ian P.; Potter, Kevin D.

2016-02-01

Electrostatic adhesion can be used as a means of reversible attachment. The incorporation of electrostatic adhesion into fibre reinforced polymer (FRP) composite structures could provide significant value added functionality. Imparting large potential differences (˜2 kV) across electrodes generates an attractive force, thus providing a means of attachment. This could be used as a reversible latching mechanism or as a means of controllable internal connectivity. Varying the connectivity for discrete elements of a substructure of a given design allows for control of internal load paths and moment of area of the cross section. This could facilitate variable stiffness (both in bending and torsion). Using a combination of existing fabrication techniques, functional electrodes have been integrated within a FRP. Copper polyimide thin film laminate material has been both co-cured with carbon fibre reinforced epoxy and bonded to PVC closed cell foam core material to provide a range of structural configurations with integrated electrodes. The ability of such integrated devices to confer variations in global bending stiffness of basic beam structures is investigated. Through the application of 4 kV across integrated electrostatic adhesive devices, a 112% increase in flexural stiffness has been demonstrated for a composite sandwich structure.

Structural Integrity Of Low-Velocity Impacted C/SIC Ceramic Matrix Composites

NASA Astrophysics Data System (ADS)

Knoche, R.; Drose, A.

2012-07-01

Carbon fibre reinforced silicon carbide (C/SiC) ceramic matrix composites (CMC) are most favourable for thermal protection systems & hot structures in re-entry vehicles since they offer superior heat resistance, high specific strength as well as a low coefficient of temperature expansion (CTE). To ensure the structural integrity of these C/SiC structures and thus mission safety all potential degradation effects during manufacturing and lifetime have to be considered. One of the most probable defects which may harm the structural integrity significantly can be caused by low-velocity impacts (LVI) which may occur during transportation and integration by e.g. dropping of tools. Thus the present study focuses on the residual mechanical and thermo-mechanical performance of C/SiC composites after being exposed to a low-velocity impact in terms of initial and residual mechanical performance, changes in microstructure, as well as thermo-mechanical performance through exposing specimens to multiple experimentally simulated re-entries. The results reveal the impact characteristics and damage mechanisms of C/SiC CMC exposed to a low-velocity impact and evidence the functional reliability as well as the damage tolerance of the C/SiC material investigated.

Composite structural materials. [fiber reinforced composites for aircraft structures

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberly, S. E.

1981-01-01

Physical properties of fiber reinforced composites; structural concepts and analysis; manufacturing; reliability; and life prediction are subjects of research conducted to determine the long term integrity of composite aircraft structures under conditions pertinent to service use. Progress is reported in (1) characterizing homogeneity in composite materials; (2) developing methods for analyzing composite materials; (3) studying fatigue in composite materials; (4) determining the temperature and moisture effects on the mechanical properties of laminates; (5) numerically analyzing moisture effects; (6) numerically analyzing the micromechanics of composite fracture; (7) constructing the 727 elevator attachment rib; (8) developing the L-1011 engine drag strut (CAPCOMP 2 program); (9) analyzing mechanical joints in composites; (10) developing computer software; and (11) processing science and technology, with emphasis on the sailplane project.

Unibody Composite Pressurized Structure

NASA Technical Reports Server (NTRS)

Rufer, Markus; Conger, Robert; Bauer, Thomas; Newman, John

2013-01-01

An integrated, generic unibody composite pressurized structure (UCPS) combined with a positive expulsion device (PED), consisting of an elastomeric bladder for monopropellant hydrazine, has been quasi-standardized for spacecraft use. The combination functions as an all-composite, non-metallic, propellant tank with bladder. The integrated UCPS combines several previous innovations - specifically, the linerless, all-composite cryogenic tank technology; all-composite boss; resin formulation; and integrated stringer system. The innovation combines the UCPS with an integrated propellant management device (PMD), the PED or bladder, to create an entirely unique system for in-space use. The UCPS is a pressure vessel that incorporates skirts, stringers, and other structures so that it is both an in-space hydrazine tank, and also a structural support system for a spacecraft in a single, all-composite unit. This innovation builds on the progress in the development of a previous SBIR (Small Business Innovation Research) Phase I with Glenn Research Center and an SBIR III with Johnson Space Center that included the fabrication of two 42-in. (˜107-cm) diameter all-composite cryogenic (LOX and liquid methane) UCPS test tanks for a lunar lander. This Phase II provides hydra zine compatibility testing of the elastomeric bladder, a see-through PED to validate the expulsion process and model, and a complete UCPS-based PED with stringers and skirts that will be used to conduct initial qualification and expulsion tests. This extends the UCPS technology to include hydrazine-based, in-space pro - pulsion applications and can also be used for electric propulsion. This innovation creates a system that, in comparison to the traditional approach, is lower in weight, cost, volume, and production time; is stronger; and is capable of much higher pressures. It also has fewer failure modes, and is applicable to both chemical and electric propulsion systems.

Composite membranes and methods for making same

DOEpatents

Routkevitch, Dmitri; Polyakov, Oleg G

2012-07-03

Composite membranes that are adapted for separation, purification, filtration, analysis, reaction and sensing. The composite membranes can include a porous support structure having elongate pore channels extending through the support structure. The composite membrane also includes an active layer comprising an active layer material, where the active layer material is completely disposed within the pore channels between the surfaces of the support structure. The active layer is intimately integrated within the support structure, thus enabling great robustness, reliability, resistance to mechanical stress and thermal cycling, and high selectivity. Methods for the fabrication of composite membranes are also provided.

Progressive Fracture of Fiber Composite Build-Up Structures

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, C. C.; Minnetyan, Levon

1997-01-01

Damage progression and fracture of built-up composite structures is evaluated by using computational simulation. The objective is to examine the behavior and response of a stiffened composite (0/ +/- 45/90)(sub s6) laminate panel by simulating the damage initiation, growth, accumulation, progression and propagation to structural collapse. An integrated computer code, CODSTRAN, was augmented for the simulation of the progressive damage and fracture of built-up composite structures under mechanical loading. Results show that damage initiation and progression have significant effect on the structural response. Influence of the type of loading is investigated on the damage initiation, propagation and final fracture of the build-up composite panel.

Progressive Fracture of Fiber Composite Build-Up Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Gotsis, Pascal K.; Chamis, C. C.

1997-01-01

Damage progression and fracture of built-up composite structures is evaluated by using computational simulation. The objective is to examine the behavior and response of a stiffened composite (0 +/-45/90)(sub s6) laminate panel by simulating the damage initiation, growth, accumulation, progression and propagation to structural collapse. An integrated computer code CODSTRAN was augmented for the simulation of the progressive damage and fracture of built-up composite structures under mechanical loading. Results show that damage initiation and progression to have significant effect on the structural response. Influence of the type of loading is investigated on the damage initiation, propagation and final fracture of the build-up composite panel.

Structural Durability of Damaged Metallic Panel Repaired with Composite Patches

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C.

1997-01-01

Structural durability/damage tolerance characteristics of an aluminum tension specimen possessing a short crack and repaired by applying a fiber composite surface patch is investigated via computational simulation. The composite patch is made of graphite/epoxy plies with various layups. An integrated computer code that accounts for all possible failure modes is utilized for the simulation of combined fiber-composite/aluminum structural degradation under loading. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. Results show the structural degradation stages due to tensile loading and illustrate the use of computational simulation for the investigation of a composite patch repaired cracked metallic panel.

Advanced technology composite aircraft structures

NASA Technical Reports Server (NTRS)

Ilcewicz, Larry B.; Walker, Thomas H.

1991-01-01

Work performed during the 25th month on NAS1-18889, Advanced Technology Composite Aircraft Structures, is summarized. The main objective of this program is to develop an integrated technology and demonstrate a confidence level that permits the cost- and weight-effective use of advanced composite materials in primary structures of future aircraft with the emphasis on pressurized fuselages. The period from 1-31 May 1991 is covered.

Three-Dimensional Microvascular Fiber-Reinforced Composites

DTIC Science & Technology

2011-03-01

are varied to meet the desired design criteria. The interstitial pore space between fi bers is infi ltrated with a low- viscosity thermosetting resin...depolymerization and monomer vaporization results in a 3D microvascular network integrated into a structural composite; d) fl uid (yellow) fi lls...VaSC method uses commercially available materials and can be seamlessly integrated with conventional fi ber-reinforced composite manufacturing

Composite structural materials

NASA Technical Reports Server (NTRS)

Ansell, G. S.; Loewy, R. G.; Wiberley, S. E.

1984-01-01

Progress is reported in studies of constituent materials composite materials, generic structural elements, processing science technology, and maintaining long-term structural integrity. Topics discussed include: mechanical properties of high performance carbon fibers; fatigue in composite materials; experimental and theoretical studies of moisture and temperature effects on the mechanical properties of graphite-epoxy laminates and neat resins; numerical investigations of the micromechanics of composite fracture; delamination failures of composite laminates; effect of notch size on composite laminates; improved beam theory for anisotropic materials; variation of resin properties through the thickness of cured samples; numerical analysis composite processing; heat treatment of metal matrix composites, and the RP-1 and RP2 gliders of the sailplane project.

Progressive Damage and Fracture of Unstiffened and Stiffened Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Gotsis, Pascal K.; Chamis, Christos C.

1997-01-01

Structural durability and damage tolerance characteristics of pressurized graphite/epoxy laminated thin composite cylinders are investigated via computational simulation. Both unstiffened and integral hoop stiffened cylinders are considered. A computer code is utilized for the simulation of composite structural degradation under loading. Damage initiation, growth, accumulation, and propagation to structural fracture are included in the simulation. The increase of burst pressure due to hoop stiffening is quantified. Results demonstrate the significance of the type and size of local defects on the structural durability of pressurized composite cylindrical shells.

Materials and structures technology insertion into spacecraft systems: Successes and challenges

NASA Astrophysics Data System (ADS)

Rawal, Suraj

2018-05-01

Over the last 30 years, significant advancements have led to the use of multifunctional materials and structures technologies in spacecraft systems. This includes the integration of adaptive structures, advanced composites, nanotechnology, and additive manufacturing technologies. Development of multifunctional structures has been directly influenced by the implementation of processes and tools for adaptive structures pioneered by Prof. Paolo Santini. Multifunctional materials and structures incorporating non-structural engineering functions such as thermal, electrical, radiation shielding, power, and sensors have been investigated. The result has been an integrated structure that offers reduced mass, packaging volume, and ease of integration for spacecraft systems. Current technology development efforts are being conducted to develop innovative multifunctional materials and structures designs incorporating advanced composites, nanotechnology, and additive manufacturing. However, these efforts offer significant challenges in the qualification and acceptance into spacecraft systems. This paper presents a brief overview of the technology development and successful insertion of advanced material technologies into spacecraft structures. Finally, opportunities and challenges to develop and mature next generation advanced materials and structures are presented.

Flame-Resistant Composite Materials For Structural Members

NASA Technical Reports Server (NTRS)

Spears, Richard K.

1995-01-01

Matrix-fiber composite materials developed for structural members occasionally exposed to hot, corrosive gases. Integral ceramic fabric surface layer essential for resistance to flames and chemicals. Endures high temperature, impedes flame from penetrating to interior, inhibits diffusion of oxygen to interior where it degrades matrix resin, resists attack by chemicals, helps resist erosion, and provides additional strength. In original intended application, composite members replace steel structural members of rocket-launching structures that deteriorate under combined influences of atmosphere, spilled propellants, and rocket exhaust. Composites also attractive for other applications in which corrosion- and fire-resistant structural members needed.

Key issues in application of composites to transport aircraft

NASA Technical Reports Server (NTRS)

Stone, M.

1978-01-01

The application of composite materials to transport aircraft was identified and reviewed including the major contributing disciplines of design, manufacturing, and processing. Factors considered include: crashworthiness considerations (structural integrity, postcrash fires, and structural fusing), electrical/avionics subsystems integration, lightning, and P-static protection design; manufacturing development, evaluation, selection, and refining of tooling and curing procedures; and major joint design considerations. Development of the DC-10 rudder, DC-10 vertical stabilizer, and the DC-9 wing study project was reviewed. The Federal Aviation Administration interface and the effect on component design of compliance with Federal Aviation Regulation 25 Composite Guidelines are discussed.

Probabilistic evaluation of fuselage-type composite structures

NASA Technical Reports Server (NTRS)

Shiao, Michael C.; Chamis, Christos C.

1992-01-01

A methodology is developed to computationally simulate the uncertain behavior of composite structures. The uncertain behavior includes buckling loads, natural frequencies, displacements, stress/strain etc., which are the consequences of the random variation (scatter) of the primitive (independent random) variables in the constituent, ply, laminate and structural levels. This methodology is implemented in the IPACS (Integrated Probabilistic Assessment of Composite Structures) computer code. A fuselage-type composite structure is analyzed to demonstrate the code's capability. The probability distribution functions of the buckling loads, natural frequency, displacement, strain and stress are computed. The sensitivity of each primitive (independent random) variable to a given structural response is also identified from the analyses.

Assessment of the State-of-the-Art in the Design and Manufacturing of Large Composite Structure

NASA Technical Reports Server (NTRS)

Harris, C. E.

2001-01-01

This viewgraph presentation gives an assessment of the state-of-the-art in the design and manufacturing of large component structures, including details on the use of continuous fiber reinforced polymer matrix composites (CFRP) in commercial and military aircraft and in space launch vehicles. Project risk mitigation plans must include a building-block test approach to structural design development, manufacturing process scale-up development tests, and pre-flight ground tests to verify structural integrity. The potential benefits of composite structures justifies NASA's investment in developing the technology. Advanced composite structures technology is enabling to virtually every Aero-Space Technology Enterprise Goal.

The effect of nanoparticle enhanced sizing on the structural health monitoring sensitivity and mechanical properties of carbon fiber composites

NASA Astrophysics Data System (ADS)

Bowland, Christopher C.; Nguyen, Ngoc A.; Naskar, Amit K.

2018-03-01

With current carbon composites being introduced into new commercial market sectors, there is an opportunity to develop multifunctional composites, which are poised to be the next generation of composites that will see future commercial applications. This multifunctional attribute can be achieved via integrated nanomaterials, which are currently under-utilized in real-world applications despite significant research efforts focused on their synthesis. This research utilizes a simple, scalable approach to integrate various nanomaterials into carbon fiber composites by embedding the nanomaterials in the epoxy fiber sizing. Illustrated in this work is the effect of silicon carbide nanoparticle concentrations and dimensions on the structural health monitoring sensitivity of unidirectional carbon fiber composites. Additionally, the nanoparticles contribute to the overall damping property of the composites thus enabling tunable damping through simple variations in nanoparticle concentration and size. Not only does this nanoparticle sizing offer enhanced sensitivity and tunable damping, but it also maintains the mechanical integrity and performance of the composites, which demonstrates a truly multifunctional composite. Therefore, this research establishes an efficient route for combining nanomaterials research with real-world multifunctional composite applications using a technique that is easily scalable to the commercial level and is compatible with a wide range of fibers and nanomaterials.

Progressive Fracture of Fiber Composite Builtup Structures

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, Christos C.; Minnetyan, Levon

1996-01-01

The damage progression and fracture of builtup composite structures was evaluated by using computational simulation to examine the behavior and response of a stiffened composite (0 +/- 45/90)(sub s6) laminate panel subjected to a bending load. The damage initiation, growth, accumulation, progression, and propagation to structural collapse were simulated. An integrated computer code (CODSTRAN) was augmented for the simulation of the progressive damage and fracture of builtup composite structures under mechanical loading. Results showed that damage initiation and progression have a significant effect on the structural response. Also investigated was the influence of different types of bending load on the damage initiation, propagation, and final fracture of the builtup composite panel.

Inert Welding/Brazing Gas Filters and Dryers

NASA Technical Reports Server (NTRS)

Goudy, Jerry

2009-01-01

The use of hybridized carbon/silicon carbide (C/SiC) fabric to reinforce ceramic matrix composite face sheets and the integration of such face sheets with a foam core creates a sandwich structure capable of withstanding high-heat-flux environments (150 W/sq cm) in which the core provides a temperature drop of 1,000 C between the surface and the back face without cracking or delamination of the structure. The composite face sheet exhibits a bilinear response, which results from the SiC matrix not being cracked on fabrication. In addition, the structure exhibits damage tolerance under impact with projectiles, showing no penetration to the back face sheet. These attributes make the composite ideal for leading-edge structures and control surfaces in aerospace vehicles, as well as for acreage thermal protection systems and in high-temperature, lightweight stiffened structures. By tailoring the coefficient of thermal expansion (CTE) of a carbon fiber containing ceramic matrix composite (CMC) face sheet to match that of a ceramic foam core, the face sheet and the core can be integrally fabricated without any delamination. Carbon and SiC are woven together in the reinforcing fabric. Integral densification of the CMC and the foam core is accomplished with chemical vapor deposition, eliminating the need for bond-line adhesive. This means there is no need to separately fabricate the core and the face sheet, or to bond the two elements together, risking edge delamination during use. Fibers of two or more types are woven together on a loom. The carbon and ceramic fibers are pulled into the same "pick" location during the weaving process. Tow spacing may be varied to accommodate the increased volume of the combined fiber tows while maintaining a target fiber volume fraction in the composite. Foam pore size, strut thickness, and ratio of face sheet to core thickness can be used to tailor thermal and mechanical properties. The anticipated CTE for the hybridized composite is managed by the choice of constituents, varying fiber tow sizes and constituent part ratios. This structural concept provides high strength and stiffness at low density 1.06 g/cu cm in panels tested. Varieties of face sheet constructions are possible, including variations in fiber type and weave geometry. The integrated structures possible with this composite could eliminate the need for non-load-bearing thermal protection systems on top of a structural component. The back sheet can readily be integrated to substructures through the incorporation of ribs. This would eliminate weight and cost for aerospace missions.

Multiscale Multifunctional Progressive Fracture of Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Minnetyan, L.

2012-01-01

A new approach is described for evaluating fracture in composite structures. This approach is independent of classical fracture mechanics parameters like fracture toughness. It relies on computational simulation and is programmed in a stand-alone integrated computer code. It is multiscale, multifunctional because it includes composite mechanics for the composite behavior and finite element analysis for predicting the structural response. It contains seven modules; layered composite mechanics (micro, macro, laminate), finite element, updating scheme, local fracture, global fracture, stress based failure modes, and fracture progression. The computer code is called CODSTRAN (Composite Durability Structural ANalysis). It is used in the present paper to evaluate the global fracture of four composite shell problems and one composite built-up structure. Results show that the composite shells. Global fracture is enhanced when internal pressure is combined with shear loads. The old reference denotes that nothing has been added to this comprehensive report since then.

Additive manufacturing of RF absorbers

NASA Astrophysics Data System (ADS)

Mills, Matthew S.

The ability of additive manufacturing techniques to fabricate integrated electromagnetic absorbers tuned for specific radio frequency bands within structural composites allows for unique combinations of mechanical and electromagnetic properties. These composites and films can be used for RF shielding of sensitive electromagnetic components through in-plane and out-of-plane RF absorption. Structural composites are a common building block of many commercial platforms. These platforms may be placed in situations in which there is a need for embedded RF absorbing properties along with structural properties. Instead of adding radar absorbing treatments to the external surface of existing structures, which adds increased size, weight and cost; it could prove to be advantageous to integrate the microwave absorbing properties directly into the composite during the fabrication process. In this thesis, a method based on additive manufacturing techniques of composites structures with prescribed electromagnetic loss, within the frequency range 1 to 26GHz, is presented. This method utilizes screen printing and nScrypt micro dispensing to pattern a carbon based ink onto low loss substrates. The materials chosen for this study will be presented, and the fabrication technique that these materials went through to create RF absorbing structures will be described. The calibration methods used, the modeling of the RF structures, and the applications in which this technology can be utilized will also be presented.

Design for cyclic loading endurance of composites

NASA Technical Reports Server (NTRS)

Shiao, Michael C.; Murthy, Pappu L. N.; Chamis, Christos C.; Liaw, Leslie D. G.

1993-01-01

The application of the computer code IPACS (Integrated Probabilistic Assessment of Composite Structures) to aircraft wing type structures is described. The code performs a complete probabilistic analysis for composites taking into account the uncertainties in geometry, boundary conditions, material properties, laminate lay-ups, and loads. Results of the analysis are presented in terms of cumulative distribution functions (CDF) and probability density function (PDF) of the fatigue life of a wing type composite structure under different hygrothermal environments subjected to the random pressure. The sensitivity of the fatigue life to a number of critical structural/material variables is also computed from the analysis.

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.

Integrated design of structures, controls, and materials

NASA Technical Reports Server (NTRS)

Blankenship, G. L.

1994-01-01

In this talk we shall discuss algorithms and CAD tools for the design and analysis of structures for high performance applications using advanced composite materials. An extensive mathematical theory for optimal structural (e.g., shape) design was developed over the past thirty years. Aspects of this theory have been used in the design of components for hypersonic vehicles and thermal diffusion systems based on homogeneous materials. Enhancement of the design methods to include optimization of the microstructure of the component is a significant innovation which can lead to major enhancements in component performance. Our work is focused on the adaptation of existing theories of optimal structural design (e.g., optimal shape design) to treat the design of structures using advanced composite materials (e.g., fiber reinforced, resin matrix materials). In this talk we shall discuss models and algorithms for the design of simple structures from composite materials, focussing on a problem in thermal management. We shall also discuss methods for the integration of active structural controls into the design process.

Structural Health Monitoring of Composite Wound Pressure Vessels

NASA Technical Reports Server (NTRS)

Grant, Joseph; Kaul, Raj; Taylor, Scott; Jackson, Kurt; Myers, George; Sharma, A.

2002-01-01

The increasing use of advanced composite materials in the wide range of applications including Space Structures is a great impetus to the development of smart materials. Incorporating these FBG sensors for monitoring the integrity of structures during their life cycle will provide valuable information about viability of the usage of such material. The use of these sensors by surface bonding or embedding in this composite will measure internal strain and temperature, and hence the integrity of the assembled engineering structures. This paper focuses on such a structure, called a composite wound pressure vessel. This vessel was fabricated from the composite material: TRH50 (a Mitsubishi carbon fiber with a 710-ksi tensile strength and a 37 Msi modulus) impregnated with an epoxy resin from NEWPORT composites (WDE-3D-1). This epoxy resin in water dispersed system without any solvents and it cures in the 240-310 degrees F range. This is a toughened resin system specifically designed for pressure applications. These materials are a natural fit for fiber sensors since the polyimide outer buffer coating of fiber can be integrated into the polymer matrix of the composite material with negligible residual stress. The tank was wound with two helical patterns and 4 hoop wraps. The order of winding is: two hoops, two helical and two hoops. The wall thickness of the composite should be about 80 mil or less. The tank should burst near 3,000 psi or less. We can measure the actual wall thickness by ultrasonic or we can burst the tank and measure the pieces. Figure 1 shows a cylinder fabricated out of carbon-epoxy composite material. The strain in different directions is measured with a surface bonded fiber Bragg gratings and with embedded fiber Bragg gratings as the cylinder is pressurized to burst pressures. Figure 2 shows the strain as a function of pressure of carbon-epoxy cylinder as it is pressurized with water. Strain is measured in different directions by multiple gratings oriented in both axial and hoops directions.

Probabilistic Assessment of Fracture Progression in Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon; Mauget, Bertrand; Huang, Dade; Addi, Frank

1999-01-01

This report describes methods and corresponding computer codes that are used to evaluate progressive damage and fracture and to perform probabilistic assessment in built-up composite structures. Structural response is assessed probabilistically, during progressive fracture. The effects of design variable uncertainties on structural fracture progression are quantified. The fast probability integrator (FPI) is used to assess the response scatter in the composite structure at damage initiation. The sensitivity of the damage response to design variables is computed. The methods are general purpose and are applicable to stitched and unstitched composites in all types of structures and fracture processes starting from damage initiation to unstable propagation and to global structure collapse. The methods are demonstrated for a polymer matrix composite stiffened panel subjected to pressure. The results indicated that composite constituent properties, fabrication parameters, and respective uncertainties have a significant effect on structural durability and reliability. Design implications with regard to damage progression, damage tolerance, and reliability of composite structures are examined.

Design and Optimization of Composite Automotive Hatchback Using Integrated Material-Structure-Process-Performance Method

NASA Astrophysics Data System (ADS)

Yang, Xudong; Sun, Lingyu; Zhang, Cheng; Li, Lijun; Dai, Zongmiao; Xiong, Zhenkai

2018-03-01

The application of polymer composites as a substitution of metal is an effective approach to reduce vehicle weight. However, the final performance of composite structures is determined not only by the material types, structural designs and manufacturing process, but also by their mutual restrict. Hence, an integrated "material-structure-process-performance" method is proposed for the conceptual and detail design of composite components. The material selection is based on the principle of composite mechanics such as rule of mixture for laminate. The design of component geometry, dimension and stacking sequence is determined by parametric modeling and size optimization. The selection of process parameters are based on multi-physical field simulation. The stiffness and modal constraint conditions were obtained from the numerical analysis of metal benchmark under typical load conditions. The optimal design was found by multi-discipline optimization. Finally, the proposed method was validated by an application case of automotive hatchback using carbon fiber reinforced polymer. Compared with the metal benchmark, the weight of composite one reduces 38.8%, simultaneously, its torsion and bending stiffness increases 3.75% and 33.23%, respectively, and the first frequency also increases 44.78%.

Finite element analysis and optimization of composite structures

NASA Technical Reports Server (NTRS)

Thomsen, Jan

1990-01-01

Linearly elastic fiber reinforced composite discs and laminates in plane stress with variable local orientation and concentration of one or two fiber fields embedded in the matrix material, are considered. The thicknesses and the domain of the discs or laminates are assumed to be given, together with prescribed boundary conditions and in-plane loading along the edge. The problem under study consists in determining throughout the structural domain the optimum orientations and concentrations of the fiber fields in such a way as to maximize the integral stiffness of the composite disc or laminate under the seven loading. Minimization of the integral stiffness can also be performed. The optimization is performed subject to a prescribed bound on the total cost or weight of the composite that for given unit cost factors or specific weights determines the amounts of fiber and matrix materials in the structure. Examples are presented.

Composite isogrid structures for parabolic surfaces

NASA Technical Reports Server (NTRS)

Silverman, Edward M. (Inventor); Boyd, Jr., William E. (Inventor); Rhodes, Marvin D. (Inventor); Dyer, Jack E. (Inventor)

2000-01-01

The invention relates to high stiffness parabolic structures utilizing integral reinforced grids. The parabolic structures implement the use of isogrid structures which incorporate unique and efficient orthotropic patterns for efficient stiffness and structural stability.

Reflexive composites: self-healing composite structures

NASA Astrophysics Data System (ADS)

Margraf, Thomas W., Jr.; Barnell, Thomas J.; Havens, Ernie; Hemmelgarn, Christopher D.

2008-03-01

Cornerstone Research Group Inc. has developed reflexive composites achieving increased vehicle survivability through integrated structural awareness and responsiveness to damage. Reflexive composites can sense damage through integrated piezoelectric sensing networks and respond to damage by heating discrete locations to activate the healable polymer matrix in areas of damage. The polymer matrix is a modified thermoset shape memory polymer that heals based on phenomena known as reptation. In theory, the reptation healing phenomena should occur in microseconds; however, during experimentation, it has been observed that to maximize healing and restore up to 85 % of mechanical properties a healing cycle of at least three minutes is required. This paper will focus on work conducted to determine the healing mechanisms at work in CRG's reflexive composites, the optimal healing cycles, and an explanation of the difference between the reptation model and actual healing times.

Electroactive nanoparticle directed assembly of functionalized graphene nanosheets into hierarchical structures with hybrid compositions for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Choi, Bong Gill; Huh, Yun Suk; Hong, Won Hi; Erickson, David; Park, Ho Seok

2013-04-01

Hierarchical structures of hybrid materials with the controlled compositions have been shown to offer a breakthrough for energy storage and conversion. Here, we report the integrative assembly of chemically modified graphene (CMG) building blocks into hierarchical complex structures with the hybrid composition for high performance flexible pseudocapacitors. The formation mechanism of hierarchical CMG/Nafion/RuO2 (CMGNR) microspheres, which is triggered by the cooperative interplay during the in situ synthesis of RuO2 nanoparticles (NPs), was extensively investigated. In particular, the hierarchical CMGNR microspheres consisting of the aggregates of CMG/Nafion (CMGN) nanosheets and RuO2 NPs provided large surface area and facile ion accessibility to storage sites, while the interconnected nanosheets offered continuous electron pathways and mechanical integrity. The synergistic effect of CMGNR hybrids on the supercapacitor (SC) performance was derived from the hybrid composition of pseudocapacitive RuO2 NPs with the conductive CMGNs as well as from structural features. Consequently, the CMGNR-SCs showed a specific capacitance as high as 160 F g-1, three-fold higher than that of conventional graphene SCs, and a capacitance retention of >95% of the maximum value even after severe bending and 1000 charge-discharge tests due to the structural and compositional features.Hierarchical structures of hybrid materials with the controlled compositions have been shown to offer a breakthrough for energy storage and conversion. Here, we report the integrative assembly of chemically modified graphene (CMG) building blocks into hierarchical complex structures with the hybrid composition for high performance flexible pseudocapacitors. The formation mechanism of hierarchical CMG/Nafion/RuO2 (CMGNR) microspheres, which is triggered by the cooperative interplay during the in situ synthesis of RuO2 nanoparticles (NPs), was extensively investigated. In particular, the hierarchical CMGNR microspheres consisting of the aggregates of CMG/Nafion (CMGN) nanosheets and RuO2 NPs provided large surface area and facile ion accessibility to storage sites, while the interconnected nanosheets offered continuous electron pathways and mechanical integrity. The synergistic effect of CMGNR hybrids on the supercapacitor (SC) performance was derived from the hybrid composition of pseudocapacitive RuO2 NPs with the conductive CMGNs as well as from structural features. Consequently, the CMGNR-SCs showed a specific capacitance as high as 160 F g-1, three-fold higher than that of conventional graphene SCs, and a capacitance retention of >95% of the maximum value even after severe bending and 1000 charge-discharge tests due to the structural and compositional features. Electronic supplementary information (ESI) available: Electrodeposition procedure, TEM, SEM, and AFM images, XPS, FT-IR, and XRD spectra, mechanical strain-stress curve, textural and conductive properties, and impedance spectroscopy. See DOI: 10.1039/c3nr33674c

Reflexive aerostructures: increased vehicle survivability

NASA Astrophysics Data System (ADS)

Margraf, Thomas W.; Hemmelgarn, Christopher D.; Barnell, Thomas J.; Franklin, Mark A.

2007-04-01

Aerospace systems stand to benefit significantly from the advancement of reflexive aerostructure technologies for increased vehicle survivability. Cornerstone Research Group Inc. (CRG) is developing lightweight, healable composite systems for use as primary load-bearing aircraft components. The reflexive system is comprised of piezoelectric structural health monitoring systems, localized thermal activation systems, and lightweight, healable composite structures. The reflexive system is designed to mimic the involuntary human response to damage. Upon impact, the structural health monitoring system will identify the location and magnitude of the damage, sending a signal to a discrete thermal activation control system to resistively heat the shape memory polymer (SMP) matrix composite above activation temperature, resulting in localized shape recovery and healing of the damaged areas. CRG has demonstrated SMP composites that can recover 90 percent of flexural yield stress and modulus after postfailure healing. During the development, CRG has overcome issues of discrete activation, structural health monitoring integration, and healable resin systems. This paper will address the challenges associated with development of a reflexive aerostructure, including integration of structural health monitoring, discrete healing, and healable shape memory resin systems.

Graphite/Polyimide Composites. [conference on Composites for Advanced Space Transportation Systems

NASA Technical Reports Server (NTRS)

Dexter, H. B. (Editor); Davis, J. G., Jr. (Editor)

1979-01-01

Technology developed under the Composites for Advanced Space Transportation System Project is reported. Specific topics covered include fabrication, adhesives, test methods, structural integrity, design and analysis, advanced technology developments, high temperature polymer research, and the state of the art of graphite/polyimide composites.

Development and implementation of an automatic integration system for fibre optic sensors in the braiding process with the objective of online-monitoring of composite structures

NASA Astrophysics Data System (ADS)

Hufenbach, W.; Gude, M.; Czulak, A.; Kretschmann, Martin

2014-04-01

Increasing economic, political and ecological pressure leads to steadily rising percentage of modern processing and manufacturing processes for fibre reinforced polymers in industrial batch production. Component weights beneath a level achievable by classic construction materials, which lead to a reduced energy and cost balance during product lifetime, justify the higher fabrication costs. However, complex quality control and failure prediction slow down the substitution by composite materials. High-resolution fibre-optic sensors (FOS), due their low diameter, high measuring point density and simple handling, show a high applicability potential for an automated sensor-integration in manufacturing processes, and therefore the online monitoring of composite products manufactured in industrial scale. Integrated sensors can be used to monitor manufacturing processes, part tests as well as the component structure during product life cycle, which simplifies allows quality control during production and the optimization of single manufacturing processes.[1;2] Furthermore, detailed failure analyses lead to a enhanced understanding of failure processes appearing in composite materials. This leads to a lower wastrel number and products of a higher value and longer product life cycle, whereby costs, material and energy are saved. This work shows an automation approach for FOS-integration in the braiding process. For that purpose a braiding wheel has been supplemented with an appliance for automatic sensor application, which has been used to manufacture preforms of high-pressure composite vessels with FOS-networks integrated between the fibre layers. All following manufacturing processes (vacuum infiltration, curing) and component tests (quasi-static pressure test, programmed delamination) were monitored with the help of the integrated sensor networks. Keywords: SHM, high-pressure composite vessel, braiding, automated sensor integration, pressure test, quality control, optic-fibre sensors, Rayleigh, Luna Technologies

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.

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.

Laser Direct Writing and Selective Metallization of Metallic Circuits for Integrated Wireless Devices.

PubMed

Cai, Jinguang; Lv, Chao; Watanabe, Akira

2018-01-10

Portable and wearable devices have attracted wide research attention due to their intimate relations with human daily life. As basic structures in the devices, the preparation of high-conductive metallic circuits or micro-circuits on flexible substrates should be facile, cost-effective, and easily integrated with other electronic units. In this work, high-conductive carbon/Ni composite structures were prepared by using a facile laser direct writing method, followed by an electroless Ni plating process, which exhibit a 3-order lower sheet resistance of less than 0.1 ohm/sq compared to original structures before plating, showing the potential for practical use. The carbon/Ni composite structures exhibited a certain flexibility and excellent anti-scratch property due to the tight deposition of Ni layers on carbon surfaces. On the basis of this approach, a wireless charging and storage device on a polyimide film was demonstrated by integrating an outer rectangle carbon/Ni composite coil for harvesting electromagnetic waves and an inner carbon micro-supercapacitor for energy storage, which can be fast charged wirelessly by a commercial wireless charger. Furthermore, a near-field communication (NFC) tag was prepared by combining a carbon/Ni composite coil for harvesting signals and a commercial IC chip for data storage, which can be used as an NFC tag for practical application.

On the Problems of Cracking and the Question of Structural Integrity of Engineering Composite Materials

NASA Astrophysics Data System (ADS)

Beaumont, Peter W. R.

2014-02-01

Predicting precisely where a crack will develop in a material under stress and exactly when in time catastrophic fracture of the component will occur is one the oldest unsolved mysteries in the design and building of large engineering structures. Where human life depends upon engineering ingenuity, the burden of testing to prove a "fracture safe design" is immense. For example, when human life depends upon structural integrity as an essential design requirement, it takes ten thousand material test coupons per composite laminate configuration to evaluate an airframe plus loading to ultimate failure tails, wing boxes, and fuselages to achieve a commercial aircraft airworthiness certification. Fitness considerations for long-life implementation of aerospace composites include understanding phenomena such as impact, fatigue, creep, and stress corrosion cracking that affect reliability, life expectancy, and durability of structure. Structural integrity analysis treats the design, the materials used, and figures out how best components and parts can be joined. Furthermore, SI takes into account service duty. However, there are conflicting aims in the complete design process of designing simultaneously for high efficiency and safety assurance throughout an economically viable lifetime with an acceptable level of risk.

Structural Analysis of Composite Flywheels: an Integrated NDE and FEM Approach

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Baaklini, George; Trudell, Jeffrey

2001-01-01

A structural assessment by integrating finite-element methods (FEM) and a nondestructive evaluation (NDE) of two flywheel rotor assemblies is presented. Composite rotor A is pancake-like with a solid hub design, and composite rotor B is cylindrical with a hollow hub design. Detailed analyses under combined centrifugal and interference-fit loading are performed. Two- and three-dimensional stress analyses and two-dimensional fracture mechanics analyses are conducted. A comparison of the structural analysis results obtained with those extracted via NDE findings is reported. Contact effects due to press-fit conditions are evaluated. Stress results generated from the finite-element analyses were corroborated with the analytical solution. Cracks due to rotational loading up to 48,000 rpm for rotor A and 34,000 rpm for rotor B were successfully imaged with NDE and predicted with FEM and fracture mechanics analyses. A procedure that extends current structural analysis to a life prediction tool is also defined.

Overview Of Structural Behavior and Occupant Responses from Crash Test of a Composite Airplane

NASA Technical Reports Server (NTRS)

Jones, Lisa E.; Carden, Huey D.

1995-01-01

As part of NASA's composite structures crash dynamics research, a general aviation aircraft with composite wing, fuselage and empennage (but with metal subfloor structure) was crash tested at the NASA Langley Research Center Impact Research Facility. The test was conducted to determine composite aircraft structural behavior for crash loading conditions and to provide a baseline for a similar aircraft test with a modified subfloor. Structural integrity and cabin volume were maintained. Lumbar loads for dummy occupants in energy absorbing seats wer substantially lower than those in standard aircraft seats; however, loads in the standard seats were much higher that those recorded under similar conditions for an all-metallic aircraft.

Advanced composite vertical fin for L-1011 aircraft

NASA Technical Reports Server (NTRS)

Jackson, A. C.

1984-01-01

The structural box of the L-1011 vertical fin was redesigned using advanced composite materials. The box was fabricated and ground tested to verify the structural integrity. This report summarizes the complete program starting with the design and analysis and proceeds through the process development ancillary test program production readiness verification testing, fabrication of the full-scale fin boxes and the full-scale ground testing. The program showed that advanced composites can economically and effectively be used in the design and fabrication of medium primary structures for commercial aircraft. Static-strength variability was demonstrated to be comparable to metal structures and the long term durability of advanced composite components was demonstrated.

Integral Ring Carbon-Carbon Piston

NASA Technical Reports Server (NTRS)

Northam, G. Burton (Inventor)

1999-01-01

An improved structure for a reciprocating internal combustion engine or compressor piston fabricate from carbon-carbon composite materials is disclosed. An integral ring carbon-carbon composite piston, disclosed herein, reduces the need for piston rings and for small clearances by providing a small flexible, integral component around the piston that allows for variation in clearance due to manufacturing tolerances, distortion due to pressure and thermal loads, and variations in thermal expansion differences between the piston and cylinder liner.

Biomimetic strategies for engineering composite tissues.

PubMed

Lee, Nancy; Robinson, Jennifer; Lu, Helen

2016-08-01

The formation of multiple tissue types and their integration into composite tissue units presents a frontier challenge in regenerative engineering. Tissue-tissue synchrony is crucial in providing structural support for internal organs and enabling daily activities. This review highlights the state-of-the-art in composite tissue scaffold design, and explores how biomimicry can be strategically applied to avoid over-engineering the scaffold. Given the complexity of biological tissues, determining the most relevant parameters for recapitulating native structure-function relationships through strategic biomimicry will reduce the burden for clinical translation. It is anticipated that these exciting efforts in composite tissue engineering will enable integrative and functional repair of common soft tissue injuries and lay the foundation for total joint or limb regeneration. Copyright © 2016 Elsevier Ltd. All rights reserved.

Resin selection criteria for tough composite structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Smith, G. T.

1983-01-01

Resin selection criteria are derived using a structured methodology consisting of an upward integrated mechanistic theory and its inverse (top-down structured theory). These criteria are expressed in a "criteria selection space" which are used to identify resin bulk properties for improved composite "toughness". The resin selection criteria correlate with a variety of experimental data including laminate strength, elevated temperature effects and impact resistance.

Structural Integrity of Gas-Filled Composite Overwrapped Pressure Vessels Subjected to Orbital Debris Impact

NASA Astrophysics Data System (ADS)

Telichev, Igor; Cherniaev, Aleksandr

Gas-filled pressure vessels are extensively used in spacecraft onboard systems. During operation on the orbit they exposed to the space debris environment. Due to high energies they contain, pressure vessels have been recognized as the most critical spacecraft components requiring protection from orbital debris impact. Major type of pressurized containers currently used in spacecraft onboard systems is composite overwrapped pressure vessels (COPVs) manufactured by filament winding. In the present work we analyze the structural integrity of vessels of this kind in case of orbital debris impact at velocities ranging from 2 to 10 km/s. Influence of such parameters as projectile energy, shielding standoff, internal pressure and filament winding pattern on COPVs structural integrity has been investigated by means of numerical and physical experiments.

Radiation-Shielding Polymer/Soil Composites

NASA Technical Reports Server (NTRS)

Sen, Subhayu

2007-01-01

It has been proposed to fabricate polymer/ soil composites primarily from extraterrestrial resources, using relatively low-energy processes, with the original intended application being that habitat structures constructed from such composites would have sufficient structural integrity and also provide adequate radiation shielding for humans and sensitive electronic equipment against the radiation environment on the Moon and Mars. The proposal is a response to the fact that it would be much less expensive to fabricate such structures in situ as opposed to transporting them from Earth.

Nanocomposites in Multifuntional Structures for Spacecraft Platforms

NASA Astrophysics Data System (ADS)

Marcos, J.; Mendizabal, M.; Elizetxea, C.; Florez, S.; Atxaga, G.; Del Olmo, E.

2012-07-01

The integration of functionalities as electrical, thermal, power or radiation shielding inside carrier electronic boxes, solar panels or platform structures allows reducing weight, volume, and harness for spacecraft. The multifunctional structures represent an advanced design approach for space components and subsystems. The development of such multifunctional structures aims the re-engineering traditional metallic structures by composites in space, which request to provide specific solutions for thermal conductivity, EMI-EMC, radiation shielding and integration. The use of nanomaterials as CNF and nano-adds to reinforce composite structures allows obtaining local solutions for improving electrical conductivity, thermal conductivity and radiation shielding. The paper summarises the results obtained in of three investigations conducted by Tecnalia based on carbon nanofillers for improving electro-thermal characteristics of spacecraft platform, electronic substrates and electronics boxes respectively.

Impact and vibration detection in composite materials by using intermodal interference in multimode optical fibers

NASA Astrophysics Data System (ADS)

Malki, Abdelrafik; Gafsi, Rachid; Michel, Laurent; Labarrère, Michel; Lecoy, Pierre

1996-09-01

An optical fiber sensor based on the intermodal interference principle is integrated in a composite material to detect impacts and vibrations. Six fibers are integrated at the top of a carbon/epoxy composite panel so as to form a grid into the structure. Spectral and temporal responses to impacts and acoustic vibrations of the sensor are compared with a piezoelectric accelerometer. The tests proved the facility of integration and the high sensitivity of the device. The location of impacts is performed with this arrangement by measuring the arrival times of the front waves to the fibers.

High-Capacity, High-Voltage Composite Oxide Cathode Materials

NASA Technical Reports Server (NTRS)

Hagh, Nader M.

2015-01-01

This SBIR project integrates theoretical and experimental work to enable a new generation of high-capacity, high-voltage cathode materials that will lead to high-performance, robust energy storage systems. At low operating temperatures, commercially available electrode materials for lithium-ion (Li-ion) batteries do not meet energy and power requirements for NASA's planned exploration activities. NEI Corporation, in partnership with the University of California, San Diego, has developed layered composite cathode materials that increase power and energy densities at temperatures as low as 0 degC and considerably reduce the overall volume and weight of battery packs. In Phase I of the project, through innovations in the structure and morphology of composite electrode particles, the partners successfully demonstrated an energy density exceeding 1,000 Wh/kg at 4 V at room temperature. In Phase II, the team enhanced the kinetics of Li-ion transport and electronic conductivity at 0 degC. An important feature of the composite cathode is that it has at least two components that are structurally integrated. The layered material is electrochemically inactive; however, upon structural integration with a spinel material, the layered material can be electrochemically activated and deliver a large amount of energy with stable cycling.

Microstructured Optical Fiber Sensors Embedded in a Laminate Composite for Smart Material Applications

PubMed Central

Sonnenfeld, Camille; Sulejmani, Sanne; Geernaert, Thomas; Eve, Sophie; Lammens, Nicolas; Luyckx, Geert; Voet, Eli; Degrieck, Joris; Urbanczyk, Waclaw; Mergo, Pawel; Becker, Martin; Bartelt, Hartmut; Berghmans, Francis; Thienpont, Hugo

2011-01-01

Fiber Bragg gratings written in highly birefringent microstructured optical fiber with a dedicated design are embedded in a composite fiber-reinforced polymer. The Bragg peak wavelength shifts are measured under controlled axial and transversal strain and during thermal cycling of the composite sample. We obtain a sensitivity to transversal strain that exceeds values reported earlier in literature by one order of magnitude. Our results evidence the relevance of using microstructured optical fibers for structural integrity monitoring of composite material structures. PMID:22163755

Structural materials for NASP

NASA Astrophysics Data System (ADS)

Ronald, Terence M. F.

1991-12-01

Structural materials for the NASP X-30 experimental vehicle are briefly reviewed including titanium alloys, titanium-based metal-matrix composites, carbon-carbon composites, ceramic-matrix composites, and copper-matrix composites. Areas of application of these materials include the airframe where these materials would be used as lightweight skin panels for honeycomb-core, truss-core, or integrally stiffened thin sheet configuration; and the engine, where they would be used in the hot gas path of the ramjet/scramjet, and in the inlet and nozzle areas.

Electroactive nanoparticle directed assembly of functionalized graphene nanosheets into hierarchical structures with hybrid compositions for flexible supercapacitors.

PubMed

Choi, Bong Gill; Huh, Yun Suk; Hong, Won Hi; Erickson, David; Park, Ho Seok

2013-05-07

Hierarchical structures of hybrid materials with the controlled compositions have been shown to offer a breakthrough for energy storage and conversion. Here, we report the integrative assembly of chemically modified graphene (CMG) building blocks into hierarchical complex structures with the hybrid composition for high performance flexible pseudocapacitors. The formation mechanism of hierarchical CMG/Nafion/RuO2 (CMGNR) microspheres, which is triggered by the cooperative interplay during the in situ synthesis of RuO2 nanoparticles (NPs), was extensively investigated. In particular, the hierarchical CMGNR microspheres consisting of the aggregates of CMG/Nafion (CMGN) nanosheets and RuO2 NPs provided large surface area and facile ion accessibility to storage sites, while the interconnected nanosheets offered continuous electron pathways and mechanical integrity. The synergistic effect of CMGNR hybrids on the supercapacitor (SC) performance was derived from the hybrid composition of pseudocapacitive RuO2 NPs with the conductive CMGNs as well as from structural features. Consequently, the CMGNR-SCs showed a specific capacitance as high as 160 F g(-1), three-fold higher than that of conventional graphene SCs, and a capacitance retention of >95% of the maximum value even after severe bending and 1000 charge-discharge tests due to the structural and compositional features.

Integrated thick-film nanostructures based on spinel ceramics

PubMed Central

2014-01-01

Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

Micromechanics Fatigue Damage Analysis Modeling for Fabric Reinforced Ceramic Matrix Composites

NASA Technical Reports Server (NTRS)

Min, J. B.; Xue, D.; Shi, Y.

2013-01-01

A micromechanics analysis modeling method was developed to analyze the damage progression and fatigue failure of fabric reinforced composite structures, especially for the brittle ceramic matrix material composites. A repeating unit cell concept of fabric reinforced composites was used to represent the global composite structure. The thermal and mechanical properties of the repeating unit cell were considered as the same as those of the global composite structure. The three-phase micromechanics, the shear-lag, and the continuum fracture mechanics models were integrated with a statistical model in the repeating unit cell to predict the progressive damages and fatigue life of the composite structures. The global structure failure was defined as the loss of loading capability of the repeating unit cell, which depends on the stiffness reduction due to material slice failures and nonlinear material properties in the repeating unit cell. The present methodology is demonstrated with the analysis results evaluated through the experimental test performed with carbon fiber reinforced silicon carbide matrix plain weave composite specimens.

Using composite sinusoidal patterns in structured-illumination reflectance imaging (SIRI) for enhanced detection of defects in food

USDA-ARS?s Scientific Manuscript database

This study presented a first exploration of using composite sinusoidal patterns that integrated two and three spatial frequencies of interest, in structured-illumination reflectance imaging (SIRI) for enhanced detection of defects in food (e.g., bruises in apples). Three methods based on Fourier tra...

Smart Composite Overwrapped Pressure Vessel - Integrated Structural Health Monitoring System to Meet Space Exploration and International Space Station Mission Assurance Needs

NASA Technical Reports Server (NTRS)

Saulsberry, Regor; Nichols, Charles; Waller, Jess

2012-01-01

Currently there are no integrated NDE methods for baselining and monitoring defect levels in fleet for Composite Overwrapped Pressure Vessels (COPVs) or related fracture critical composites, or for performing life-cycle maintenance inspections either in a traditional remove-and-inspect mode or in a more modern in situ inspection structural health monitoring (SHM) mode. Implicit in SHM and autonomous inspection is the existence of quantitative accept-reject criteria. To be effective, these criteria must correlate with levels of damage known to cause composite failure. Furthermore, implicit in SHM is the existence of effective remote sensing hardware and automated techniques and algorithms for interpretation of SHM data. SHM of facture critical composite structures, especially high pressure COPVs, is critical to the success of nearly every future NASA space exploration program as well as life extension of the International Space Station. It has been clearly stated that future NASA missions may not be successful without SHM [1]. Otherwise, crews will be busy addressing subsystem health issues and not focusing on the real NASA mission

The effects of embedded piezoelectric fiber composite sensors on the structural integrity of glass-fiber-epoxy composite laminate

NASA Astrophysics Data System (ADS)

Konka, Hari P.; Wahab, M. A.; Lian, K.

2012-01-01

Piezoelectric fiber composite sensors (PFCSs) made from micro-sized lead zirconate titanate (PZT) fibers have many advantages over the traditional bulk PZT sensors for embedded sensor applications. PFCSs as embedded sensors will be an ideal choice to continuously monitor the stress/strain levels and health conditions of composite structures. PFCSs are highly flexible, easily embeddable, have high compatibility with composite structures, and also provides manufacturing flexibility. This research is focused on examining the effects of embedding PFCS sensors (macro-fiber composite (MFC) and piezoelectric fiber composite (PFC)) on the structural integrity of glass-fiber-epoxy composite laminates. The strengths of composite materials with embedded PFCSs and conventional PZT sensors were compared, and the advantages of PFCS sensors over PZTs were demonstrated. Initially a numerical simulation study is performed to understand the local stress/strain field near the embedded sensor region inside a composite specimen. High stress concentration regions were observed near the embedded sensor corner edge. Using PFCS leads to a reduction of 56% in longitudinal stress concentration and 38% in transverse stress concentration, when compared to using the conventional PZTs as embedded sensors. In-plane tensile, in-plane tension-tension fatigue, and short beam strength tests are performed to evaluate the strengths/behavior of the composite specimens containing embedded PFCS. From the tensile test it is observed that embedding PFCS and PZT sensors in the composite structures leads to a reduction in ultimate strength by 3 and 6% respectively. From the fatigue test results it is concluded that both embedded PFCS and PZT sensors do not have a significant effect on the fatigue behavior of the composite specimens. From the short beam strength test it is found that embedding PFCS and PZT sensors leads to a reduction in shear strength by 7 and 15% respectively. Overall the pure PZT sensors seem to have low compatibility with composites when compared to PFCSs.

A Review of Crashworthiness of Composite Aircraft Structures

DTIC Science & Technology

1990-02-01

proprietary, or other reaons . Details on the availability of these publications may be obtained from: Graphics Section, National Research Council Canada...bottoming out, good energy-absorbing and load-limiting ability, good post-crushing structural integrity and no significant load rate sensitivity. In a... good energy absorption capability under compressive loadings. However, under tensile or bending conditions, structural integrity may be lost at initial

Cryogenic-Compatible Winchester Connector Mount and Retaining System for Composite Tubes

NASA Technical Reports Server (NTRS)

Pontius, James; McGuffey, Douglas

2011-01-01

A connector retainer and mounting system has been designed to replace screw-mounting of Winchester connectors. Countersunk screws are normally used to secure connectors to structures, and to keep them from coming apart. These screws are normally put into threaded or through-holes in metallic structures. This unique retainer is designed such that integral posts keep the connector halves retained, and a groove permits a cable tie to be fastened around the retainer and composite tube, thus securing the connector to the structure. The system is compatible for use on cryogenic (and conventional) bonded composite tube assemblies. Screws and tapped/through-holes needed to retain and mount Winchester connectors cannot be used on blind-access composite tubes. This system allows for rapid installation, removal, low-molecular-outgassing materials, and particulate-free installation and removal. Installation and/or changes late in the integration, and test flow with limited access in a cleanroom environment are possible. No sanding or bonding is needed.

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.

Optimization of sensor introduction into laminated composite materials

NASA Astrophysics Data System (ADS)

Schaaf, Kristin; Nemat-Nasser, Sia

2008-03-01

This work seeks to extend the functionality of the composite material beyond that of simply load-bearing and to enable in situ sensing, without compromising the structural integrity of the host composite material. Essential to the application of smart composites is the issue of the mechanical coupling of the sensor to the host material. Here we present various methods of embedding sensors within the host composite material. In this study, quasi-static three-point bending (short beam) and fatigue three-point bending (short beam) tests are conducted in order to characterize the effects of introducing the sensors into the host composite material. The sensors that are examined include three types of polyvinylidene fluoride (PVDF) thin film sensors: silver ink with a protective coating of urethane, silver ink without a protective coating, and nickel-copper alloy without a protective coating. The methods of sensor integration include placement at the midplane between the layers of prepreg material as well as a sandwich configuration in which a PVDF thin film sensor is placed between the first and second and nineteenth and twentieth layers of prepreg. Each PVDF sensor is continuous and occupies the entire layer, lying in the plane normal to the thickness direction in laminated composites. The work described here is part of an ongoing effort to understand the structural effects of integrating microsensor networks into a host composite material.

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.

The effects of gravity level during directional solidification on the microstructure of hypermonotectic Al-In-Sn alloys

NASA Technical Reports Server (NTRS)

Curreri, P. A.; Kaukler, W. F.

1986-01-01

Five hypermonotectic Al-In-Sn compositions were directionally solidified in a Bridgman-type furnace at normal gravity and during aircraft low-gravity maneuvers. The tendency of the Al-30In alloy to form an indium-rich band at the start of unidirectional growth (SUG) made it difficult to study the integration of L sub 2 into the solidification interface. Hypermonotectic compositions closer to monotectic slightly hypermonotectic caused only a partial band on L sub 2 to form at SUG and allowed the study of such variables as gravity, composition, and monotectic dome height on integration of excess L sub 2 into the solid plus L sub 2 interface. It was found that formation of aligned composite structures for the Al-In-Sn system is not only a function of G and R but also of the degree to which the composition varies from monotectic. Most of the aligned fibrous structures formed from hypermonotectic Al-In-Sn had spacings that were of the order of irregular fibrous structures reported for on monotectic Al-In-Sn. The spacings for the large fibers and aligned globules found for ground and low-gravity processed Al-In-18-Sn-22, respectively, were significantly larger than the others measured and were of the order expected for cell spacings under the growth conditions utilized. It was found that the integration into the solidification front of excess L sub 2 in low gravity was a function of the Sn composition of the alloy.

Thermoviscoplastic nonlinear constitutive relationships for structural analysis of high temperature metal matrix composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Hopkins, D. A.

1985-01-01

A set of thermoviscoplastic nonlinear constitutive relationships (1VP-NCR) is presented. The set was developed for application to high temperature metal matrix composites (HT-MMC) and is applicable to thermal and mechanical properties. Formulation of the TVP-NCR is based at the micromechanics level. The TVP-NCR are of simple form and readily integrated into nonlinear composite structural analysis. It is shown that the set of TVP-NCR is computationally effective. The set directly predicts complex materials behavior at all levels of the composite simulation, from the constituent materials, through the several levels of composite mechanics, and up to the global response of complex HT-MMC structural components.

Integration of High-Resolution Laser Displacement Sensors and 3D Printing for Structural Health Monitoring

PubMed Central

Chang, Shu-Wei; Kuo, Shih-Yu; Huang, Ting-Hsuan

2017-01-01

This paper presents a novel experimental design for complex structural health monitoring (SHM) studies achieved by integrating 3D printing technologies, high-resolution laser displacement sensors, and multiscale entropy SHM theory. A seven-story structure with a variety of composite bracing systems was constructed using a dual-material 3D printer. A wireless Bluetooth vibration speaker was used to excite the ground floor of the structure, and high-resolution laser displacement sensors (1-μm resolution) were used to monitor the displacement history on different floors. Our results showed that the multiscale entropy SHM method could detect damage on the 3D-printed structures. The results of this study demonstrate that integrating 3D printing technologies and high-resolution laser displacement sensors enables the design of cheap, fast processing, complex, small-scale civil structures for future SHM studies. The novel experimental design proposed in this study provides a suitable platform for investigating the validity and sensitivity of SHM in different composite structures and damage conditions for real life applications in the future. PMID:29271937

Integration of High-Resolution Laser Displacement Sensors and 3D Printing for Structural Health Monitoring.

PubMed

Chang, Shu-Wei; Lin, Tzu-Kang; Kuo, Shih-Yu; Huang, Ting-Hsuan

2017-12-22

This paper presents a novel experimental design for complex structural health monitoring (SHM) studies achieved by integrating 3D printing technologies, high-resolution laser displacement sensors, and multiscale entropy SHM theory. A seven-story structure with a variety of composite bracing systems was constructed using a dual-material 3D printer. A wireless Bluetooth vibration speaker was used to excite the ground floor of the structure, and high-resolution laser displacement sensors (1-μm resolution) were used to monitor the displacement history on different floors. Our results showed that the multiscale entropy SHM method could detect damage on the 3D-printed structures. The results of this study demonstrate that integrating 3D printing technologies and high-resolution laser displacement sensors enables the design of cheap, fast processing, complex, small-scale civil structures for future SHM studies. The novel experimental design proposed in this study provides a suitable platform for investigating the validity and sensitivity of SHM in different composite structures and damage conditions for real life applications in the future.

Structural vibration-based damage classification of delaminated smart composite laminates

NASA Astrophysics Data System (ADS)

Khan, Asif; Kim, Heung Soo; Sohn, Jung Woo

2018-03-01

Separation along the interfaces of layers (delamination) is a principal mode of failure in laminated composites and its detection is of prime importance for structural integrity of composite materials. In this work, structural vibration response is employed to detect and classify delaminations in piezo-bonded laminated composites. Improved layerwise theory and finite element method are adopted to develop the electromechanically coupled governing equation of a smart composite laminate with and without delaminations. Transient responses of the healthy and damaged structures are obtained through a surface bonded piezoelectric sensor by solving the governing equation in the time domain. Wavelet packet transform (WPT) and linear discriminant analysis (LDA) are employed to extract discriminative features from the structural vibration response of the healthy and delaminated structures. Dendrogram-based support vector machine (DSVM) is used to classify the discriminative features. The confusion matrix of the classification algorithm provided physically consistent results.

Integrated Composite Analyzer (ICAN): Users and programmers manual

NASA Technical Reports Server (NTRS)

Murthy, P. L. N.; Chamis, C. C.

1986-01-01

The use of and relevant equations programmed in a computer code designed to carry out a comprehensive linear analysis of multilayered fiber composites is described. The analysis contains the essential features required to effectively design structural components made from fiber composites. The inputs to the code are constituent material properties, factors reflecting the fabrication process, and composite geometry. The code performs micromechanics, macromechanics, and laminate analysis, including the hygrothermal response of fiber composites. The code outputs are the various ply and composite properties, composite structural response, and composite stress analysis results with details on failure. The code is in Fortran IV and can be used efficiently as a package in complex structural analysis programs. The input-output format is described extensively through the use of a sample problem. The program listing is also included. The code manual consists of two parts.

Material characterization of active fiber composites for integral twist-actuated rotor blade application

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

2004-10-01

The primary objective of this work was to perform material characterization of the active fiber composite (AFC) actuator system for the Boeing active material rotor (AMR) blade application. The purpose of the AMR was to demonstrate active vibration control in helicopters through integral twist-actuation of the blade. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to enhance actuation performance. These conformable actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural control. Therefore, extensive electromechanical material characterization was required to evaluate AFCs both as actuators and as structural components of the blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included nominal actuation tests, stress-strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing procedure developed to evaluate the relevant properties of the AFCs for structural application. The material characterization tests provided an invaluable insight into the behavior of the AFCs under various electromechanical conditions. The results from this comprehensive material characterization of the AFC actuator system supported the design and operation of the AMR blades scheduled for wind tunnel tests.

Design and Manufacture of Structurally Efficient Tapered Struts

NASA Technical Reports Server (NTRS)

Brewster, Jebediah W.

2009-01-01

Composite materials offer the potential of weight savings for numerous spacecraft and aircraft applications. A composite strut is just one integral part of the node-to-node system and the optimization of the shut and node assembly is needed to take full advantage of the benefit of composites materials. Lockheed Martin designed and manufactured a very light weight one piece composite tapered strut that is fully representative of a full scale flight article. In addition, the team designed and built a prototype of the node and end fitting system that will effectively integrate and work with the full scale flight articles.

Analysis of metal-matrix composite structures. I - Micromechanics constitutive theory. II - Laminate analyses

NASA Technical Reports Server (NTRS)

Arenburg, R. T.; Reddy, J. N.

1991-01-01

The micromechanical constitutive theory is used to examine the nonlinear behavior of continuous-fiber-reinforced metal-matrix composite structures. Effective lamina constitutive relations based on the Abouli micromechanics theory are presented. The inelastic matrix behavior is modeled by the unified viscoplasticity theory of Bodner and Partom. The laminate constitutive relations are incorporated into a first-order deformation plate theory. The resulting boundary value problem is solved by utilizing the finite element method. Attention is also given to computational aspects of the numerical solution, including the temporal integration of the inelastic strains and the spatial integration of bending moments. Numerical results the nonlinear response of metal matrix composites subjected to extensional and bending loads are presented.

Proceedings of the USAF Structural Integrity Program Conference Held in San Antonio, Texas on 2-6 December 1991

DTIC Science & Technology

1992-07-01

NONDESTRUCTIVE INSPECTION Probabilistic Durability Evaluation of Alcoa 7050 Aluminum ............................... 305 Composite Repair of Aircraft Structures... Aluminum J.G. Burns, WLIFIBEC 0900-0930 Composite Repair of Aircraft Structures - The Australian Experience L. Molent, Aeronautical Research Laboratory...fatigue test articles consisted of a of 5 percent from the calculated airframe ratio of 2124-T851 aluminum specimen surrounded by 0.882, to preclude

Post-impact behavior of composite solid rocket motor cases

NASA Technical Reports Server (NTRS)

Highsmith, Alton L.

1992-01-01

In recent years, composite materials have seen increasing use in advanced structural applications because of the significant weight savings they offer when compared to more traditional engineering materials. The higher cost of composites must be offset by the increased performance that results from reduced structural weight if these new materials are to be used effectively. At present, there is considerable interest in fabricating solid rocket motor cases out of composite materials, and capitalizing on the reduced structural weight to increase rocket performance. However, one of the difficulties that arises when composite materials are used is that composites can develop significant amounts of internal damage during low velocity impacts. Such low velocity impacts may be encountered in routine handling of a structural component like a rocket motor case. The ability to assess the reduction in structural integrity of composite motor cases that experience accidental impacts is essential if composite rocket motor cases are to be certified for manned flight. The study described herein was an initial investigation of damage development and reduction of tensile strength in an idealized composite subjected to low velocity impacts.

Integrated NDE and FEM characterization of composite rotors

NASA Astrophysics Data System (ADS)

Abdul-Aziz, Ali; Baaklini, George Y.; Trudell, Jeffrey J.

2001-08-01

A structural assessment by integrating finite-element methods (FEM) and a nondestructive evaluation (NDE) of two flywheel rotor assemblies is presented. Composite rotor A is pancake like with a solid hub design, and composite rotor B is cylindrical with a hollow hub design. Detailed analyses under combined centrifugal and interference-fit loading are performed. Two- and three-dimensional stress analyses and two-dimensional fracture mechanics analyses are conducted. A comparison of the structural analysis results obtained with those extracted via NDE findings is reported. Contact effects due to press-fit conditions are evaluated. Stress results generated from the finite-element analyses were corroborated with the analytical solution. Cracks due to rotational loading up to 48 000 rpm for rotor A and 34 000 rpm for rotor B were successfully imaged with NDE and predicted with FEM and fracture mechanics analyses. A procedure that extends current structural analysis to a life prediction tool is also defined.

An Integrated NDE and FEM Characterization of Composite Rotors

NASA Technical Reports Server (NTRS)

Abdul-Aziz, Ali; Baaklini, George Y.; Trudell, Jeffrey J.

2000-01-01

A structural assessment by integrating finite-element methods (FEM) and a nondestructive evaluation (NDE) of two flywheel rotor assemblies is presented. Composite rotor A is pancake like with a solid hub design, and composite rotor B is cylindrical with a hollow hub design. Detailed analyses under combined centrifugal and interference-fit loading are performed. Two- and three-dimensional stress analyses and two-dimensional fracture mechanics analyses are conducted. A comparison of the structural analysis results obtained with those extracted via NDE findings is reported. Contact effects due to press-fit conditions are evaluated. Stress results generated from the finite-element analyses were corroborated with the analytical solution. Cracks due to rotational loading up to 49 000 rpm for rotor A and 34 000 rpm for rotor B were successfully imaged with NDE and predicted with FEM and fracture mechanics analyses. A procedure that extends current structural analysis to a life prediction tool is also defined.

Fiber Optic Sensors for Health Monitoring of Morphing Aircraft

NASA Technical Reports Server (NTRS)

Brown, Timothy; Wood, Karen; Childers, Brooks; Cano, Roberto; Jensen, Brian; Rogowski, Robert

2001-01-01

Fiber optic sensors are being developed for health monitoring of future aircraft. Aircraft health monitoring involves the use of strain, temperature, vibration and chemical sensors. These sensors will measure load and vibration signatures that will be used to infer structural integrity. Sine the aircraft morphing program assumes that future aircraft will be aerodynamically reconfigurable there is also a requirement for pressure, flow and shape sensors. In some cases a single fiber may be used for measuring several different parameters. The objective of the current program is to develop techniques for using optical fibers to monitor composite cure in real time during manufacture and to monitor in-service structural integrity of the composite structure. Graphite-epoxy panels were fabricated with integrated optical fibers of various types. The panels were mechanically and thermally tested to evaluate composite strength and sensor durability. Finally the performance of the fiber optic sensors was determined. Experimental results are presented evaluating the performance of embedded and surface mounted optical fibers for measuring strain, temperature and chemical composition. The performance of the fiber optic sensors was determined by direct comparison with results from more conventional instrumentation. The facilities for fabricating optical fiber and associated sensors and methods of demodulating Bragg gratings for strain measurement will be described.

Composite transport wing technology development: Design development tests and advanced structural concepts

NASA Technical Reports Server (NTRS)

Griffin, Charles F.; Harvill, William E.

1988-01-01

Numerous design concepts, materials, and manufacturing methods were investigated for the covers and spars of a transport box wing. Cover panels and spar segments were fabricated and tested to verify the structural integrity of design concepts and fabrication techniques. Compression tests on stiffened panels demonstrated the ability of graphite/epoxy wing upper cover designs to achieve a 35 percent weight savings compared to the aluminum baseline. The impact damage tolerance of the designs and materials used for these panels limits the allowable compression strain and therefore the maximum achievable weight savings. Bending and shear tests on various spar designs verified an average weight savings of 37 percent compared to the aluminum baseline. Impact damage to spar webs did not significantly degrade structural performance. Predictions of spar web shear instability correlated well with measured performance. The structural integrity of spars manufactured by filament winding equalled or exceeded those fabricated by hand lay-up. The information obtained will be applied to the design, fabrication, and test of a full-scale section of a wing box. When completed, the tests on the technology integration box beam will demonstrate the structural integrity of an advanced composite wing design which is 25 percent lighter than the metal baseline.

Study of the influence of volume fraction of ceramic inclusions in NiCr-TiC composite with columnar structure on its mechanical behavior

NASA Astrophysics Data System (ADS)

Eremina, Galina M.; Smolin, Alexey Yu.; Shilko, Evgeny V.

2017-12-01

Metal-ceramic materials are characterized by high mechanical and tribological properties. The surface treatment of the composite by an electron beam in inert gas plasma leads to a qualitative and quantitative change in its microstructure as well as to a change in mechanical properties of the components: a columnar structure forms in the modified layer. Different treatment regimes result in different concentrations of inclusions in the surface layer. In this paper, the effect of the volume concentration of inclusions on the integral mechanical properties of a dispersion-strengthened NiCr-TiC composite is studied on the basis of 3D numerical simulation. The results of computer simulation show that the change in concentration significantly affects the integral mechanical characteristics of the composite material as well as the nature of the nucleation and development of damages in it.

Fatigue Damage Monitoring of a Composite Step Lap Joint Using Distributed Optical Fibre Sensors

PubMed Central

Wong, Leslie; Chowdhury, Nabil; Wang, John; Chiu, Wing Kong; Kodikara, Jayantha

2016-01-01

Over the past few decades, there has been a considerable interest in the use of distributed optical fibre sensors (DOFS) for structural health monitoring of composite structures. In aerospace-related work, health monitoring of the adhesive joints of composites has become more significant, as they can suffer from cracking and delamination, which can have a significant impact on the integrity of the joint. In this paper, a swept-wavelength interferometry (SWI) based DOFS technique is used to monitor the fatigue in a flush step lap joint composite structure. The presented results will show the potential application of distributed optical fibre sensor for damage detection, as well as monitoring the fatigue crack growth along the bondline of a step lap joint composite structure. The results confirmed that a distributed optical fibre sensor is able to enhance the detection of localised damage in a structure. PMID:28773496

New properties of a fiber optic sensor in application of a composite fence for critical infrastructure protection

NASA Astrophysics Data System (ADS)

Zyczkowski, M.; Szustakowski, M.; Markowski, P.

2015-09-01

This paper presents a new solution of using the composite fence with a novel fiber optic modalmetric sensor integrated within its structure. The modalmetric sensor is based on changes in a transverse modal field which is generated at the output of a multimode fiber. By a spatial limitation of the transverse modal field observation to its fragment thereof, changes' transformation in the modal distribution into changes of the output signal amplitude is made. Due to a constant analysis of the structure output signal, detection of an external disorder is possible. Integration of optical fibers with the fence structure allows for an accurate reproduction of the fence movement onto the optical fiber by significantly improving sensitivity of the modalmetric fiber sensor structure.

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.

Damping Experiment of Spinning Composite Plates With Embedded Viscoelastic Material

NASA Technical Reports Server (NTRS)

Mehmed, Oral

1998-01-01

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration can be reduced by adding damping to metal and composite blade-disk systems. As part of a joint research effort of the NASA Lewis Research Center and the University of California, San Diego, the use of integral viscoelastic damping treatment to reduce the vibration of rotating composite fan blades was investigated. The objectives of this experiment were to verify the structural integrity of composite plates with viscoelastic material patches embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

SMART Layer and SMART Suitcase for structural health monitoring applications

NASA Astrophysics Data System (ADS)

Lin, Mark; Qing, Xinlin; Kumar, Amrita; Beard, Shawn J.

2001-06-01

Knowledge of integrity of in-service structures can greatly enhance their safety and reliability and lower structural maintenance cost. Current practices limit the extent of real-time knowledge that can be obtained from structures during inspection, are labor-intensive and thereby increase life-cycle costs. Utilization of distributed sensors integrated with the structure is a viable and cost-effective means of monitoring the structure and reducing inspection costs. Acellent Technologies is developing a novel system for actively and passively interrogating the health of a structure through an integrated network of sensors and actuators. Acellent's system comprises of SMART Layers, SMART Suitcase and diagnostic software. The patented SMART Layer is a thin dielectric film with an embedded network of distributed piezoelectric actuators/sensors that can be surface-mounted on metallic structures or embedded inside composite structures. The SMART Suitcase is a portable diagnostic unit designed with multiple sensor/actuator channels to interface with the SMART Layer, generate diagnostic signals from actuators and record measurements from the embedded sensors. With appropriate diagnostic software, Acellent's system can be used for monitoring structural condition and for detecting damage while the structures are in service. This paper enumerates on the SMART Layer and SMART Suitcase and their applicability to composite and metal structures.

James Webb Space Telescope (JWST) Integrated Science Instruments Module (ISIM) Electronics Compartment (IEC) Conformal Shields Composite Bond Structure Qualification Test Method

NASA Technical Reports Server (NTRS)

Yew, Calinda; Stephens, Matt

2015-01-01

The JWST IEC conformal shields are mounted onto a composite frame structure that must undergo qualification testing to satisfy mission assurance requirements. The composite frame segments are bonded together at the joints using epoxy, EA 9394. The development of a test method to verify the integrity of the bonded structure at its operating environment introduces challenges in terms of requirements definition and the attainment of success criteria. Even though protoflight thermal requirements were not achieved, the first attempt in exposing the structure to cryogenic operating conditions in a thermal vacuum environment resulted in approximately 1 bonded joints failure during mechanical pull tests performed at 1.25 times the flight loads. Failure analysis concluded that the failure mode was due to adhesive cracks that formed and propagated along stress concentrated fillets as a result of poor bond squeeze-out control during fabrication. Bond repairs were made and the structures successfully re-tested with an improved LN2 immersion test method to achieve protoflight thermal requirements.

Progressive Fracture and Damage Tolerance of Composite Pressure Vessels

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Gotsis, Pascal K.; Minnetyan, Levon

1997-01-01

Structural performance (integrity, durability and damage tolerance) of fiber reinforced composite pressure vessels, designed for pressured shelters for planetary exploration, is investigated via computational simulation. An integrated computer code is utilized for the simulation of damage initiation, growth, and propagation under pressure. Aramid fibers are considered in a rubbery polymer matrix for the composite system. Effects of fiber orientation and fabrication defect/accidental damages are investigated with regard to the safety and durability of the shelter. Results show the viability of fiber reinforced pressure vessels as damage tolerant shelters for planetary colonization.

Intelligent structures technology

NASA Astrophysics Data System (ADS)

Crawley, Edward F.

1991-07-01

Viewgraphs on intelligent structures technology are presented. Topics covered include: embedding electronics; electrical and mechanical compatibility; integrated circuit chip packaged for embedding; embedding devices within composite structures; test of embedded circuit in G/E coupon; temperature/humidity/bias test; single-chip microcomputer control experiment; and structural shape determination.

Intelligent structures technology

NASA Technical Reports Server (NTRS)

Crawley, Edward F.

1991-01-01

Viewgraphs on intelligent structures technology are presented. Topics covered include: embedding electronics; electrical and mechanical compatibility; integrated circuit chip packaged for embedding; embedding devices within composite structures; test of embedded circuit in G/E coupon; temperature/humidity/bias test; single-chip microcomputer control experiment; and structural shape determination.

Micromechanics-based magneto-elastic constitutive modeling of particulate composites

NASA Astrophysics Data System (ADS)

Yin, Huiming

Modified Green's functions are derived for three situations: a magnetic field caused by a local magnetization, a displacement field caused by a local body force and a displacement field caused by a local prescribed eigenstrain. Based on these functions, an explicit solution is derived for two magnetic particles embedded in the infinite medium under external magnetic and mechanical loading. A general solution for numerable magnetic particles embedded in an infinite domain is then provided in integral form. Two-phase composites containing spherical magnetic particles of the same size are considered for three kinds of microstructures. With chain-structured composites, particle interactions in the same chain are considered and a transversely isotropic effective elasticity is obtained. For periodic composites, an eight-particle interaction model is developed and provides a cubic symmetric effective elasticity. In the random composite, pair-wise particle interactions are integrated from all possible positions and an isotropic effective property is reached. This method is further extended to functionally graded composites. Magneto-mechanical behavior is studied for the chain-structured composite and the random composite. Effective magnetic permeability, effective magnetostriction and field-dependent effective elasticity are investigated. It is seen that the chain-structured composite is more sensitive to the magnetic field than the random composite; a composite consisting of only 5% of chain-structured particles can provide a larger magnetostriction and a larger change of effective elasticity than an equivalent composite consisting of 30% of random dispersed particles. Moreover, the effective shear modulus of the chain-structured composite rapidly increases with the magnetic field, while that for the random composite decreases. An effective hyperelastic constitutive model is further developed for a magnetostrictive particle-filled elastomer, which is sampled by using a network of body-centered cubic lattices of particles connected by macromolecular chains. The proposed hyperelastic model is able to characterize overall nonlinear elastic stress-stretch relations of the composites under general three-dimensional loading. It is seen that the effective strain energy density is proportional to the length of stretched chains in unit volume and volume fraction of particles.

Isolation of aramid nanofibers for high strength multiscale fiber reinforced composites

NASA Astrophysics Data System (ADS)

Lin, Jiajun; Patterson, Brendan A.; Malakooti, Mohammad H.; Sodano, Henry A.

2018-03-01

Aramid fibers are famous for their high specific strength and energy absorption properties and have been intensively used for soft body armor and ballistic protection. However, the use of aramid fiber reinforced composites is barely observed in structural applications. Aramid fibers have smooth and inert surfaces that are unable to form robust adhesion to polymeric matrices due to their high crystallinity. Here, a novel method to effectively integrate aramid fibers into composites is developed through utilization of aramid nanofibers. Aramid nanofibers are prepared from macroscale aramid fibers (such as Kevlar®) and isolated through a simple and scalable dissolution method. Prepared aramid nanofibers are dispersible in many polymers due to their improved surface reactivity, meanwhile preserve the conjugated structure and likely the strength of their macroscale counterparts. Simultaneously improved elastic modulus, strength and fracture toughness are observed in aramid nanofiber reinforced epoxy nanocomposites. When integrated in continuous fiber reinforced composites, aramid nanofibers can also enhance interfacial properties by forming hydrogen bonds and π-π coordination to bridge matrix and macroscale fibers. Such multiscale reinforcement by aramid nanofibers and continuous fibers results in strong polymeric composites with robust mechanical properties that are necessary and long desired for structural applications.

Portable wireless ultrasonic systems for remote inspection

NASA Astrophysics Data System (ADS)

Zhong, C. H.; Croxford, A. J.; Wilcox, P. D.

2015-03-01

The weight and power storage of conventional wire and active wireless systems limit their applications to composite structures such as wind turbines and aerospace structures. In this paper, a structurally-integrated, inert, wireless guided wave system for rapid composite inspection is demonstrated. The wireless interface is based on electromagnetic coupling between three coils, one of which is physically connected to an ultrasonic piezoelectric transducer and embedded in the structure, while the other two are in a separate probing unit. Compact encapsulated sensor units are designed, built and successfully embedded into carbon fibre composite panel at manufacture. Chirp-based excitation is used to enable single-shot measurements with high signal-to-noise ratios to be obtained. Results from sensors embedded in carbon fibre reinforced composite panel show that signal amplitude obtained by embedding the sensor into composite is almost twice that of a surface-bonded sensor. The promising results indicate that the developed sensor can be potentially used for impact damage in a large composite structure.

A critical review of nanotechnologies for composite aerospace structures

NASA Astrophysics Data System (ADS)

Kostopoulos, Vassilis; Masouras, Athanasios; Baltopoulos, Athanasios; Vavouliotis, Antonios; Sotiriadis, George; Pambaguian, Laurent

2017-03-01

The past decade extensive efforts have been invested in understanding the nano-scale and revealing the capabilities offered by nanotechnology products to structural materials. Integration of nano-particles into fiber composites concludes to multi-scale reinforced composites and has opened a new wide range of multi-functional materials in industry. In this direction, a variety of carbon based nano-fillers has been proposed and employed, individually or in combination in hybrid forms, to approach the desired performance. Nevertheless, a major issue faced lately more seriously due to the interest of industry is on how to incorporate these nano-species into the final composite structure through existing manufacturing processes and infrastructure. This interest originates from several industrial applications needs that request the development of new multi-functional materials which combine enhanced mechanical, electrical and thermal properties. In this work, an attempt is performed to review the most representative processes and related performances reported in literature and the experience obtained on nano-enabling technologies of fiber composite materials. This review focuses on the two main composite manufacturing technologies used by the aerospace industry; Prepreg/Autoclave and Resin Transfer technologies. It addresses several approaches for nano-enabling of composites for these two routes and reports latest achieved results focusing on performance of nano-enabled fiber reinforced composites extracted from literature. Finally, this review work identifies the gap between available nano-technology integration routes and the established industrial composite manufacturing techniques and the challenges to increase the Technology Readiness Level to reach the demands for aerospace industry applications.

The approach to engineering tasks composition on knowledge portals

NASA Astrophysics Data System (ADS)

Novogrudska, Rina; Globa, Larysa; Schill, Alexsander; Romaniuk, Ryszard; Wójcik, Waldemar; Karnakova, Gaini; Kalizhanova, Aliya

2017-08-01

The paper presents an approach to engineering tasks composition on engineering knowledge portals. The specific features of engineering tasks are highlighted, their analysis makes the basis for partial engineering tasks integration. The formal algebraic system for engineering tasks composition is proposed, allowing to set the context-independent formal structures for engineering tasks elements' description. The method of engineering tasks composition is developed that allows to integrate partial calculation tasks into general calculation tasks on engineering portals, performed on user request demand. The real world scenario «Calculation of the strength for the power components of magnetic systems» is represented, approving the applicability and efficiency of proposed approach.

Second Generation Integrated Composite Analyzer (ICAN) Computer Code

NASA Technical Reports Server (NTRS)

Murthy, Pappu L. N.; Ginty, Carol A.; Sanfeliz, Jose G.

1993-01-01

This manual updates the original 1986 NASA TP-2515, Integrated Composite Analyzer (ICAN) Users and Programmers Manual. The various enhancements and newly added features are described to enable the user to prepare the appropriate input data to run this updated version of the ICAN code. For reference, the micromechanics equations are provided in an appendix and should be compared to those in the original manual for modifications. A complete output for a sample case is also provided in a separate appendix. The input to the code includes constituent material properties, factors reflecting the fabrication process, and laminate configuration. The code performs micromechanics, macromechanics, and laminate analyses, including the hygrothermal response of polymer-matrix-based fiber composites. The output includes the various ply and composite properties, the composite structural response, and the composite stress analysis results with details on failure. The code is written in FORTRAN 77 and can be used efficiently as a self-contained package (or as a module) in complex structural analysis programs. The input-output format has changed considerably from the original version of ICAN and is described extensively through the use of a sample problem.

Fiber optics in composite materials: materials with nerves of glass

NASA Astrophysics Data System (ADS)

Measures, Raymond M.

1990-08-01

A Fiber Optic BasedSmart Structure wiipossess a structurally integrated optical microsensor system for determining its state. This built-in sensor system should, in real-time, be able to: evaluate the strain or deformation of a structure, monitor if its vibrating or subject to excessive loads, check its temperature and warn of the appearance of any hot spots. In addition a Smart Structure should maintain a vigilant survelliance over its structural integrity. The successful development of Smart StructureTechnolgy could lead to: aircraft that are safer, lighter, more efficient, easier to maintain and to service; pipelines, pressure vessels and storage tanks that constantly monitor their structuralintegrity and immediately issue an alert ifany problem is detected; space platforms that check forpressure leaks, unwanted vibration, excess thermal buildup, and deviation from some preassigned shape.This technology is particularly appropriate for composite materials where internal damage generated by: impacts, manufacturing flaws, excessive loading or fatigue could be detected and assessed. In service monitoring of structural loads, especially in regions like wing roots of aircraft, could be ofconsiderable benefit in helping to avoid structural overdesign and reduce weight. Structurally imbedded optical fibers sensors might also serve to monitor the cure state of composite thermosets during their fabrication and thereby contribute to improved quality control of these products.

Damage evaluation and analysis of composite pressure vessels using fiber Bragg gratings to determine structural health

NASA Astrophysics Data System (ADS)

Ortyl, Nicholas E.

2005-11-01

The application of MEMS and nanotechnology (MNT) to the field of structural health monitoring (SHM) is a fairly recent development. The recent change in this focus for MNT has been driven by the need to expand the applications for much of the technologies that were developed in the late 1990s. In addition, many companies desire to expand beyond their target high volume market segments of automotive, wireless communications, and computer peripherals, since these market segments were not as lucrative as first predicted. Most of the aerospace structural health monitoring developmental activity has been sponsored by agencies of the U.S. Government, which serves to pace the examination of these newer technologies to some degree. With that said, efforts are underway by companies such as Acellent Technologies and Blue Road Research to explore various MNT structural health monitoring approaches. The MNT under test include embedded piezoelectric sensors, MEMS accelerometers, time domain region sensors, and topical and embedded single and multi-axis fiber optic Bragg grating sensors. The promise of MNT for the SHM market segment is very enticing. The many wireless communication developments and miniaturization developments of the past five years is very attractive to the SHM community, especially those that are able to reduce the cost and complexity of integration. The main challenge for the community is one of selective integration. That is, certain pieces may be appropriate for SHM systems and certain pieces may not be. The better companies will chose wisely and put forth an approach that can be seamlessly integrated into the larger structure. For over a decade, Blue Road Research has been developing technologies aimed at structural health monitoring of both composite and non-composite parts, through the use of single and multiaxis fiber optic Bragg grating sensors. These sensors are 80 to 120 microns in diameter making them smaller than the diameter of a human hair. Multiaxis fiber optic sensors are able to measure pressure, temperature, axial and transverse strain, chemical properties, corrosion, as well as transverse strain gradients. This technology is easily embedded in between the various layers of the composite structure, during manufacture, without compromising the structural integrity, in order to verify manufacturing parameters during the cure cycle and well as monitor the on-going condition of the composite structure throughout its life time. This paper reviews some of the technical work that has been accomplished during the past two years; specifically the embedding of fiber optic sensors into various composite structures in order to be able to conduct in situ non-destructive evaluation of the curing process and the service life of the component. The fiber optic technology has been developed to the point that it is at a TRL of 6.

A Complex Shaped Reinforced Thermoplastic Composite Part Made of Commingled Yarns With Integrated Sensor

NASA Astrophysics Data System (ADS)

Risicato, Jean-Vincent; Kelly, Fern; Soulat, Damien; Legrand, Xavier; Trümper, Wolfgang; Cochrane, Cedric; Koncar, Vladan

2015-02-01

This paper focuses on the design and one shot manufacturing process of complex shaped composite parts based on the overbraiding of commingled yarns. The commingled yarns contain thermoplastic fibres used as the matrix and glass fibres as the reinforcement material. This technology reduces the flow path length for the melted thermoplastic and aims to improve the impregnation of materials with high viscosity. The tensile strength behaviour of the material was firstly investigated in order to evaluate the influence of the manufacturing parameters on flat structured braids that have been consolidated on a heating press. A good compatibility between the required geometry and the braiding process was observed. Additionally, piezo-resistive sensor yarns, based on glass yarns coated with PEDOT: PSS, have been successfully integrated within the composite structure. The sensor yarns have been inserted into the braided fabric, before consolidation. The inserted sensors provide the ability to monitor the structural health of the composite part in a real time. The design and manufacture of the complete complex shaped part has then been successfully achieved.

Laminar composite structures for high power actuators

NASA Astrophysics Data System (ADS)

Hobosyan, M. A.; Martinez, P. M.; Zakhidov, A. A.; Haines, C. S.; Baughman, R. H.; Martirosyan, K. S.

2017-05-01

Twisted laminar composite structures for high power and large-stroke actuators based on coiled Multi Wall Carbon Nanotube (MWNT) composite yarns were crafted by integrating high-density Nanoenergetic Gas Generators (NGGs) into carbon nanotube sheets. The linear actuation force, resulting from the pneumatic force caused by expanding gases confined within the pores of laminar structures and twisted carbon nanotube yarns, can be further amplified by increasing NGG loading and yarns twist density, as well as selecting NGG compositions with high energy density and large-volume gas generation. Moreover, the actuation force and power can be tuned by the surrounding environment, such as to increase the actuation by combustion in ambient air. A single 300-μm-diameter integrated MWNT/NGG coiled yarn produced 0.7 MPa stress and a contractile specific work power of up to 4.7 kW/kg, while combustion front propagated along the yarn at a velocity up to 10 m/s. Such powerful yarn actuators can also be operated in a vacuum, enabling their potential use for deploying heavy loads in outer space, such as to unfold solar panels and solar sails.

An Integrated Computational Materials Engineering Method for Woven Carbon Fiber Composites Preforming Process

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

Zhang, Weizhao; Ren, Huaqing; Wang, Zequn

2016-10-19

An integrated computational materials engineering method is proposed in this paper for analyzing the design and preforming process of woven carbon fiber composites. The goal is to reduce the cost and time needed for the mass production of structural composites. It integrates the simulation methods from the micro-scale to the macro-scale to capture the behavior of the composite material in the preforming process. In this way, the time consuming and high cost physical experiments and prototypes in the development of the manufacturing process can be circumvented. This method contains three parts: the micro-scale representative volume element (RVE) simulation to characterizemore » the material; the metamodeling algorithm to generate the constitutive equations; and the macro-scale preforming simulation to predict the behavior of the composite material during forming. The results show the potential of this approach as a guidance to the design of composite materials and its manufacturing process.« less

Integrated analysis and design of thick composite structures for optimal passive damping characteristics

NASA Technical Reports Server (NTRS)

Saravanos, D. A.

1993-01-01

The development of novel composite mechanics for the analysis of damping in composite laminates and structures and the more significant results of this effort are summarized. Laminate mechanics based on piecewise continuous in-plane displacement fields are described that can represent both intralaminar stresses and interlaminar shear stresses and the associated effects on the stiffness and damping characteristics of a composite laminate. Among other features, the mechanics can accurately model the static and damped dynamic response of either thin or thick composite laminates, as well as, specialty laminates with embedded compliant damping layers. The discrete laminate damping theory is further incorporated into structural analysis methods. In this context, an exact semi-analytical method for the simulation of the damped dynamic response of composite plates was developed. A finite element based method and a specialty four-node plate element were also developed for the analysis of composite structures of variable shape and boundary conditions. Numerous evaluations and applications demonstrate the quality and superiority of the mechanics in predicting the damped dynamic characteristics of composite structures. Finally, additional development was focused on the development of optimal tailoring methods for the design of thick composite structures based on the developed analytical capability. Applications on composite plates illustrated the influence of composite mechanics in the optimal design of composites and the potential for significant deviations in the resultant designs when more simplified (classical) laminate theories are used.

Time-varying volatility in Malaysian stock exchange: An empirical study using multiple-volatility-shift fractionally integrated model

NASA Astrophysics Data System (ADS)

Cheong, Chin Wen

2008-02-01

This article investigated the influences of structural breaks on the fractionally integrated time-varying volatility model in the Malaysian stock markets which included the Kuala Lumpur composite index and four major sectoral indices. A fractionally integrated time-varying volatility model combined with sudden changes is developed to study the possibility of structural change in the empirical data sets. Our empirical results showed substantial reduction in fractional differencing parameters after the inclusion of structural change during the Asian financial and currency crises. Moreover, the fractionally integrated model with sudden change in volatility performed better in the estimation and specification evaluations.

Open Circuit Resonant Sensors for Composite Damage Detection and Diagnosis

NASA Technical Reports Server (NTRS)

Mielnik, John J., Jr.

2011-01-01

Under the Integrated Vehicle Health Management (IVHM) program work was begun to investigate the feasibility of sensor systems for detecting and diagnosing damage to aircraft composite structures and materials. Specific interest for this study was in damage initiated by environmental storm hazards and the direct effect of lightning strikes on the material structures of a composite aircraft in flight. A series of open circuit resonant sensors was designed, fabricated, characterized, and determined to be a potentially viable means for damage detection and diagnosis of composite materials. The results of this research and development effort are documented in this report.

Symmetric Composite Laminate Stress Analysis

NASA Technical Reports Server (NTRS)

Wang, T.; Smolinski, K. F.; Gellin, S.

1985-01-01

It is demonstrated that COSMIC/NASTRAN may be used to analyze plate and shell structures made of symmetric composite laminates. Although general composite laminates cannot be analyzed using NASTRAN, the theoretical development presented herein indicates that the integrated constitutive laws of a symmetric composite laminate resemble those of a homogeneous anisotropic plate, which can be analyzed using NASTRAN. A detailed analysis procedure is presented, as well as an illustrative example.

Integration of magnetic bearings in the design of advanced gas turbine engines

NASA Technical Reports Server (NTRS)

Storace, Albert F.; Sood, Devendra K.; Lyons, James P.; Preston, Mark A.

1994-01-01

Active magnetic bearings provide revolutionary advantages for gas turbine engine rotor support. These advantages include tremendously improved vibration and stability characteristics, reduced power loss, improved reliability, fault-tolerance, and greatly extended bearing service life. The marriage of these advantages with innovative structural network design and advanced materials utilization will permit major increases in thrust to weight performance and structural efficiency for future gas turbine engines. However, obtaining the maximum payoff requires two key ingredients. The first key ingredient is the use of modern magnetic bearing technologies such as innovative digital control techniques, high-density power electronics, high-density magnetic actuators, fault-tolerant system architecture, and electronic (sensorless) position estimation. This paper describes these technologies. The second key ingredient is to go beyond the simple replacement of rolling element bearings with magnetic bearings by incorporating magnetic bearings as an integral part of the overall engine design. This is analogous to the proper approach to designing with composites, whereby the designer tailors the geometry and load carrying function of the structural system or component for the composite instead of simply substituting composites in a design originally intended for metal material. This paper describes methodologies for the design integration of magnetic bearings in gas turbine engines.

Reusable LH2 tank technology demonstration through ground test

NASA Technical Reports Server (NTRS)

Bianca, C.; Greenberg, H. S.; Johnson, S. E.

1995-01-01

The paper presents the project plan to demonstrate, by March 1997, the reusability of an integrated composite LH2 tank structure, cryogenic insulation, and thermal protection system (TPS). The plan includes establishment of design requirements and a comprehensive trade study to select the most suitable Reusable Hydrogen Composite Tank system (RHCTS) within the most suitable of 4 candidate structural configurations. The 4 vehicles are winged body with the capability to deliver 25,000 lbs of payload to a circular 220 nm, 51.6 degree inclined orbit (also 40,000 lbs to a 28.5 inclined 150 nm orbit). A prototype design of the selected RHCTS is established to identify the construction, fabrication, and stress simulation and test requirements necessary in an 8 foot diameter tank structure/insulation/TPS test article. A comprehensive development test program supports the 8 foot test article development and involves the composite tank itself, cryogenic insulation, and integrated tank/insulation/TPS designs. The 8 foot diameter tank will contain the integrated cryogenic insulation and TPS designs resulting from this development and that of the concurrent lightweight durable TPS program. Tank ground testing will include 330 cycles of LH2 filling, pressurization, body loading, depressurization, draining, and entry heating.

Active Control Technology at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Antcliff, Richard R.; McGowan, Anna-Marie R.

2000-01-01

NASA Langley has a long history of attacking important technical opportunities from a broad base of supporting disciplines. The research and development at Langley in this subject area range from the test tube to the test flight. The information covered here will range from the development of innovative new materials, sensors and actuators, to the incorporation of smart sensors and actuators in practical devices, to the optimization of the location of these devices, to, finally, a wide variety of applications of these devices utilizing Langley's facilities and expertise. Advanced materials are being developed for sensors and actuators, as well as polymers for integrating smart devices into composite structures. Contributions reside in three key areas: computational materials; advanced piezoelectric materials; and integrated composite structures. The computational materials effort is focused on developing predictive tools for the efficient design of new materials with the appropriate combination of properties for next generation smart airframe systems. Research in the area of advanced piezoelectrics includes optimizing the efficiency, force output, use temperature, and energy transfer between the structure and device for both ceramic and polymeric materials. For structural health monitoring, advanced non-destructive techniques including fiber optics are being developed for detection of delaminations, cracks and environmental deterioration in aircraft structures. The computational materials effort is focused on developing predictive tools for the efficient design of new materials with the appropriate combination of properties for next generation smart airframe system. Innovative fabrication techniques processing structural composites with sensor and actuator integration are being developed.

Mechanism Design and Testing of a Self-Deploying Structure Using Flexible Composite Tape Springs

NASA Technical Reports Server (NTRS)

Footdale, Joseph N.; Murphey, Thomas W.

2014-01-01

The detailed mechanical design of a novel deployable support structure that positions and tensions a membrane optic for space imagining applications is presented. This is a complex three-dimensional deployment using freely deploying rollable composite tape spring booms that become load bearing structural members at full deployment. The deployment tests successfully demonstrate a new architecture based on rolled and freely deployed composite tape spring members that achieve simultaneous deployment without mechanical synchronization. Proper design of the flexible component mounting interface and constraint systems, which were critical in achieving a functioning unit, are described. These flexible composite components have much potential for advancing the state of the art in deployable structures, but have yet to be widely adopted. This paper demonstrates the feasibility and advantages of implementing flexible composite components, including the design details on how to integrate with required traditional mechanisms.

Delineating ecological regions in marine systems: Integrating physical structure and community composition to inform spatial management in the eastern Bering Sea

NASA Astrophysics Data System (ADS)

Baker, Matthew R.; Hollowed, Anne B.

2014-11-01

Characterizing spatial structure and delineating meaningful spatial boundaries have useful applications to understanding regional dynamics in marine systems, and are integral to ecosystem approaches to fisheries management. Physical structure and drivers combine with biological responses and interactions to organize marine systems in unique ways at multiple scales. We apply multivariate statistical methods to define spatially coherent ecological units or ecoregions in the eastern Bering Sea. We also illustrate a practical approach to integrate data on species distribution, habitat structure and physical forcing mechanisms to distinguish areas with distinct biogeography as one means to define management units in large marine ecosystems. We use random forests to quantify the relative importance of habitat and environmental variables to the distribution of individual species, and to quantify shifts in multispecies assemblages or community composition along environmental gradients. Threshold shifts in community composition are used to identify regions with distinct physical and biological attributes, and to evaluate the relative importance of predictor variables to determining regional boundaries. Depth, bottom temperature and frontal boundaries were dominant factors delineating distinct biological communities in this system, with a latitudinal divide at approximately 60°N. Our results indicate that distinct climatic periods will shift habitat gradients and that dynamic physical variables such as temperature and stratification are important to understanding temporal stability of ecoregion boundaries. We note distinct distribution patterns among functional guilds and also evidence for resource partitioning among individual species within each guild. By integrating physical and biological data to determine spatial patterns in community composition, we partition ecosystems along ecologically significant gradients. This may provide a basis for defining spatial management units or serve as a baseline index for analyses of structural shifts in the physical environment, species abundance and distribution, and community dynamics over time.

Integrated photonics using colloidal quantum dots

NASA Astrophysics Data System (ADS)

Menon, Vinod M.; Husaini, Saima; Okoye, Nicky; Valappil, Nikesh V.

2009-11-01

Integrated photonic devices were realized using colloidal quantum dot composites such as flexible microcavity laser, microdisk emitters and integrated active-passive waveguides. The microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. Planar photonic devices consisting of vertically coupled microring resonators, microdisk emitters, active-passive integrated waveguide structures and coupled active microdisk resonators were realized using soft lithography, photo-lithography, and electron beam lithography, respectively. The gain medium in all these devices was a composite consisting of quantum dots embedded in SU8 matrix. Finally, the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements was determined. In addition to their specific functionalities, these novel device demonstrations and their development present a low-cost alternative to the traditional photonic device fabrication techniques.

TRANSTRAIN: A program to compute strain transformations in composite materials

NASA Technical Reports Server (NTRS)

Ahmed, Rafiq

1990-01-01

Over the years, the solid rocket motor community has made increasing use of composite materials for thermal and structural applications. This is particularly true of solid rocket nozzles, which have used carbon phenolic and, increasingly, carbon-carbon materials to provide structural integrity and thermal protection at the high temperatures encountered during motor burn. To evaluate the degree of structural performance of nozzles and their materials and to verify analysis models, many subscale and full-scale tests are run. These provide engineers with valuable data needed to optimize design and to analyze nozzle hardware. Included among these data are strains, pressures, thrust, temperatures, and displacements. Recent nozzle test hardware has made increasing use of strain gauges embedded in the carbon composite material to measure internal strains. In order to evaluate strength, these data must be transformed into strains along the fiber directions. The fiber-direction stresses can then be calculated. A computer program written to help engineers correctly manipulate the strain data into a form that can be used to evaluate structural integrity of the nozzle is examined.

A smart composite patch for the repair of aircraft structures

NASA Astrophysics Data System (ADS)

Wakha, Kelah; Samuel, Paul; Pines, Darryll J.

2005-05-01

Recent interest in bonded composite patch repair technology for aerospace systems is because this method can be carried out at a reduced cost and time and can easily be applied to complex geometric structures. This paper details the development of a dual stiffness/energy sensor for monitoring the integrity of a composite patch used to repair an aluminum structural component. The smart sensor has the ability to predict the elastic field of a given host structure based on the strain state of two sub-sensors integrated into the structure. The present study shows the possibility of using the sensor to deduce the local instantaneous host stiffness. Damaged structures are characterized by a reduction in their elastic stiffness that evolve from microstructural defects. A local smart sensor can be developed to sense the local average properties on a host. In this paper, sensors are attached to a structure and a modified Eshelby's equivalent inclusion method is used to derive the elastic properties of the host. An analytical derivation and a sensitivity analysis for the quasistatic application is given in a papers by Majed, Dasgupta, Kelah and Pines. A summary of the derivation of the dynamic Eshelby tensor is presented. This is of importance because damage detection in structures undergoing vibratory and other motions present a greater challenge than those in quasistatic motion. An in-situ health monitoring active sensor system for a real structure (an aluminum plate with an attached repair patch) under close-to real lifecycle loading conditions is developed. The detection of the onset of any damage to the structure as well as the repair patch and the subsequent monitoring of the growth of this damage constitute important goals of the system. Both experimental and finite element methods were applied. Experimental results are presented for tests of the aluminum plate with the repair patch under monotonic quasi-static and dynamic loading vibratory conditions. In summary, the study shows that smart bonded composite repair patches are very effective in the repair of thin aluminum structures since they are able to determine the integrity of the repair structure as well as the repair patch.

Microstructure of the smart composite structures with embedded fiber optic sensing nerves

NASA Astrophysics Data System (ADS)

Liu, Jingyuan; Luo, Fei; Li, Changchun; Ma, Naibin

1997-11-01

The composite structures with embedded optical fiber sensors construct a smart composite structure system, which may have the characteristics of the in-service self-measurement, self- recognition and self-judgement action. In the present work, we studied the microstructures of carbon/epoxy composite laminates with embedded sensing optical fibers, and the integration of optical fiber with composites was also discussed. The preliminary experiment results show that because of the difference between the sensing optical fibers and the reinforcing fibers in their size, the microstructure of the composites with embedded optical fibers will produce partial local changes in the area of embedded optical fiber, these changes may affect the mechanical properties of composite structures. When the optical fibers are embedded parallel to the reinforcing fibers, due to the composite prepregs are formed under a press action during its curing process, the reinforcing fibers can be arranged equably around the optical fibers. But when the optical fibers are embedded perpendicularly to the reinforcement fibers, the resin rich pocket will appear in the composite laminates surrounding the embedded optical fiber. The gas holes will be easily produced in these zones which may produce a premature failure of the composite structure. The photoelastic experiments are also given in the paper.

Shape and Stress Sensing of Multilayered Composite and Sandwich Structures Using an Inverse Finite Element Method

NASA Technical Reports Server (NTRS)

Cerracchio, Priscilla; Gherlone, Marco; Di Sciuva, Marco; Tessler, Alexander

2013-01-01

The marked increase in the use of composite and sandwich material systems in aerospace, civil, and marine structures leads to the need for integrated Structural Health Management systems. A key capability to enable such systems is the real-time reconstruction of structural deformations, stresses, and failure criteria that are inferred from in-situ, discrete-location strain measurements. This technology is commonly referred to as shape- and stress-sensing. Presented herein is a computationally efficient shape- and stress-sensing methodology that is ideally suited for applications to laminated composite and sandwich structures. The new approach employs the inverse Finite Element Method (iFEM) as a general framework and the Refined Zigzag Theory (RZT) as the underlying plate theory. A three-node inverse plate finite element is formulated. The element formulation enables robust and efficient modeling of plate structures instrumented with strain sensors that have arbitrary positions. The methodology leads to a set of linear algebraic equations that are solved efficiently for the unknown nodal displacements. These displacements are then used at the finite element level to compute full-field strains, stresses, and failure criteria that are in turn used to assess structural integrity. Numerical results for multilayered, highly heterogeneous laminates demonstrate the unique capability of this new formulation for shape- and stress-sensing.

Supersonic cruise research aircraft structural studies: Methods and results

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, J.; Gross, D.; Kurtze, W.; Newsom, J.; Wrenn, G.; Greene, W.

1981-01-01

NASA Langley Research Center SCAR in-house structural studies are reviewed. In methods development, advances include a new system of integrated computer programs called ISSYS, progress in determining aerodynamic loads and aerodynamically induced structural loads (including those due to gusts), flutter optimization for composite and metal airframe configurations using refined and simplified mathematical models, and synthesis of active controls. Results given address several aspects of various SCR configurations. These results include flutter penalties on composite wing, flutter suppression using active controls, roll control effectiveness, wing tip ground clearance, tail size effect on flutter, engine weight and mass distribution influence on flutter, and strength and flutter optimization of new configurations. The ISSYS system of integrated programs performed well in all the applications illustrated by the results, the diversity of which attests to ISSYS' versatility.

Quiet Clean Short-haul Experimental Engine (QCSEE). Composite fan frame subsystem test report

NASA Technical Reports Server (NTRS)

Stotler, C. L., Jr.; Bowden, J. H.

1977-01-01

The element and subcomponent testing conducted to verify the composite fan frame design of two experimental high bypass geared turbofan engines and propulsion systems for short haul passenger aircraft is described. Emphasis is placed on the propulsion technology required for future externally blown flap aircraft with engines located both under the wing and over the wing, including technology in composite structures and digital engine controls. The element tests confirmed that the processes used in the frame design would produce the predicted mechanical properties. The subcomponent tests verified that the detail structural components of the frame had adequate structural integrity.

Supersonic Cruise Research 1979, part 2. [airframe structures and materials, systems integration, economic analysis

NASA Technical Reports Server (NTRS)

1980-01-01

Advances in airframe structure and materials technology for supersonic cruise aircraft are reported with emphasis on titanium and composite structures. The operation of the Concorde is examined as a baseline for projections into the future. A market survey of U.S. passenger attitudes and preferences, the impact of advanced air transport technology and the integration of systems for the advanced SST and for a smaller research/business jet vehicle are also discussed.

Structure and properties of composite films formed by cellulose nanocrystals and charged latex nanoparticles

NASA Astrophysics Data System (ADS)

Thérien-Aubin, Héloïse; Lukach, Ariella; Pitch, Natalie; Kumacheva, Eugenia

2015-04-01

We report the structural and optical properties of composite films formed from mixed suspensions of cellulose nanocrystals (CNCs) and fluorescent latex nanoparticles (NPs). We explored the effect of NP concentration, size, surface charge, glass transition temperature and film processing conditions on film structure and properties. The chiral nematic order, typical of CNC films, was preserved in films with up to 50 wt% of negatively-charged latex NPs. Composite films were characterized by macroscopically close-to-uniform fluorescence, birefringence, and circular dichroism properties. In contrast, addition of positively charged latex NPs led to gelation of CNC-latex suspensions and disruption of the chiral nematic order in the composite films. Large latex NPs disrupted the chiral nematic order to a larger extend than small NPs. Furthermore, the glass transition of latex NPs had a dramatic effect on the structure of CNC-latex films. Latex particles in the rubbery state were easily incorporated in the ordered CNC matrix and improved the structural integrity of its chiral nematic phase.We report the structural and optical properties of composite films formed from mixed suspensions of cellulose nanocrystals (CNCs) and fluorescent latex nanoparticles (NPs). We explored the effect of NP concentration, size, surface charge, glass transition temperature and film processing conditions on film structure and properties. The chiral nematic order, typical of CNC films, was preserved in films with up to 50 wt% of negatively-charged latex NPs. Composite films were characterized by macroscopically close-to-uniform fluorescence, birefringence, and circular dichroism properties. In contrast, addition of positively charged latex NPs led to gelation of CNC-latex suspensions and disruption of the chiral nematic order in the composite films. Large latex NPs disrupted the chiral nematic order to a larger extend than small NPs. Furthermore, the glass transition of latex NPs had a dramatic effect on the structure of CNC-latex films. Latex particles in the rubbery state were easily incorporated in the ordered CNC matrix and improved the structural integrity of its chiral nematic phase. Electronic supplementary information (ESI) available: Detailed latex synthesis. Additional characterization of the nanoparticles and films. See DOI: 10.1039/c5nr00660k

Manufacturing of Smart Structures Using Fiber Placement Manufacturing Processes

NASA Technical Reports Server (NTRS)

Thomas, Matthew M.; Glowasky, Robert A.; McIlroy, Bruce E.; Story, Todd A.

1996-01-01

Smart structures research and development, with the ultimate aim of rapid commercial and military production of these structures, are at the forefront of the Synthesis and Processing of Intelligent Cost-Effective Structures (SPICES) program. As part of this ARPA-sponsored program, MDA-E is using fiber placement processes to manufacture integrated smart structure systems. These systems comprise advanced composite structures with embedded fiber optic sensors, shape memory alloys, piezoelectric actuators, and miniature accelerometers. Cost-effective approaches and solutions to smart material synthesis in the fiber-placement process, based upon integrated product development, are discussed herein.

Methodologies for Combined Loads Tests Using a Multi-Actuator Test Machine

NASA Technical Reports Server (NTRS)

Rouse, Marshall

2013-01-01

The NASA Langley COmbined Loads Test System (COLTS) Facility was designed to accommodate a range of fuselage structures and wing sections and subject them to both quasistatic and cyclic loading conditions. Structural tests have been conducted in COLTS that address structural integrity issues of metallic and fiber reinforced composite aerospace structures in support of NASA Programs (i.e. the Aircraft Structural Integrity (ASIP) Program, High-Speed-Research program and the Supersonic Project, NASA Engineering and Safety Center (NESC) Composite Crew Module Project, and the Environmentally Responsible Aviation Program),. This paper presents experimental results for curved panels subjected to mechanical and internal pressure loads using a D-box test fixture. Also, results are presented that describe use of a checkout beam for development of testing procedures for a combined mechanical and pressure loading test of a Multi-bay box. The Multi-bay box test will be used to experimentally verify the structural performance of the Multi-bay box in support of the Environmentally Responsible Aviation Project at NASA Langley.

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.

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

Adhesive Defect Monitoring of Glass Fiber Epoxy Plate Using an Impedance-Based Non-Destructive Testing Method for Multiple Structures

PubMed Central

Na, Wongi S.; Baek, Jongdae

2017-01-01

The emergence of composite materials has revolutionized the approach to building engineering structures. With the number of applications for composites increasing every day, maintaining structural integrity is of utmost importance. For composites, adhesive bonding is usually the preferred choice over the mechanical fastening method, and monitoring for delamination is an essential factor in the field of composite materials. In this study, a non-destructive method known as the electromechanical impedance method is used with an approach of monitoring multiple areas by specifying certain frequency ranges to correspond to a certain test specimen. Experiments are conducted using various numbers of stacks created by attaching glass fiber epoxy composite plates onto one another, and two different debonding damage types are introduced to evaluate the performance of the multiple monitoring electromechanical impedance method. PMID:28629194

Poling of PVDF matrix composites for integrated structural load sensing

NASA Astrophysics Data System (ADS)

Haghiashtiani, Ghazaleh; Greminger, Michael A.; Zhao, Ping

2014-03-01

The purpose of this study is to create and evaluate a smart composite structure that can be used for integrated load sensing and structural health monitoring. In this structure, PVDF films are used as the matrix material instead of epoxy resin or other thermoplastics. The reinforcements are two layers of carbon fiber with one layer of Kevlar separating them. Due to the electrical conductivity properties of carbon fiber and the dielectric effect of Kevlar, the structure acts as a capacitor. Furthermore, the piezoelectric properties of the PVDF matrix can be used to monitor the response of the structure under applied loads. In order to exploit the piezoelectric properties of PVDF, the PVDF material must be polarized to align the dipole moments of its crystalline structure. The optimal condition for poling the structure was found by performing a 23 factorial design of experiment (DoE). The factors that were studied in DoE were temperature, voltage, and duration of poling. Finally, the response of the poled structure was monitored by exposing the samples to an applied load.

ICAN: A versatile code for predicting composite properties

NASA Technical Reports Server (NTRS)

Ginty, C. A.; Chamis, C. C.

1986-01-01

The Integrated Composites ANalyzer (ICAN), a stand-alone computer code, incorporates micromechanics equations and laminate theory to analyze/design multilayered fiber composite structures. Procedures for both the implementation of new data in ICAN and the selection of appropriate measured data are summarized for: (1) composite systems subject to severe thermal environments; (2) woven fabric/cloth composites; and (3) the selection of new composite systems including those made from high strain-to-fracture fibers. The comparisons demonstrate the versatility of ICAN as a reliable method for determining composite properties suitable for preliminary design.

SiC Fiber-Reinforced Celsian Composites

NASA Technical Reports Server (NTRS)

Bansal, Narottam P.

2003-01-01

Celsian is a promising matrix material for fiber-reinforced composites for high temperature structural applications. Processing and fabrication of small diameter multifilament silicon carbide tow reinforced celsian matrix composites are described. Mechanical and microstructural properties of these composites at ambient and elevated temperatures are presented. Effects of high-temperature exposures in air on the mechanical behavior of these composites are also given. The composites show mechanical integrity up to 1100 C but degrade at higher temperatures in oxidizing atmospheres. A model has been proposed for the degradation of these composites in oxidizing atmospheres at high temperatures.

Computer codes developed and under development at Lewis

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1992-01-01

The objective of this summary is to provide a brief description of: (1) codes developed or under development at LeRC; and (2) the development status of IPACS with some typical early results. The computer codes that have been developed and/or are under development at LeRC are listed in the accompanying charts. This list includes: (1) the code acronym; (2) select physics descriptors; (3) current enhancements; and (4) present (9/91) code status with respect to its availability and documentation. The computer codes list is grouped by related functions such as: (1) composite mechanics; (2) composite structures; (3) integrated and 3-D analysis; (4) structural tailoring; and (5) probabilistic structural analysis. These codes provide a broad computational simulation infrastructure (technology base-readiness) for assessing the structural integrity/durability/reliability of propulsion systems. These codes serve two other very important functions: they provide an effective means of technology transfer; and they constitute a depository of corporate memory.

Composites research at NASA Lewis Research Center

NASA Technical Reports Server (NTRS)

Levine, Stanley R.; Duffy, Stephen; Vary, Alex; Nathal, Michael V.; Miner, Robert V.; Arnold, Steven M.; Castelli, Michael G.; Hopkins, Dale A.; Meador, Michael A.

1994-01-01

Composites research at NASA Lewis is focused on their applications in aircraft propulsion, space propulsion, and space power, with the first being predominant. Research on polymer-, metal-, and ceramic-matrix composites is being carried out from an integrated materials and structures viewpoint. This paper outlines some of the topics being pursued from the standpoint of key technical issues, current status, and future directions.

Lithium-aluminum-magnesium electrode composition

DOEpatents

Melendres, Carlos A.; Siegel, Stanley

1978-01-01

A negative electrode composition is presented for use in a secondary, high-temperature electrochemical cell. The cell also includes a molten salt electrolyte of alkali metal halides or alkaline earth metal halides and a positive electrode including a chalcogen or a metal chalcogenide as the active electrode material. The negative electrode composition includes up to 50 atom percent lithium as the active electrode constituent and a magnesium-aluminum alloy as a structural matrix. Various binary and ternary intermetallic phases of lithium, magnesium, and aluminum are formed but the electrode composition in both its charged and discharged state remains substantially free of the alpha lithium-aluminum phase and exhibits good structural integrity.

Light weight, high-speed, and self-powered wireless fiber optic sensor (WiFOS) structural health monitor system for avionics and aerospace environments

NASA Astrophysics Data System (ADS)

Mendoza, Edgar A.; Kempen, Cornelia; Sun, Sunjian; Esterkin, Yan

2014-09-01

This paper describes recent progress towards the development of an innovative light weight, high-speed, and selfpowered wireless fiber optic sensor (WiFOS™) structural health monitor system suitable for the onboard and in-flight unattended detection, localization, and classification of load, fatigue, and structural damage in advanced composite materials commonly used in avionics and aerospace systems. The WiFOS™ system is based on ROI's advancements on monolithic photonic integrated circuit microchip technology, integrated with smart power management, on-board data processing, wireless data transmission optoelectronics, and self-power using energy harvesting tools such as solar, vibration, thermoelectric, and magneto-electric. The self-powered, wireless WiFOS™ system offers a versatile and powerful SHM tool to enhance the reliability and safety of avionics platforms, jet fighters, helicopters, commercial aircraft that use lightweight composite material structures, by providing comprehensive information about the structural integrity of the structure from a large number of locations. Immediate SHM applications are found in rotorcraft and aircraft, ships, submarines, and in next generation weapon systems, and in commercial oil and petrochemical, aerospace industries, civil structures, power utilities, portable medical devices, and biotechnology, homeland security and a wide spectrum of other applications.

Novel self-sensing carbon nanotube-based composites for rehabilitation of structural steel members

NASA Astrophysics Data System (ADS)

Ahmed, Shafique; Doshi, Sagar; Schumacher, Thomas; Thostenson, Erik T.; McConnell, Jennifer

2016-02-01

Fatigue and fracture are among the most critical forms of damage in metal structures. Fatigue damage can initiate from microscopic defects (e.g., surface scratches, voids in welds, and internal defects) and initiate a crack. Under cyclic loading, these cracks can grow and reach a critical level to trigger fracture of the member which leads to compromised structural integrity and, in some cases, catastrophic failure of the entire structure. In our research, we are investigating a solution using carbon nanotube-based sensing composites, which have the potential to simultaneously rehabilitate and monitor fatigue-cracked structural members. These composites consist of a fiber-reinforced polymer (FRP) layer and a carbon nanotube-based sensing layer, which are integrated to form a novel structural self-sensing material. The sensing layer is composed of a non-woven aramid fabric that is coated with carbon nanotubes (CNT) to form an electrically conductive network that is extremely sensitive to detecting deformation as well as damage accumulation via changes in the resistance of the CNT network. In this paper, we introduce the sensing concept, describe the manufacturing of a model sensing prototype, and discuss a set of small-scale laboratory experiments to examine the load-carrying capacity and damage sensing response.

Computational simulation of progressive fracture in fiber composites

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1986-01-01

Computational methods for simulating and predicting progressive fracture in fiber composite structures are presented. These methods are integrated into a computer code of modular form. The modules include composite mechanics, finite element analysis, and fracture criteria. The code is used to computationally simulate progressive fracture in composite laminates with and without defects. The simulation tracks the fracture progression in terms of modes initiating fracture, damage growth, and imminent global (catastrophic) laminate fracture.

Polymer coating for immobilizing soluble ions in a phosphate ceramic product

DOEpatents

Singh, Dileep; Wagh, Arun S.; Patel, Kartikey D.

2000-01-01

A polymer coating is applied to the surface of a phosphate ceramic composite to effectively immobilize soluble salt anions encapsulated within the phosphate ceramic composite. The polymer coating is made from ceramic materials, including at least one inorganic metal compound, that wet and adhere to the surface structure of the phosphate ceramic composite, thereby isolating the soluble salt anions from the environment and ensuring long-term integrity of the phosphate ceramic composite.

Incorporation of composite defects from ultrasonic NDE into CAD and FE models

NASA Astrophysics Data System (ADS)

Bingol, Onur Rauf; Schiefelbein, Bryan; Grandin, Robert J.; Holland, Stephen D.; Krishnamurthy, Adarsh

2017-02-01

Fiber-reinforced composites are widely used in aerospace industry due to their combined properties of high strength and low weight. However, owing to their complex structure, it is difficult to assess the impact of manufacturing defects and service damage on their residual life. While, ultrasonic testing (UT) is the preferred NDE method to identify the presence of defects in composites, there are no reasonable ways to model the damage and evaluate the structural integrity of composites. We have developed an automated framework to incorporate flaws and known composite damage automatically into a finite element analysis (FEA) model of composites, ultimately aiding in accessing the residual life of composites and make informed decisions regarding repairs. The framework can be used to generate a layer-by-layer 3D structural CAD model of the composite laminates replicating their manufacturing process. Outlines of structural defects, such as delaminations, are automatically detected from UT of the laminate and are incorporated into the CAD model between the appropriate layers. In addition, the framework allows for direct structural analysis of the resulting 3D CAD models with defects by automatically applying the appropriate boundary conditions. In this paper, we show a working proof-of-concept for the composite model builder with capabilities of incorporating delaminations between laminate layers and automatically preparing the CAD model for structural analysis using a FEA software.

Multifunctional smart composites with integrated carbon nanotube yarn and sheet

NASA Astrophysics Data System (ADS)

Chauhan, Devika; Hou, Guangfeng; Ng, Vianessa; Chaudhary, Sumeet; Paine, Michael; Moinuddin, Khwaja; Rabiee, Massoud; Cahay, Marc; Lalley, Nicholas; Shanov, Vesselin; Mast, David; Liu, Yijun; Yin, Zhangzhang; Song, Yi; Schulz, Mark

2017-04-01

Multifunctional smart composites (MSCs) are materials that combine the good electrical and thermal conductivity, high tensile and shear strength, good impact toughness, and high stiffness properties of metals; the light weight and corrosion resistance properties of composites; and the sensing or actuation properties of smart materials. The basic concept for MSCs was first conceived by Daniel Inman and others about 25 years ago. Current laminated carbon and glass fiber polymeric composite materials have high tensile strength and are light in weight, but they still lack good electrical and thermal conductivity, and they are sensitive to delamination. Carbon nanotube yarn and sheets are lightweight, electrically and thermally conductive materials that can be integrated into laminated composite materials to form MSCs. This paper describes the manufacturing of high quality carbon nanotube yarn and sheet used to form MSCs, and integrating the nanotube yarn and sheet into composites at low volume fractions. Various up and coming technical applications of MSCs are discussed including composite toughening for impact and delamination resistance; structural health monitoring; and structural power conduction. The global carbon nanotube overall market size is estimated to grow from 2 Billion in 2015 to 5 Billion by 2020 at a CAGR of 20%. Nanotube yarn and sheet products are predicted to be used in aircraft, wind machines, automobiles, electric machines, textiles, acoustic attenuators, light absorption, electrical wire, sporting equipment, tires, athletic apparel, thermoelectric devices, biomedical devices, lightweight transformers, and electromagnets. In the future, due to the high maximum current density of nanotube conductors, nanotube electromagnetic devices may also become competitive with traditional smart materials in terms of power density.

Surface functionalization of hexagonal boron nitride and its effect on the structure and performance of composites

NASA Astrophysics Data System (ADS)

Jin, Wenqin; Zhang, Wei; Gao, Yuwen; Liang, Guozheng; Gu, Aijuan; Yuan, Li

2013-04-01

A new organized hexagonal boron nitride (OhBN) with significantly increased amount of amine groups was synthesized, and characterized by Fourier Transform Infrared (FTIR), X-ray Photoelectron Spectroscopy (XPS), Thermogravimetric (TG) analysis, UV-vis Transmittance Spectra, Transmission Electron Microscope (TEM) and the potentiometric titration. The content of amine groups for OhBN is about 5 times of that for original hexagonal boron nitride (hBN). Based on the preparation of OhBN, new composites consisting of OhBN and bismaleimide (BD) resin were developed, which show greatly improved integrated performance (including dynamic mechanical, dielectric and thermal properties) compared with BD resin and the hBN/BD composites. In the case of the OhBN/BD composite with 15 wt% OhBN, its storage modulus, dielectric loss, thermal conductivity and coefficient of thermal expansion are about 1.2, 0.56, 1.11 and 0.92 times of the corresponding values of hBN/BD composite, respectively; moreover, the glass transition temperature of the former is 15 °C higher than that of the latter. These interesting results suggest that the integrated performance of the composites is closely related to the surface nature of the fillers because the change in the surface nature not only varies the chemical structure, free volume and crosslinking density of the composite, but also determines the interfacial nature between inorganic fillers and the resin matrix. This investigation demonstrates that the method proposed herein provides a new approach to prepare organized inorganic fillers as well as corresponding composites with controlled structure and expected performances for cutting-edge industries.

Manufacturing Technology Support (MATES II) Task Order 0005: Manufacturing Integration and Technology Evaluation to Enable Technology Transition. Subtask Phase 0 Study Task: Manufacturing Technology (ManTech) and Systems Engineering For Quick Reaction Systems

DTIC Science & Technology

2014-10-01

Porosity from gas entrapment & shrinkage 4 Continuous Fiber Ti Metal Matrix Composites (Aircraft panels and rotor components) [14...process models for casting, forging, and welding , and software capability to integrate various independent models with design, thermal, and structural...Applications, Ph.D. Thesis, Queen’s College, University of Oxford, (2007). 14. S.A. Singerman and J.J. Jackson, Titanium Metal Matrix Composites for

Using graphene networks to build bioinspired self-monitoring ceramics

PubMed Central

Picot, Olivier T.; Rocha, Victoria G.; Ferraro, Claudio; Ni, Na; D'Elia, Eleonora; Meille, Sylvain; Chevalier, Jerome; Saunders, Theo; Peijs, Ton; Reece, Mike J.; Saiz, Eduardo

2017-01-01

The properties of graphene open new opportunities for the fabrication of composites exhibiting unique structural and functional capabilities. However, to achieve this goal we should build materials with carefully designed architectures. Here, we describe the fabrication of ceramic-graphene composites by combining graphene foams with pre-ceramic polymers and spark plasma sintering. The result is a material containing an interconnected, microscopic network of very thin (20–30 nm), electrically conductive, carbon interfaces. This network generates electrical conductivities up to two orders of magnitude higher than those of other ceramics with similar graphene or carbon nanotube contents and can be used to monitor ‘in situ' structural integrity. In addition, it directs crack propagation, promoting stable crack growth and increasing the fracture resistance by an order of magnitude. These results demonstrate that the rational integration of nanomaterials could be a fruitful path towards building composites combining unique mechanical and functional performances. PMID:28181518

Multidisciplinary tailoring of hot composite structures

NASA Technical Reports Server (NTRS)

Singhal, Surendra N.; Chamis, Christos C.

1993-01-01

A computational simulation procedure is described for multidisciplinary analysis and tailoring of layered multi-material hot composite engine structural components subjected to simultaneous multiple discipline-specific thermal, structural, vibration, and acoustic loads. The effect of aggressive environments is also simulated. The simulation is based on a three-dimensional finite element analysis technique in conjunction with structural mechanics codes, thermal/acoustic analysis methods, and tailoring procedures. The integrated multidisciplinary simulation procedure is general-purpose including the coupled effects of nonlinearities in structure geometry, material, loading, and environmental complexities. The composite material behavior is assessed at all composite scales, i.e., laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization hygro-thermo-mechanical model. Sample tailoring cases exhibiting nonlinear material/loading/environmental behavior of aircraft engine fan blades, are presented. The various multidisciplinary loads lead to different tailored designs, even those competing with each other, as in the case of minimum material cost versus minimum structure weight and in the case of minimum vibration frequency versus minimum acoustic noise.

Homogenization-based interval analysis for structural-acoustic problem involving periodical composites and multi-scale uncertain-but-bounded parameters.

PubMed

Chen, Ning; Yu, Dejie; Xia, Baizhan; Liu, Jian; Ma, Zhengdong

2017-04-01

This paper presents a homogenization-based interval analysis method for the prediction of coupled structural-acoustic systems involving periodical composites and multi-scale uncertain-but-bounded parameters. In the structural-acoustic system, the macro plate structure is assumed to be composed of a periodically uniform microstructure. The equivalent macro material properties of the microstructure are computed using the homogenization method. By integrating the first-order Taylor expansion interval analysis method with the homogenization-based finite element method, a homogenization-based interval finite element method (HIFEM) is developed to solve a periodical composite structural-acoustic system with multi-scale uncertain-but-bounded parameters. The corresponding formulations of the HIFEM are deduced. A subinterval technique is also introduced into the HIFEM for higher accuracy. Numerical examples of a hexahedral box and an automobile passenger compartment are given to demonstrate the efficiency of the presented method for a periodical composite structural-acoustic system with multi-scale uncertain-but-bounded parameters.

A highly printable and biocompatible hydrogel composite for direct printing of soft and perfusable vasculature-like structures.

PubMed

Suntornnond, Ratima; Tan, Edgar Yong Sheng; An, Jia; Chua, Chee Kai

2017-12-04

Vascularization is one major obstacle in bioprinting and tissue engineering. In order to create thick tissues or organs that can function like original body parts, the presence of a perfusable vascular system is essential. However, it is challenging to bioprint a hydrogel-based three-dimensional vasculature-like structure in a single step. In this paper, we report a new hydrogel-based composite that offers impressive printability, shape integrity, and biocompatibility for 3D bioprinting of a perfusable complex vasculature-like structure. The hydrogel composite can be used on a non-liquid platform and is printable at human body temperature. Moreover, the hydrogel composite supports both cell proliferation and cell differentiation. Our results represent a potentially new vascularization strategy for 3D bioprinting and tissue engineering.

Investigation of Structural Properties of Carbon-Epoxy Composites Using Embedded Fiber-Optic Bragg Gratings

NASA Technical Reports Server (NTRS)

Osei, Albert J.

2003-01-01

Real time monitoring of the mechanical integrity and stresses on key aerospace composite structures like aircraft wings, walls of pressure vessels and fuel tanks or any other structurally extended components and panels as in space telescopes is very important to NASA. Future military and commercial aircraft as well as NASA space systems such as Space Based Radar and International Space Station will incorporate a monitoring system to sense any degradation to the structure. In the extreme flight conditions of an aerospace vehicle it might be desirable to measure the strain every ten centimeters and thus fully map out the strain field of a composite component. A series of missions and vehicle health management requirements call for these measurements. At the moment thousands of people support a few vehicle launches per year. This number can be significantly reduced by implementing intelligent vehicles with integral nervous systems (smart structures). This would require maintenance to be performed only as needed. Military and commercial aircrafts have an equally compelling case. Annual maintenance costs are currently reaching astronomical heights. Monitoring techniques are therefore required that allow for maintenance to be performed only when needed. This would allow improved safety by insuring that necessary tasks are performed while reducing costs by eliminating procedures that are costly and not needed. The advantages fiber optical sensors have over conventional electro-mechanical systems like strain gauges have been widely extolled in the research literature. These advantages include their small size, low weight, immunity to electrical resistance, corrosion resistance, compatibility with composite materials and process conditions, and multiplexing capabilities. One fiber optic device which is suitable for distributed sensing is the fiber Bragg grating (FBG). This is a periodic perturbation in the refractive index of the fiber core. When a broadband light is coupled into the optical fiber sensor, a reflection peak will be obtained centered around a wavelength called Bragg-wavelength. The Bragg-wavelength depends on the refractive index and the period of the grating, which both change due to mechanical and thermal strain applied to the sensor. The shift in the Bragg-wavelength is directly proportional to the strain. Researchers at NASA MSFC are currently developing techniques for using FBGs for monitoring the integrity of advanced structural materials expected to become the mainstay of the current and future generation space structures. Since carbon-epoxy composites are the materials of choice for the current space structures, the initial study is concentrated on this type of composite. The goals of this activity are to use embedded FBG sensors for measuring strain and temperature of composite structures, and to investigate the effects of various parameters such as composite fiber orientation with respect to the optical sensor, unidirectional fiber composite, fabrication process etc., on the optical performance of the sensor. This paper describes an experiment to demonstrate the use of an embedded FBG for measuring strain in a composite material. The performance of the fiber optic sensor is determined by direct comparison with results from more conventional instrumentation.

Fracture mechanisms and fracture control in composite structures

NASA Astrophysics Data System (ADS)

Kim, Wone-Chul

Four basic failure modes--delamination, delamination buckling of composite sandwich panels, first-ply failure in cross-ply laminates, and compression failure--are analyzed using linear elastic fracture mechanics (LEFM) and the J-integral method. Structural failures, including those at the micromechanical level, are investigated with the aid of the models developed, and the critical strains for crack propagation for each mode are obtained. In the structural fracture analyses area, the fracture control schemes for delamination in a composite rib stiffener and delamination buckling in composite sandwich panels subjected to in-plane compression are determined. The critical fracture strains were predicted with the aid of LEFM for delamination and the J-integral method for delamination buckling. The use of toughened matrix systems has been recommended for improved damage tolerant design for delamination crack propagation. An experimental study was conducted to determine the onset of delamination buckling in composite sandwich panel containing flaws. The critical fracture loads computed using the proposed theoretical model and a numerical computational scheme closely followed the experimental measurements made on sandwich panel specimens of graphite/epoxy faceskins and aluminum honeycomb core with varying faceskin thicknesses and core sizes. Micromechanical models of fracture in composites are explored to predict transverse cracking of cross-ply laminates and compression fracture of unidirectional composites. A modified shear lag model which takes into account the important role of interlaminar shear zones between the 0 degree and 90 degree piles in cross-ply laminate is proposed and criteria for transverse cracking have been developed. For compressive failure of unidirectional composites, pre-existing defects play an important role. Using anisotropic elasticity, the stress state around a defect under a remotely applied compressive load is obtained. The experimentally observed complex compressive failure modes, such as shear crippling and pure compressive fiber failure of fibers are explained by the predicted stress distributions calculated in this work. These fracture analyses can be damage tolerant design methodology for composite structures. The proposed fracture criteria and the corresponding critical fracture strains provide the designer with quantitative guidelines for safe-life design. These have been incorporated into a fracture control plan for composite structures, which is also described. Currently, fracture control plans do not exist for composite structures; the proposed plan is a first step towards establishing fracture control and damage tolerant design methodology for this important class of materials.

Fiber Optic Sensors for Health Monitoring of Morphing Airframes. Part 1; Bragg Grating Strain and Temperature Sensor

NASA Technical Reports Server (NTRS)

Wood, Karen; Brown, Timothy; Rogowski, Robert; Jensen, Brian

2000-01-01

Fiber optic sensors are being developed for health monitoring of future aircraft. Aircraft health monitoring involves the use of strain, temperature, vibration and chemical sensors to infer integrity of the aircraft structure. Part 1 of this two part series describes sensors that will measure load and temperature signatures of these structures. In some cases a single fiber may be used for measuring these parameters. Part 2 will describe techniques for using optical fibers to monitor composite cure in real time during manufacture and to monitor in-service integrity of composite structures using a single fiber optic sensor capable of measuring multiple chemical and physical parameters. The facilities for fabricating optical fiber and associated sensors and the methods of demodulating Bragg gratings for strain measurement will be described.

Probabilistic Analysis of Large-Scale Composite Structures Using the IPACS Code

NASA Technical Reports Server (NTRS)

Lemonds, Jeffrey; Kumar, Virendra

1995-01-01

An investigation was performed to ascertain the feasibility of using IPACS (Integrated Probabilistic Assessment of Composite Structures) for probabilistic analysis of a composite fan blade, the development of which is being pursued by various industries for the next generation of aircraft engines. A model representative of the class of fan blades used in the GE90 engine has been chosen as the structural component to be analyzed with IPACS. In this study, typical uncertainties are assumed in the level, and structural responses for ply stresses and frequencies are evaluated in the form of cumulative probability density functions. Because of the geometric complexity of the blade, the number of plies varies from several hundred at the root to about a hundred at the tip. This represents a extremely complex composites application for the IPACS code. A sensitivity study with respect to various random variables is also performed.

Design of hat-stiffened composite panels loaded in axial compression

NASA Astrophysics Data System (ADS)

Paul, T. K.; Sinha, P. K.

An integrated step-by-step analysis procedure for the design of axially compressed stiffened composite panels is outlined. The analysis makes use of the effective width concept. A computer code, BUSTCOP, is developed incorporating various aspects of buckling such as skin buckling, stiffener crippling and column buckling. Other salient features of the computer code include capabilities for generation of data based on micromechanics theories and hygrothermal analysis, and for prediction of strength failure. Parametric studies carried out on a hat-stiffened structural element indicate that, for all practical purposes, composite panels exhibit higher structural efficiency. Some hybrid laminates with outer layers made of aluminum alloy also show great promise for flight vehicle structural applications.

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.

Simulations of carbon fiber composite delamination tests

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

Kay, G

2007-10-25

Simulations of mode I interlaminar fracture toughness tests of a carbon-reinforced composite material (BMS 8-212) were conducted with LSDYNA. The fracture toughness tests were performed by U.C. Berkeley. The simulations were performed to investigate the validity and practicality of employing decohesive elements to represent interlaminar bond failures that are prevalent in carbon-fiber composite structure penetration events. The simulations employed a decohesive element formulation that was verified on a simple two element model before being employed to perform the full model simulations. Care was required during the simulations to ensure that the explicit time integration of LSDYNA duplicate the near steady-statemore » testing conditions. In general, this study validated the use of employing decohesive elements to represent the interlaminar bond failures seen in carbon-fiber composite structures, but the practicality of employing the elements to represent the bond failures seen in carbon-fiber composite structures during penetration events was not established.« less

Degradation Factor Approach for Impacted Composite Structural Assessment: MSFC Center Director's Discretionary Fund Final Report, Project No. 96-17

NASA Technical Reports Server (NTRS)

Ortega, R.; Price, J. M.; Fox, D.

2000-01-01

This technical memorandum documents the results of the research to develop a concept for assessing the structural integrity of impacted composite structures using the strength degradation factor in conjunction with available finite element tools. For this purpose, a literature search was conducted, a plan for conducting impact testing on two laminates was developed, and a finite element model of the impact process was created. Specimens for the impact testing were fabricated to support the impact testing plan.

Manufacturing technology of integrated textile-based sensor networks for in situ monitoring applications of composite wind turbine blades

NASA Astrophysics Data System (ADS)

Haentzsche, Eric; Mueller, Ralf; Huebner, Matthias; Ruder, Tristan; Unger, Reimar; Nocke, Andreas; Cherif, Chokri

2016-10-01

Based on in situ strain sensors consisting of piezo-resistive carbon filament yarns (CFYs), which have been successfully integrated into textile reinforcement structures during their textile-technological manufacturing process, a continuous load of fibre-reinforced plastic (FRP) components has been realised. These sensors are also suitable for structural health monitoring (SHM) applications. The two-dimensional sensor layout is made feasible by the usage of a modular warp yarn path manipulation unit. Using a functional model of a small wind turbine blade in thermoset composite design, the sensor function for basic SHM applications (e.g. static load monitoring) are demonstrated. Any mechanical loads along the pressure or suction side of the wind turbine blade can be measured and calculated via a correlative change in resistance of the CFYs within the textile reinforcement plies. Performing quasi-static load tests on both tensile specimen and full-scale wind turbine blade, elementary results have been obtained concerning electro-mechanical behaviour and spatial resolution of global and even local static stresses according to the CFY sensor integration length. This paper demonstrates the great potential of textile-based and textile-technological integrated sensors in reinforcement structures for future SHM applications of FRPs.

SOFIP: A Short Orbital Flux Integration Program

NASA Technical Reports Server (NTRS)

Stassinopoulos, E. G.; Hebert, J. J.; Butler, E. L.; Barth, J. L.

1979-01-01

A computer code was developed to evaluate the space radiation environment encountered by geocentric satellites. The Short Orbital Flux Integration Program (SOFIP) is a compact routine of modular compositions, designed mostly with structured programming techniques in order to provide core and time economy and ease of use. The program in its simplest form produces for a given input trajectory a composite integral orbital spectrum of either protons or electrons. Additional features are available separately or in combination with the inclusion of the corresponding (optional) modules. The code is described in detail, and the function and usage of the various modules are explained. A program listing and sample outputs are attached.

Low-Cost Composite Materials and Structures for Aircraft Applications

NASA Technical Reports Server (NTRS)

Deo, Ravi B.; Starnes, James H., Jr.; Holzwarth, Richard C.

2003-01-01

A survey of current applications of composite materials and structures in military, transport and General Aviation aircraft is presented to assess the maturity of composites technology, and the payoffs realized. The results of the survey show that performance requirements and the potential to reduce life cycle costs for military aircraft and direct operating costs for transport aircraft are the main reasons for the selection of composite materials for current aircraft applications. Initial acquisition costs of composite airframe components are affected by high material costs and complex certification tests which appear to discourage the widespread use of composite materials for aircraft applications. Material suppliers have performed very well to date in developing resin matrix and fiber systems for improved mechanical, durability and damage tolerance performance. The next challenge for material suppliers is to reduce material costs and to develop materials that are suitable for simplified and inexpensive manufacturing processes. The focus of airframe manufacturers should be on the development of structural designs that reduce assembly costs by the use of large-scale integration of airframe components with unitized structures and manufacturing processes that minimize excessive manual labor.

Nanotechnology

NASA Technical Reports Server (NTRS)

Biaggi-Labiosa, Azlin

2016-01-01

Present an overview of the Nanotechnology Project at NASA's Game Changing Technology Industry Day. Mature and demonstrate flight readiness of CNT reinforced composites for future NASA mission applications?Sounding rocket test in a multiexperiment payload?Integrate into cold gas thruster system as propellant storage?The technology would provide the means for reduced COPV mass and improved damage tolerance and flight qualify CNT reinforced composites. PROBLEM/NEED BEING ADDRESSED:?Reduce weight and enhance the performance and damage tolerance of aerospace structuresGAME-CHANGING SOLUTION:?Improve mechanical properties of CNTs to eventually replace CFRP –lighter and stronger?First flight-testing of a CNT reinforced composite structural component as part of an operational flight systemUNIQUENESS:?CNT manufacturing methods developed?Flight qualify CNT reinforced composites

Effects of thermal cycling on composite materials for space structures

NASA Technical Reports Server (NTRS)

Tompkins, Stephen S.

1989-01-01

The effects of thermal cycling on the thermal and mechanical properties of composite materials that are candidates for space structures are briefly described. The results from a thermal analysis of the orbiting Space Station Freedom is used to define a typical thermal environment and the parameters that cause changes in the thermal history. The interactions of this environment with composite materials are shown and described. The effects of this interaction on the integrity as well as the properties of GR/thermoset, Gr/thermoplastic, Gr/metal and Gr/glass composite materials are discussed. Emphasis is placed on the effects of the interaction that are critical to precision spacecraft. Finally, ground test methodology are briefly discussed.

Society for the advancement of material and process engineering. 41st International SAMPE symposium and exhibition, Volume 41, Books 1 and 2

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

NONE

This document contains reports which were presented at the 41st International Society For The Advancement of Material and Process Engineering Symposium and Exhibition. Topics include: structural integrity of aging aircraft; composite materials development; affordable composites and processes; corrosion characterization of aging aircraft; adhesive advances; composite design; dual use materials and processing; repair of aircraft structures; adhesive inspection; materials systems for infrastructure; fire safety; composite impact/energy absorption; advanced materials for space; seismic retrofit; high temperature resins; preform technology; thermoplastics; alternative energy and transportation; manufacturing; and durability. Individual reports have been processed separately for the United States Department of Energy databases.

Photonic emitters and circuits based on colloidal quantum dot composites

NASA Astrophysics Data System (ADS)

Menon, Vinod M.; Husaini, Saima; Valappil, Nikesh; Luberto, Matthew

2009-02-01

We discuss our work on light emitters and photonic circuits realized using colloidal quantum dot composites. Specifically we will report our recent work on flexible microcavity laser, microdisk emitters and integrated active - passive waveguides. The entire microcavity laser structure was realized using spin coating and consisted of an all-polymer distributed Bragg reflector with a poly-vinyl carbazole cavity layer embedded with InGaP/ZnS colloidal quantum dots. These microcavities can be peeled off the substrate yielding a flexible structure that can conform to any shape and whose emission spectra can be mechanically tuned. The microdisk emitters and the integrated waveguide structures were realized using soft lithography and photo-lithography, respectively and were fabricated using a composite consisting of quantum dots embedded in SU8 matrix. Finally, we will discuss the effect of the host matrix on the optical properties of the quantum dots using results of steady-state and time-resolved luminescence measurements. In addition to their specific functionalities, these novel device demonstrations and their development present a low cost alternative to the traditional photonic device fabrication techniques.

Structures technology for a new generation of rotorcraft

NASA Technical Reports Server (NTRS)

Bartlett, Felton D., Jr.

1989-01-01

This paper presents an overview of structures research at the U. S. Army Aerostructures Directorate. The objectives of this research are to investigate, explore, and demonstrate emerging technologies that will provide lighter, safer, more survivable, and more cost-effective structures for rotorcraft in the 1990s and beyond. The emphasis of today's R&D is to contribute proven structures technology to the U. S. rotorcraft industry and Army aviation that directly impacts tomorrow's fleet readiness and mission capabilities. The primary contributor toward meeting these challenges is the development of high-strength and durable composites to minimize structural weight while maximizing cost effectiveness. Special aviation issues such as delamination of dynamic components, impact damage to thin skins, crashworthiness, and affordable manufacturing need to be resolved before the full potential of composites technology can be realized. To that end, this paper highlights research into composites structural integrity, crashworthiness, and materials applications which addresses these issues.

Active Control Technology at NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Antcliff, Richard R.; McGowan, Anna-Marie R.

2000-01-01

NASA Langley has a long history of attacking important technical Opportunities from a broad base of supporting disciplines. The research and development at Langley in this subject area range from the test tube to the test flight, The information covered here will range from the development of innovative new materials, sensors and actuators, to the incorporation of smart sensors and actuators in practical devices, to the optimization of the location of these devices, to, finally, a wide variety of applications of these devices utilizing Langley's facilities and expertise. Advanced materials are being developed for sensors and actuators, as well as polymers for integrating smart devices into composite structures. Contributions reside in three key areas: computational materials; advanced piezoelectric materials; and integrated composite structures.

Tooling Foam for Structural Composite Applications

NASA Technical Reports Server (NTRS)

DeLay, Tom; Smith, Brett H.; Ely, Kevin; MacArthur, Doug

1998-01-01

Tooling technology applications for composite structures fabrication have been expanded at MSFC's Productivity Enhancement Complex (PEC). Engineers from NASA/MSFC and Lockheed Martin Corporation have developed a tooling foam for use in composite materials processing and manufacturing that exhibits superior thermal and mechanical properties in comparison with other tooling foam materials. This tooling foam is also compatible with most preimpregnated composite resins such as epoxy, bismaleimide, phenolic and their associated cure cycles. MARCORE tooling foam has excellent processability for applications requiring either integral or removable tooling. It can also be tailored to meet the requirements for composite processing of parts with unlimited cross sectional area. A shelf life of at least six months is easily maintained when components are stored between 50F - 70F. The MARCORE tooling foam system is a two component urethane-modified polyisocyanurate, high density rigid foam with zero ozone depletion potential. This readily machineable, lightweight tooling foam is ideal for composite structures fabrication and is dimensionally stable at temperatures up to 350F and pressures of 100 psi.

EFFECTS OF TEMPERATURE AND ENVIRONMENT ON MECHANICAL PROPERTIES OF TWO CHOPPED-FIBER AUTOMOTIVE STRUCTURAL COMPOSITES

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

Ruggles-Wrenn, M.B.

2003-10-06

The Durability of Lightweight Composite Structures Project was established at Oak Ridge National Laboratory (ORNL) by the U.S. Department of Energy to provide the experimentally-based, durability-driven design guidelines necessary to assure long-term structural integrity of automotive composite components. The initial focus of the ORNL Durability Project was on composite materials consisting of polyurethane reinforced with E-glass. Current focus of the project is on composite materials reinforced with carbon fibers. The primary purpose of this report is to provide the individual specimen test date. Basic mechanical property testing and results for two chopped-fiber composite materials, one reinforced with glass- and themore » other with carbon fiber are provided. Both materials use the same polyurethane matrix. Preforms for both materials were produced using the P4 process. Behavioral trends, effects of temperature and environment, and corresponding design knockdown factors are established for both materials. Effects of prior short-time loads and of prior thermal cycling are discussed.« less

Lightning Strike Ablation Damage Influence Factors Analysis of Carbon Fiber/Epoxy Composite Based on Coupled Electrical-Thermal Simulation

NASA Astrophysics Data System (ADS)

Yin, J. J.; Chang, F.; Li, S. L.; Yao, X. L.; Sun, J. R.; Xiao, Y.

2017-10-01

According to the mathematical analysis model constructed on the basis of energy-balance relationship in lightning strike, and accompany with the simplified calculation strategy of composite resin pyrolysis degree dependent electrical conductivity, an effective three dimensional thermal-electrical coupling analysis finite element model of composite laminate suffered from lightning current was established based on ABAQUS, to elucidate the effects of lighting current waveform parameters and thermal/electrical properties of composite laminate on the extent of ablation damage. Simulated predictions agree well with the composite lightning strike directed effect experimental data, illustrating the potential accuracy of the constructed model. The analytical results revealed that extent of composite lightning strike ablation damage can be characterized by action integral validly, there exist remarkable power function relationships between action integral and visual damage area, projected damage area, maximum damage depth and damage volume of ablation damage, and enhancing the electrical conductivity and specific heat of composite, ablation damage will be descended obviously, power function relationships also exist between electrical conductivity, specific heat and ablation damage, however, the impact of thermal conductivity on the extent of ablation damage is not notable. The conclusions obtained provide some guidance for composite anti-lightning strike structure-function integration design.

On finite element implementation and computational techniques for constitutive modeling of high temperature composites

NASA Technical Reports Server (NTRS)

Saleeb, A. F.; Chang, T. Y. P.; Wilt, T.; Iskovitz, I.

1989-01-01

The research work performed during the past year on finite element implementation and computational techniques pertaining to high temperature composites is outlined. In the present research, two main issues are addressed: efficient geometric modeling of composite structures and expedient numerical integration techniques dealing with constitutive rate equations. In the first issue, mixed finite elements for modeling laminated plates and shells were examined in terms of numerical accuracy, locking property and computational efficiency. Element applications include (currently available) linearly elastic analysis and future extension to material nonlinearity for damage predictions and large deformations. On the material level, various integration methods to integrate nonlinear constitutive rate equations for finite element implementation were studied. These include explicit, implicit and automatic subincrementing schemes. In all cases, examples are included to illustrate the numerical characteristics of various methods that were considered.

Preliminary Structural Sizing and Alternative Material Trade Study of CEV Crew Module

NASA Technical Reports Server (NTRS)

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

2007-01-01

This paper presents the results of a preliminary structural sizing and alternate material trade study for NASA s Crew Exploration Vehicle (CEV) Crew Module (CM). This critical CEV component will house the astronauts during ascent, docking with the International Space Station, reentry, and landing. The alternate material design study considers three materials beyond the standard metallic (aluminum alloy) design that resulted from an earlier NASA Smart Buyer Team analysis. These materials are graphite/epoxy composite laminates, discontinuously reinforced SiC/Al (DRA) composites, and a novel integrated panel material/concept known as WebCore. Using the HyperSizer (Collier Research and Development Corporation) structural sizing software and NASTRAN finite element analysis code, a comparison is made among these materials for the three composite CM concepts considered by the 2006 NASA Engineering and Safety Center Composite Crew Module project.

Fatigue behavior and life prediction of a SiC/Ti-24Al-11Nb composite under isothermal conditions. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bartolotta, Paul A.

1991-01-01

Metal Matrix Composites (MMC) and Intermetallic Matrix Composites (IMC) were identified as potential material candidates for advanced aerospace applications. They are especially attractive for high temperature applications which require a low density material that maintains its structural integrity at elevated temperatures. High temperature fatigue resistance plays an important role in determining the structural integrity of the material. This study attempts to examine the relevance of test techniques, failure criterion, and life prediction as they pertain to an IMC material, specifically, unidirectional SiC fiber reinforced titanium aluminide. A series of strain and load controlled fatigue tests were conducted on unidirectional SiC/Ti-24Al-11Nb composite at 425 and 815 C. Several damage mechanism regimes were identified by using a strain-based representation of the data, Talreja's fatigue life diagram concept. Results of these tests were then used to address issues of test control modes, definition of failure, and testing techniques. Finally, a strain-based life prediction method was proposed for an IMC under tensile cyclic loadings at elevated temperatures.

Raman spectroscopic investigations on natural samples from the Integrated Ocean Drilling Program (IODP) Expedition 311: indications for heterogeneous compositions in hydrate crystals.

PubMed

Schicks, J M; Ziemann, M A; Lu, H; Ripmeester, J A

2010-12-01

Natural gas hydrates usually are found in the form of structure I, encasing predominantly methane in the hydrate lattices as guest molecules, sometimes also minor amount of higher hydrocarbons, CO2 or H2S. Raman spectroscopy is an approved tool to determine the composition of the hydrate phase. Thus, in this study Raman spectroscopic analyses have been applied to hydrate samples obtained from Integrated Ocean Drilling Program (IODP) Expedition 311 in two different approaches: studying the samples randomly taken from the hydrate core, and--as a new application--mapping small areas on the surface of clear hydrate crystals. The results obtained imply that the gas composition of hydrate, in terms of relative concentrations of CH4 and H2S, is not homogeneous over a core or even within a crystal. The mapping method yielded results with very high lateral resolution, indicating the coexistence of different phases with the same structure but different compositions within a hydrate crystal. Copyright © 2010 Elsevier B.V. All rights reserved.

Synthesis of aircraft structures using integrated design and analysis methods

NASA Technical Reports Server (NTRS)

Sobieszczanski-Sobieski, J.; Goetz, R. C.

1978-01-01

A systematic research is reported to develop and validate methods for structural sizing of an airframe designed with the use of composite materials and active controls. This research program includes procedures for computing aeroelastic loads, static and dynamic aeroelasticity, analysis and synthesis of active controls, and optimization techniques. Development of the methods is concerned with the most effective ways of integrating and sequencing the procedures in order to generate structural sizing and the associated active control system, which is optimal with respect to a given merit function constrained by strength and aeroelasticity requirements.

Quiet Clean Short-haul Experimental Engine (QCSEE) Under-The-Wing (UTW) composite nacelle subsystem test report. [to verify strength of selected composite materials

NASA Technical Reports Server (NTRS)

Stotler, C. L., Jr.; Johnston, E. A.; Freeman, D. S.

1977-01-01

The element and subcomponent testing conducted to verify the under the wing composite nacelle design is reported. This composite nacelle consists of an inlet, outer cowl doors, inner cowl doors, and a variable fan nozzle. The element tests provided the mechanical properties used in the nacelle design. The subcomponent tests verified that the critical panel and joint areas of the nacelle had adequate structural integrity.

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

Jason Maung, K.; Hahn, H. Thomas; Ju, Y.S.

Multifunction integration of solar cells in load-bearing structures can enhance overall system performance by reducing parasitic components and material redundancy. The article describes a manufacturing strategy, named the co-curing scheme, to integrate thin-film silicon solar cells on carbon-fiber-reinforced epoxy composites and eliminate parasitic packaging layers. In this scheme, an assembly of a solar cell and a prepreg is cured to form a multifunctional composite in one processing step. The photovoltaic performance of the manufactured structures is then characterized under controlled cyclic mechanical loading. The study finds that the solar cell performance does not degrade under 0.3%-strain cyclic tension loading upmore » to 100 cycles. Significant degradation, however, is observed when the magnitude of cyclic loading is increased to 1% strain. The present study provides an initial set of data to guide and motivate further studies of multifunctional energy harvesting structures. (author)« less

Advanced Technology Composite Fuselage - Repair and Damage Assessment Supporting Maintenance

NASA Technical Reports Server (NTRS)

Flynn, B. W.; Bodine, J. B.; Dopker, B.; Finn, S. R.; Griess, K. H.; Hanson, C. T.; Harris, C. G.; Nelson, K. M.; Walker, T. H.; Kennedy, T. C.;

Damping Experiment of Spinning Composite Plates with Embedded Viscoelastic Material

NASA Technical Reports Server (NTRS)

Mehmed, Oral; Kosmatka, John B.

1997-01-01

One way to increase gas turbine engine blade reliability and durability is to reduce blade vibration. It is well known that vibration reduction can be achieved by adding damping to metal and composite blade-disk systems. This experiment was done to investigate the use of integral viscoelastic damping treatments to reduce vibration of rotating composite fan blades. It is part of a joint research effort with NASA LeRC and the University of California, San Diego (UCSD). Previous vibration bench test results obtained at UCSD show that plates with embedded viscoelastic material had over ten times greater damping than similar untreated plates; and this was without a noticeable change in blade stiffness. The objectives of this experiment, were to verify the structural integrity of composite plates with viscoelastic material embedded between composite layers while under large steady forces from spinning, and to measure the damping and natural frequency variation with rotational speed.

Advanced stitching technology

NASA Technical Reports Server (NTRS)

Scardino, Frank L.

1992-01-01

In the design of textile composites, the selection of materials and constructional techniques must be matched with product performance, productivity, and cost requirements. Constructional techniques vary. A classification of various textile composite systems is given. In general, the chopped fiber system is not suitable for structural composite applications because of fiber discontinuity, uncontrolled fiber orientation and a lack of fiber integration or entanglement. Linear filament yarn systems are acceptable for structural components which are exposed to simple tension in their applications. To qualify for more general use as structural components, filament yarn systems must be multi-directionally positioned. With the most sophisticated filament winding and laying techniques, however, the Type 2 systems have limited potential for general load-bearing applications because of a lack of filament integration or entanglement, which means vulnerability to splitting and delamination among filament layers. The laminar systems (Type 3) represented by a variety of simple fabrics (woven, knitted, braided and nonwoven) are especially suitable for load-bearing panels in flat form and for beams in a roled up to wound form. The totally integrated, advanced fabric system (Type 4) are thought to be the most reliable for general load-bearing applications because of fiber continuity and because of controlled multiaxial fiber orientation and entanglement. Consequently, the risk of splitting and delamination is minimized and practically omitted. Type 4 systems can be woven, knitted, braided or stitched through with very special equipment. Multiaxial fabric technologies are discussed.

Method and apparatus for evaluating structural weakness in polymer matrix composites

DOEpatents

Wachter, E.A.; Fisher, W.G.

1996-01-09

A method and apparatus for evaluating structural weaknesses in polymer matrix composites is described. An object to be studied is illuminated with laser radiation and fluorescence emanating therefrom is collected and filtered. The fluorescence is then imaged and the image is studied to determine fluorescence intensity over the surface of the object being studied and the wavelength of maximum fluorescent intensity. Such images provide a map of the structural integrity of the part being studied and weaknesses, particularly weaknesses created by exposure of the object to heat, are readily visible in the image. 6 figs.

Method and apparatus for evaluating structural weakness in polymer matrix composites

DOEpatents

Wachter, Eric A.; Fisher, Walter G.

1996-01-01

A method and apparatus for evaluating structural weaknesses in polymer matrix composites is described. An object to be studied is illuminated with laser radiation and fluorescence emanating therefrom is collected and filtered. The fluorescence is then imaged and the image is studied to determine fluorescence intensity over the surface of the object being studied and the wavelength of maximum fluorescent intensity. Such images provide a map of the structural integrity of the part being studied and weaknesses, particularly weaknesses created by exposure of the object to heat, are readily visible in the image.

Composite sizing and ply orientation for stiffness requirements using a large finite element structural model

NASA Technical Reports Server (NTRS)

Radovcich, N. A.; Gentile, D. P.

1989-01-01

A NASTRAN bulk dataset preprocessor was developed to facilitate the integration of filamentary composite laminate properties into composite structural resizing for stiffness requirements. The NASCOMP system generates delta stiffness and delta mass matrices for input to the flutter derivative program. The flutter baseline analysis, derivative calculations, and stiffness and mass matrix updates are controlled by engineer defined processes under an operating system called CBUS. A multi-layered design variable grid system permits high fidelity resizing without excessive computer cost. The NASCOMP system uses ply layup drawings for basic input. The aeroelastic resizing for stiffness capability was used during an actual design exercise.

ISAAC - A Testbed for Advanced Composites Research

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey; Stewart, Brian K.; Martin, Robert A.

2014-01-01

The NASA Langley Research Center is acquiring a state-of-art composites fabrication environment to support the Center's research and technology development mission. This overall system described in this paper is named ISAAC, or Integrated Structural Assembly of Advanced Composites. ISAAC's initial operational capability is a commercial robotic automated fiber placement system from Electroimpact, Inc. that consists of a multi-degree of freedom commercial robot platform, a tool changer mechanism, and a specialized automated fiber placement end effector. Examples are presented of how development of advanced composite materials, structures, fabrication processes and technology are enabled by utilizing the fiber placement end effector directly or with appropriate modifications. Alternatively, end effectors with different capabilities may either be bought or developed with NASA's partners in industry and academia.

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.

Nanocomposites for Enhanced Structural Integrity

DTIC Science & Technology

2007-09-11

Yong and H.T. Hahn, "Kevlar/Vinyl Ester Composites with SiC Nanoparticles ," SAMPE 2004 Proc. ( CD ROM), May 2004. C-6. M. Lui and H.T. Hahn...34 Nanoparticle -Based Mitigation of fiber Print-Through in Composite Mirrors," Proc. American Society for Composites, 20’h Technical Conference ( CD ROM), Sept. 2005...the graphene layers. Microwave radiation aids in drying and results in further separation of the sheets. Thermogravimetric analysis indicates that the

Structural health monitoring and impact detection for primary aircraft structures

NASA Astrophysics Data System (ADS)

Kosters, Eric; van Els, Thomas J.

2010-04-01

The increasing use of thermoplastic carbon fiber-reinforced plastic (CFRP) materials in the aerospace industry for primary aircraft structures, such as wing leading-edge surfaces and fuselage sections, has led to rapid growth in the field of structural health monitoring (SHM). Impact, vibration, and load can all cause failure, such as delamination and matrix cracking, in composite materials. Moreover, the internal material damage can occur without being visible to the human eye, making inspection of and clear insight into structural integrity difficult using currently available evaluation methods. Here, we describe the detection of impact and its localization in materials and structures by high-speed interrogation of multiple-fiber Bragg grating (FBG) sensors mounted on a composite aircraft component.

High Temperature Aerogels for Thermal Protection Systems

NASA Technical Reports Server (NTRS)

Hurwitz, Frances I.; Mbah, Godfrey C.

2008-01-01

High temperature aerogels in the Al2O3-SiO2 system are being investigated as possible constituents for lightweight integrated thermal protection system (TPS) designs for use in supersonic and hypersonic applications. Gels are synthesized from ethoxysilanes and AlCl3.6H2O, using an epoxide catalyst. The influence of Al:Si ratio, solvent, water to metal and water to alcohol ratios on aerogel composition, morphology, surface area, and pore size distribution were examined, and phase transformation on heat treatment characterized. Aerogels have been fabricated which maintain porous, fractal structures after brief exposures to 1000 C. Incorporation of nanofibers, infiltration of aerogels into SiC foams, use of polymers for crosslinking the aerogels, or combinations of these, offer potential for toughening and integration of TPS with composite structure. Woven fabric composites having Al2O3-SiO2 aerogels as a matrix also have been fabricated. Continuing work is focused on reduction in shrinkage and optimization of thermal and physical properties.

Graphitic design: prospects of graphene-based nanocomposites for solar energy conversion, storage, and sensing.

PubMed

Lightcap, Ian V; Kamat, Prashant V

2013-10-15

Graphene not only possesses interesting electrochemical behavior but also has a remarkable surface area and mechanical strength and is naturally abundant, all advantageous properties for the design of tailored composite materials. Graphene-semiconductor or -metal nanoparticle composites have the potential to function as efficient, multifunctional materials for energy conversion and storage. These next-generation composite systems could possess the capability to integrate conversion and storage of solar energy, detection, and selective destruction of trace environmental contaminants or achieve single-substrate, multistep heterogeneous catalysis. These advanced materials may soon become a reality, based on encouraging results in the key areas of energy conversion and sensing using graphene oxide as a support structure. Through recent advances, chemists can now integrate such processes on a single substrate while using synthetic designs that combine simplicity with a high degree of structural and composition selectivity. This progress represents the beginning of a transformative movement leveraging the advancements of single-purpose chemistry toward the creation of composites designed to address whole-process applications. The promising field of graphene nanocomposites for sensing and energy applications is based on fundamental studies that explain the electronic interactions between semiconductor or metal nanoparticles and graphene. In particular, reduced graphene oxide is a suitable composite substrate because of its two-dimensional structure, outstanding surface area, and electrical conductivity. In this Account, we describe common assembly methods for graphene composite materials and examine key studies that characterize its excited state interactions. We also discuss strategies to develop graphene composites and control electron capture and transport through the 2D carbon network. In addition, we provide a brief overview of advances in sensing, energy conversion, and storage applications that incorporate graphene-based composites. With these results in mind, we can envision a new class of semiconductor- or metal-graphene composites sensibly tailored to address the pressing need for advanced energy conversion and storage devices.

Multi-Functional Sandwich Composites for Spacecraft Applications: An Initial Assessment

NASA Technical Reports Server (NTRS)

Adams, Daniel O.; Webb, Nicholas Jason; Yarger, Cody B.; Hunter, Abigail; Oborn, Kelli D.

2007-01-01

Current spacecraft implement relatively uncoupled material and structural systems to address a variety of design requirements, including structural integrity, damage tolerance, radiation protection, debris shielding and thermal insulation. This investigation provided an initial assessment of multi-functional sandwich composites to integrate these diverse requirements. The need for radiation shielding was addressed through the selection of polymeric constituents with high hydrogen content. To provide increased damage tolerance and debris shielding, manufacturing techniques were developed to incorporate transverse stitching reinforcement, internal layers, and a self-healing ionomer membrane. To assess the effects of a space environment, thermal expansion behavior of the candidate foam materials was investigated under a vacuum and increasing temperature. Finally, a thermal expansion model was developed for foam under vacuum conditions and its predictive capability assessed.

Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 2: Structural fatigue, thermal cycling, creep, and residual strength

NASA Technical Reports Server (NTRS)

Blichfeldt, B.; Mccarty, J. E.

1972-01-01

Specimens representative of metal aircraft structural components reinforced with boron filamentary composites were manufactured and tested under cyclic loading, cyclic temperature, or continuously applied loading to evaluate some of the factors that affect structural integrity under cyclic conditions. Bonded, stepped joints were used throughout to provide composite-to-metal transition regions at load introduction points. Honeycomb panels with titanium or aluminum faces reinforced with unidirectional boron composite were fatigue tested at constant amplitude under completely reversed loading. Results indicated that the matrix material was the most fatigue-sensitive part of the design, with debonding initiating in the stepped joints. However, comparisons with equal weight all-metal specimens show a 10 to 50 times improved fatigue life. Fatigue crack propagation and residual strength were studied for several different stiffened panel concepts, and were found to vary considerably depending on the configuration. Composite-reinforced metal specimens were also subjected to creep and thermal cycling tests. Thermal cycling of stepped joint tensile specimens resulted in a ten percent decrease in residual strength after 4000 cycles.

Integrating Mass Spectrometry of Intact Protein Complexes into Structural Proteomics

PubMed Central

Hyung, Suk-Joon; Ruotolo, Brandon T.

2013-01-01

Summary Mass spectrometry analysis of intact protein complexes has emerged as an established technology for assessing the composition and connectivity within dynamic, heterogeneous multiprotein complexes at low concentrations and in the context of mixtures. As this technology continues to move forward, one of the main challenges is to integrate the information content of such intact protein complex measurements with other mass spectrometry approaches in structural biology. Methods such as H/D exchange, oxidative foot-printing, chemical cross-linking, affinity purification, and ion mobility separation add complementary information that allows access to every level of protein structure and organization. Here, we survey the structural information that can be retrieved by such experiments, demonstrate the applicability of integrative mass spectrometry approaches in structural proteomics, and look to the future to explore upcoming innovations in this rapidly-advancing area. PMID:22611037

Integrated aerodynamic-structural design of a forward-swept transport wing

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.; Grossman, Bernard; Kao, Pi-Jen; Polen, David M.; Sobieszczanski-Sobieski, Jaroslaw

1989-01-01

The introduction of composite materials is having a profound effect on aircraft design. Since these materials permit the designer to tailor material properties to improve structural, aerodynamic and acoustic performance, they require an integrated multidisciplinary design process. Futhermore, because of the complexity of the design process, numerical optimization methods are required. The utilization of integrated multidisciplinary design procedures for improving aircraft design is not currently feasible because of software coordination problems and the enormous computational burden. Even with the expected rapid growth of supercomputers and parallel architectures, these tasks will not be practical without the development of efficient methods for cross-disciplinary sensitivities and efficient optimization procedures. The present research is part of an on-going effort which is focused on the processes of simultaneous aerodynamic and structural wing design as a prototype for design integration. A sequence of integrated wing design procedures has been developed in order to investigate various aspects of the design process.

FIBER AND INTEGRATED OPTICS: Photodetector waveguide structures made of epitaxial InGaAs films and intended for integrated circuits manufactured from III-V semiconductor compounds

NASA Astrophysics Data System (ADS)

Shmal'ko, A. V.; Lamekin, V. F.; Smirnov, V. L.; Polyantsev, A. S.; Kogan, Yu I.; Babushkina, T. S.; Kuntsevich, T. S.; Peshkovskaya, O. G.

1990-08-01

Photodetector waveguide structures made of epitaxial InxGa1 - xAs solid-solution films were developed and investigated. These structures were intended for optical integrated circuits manufactured from III-V semiconductor compounds for operation in the wavelength range 1.0-1.5 μm. Two types of photodetector waveguide p-i-n structures were developed. They consisted of a composite waveguide and tunnel-coupled waveguides, respectively. A study was made of structural parameters, responsivity, spectral and time characteristics, and dark currents in photodetectors made of the waveguide structures. This investigation was carried out in the wavelength range 1.0-1.3 μm. The maximum spectral responsivity of one of the types of the waveguide photodetector was ~ 0.5 ± 0.1 A/W and the dark current did not exceed 10 - 7-10 - 8 A.

Structural Integrity Evaluation of the Lear Fan 2100 Aircraft

NASA Technical Reports Server (NTRS)

Kan, H. P.; Dyer, T. A.

1996-01-01

An in-situ nondestructive inspection was conducted to detect manufacturing and assembly induced defects in the upper two wing surfaces (skin s) and upper fuselage skin of the Lear Fan 2100 aircraft E009. The effects of the defects, detected during the inspection, on the integrity of the structure was analytically evaluated. A systematic evaluation was also conducted to determine the damage tolerance capability of the upper wing skin against impact threats and assembly induced damage. The upper wing skin was divided into small regions for damage tolerance evaluations. Structural reliability, margin of safety, allowable strains, and allowable damage size were computed. The results indicated that the impact damage threat imposed on composite military aircraft structures is too severe for the Lear Fan 2100 upper wing skin. However, the structural integrity is not significantly degraded by the assembly induced damage for properly assembled structures, such as the E009 aircraft.

Single-walled carbon nanotubes/polymer composite electrodes patterned directly from solution.

PubMed

Chang, Jingbo; Najeeb, Choolakadavil Khalid; Lee, Jae-Hyeok; Kim, Jae-Ho

2011-06-07

This work describes a simple technique for direct patterning of single-walled carbon nanotube (SWNT)/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) composite electrodes in a large area on a substrate based on the solution transfer process by microcontact printing using poly(dimethylsiloxane) (PDMS) stamps. Various shapes of SWNT/PEDOT-PSS composite patterns, such as line, circle, and square, can be easily fabricated with high pattern fidelity and structural integrity. The single parallel line pattern device exhibits high electrical conductivity (0.75 × 10(5) S/m) and electronic stability because of alignment of nanotubes and big-size SWNT bundles (∼5 nm). The electromechanical study reveals that the composite patterns show ∼1% resistance change along SWNT alignment direction and ∼5% resistance change along vertical alignment direction after 200 bend cycles. Our approach provides a facile, low-cost method to pattern transparent conductive SWNT/polymer composite electrodes and demonstrates a novel platform for future integration of conducting SWNT/polymer composite patterns for optoelectronic applications.

A Framework for Performing Multiscale Stochastic Progressive Failure Analysis of Composite Structures

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2006-01-01

A framework is presented that enables coupled multiscale analysis of composite structures. The recently developed, free, Finite Element Analysis - Micromechanics Analysis Code (FEAMAC) software couples the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) with ABAQUS to perform micromechanics based FEA such that the nonlinear composite material response at each integration point is modeled at each increment by MAC/GMC. As a result, the stochastic nature of fiber breakage in composites can be simulated through incorporation of an appropriate damage and failure model that operates within MAC/GMC on the level of the fiber. Results are presented for the progressive failure analysis of a titanium matrix composite tensile specimen that illustrate the power and utility of the framework and address the techniques needed to model the statistical nature of the problem properly. In particular, it is shown that incorporating fiber strength randomness on multiple scales improves the quality of the simulation by enabling failure at locations other than those associated with structural level stress risers.

A Framework for Performing Multiscale Stochastic Progressive Failure Analysis of Composite Structures

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Arnold, Steven M.

2007-01-01

A framework is presented that enables coupled multiscale analysis of composite structures. The recently developed, free, Finite Element Analysis-Micromechanics Analysis Code (FEAMAC) software couples the Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) with ABAQUS to perform micromechanics based FEA such that the nonlinear composite material response at each integration point is modeled at each increment by MAC/GMC. As a result, the stochastic nature of fiber breakage in composites can be simulated through incorporation of an appropriate damage and failure model that operates within MAC/GMC on the level of the fiber. Results are presented for the progressive failure analysis of a titanium matrix composite tensile specimen that illustrate the power and utility of the framework and address the techniques needed to model the statistical nature of the problem properly. In particular, it is shown that incorporating fiber strength randomness on multiple scales improves the quality of the simulation by enabling failure at locations other than those associated with structural level stress risers.

Impedance Based Detection of Delamination in Composite Structures

NASA Astrophysics Data System (ADS)

Djemana, M.; Hrairi, M.

2017-03-01

Nowadays commercial and military aircrafts are increasingly using composite materials to take advantage of their excellent specific strength and stiffness properties but impacts on composites due to bird-strike, hail-storm cause barely visible impact damage (BVID) that underscores the need for robust structural health monitoring methods. Hence, damage identification in composite materials is a widely researched area that has to deal with problems coming from the anisotropic nature of composites and the fact that much of the damage occurs beneath the top surface of the laminate. This paper focuses on understanding self-sensing piezoelectric wafer active sensors (PWAS) to conduct electromechanical impedance (EMI) in glass fibre reinforced polymer composite to perform structural health monitoring. With the aid of a 3D ANSYS finite element model, an analysis of different techniques for the detection of position and size of a delamination in a composite structure using piezoelectric patches had been performed. The real part of the impedance is used because it is known to be more reactive to damage or changes in the structure’s integrity and less sensitive to ambient temperature changes compared to the imaginary part. Comparison with experimental results is presented to validate the FE results. The experimental setup utilizes as its main apparatus an impedance analyser HP4194 that reads the in-situ EMI of PWAS bonded to the monitored composite structure. A good match between experimental and numerical results has been observed for low and high frequencies. The analysis in this paper provides necessary basis for delamination detection in composite structures using EMI technique

Effect of impregnation pressure and time on the porosity, structure and properties of polyacrylonitrile-fiber based carbon composites

NASA Astrophysics Data System (ADS)

Venugopalan, Ramani; Roy, Mainak; Thomas, Susy; Patra, A. K.; Sathiyamoorthy, D.; Tyagi, A. K.

2013-02-01

Carbon-carbon composites may find applications in critical parts of advanced nuclear reactors. A series of carbon-carbon composites were prepared using polyacrylonitrile (PAN) based carbon fibers. The materials were densified by impregnating two-dimensional (2D) preforms with liquid phenol formaldehyde resin at different pressures and for different periods of time and then carbonizing those by slowly heating at 1000 °C. Effects of the processing parameters on the structure of the composites were extensively studied. The study showed conclusively that open porosity decreased with increasing impregnation pressure, whereas impregnation time had lesser effect. Matrix-resin bonding also improved at higher pressure. d002 spacing decreased and ordering along c-axis increased with concomitant increase in sp2-carbon fraction at higher impregnation pressures. The fiber reinforced composites exhibited short range ordering of carbon atoms and satisfied structural conditions (d002 values) of amorphous carbon according to the turbostratic model for non-graphitic carbon materials. The composites had pellet-density of ˜85% of the theoretical value, low thermal expansion and negligible neutron-poisoning. They maintained structural integrity and retained disordered nature even on heat-treatment at ca. 1800 °C.

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.

Fuel containment and damage tolerance in large composite primary aircraft structures. Phase 2: Testing

NASA Technical Reports Server (NTRS)

Sandifer, J. P.; Denny, A.; Wood, M. A.

1985-01-01

Technical issues associated with fuel containment and damage tolerance of composite wing structures for transport aircraft were investigated. Material evaluation tests were conducted on two toughened resin composites: Celion/HX1504 and Celion/5245. These consisted of impact, tension, compression, edge delamination, and double cantilever beam tests. Another test series was conducted on graphite/epoxy box beams simulating a wing cover to spar cap joint configuration of a pressurized fuel tank. These tests evaluated the effectiveness of sealing methods with various fastener types and spacings under fatigue loading and with pressurized fuel. Another test series evaluated the ability of the selected coatings, film, and materials to prevent fuel leakage through 32-ply AS4/2220-1 laminates at various impact energy levels. To verify the structural integrity of the technology demonstration article structural details, tests were conducted on blade stiffened panels and sections. Compression tests were performed on undamaged and impacted stiffened AS4/2220-1 panels and smaller element tests to evaluate stiffener pull-off, side load and failsafe properties. Compression tests were also performed on panels subjected to Zone 2 lightning strikes. All of these data were integrated into a demonstration article representing a moderately loaded area of a transport wing. This test combined lightning strike, pressurized fuel, impact, impact repair, fatigue and residual strength.

Carbon nanotube-embedded advanced aerospace composites for early-stage damage sensing

NASA Astrophysics Data System (ADS)

Nataraj, Latha; Coatney, Michael; Cain, Jason; Hall, Asha

2018-03-01

Fiber reinforced polymer (FRP) composites featuring outstanding fatigue performance, high specific stiffness and strength, and low density have evolved as critical structural materials in aerospace applications. Microscale damage such as fiber breakage, matrix cracking, and delamination could occur in layered composites compromising structural integrity, emphasizing the critical need to monitor structural health. Early damage detection would lead to enhanced reliability, lifetime, and performance while minimizing maintenance time, leading to enormous scientific and technical interest in realizing physically stable, quick responding, and cost effective strain sensing materials, devices, and techniques with high sensitivity over a broad range of the practical strain spectrum. Today's most commonly used strain sensing techniques are metal foil strain gauges and optical fiber sensors. Metal foil gauges offer high stability and cost-effectiveness but can only be surface-mounted and have a low gauge factor. Optical fibers require expensive instrumentation, are mostly insensitive to cracks parallel to the fiber orientation and may lead to crack initiation as the diameter is larger than that of the reinforcement fibers. Carbon nanotubes (CNTs) have attracted much attention due to high aspect ratio and superior electrical, thermal, and mechanical properties. CNTs embedded in layered composites have improved performance. A variety of CNT architectures and configurations have shown improved piezoresistive behavior and stability for sensing applications. However, scaling up and commercialization remain serious challenges. The current study investigates a simple, cost effective and repeatable technique for highly sensitive, stable, linear and repeatable strain sensing for damage detection by integrating CNT laminates into composites.

Titanium and advanced composite structures for a supersonic cruise arrow wing configuration

NASA Technical Reports Server (NTRS)

Turner, M. J.; Hoy, J. M.

1976-01-01

Structural design studies were made, based on current technology and on an estimate of technology to be available in the mid 1980's, to assess the relative merits of structural concepts and materials for an advanced arrow wing configuration cruising at Mach 2.7. Preliminary studies were made to insure compliance of the configuration with general design criteria, integrate the propulsion system with the airframe, and define an efficient structural arrangement. Material and concept selection, detailed structural analysis, structural design and airplane mass analysis were completed based on current technology. Based on estimated future technology, structural sizing for strength and a preliminary assessment of the flutter of a strength designed composite structure were completed. An advanced computerized structural design system was used, in conjunction with a relatively complex finite element model, for detailed analysis and sizing of structural members.

How livestock and flooding mediate the ecological integrity of working forests in Amazon River floodplains.

PubMed

Lucas, Christine M; Sheikh, Pervaze; Gagnon, Paul R; Mcgrath, David G

2016-01-01

The contribution of working forests to tropical conservation and development depends upon the maintenance of ecological integrity under ongoing land use. Assessment of ecological integrity requires an understanding of the structure, composition, and function and major drivers that govern their variability. Working forests in tropical river floodplains provide many goods and services, yet the data on the ecological processes that sustain these services is scant. In flooded forests of riverside Amazonian communities, we established 46 0.1-ha plots varying in flood duration, use by cattle and water buffalo, and time since agricultural abandonment (30-90 yr). We monitored three aspects of ecological integrity (stand structure, species composition, and dynamics of trees and seedlings) to evaluate the impacts of different trajectories of livestock activity (alleviation, stasis, and intensification) over nine years. Negative effects of livestock intensification were solely evident in the forest understory, and plots alleviated from past heavy disturbance increased in seedling density but had higher abundance of thorny species than plots maintaining low activity. Stand structure, dynamics, and tree species composition were strongly influenced by the natural pulse of seasonal floods, such that the defining characteristics of integrity were dependent upon flood duration (3-200 d). Forests with prolonged floods ≥ 140 d had not only lower species richness but also lower rates of recruitment and species turnover relative to forests with short floods <70 d. Overall, the combined effects of livestock intensification and prolonged flooding hindered forest regeneration, but overall forest integrity was largely related to the hydrological regime and age. Given this disjunction between factors mediating canopy and understory integrity, we present a subset of metrics for regeneration and recruitment to distinguish forest condition by livestock trajectory. Although our study design includes confounded factors that preclude a definitive assessment of the major drivers of ecological change, we provide much-needed data on the regrowth of a critical but poorly studied ecosystem. In addition to its emphasis on the dynamics of tropical wetland forests undergoing anthropogenic and environmental change, our case study is an important example for how to assess of ecological integrity in working forests of tropical ecosystems.

Fatigue damage prognosis of internal delamination in composite plates under cyclic compression loadings using affine arithmetic as uncertainty propagation tool

NASA Astrophysics Data System (ADS)

Gbaguidi, Audrey J.-M.

Structural health monitoring (SHM) has become indispensable for reducing maintenance costs and increasing the in-service capacity of a structure. The increased use of lightweight composite materials in aircraft structures drastically increased the effects of fatigue induced damage on their critical structural components and thus the necessity to predict the remaining life of those components. Damage prognosis, one of the least investigated fields in SHM, uses the current damage state of the system to forecast its future performance by estimating the expected loading environments. A successful damage prediction model requires the integration of technologies in areas like measurements, materials science, mechanics of materials, and probability theories, but most importantly the quantification of uncertainty in all these areas. In this study, Affine Arithmetic is used as a method for incorporating the uncertainties due to the material properties into the fatigue life prognosis of composite plates subjected to cyclic compressive loadings. When loadings are compressive in nature, the composite plates undergo repeated buckling-unloading of the delaminated layer which induces mixed modes I and II states of stress at the tip of the delamination in the plates. The Kardomateas model-based prediction law is used to predict the growth of the delamination, while the integration of the effects of the uncertainties for modes I and II coefficients in the fatigue life prediction model is handled using Affine arithmetic. The Mode I and Mode II interlaminar fracture toughness and fatigue characterization of the composite plates are first experimentally studied to obtain the material coefficients and fracture toughness, respectively. Next, these obtained coefficients are used in the Kardomateas law to predict the delamination lengths in the composite plates while using Affine Arithmetic to handle their uncertainties. At last, the fatigue characterization of the composite plates during compressive-buckling loadings is experimentally studied, and the delamination lengths obtained are compared with the predicted values to check the performance of Affine Arithmetic as an uncertainty propagation tool.

Learning Objects Update: Review and Critical Approach to Content Aggregation

ERIC Educational Resources Information Center

Balatsoukas, Panos; Morris, Anne; O'Brien, Ann

2008-01-01

The structure and composite nature of a learning object is still open to interpretation. Although several theoretical studies advocate integrated approaches to the structure and aggregation level of learning objects, in practice, many content specifications, such as SCORM, IMS Content Packaging, and course authoring tools, do not explicitly state…

Reliability analysis of composite structures

NASA Technical Reports Server (NTRS)

Kan, Han-Pin

1992-01-01

A probabilistic static stress analysis methodology has been developed to estimate the reliability of a composite structure. Closed form stress analysis methods are the primary analytical tools used in this methodology. These structural mechanics methods are used to identify independent variables whose variations significantly affect the performance of the structure. Once these variables are identified, scatter in their values is evaluated and statistically characterized. The scatter in applied loads and the structural parameters are then fitted to appropriate probabilistic distribution functions. Numerical integration techniques are applied to compute the structural reliability. The predicted reliability accounts for scatter due to variability in material strength, applied load, fabrication and assembly processes. The influence of structural geometry and mode of failure are also considerations in the evaluation. Example problems are given to illustrate various levels of analytical complexity.

Sustained and localized in vitro release of BMP-2/7, RANKL, and tetracycline from FlexBone, an elastomeric osteoconductive bone substitute.

PubMed

Xu, Jianwen; Li, Xinning; Lian, Jane B; Ayers, David C; Song, Jie

2009-10-01

We tested the hypothesis that synthetic composites containing a high percentage of osteoconductive biominerals well-integrated with a hydrophilic polymer matrix can be engineered to provide both the structural and biochemical framework of a viable synthetic bone substitute. FlexBone, an elastic hydrogel-mineral composite exhibiting excellent structural integration was prepared by crosslinking poly(2-hydroxyethyl methacrylate) hydrogel in the presence of 25 wt% nanocrystalline hydroxyapatite and 25 wt% tricalcium phosphate. Biologically active factors tetracycline, BMP-2/7, and RANKL that stimulate bone formation and remodeling were encapsulated into FlexBone during polymerization or via postpolymerization adsorption. SEM and dynamic mechanical analyses showed that the encapsulation of tetracycline (5.0 wt%) did not compromise the structural integrity and compressive behavior of FlexBone, which could withstand repetitive megapascal-compressive loadings and be securely press-fitted into critical femoral defects. Dose-dependent, sustained in vitro release of tetracycline was characterized by spectroscopy and bacterial inhibition. A single dose of 40 ng BMP-2/7 or 10 ng RANKL pre-encapsulated with 50 mg FlexBone, released over 1 week, was able to induce local osteogenic differentiation of myoblast C2C12 cells and osteoclastogenesis of macrophage RAW264.7 cells, respectively. With a bonelike structural composition, useful surgical handling characteristics, and tunable biochemical microenvironment, FlexBone provides an exciting opportunity for the treatment of hard-to-heal skeletal defects with minimal systemic side effects. (c) 2009 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Differential Weighting for Subcomponent Measures of Integrated Clinical Encounter Scores Based on the USMLE Step 2 CS Examination: Effects on Composite Score Reliability and Pass-Fail Decisions.

PubMed

Park, Yoon Soo; Lineberry, Matthew; Hyderi, Abbas; Bordage, Georges; Xing, Kuan; Yudkowsky, Rachel

2016-11-01

Medical schools administer locally developed graduation competency examinations (GCEs) following the structure of the United States Medical Licensing Examination Step 2 Clinical Skills that combine standardized patient (SP)-based physical examination and the patient note (PN) to create integrated clinical encounter (ICE) scores. This study examines how different subcomponent scoring weights in a locally developed GCE affect composite score reliability and pass-fail decisions for ICE scores, contributing to internal structure and consequential validity evidence. Data from two M4 cohorts (2014: n = 177; 2015: n = 182) were used. The reliability of SP encounter (history taking and physical examination), PN, and communication and interpersonal skills scores were estimated with generalizability studies. Composite score reliability was estimated for varying weight combinations. Faculty were surveyed for preferred weights on the SP encounter and PN scores. Composite scores based on Kane's method were compared with weighted mean scores. Faculty suggested weighting PNs higher (60%-70%) than the SP encounter scores (30%-40%). Statistically, composite score reliability was maximized when PN scores were weighted at 40% to 50%. Composite score reliability of ICE scores increased by up to 0.20 points when SP-history taking (SP-Hx) scores were included; excluding SP-Hx only increased composite score reliability by 0.09 points. Classification accuracy for pass-fail decisions between composite and weighted mean scores was 0.77; misclassification was < 5%. Medical schools and certification agencies should consider implications of assigning weights with respect to composite score reliability and consequences on pass-fail decisions.

ISAAC Advanced Composites Research Testbed

NASA Technical Reports Server (NTRS)

Wu, K. Chauncey; Stewart, Brian K.; Martin, Robert A.

2014-01-01

The NASA Langley Research Center is acquiring a state-of-art composites fabrication capability to support the Center's advanced research and technology mission. The system introduced in this paper is named ISAAC (Integrated Structural Assembly of Advanced Composites). The initial operational capability of ISAAC is automated fiber placement, built around a commercial system from Electroimpact, Inc. that consists of a multi-degree of freedom robot platform, a tool changer mechanism, and a purpose-built fiber placement end effector. Examples are presented of the advanced materials, structures, structural concepts, fabrication processes and technology development that may be enabled using the ISAAC system. The fiber placement end effector may be used directly or with appropriate modifications for these studies, or other end effectors with different capabilities may either be bought or developed with NASA's partners in industry and academia.

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Lu, Yang; Liu, Xianming; Wang, Weixiao; Cheng, Jinbing; Yan, Hailong; Tang, Chengchun; Kim, Jang-Kyo; Luo, Yongsong

2015-11-01

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15-30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m2 g-1 and a high conductivity of 0.471 S cm-1. As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g-1 at a current density of 10 mA cm-2 over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons.

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors.

PubMed

Lu, Yang; Liu, Xianming; Wang, Weixiao; Cheng, Jinbing; Yan, Hailong; Tang, Chengchun; Kim, Jang-Kyo; Luo, Yongsong

2015-11-16

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15-30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m(2) g(-1) and a high conductivity of 0.471 S cm(-1). As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g(-1) at a current density of 10 mA cm(-2) over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons.

Stochastic global identification of a bio-inspired self-sensing composite UAV wing via wind tunnel experiments

NASA Astrophysics Data System (ADS)

Kopsaftopoulos, Fotios; Nardari, Raphael; Li, Yu-Hung; Wang, Pengchuan; Chang, Fu-Kuo

2016-04-01

In this work, the system design, integration, and wind tunnel experimental evaluation are presented for a bioinspired self-sensing intelligent composite unmanned aerial vehicle (UAV) wing. A total of 148 micro-sensors, including piezoelectric, strain, and temperature sensors, in the form of stretchable sensor networks are embedded in the layup of a composite wing in order to enable its self-sensing capabilities. Novel stochastic system identification techniques based on time series models and statistical parameter estimation are employed in order to accurately interpret the sensing data and extract real-time information on the coupled air flow-structural dynamics. Special emphasis is given to the wind tunnel experimental assessment under various flight conditions defined by multiple airspeeds and angles of attack. A novel modeling approach based on the recently introduced Vector-dependent Functionally Pooled (VFP) model structure is employed for the stochastic identification of the "global" coupled airflow-structural dynamics of the wing and their correlation with dynamic utter and stall. The obtained results demonstrate the successful system-level integration and effectiveness of the stochastic identification approach, thus opening new perspectives for the state sensing and awareness capabilities of the next generation of "fly-by-fee" UAVs.

Applications of a damage tolerance analysis methodology in aircraft design and production

NASA Technical Reports Server (NTRS)

Woodward, M. R.; Owens, S. D.; Law, G. E.; Mignery, L. A.

1992-01-01

Objectives of customer mandated aircraft structural integrity initiatives in design are to guide material selection, to incorporate fracture resistant concepts in the design, to utilize damage tolerance based allowables and planned inspection procedures necessary to enhance the safety and reliability of manned flight vehicles. However, validated fracture analysis tools for composite structures are needed to accomplish these objectives in a timely and economical manner. This paper briefly describes the development, validation, and application of a damage tolerance methodology for composite airframe structures. A closed-form analysis code, entitled SUBLAM was developed to predict the critical biaxial strain state necessary to cause sublaminate buckling-induced delamination extension in an impact damaged composite laminate. An embedded elliptical delamination separating a thin sublaminate from a thick parent laminate is modelled. Predicted failure strains were correlated against a variety of experimental data that included results from compression after impact coupon and element tests. An integrated analysis package was developed to predict damage tolerance based margin-of-safety (MS) using NASTRAN generated loads and element information. Damage tolerance aspects of new concepts are quickly and cost-effectively determined without the need for excessive testing.

Embedded electronics for intelligent structures

NASA Astrophysics Data System (ADS)

Warkentin, David J.; Crawley, Edward F.

The signal, power, and communications provisions for the distributed control processing, sensing, and actuation of an intelligent structure could benefit from a method of physically embedding some electronic components. The preliminary feasibility of embedding electronic components in load-bearing intelligent composite structures is addressed. A technique for embedding integrated circuits on silicon chips within graphite/epoxy composite structures is presented which addresses the problems of electrical, mechanical, and chemical isolation. The mechanical and chemical isolation of test articles manufactured by this technique are tested by subjecting them to static and cyclic mechanical loads and a temperature/humidity/bias environment. The likely failure modes under these conditions are identified, and suggestions for further improvements in the technique are discussed.

A finite element-boundary integral method for scattering and radiation by two- and three-dimensional structures

NASA Technical Reports Server (NTRS)

Jin, Jian-Ming; Volakis, John L.; Collins, Jeffery D.

1991-01-01

A review of a hybrid finite element-boundary integral formulation for scattering and radiation by two- and three-composite structures is presented. In contrast to other hybrid techniques involving the finite element method, the proposed one is in principle exac, and can be implemented using a low O(N) storage. This is of particular importance for large scale applications and is a characteristic of the boundary chosen to terminate the finite-element mesh, usually as close to the structure as possible. A certain class of these boundaries lead to convolutional boundary integrals which can be evaluated via the fast Fourier transform (FFT) without a need to generate a matrix; thus, retaining the O(N) storage requirement.

Production Principles and Technological Development of Novel Woven Spacer Preforms and Integrated Stiffener Structures

NASA Astrophysics Data System (ADS)

Torun, Ahmet R.; Mountasir, Adil; Hoffmann, Gerald; Cherif, Chokri

2013-06-01

3D textile preforms offer a high potential to increase mechanical properties of composites and/or decrease manufacturing costs. Within the scope of this study, production principles were developed for complex spacer preforms and integrated stiffeners. These principles were applied through technological further development of the well-known face-to-face and terry weaving techniques. Various woven preforms were produced with Glass fibre/Polypropylene (GF/PP) Commingled yarns, however, the technology is suitable for any type of reinforcement yarns. U-shaped woven spacer preform was consolidated into a sandwich composite component for lightweight applications.

Probability techniques for reliability analysis of composite materials

NASA Technical Reports Server (NTRS)

Wetherhold, Robert C.; Ucci, Anthony M.

1994-01-01

Traditional design approaches for composite materials have employed deterministic criteria for failure analysis. New approaches are required to predict the reliability of composite structures since strengths and stresses may be random variables. This report will examine and compare methods used to evaluate the reliability of composite laminae. The two types of methods that will be evaluated are fast probability integration (FPI) methods and Monte Carlo methods. In these methods, reliability is formulated as the probability that an explicit function of random variables is less than a given constant. Using failure criteria developed for composite materials, a function of design variables can be generated which defines a 'failure surface' in probability space. A number of methods are available to evaluate the integration over the probability space bounded by this surface; this integration delivers the required reliability. The methods which will be evaluated are: the first order, second moment FPI methods; second order, second moment FPI methods; the simple Monte Carlo; and an advanced Monte Carlo technique which utilizes importance sampling. The methods are compared for accuracy, efficiency, and for the conservativism of the reliability estimation. The methodology involved in determining the sensitivity of the reliability estimate to the design variables (strength distributions) and importance factors is also presented.

Autonomous sensing of composites with carbon nanotubes for structural health monitoring

NASA Astrophysics Data System (ADS)

Liu, Yingtao; Yekani Fard, Masoud; Rajadas, Abhishek; Chattopadhyay, Aditi

2012-04-01

The development of structural health monitoring techniques leads to the integration of sensing capability within engineering structures. This study investigates the application of multi walled carbon nanotubes in polymer matrix composites for autonomous damage detection through changes in electrical resistance. The autonomous sensing capabilities of fiber reinforced nanocomposites are studied under multiple loading conditions including tension loads. Single-lap joints with different joint lengths are tested. Acoustic emission sensing is used to validate the matrix crack propagation. A digital image correlation system is used to measure the shear strain field of the joint area. The joints with 1.5 inch length have better autonomous sensing capabilities than those with 0.5 inch length. The autonomous sensing capabilities of nanocomposites are found to be sensitive to crack propagation and can revolutionize the research on composite structural health management in the near future.

12,000 Students and Their English Teachers: Tested Units in Teaching Literature, Language, Composition.

ERIC Educational Resources Information Center

College Entrance Examination Board, New York, NY. Commission on English.

Literature, language, and composition are integrated in this collection of 30 model teaching units for grades 9-12. The units are concerned with (1) the explication and comparison of novels by Hemingway, Wilder, Kipling, and Knowles, (2) short story techniques used by writers from Poe to Joyce, (3) poetic structure and themes as demonstrated in…

Damage Tolerance of Pre-Stressed Composite Panels Under Impact Loads

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; Toso-Pentecôte, Nathalie; Schueler, Dominik

2014-02-01

An experimental test campaign studied the structural integrity of carbon fibre/epoxy panels preloaded in tension or compression then subjected to gas gun impact tests causing significant damage. The test programme used representative composite aircraft fuselage panels composed of aerospace carbon fibre toughened epoxy prepreg laminates. Preload levels in tension were representative of design limit loads for fuselage panels of this size, and maximum compression preloads were in the post-buckle region. Two main impact scenarios were considered: notch damage from a 12 mm steel cube projectile, at velocities in the range 93-136 m/s; blunt impact damage from 25 mm diameter glass balls, at velocities 64-86 m/s. The combined influence of preload and impact damage on panel residual strengths was measured and results analysed in the context of damage tolerance requirements for composite aircraft panels. The tests showed structural integrity well above design limit loads for composite panels preloaded in tension and compression with visible notch impact damage from hard body impact tests. However, blunt impact tests on buckled compression loaded panels caused large delamination damage regions which lowered plate bending stiffness and reduced significantly compression strengths in buckling.

High-Throughput Screening of Vascular Endothelium-Destructive or Protective Microenvironments: Cooperative Actions of Extracellular Matrix Composition, Stiffness, and Structure.

PubMed

Ding, Yonghui; Floren, Michael; Tan, Wei

2017-06-01

Pathological modification of the subendothelial extracellular matrix (ECM) has closely been associated with endothelial activation and subsequent cardiovascular disease progression. To understand regulatory mechanisms of these matrix modifications, the majority of previous efforts have focused on the modulation of either chemical composition or matrix stiffness on 2D smooth surfaces without simultaneously probing their cooperative effects on endothelium function on in vivo like 3D fibrous matrices. To this end, a high-throughput, combinatorial microarray platform on 2D and 3D hydrogel settings to resemble the compositions, stiffness, and structure of healthy and diseased subendothelial ECM has been established, and further their respective and combined effects on endothelial attachment, proliferation, inflammation, and junctional integrity have been investigated. For the first time, the results demonstrate that 3D fibrous structure resembling native ECM is a critical endothelium-protective microenvironmental factor by maintaining the stable, quiescent endothelium with strong resistance to proinflammatory stimuli. It is also revealed that matrix stiffening, in concert with chemical compositions resembling diseased ECM, particularly collagen III, could aggravate activation of nuclear factor kappa B, disruption of endothelium integrity, and susceptibility to proinflammatory stimuli. This study elucidates cooperative effects of various microenvironmental factors on endothelial activation and sheds light on new in vitro model for cardiovascular diseases. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Materials for the General Aviation Industry: Effect of Environment on Mechanical Properties of Glass Fabric/Rubber Toughened Vinyl Ester Laminates

NASA Technical Reports Server (NTRS)

McBride, Timothy M.

1995-01-01

A screening evaluation is being conducted to determine the performance of several glass fabric/vinyl ester composite material systems for use in primary General Aviation aircraft structures. In efforts to revitalize the General Aviation industry, the Integrated Design and Manufacturing Work Package for General Aviation Airframe and Propeller Structures is seeking to develop novel composite materials and low-cost manufacturing methods for lighter, safer and more affordable small aircraft. In support of this Work Package, this study is generating material properties for several glass fabric/rubber toughened vinyl ester composite systems and investigates the effect of environment on property retention. All laminates are made using the Seemann Composites Resin Infusion Molding Process (SCRIMP), a potential manufacturing method for the General Aviation industry.

Dynamic mechanical analysis and organization/storage of data for polymetric materials

NASA Technical Reports Server (NTRS)

Rosenberg, M.; Buckley, W.

1982-01-01

Dynamic mechanical analysis was performed on a variety of temperature resistant polymers and composite resin matrices. Data on glass transition temperatures and degree of cure attained were derived. In addition a laboratory based computer system was installed and data base set up to allow entry of composite data. The laboratory CPU termed TYCHO is based on a DEC PDP 11/44 CPU with a Datatrieve relational data base. The function of TYCHO is integration of chemical laboratory analytical instrumentation and storage of chemical structures for modeling of new polymeric structures and compounds

Evaluation of Dynamic Characteristics of the Footbridge with Integral Abutments

NASA Astrophysics Data System (ADS)

Pańtak, Marek; Jarek, Bogusław

2017-09-01

The paper presents the results of dynamic field tests and numerical analysis of the footbridge designed as a three-span composite structure with integral abutments. The adopted design solution which has allowed to achieve a high resistance of the structure to dynamic loads and to meet the requirements of the criteria of comfort of use with a large reserve has been characterized. For comparative purposes, numerical analyzes of three construction variants of the footbridge were presented: F-1 - construction with integral abutments (realized variant), F-2 - construction with girders anchored in the abutments by means of tension rocker bearings, F-3 - construction with concrete side spans.

Fully integrated carbon nanotube composite thin film strain sensors on flexible substrates for structural health monitoring

NASA Astrophysics Data System (ADS)

Burton, A. R.; Lynch, J. P.; Kurata, M.; Law, K. H.

2017-09-01

Multifunctional thin film materials have opened many opportunities for novel sensing strategies for structural health monitoring. While past work has established methods of optimizing multifunctional materials to exhibit sensing properties, comparatively less work has focused on their integration into fully functional sensing systems capable of being deployed in the field. This study focuses on the advancement of a scalable fabrication process for the integration of multifunctional thin films into a fully integrated sensing system. This is achieved through the development of an optimized fabrication process that can create a broad range of sensing systems using multifunctional materials. A layer-by-layer deposited multifunctional composite consisting of single walled carbon nanotubes (SWNT) in a polyvinyl alcohol and polysodium-4-styrene sulfonate matrix are incorporated with a lithography process to produce a fully integrated sensing system deposited on a flexible substrate. To illustrate the process, a strain sensing platform consisting of a patterned SWNT-composite thin film as a strain-sensitive element within an amplified Wheatstone bridge sensing circuit is presented. Strain sensing is selected because it presents many of the design and processing challenges that are core to patterning multifunctional thin film materials into sensing systems. Strain sensors fabricated on a flexible polyimide substrate are experimentally tested under cyclic loading using standard four-point bending coupons and a partial-scale steel frame assembly under lateral loading. The study reveals the material process is highly repeatable to produce fully integrated strain sensors with linearity and sensitivity exceeding 0.99 and 5 {{V}}/{ε }, respectively. The thin film strain sensors are robust and are capable of high strain measurements beyond 3000 μ {ε }.

Aerothermo-Structural Analysis of Low Cost Composite Nozzle/Inlet Components

NASA Technical Reports Server (NTRS)

Shivakumar, Kuwigai; Challa, Preeli; Sree, Dave; Reddy, D.

1999-01-01

This research is a cooperative effort among the Turbomachinery and Propulsion Division of NASA Glenn, CCMR of NC A&T State University, and the Tuskegee University. The NC A&T is the lead center and Tuskegee University is the participating institution. Objectives of the research were to develop an integrated aerodynamic, thermal and structural analysis code for design of aircraft engine components, such as, nozzles and inlets made of textile composites; conduct design studies on typical inlets for hypersonic transportation vehicles and setup standards test examples and finally manufacture a scaled down composite inlet. These objectives are accomplished through the following seven tasks: (1) identify the relevant public domain codes for all three types of analysis; (2) evaluate the codes for the accuracy of results and computational efficiency; (3) develop aero-thermal and thermal structural mapping algorithms; (4) integrate all the codes into one single code; (5) write a graphical user interface to improve the user friendliness of the code; (6) conduct test studies for rocket based combined-cycle engine inlet; and finally (7) fabricate a demonstration inlet model using textile preform composites. Tasks one, two and six are being pursued. Selected and evaluated NPARC for flow field analysis, CSTEM for in-depth thermal analysis of inlets and nozzles and FRAC3D for stress analysis. These codes have been independently verified for accuracy and performance. In addition, graphical user interface based on micromechanics analysis for laminated as well as textile composites was developed. Demonstration of this code will be made at the conference. A rocket based combined cycle engine was selected for test studies. Flow field analysis of various inlet geometries were studied. Integration of codes is being continued. The codes developed are being applied to a candidate example of trailblazer engine proposed for space transportation. A successful development of the code will provide a simpler, faster and user-friendly tool for conducting design studies of aircraft and spacecraft engines, applicable in high speed civil transport and space missions.

Integration of Composite Structures in Modern Day Architecture: Case Study of City Business Centre, Timisoara, Romania

NASA Astrophysics Data System (ADS)

Vataman, Adina; Gaivoronschi, Vlad; Mosoarca, Marius

2017-10-01

In current day structural design the use of composite steel-concrete structures has become the norm; because of the advantages that each of these materials has to offer. Composite structures also have the benefit of a faster execution at a lower cost, compared to traditional structures. While the arguments in favour of designing composite structures are well-known and appreciated by civil engineers; there remains a question of integrating these structures in modern-day urban landscapes. Eastern European countries are welcoming a blossoming of culture, arts, economy and industry, which unavoidably and necessarily will lead to a change in urban landscapes. With an increasing amount of foreign companies opening offices in these areas, the need for modern office solutions has arisen. The current paper presents a case study of an office building complex situated in the western part of Romania, in the city of Timişoara. The complex consists of 5 office buildings; all designed in composite steel-concrete structure, an underground parking lot, multiple terraces and adjacent promenade areas. Within the context of rapid growth and development of the city, the City Business Centre has offered high quality office spaces in the heart of the city, while considering the needs of the community. A very important aspect in the successful completion of the project was the efficient and professional collaboration between the separate project teams, between the owner, represented by the project management team, the architect, the structural designer and the building company. The successful joining of seismic structural solutions with modern architectural aesthetics has led to a dynamic, vibrant environment, making the City Business Centre the core of the region’s business life, at the same time redefining Timisoara’s architectural landscape. A testimony to the success of the project was the Civil Engineering Structural Designers Associations’ (AICPS) 3rd Prize awarded for great performance and quality in structural design. The project was also awarded a „Green Building of the Year” award by the Romanian Green Building Council and also the „Office Development of the Year” in South-Eastern Europe awarded at the Real Estate Awards by an international jury of renowned real estate developers, consulting firms and investment banks. The project was also selected by the European Architects’ Council to represent Romania in a Sustainable Architecture Exhibition at the European Parliament in Brussels.

Efficient Design and Analysis of Lightweight Reinforced Core Sandwich and PRSEUS Structures

NASA Technical Reports Server (NTRS)

Bednarcyk, Brett A.; Yarrington, Phillip W.; Lucking, Ryan C.; Collier, Craig S.; Ainsworth, James J.; Toubia, Elias A.

2012-01-01

Design, analysis, and sizing methods for two novel structural panel concepts have been developed and incorporated into the HyperSizer Structural Sizing Software. Reinforced Core Sandwich (RCS) panels consist of a foam core with reinforcing composite webs connecting composite facesheets. Boeing s Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) panels use a pultruded unidirectional composite rod to provide axial stiffness along with integrated transverse frames and stitching. Both of these structural concepts are ovencured and have shown great promise applications in lightweight structures, but have suffered from the lack of efficient sizing capabilities similar to those that exist for honeycomb sandwich, foam sandwich, hat stiffened, and other, more traditional concepts. Now, with accurate design methods for RCS and PRSEUS panels available in HyperSizer, these concepts can be traded and used in designs as is done with the more traditional structural concepts. The methods developed to enable sizing of RCS and PRSEUS are outlined, as are results showing the validity and utility of the methods. Applications include several large NASA heavy lift launch vehicle structures.

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.

Structural integrated sensor and actuator systems for active flow control

NASA Astrophysics Data System (ADS)

Behr, Christian; Schwerter, Martin; Leester-Schädel, Monika; Wierach, Peter; Dietzel, Andreas; Sinapius, Michael

2016-04-01

An adaptive flow separation control system is designed and implemented as an essential part of a novel high-lift device for future aircraft. The system consists of MEMS pressure sensors to determine the flow conditions and adaptive lips to regulate the mass flow and the velocity of a wall near stream over the internally blown Coanda flap. By the oscillating lip the mass flow in the blowing slot changes dynamically, consequently the momentum exchange of the boundary layer over a high lift flap required mass flow can be reduced. These new compact and highly integrated systems provide a real-time monitoring and manipulation of the flow conditions. In this context the integration of pressure sensors into flow sensing airfoils of composite material is investigated. Mechanical and electrical properties of the integrated sensors are investigated under mechanical loads during tensile tests. The sensors contain a reference pressure chamber isolated to the ambient by a deformable membrane with integrated piezoresistors connected as a Wheatstone bridge, which outputs voltage signals depending on the ambient pressure. The composite material in which the sensors are embedded consists of 22 individual layers of unidirectional glass fiber reinforced plastic (GFRP) prepreg. The results of the experiments are used for adapting the design of the sensors and the layout of the laminate to ensure an optimized flux of force in highly loaded structures primarily for future aeronautical applications. It can be shown that the pressure sensor withstands the embedding process into fiber composites with full functional capability and predictable behavior under stress.

A scaleable integrated sensing and control system for NDE, monitoring, and control of medium to very large composite smart structures

NASA Astrophysics Data System (ADS)

Jones, Jerry; Rhoades, Valerie; Arner, Radford; Clem, Timothy; Cuneo, Adam

2007-04-01

NDE measurements, monitoring, and control of smart and adaptive composite structures requires that the central knowledge system have an awareness of the entire structure. Achieving this goal necessitates the implementation of an integrated network of significant numbers of sensors. Additionally, in order to temporally coordinate the data from specially distributed sensors, the data must be time relevant. Early adoption precludes development of sensor technology specifically for this application, instead it will depend on the ability to utilize legacy systems. Partially supported by the U.S. Department of Commerce, National Institute of Standards and Technology, Advanced Technology Development Program (NIST-ATP), a scalable integrated system has been developed to implement monitoring of structural integrity and the control of adaptive/intelligent structures. The project, called SHIELD (Structural Health Identification and Electronic Life Determination), was jointly undertaken by: Caterpillar, N.A. Tech., Motorola, and Microstrain. SHIELD is capable of operation with composite structures, metallic structures, or hybrid structures. SHIELD consists of a real-time processing core on a Motorola MPC5200 using a C language based real-time operating system (RTOS). The RTOS kernel was customized to include a virtual backplane which makes the system completely scalable. This architecture provides for multiple processes to be operating simultaneously. They may be embedded as multiple threads on the core hardware or as separate independent processors connected to the core using a software driver called a NAT-Network Integrator (NATNI). NATNI's can be created for any communications application. In it's current embodiment, NATNI's have been created for CAN bus, TCP/IP (Ethernet) - both wired and 802.11 b and g, and serial communications using RS485 and RS232. Since SHIELD uses standard C language, it is easy to port any monitoring or control algorithm, thus providing for legacy technology which may use other hardware processors and various communications means. For example, two demonstrations of SHIELD have been completed, in January and May 2005 respectively. One demonstration used algorithms in C running in multiple threads in the SHIELD core and utilizing two different sensor networks, one CAN bus and one wireless. The second had algorithms operating in C on the SHIELD core and other algorithms running on multiple Texas Instruments DSP processors using a NATNI that communicated via wired TCP/IP. A key feature of SHIELD is the implementation of a wireless ZIGBEE (802.15.4) network for implementing large numbers of small, low cost, low power sensors communication via a meshstar wireless network. While SHIELD was designed to integrate with a wide variety of existing communications protocols, a ZIGBEE network capability was implemented specifically for SHIELD. This will facilitate the monitoring of medium to very large structures including marine applications, utility scale multi-megawatt wind energy systems, and aircraft/spacecraft. The SHIELD wireless network will facilitate large numbers of sensors (up to 32000), accommodate sensors embedded into the composite material, can communicate to both sensors and actuators, and prevents obsolescence by providing for re-programming of the nodes via remote RF communications. The wireless network provides for ultra-low energy use, spatial location, and accurate timestamping, utilizing the beaconing feature of ZIGBEE.

High char yield epoxy curing agents

NASA Technical Reports Server (NTRS)

Delvigs, P.; Serafini, T. T.; Vanucci, R. D.

1981-01-01

Class of imide-amine curing agents preserves structural integrity, prevents fiber release, and is fully compatible with conventional epoxy resins; agents do not detract from composite properties while greatly reducing char yield. Materials utilizing curing are used in aerospace, automotive, and other structural components where deterioration must be minimized and fiber release avoided in event of fire.

Toward Gleasonian landscape ecology: From communities to species, from patches to pixels

Treesearch

Samuel A. Cushman; Jeffrey S. Evans; Kevin McGarigal; Joseph M. Kiesecker

2010-01-01

The fusion of individualistic community ecology with the Hutchinsonian niche concept enabled a broad integration of ecological theory, spanning all the way from the niche characteristics of individual species, to the composition, structure, and dynamics of ecological communities. Landscape ecology has been variously described as the study of the structure, function,...

Nonlinear mesomechanics of composites with periodic microstructure

NASA Technical Reports Server (NTRS)

Walker, Kevin P.; Jordan, Eric H.; Freed, Alan D.

1989-01-01

This work is concerned with modeling the mechanical deformation or constitutive behavior of composites comprised of a periodic microstructure under small displacement conditions at elevated temperature. A mesomechanics approach is adopted which relates the microimechanical behavior of the heterogeneous composite with its in-service macroscopic behavior. Two different methods, one based on a Fourier series approach and the other on a Green's function approach, are used in modeling the micromechanical behavior of the composite material. Although the constitutive formulations are based on a micromechanical approach, it should be stressed that the resulting equations are volume averaged to produce overall effective constitutive relations which relate the bulk, volume averaged, stress increment to the bulk, volume averaged, strain increment. As such, they are macromodels which can be used directly in nonlinear finite element programs such as MARC, ANSYS and ABAQUS or in boundary element programs such as BEST3D. In developing the volume averaged or efective macromodels from the micromechanical models, both approaches will require the evaluation of volume integrals containing the spatially varying strain distributions throughout the composite material. By assuming that the strain distributions are spatially constant within each constituent phase-or within a given subvolume within each constituent phase-of the composite material, the volume integrals can be obtained in closed form. This simplified micromodel can then be volume averaged to obtain an effective macromodel suitable for use in the MARC, ANSYS and ABAQUS nonlinear finite element programs via user constitutive subroutines such as HYPELA and CMUSER. This effective macromodel can be used in a nonlinear finite element structural analysis to obtain the strain-temperature history at those points in the structure where thermomechanical cracking and damage are expected to occur, the so called damage critical points of the structure.

Application of fiber-reinforced bismaleimide materials to aircraft nacelle structures

NASA Technical Reports Server (NTRS)

Peros, Vasilios; Ruth, John; Trawinski, David

1992-01-01

Existing aircraft engine nacelle structures employ advanced composite materials to reduce weight and thereby increase overall performance. Use of advanced composite materials on existing aircraft nacelle structures includes fiber-reinforced epoxy structures and has typically been limited to regions furthest away from the hot engine core. Portions of the nacelle structure that are closer to the engine require materials with a higher temperature capability. In these portions, existing nacelle structures employ aluminum sandwich construction and skin/stringer construction. The aluminum structure is composed of many detail parts and assemblies and is usually protected by some form of ablative, insulator, or metallic thermal shield. A one-piece composite inner cowl for a new-generation engine nacelle structure has been designed using fiber-reinforced bismaleimide (BMI) materials and honeycomb core in a sandwich construction. The new composite design has many advantages over the existing aluminum structure. Multiple details were integrated into the one-piece composite design, thereby significantly reducing the number of detail parts and fasteners. The use of lightweight materials and the reduction of the number of joints result in a significant weight reduction over the aluminum design; manufacturing labor and the overall number of tools required have also been reduced. Several significant technical issues were addressed in the development of a BMI composite design. Technical evaluation of the available BMI systems led to the selection of a toughened BMI material which was resistant to microcracking under thermal cyclic loading and enhanced the damage tolerance of the structure. Technical evaluation of the degradation of BMI materials in contact with aluminum and other metals validated methods for isolation of the various materials. Graphite-reinforced BMI in contact with aluminum and some steels was found to degrade in salt spray testing. Isolation techniques such as those used for graphite-reinforced epoxy structures were shown to provide adequate protection. The springback and producibility of large BMI structures were evaluated by manufacturing prototype hardware which had the full-scale cross section of the one-piece composite structure.

Passive Earth Entry Vehicle Landing Test

NASA Technical Reports Server (NTRS)

Kellas, Sotiris

2017-01-01

Two full-scale passive Earth Entry Vehicles (EEV) with realistic structure, surrogate sample container, and surrogate Thermal Protection System (TPS) were built at NASA Langley Research Center (LaRC) and tested at the Utah Test and Training Range (UTTR). The main test objective was to demonstrate structural integrity and investigate possible impact response deviations of the realistic vehicle as compared to rigid penetrometer responses. With the exception of the surrogate TPS and minor structural differences in the back shell construction, the two test vehicles were identical in geometry and both utilized the Integrated Composite Stiffener Structure (ICoSS) structural concept in the forward shell. The ICoSS concept is a lightweight and highly adaptable composite concept developed at NASA LaRC specifically for entry vehicle TPS carrier structures. The instrumented test vehicles were released from a helicopter approximately 400 m above ground. The drop height was selected such that at least 98% of the vehicles terminal velocity would be achieved. While drop tests of spherical penetrometers and a low fidelity aerodynamic EEV model were conducted at UTTR in 1998 and 2000, this was the first time a passive EEV with flight-like structure, surrogate TPS, and sample container was tested at UTTR for the purpose of complete structural system validation. Test results showed that at a landing vertical speed of approximately 30 m/s, the test vehicle maintained structural integrity and enough rigidity to penetrate the sandy clay surface thus attenuating the landing load, as measured at the vehicle CG, to less than 600 g. This measured deceleration was found to be in family with rigid penetrometer test data from the 1998 and 2000 test campaigns. Design implications of vehicle structure/soil interaction with respect to sample container and sample survivability are briefly discussed.

Overview of the ACT program

NASA Technical Reports Server (NTRS)

Davis, John G., Jr.

1992-01-01

NASA's Advanced Composites Program (ACT) was initiated in 1988. A National Research Announcement was issued to solicit innovative ideas that could significantly contribute to development and demonstration of an integrated technology data base and confidence level that permits cost-effective use of composite primary structures in transport aircraft. Fifteen contracts were awarded by the Spring of 1989 and the participants include commercial and military airframe manufacturers, materials developers and suppliers, universities, and government laboratories. The program approach is to develop materials, structural mechanics methodology, design concepts, and fabrication procedures that offer the potential to make composite structures cost-effective compared to aluminum structure. Goals for the ACT program included 30-50 percent weight reduction, 20-25 percent acquisition cost reduction, and provided the scientific basis for predicting materials and structures performance. This paper provides an overview of the ACT program status, plans, and selected technical accomplishments. Sixteen additional papers, which provide more detailed information on the research and development accomplishments, are contained in this publication.

Study Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1997-01-01

The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires, light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures.

Structure and composition of the plate-boundary slip zone for the 2011 Tohoku-Oki earthquake.

PubMed

Chester, Frederick M; Rowe, Christie; Ujiie, Kohtaro; Kirkpatrick, James; Regalla, Christine; Remitti, Francesca; Moore, J Casey; Toy, Virginia; Wolfson-Schwehr, Monica; Bose, Santanu; Kameda, Jun; Mori, James J; Brodsky, Emily E; Eguchi, Nobuhisa; Toczko, Sean

2013-12-06

The mechanics of great subduction earthquakes are influenced by the frictional properties, structure, and composition of the plate-boundary fault. We present observations of the structure and composition of the shallow source fault of the 2011 Tohoku-Oki earthquake and tsunami from boreholes drilled by the Integrated Ocean Drilling Program Expedition 343 and 343T. Logging-while-drilling and core-sample observations show a single major plate-boundary fault accommodated the large slip of the Tohoku-Oki earthquake rupture, as well as nearly all the cumulative interplate motion at the drill site. The localization of deformation onto a limited thickness (less than 5 meters) of pelagic clay is the defining characteristic of the shallow earthquake fault, suggesting that the pelagic clay may be a regionally important control on tsunamigenic earthquakes.

Improving the reliability of road materials based on micronized sulfur composites

NASA Astrophysics Data System (ADS)

Abdrakhmanova, K. K.

2015-01-01

The work contains the results of a nano-structural modification of sulfur that prevents polymorphic transformations from influencing the properties of sulfur composites where sulfur is present in a thermodynamic stable condition that precludes destruction when operated. It has been established that the properties of sulfur-based composite materials can be significantly improved by modifying sulfur and structuring sulfur binder by nano-dispersed fiber particles and ultra-dispersed state filler. The paper shows the possibility of modifying Tengiz sulfur by its fragmenting which ensures that the structured sulfur is structurally changed and stabilized through reinforcement by ultra-dispersed fiber particles allowing the phase contact area to be multiplied. Interaction between nano-dispersed fibers of chrysotile asbestos and sulfur ensures the implementation of the mechanical properties of chrysotile asbestos tubes in reinforced composite and its integrity provided that the surface of chrysotile asbestos tubes are highly moistened with molten sulfur and there is high adhesion between the tubes and the matrix that, in addition to sulfur, contains limestone microparticles. Ability to apply materials in severe operation conditions and possibility of exposure in both aggressive medium and mechanical loads makes produced sulfur composites required by the road construction industry.

An Integrated Procedure for the Structural Design of a Composite Rotor-Hydrofoil of a Water Current Turbine (WCT)

NASA Astrophysics Data System (ADS)

Oller Aramayo, S. A.; Nallim, L. G.; Oller, S.

2013-12-01

This paper shows an integrated structural design optimization of a composite rotor-hydrofoil of a water current turbine by means the finite elements method (FEM), using a Serial/Parallel mixing theory (Rastellini et al. Comput. Struct. 86:879-896, 2008, Martinez et al., 2007, Martinez and Oller Arch. Comput. Methods. 16(4):357-397, 2009, Martinez et al. Compos. Part B Eng. 42(2011):134-144, 2010) coupled with a fluid-dynamic formulation and multi-objective optimization algorithm (Gen and Cheng 1997, Lee et al. Compos. Struct. 99:181-192, 2013, Lee et al. Compos. Struct. 94(3):1087-1096, 2012). The composite hydrofoil of the turbine rotor has been design using a reinforced laminate composites, taking into account the optimization of the carbon fiber orientation to obtain the maximum strength and lower rotational-inertia. Also, these results have been compared with a steel hydrofoil remarking the different performance on both structures. The mechanical and geometrical parameters involved in the design of this fiber-reinforced composite material are the fiber orientation, number of layers, stacking sequence and laminate thickness. Water pressure in the rotor of the turbine is obtained from a coupled fluid-dynamic simulation (CFD), whose detail can be found in the reference Oller et al. (2012). The main purpose of this paper is to achieve a very low inertia rotor minimizing the start-stop effect, because it is applied in axial water flow turbine currently in design by the authors, in which is important to take the maximum advantage of the kinetic energy. The FEM simulation codes are engineered by CIMNE (International Center for Numerical Method in Engineering, Barcelona, Spain), COMPack for the solids problem application, KRATOS for fluid dynamic application and RMOP for the structural optimization. To validate the procedure here presented, many turbine rotors made of composite materials are analyzed and three of them are compared with the steel one.

Spacelab software development and integration concepts study report. Volume 2: Appendices

NASA Technical Reports Server (NTRS)

1973-01-01

Software considerations were developed for incorporation in the spacelab systems design, and include management concepts for top-down structured programming, composite designs for modular programs, and team management methods for production programming.

Improved Joining of Metal Components to Composite Structures

NASA Technical Reports Server (NTRS)

Semmes, Edmund

2009-01-01

Systems requirements for complex spacecraft drive design requirements that lead to structures, components, and/or enclosures of a multi-material and multifunctional design. The varying physical properties of aluminum, tungsten, Invar, or other high-grade aerospace metals when utilized in conjunction with lightweight composites multiply system level solutions. These multi-material designs are largely dependent upon effective joining techAn improved method of joining metal components to matrix/fiber composite material structures has been invented. The method is particularly applicable to equipping such thin-wall polymer-matrix composite (PMC) structures as tanks with flanges, ceramic matrix composite (CMC) liners for high heat engine nozzles, and other metallic-to-composite attachments. The method is oriented toward new architectures and distributing mechanical loads as widely as possible in the vicinities of attachment locations to prevent excessive concentrations of stresses that could give rise to delaminations, debonds, leaks, and other failures. The method in its most basic form can be summarized as follows: A metal component is to be joined to a designated attachment area on a composite-material structure. In preparation for joining, the metal component is fabricated to include multiple studs projecting from the aforementioned face. Also in preparation for joining, holes just wide enough to accept the studs are molded into, drilled, or otherwise formed in the corresponding locations in the designated attachment area of the uncured ("wet') composite structure. The metal component is brought together with the uncured composite structure so that the studs become firmly seated in the holes, thereby causing the composite material to become intertwined with the metal component in the joining area. Alternately, it is proposed to utilize other mechanical attachment schemes whereby the uncured composite and metallic parts are joined with "z-direction" fasteners. The resulting "wet" assembly is then subjected to the composite-curing heat treatment, becoming a unitary structure. It should be noted that this new art will require different techniques for CMC s versus PMC's, but the final architecture and companion curing philosophy is the same. For instance, a chemical vapor infiltration (CVI) fabrication technique may require special integration of the pre-form and

Passive and Active Control of Space Structures (PACOSS)

NASA Astrophysics Data System (ADS)

Morosow, G.; Harcrow, H.; Rogers, L.

1985-04-01

Passive and Active Control of Space Structures (PACOSS) is a five-year program designed to investigate highly damped structures in conjunction with active control systems, and in particular to develop technology that integrates passive damping and active control to achieve precise pointing control. Major areas of research include metal matrix composites; viscoelastic materials; damping devices; dynamic test article design, fabrication and testing; and active damping.

Fusion of nacre, mussel, and lotus leaf: bio-inspired graphene composite paper with multifunctional integration

NASA Astrophysics Data System (ADS)

Zhong, Da; Yang, Qinglin; Guo, Lin; Dou, Shixue; Liu, Kesong; Jiang, Lei

2013-06-01

Multifunctional integration is an inherent characteristic for biological materials with multiscale structures. Learning from nature is an effective approach for scientists and engineers to construct multifunctional materials. In nature, mollusks (abalone), mussels, and the lotus have evolved different and optimized solutions to survive. Here, bio-inspired multifunctional graphene composite paper was fabricated in situ through the fusion of the different biological solutions from nacre (brick-and-mortar structure), mussel adhesive protein (adhesive property and reducing character), and the lotus leaf (self-cleaning effect). Owing to the special properties (self-polymerization, reduction, and adhesion), dopamine could be simultaneously used as a reducing agent for graphene oxide and as an adhesive, similar to the mortar in nacre, to crosslink the adjacent graphene. The resultant nacre-like graphene paper exhibited stable superhydrophobicity, self-cleaning, anti-corrosion, and remarkable mechanical properties underwater.Multifunctional integration is an inherent characteristic for biological materials with multiscale structures. Learning from nature is an effective approach for scientists and engineers to construct multifunctional materials. In nature, mollusks (abalone), mussels, and the lotus have evolved different and optimized solutions to survive. Here, bio-inspired multifunctional graphene composite paper was fabricated in situ through the fusion of the different biological solutions from nacre (brick-and-mortar structure), mussel adhesive protein (adhesive property and reducing character), and the lotus leaf (self-cleaning effect). Owing to the special properties (self-polymerization, reduction, and adhesion), dopamine could be simultaneously used as a reducing agent for graphene oxide and as an adhesive, similar to the mortar in nacre, to crosslink the adjacent graphene. The resultant nacre-like graphene paper exhibited stable superhydrophobicity, self-cleaning, anti-corrosion, and remarkable mechanical properties underwater. Electronic supplementary information (ESI) available. See DOI: 10.1039/c3nr33632h

Evaluation of Advanced Composite Structures Technologies for Application to NASA's Vision for Space Exploration

NASA Technical Reports Server (NTRS)

Messinger, Ross

2008-01-01

An assessment was performed to identify the applicability of composite material technologies to major structural elements of the NASA Constellation program. A qualitative technology assessment methodology was developed to document the relative benefit of 24 structural systems with respect to 33 major structural elements of Ares I, Orion, Ares V, and Altair. Technology maturity assessments and development plans were obtained from more than 30 Boeing subject matter experts for more than 100 technologies. These assessment results and technology plans were combined to generate a four-level hierarchy of recommendations. An overarching strategy is suggested, followed by a Constellation-wide development plan, three integrated technology demonstrations, and three focused projects for a task order follow-on.

Effect of the structure and mechanical properties of the near-surface layer of lithium niobate single crystals on the manufacture of integrated optic circuits

NASA Astrophysics Data System (ADS)

Sosunov, A. V.; Ponomarev, R. S.; Yur'ev, V. A.; Volyntsev, A. B.

2017-01-01

This paper shows that the near-surface layer of a lithium niobate single layer 15 μm in depth is essentially different from the rest of the volume of the material from the standpoint of composition, structure, and mechanical properties. The pointed out differences are due to the effect of cutting, polishing, and smoothing of the lithium niobate plates, which increase the density of point defects and dislocations. The increasing density of the structural defects leads to uncontrollable changes in the conditions of the formations of waveguides and the drifting of characteristics of integrated optical circuits. The results obtained are very important for the manufacture of lithium niobate based integrated optical circuits.

Design and fabrication of planar structures with graded electromagnetic properties

NASA Astrophysics Data System (ADS)

Good, Brandon Lowell

Successfully integrating electromagnetic properties in planar structures offers numerous benefits to the microwave and optical communities. This work aims at formulating new analytic and optimized design methods, creating new fabrication techniques for achieving those methods, and matching appropriate implementation of methods to fabrication techniques. The analytic method consists of modifying an approach that realizes perfect antireflective properties from graded profiles. This method is shown for all-dielectric and magneto-dielectric grading profiles. The optimized design methods are applied to transformer (discrete) or taper (continuous) designs. From these methods, a subtractive and an additive manufacturing technique were established and are described. The additive method, dry powder dot deposition, enables three dimensional varying electromagnetic properties in a structural composite. Combining the methods and fabrication is shown in two applied methodologies. The first uses dry powder dot deposition to design one dimensionally graded electromagnetic profiles in a planar fiberglass composite. The second method simultaneously applies antireflective properties and adjusts directivity through a slab through the use of subwavelength structures to achieve a flat antireflective lens. The end result of this work is a complete set of methods, formulations, and fabrication techniques to achieve integrated electromagnetic properties in planar structures.

Compressive failure modes and parameter optimization of the trabecular structure of biomimetic fully integrated honeycomb plates.

PubMed

Chen, Jinxiang; Tuo, Wanyong; Zhang, Xiaoming; He, Chenglin; Xie, Juan; Liu, Chang

2016-12-01

To develop lightweight biomimetic composite structures, the compressive failure and mechanical properties of fully integrated honeycomb plates were investigated experimentally and through the finite element method. The results indicated that: fracturing of the fully integrated honeycomb plates primarily occurred in the core layer, including the sealing edge structure. The morphological failures can be classified into two types, namely dislocations and compactions, and were caused primarily by the stress concentrations at the interfaces between the core layer and the upper and lower laminations and secondarily by the disordered short-fiber distribution in the material; although the fully integrated honeycomb plates manufactured in this experiment were imperfect, their mass-specific compressive strength was superior to that of similar biomimetic samples. Therefore, the proposed bio-inspired structure possesses good overall mechanical properties, and a range of parameters, such as the diameter of the transition arc, was defined for enhancing the design of fully integrated honeycomb plates and improving their compressive mechanical properties. Copyright © 2016 Elsevier B.V. All rights reserved.

Development of GENOA Progressive Failure Parallel Processing Software Systems

NASA Technical Reports Server (NTRS)

Abdi, Frank; Minnetyan, Levon

1999-01-01

A capability consisting of software development and experimental techniques has been developed and is described. The capability is integrated into GENOA-PFA to model polymer matrix composite (PMC) structures. The capability considers the physics and mechanics of composite materials and structure by integration of a hierarchical multilevel macro-scale (lamina, laminate, and structure) and micro scale (fiber, matrix, and interface) simulation analyses. The modeling involves (1) ply layering methodology utilizing FEM elements with through-the-thickness representation, (2) simulation of effects of material defects and conditions (e.g., voids, fiber waviness, and residual stress) on global static and cyclic fatigue strengths, (3) including material nonlinearities (by updating properties periodically) and geometrical nonlinearities (by Lagrangian updating), (4) simulating crack initiation. and growth to failure under static, cyclic, creep, and impact loads. (5) progressive fracture analysis to determine durability and damage tolerance. (6) identifying the percent contribution of various possible composite failure modes involved in critical damage events. and (7) determining sensitivities of failure modes to design parameters (e.g., fiber volume fraction, ply thickness, fiber orientation. and adhesive-bond thickness). GENOA-PFA progressive failure analysis is now ready for use to investigate the effects on structural responses to PMC material degradation from damage induced by static, cyclic (fatigue). creep, and impact loading in 2D/3D PMC structures subjected to hygrothermal environments. Its use will significantly facilitate targeting design parameter changes that will be most effective in reducing the probability of a given failure mode occurring.

Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Bowles, K. J.

1985-01-01

A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

Finite element analysis of drilling in carbon fiber reinforced polymer composites

NASA Astrophysics Data System (ADS)

Phadnis, V. A.; Roy, A.; Silberschmidt, V. V.

2012-08-01

Carbon fiber reinforced polymer composite (CFRP) laminates are attractive for many applications in the aerospace industry especially as aircraft structural components due to their superior properties. Usually drilling is an important final machining process for components made of composite laminates. In drilling of CFRP, it is an imperative task to determine the maximum critical thrust forces that trigger inter-laminar and intra-laminar damage modes owing to highly anisotropic fibrous media; and negotiate integrity of composite structures. In this paper, a 3D finite element (FE) model of drilling in CFRP composite laminate is developed, which accurately takes into account the dynamic characteristics involved in the process along with the accurate geometrical considerations. A user defined material model is developed to account for accurate though thickness response of composite laminates. The average critical thrust forces and torques obtained using FE analysis, for a set of machining parameters are found to be in good agreement with the experimental results from literature.

Evaluation of shear-compressive strength properties for laminated GFRP composites in electromagnet system

NASA Astrophysics Data System (ADS)

Song, Jun Hee; Kim, Hak Kun; Kim, Sam Yeon

2014-07-01

Laminated fiber-reinforced composites can be applied to an insulating structure of a nuclear fusion device. It is necessary to investigate the interlaminar fracture characteristics of the laminated composites for the assurance of design and structural integrity. The three methods used to prepare the glass fiber reinforced plastic composites tested in this study were vacuum pressure impregnation, high pressure laminate (HPL), and prepreg laminate. We discuss the design criteria for safe application of composites and the shear-compressive test methods for evaluating mechanical properties of the material. Shear-compressive tests could be performed successfully using series-type test jigs that were inclined 0°, 30°, 45°, 60°, and 75° to the normal axis. Shear strength depends strongly on the applied compressive stress. The design range of allowable shear stress was extended by use of the appropriate composite fabrication method. HPL had the largest design range, and the allowable interlaminar shear stress was 0.254 times the compressive stress.

Constitutive modeling and control of 1D smart composite structures

NASA Astrophysics Data System (ADS)

Briggs, Jonathan P.; Ostrowski, James P.; Ponte-Castaneda, Pedro

1998-07-01

Homogenization techniques for determining effective properties of composite materials may provide advantages for control of stiffness and strain in systems using hysteretic smart actuators embedded in a soft matrix. In this paper, a homogenized model of a 1D composite structure comprised of shape memory alloys and a rubber-like matrix is presented. With proportional and proportional/integral feedback, using current as the input state and global strain as an error state, implementation scenarios include the use of tractions on the boundaries and a nonlinear constitutive law for the matrix. The result is a simple model which captures the nonlinear behavior of the smart composite material system and is amenable to experiments with various control paradigms. The success of this approach in the context of the 1D model suggests that the homogenization method may prove useful in investigating control of more general smart structures. Applications of such materials could include active rehabilitation aids, e.g. wrist braces, as well as swimming/undulating robots, or adaptive molds for manufacturing processes.

Additive Manufacturing of Composites and Complex Materials

NASA Astrophysics Data System (ADS)

Spowart, Jonathan E.; Gupta, Nikhil; Lehmhus, Dirk

2018-03-01

Advanced composite materials form an important class of high-performance industrial materials used in weight-sensitive applications such as aerospace structures, automotive structures and sports equipment. In many of these applications, parts are made in small production runs, are highly customized and involve long process development times. Developments in additive manufacturing (AM) methods have helped in overcoming many of these limitations. The special topic of Additive Manufacturing of Composites and Complex Materials captures the state of the art in this area by collecting nine papers that present much novel advancement in this field. The studies under this topic show advancement in the area of AM of carbon fiber and graphene-reinforced composites with high thermal and electrical conductivities, development of new hollow glass particle-filled syntactic foam filaments for printing lightweight structures and integration of sensors or actuators during AM of metallic parts. Some of the studies are focused on process optimization or modification to increase the manufacturing speed or tuning manufacturing techniques to enable AM of new materials.

Scalable File Systems for High Performance Computing Final Report

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

Brandt, S A

2007-10-03

Simulations of mode I interlaminar fracture toughness tests of a carbon-reinforced composite material (BMS 8-212) were conducted with LSDYNA. The fracture toughness tests were performed by U.C. Berkeley. The simulations were performed to investigate the validity and practicality of employing decohesive elements to represent interlaminar bond failures that are prevalent in carbon-fiber composite structure penetration events. The simulations employed a decohesive element formulation that was verified on a simple two element model before being employed to perform the full model simulations. Care was required during the simulations to ensure that the explicit time integration of LSDYNA duplicate the near steady-statemore » testing conditions. In general, this study validated the use of employing decohesive elements to represent the interlaminar bond failures seen in carbon-fiber composite structures, but the practicality of employing the elements to represent the bond failures seen in carbon-fiber composite structures during penetration events was not established.« less

Investigation of contact acoustic nonlinearities on metal and composite airframe structures via intensity based health monitoring.

PubMed

Romano, P Q; Conlon, S C; Smith, E C

2013-01-01

Nonlinear structural intensity (NSI) and nonlinear structural surface intensity (NSSI) based damage detection techniques were improved and extended to metal and composite airframe structures. In this study, the measurement of NSI maps at sub-harmonic frequencies was completed to provide enhanced understanding of the energy flow characteristics associated with the damage induced contact acoustic nonlinearity mechanism. Important results include NSI source localization visualization at ultra-subharmonic (nf/2) frequencies, and damage detection results utilizing structural surface intensity in the nonlinear domain. A detection metric relying on modulated wave spectroscopy was developed and implemented using the NSSI feature. The data fusion of the intensity formulation provided a distinct advantage, as both the single interrogation frequency NSSI and its modulated wave extension (NSSI-MW) exhibited considerably higher sensitivities to damage than using single-sensor (strain or acceleration) nonlinear detection metrics. The active intensity based techniques were also extended to composite materials, and results show both NSSI and NSSI-MW can be used to detect damage in the bond line of an integrally stiffened composite plate structure with high sensitivity. Initial damage detection measurements made on an OH-58 tailboom (Penn State Applied Research Laboratory, State College, PA) indicate the techniques can be transitioned to complex airframe structures achieving high detection sensitivities with minimal sensors and actuators.

A Homogenization Approach for Design and Simulation of Blast Resistant Composites

NASA Astrophysics Data System (ADS)

Sheyka, Michael

Structural composites have been used in aerospace and structural engineering due to their high strength to weight ratio. Composite laminates have been successfully and extensively used in blast mitigation. This dissertation examines the use of the homogenization approach to design and simulate blast resistant composites. Three case studies are performed to examine the usefulness of different methods that may be used in designing and optimizing composite plates for blast resistance. The first case study utilizes a single degree of freedom system to simulate the blast and a reliability based approach. The first case study examines homogeneous plates and the optimal stacking sequence and plate thicknesses are determined. The second and third case studies use the homogenization method to calculate the properties of composite unit cell made of two different materials. The methods are integrated with dynamic simulation environments and advanced optimization algorithms. The second case study is 2-D and uses an implicit blast simulation, while the third case study is 3-D and simulates blast using the explicit blast method. Both case studies 2 and 3 rely on multi-objective genetic algorithms for the optimization process. Pareto optimal solutions are determined in case studies 2 and 3. Case study 3 is an integrative method for determining optimal stacking sequence, microstructure and plate thicknesses. The validity of the different methods such as homogenization, reliability, explicit blast modeling and multi-objective genetic algorithms are discussed. Possible extension of the methods to include strain rate effects and parallel computation is also examined.

Impact damage in filament wound composite bottles

NASA Technical Reports Server (NTRS)

Highsmith, Alton L.

1993-01-01

Increasingly, composite materials are being used in advanced structural applications because of the significant weight savings they offer when compared to more traditional engineering materials. The higher cost of composites must be offset by the increased performance that results from reduced structural weight if these new materials are to be used effectively. At present, there is considerable interest in fabricating solid rocket motor cases out of composite materials, and capitalizing on the reduced structural weight to increase rocket performance. However, one of the difficulties that arises when composite materials are used is that composites can develop significant amounts of internal damage during low velocity impacts. Such low velocity impacts may be encountered in routine handling of a structural component like a rocket motor case. The ability to assess the reduction in structural integrity of composite motor cases that experience accidental impacts is essential if composite rocket motor cases are to be certified for manned flight. While experimental studies of the post-impact performance of filament wound composite motor cases haven been proven performed (2,3), scaling impact data from small specimens to full scale structures has proven difficult. If such a scaling methodology is to be achieved, an increased understanding of the damage processes which influence residual strength is required. The study described herein was part of an ongoing investigation of damage development and reduction of tensile strength in filament wound composites subjected to low velocity impacts. The present study, which focused on documenting the damage that develops in filament wound composites as a result of such impacts, included two distinct tasks. The first task was to experimentally assess impact damage in small, filament wound pressure bottles using x-ray radiography. The second task was to study the feasibility of using digital image processing techniques to assist in determining the 3-D distribution of damage from stereo x-ray pairs.

Forest biomass, canopy structure, and species composition relationships with multipolarization L-band synthetic aperture radar data

NASA Technical Reports Server (NTRS)

Sader, Steven A.

1987-01-01

The effect of forest biomass, canopy structure, and species composition on L-band synthetic aperature radar data at 44 southern Mississippi bottomland hardwood and pine-hardwood forest sites was investigated. Cross-polarization mean digital values for pine forests were significantly correlated with green weight biomass and stand structure. Multiple linear regression with five forest structure variables provided a better integrated measure of canopy roughness and produced highly significant correlation coefficients for hardwood forests using HV/VV ratio only. Differences in biomass levels and canopy structure, including branching patterns and vertical canopy stratification, were important sources of volume scatter affecting multipolarization radar data. Standardized correction techniques and calibration of aircraft data, in addition to development of canopy models, are recommended for future investigations of forest biomass and structure using synthetic aperture radar.

A bioinspired study on the compressive resistance of helicoidal fibre structures

NASA Astrophysics Data System (ADS)

Tan, Ting; Ribbans, Brian

2017-10-01

Helicoidal fibre structures are widely observed in natural materials. In this paper, an integrated experimental and analytical approach was used to investigate the compressive resistance of helicoidal fibre structures. First, helicoidal fibre-reinforced composites were created using three-dimensionally printed helicoids and polymeric matrices, including plain, ring-reinforced and helix-reinforced helicoids. Then, load-displacement curves under monotonic compression tests were collected to measure the compressive strengths of helicoidal fibre composites. Fractographic characterization was performed using an X-ray microtomographer and scanning electron microscope, through which crack propagations in helicoidal structures were illustrated. Finally, mathematical modelling was performed to reveal the essential fibre architectures in the compressive resistance of helicoidal fibre structures. This work reveals that fibre-matrix ratios, helix pitch angles and interlayer rotary angles are critical to the compressive resistance of helicoidal structures.

Impact Damage and Strain Rate Effects for Toughened Epoxy Composite Structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Minnetyan, Levon

2006-01-01

Structural integrity of composite systems under dynamic impact loading is investigated herein. The GENOA virtual testing software environment is used to implement the effects of dynamic loading on fracture progression and damage tolerance. Combinations of graphite and glass fibers with a toughened epoxy matrix are investigated. The effect of a ceramic coating for the absorption of impact energy is also included. Impact and post impact simulations include verification and prediction of (1) Load and Impact Energy, (2) Impact Damage Size, (3) Maximum Impact Peak Load, (4) Residual Strength, (5) Maximum Displacement, (6) Contribution of Failure Modes to Failure Mechanisms, (7) Prediction of Impact Load Versus Time, and (8) Damage, and Fracture Pattern. A computer model is utilized for the assessment of structural response, progressive fracture, and defect/damage tolerance characteristics. Results show the damage progression sequence and the changes in the structural response characteristics due to dynamic impact. The fundamental premise of computational simulation is that the complete evaluation of composite fracture requires an assessment of ply and subply level damage/fracture processes as the structure is subjected to loads. Simulation results for the graphite/epoxy composite were compared with the impact and tension failure test data, correlation and verification was obtained that included: (1) impact energy, (2) damage size, (3) maximum impact peak load, (4) residual strength, (5) maximum displacement, and (6) failure mechanisms of the composite structure.

An Overview of Materials Structures for Extreme Environments Efforts for 2015 SBIR Phases I and II

NASA Technical Reports Server (NTRS)

Nguyen, Hung D.; Steele, Gynelle C.

2017-01-01

Technological innovation is the overall focus of NASA's Small Business Innovation Research (SBIR) program. The program invests in the development of innovative concepts and technologies to help NASA's mission directorates address critical research and development needs for Agency projects. This report highlights innovative SBIR 2015 Phase I and II projects that specifically address areas in Materials and Structures for Extreme Environments, one of six core competencies at NASA Glenn Research Center. Each article describes an innovation, defines its technical objective, and highlights NASA applications as well as commercial and industrial applications. Ten technologies are featured: metamaterials-inspired aerospace structures, metallic joining to advanced ceramic composites, multifunctional polyolefin matrix composite structures, integrated reacting fluid dynamics and predictive materials degradation models for propulsion system conditions, lightweight inflatable structural airlock (LISA), copolymer materials for fused deposition modeling 3-D printing of nonstandard plastics, Type II strained layer superlattice materials development for space-based focal plane array applications, hydrogenous polymer-regolith composites for radiation-shielding materials, a ceramic matrix composite environmental barrier coating durability model, and advanced composite truss printing for large solar array structures. This report serves as an opportunity for NASA engineers, researchers, program managers, and other personnel to learn about innovations in this technology area as well as possibilities for collaboration with innovative small businesses that could benefit NASA programs and projects.

Recent advances in aerospace composite NDE

NASA Astrophysics Data System (ADS)

Georgeson, Gary E.

2002-06-01

As the aerospace industry continues to advance the design and use of composite structure, the NDE community faces the difficulties of trying to keep up. The challenges lie in manufacturing evaluation of the newest aerospace structures and materials and the in-service inspection and monitoring of damaged or aging composites. This paper provides examples of several promising NDI applications in the world of aerospace composites. Airborne (or non-contact) Ultrasonic Testing (UT) has been available for decades, but recently has generated new interest due to significant improvements in transducer design and low noise electronics. Boeing is developing inspection techniques for composite joints and core blankets using this technology. In-service inspection techniques for thick, multi-layer structures are also being advanced. One effective technique integrates the S-9 Sondicator, a traditional bond testing device, with Boeing's Mobile Automated Scanner (MAUS) platform. Composite patches have seen limited use on-aircraft, due, in part, to the difficulty of determining the quality of a bonded joint. A unique approach using Electronic Speckle Pattern Interferometry (ESPI) is showing promise as a bonded patch-inspection method. Other NDI techniques currently being developed for aerospace application are also briefly discussed.

Integration of colloids into a semi-flexible network of fibrin.

PubMed

Bharadwaj, N Ashwin K; Kang, Jin Gu; Hatzell, Marta C; Schweizer, Kenneth S; Braun, Paul V; Ewoldt, Randy H

2017-02-15

Typical colloid-polymer composites have particle diameters much larger than the polymer mesh size, but successful integration of smaller colloids into a large-mesh network could allow for the realization of new colloidal states of spatial organization and faster colloid motion which can allow the possibility of switchable re-configuration of colloids or more dramatic stimuli-responsive property changes. Experimental realization of such composites requires solving non-trivial materials selection and fabrication challenges; key questions include composition regime maps of successful composites, the resulting structure and colloidal contact network, and the mechanical properties, in particular the ability to form a network and retain strain stiffening in the presence of colloids. Here, we study these fundamental questions by formulating composites with fluorescent (though not stimuli-responsive) carboxylate modified polystyrene/latex (CML) colloidal particles (diameters 200 nm and 1000 nm) in bovine fibrin networks (a semi-flexible biopolymer network with mesh size 1-5 μm). We describe and characterize two methods of composite preparation: adding colloids before fibrinogen polymerization (Method I), and electrophoretically driving colloids into a network already formed by fibrinogen polymerization (Method II). We directly image the morphology of colloidal and fibrous components with two-color fluorescent confocal microscopy under wet conditions and SEM of fixed dry samples. Mechanical properties are studied with shear and extensional rheology. Both fabrication methods are successful, though with trade-offs. Method I retains the nonlinear strain-stiffening and extensibility of the native fibrin network, but some colloid clustering is observed and fibrin network integrity is lost above a critical colloid concentration that depends on fibrinogen and thrombin concentration. Larger colloids can be included at higher volume fractions before massive aggregation occurs, indicating surface interactions as a limiting factor. Method II results in a loss of measurable strain-stiffening, but colloids are well dispersed and template along the fibrous scaffold. The results here, with insight into both structure and rheology, form a foundational understanding for the integration of other colloids, e.g. with stimuli-responsive functionalities, into semi-flexible networks.

Optimization of Layered Cathode Materials for Lithium-Ion Batteries

PubMed Central

Julien, Christian; Mauger, Alain; Zaghib, Karim; Groult, Henri

2016-01-01

This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi2MnO3•(1 − y)LiNi½Mn½O2 layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling. PMID:28773717

Fusion of nacre, mussel, and lotus leaf: bio-inspired graphene composite paper with multifunctional integration.

PubMed

Zhong, Da; Yang, Qinglin; Guo, Lin; Dou, Shixue; Liu, Kesong; Jiang, Lei

2013-07-07

Multifunctional integration is an inherent characteristic for biological materials with multiscale structures. Learning from nature is an effective approach for scientists and engineers to construct multifunctional materials. In nature, mollusks (abalone), mussels, and the lotus have evolved different and optimized solutions to survive. Here, bio-inspired multifunctional graphene composite paper was fabricated in situ through the fusion of the different biological solutions from nacre (brick-and-mortar structure), mussel adhesive protein (adhesive property and reducing character), and the lotus leaf (self-cleaning effect). Owing to the special properties (self-polymerization, reduction, and adhesion), dopamine could be simultaneously used as a reducing agent for graphene oxide and as an adhesive, similar to the mortar in nacre, to crosslink the adjacent graphene. The resultant nacre-like graphene paper exhibited stable superhydrophobicity, self-cleaning, anti-corrosion, and remarkable mechanical properties underwater.

Constraints on Composition, Structure and Evolution of the Lithosphere

NASA Astrophysics Data System (ADS)

Bianchini, Gianluca; Bonadiman, Costanza; Aulbach, Sonja; Schutt, Derek

2015-05-01

The idea for this special issue was triggered at the Goldschmidt Conference held in Florence (August 25-30, 2013), where we convened a session titled "Integrated Geophysical-Geochemical Constraints on Composition and Structure of the Lithosphere". The invitation to contribute was extended not only to the session participants but also to a wider spectrum of colleagues working on related topics. Consequently, a diverse group of Earth scientists encompassing geophysicists, geodynamicists, geochemists and petrologists contributed to this Volume, providing a comprehensive overview on the nature and evolution of lithospheric mantle by combining studies that exploit different types of data and interpretative approaches. The integration of geochemical and geodynamic datasets and their interpretation represents the state of the art in our knowledge of the lithosphere and beyond, and could serve as a blueprint for future strategies in concept and methodology to advance our knowledge of this and other terrestrial reservoirs.

Giant self-biased magnetoelectric coupling in co-fired textured layered composites

NASA Astrophysics Data System (ADS)

Yan, Yongke; Zhou, Yuan; Priya, Shashank

2013-02-01

Co-fired magnetostrictive/piezoelectric/magnetostrictive laminate structure with silver inner electrode was synthesized and characterized. We demonstrate integration of textured piezoelectric microstructure with the cost-effective low-temperature co-fired layered structure to achieve strong magnetoelectric coupling. Using the co-fired composite, a strategy was developed based upon the hysteretic response of nickel-copper-zinc ferrite magnetostrictive materials to achieve peak magnetoelectric response at zero DC bias, referred as self-biased magnetoelectric response. Fundamental understanding of self-bias phenomenon in composites with single phase magnetic material was investigated by quantifying the magnetization and piezomagnetic changes with applied DC field. We delineate the contribution arising from the interfacial strain and inherent magnetic hysteretic behavior of copper modified nickel-zinc ferrite towards self-bias response.

Hierarchical, porous CuS microspheres integrated with carbon nanotubes for high-performance supercapacitors

PubMed Central

Lu, Yang; Liu, Xianming; Wang, Weixiao; Cheng, Jinbing; Yan, Hailong; Tang, Chengchun; Kim, Jang-Kyo; Luo, Yongsong

2015-01-01

Carbon nanotubes (CNTs) incorporated porous 3-dimensional (3D) CuS microspheres have been successfully synthesized via a simple refluxing method assisted by PVP. The composites are composed of flower-shaped CuS secondary microspheres, which in turn are assembled with primary nanosheets of 15–30 nm in thickness and fully integrated with CNT. The composites possess a large specific surface area of 189.6 m2 g−1 and a high conductivity of 0.471 S cm−1. As electrode materials for supercapacitors, the nanocomposites show excellent cyclability and rate capability and deliver an average reversible capacitance as high as 1960 F g−1 at a current density of 10 mA cm−2 over 10000 cycles. The high electrochemical performance can be attributed to the synergistic effect of CNTs and the unique microstructure of CuS. The CNTs serve as not only a conductive agent to accelerate the transfer of electrons in the composites, but also as a buffer matrix to restrain the volume change and stabilize the electrode structure during the charge/discharge process. The porous structure of CuS also helps to stabilize the electrode structure and facilitates the transport for electrons. PMID:26568518

Response of a southern pine community to readjustment of stand structure

Treesearch

K.W. Outcalt; D.G. Brockway

2001-01-01

Widespread treatments are needed to restore ecological integrity to southern forest, but reintroduction of fire into these altered communities, is difficult. This study measured the effect on plant community structure and composition of an alternative mechanical treatment. In April, diameter was measured for tree stems grater than 5cm, while cover and frequency of...

Novel Composites for Wing and Fuselage Applications

NASA Technical Reports Server (NTRS)

Suarez, J. A.; Buttitta, C.

1996-01-01

Design development was successfully completed for textile preforms with continuous cross-stiffened epoxy panels with cut-outs. The preforms developed included 3-D angle interlock weaving of graphite structural fibers impregnated by resin film infiltration (RFI) and shown to be structurally suitable under conditions requiring minimum acquisition costs. Design guidelines/analysis methodology for such textile structures are given. The development was expanded to a fuselage side-panel component of a subsonic commercial airframe and found to be readily scalable. The successfully manufactured panel was delivered to NASA Langley for biaxial testing. This report covers the work performed under Task 3 -- Cross-Stiffened Subcomponent; Task 4 -- Design Guidelines/Analysis of Textile-Reinforced Composites; and Task 5 -- Integrally Woven Fuselage Panel.

SAW-Based Phononic Crystal Microfluidic Sensor—Microscale Realization of Velocimetry Approaches for Integrated Analytical Platform Applications

PubMed Central

Lucklum, Ralf; Zubtsov, Mikhail; Schmidt, Marc-Peter; Mukhin, Nikolay V.; Hirsch, Soeren

2017-01-01

The current work demonstrates a novel surface acoustic wave (SAW) based phononic crystal sensor approach that allows the integration of a velocimetry-based sensor concept into single chip integrated solutions, such as Lab-on-a-Chip devices. The introduced sensor platform merges advantages of ultrasonic velocimetry analytic systems and a microacoustic sensor approach. It is based on the analysis of structural resonances in a periodic composite arrangement of microfluidic channels confined within a liquid analyte. Completed theoretical and experimental investigations show the ability to utilize periodic structure localized modes for the detection of volumetric properties of liquids and prove the efficacy of the proposed sensor concept. PMID:28946609

SAW-Based Phononic Crystal Microfluidic Sensor-Microscale Realization of Velocimetry Approaches for Integrated Analytical Platform Applications.

PubMed

Oseev, Aleksandr; Lucklum, Ralf; Zubtsov, Mikhail; Schmidt, Marc-Peter; Mukhin, Nikolay V; Hirsch, Soeren

2017-09-23

The current work demonstrates a novel surface acoustic wave (SAW) based phononic crystal sensor approach that allows the integration of a velocimetry-based sensor concept into single chip integrated solutions, such as Lab-on-a-Chip devices. The introduced sensor platform merges advantages of ultrasonic velocimetry analytic systems and a microacoustic sensor approach. It is based on the analysis of structural resonances in a periodic composite arrangement of microfluidic channels confined within a liquid analyte. Completed theoretical and experimental investigations show the ability to utilize periodic structure localized modes for the detection of volumetric properties of liquids and prove the efficacy of the proposed sensor concept.

MANTECH project book

NASA Astrophysics Data System (ADS)

The effective integration of processes, systems, and procedures used in the production of aerospace systems using computer technology is managed by the Integration Technology Division (MTI). Under its auspices are the Information Management Branch, which is actively involved with information management, information sciences and integration, and the Implementation Branch, whose technology areas include computer integrated manufacturing, engineering design, operations research, and material handling and assembly. The Integration Technology Division combines design, manufacturing, and supportability functions within the same organization. The Processing and Fabrication Division manages programs to improve structural and nonstructural materials processing and fabrication. Within this division, the Metals Branch directs the manufacturing methods program for metals and metal matrix composites processing and fabrication. The Nonmetals Branch directs the manufacturing methods programs, which include all manufacturing processes for producing and utilizing propellants, plastics, resins, fibers, composites, fluid elastomers, ceramics, glasses, and coatings. The objective of the Industrial Base Analysis Division is to act as focal point for the USAF industrial base program for productivity, responsiveness, and preparedness planning.

NASA technology program for future civil air transports

NASA Technical Reports Server (NTRS)

Wright, H. T.

1983-01-01

An assessment is undertaken of the development status of technology, applicable to future civil air transport design, which is currently undergoing conceptual study or testing at NASA facilities. The NASA civil air transport effort emphasizes advanced aerodynamic computational capabilities, fuel-efficient engines, advanced turboprops, composite primary structure materials, advanced aerodynamic concepts in boundary layer laminarization and aircraft configuration, refined control, guidance and flight management systems, and the integration of all these design elements into optimal systems. Attention is given to such novel transport aircraft design concepts as forward swept wings, twin fuselages, sandwich composite structures, and swept blade propfans.

Optimizing isotope substitution in graphene for thermal conductivity minimization by genetic algorithm driven molecular simulations

NASA Astrophysics Data System (ADS)

Davies, Michael; Ganapathysubramanian, Baskar; Balasubramanian, Ganesh

2017-03-01

We present results from a computational framework integrating genetic algorithm and molecular dynamics simulations to systematically design isotope engineered graphene structures for reduced thermal conductivity. In addition to the effect of mass disorder, our results reveal the importance of atomic distribution on thermal conductivity for the same isotopic concentration. Distinct groups of isotope-substituted graphene sheets are identified based on the atomic composition and distribution. Our results show that in structures with equiatomic compositions, the enhanced scattering by lattice vibrations results in lower thermal conductivities due to the absence of isotopic clusters.

Foreign body impact event damage formation in composite structures

NASA Technical Reports Server (NTRS)

Bucinell, Ronald B.

1994-01-01

This report discusses a methodology that can be used to assess the effect of foreign body impacts on composite structural integrity. The described effort focuses on modeling the effect of a central impact on a 5 3/4 inch filament wound test article. The discussion will commence with details of the material modeling that was used to establish the input properties for the analytical model. This discussion is followed by an overview of the impact assessment methodology. The progress on this effort to date is reviewed along with a discussion of tasks that have yet to be completed.

Integrating community assembly and biodiversity to better understand ecosystem function: the Community Assembly and the Functioning of Ecosystems (CAFE) approach.

PubMed

Bannar-Martin, Katherine H; Kremer, Colin T; Ernest, S K Morgan; Leibold, Mathew A; Auge, Harald; Chase, Jonathan; Declerck, Steven A J; Eisenhauer, Nico; Harpole, Stanley; Hillebrand, Helmut; Isbell, Forest; Koffel, Thomas; Larsen, Stefano; Narwani, Anita; Petermann, Jana S; Roscher, Christiane; Cabral, Juliano Sarmento; Supp, Sarah R

2018-02-01

The research of a generation of ecologists was catalysed by the recognition that the number and identity of species in communities influences the functioning of ecosystems. The relationship between biodiversity and ecosystem functioning (BEF) is most often examined by controlling species richness and randomising community composition. In natural systems, biodiversity changes are often part of a bigger community assembly dynamic. Therefore, focusing on community assembly and the functioning of ecosystems (CAFE), by integrating both species richness and composition through species gains, losses and changes in abundance, will better reveal how community changes affect ecosystem function. We synthesise the BEF and CAFE perspectives using an ecological application of the Price equation, which partitions the contributions of richness and composition to function. Using empirical examples, we show how the CAFE approach reveals important contributions of composition to function. These examples show how changes in species richness and composition driven by environmental perturbations can work in concert or antagonistically to influence ecosystem function. Considering how communities change in an integrative fashion, rather than focusing on one axis of community structure at a time, will improve our ability to anticipate and predict changes in ecosystem function. © 2017 The Authors. Ecology Letters published by CNRS and John Wiley & Sons Ltd.

Ceramic honeycomb structures and the method thereof

NASA Technical Reports Server (NTRS)

Riccitiello, Salvatore R. (Inventor); Cagliostro, Domenick E. (Inventor)

1987-01-01

The subject invention pertains to a method of producing an improved composite-composite honeycomb structure for aircraft or aerospace use. Specifically, the subject invention relates to a method for the production of a lightweight ceramic-ceramic composite honeycomb structure, which method comprises: (1) pyrolyzing a loosely woven fabric/binder having a honeycomb shape and having a high char yield and geometric integrity after pyrolysis at between about 700 and 1,100 C; (2) substantially evenly depositing at least one layer of ceramic material on the pyrolyzed fabric/binder of step (1); (3) recovering the coated ceramic honeycomb structure; (4) removing the pyrolyzed fabric/binder of the structure of step (3) by slow pyrolysis at between 700 and 1000 C in between about a 2 to 5% by volume oxygen atmosphere for between about 0.5 and 5 hr.; and (5) substantially evenly depositing on and within the rigid hollow honeycomb structure at least one additional layer of the same or a different ceramic material by chemical vapor deposition and chemical vapor infiltration. The honeycomb shaped ceramic articles have enhanced physical properties and are useful in aircraft and aerospace uses.

Advances in Micromechanics Modeling of Composites Structures for Structural Health Monitoring

NASA Astrophysics Data System (ADS)

Moncada, Albert

Although high performance, light-weight composites are increasingly being used in applications ranging from aircraft, rotorcraft, weapon systems and ground vehicles, the assurance of structural reliability remains a critical issue. In composites, damage is absorbed through various fracture processes, including fiber failure, matrix cracking and delamination. An important element in achieving reliable composite systems is a strong capability of assessing and inspecting physical damage of critical structural components. Installation of a robust Structural Health Monitoring (SHM) system would be very valuable in detecting the onset of composite failure. A number of major issues still require serious attention in connection with the research and development aspects of sensor-integrated reliable SHM systems for composite structures. In particular, the sensitivity of currently available sensor systems does not allow detection of micro level damage; this limits the capability of data driven SHM systems. As a fundamental layer in SHM, modeling can provide in-depth information on material and structural behavior for sensing and detection, as well as data for learning algorithms. This dissertation focuses on the development of a multiscale analysis framework, which is used to detect various forms of damage in complex composite structures. A generalized method of cells based micromechanics analysis, as implemented in NASA's MAC/GMC code, is used for the micro-level analysis. First, a baseline study of MAC/GMC is performed to determine the governing failure theories that best capture the damage progression. The deficiencies associated with various layups and loading conditions are addressed. In most micromechanics analysis, a representative unit cell (RUC) with a common fiber packing arrangement is used. The effect of variation in this arrangement within the RUC has been studied and results indicate this variation influences the macro-scale effective material properties and failure stresses. The developed model has been used to simulate impact damage in a composite beam and an airfoil structure. The model data was verified through active interrogation using piezoelectric sensors. The multiscale model was further extended to develop a coupled damage and wave attenuation model, which was used to study different damage states such as fiber-matrix debonding in composite structures with surface bonded piezoelectric sensors.

An Overview of Integration and Test of the James Webb Space Telescope Integrated Science Instrument Module

NASA Technical Reports Server (NTRS)

Drury, Michael; Becker, Neil; Bos, Brent; Davila, Pamela; Frey, Bradley; Hylan, Jason; Marsh, James; McGuffey, Douglas; Novak, Maria; Ohl, Raymond;

Spider Silk Spun and Integrated into Composites

DTIC Science & Technology

2009-02-20

and elongation of sericin is lower than those of fibroin and, finally, (0 local shear damage is dominant in damaged sericin between fibres, while the... sericin at fibre-joint often shows microflow. These analytical studies are presently being expanded to include synthetic composites made of both...with sericin . Such a cocoon consists of three main parts: an outermost loose mesh structure, the middle shell layers and the innermost tetelette; all

3D Rheological Modeling of NW Intraplate Europe, Deciphering Spatial Integrated strength patterns, Mechanical Strong Layering and EET

NASA Astrophysics Data System (ADS)

Beekman, F.; Hardebol, N.; Cloetingh, S.; Tesauro, M.

2006-12-01

Better understanding of 3D rheological heterogeneity of the European Lithosphere provide the key to tie the recorded intraplate deformation pattern to stress fields transmitted into plate interior from plate boundary forces. The first order strain patterns result from stresses transmitted through the European lithosphere that is marked by a patchwork of high strength variability from inherited structural and compositional heterogeneities and upper mantle thermal perturbations. As the lithospheric rheology depends primarily on its spatial structure, composition and thermal estate, the 3D strength model for the European lithosphere relies on a 3D compositional model that yields the compositional heterogeneities and an iteratively calculated thermal cube using Fouriers law for heat conduction. The accurate appraisal of spatial strength variability results from proper mapping and integration of the geophysical compositional and thermal input parameters. Therefore, much attention has been paid to a proper description of first order structural and tectonic features that facilitate compilation of the compositional and thermal input models. As such, the 3D strength model reflects the thermo-mechanical structure inherited from the Europeans polyphase deformation history. Major 3D spatial mechanical strength variability has been revealed. The East-European and Fennoscandian Craton to the NE exhibit high strength (30-50 1012 N/m) from low mantle temperatures and surface heatflow of 35-60 mW/m2 while central and western Europe reflect a polyphase Phanerozoic thermo- tectonic history. Here, regions with high rigidity are formed primarily by patches of thermally stabilized Variscan Massifs (e.g. Rhenish, Armorican, Bohemian, and Iberian Massif) with low heatflow and lithospheric thickness values (50-65 mW/m2; 110-150 km) yielding strengths of ~15-25 1012 N/m. In contrast, major axis of weakened lithosphere coincides with Cenozoic Rift System (e.g. Upper and Lower Rhine Grabens, Pannonian Basin and Massif Central) attributed to the presence of tomographically imaged plumes. This study has elucidated the memory of the present-days Europeans lithosphere induced by compositional and thermal heterogeneities. The resulting lateral strength variations has a clear signature of the pst lithospheres polyphase deformation and also entails active tectonics, tectonically induced topography and surface processes.

Modeling approaches for the simulation of ultrasonic inspections of anisotropic composite structures in the CIVA software platform

NASA Astrophysics Data System (ADS)

Jezzine, Karim; Imperiale, Alexandre; Demaldent, Edouard; Le Bourdais, Florian; Calmon, Pierre; Dominguez, Nicolas

2018-04-01

Models for the simulation of ultrasonic inspections of flat and curved plate-like composite structures, as well as stiffeners, are available in the CIVA-COMPOSITE module released in 2016. A first modelling approach using a ray-based model is able to predict the ultrasonic propagation in an anisotropic effective medium obtained after having homogenized the composite laminate. Fast 3D computations can be performed on configurations featuring delaminations, flat bottom holes or inclusions for example. In addition, computations on ply waviness using this model will be available in CIVA 2017. Another approach is proposed in the CIVA-COMPOSITE module. It is based on the coupling of CIVA ray-based model and a finite difference scheme in time domain (FDTD) developed by AIRBUS. The ray model handles the ultrasonic propagation between the transducer and the FDTD computation zone that surrounds the composite part. In this way, the computational efficiency is preserved and the ultrasound scattering by the composite structure can be predicted. Alternatively, a high order finite element approach is currently developed at CEA but not yet integrated in CIVA. The advantages of this approach will be discussed and first simulation results on Carbon Fiber Reinforced Polymers (CFRP) will be shown. Finally, the application of these modelling tools to the construction of metamodels is discussed.

Study of Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James L.; Workman, Gary L.

1997-01-01

The nondestructive evaluation (NDE) of future propulsion systems utilizing advanced composite structures for the storage of cryogenic fuels, such as liquid hydrogen or oxygen, presents many challenges. Economic justification for these structures requires light weight, reusable components with an infrastructure allowing periodic evaluation of structural integrity after enduring demanding stresses during operation. A major focus has been placed on the use of acoustic emission NDE to detect propagating defects, in service, necessitating an extensive study into characterizing the nature of acoustic signal propagation at very low temperatures and developing the methodology of applying AE sensors to monitor cryogenic components. This work addresses the question of sensor performance in the cryogenic environment. Problems involving sensor mounting, spectral response and durability are addressed. The results of this work provides a common point of measure from which sensor selection can be made when testing composite components at cryogenic temperatures.

Fracture mechanics methodology: Evaluation of structural components integrity

NASA Astrophysics Data System (ADS)

Sih, G. C.; de Oliveira Faria, L.

1984-09-01

The application of fracture mechanics to structural-design problems is discussed in lectures presented in the AGARD Fracture Mechanics Methodology course held in Lisbon, Portugal, in June 1981. The emphasis is on aeronautical design, and chapters are included on fatigue-life prediction for metals and composites, the fracture mechanics of engineering structural components, failure mechanics and damage evaluation of structural components, flaw-acceptance methods, and reliability in probabilistic design. Graphs, diagrams, drawings, and photographs are provided.

Adhesive bonded structural repair. I - Materials and processes, damage assessment and repair

NASA Astrophysics Data System (ADS)

Wegman, Raymond F.; Tullos, Thomas R.

1993-08-01

A standard method for the repair of adhesive bonded and composite laminate structures is introduced. Suitable materials and equipment for making satisfactory repairs are identified. Methods by which structures may be inspected, both before and after repair, are discussed. The objective in selecting the methods and materials is to restore the structure to its original integrity, i.e., to make a permanent repair. The use of these methods is recommended to promote standardized repair procedures.

Damage Detection and Self-Repair in Inflatable/Deployable Structures

NASA Technical Reports Server (NTRS)

Brandon, Erik; Studor, George; Banks, DAvid; Curry, Mark; Broccato, Robert; Jackson, Tom; Champaigne, Kevin; Sottos, Nancy

2009-01-01

Inflatable/deployable structures are under consideration for applications as varied as expansion modules for the International Space Station to destinations for space tourism to habitats for the lunar surface. Monitoring and maintaining the integrity of the physical structure is critical, particularly since these structures rely on non-traditional engineering materials such as fabrics, foams, and elastomeric polymers to provide the primary protection for the human crew. The closely related prior concept of monitoring structural integrity by use of built-in or permanently attached sensors has been applied to structures made of such standard engineering materials as metals, alloys, and rigid composites. To effect monitoring of flexible structures comprised mainly of soft goods, however, it will be necessary to solve a different set of problems - especially those of integrating power and data-transfer cabling that can withstand, and not unduly interfere with, stowage and subsequent deployment of the structures. By incorporating capabilities for self-repair along with capabilities for structural health monitoring, successful implementation of these technologies would be a significant step toward semi-autonomous structures, which need little human intervention to maintain. This would not only increase the safety of these structures, but also reduce the inspection and maintenance costs associated with more conventional structures.

Integrated evaluation of the geology, aerogammaspectrometry and aeromagnetometry of the Sul-Riograndense Shield, southernmost Brazil.

PubMed

Hartmann, Léo A; Lopes, William R; Savian, Jairo F

2016-03-01

An integrated evaluation of geology, aerogammaspectrometry and aeromagnetometry of the Sul-Riogran-dense Shield is permitted by the advanced stage of understanding of the geology and geochronology of the southern Brazilian Shield and a 2010 airborne geophysical survey. Gamma rays are registered from the rocks near the surface and thus describe the distribution of major units in the shield, such as the Pelotas batholith, the juvenile São Gabriel terrane, the granulite-amphibolite facies Taquarembó terrane and the numerous granite intrusions in the foreland. Major structures are also observed, e.g., the Dorsal de Canguçu shear. Magnetic signals register near surface crustal compositions (analytic signal) and total crust composition (total magnetic signal), so their variation as measured indicates either shallow or whole crustal structures. The Caçapava shear is outstanding on the images as is the magnetic low along the N-S central portion of the shield. These integrated observations lead to the deepening of the understanding of the largest and even detailed structures of the Sul-Riograndense Shield, some to be correlated to field geology in future studies. Most significant is the presence of different provinces and their limits depending on the method used for data acquisition - geology, aerogammaspectrometry or aeromagnetometry.

Embedded Bragg grating fiber optic sensor for composite flexbeams

NASA Astrophysics Data System (ADS)

Bullock, Daniel; Dunphy, James; Hufstetler, Gerard

1993-03-01

An embedded fiber-optic (F-O) sensor has been developed for translaminar monitoring of the structural integrity of composites, with a view to application in composite helicopter flexbeams for bearingless main rotor hubs. This through-thickness strain sensor is much more sensitive than conventional in-plane embedded F-O sensors to ply delamination, on the basis of a novel insertion technique and innovative Bragg grating sensor. Experimental trials have demonstrated the detection by this means of potential failures in advance of the edge-delamination or crack-propagation effect.

Fabricating Composite-Material Structures Containing SMA Ribbons

NASA Technical Reports Server (NTRS)

Turner, Travis L.; Cano, Roberto J.; Lach, Cynthia L.

2003-01-01

An improved method of designing and fabricating laminated composite-material (matrix/fiber) structures containing embedded shape-memory-alloy (SMA) actuators has been devised. Structures made by this method have repeatable, predictable properties, and fabrication processes can readily be automated. Such structures, denoted as shape-memory-alloy hybrid composite (SMAHC) structures, have been investigated for their potential to satisfy requirements to control the shapes or thermoelastic responses of themselves or of other structures into which they might be incorporated, or to control noise and vibrations. Much of the prior work on SMAHC structures has involved the use SMA wires embedded within matrices or within sleeves through parent structures. The disadvantages of using SMA wires as the embedded actuators include (1) complexity of fabrication procedures because of the relatively large numbers of actuators usually needed; (2) sensitivity to actuator/ matrix interface flaws because voids can be of significant size, relative to wires; (3) relatively high rates of breakage of actuators during curing of matrix materials because of sensitivity to stress concentrations at mechanical restraints; and (4) difficulty of achieving desirable overall volume fractions of SMA wires when trying to optimize the integration of the wires by placing them in selected layers only.

Porous composite prosthetic pylon for integration with skin and bone

PubMed Central

Pitkin, Mark; Raykhtsaum, Grigory; Pilling, John; Galibin, Oleg V.; Protasov, Mikhail V.; Chihovskaya, Julie V.; Belyaeva, Irina G.; Blinova, Miralda I.; Yudintseva, Natalia M.; Potokin, Igor L.; Pinaev, George P.; Moxson, Vladimir; Duz, Volodimir

2012-01-01

This article presents results of the further development and testing of the “skin and bone integrated pylon” (SBIP-1) for percutaneous (through skin) connection of the residual bone with an external limb prosthesis. We investigated a composite structure (called the SBIP-2) made of titanium particles and fine wires using mathematical modeling and mechanical testing. Results showed that the strength of the pylon was comparable with that of anatomical bone. In vitro and in vivo animal studies on 30 rats showed that the reinforcement of the composite pylon did not compromise its previously shown capacity for inviting skin and bone cell ingrowth through the device. These findings provide evidence for the safe and reliable long-term percutaneous transfer of vital and therapeutic substances, signals, and necessary forces and moments from a prosthetic device to the body. PMID:17943684

Progressive Fracture of Fiber Composite Thin Shell Structures Under Internal Pressure and Axial Loads

NASA Technical Reports Server (NTRS)

Gotsis, Pascal K.; Chamis, Christos C.; Minnetyan, Levon

1996-01-01

Graphite/epoxy composite thin shell structures were simulated to investigate damage and fracture progression due to internal pressure and axial loading. Defective and defect-free structures (thin cylinders) were examined. The three different laminates examined had fiber orientations of (90/0/+/-0)(sub s), where 0 is 45, 60, and 75 deg. CODSTRAN, an integrated computer code that scales up constituent level properties to the structural level and accounts for all possible failure modes, was used to simulate composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture were included in the simulation. Burst pressures for defective and defect-free shells were compared to evaluate damage tolerance. The results showed that damage initiation began with matrix failure whereas damage and/or fracture progression occurred as a result of additional matrix failure and fiber fracture. In both thin cylinder cases examined (defective and defect-free), the optimum layup configuration was (90/0/+/-60)(sub s) because it had the best damage tolerance with respect to the burst pressure.

Online Damage Detection on Metal and Composite Space Structures by Active and Passive Acoustic Methods

NASA Astrophysics Data System (ADS)

Scheerer, M.; Cardone, T.; Rapisarda, A.; Ottaviano, S.; Ftancesconi, D.

2012-07-01

In the frame of ESA funded programme Future Launcher Preparatory Programme Period 1 “Preparatory Activities on M&S”, Aerospace & Advanced Composites and Thales Alenia Space-Italia, have conceived and tested a structural health monitoring approach based on integrated Acoustic Emission - Active Ultrasound Damage Identification. The monitoring methods implemented in the study are both passive and active methods and the purpose is to cover large areas with a sufficient damage size detection capability. Two representative space sub-structures have been built and tested: a composite overwrapped pressure vessel (COPV) and a curved, stiffened Al-Li panel. In each structure, typical critical damages have been introduced: delaminations caused by impacts in the COPV and a crack in the stiffener of the Al-Li panel which was grown during a fatigue test campaign. The location and severity of both types of damages have been successfully assessed online using two commercially available systems: one 6 channel AE system from Vallen and one 64 channel AU system from Acellent.

Overview of demonstrator program of Japanese Smart Materials and Structure System project

NASA Astrophysics Data System (ADS)

Tajima, Naoyuki; Sakurai, Tateo; Sasajima, Mikio; Takeda, Nobuo; Kishi, Teruo

2003-08-01

The Japanese Smart Material and Structure System Project started in 1998 as five years' program that funded by METI (Ministry of Economy, Trade and Industry) and supported by NEDO (New Energy and Industrial Technology Development Organization). Total budget of five years was finally about 3.8 billion Japanese yen. This project has been conducted as the Academic Institutions Centered Program, namely, one of collaborated research and development among seven universities (include one foreign university), seventeen Industries (include two foreign companies), and three national laboratories. At first, this project consisted of four research groups that were structural health monitoring, smart manufacturing, active/adaptive structures, and actuator material/devices. Two years later, we decided that two demonstrator programs should be added in order to integrate the developed sensor and actuator element into the smart structure system and verify the research and development results of above four research groups. The application target of these demonstrators was focused to the airplane, and two demonstrators that these shapes simulate to the fuselage of small commercial airplane (for example, Boeing B737) had been established. Both demonstrators are cylindrical structures with 1.5 m in diameter and 3 m in length that the first demonstrator has CFRP skin-stringer and the second one has CFRP skin. The first demonstrator integrates the following six innovative techniques: (1) impact monitoring using embedded small diameter optical fiber sensors newly developed in this program, (2) impact monitoring using the integrated acoustic emission (AE) systems, (3) whole-field strain mapping using the BOTDR/FBG integrated system, (4) damage suppression using embedded shape memory alloy (SMA) films, (5) maximum and cyclic strain sensing using smart composite patches, and (6) smart manufacturing using the integrated sensing system. The second one is for demonstrating the suppression of vibration and acoustic noise generated in the composite cylindrical structure. In this program, High-performance PZT actuators/sensors developed in this program are also installed. The whole tests and evaluations have now been finished. This paper presents the outline of demonstrator programs, followed by six presentations that show the detail verification results of industrial demonstration themes.

Nano-composite magnetic material embedded on TiO2 pillars to realize magneto-optical resonant guided mode gratings

NASA Astrophysics Data System (ADS)

Varghese, B.; Gamet, E.; Jamon, D.; Neveu, S.; Berthod, L.; Shavdina, O.; Reynaud, S.; Verrier, I.; Veillas, C.; Royer, F.

2016-02-01

Periodic structuration of magnetic material is a way to enhance the magneto-optical behavior of optical devices like isolators. It is useful to reduce the footprint of such integrated devices or to improve their features. However, the structuration and/or integration of efficient magnetic materials on photonic platforms is still a difficult problem, because classical magneto-optical materials require an annealing temperature as high as 700°C. A novel wafer-scale approach is to incorporate that material into an already structured template through a single step deposition at low temperature. Using the dip-coating method, a magneto-optical thin film (~300nm) of CoFe2O4 nanoparticles in silica matrix prepared by sol-gel technique was coated on a 1D and 2D TiO2 subwavelength gratings. Such gratings were realized by the patterning of TiO2 films obtained by a sol-gel process. It was confirmed by Scanning Electron Microscope images that the magneto-optical composite completely occupies the voids of the 2D structuration showing a good compatibility between both materials. This composite shows a specific Faraday rotation of about 200°cm-1 at 1,5μm for 1% of volume fraction of nanoparticles. Spectral studies of the transmission and the reflection of a 1D TiO2 grating filled with the MO composite have evidenced the presence of a guided-mode optical resonance at 1,55μm. The position of this resonance was confirmed by numerical simulations, as well as its quite low efficiency. Based on simulations results, one can conclude that an increase of the grating depth is required to improve the efficiency of the resonance.

How Membrane-Active Peptides Get into Lipid Membranes.

PubMed

Sani, Marc-Antoine; Separovic, Frances

2016-06-21

The structure-function relationship for a family of antimicrobial peptides (AMPs) from the skin of Australian tree frogs is discussed and compared with that of peptide toxins from bee and Australian scorpion venoms. Although these membrane-active peptides induce a similar cellular fate by disrupting the lipid bilayer integrity, their lytic activity is achieved via different modes of action, which are investigated in relation to amino acid sequence, secondary structure, and membrane lipid composition. In order to better understand what structural features govern the interaction between peptides and lipid membranes, cell-penetrating peptides (CPPs), which translocate through the membrane without compromising its integrity, are also discussed. AMPs possess membrane lytic activities that are naturally designed to target the cellular membrane of pathogens or competitors. They are extremely diverse in amino acid composition and often show specificity against a particular strain of microbe. Since our antibiotic arsenal is declining precariously in the face of the rise in multiantibiotic resistance, AMPs increasingly are seen as a promising alternative. In an effort to understand their molecular mechanism, biophysical studies of a myriad of AMPs have been reported, yet no unifying mechanism has emerged, rendering difficult the rational design of drug leads. Similarly, a wide variety of cytotoxic peptides are found in venoms, the best known being melittin, yet again, predicting their activity based on a particular amino acid composition or secondary structure remains elusive. A common feature of these membrane-active peptides is their preference for the lipid environment. Indeed, they are mainly unstructured in solution and, in the presence of lipid membranes, quickly adsorb onto the surface, change their secondary structure, eventually insert into the hydrophobic core of the membrane bilayer, and finally disrupt the bilayer integrity. These steps define the molecular mechanism by which these membrane-active peptides lyse membranes. The last class of membrane-active peptides discussed are the CPPs, which translocate across the lipid bilayer without inducing severe disruption and have potential as drug vehicles. CPPs are typically highly charged and can show antimicrobial activity by targeting an intracellular target rather than via a direct membrane lytic mechanism. A critical aspect in the structure-function relationship of membrane-active peptides is their specific activity relative to the lipid membrane composition of the cell target. Cell membranes have a wide diversity of lipids, and those of eukaryotic and prokaryotic species differ greatly in composition and structure. The activity of AMPs from Australian tree frogs, toxins, and CPPs has been investigated within various lipid systems to assess whether a relationship between peptide and membrane composition could be identified. NMR spectroscopy techniques are being used to gain atomistic details of how these membrane-active peptides interact with model membranes and cells, and in particular, competitive assays demonstrate the difference between affinity and activity for a specific lipid environment. Overall, the interactions between these relatively small sized peptides and various lipid bilayers give insight into how these peptides function at the membrane interface.

High Performance Piezoelectric Thin Films for Shape Control in Large Inflatable Structures

NASA Technical Reports Server (NTRS)

Neurgaonkar, R. R.; Nelson, J. G.

1999-01-01

The objective of this research and development program was to develop PbZr(1-x)Ti(x)O3 (PZT) and Pb(1-x)Ba(x)Nb2O6 (PBN) materials with large piezoelectric response which are suitable for shape control in large inflatable structures. Two approaches were to be considered: (1) direct deposition of PZT and PBN films on flexible plastic or thin metal foil substrates, and (2) deposition on Si followed by fabrication of hybrid structures on mylar or kapton. Testing in shape control concepts was carried out at JPL and based on their results, the required modifications were made in the final film compositions and deposition techniques. The program objective was to identify and then optimize piezoelectric materials for NASA shape control applications. This involved the bulk piezoelectric and photovoltaic responses and the compatibility of the thin films with appropriate substrate structures. Within the PZT system, Rockwell has achieved the highest reported piezoelectric coefficient (d(sub 33) greater than 100 pC/N) of any ceramic composition. We used this experience in piezoelectric technology to establish compositions that can effectively address the issues of this program. The performance of piezoelectric thin films depends directly on d(sub ij) and Epsilon. The challenge was to find PZT compositions that maintained high d(sub ij) and Epsilon, while also exhibiting a large photovoltaic effect and integrate thin films of this composition into the system structure necessary to meet shape control applications. During the course of this program, several PZT and PLZT compositions were identified that meet these requirements. Two such compositions were successfully used in electrical and optical actuation studies of thin film structures.

High Performance Piezoelectric Thin Films for Shape Control in Large Inflatable Structures

NASA Technical Reports Server (NTRS)

Neurgaonkar, R. R.; Nelson, J. G.

1999-01-01

The objective of this research and development program was to develop PbZr(1-x)Ti(x)O3 (PZT) and Pb(1-x)Ba(x)Nb2O6 (PBN) materials with large piezoelectric response which are suitable for shape control in large inflatable structures. Two approaches were to be considered: (1) direct deposition of PZT and PBN films on flexible plastic or thin metal foil substrates, and (2) deposition on Si followed by fabrication of hybrid structures on mylar or kapton. Testing in shape control concepts was carried out at JPL and based on their results, the required modifications were made in the final film compositions and deposition techniques. The program objective was to identify and then optimize piezoelectric materials for NASA shape control applications. This involved the bulk piezoelectric and photovoltaic responses and the compatibility of the thin films with appropriate substrate structures. Within the PZT system, Rockwell has achieved the highest reported piezoelectric coefficient (d(sub 33) greater than 100 pC/N) of any ceramic composition. We used this experience in piezoelectric technology to establish compositions that can effectively address the issues of this program. The performance of piezoelectric thin films depends directly on d(sub ij) and epsilin. The challenge was to find PZT compositions that maintained high d(sub ij) and epsilon, while also exhibiting a large photovoltaic effect and integrate thin films of this composition into the system structure necessary to meet shape control applications. During the course of this program, several PZT and PLZT compositions were identified that meet these requirements. Two such compositions were successfully used in electrical and optical actuation studies of thin film structures.

Airborne Transducer Integrity under Operational Environment for Structural Health Monitoring

PubMed Central

Salmanpour, Mohammad Saleh; Sharif Khodaei, Zahra; Aliabadi, Mohammad Hossein

2016-01-01

This paper investigates the robustness of permanently mounted transducers used in airborne structural health monitoring systems, when exposed to the operational environment. Typical airliners operate in a range of conditions, hence, structural health monitoring (SHM) transducer robustness and integrity must be demonstrated for these environments. A set of extreme temperature, altitude and vibration environment test profiles are developed using the existing Radio Technical Commission for Aeronautics (RTCA)/DO-160 test methods. Commercially available transducers and manufactured versions bonded to carbon fibre reinforced polymer (CFRP) composite materials are tested. It was found that the DuraAct transducer is robust to environmental conditions tested, while the other transducer types degrade under the same conditions. PMID:27973450

Probabilistic structural analysis using a general purpose finite element program

NASA Astrophysics Data System (ADS)

Riha, D. S.; Millwater, H. R.; Thacker, B. H.

1992-07-01

This paper presents an accurate and efficient method to predict the probabilistic response for structural response quantities, such as stress, displacement, natural frequencies, and buckling loads, by combining the capabilities of MSC/NASTRAN, including design sensitivity analysis and fast probability integration. Two probabilistic structural analysis examples have been performed and verified by comparison with Monte Carlo simulation of the analytical solution. The first example consists of a cantilevered plate with several point loads. The second example is a probabilistic buckling analysis of a simply supported composite plate under in-plane loading. The coupling of MSC/NASTRAN and fast probability integration is shown to be orders of magnitude more efficient than Monte Carlo simulation with excellent accuracy.

Introduction to natural disturbances and historic range of variation: type, frequency, severity, and post-disturbance structure in central hardwood forests

Treesearch

Katie Greenberg; Beverly S. Collins; Henry McNab; Douglas K. Miller; Gary R. Wein

2015-01-01

EXCERPT FROM: Natural Disturbances and Historic Range Variation 2015. Throughout the history of upland hardwood forests of the Central Hardwood Region, natural disturbances have been integral to shaping forest structure and composition, and essential in maintaining diverse biotic...

Health Monitoring of Composite Material Structures using a Vibrometry Technique

NASA Technical Reports Server (NTRS)

Schulz, Mark J.

1997-01-01

Large composite material structures such as aircraft and Reusable Launch Vehicles (RLVS) operate in severe environments comprised of vehicle dynamic loads, aerodynamic loads, engine vibration, foreign object impact, lightning strikes, corrosion, and moisture absorption. These structures are susceptible to damage such as delamination, fiber breaking/pullout, matrix cracking, and hygrothermal strain. To ensure human safety and load-bearing integrity, these structures must be inspected to detect and locate often invisible damage and faults before becoming catastrophic. Moreover, nearly all future structures will need some type of in-service inspection technique to increase their useful life and reduce maintenance and overall costs. Possible techniques for monitoring the health and indicating damage on composite structures include: c-scan, thermography, acoustic emissions using piezoceramic actuators or fiber-optic wires with gratings, laser ultrasound, shearography, holography, x-ray, and others. These techniques have limitations in detecting damage that is beneath the surface of the structure, far away from a sensor location, or during operation of the vehicle. The objective of this project is to develop a more global method for damage detection that is based on structural dynamics principles, and can inspect for damage when the structure is subjected to vibratory loads to expose faults that may not be evident by static inspection. A Transmittance Function Monitoring (TFM) method is being developed in this project for ground-based inspection and operational health monitoring of large composite structures as a RLV. A comparison of the features of existing health monitoring approaches and the proposed TFM method is given.

Quantifying forest vertical structure to determine bird habitat quality in the Greenbelt Corridor, Denton, TX

NASA Astrophysics Data System (ADS)

Matsubayashi, Shiho

This study presents the integration of light detection and range (LiDAR) and hyperspectral remote sensing to create a three-dimensional bird habitat map in the Greenbelt Corridor of the Elm Fork of the Trinity River. This map permits to examine the relationship between forest stand structure, landscape heterogeneity, and bird community composition. A biannual bird census was conducted at this site during the breeding seasons of 2009 and 2010. Census data combined with the three-dimensional map suggest that local breeding bird abundance, community structure, and spatial distribution patterns are highly influenced by vertical heterogeneity of vegetation surface. For local breeding birds, vertical heterogeneity of canopy surface within stands, connectivity to adjacent forest patches, largest forest patch index, and habitat (vegetation) types proved to be the most influential factors to determine bird community assemblages. Results also highlight the critical role of secondary forests to increase functional connectivity of forest patches. Overall, three-dimensional habitat descriptions derived from integrated LiDAR and hyperspectral data serve as a powerful bird conservation tool that shows how the distribution of bird species relates to forest composition and structure at various scales.

Design, testing, and damage tolerance study of bonded stiffened composite wing cover panels

NASA Technical Reports Server (NTRS)

Madan, Ram C.; Sutton, Jason O.

1988-01-01

Results are presented from the application of damage tolerance criteria for composite panels to multistringer composite wing cover panels developed under NASA's Composite Transport Wing Technology Development contract. This conceptual wing design integrated aeroelastic stiffness constraints with an enhanced damage tolerance material system, in order to yield optimized producibility and structural performance. Damage tolerance was demonstrated in a test program using full-sized cover panel subcomponents; panel skins were impacted at midbay between stiffeners, directly over a stiffener, and over the stiffener flange edge. None of the impacts produced visible damage. NASTRAN analyses were performed to simulate NDI-detected invisible damage.

Micro-tube biotemplate synthesis of Fe3O4/C composite as anode material for lithium-ion batteries

NASA Astrophysics Data System (ADS)

Du, Jun; Ding, Yu; Guo, Liangui; Wang, Li; Fu, Zhengbing; Qin, Caiqin; Wang, Feng; Tao, Xinyong

2017-12-01

Kapok fibres were used as micro-tube biotemplate and bio-carbon source to synthesise Fe3O4/C composites, which were then utilised as anode materials. Fe3O4 nanoparticles were grown uniformly onto the external surface and internal channel of kapok carbon fibres. The flexibility, high specific surface area and electronic conduction of kapok fibres can buffer the volume expansion as well as inhibit the aggregation of Fe3O4 nanoparticles. Thus, the electrical integrity and structural of the Fe3O4/C composites electrode during lithiation/delithiation processes. The Fe3O4/C composites electrode delivers a high reversible capacity of 596 mA h g-1 after 100 cycles and an ultra-high coulombic efficiency approaching 100%. The high electrochemical performance of the Fe3O4/C composites can be caused by the synergistic effect of the Fe3O4 nanoparticles and the structure of kapok carbon fibres.

Conformal and embedded IDT microsensors for health monitoring of structures

NASA Astrophysics Data System (ADS)

Varadan, Vijay K.; Varadan, Vasundara V.

2000-06-01

MEMS are currently being applied to the structural health monitoring of critical aircraft components and composites. The approach integrates acoustic emission, strain gauges, MEMS accelerometers and vibration monitoring aircraft components with a known history of catastrophic failure due to fracture. Recently a combination of the need for safety in the air and the desire to control costs is encouraging the use of in-flight monitoring of aircraft components and systems using light-weight, wireless and cost effective microsensors and MEMS. An in-situ aircraft structural health monitoring system, with sensors embedded in the composite structure or surface-mounted on the structure, would permit the timely detection of damage in aircraft. Micromachining offers the potential for fabricating a range of microsensor and MEMS for structural applications including load, vibration and acoustics characterization and monitoring. Such microsensors are extremely small; they can be embedded into structural materials, can be mass-produced and are therefore potentially cheap. The smart sensors are being developed using the standard microelectronics and micromachining in conjunction with novel Penn State wireless communication systems suitable for condition monitoring of aircraft structures in-flight. The main application areas of this investigation include continuos monitoring of a) structural integrity of aging aircraft, b) fatigue cracking, c) corrosion, d) deflection and strain of aircraft structures, wings, and rotorblades, e) impact damage, f) delamination and g) location and propagation of cracks. In this paper we give an overview of wireless programmable microsensors and MEMS and their associated driving electronics for such applications.

Finite-Element Analysis of Crack Arrest Properties of Fiber Reinforced Composites Application in Semi-Elliptical Cracked Pipelines

NASA Astrophysics Data System (ADS)

Wang, Linyuan; Song, Shulei; Deng, Hongbo; Zhong, Kai

2018-04-01

In nowadays, repair method using fiber reinforced composites as the mainstream pipe repair technology, it can provide security for X100 high-grade steel energy long-distance pipelines in engineering. In this paper, analysis of cracked X100 high-grade steel pipe was conducted, simulation analysis was made on structure of pipes and crack arresters (CAs) to obtain the J-integral value in virtue of ANSYS Workbench finite element software and evaluation on crack arrest effects was done through measured elastic-plastic fracture mechanics parameter J-integral and the crack arrest coefficient K, in a bid to summarize effect laws of composite CAs and size of pipes and cracks for repairing CAs. The results indicate that the K value is correlated with laying angle λ, laying length L2/D1, laying thickness T1/T2of CAs, crack depth c/T1 and crack length a/c, and calculate recommended parameters for repairing fiber reinforced composite CAs in terms of two different crack forms.

Passive damping of composite blades using embedded piezoelectric modules or shape memory alloy wires: a comparative study

NASA Astrophysics Data System (ADS)

Bachmann, F.; de Oliveira, R.; Sigg, A.; Schnyder, V.; Delpero, T.; Jaehne, R.; Bergamini, A.; Michaud, V.; Ermanni, P.

2012-07-01

Emission reduction from civil aviation has been intensively addressed in the scientific community in recent years. The combined use of novel aircraft engine architectures such as open rotor engines and lightweight materials offer the potential for fuel savings, which could contribute significantly in reaching gas emissions targets, but suffer from vibration and noise issues. We investigated the potential improvement of mechanical damping of open rotor composite fan blades by comparing two integrated passive damping systems: shape memory alloy wires and piezoelectric shunt circuits. Passive damping concepts were first validated on carbon fibre reinforced epoxy composite plates and then implemented in a 1:5 model of an open rotor blade manufactured by resin transfer moulding (RTM). A two-step process was proposed for the structural integration of the damping devices into a full composite fan blade. Forced vibration measurements of the plates and blade prototypes quantified the efficiency of both approaches, and their related weight penalty.

Impact of land use on the biodiversity integrity of the moist sub-biome of the grassland biome, South Africa.

PubMed

O'Connor, T G; Kuyler, P

2009-01-01

South Africa's moist grassland harbours globally significant biodiversity, supplies essential ecosystem services, supports crop and livestock agriculture, forestry and settlement, yet is poorly conserved. Ongoing transformation and limited opportunity for expanding the protected area network require instead that biodiversity conservation is 'mainstreamed' within other land uses. This exercise sought to identify the relative compatibility of 10 land uses (conservation, livestock or game ranching, tourism/recreation, rural settlement, dryland cropping, irrigated cropping, dairy farming, plantation forestry, and urban settlement) with maintaining biodiversity integrity. This was assessed using 46 indicators for biodiversity integrity that covered landscape composition, structure, and functioning. Data was integrated into a single measure per land use through application of the analytic hierarchy process, with supporting information gained from interviews with experts. The rank order of importance amongst indicators was landscape structure, functioning and composition. Consistent differences among land uses for all three categories revealed two clear groupings. Conservation, livestock or game ranching had the lowest impact and retained substantial natural asset, while that for tourism/recreation was intermediate. All other land uses had a severe impact. Impact on biodiversity integrity depended mainly on the extent of transformation and fragmentation, which accounted for the greatest impact on habitats and species, and impairment of landscape functioning. It is suggested that a strategic intervention for maintaining biodiversity integrity of moist grassland is to support livestock or game ranching and limit ongoing urban sprawl.

Beam Scanning Antenna with Wideband Broadside Radiation Based on Multilayered Substrate Integrated Waveguide Composite Right/Left-Handed Structure

NASA Astrophysics Data System (ADS)

Zhang, Qin; Wu, Guo-cheng; Wang, Guang-ming; Liang, Jian-gang; Gao, Xiang-jun

2017-01-01

In this paper, a novel multilayered substrate integrated waveguide (SIW) composite right/left-handed (CRLH) structure is proposed to design beam scanning antenna for wideband broadside radiation. The unit cell of the SIW-CRLH structure is formed by spiral interdigital fingers etched on the upper ground of SIW, and a parasitic patch beneath the slot, has a continuous change of phase constant from negative to positive value within its passband. The proposed beam scanning antenna, which consists of consists of 15 identical elementary cells of the SIW-CRLH, is simulated, fabricated and measured. According to the measured results, the proposed antenna not only realizes a continuous main beam scanning from backward -78° to forward +80° within the operating frequency range from 8.25 to 12.2 GHz, but also obtains the measured broadside gain of 11.5 dB with variation of 1.0 dB over the frequency range of 8.8-9.25 GHz (4.99 %). Besides, compared with the same works in the references, this one has the most wonderful performance.

Structural Health Monitoring of a Composite Panel Based on PZT Sensors and a Transfer Impedance Framework.

PubMed

Dziendzikowski, Michal; Niedbala, Patryk; Kurnyta, Artur; Kowalczyk, Kamil; Dragan, Krzysztof

2018-05-11

One of the ideas for development of Structural Health Monitoring (SHM) systems is based on excitation of elastic waves by a network of PZT piezoelectric transducers integrated with the structure. In the paper, a variant of the so-called Transfer Impedance (TI) approach to SHM is followed. Signal characteristics, called the Damage Indices (DIs), were proposed for data presentation and analysis. The idea underlying the definition of DIs was to maintain most of the information carried by the voltage induced on PZT sensors by elastic waves. In particular, the DIs proposed in the paper should be sensitive to all types of damage which can influence the amplitude or the phase of the voltage induced on the sensor. Properties of the proposed DIs were investigated experimentally using a GFRP composite panel equipped with PZT networks attached to its surface and embedded into its internal structure. Repeatability and stability of DI indications under controlled conditions were verified in tests. Also, some performance indicators for surface-attached and structure-embedded sensors were obtained. The DIs' behavior was dependent mostly on the presence of a simulated damage in the structure. Anisotropy of mechanical properties of the specimen, geometrical properties of PZT network as well as, to some extent, the technology of sensor integration with the structure were irrelevant for damage indication. This property enables the method to be used for damage detection and classification.

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.

Advanced manufacturing development of a composite empennage component for L-1011 aircraft. Phase 2: Design and analysis

NASA Technical Reports Server (NTRS)

Jackson, A. C.; Crocker, J. F.; Ekvall, J. C.; Eudaily, R. R.; Mosesian, B.; Vancleave, R. R.; Vanhamersveld, J.

1981-01-01

The composite fin design consists of two one-piece cocured covers, two one-piece cocured spars and eleven ribs. The lower ribs are truss ribs with graphite/epoxy caps and aluminum truss members. The upper three ribs are a sandwich design with graphite/epoxy face sheets and a syntactic epoxy core. The design achieves a 27% weight saving compared to the metal box. The fastener count has been reduced from over 40,000 to less than 7000. The structural integrity of the composite fin was verified by analysis and test. The static, fail-safe and flutter analyses were completed. An extensive test program has established the material behavior under a range of conditions and critical subcomponents were tested to verify the structural concepts.

An Investigation on the Use of a Laser Ablation Treatment on Metallic Surfaces and the Influence of Temperature on Fracture Toughness of Hybrid Co-Cured Metal-PMC Interfaces

NASA Technical Reports Server (NTRS)

Connell, John; Palmieri, Frank; Truong, Hieu; Ochoa, Ozden; Lagoudas, Dimitris

2015-01-01

Hybrid composite laminates that contain alternating layers of titanium alloys and carbon fabric reinforced polyimide matrix composites (PMC) are excellent candidates for light-weight, high-temperature structural materials for high-speed aerospace vehicles. The delamination resistance of the hybrid titanium-PMC interface is of crucial consideration for structural integrity during service. Here, we report the first investigations on the use of laser ablation in combination with sol-gel treatment technique on Ti/NiTi foil surfaces in co-cured hybrid polyimide matrix composite laminates. Mode-I and mode-II fracture toughness of the hybrid Ti/NiTi-PMC interface as a function of temperature were determined via experimental testing and finite element analysis.

Flutter analysis of composite box beams

NASA Technical Reports Server (NTRS)

Hodges, Dewey H.; Greenman, Matthew

1995-01-01

The dynamic aeroelastic instability of flutter is an important factor in the design of modern high-speed, flexible aircraft. The current trend is toward the creative use of composites to delay flutter. To obtain an optimum design, we need an accurate as well as efficient model. As a first step towards this goal, flutter analysis is carried out for an unswept composite box beam using a linear structural model and Theodorsen's unsteady aerodynamic theory. Structurally, the wing was modeled as a thin-walled box-beam of rectangular cross section. Theodorsen's theory was used to get 2-D unsteady aerodynamic forces, which were integrated over the span. A free-vibration analysis is carried out. These fundamental modes are used to get the flutter solution using the V-g method. Future work is intended to build on this foundation.

A Micro-Computed Tomography Technique to Study the Quality of Fibre Optics Embedded in Composite Materials

PubMed Central

Chiesura, Gabriele; Luyckx, Geert; Voet, Eli; Lammens, Nicolas; Van Paepegem, Wim; Degrieck, Joris; Dierick, Manuel; Van Hoorebeke, Luc; Vanderniepen, Pieter; Sulejmani, Sanne; Sonnenfeld, Camille; Geernaert, Thomas; Berghmans, Francis

2015-01-01

Quality of embedment of optical fibre sensors in carbon fibre-reinforced polymers plays an important role in the resultant properties of the composite, as well as for the correct monitoring of the structure. Therefore, availability of a tool able to check the optical fibre sensor-composite interaction becomes essential. High-resolution 3D X-ray Micro-Computed Tomography, or Micro-CT, is a relatively new non-destructive inspection technique which enables investigations of the internal structure of a sample without actually compromising its integrity. In this work the feasibility of inspecting the position, the orientation and, more generally, the quality of the embedment of an optical fibre sensor in a carbon fibre reinforced laminate at unit cell level have been proven. PMID:25961383

Energy storage in structural composites by introducing CNT fiber/polymer electrolyte interleaves.

PubMed

Senokos, Evgeny; Ou, Yunfu; Torres, Juan Jose; Sket, Federico; González, Carlos; Marcilla, Rebeca; Vilatela, Juan J

2018-02-21

This work presents a method to produce structural composites capable of energy storage. They are produced by integrating thin sandwich structures of CNT fiber veils and an ionic liquid-based polymer electrolyte between carbon fiber plies, followed by infusion and curing of an epoxy resin. The resulting structure behaves simultaneously as an electric double-layer capacitor and a structural composite, with flexural modulus of 60 GPa and flexural strength of 153 MPa, combined with 88 mF/g of specific capacitance and the highest power (30 W/kg) and energy (37.5 mWh/kg) densities reported so far for structural supercapacitors. In-situ electrochemical measurements during 4-point bending show that electrochemical performance is retained up to fracture, with minor changes in equivalent series resistance for interleaves under compressive stress. En route to improving interlaminar properties we produce grid-shaped interleaves that enable mechanical interconnection of plies by the stiff epoxy. Synchrotron 3D X-ray tomography analysis of the resulting hierarchical structure confirms the formation of interlaminar epoxy joints. The manuscript discusses encapsulation role of epoxy, demonstrated by charge-discharge measurements of composites immersed in water, a deleterious agent for ionic liquids. Finally, we show different architectures free of current collector and electrical insulators, in which both CNT fiber and CF act as active electrodes.

Application of golay complementary coded excitation schemes for non-destructive testing of sandwich structures

NASA Astrophysics Data System (ADS)

Arora, Vanita; Mulaveesala, Ravibabu

2017-06-01

In recent years, InfraRed Thermography (IRT) has become a widely accepted non-destructive testing technique to evaluate the structural integrity of composite sandwich structures due to its full-field, remote, fast and in-service inspection capabilities. This paper presents a novel infrared thermographic approach named as Golay complementary coded thermal wave imaging is presented to detect disbonds in a sandwich structure having face sheets from Glass/Carbon Fibre Reinforced (GFR/CFR) laminates and core of the wooden block.

Chemically Active, Porous 3D-Printed Thermoplastic Composites

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

Evans, Kent A.; Kennedy, Zachary C.; Arey, Bruce W.

Metal-organic frameworks (MOFs) exhibit exceptional properties and are widely investigated because of their structural and functional versatility relevant to catalysis, separations, and sensing applications. However, their commercial or large-scale application is often limited by their powder forms. To address this, we report the production of MOF-thermoplastic polymer composites accessed via a standard 3D printer. MOFs (Zeolitic imidazolate framework; ZIF-8) were successfully incorporated homogeneously into both poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) matrices, extruded into filaments, and utilized for on-demand access to 3D structures by fused-deposition modeling. Printed rigid PLA-MOF composites displayed good structural integrity, high surface area ((SA)avg =more » 531 m2 g-1) and hierarchical pore features. Flexible TPU-MOF composites (SAavg = 706 m2 g-1) were achieved by employing a sacrificial fluoropolymer readily removed post-printing. Critically, embedded particles in the plastic matrices retain their ability to participate in chemical interactions characteristic of the parent MOF. The fabrication strategies can be extended to other MOFs and illustrate the potential of 3D printing to create unique porous and high surface area chemically-active structures.« less

Evaluation of a new composite prosthesis for the repair of abdominal wall defects.

PubMed

Losi, Paola; Munaò, Antonella; Spiller, Dario; Briganti, Enrica; Martinelli, Ilaria; Scoccianti, Marco; Soldani, Giorgio

2007-10-01

The degree of integration of biomaterials used in the repair of abdominal wall defects seems to depend upon the structure of the prosthesis. The present investigation evaluates the behaviour in terms of adhesion formation and integration of a new composite prosthesis that could be employed in this clinical application. Full-thickness abdominal wall defects (7 x 5 cm) were created in 16 anaesthetized New Zealand white rabbits and the prosthesis were placed in direct contact with the visceral peritoneum during the experiment. The defects were repaired with a composite prosthesis or pure polypropylene mesh to establish two study groups (n = 8 each). The composite device was constituted by a polypropylene mesh physically attached to a poly(ether)urethane-polydimethylsiloxane laminar sheet. Animals were sacrificed 7, 14, 21 and 30 days after implant and prosthesis/surrounding tissue specimens subjected to light and electron microscopy. Firm adhesions were detected in the polypropylene implants, while they were not present in the composite implants. The excellent behaviour of the composite prosthesis shown in this study warrants further investigation on its use for the repair of abdominal wall defects when a prosthetic device needs to be placed in contact with the intestinal loops.

Bioinspired Hierarchical Nanofibrous Silver-Nanoparticle/Anatase-Rutile-Titania Composite as an Anode Material for Lithium-Ion Batteries.

PubMed

Luo, Yan; Li, Jiao; Huang, Jianguo

2016-11-29

A new bioinspired hierarchical nanofibrous silver-nanoparticle/anatase-rutile-titania (Ag-NP/A-R-titania) composite was fabricated by employing a natural cellulose substance (e.g., commercial laboratory cellulose filter paper) as the structural scaffold template, which was composed of anatase-phase titania (A-titania) nanotubes with rutile-phase titania (R-titania) nanoneedles grown on the surfaces and further silver nanoparticles (AgNPs) immobilized thereon. As it was employed as an anode material for lithium-ion batteries (LIBs), high reversible capacity, enhanced rate performance, and excellent cycling stability were achieved as compared with those of the corresponding cellulose-substance-derived nanotubular A-titania, R-titania, heterogeneous anatase/rutile titania (A-R-titania) composite, and commercial P25 powder. This benefited from its unique porous cross-linked three-dimensional structure inherited from the initial cellulose substance scaffold, which enhances the sufficient electrode/electrolyte contact, relieves the severe volume change upon cycling, and improves the amount of lithium-ion storage; moreover, the high loading content of the silver component in the composite improves the electrical conductivity of the electrode. The structural integrity of the composite was maintained upon long-term charge/discharge cycling, indicating its significant stability.

UMAT Implementation of Coupled, Multilevel, Structural Deformation and Damage Analysis of General Hereditary Materials

NASA Technical Reports Server (NTRS)

Arnold, S. M.; Saleeb, A. F.; Wilt, T. E.; Trowbridge, D.

2000-01-01

Extensive research efforts have been made over the years on the phenomenological representations of constitutive material behavior in the inelastic analysis and life assessment of structures composed of advanced monolithic and composite (CMC, MMC, and PMC) materials. Recently, emphasis has been placed on concurrently addressing three important and related areas of constitutive and degradation modeling; i.e. (i) mathematical formulation, (ii) algorithmic developments for the updating (integrating) of external (e.g. stress) and internal state variable, as well as (iii) parameter estimation for the characterization of the specific model. This concurrent perspective has resulted in; i) the formulation of a fully-associative viscoelastoplastic model (GVIPS), (ii) development of an efficient implicit integration and it's associative, symmetric, consistent tangent stiffness matrix algorithm for integration of the underlying rate flow/evolutionary equations, and iii) a robust, stand-alone, Constitutive Material Parameter Estimator (COMPARE) for automatically characterizing the various time-dependent, nonlinear, material models. Furthermore, to provide a robust multi-scale framework for the deformation and life analysis of structures composed of composite materials, NASA Glenn has aggressively pursued the development of a sufficiently general, accurate, and efficient micromechanics approach known as the generalized method of cells (GMC). This work has resulted in the development of MAC/GMC, a stand-alone micromechanics analysis tool that can easily and accurately design/analyze multiphase (composite) materials subjected to complex histories. MAC/GMC admits generalized, physically based, deformation and damage models for each constituent and provides "closed-form" expressions for the macroscopic composite response in terms of the properties, size, shape, distribution, and response of the individual constituents or phases that comprise the material. Consequently, MAC/GMC can be incorporated directly into a structural finite element code like ABAQUS for cost-effective, micromechanics based, large-scale component design and analysis. Our primary objective here is to report on these recent works conducted over the past decade, in the context of their incorporation into ABAQUS through the various user subroutines. Representative results will be shown to demonstrate the features of the developed schemes.

Multi-Scale Modeling of an Integrated 3D Braided Composite with Applications to Helicopter Arm

NASA Astrophysics Data System (ADS)

Zhang, Diantang; Chen, Li; Sun, Ying; Zhang, Yifan; Qian, Kun

2017-10-01

A study is conducted with the aim of developing multi-scale analytical method for designing the composite helicopter arm with three-dimensional (3D) five-directional braided structure. Based on the analysis of 3D braided microstructure, the multi-scale finite element modeling is developed. Finite element analysis on the load capacity of 3D five-directional braided composites helicopter arm is carried out using the software ABAQUS/Standard. The influences of the braiding angle and loading condition on the stress and strain distribution of the helicopter arm are simulated. The results show that the proposed multi-scale method is capable of accurately predicting the mechanical properties of 3D braided composites, validated by the comparison the stress-strain curves of meso-scale RVCs. Furthermore, it is found that the braiding angle is an important factor affecting the mechanical properties of 3D five-directional braided composite helicopter arm. Based on the optimized structure parameters, the nearly net-shaped composite helicopter arm is fabricated using a novel resin transfer mould (RTM) process.

Quiet Clean Short-haul Experimental Engine (QCSEE) composite fan frame design report

NASA Technical Reports Server (NTRS)

Mitchell, S. C.

1978-01-01

An advanced composite frame which is flight-weight and integrates the functions of several structures was developed for the over the wing (OTW) engine and for the under the wing (UTW) engine. The composite material system selected as the basic material for the frame is Type AS graphite fiber in a Hercules 3501 epoxy resin matrix. The frame was analyzed using a finite element digital computer program. This program was used in an iterative fashion to arrive at practical thicknesses and ply orientations to achieve a final design that met all strength and stiffness requirements for critical conditions. Using this information, the detail design of each of the individual parts of the frame was completed and released. On the basis of these designs, the required tooling was designed to fabricate the various component parts of the frame. To verify the structural integrity of the critical joint areas, a full-scale test was conducted on the frame before engine testing. The testing of the frame established critical spring constants and subjected the frame to three critical load cases. The successful static load test was followed by 153 and 58 hours respectively of successful running on the UTW and OTW engines.

Tailoring the structure of aligned carbon nanotube bundle by reactive polymer for strengthening its surface interaction with thermosets and the excellent properties of the hybrid thermosets

NASA Astrophysics Data System (ADS)

Guan, Qingbao; Yuan, Li; Zhang, Yi; Gu, Aijuan; Liang, Guozheng

2018-05-01

Aligned carbon nanotube bundles (ACNTB) with multi-level hierarchical structures were tailored by reactive polymer vinyl-terminated polyphenylene ether (PPE) for the excellent integrated property of bismaleimide-triazine (BT) resin. The PPE-tailored ACNTB (ACNTB@PPE) has increased strength for the penetration of PPE into porous ACNTB strengthening the interaction between each CNT. The strong interaction at the interface of ACNTB@PPE and BT matrix can be created owing to the reaction of the vinyl group in PPE on the surface of ACNTB and maleimide group in BT. BT with 2% ACNTB@PPE composite shows the optimal flexural strength, fracture toughness and tensile strength, which are 88%, 115% and 77% higher than those of BT, respectively. The introduction of ACNTB@PPE slightly enhances the thermal property of BT. ACNTB@PPE can significantly improve the flame retardancy of BT composites. As compared to individual ACNTB, ACNTB@PPE effectively improves the integrated property of BT composites mainly due to the chemical interaction at the interface of ACNTB@PPE and BT matrix and the increased interaction between each CNT.

Detection of internal cracks in rubber composite structures using an impact acoustic modality

NASA Astrophysics Data System (ADS)

Shen, Q.; Kurfess, T. R.; Omar, M.; Gramling, F.

2014-01-01

The objective of this study is to investigate the use of impact acoustic signals to non-intrusively inspect rubber composite structures for the presence of internal cracks, such as those found in an automobile tyre. Theoretical contact dynamic models for both integral and defective rubber structures are developed based on Hertz's impact model, further modified for rubber composite materials. The model generates the prediction of major impact dynamic quantities, namely the maximum impact force, impact duration and contact deformation; such parameters are also theoretically proven to be correlated with the presence of internal cracks. The tyre structures are simplified into cubic rubber blocks, to mitigate complexity for analytical modelling. Both impact force and impact sound signals are measured experimentally, and extraction of useful features from both signals for defect identification is achieved. The impact force produces two direct measurements of theoretical impact dynamic quantities. A good correlation between these experimental discriminators and the theoretical dynamic quantities provide validation for the contact dynamics models. Defect discriminators extracted from the impact sound are dependent on both time- and frequency-domain analyses. All the discriminators are closely connected with the theoretical dynamic quantities and experimentally verified as good indicators of internal cracks in rubber composite structures.

Constructing Repairable Meta-Structures of Ultra-Broad-Band Electromagnetic Absorption from Three-Dimensional Printed Patterned Shells.

PubMed

Song, Wei-Li; Zhou, Zhili; Wang, Li-Chen; Cheng, Xiao-Dong; Chen, Mingji; He, Rujie; Chen, Haosen; Yang, Yazheng; Fang, Daining

2017-12-13

Ultra-broad-band electromagnetic absorption materials and structures are increasingly attractive for their critical role in competing with the advanced broad-band electromagnetic detection systems. Mechanically soft and weak wax-based materials composites are known to be insufficient to serve in practical electromagnetic absorption applications. To break through such barriers, here we developed an innovative strategy to enable the wax-based composites to be robust and repairable meta-structures by employing a three-dimensional (3D) printed polymeric patterned shell. Because of the integrated merits from both the dielectric loss wax-based composites and mechanically robust 3D printed shells, the as-fabricated meta-structures enable bear mechanical collision and compression, coupled with ultra-broad-band absorption (7-40 and 75-110 GHz, reflection loss  smaller than -10 dB) approaching state-of-the-art electromagnetic absorption materials. With the assistance of experiment and simulation methods, the design advantages and mechanism of employing such 3D printed shells for substantially promoting the electromagnetic absorption performance have been demonstrated. Therefore, such universal strategy that could be widely extended to other categories of wax-based composites highlights a smart stage on which high-performance practical multifunction meta-structures with ultra-broad-band electromagnetic absorption could be envisaged.

Unitized Stiffened Composite Textile Panels: Manufacturing, Characterization, Experiments, and Analysis

NASA Astrophysics Data System (ADS)

Kosztowny, Cyrus Joseph Robert

Use of carbon fiber textiles in complex manufacturing methods creates new implementations of structural components by increasing performance, lowering manufacturing costs, and making composites overall more attractive across industry. Advantages of textile composites include high area output, ease of handling during the manufacturing process, lower production costs per material used resulting from automation, and provide post-manufacturing assembly mainstreaming because significantly more complex geometries such as stiffened shell structures can be manufactured with fewer pieces. One significant challenge with using stiffened composite structures is stiffener separation under compression. Axial compression loading conditions have frequently observed catastrophic structural failure due to stiffeners separating from the shell skin. Characterizing stiffener separation behavior is often costly computationally and experimentally. The objectives of this research are to demonstrate unitized stiffened textile composite panels can be manufactured to produce quality test specimens, that existing characterization techniques applied to state-of-the-art high-performance composites provide valuable information in modeling such structures, that the unitized structure concept successfully removes stiffener separation as a primary structural failure mode, and that modeling textile material failure modes are sufficient to accurately capture postbuckling and final failure responses of the stiffened structures. The stiffened panels in this study have taken the integrally stiffened concept to an extent such that the stiffeners and skin are manufactured at the same time, as one single piece, and from the same composite textile layers. Stiffener separation is shown to be removed as a primary structural failure mode for unitized stiffened composite textile panels loaded under axial compression well into the postbuckling regime. Instead of stiffener separation, a material damaging and failure model effectively captures local post-peak material response via incorporating a mesoscale model using a multiscaling framework with a smeared crack element-based failure model in the macroscale stiffened panel. Material damage behavior is characterized by simple experimental tests and incorporated into the post-peak stiffness degradation law in the smeared crack implementation. Computational modeling results are in overall excellent agreement compared to the experimental responses.

Simulated Data for High Temperature Composite Design

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Abumeri, Galib H.

2006-01-01

The paper describes an effective formal method that can be used to simulate design properties for composites that is inclusive of all the effects that influence those properties. This effective simulation method is integrated computer codes that include composite micromechanics, composite macromechanics, laminate theory, structural analysis, and multi-factor interaction model. Demonstration of the method includes sample examples for static, thermal, and fracture reliability for a unidirectional metal matrix composite as well as rupture strength and fatigue strength for a high temperature super alloy. Typical results obtained for a unidirectional composite show that the thermal properties are more sensitive to internal local damage, the longitudinal properties degrade slowly with temperature, the transverse and shear properties degrade rapidly with temperature as do rupture strength and fatigue strength for super alloys.

Study of advanced composite structural design concepts for an arrow wing supersonic cruise configuration

NASA Technical Reports Server (NTRS)

Turner, M. J.; Grande, D. L.

1978-01-01

Based on estimated graphite and boron fiber properties, allowable stresses and strains were established for advanced composite materials. Stiffened panel and conventional sandwich panel concepts were designed and analyzed, using graphite/polyimide and boron/polyimide materials. The conventional sandwich panel was elected as the structural concept for the modified wing structure. Upper and lower surface panels of the arrow wing structure were then redesigned, using high strength graphite/polyimide sandwich panels, retaining the titanium spars and ribs from the prior study. The ATLAS integrated analysis and design system was used for stress analysis and automated resizing of surface panels. Flutter analysis of the hybrid structure showed a significant decrease in flutter speed relative to the titanium wing design. The flutter speed was increased to that of the titanium design by selective increase in laminate thickness and by using graphite fibers with properties intermediate between high strength and high modulus values.

A finite element-boundary integral method for scattering and radiation by two- and three-dimensional structures

NASA Technical Reports Server (NTRS)

Jin, Jian-Ming; Volakis, John L.; Collins, Jeffery D.

1991-01-01

A review of a hybrid finite element-boundary integral formulation for scattering and radiation by two- and three-dimensional composite structures is presented. In contrast to other hybrid techniques involving the finite element method, the proposed one is in principle exact and can be implemented using a low O(N) storage. This is of particular importance for large scale applications and is a characteristic of the boundary chosen to terminate the finite element mesh, usually as close to the structure as possible. A certain class of these boundaries lead to convolutional boundary integrals which can be evaluated via the fast Fourier transform (FFT) without a need to generate a matrix; thus, retaining the O(N) storage requirement. The paper begins with a general description of the method. A number of two- and three-dimensional applications are then given, including numerical computations which demonstrate the method's accuracy, efficiency, and capability.

Vertically Integrated MEMS SOI Composite Porous Silicon-Crystalline Silicon Cantilever-Array Sensors: Concept for Continuous Sensing of Explosives and Warfare Agents

NASA Astrophysics Data System (ADS)

Stolyarova, Sara; Shemesh, Ariel; Aharon, Oren; Cohen, Omer; Gal, Lior; Eichen, Yoav; Nemirovsky, Yael

This study focuses on arrays of cantilevers made of crystalline silicon (c-Si), using SOI wafers as the starting material and using bulk micromachining. The arrays are subsequently transformed into composite porous silicon-crystalline silicon cantilevers, using a unique vapor phase process tailored for providing a thin surface layer of porous silicon on one side only. This results in asymmetric cantilever arrays, with one side providing nano-structured porous large surface, which can be further coated with polymers, thus providing additional sensing capabilities and enhanced sensing. The c-Si cantilevers are vertically integrated with a bottom silicon die with electrodes allowing electrostatic actuation. Flip Chip bonding is used for the vertical integration. The readout is provided by a sensitive Capacitance to Digital Converter. The fabrication, processing and characterization results are reported. The reported study is aimed towards achieving miniature cantilever chips with integrated readout for sensing explosives and chemical warfare agents in the field.

A new SMART sensing system for aerospace structures

NASA Astrophysics Data System (ADS)

Zhang, David C.; Yu, Pin; Beard, Shawn; Qing, Peter; Kumar, Amrita; Chang, Fu-Kuo

2007-04-01

It is essential to ensure the safety and reliability of in-service structures such as unmanned vehicles by detecting structural cracking, corrosion, delamination, material degradation and other types of damage in time. Utilization of an integrated sensor network system can enable automatic inspection of such damages ultimately. Using a built-in network of actuators and sensors, Acellent is providing tools for advanced structural diagnostics. Acellent's integrated structural health monitoring system consists of an actuator/sensor network, supporting signal generation and data acquisition hardware, and data processing, visualization and analysis software. This paper describes the various features of Acellent's latest SMART sensing system. The new system is USB-based and is ultra-portable using the state-of-the-art technology, while delivering many functions such as system self-diagnosis, sensor diagnosis, through-transmission mode and pulse-echo mode of operation and temperature measurement. Performance of the new system was evaluated for assessment of damage in composite structures.

Material Characterization for Composite Materials in Load Bearing Wave Guides

DTIC Science & Technology

2012-03-01

ISIS Integrated Sensor Is Structure MUSTRAP Multifunctional Structural Aperture MWCNT Multi-walled Carbon Nanotube SWCNT Single-walled Carbon...CNTs go through a specific process to coat them with nickel. The process includes conditioning the CNTs in different solutions and adding...a single-walled carbon nanotube (SWCNT), a multi-walled carbon nanotube ( MWCNT ), or a graphene nanoribbon (GNR). A SWCNT is a hollow cylindrical

Carbon Nanotube-Reinforced Aluminum Matrix Composites Produced by High-Energy Ball Milling

NASA Astrophysics Data System (ADS)

Travessa, Dilermando N.; da Rocha, Geovana V. B.; Cardoso, Kátia R.; Lieblich, Marcela

2017-05-01

Although multiwall carbon nanotubes (MWCNT) are promising materials to strengthen lightweight aluminum matrix composites, their dispersion into the metallic matrix is challenge. In the present work, MWCNT were dispersed into age-hardenable AA6061 aluminum alloy by high-energy ball milling and the blend was subsequently hot-extruded. The composite bars obtained were heat-treated by solution heat treatment at 520 °C and artificially aged at 177 °C for 8 h, in order to reach the T6 temper. Special attention was given to the integrity of the MWCNT along the entire composite production. The microstructure of the obtained bars was evaluated by optical and scanning electron microscopy, and the mechanical properties were evaluated by Vickers microhardness tests. Raman spectroscopy, x-ray diffraction and transmission electron microscopy were employed to evaluate the structural integrity of MWCNT. It was found that milling time is critical to reach a proper dispersion of the reinforcing phase. The composite hardness increased up to 67% with the dispersion of 2% in weight of MWCNT, when comparing with un-reinforced bars produced by similar route. However, age hardening was not observed in composite bars after heat treatment. It was also found that MWCNT continuously degraded along the process, being partially converted into Al4C3 in the final composite.

Novel Composites for Wing and Fuselage Applications. Task 1; Novel Wing Design Concepts

NASA Technical Reports Server (NTRS)

Suarez, J. A.; Buttitta, C.; Flanagan, G.; DeSilva, T.; Egensteiner, W.; Bruno, J.; Mahon, J.; Rutkowski, C.; Collins, R.; Fidnarick, R.;

Full-Scale Test and Analysis Results of a PRSEUS Fuselage Panel to Assess Damage Containment Features

NASA Technical Reports Server (NTRS)

Bergan, Andrew; Bakuckas, John G., Jr.; Lovejoy, Andrew; Jegley, Dawn; Linton, Kim; Neal, Bert; Korkosz, Gregory; Awerbuch, Jonathan; Tan, Tein-Min

2012-01-01

Integrally stitched composite technology is an area that shows promise in enhancing the structural integrity of aircraft and aerospace structures. The most recent generation of this technology is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept. The goal of the PRSEUS concept relevant to this test is to provide damage containment capability for composite structures while reducing overall structural weight. The National Aeronautics and Space Administration (NASA), the Federal Aviation Administration (FAA), and The Boeing Company have partnered in an effort to assess the damage containment features of a full-scale curved PRSEUS panel using the FAA Full-Scale Aircraft Structural Test Evaluation and Research (FASTER) facility. A single PRSEUS test panel was subjected to axial tension, internal pressure, and combined axial tension and internal pressure loads. The test results showed excellent performance of the PRSEUS concept. No growth of Barely Visible Impact Damage (BVID) was observed after ultimate loads were applied. With a two-bay notch severing the central stringer, damage was contained within the two-bay region well above the required limit load conditions. Catastrophic failure was well above the ultimate load level. Information describing the test panel and procedure has been previously presented, so this paper focuses on the experimental procedure, test results, nondestructive inspection results, and preliminary test and analysis correlation.

Development of integrated damage detection system for international America's Cup class yacht structures using a fiber optic distributed sensor

NASA Astrophysics Data System (ADS)

Akiyoshi, Shimada; Naruse, Hiroshi; Uzawa, Kyoshi; Murayama, Hideaki; Kageyama, Kazuro

2000-06-01

We constructed a new health monitoring system to detect damage using a fiber optic distributed sensor, namely a Brillouin optical time domain reflectometer (BOTDR), and installed it in International America's Cup Class (IACC) yachts, the Japanese entry in America's Cup 2000. IACC yachts are designed to be as fast as possible, so it is essential that they are lightweight and encounter minimum water resistance. Advanced composite sandwich structures, made with carbon fiber reinforced plastic (CFRP) skins and a honeycomb core, are used to achieve the lightweight structure. Yacht structure designs push the strength of the materials to their limit and so it is important to detect highly stressed or damaged regions that might cause a catastrophic fracture. The BOTDR measures changes in the Brillouin frequency shift caused by distributed strain along one optical fiber. We undertook two experiments: a pulling test and a four point bending test on a composite beam. The former showed that no slippage occurred between the optical fiber glass and its coating. The latter confirmed that a debonding between the skin and the core of 300 mm length could be found with the BOTDR. Next we examined the effectiveness with which this system can assess the structural integrity of IACC yachts. The results show that our system has the potential for use as a damage detection system for smart structures.

Use of composite materials, health monitoring and self-healing concepts to refurbish our civil and military infrastructure.

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

Roach, Dennis Patrick; Delong, Waylon Anthony; White, Scott

An unavoidable by-product of a metallic structure's use is the appearance of crack, corrosion, erosion and other flaws. Economic barriers to the replacement of these structures have created an aging civil and military infrastructure and placed even greater demands on efficient and safe repair and inspection methods. As a result of Homeland Security issues and these aging infrastructure concerns, increased attention has been focused on the rapid repair and preemptive reinforcement of structures such as buildings and bridges. This Laboratory Directed Research and Development (LDRD) program established the viability of using bonded composite patches to repair metallic structures. High modulusmore » fiber-reinforced polymer (FRP) material may be used in lieu of mechanically fastened metallic patches or welds to reinforce or repair damaged structures. Their use produces a wide array of engineering and economic advantages. Current techniques for strengthening steel structures have several drawbacks including requiring heavy equipment for installation, poor fatigue performance, and the need for ongoing maintenance due to continued corrosion attack or crack growth. The use of bonded composite doublers has the potential to correct the difficulties associated with current repair techniques and the ability to be applied where there are currently no rehabilitation options. Applications include such diverse structures as: buildings, bridges, railroad cars, trucks and other heavy machinery, steel power and communication towers, pipelines, factories, mining equipment, ships, tanks and other military vehicles. This LDRD also proved the concept of a living infrastructure by developing custom sensors and self-healing chemistry and linking this technology with the application of advanced composite materials. Structural Health Monitoring (SHM) systems and mountable, miniature sensors were designed to continuously or periodically assess structural integrity. Such systems are able to detect incipient damage before catastrophic failure occurs. The ease of monitoring an entire network of distributed sensors means that structural health assessments can occur more often, allowing operators to be even more vigilant with respect to flaw onset. In addition, the realization of smart structures, through the use of in-situ sensors, allows condition-based maintenance to be substituted for conventional time-based maintenance practices. The sensitivity and reliability of a series of sensor systems was quantified in laboratory and real-world environments. Finally, self healing methods for composite materials were evolved--using resin modules that are released in response to the onset of delaminations--so that these components can provide a living infrastructure with minimal need for human intervention. This program consisted of four related research elements: (1) design, installation, and performance assessment of composite repairs, (2) in-situ sensors for real-time health monitoring, (3) self healing of in-service damage in a repair, and (4) numerical modeling. Deployment of FRP materials and bonded joints requires proper design, suitable surface preparation methods, and adequate surveillance to ensure structural integrity. By encompassing all 'cradle-to-grave' tasks --including design, analysis, installation, durability, flaw containment, and inspection--this program is designed to firmly establish the capabilities of composite doubler repairs and introduce technology to incorporate self-monitoring and self-healing (living structures) methodologies. A proof-of-concept repair was completed on a steel highway bridge in order to demonstrate the potential of composite doubler technology for critical infrastructure use.« less

Developments in Nano-Satellite Structural Subsystem Design at NASA-GSFC

NASA Technical Reports Server (NTRS)

Rossoni, Peter; Panetta, Peter V.

1999-01-01

The NASA-GSFC Nano-satellite Technology Development Program will enable flying constellations of tens to hundreds of nano-satellites for future NASA Space and Earth Science missions. Advanced technology components must be developed to make these future spacecraft compact, lightweight, low-power, low-cost, and survivable to a radiation environment over a two-year mission lifetime. This paper describes the efforts underway to develop lightweight, low cost, and multi-functional structures, serviceable designs, and robust mechanisms. As designs shrink, the integration of various subsystems becomes a vital necessity. This paper also addresses structurally integrated electrical power, attitude control, and thermal systems. These innovations bring associated fabrication, integration, and test challenges. Candidate structural materials and processes are examined and the merits of each are discussed. Design and fabrication processes include flat stock composite construction, cast aluminum-beryllium alloy, and an injection molded fiber-reinforced plastic. A viable constellation deployment scenario is described as well as a Phase-A Nano-satellite Pathfinder study.

Structural analysis of high-rpm composite propfan blades for a cruise missile wind tunnel model

NASA Technical Reports Server (NTRS)

Carek, David A.

1993-01-01

Analyses were performed on a high-speed composite blade set for the Department of Defense Propfan Missile Interactions Project. The final design iteration, which resulted in the CM2D-2 blade design, is described in this report. Mode shapes, integral order excitation, and stress margins were examined. In addition, geometric corrections were performed to compensate for blade deflection under operating conditions with respect to the aerodynamic design shape.

Metal-Matrix Composite Parts With Metal Inserts

NASA Technical Reports Server (NTRS)

Majkowski, T.; Kashalikar, U.

1995-01-01

Developmental fabrication process produces metal-matrix composite (MMC) parts with integral metal inserts. With inserts, MMC parts readily joined to similar parts by use of brazing, welding, or mechanical fasteners. Process conceived to make strong, lightweight components of structures erected in outer space. Also useful on Earth, in such automotive parts as rocker arms, cylinder liners, and pistons. Potential industrial applications include parts subjected to high stresses at high temperatures, as in power-generation, mining, and oil-drilling equipment.

Development and fabrication of an autoclave molded PES/Quartz sandwich radome

NASA Astrophysics Data System (ADS)

Stanton, Leonard E.; Levin, Stephen D.

1993-04-01

A cohesively bonded, thermoplastic composite sandwich radome for a leading edge supersonic aircraft has been built using autoclave processing with PES/Quartz prepreg and a PES coated honeycomb core. Processes were developed for solvent removal, thermoplastic laminate consolidation, surface etching to improve adhesion, honeycomb coating and forming, and ultrasound testing of bond integrity. Environmental testing was also conducted to verify the structural integrity of the radome for its intended application.

Innovative Design for Composite Spacecraft Structure Thanks to Automatic Fiber Placement Technology

NASA Astrophysics Data System (ADS)

Brindeau, Aymeric; Khalfi, Thomas

2014-06-01

The innovative design for composite spacecraft structure thanks to automatic fiber placement technology takes place in the frame of the development of a new launcher. A heavy loaded spacecraft carrying structure is developed in order to allow performance and big payload volumes.This kind of structure already exists on a current launcher, but performances are not compatible with the new requirements. Indeed, in spite of a sandwich design made of carbon and aluminium honeycomb, mass and stiffness requirements are not fulfilled.Consequently, for the new structure, an innovative design has been set-up. The materials are still sandwich made of carbon and aluminium honeycomb in order to obtain the best ratio mass / stiffness, but major evolutions have been implemented of the geometry of the structure in order to increase the performance of the product. These evolutions are allowed thanks to the use of the fiber placement technology, which allows manufacturing geometries that are not reachable with standard lay-up by hands. The main progress deals with the manufacturing of revolution sub-structures, in one shot, with double curvature areas. Moreover, beyond the technical performance of the new product and the gains in terms of manufacturing time and quality, the integration of sub-structures is extremely simplified compared to the existing process. As a result, the technology of fiber placement is the opportunity to imagine new designs which allows increasing the performances, to reduce manufacturing cycles, and to simplify integration operations.

An integrated approach to the optimum design of actively controlled composite wings

NASA Technical Reports Server (NTRS)

Livne, E.

1989-01-01

The importance of interactions among the various disciplines in airplane wing design has been recognized for quite some time. With the introduction of high gain, high authority control systems and the design of thin, flexible, lightweight composite wings, the integrated treatment of control systems, flight mechanics and dynamic aeroelasticity became a necessity. A research program is underway now aimed at extending structural synthesis concepts and methods to the integrated synthesis of lifting surfaces, spanning the disciplines of structures, aerodynamics and control for both analysis and design. Mathematical modeling techniques are carefully selected to be accurate enough for preliminary design purposes of the complicated, built-up lifting surfaces of real aircraft with their multiple design criteria and tight constraints. The presentation opens with some observations on the multidisciplinary nature of wing design. A brief review of some available state of the art practical wing optimization programs and a brief review of current research effort in the field serve to illuminate the motivation and support the direction taken in our research. The goals of this research effort are presented, followed by a description of the analysis and behavior sensitivity techniques used. The presentation concludes with a status report and some forecast of upcoming progress.

Ultrasonic analysis of Kevlar-epoxy filament wound structures

NASA Astrophysics Data System (ADS)

Brosey, W. D.

1985-07-01

Composite structures are often desirable for their strength and weight characteristics. Since composites are not as well characterized mechanically as metallic or ceramic structures, much work has been performed at the Oak Ridge Y-12 Plant to obtain that characterization and to develop methods of determining the mechanical properties of a composite nondestructively. Most of the work to date has been performed on nonenclosed structures. One notable exception has been the holographic evaluation of spherical Kevlar-epoxy composite pressure vessels. Several promising nondestructive evaluation techniques have been used to locate flaws and predict the integrity of the composite. Several of these include thermography, Moire interferometry, ultrasonic stress wave factor, ultrasonic C-scan image enhancement, radiography, and nuclear magnetic resonance. As a first step in this transfer and development of NDE techniques, known defects were placed within spherical Kevlar-epoxy, filament-wound test specimens to determine the extent to which they could be detected. These defects included Teflon shim-simulated delaminations, macrosphere-simulated voids, dry-band sets, variable tension, Kevlar 29 fiber instead of the higher strength Kevlar 40 fiber, and an alternate high-void-content winding pattern. Ultrasonic waveform analysis was performed in both the time and frequency domains to determine the detectability and locatability of structural flaws within the composite. Preparation has been made at Virginia Polytechnic Institute and State University and at the University of Delaware, to examine the specimens using various NDE techniques. This work is a compilation of interim project reports in partial fulfillment of the contracts between Virginia Polytechnic Institute and State University, the University of Delaware, and Y-12 Plant.

Simulation Based Optimization of Complex Monolithic Composite Structures Using Cellular Core Technology

NASA Astrophysics Data System (ADS)

Hickmott, Curtis W.

Cellular core tooling is a new technology which has the capability to manufacture complex integrated monolithic composite structures. This novel tooling method utilizes thermoplastic cellular cores as inner tooling. The semi-rigid nature of the cellular cores makes them convenient for lay-up, and under autoclave temperature and pressure they soften and expand providing uniform compaction on all surfaces including internal features such as ribs and spar tubes. This process has the capability of developing fully optimized aerospace structures by reducing or eliminating assembly using fasteners or bonded joints. The technology is studied in the context of evaluating its capabilities, advantages, and limitations in developing high quality structures. The complex nature of these parts has led to development of a model using the Finite Element Analysis (FEA) software Abaqus and the plug-in COMPRO Common Component Architecture (CCA) provided by Convergent Manufacturing Technologies. This model utilizes a "virtual autoclave" technique to simulate temperature profiles, resin flow paths, and ultimately deformation from residual stress. A model has been developed simulating the temperature profile during curing of composite parts made with the cellular core technology. While modeling of composites has been performed in the past, this project will look to take this existing knowledge and apply it to this new manufacturing method capable of building more complex parts and develop a model designed specifically for building large, complex components with a high degree of accuracy. The model development has been carried out in conjunction with experimental validation. A double box beam structure was chosen for analysis to determine the effects of the technology on internal ribs and joints. Double box beams were manufactured and sectioned into T-joints for characterization. Mechanical behavior of T-joints was performed using the T-joint pull-off test and compared to traditional tooling methods. Components made with the cellular core tooling method showed an improved strength at the joints. It is expected that this knowledge will help optimize the processing of complex, integrated structures and benefit applications in aerospace where lighter, structurally efficient components would be advantageous.

Hispanic Immigration to the Northeast In the 1970s.

ERIC Educational Resources Information Center

Gurak, Douglas T.; Kritz, Mary M.

1985-01-01

Discusses recent Hispanic immigration to the northeast U.S., particularly the New York City area. Presents data on country of origin, family composition and fertility, education levels, occupation, and income status. Examines patterns of structural integration, such as intermarriage and residential segregation. (SA)

A novel hybrid joining methodology for composite to steel joints

NASA Astrophysics Data System (ADS)

Sarh, Bastian

This research has established a novel approach for designing, analyzing, and fabricating load bearing structural connections between resin infused composite materials and components made of steel or other metals or alloys. A design philosophy is proposed wherein overlapping joint sections comprised of fiber reinforced plastics (FRP's) and steel members are connected via a combination of adhesive bonding and integrally placed composite pins. A film adhesive is utilized, placed into the dry stack prior to resin infusion and is cured after infusion through either local heat elements or by placing the structure into an oven. The novel manner in which the composite pins are introduced consists of perforating the steel member with holes and placing pre-formed composite pins through them, also prior to resin infusion of the composite section. In this manner joints are co-molded structures such that secondary processing is eliminated. It is shown that such joints blend the structural benefits of adhesive and mechanically connected joints, and that the fabrication process is feasible for low-cost, large-scale production as applicable to the shipbuilding industry. Analysis procedures used for designing such joints are presented consisting of an adhesive joint design theory and a pin placement theory. These analysis tools are used in the design of specimens, specific designs are fabricated, and these evaluated through structural tests. Structural tests include quasi-static loading and low cycle fatigue evaluation. This research has thereby invented a novel philosophy on joints, created the manufacturing technique for fabricating such joints, established simple to apply analysis procedures used in the design of such joints (consisting of both an adhesive and a pin placement analysis), and has validated the methodology through specimen fabrication and testing.

Structure and composition of the courtship phenotype in the bird of paradise Parotia lawesii (Aves: Paradisaeidae).

PubMed

Scholes, Edwin

2008-01-01

Ethology is rooted in the idea that behavior is composed of discrete units and sub-units that can be compared among taxa in a phylogenetic framework. This means that behavior, like morphology and genes, is inherently modular. Yet, the concept of modularity is not well integrated into how we envision the behavioral components of phenotype. Understanding ethological modularity, and its implications for animal phenotype organization and evolution, requires that we construct interpretive schemes that permit us to examine it. In this study, I describe the structure and composition of a complex part of the behavioral phenotype of Parotia lawesii Ramsay, 1885--a bird of paradise (Aves: Paradisaeidae) from the forests of eastern New Guinea. I use archived voucher video clips, photographic ethograms, and phenotype ontology diagrams to describe the modular units comprising courtship at various levels of integration. Results show P. lawesii to have 15 courtship and mating behaviors (11 males, 4 females) hierarchically arranged within a complex seven-level structure. At the finest level examined, male displays are comprised of 49 modular sub-units (elements) differentially employed to form more complex modular units (phases and versions) at higher-levels of integration. With its emphasis on hierarchical modularity, this study provides an important conceptual framework for understanding courtship-related phenotypic complexity and provides a solid basis for comparative study of the genus Parotia.

Limited access: gender, occupational composition, and flexible work scheduling.

PubMed

Glauber, Rebecca

2011-01-01

The current study draws on national data to explore differences in access to flexible work scheduling by the gender composition of women's and men's occupations. Results show that those who work in integrated occupations are more likely to have access to flexible scheduling. Women and men do not take jobs with lower pay in return for greater access to flexibility. Instead, jobs with higher pay offer greater flexibility. Integrated occupations tend to offer the greatest access to flexible scheduling because of their structural locations. Part-time work is negatively associated with men's access to flexible scheduling but positively associated with women's access. Women have greater flexibility when they work for large establishments, whereas men have greater flexibility when they work for small establishments.

Adsorption of heavy metal ions by hierarchically structured magnetite-carbonaceous spheres.

PubMed

Gong, Jingming; Wang, Xiaoqing; Shao, Xiulan; Yuan, Shuang; Yang, Chenlin; Hu, Xianluo

2012-11-15

Magnetically driven separation technology has received considerable attention in recent decade for its great potential application. In this work, hierarchically structured magnetite-carbonaceous microspheres (Fe(3)O(4)-C MSs) have been synthesized for the adsorption of heavy metal ions from aqueous solution. Each sphere contains numerous unique rattle-type structured magnetic particles, realizing the integration of rattle-type building unit into microspheres. The as-prepared composites with high BET surface area, hierarchical as well as mesoporous structures, exhibit an excellent adsorption capacity for heavy metal ions and a convenient separation procedure with the help of an external magnet. It was found that the maximum adsorption capacity of the composite toward Pb(2+) was ∼126mgg(-1), displaying a high efficiency for the removal of heavy metal ions. The Freundlich adsorption isotherm was applicable to describe the removal processes. Kinetics of the Pb(2+) removal was found to follow pseudo-second-order rate equation. The as-prepared composite of Fe(3)O(4)-C MSs as well as Pb(2+)-adsorbed composite were carefully examined by scanning electron microscopy (SEM), Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR), nitrogen sorption measurements, and X-ray photoelectron spectroscopy (XPS). Based on the characterization results, a possible mechanism of Pb(2+) removal with the composite of Fe(3)O(4)-C MSs was proposed. Copyright © 2012 Elsevier B.V. All rights reserved.

Environmental degradation of composites for marine structures: new materials and new applications

PubMed Central

2016-01-01

This paper describes the influence of seawater ageing on composites used in a range of marine structures, from boats to tidal turbines. Accounting for environmental degradation is an essential element in the multi-scale modelling of composite materials but it requires reliable test data input. The traditional approach to account for ageing effects, based on testing samples after immersion for different periods, is evolving towards coupled studies involving strong interactions between water diffusion and mechanical loading. These can provide a more realistic estimation of long-term behaviour but still require some form of acceleration if useful data, for 20 year lifetimes or more, are to be obtained in a reasonable time. In order to validate extrapolations from short to long times, it is essential to understand the degradation mechanisms, so both physico-chemical and mechanical test data are required. Examples of results from some current studies on more environmentally friendly materials including bio-sourced composites will be described first. Then a case study for renewable marine energy applications will be discussed. In both cases, studies were performed first on coupons at the material level, then during structural testing and analysis of large components, in order to evaluate their long-term behaviour. This article is part of the themed issue ‘Multiscale modelling of the structural integrity of composite materials’. PMID:27242304

Numerical Characterization of a Composite Bonded Wing-Box

NASA Technical Reports Server (NTRS)

Smeltzer, Stanley S., III; Lovejoy, Andrew E.; Satyanarayana, Arunkumar

2008-01-01

The development of composite wing structures has focused on the use of mechanical fasteners to join heavily-loaded areas, while bonded joints have been used only for select locations. The focus of this paper is the examination of the adhesive layer in a generic bonded wing box that represents a "fastenerless" or unitized structure in order to characterize the general behavior and failure mechanisms. A global/local approach was applied to study the response of the adhesive layer using a global shell model and a local shell/solid model. The wing box was analyzed under load to represent a high-g up-bending condition such that the strains in the composite sandwich face sheets are comparable to an expected design allowable. The global/local analysis indicates that at these wing load levels the strains in the adhesive layer are well within the adhesive's elastic region, such that yielding would not be expected in the adhesive layer. The global/local methodology appears to be a promising approach to evaluate the structural integrity of the adhesively bonded structures.

Cryotank Skin/Stringer Bondline Analysis

NASA Technical Reports Server (NTRS)

Nguyen, Bao

1999-01-01

The need for light weight structure for advanced launch systems have presented great challenges and led to the usage of composites materials in a variety of structural assemblies where joining of two or more components is imperative. Although joints can be mechanically bolted, adhesive bonding has always been a very desirable method for joining the composite components, particularly for the cryotank systems, to achieve maximum structural efficiency. This paper presents the analytical approach resulted from the conceptual development of the DC-Y composite cryotank, conducted under the NASA/Boeing NRA 8-12 Partnership, to support the continued progress of SSTO (Single-Stage-To-Orbit) concepts. One of the critical areas of design was identified as the bonded interface between the skin (tank wall) and stringer. The approach to analyze this critical area will be illustrated through the steps which were used to evaluate the structural integrity of the bondline. Detailed finite element models were developed and numerous coupon test data were also gathered as part of the approach. Future plan is to incorporate this approach as a building block in analyzing bondline for the cryotank systems of RLVs (Reusable Launch Vehicles).

Fabrication and Characterization of Magnesium Ferrite-Based PCL/Aloe Vera Nanofibers

PubMed Central

Thompson, Zanshe; Rahman, Shekh; Yarmolenko, Sergey; Sankar, Jagannathan; Kumar, Dhananjay

2017-01-01

Composite nanofibers of biopolymers and inorganic materials have been widely explored as tissue engineering scaffolds because of their superior structural, mechanical and biological properties. In this study, magnesium ferrite (Mg-ferrite) based composite nanofibers were synthesized using an electrospinning technique. Mg-ferrite nanoparticles were first synthesized using the reverse micelle method, and then blended in a mixture of polycaprolactone (PCL), a synthetic polymer, and Aloe vera, a natural polymer, to create magnetic nanofibers by electrospinning. The morphology, structural and magnetic properties, and cellular compatibility of the magnetic nanofibers were analyzed. Mg-ferrite/PCL/Aloe vera nanofibers showed good uniformity in fiber morphology, retained their structural integrity, and displayed magnetic strength. Experimental results, using cell viability assay and scanning electron microscopy imaging showed that magnetic nanofibers supported 3T3 cell viability. We believe that the new composite nanofibrous membranes developed in this study have the ability to mimic the physical structure and function of tissue extracellular matrix, as well as provide the magnetic and soluble metal ion attributes in the scaffolds with enhanced cell attachment, and thus improve tissue regeneration. PMID:28800071

Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.

1999-01-01

Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

Fiber-Optic Defect and Damage Locator System for Wind Turbine Blades

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

Dr. Vahid Sotoudeh; Dr. Richard J. Black; Dr. Behzad Moslehi

2010-10-30

IFOS in collaboration with Auburn University demonstrated the feasibility of a Fiber Bragg Grating (FBG) integrated sensor system capable of providing real time in-situ defect detection, localization and quantification of damage. In addition, the system is capable of validating wind turbine blade structural models, using recent advances in non-contact, non-destructive dynamic testing of composite structures. This new generation method makes it possible to analyze wind turbine blades not only non-destructively, but also without physically contacting or implanting intrusive electrical elements and transducers into the structure. Phase I successfully demonstrated the feasibility of the technology with the construction of a 1.5more » kHz sensor interrogator and preliminary instrumentation and testing of both composite material coupons and a wind turbine blade.« less

Factors influencing phase compositions and structure of plasma sprayed hydroxyapatite coatings during heat treatment

NASA Astrophysics Data System (ADS)

Lu, Yu-Peng; Song, Yi-Zhong; Zhu, Rui-Fu; Li, Mu-Sen; Lei, Ting-Quan

2003-02-01

Heat treatment was expected to enhance the long-term reliability of hydroxyapatite (HA) coatings on metal substrates. In this study, factors influencing phase compositions and structure of plasma sprayed hydroxyapatite coatings during heat treatment were carefully analyzed. The phases were characterized by using X-ray diffraction (XRD), the OH - ion contents were determined by Fourier transform infrared (FTIR) spectroscopy. Of the involved factors, heating temperature is of more importance. The appropriate heat treatments is (600- 700 ° C)×2 h for coatings made from fine particles (10-20 μm) and 600 ° C×2 h for coatings made from coarse particles (50-80 μm). The excessive high temperatures and long holding times were unfavorable for the structural integrity of HA.

Crash-Energy Absorbing Composite Structure and Method of Fabrication

NASA Technical Reports Server (NTRS)

Kellas, Sotiris (Inventor); Carden, Huey D. (Inventor)

1996-01-01

A stand-alone, crash-energy absorbing structure and fabrication method are provided. A plurality of adjoining rigid cells are each constructed of resin-cured fiber reinforcement and are arranged in a geometric configuration. The fiber reinforcement can be in the form of a fabric or braided fibers wrapped about a core that is either left in place or removed from the ultimate cured structure. The geometric configuration of cells is held together with more fiber reinforcement (in the form of fabric or braided fibers) in order to integrate the cells in the geometric configuration. The additional fiber reinforcement is resin-cured to the cells. Curing of the cells and ultimate structure can occur in a single step. In applications where post-crash integrity is necessary, ductile fibers can be used to integrate the cells in the geometric configuration. The novelty of the present invention is that simple fabrication techniques are used to create structures that can be formed in a variety of net stable shapes without additional reinforcement and can withstand combined loading while crushing in a desired direction.

Shade tree spatial structure and pod production explain frosty pod rot intensity in cacao agroforests, Costa Rica.

PubMed

Gidoin, Cynthia; Avelino, Jacques; Deheuvels, Olivier; Cilas, Christian; Bieng, Marie Ange Ngo

2014-03-01

Vegetation composition and plant spatial structure affect disease intensity through resource and microclimatic variation effects. The aim of this study was to evaluate the independent effect and relative importance of host composition and plant spatial structure variables in explaining disease intensity at the plot scale. For that purpose, frosty pod rot intensity, a disease caused by Moniliophthora roreri on cacao pods, was monitored in 36 cacao agroforests in Costa Rica in order to assess the vegetation composition and spatial structure variables conducive to the disease. Hierarchical partitioning was used to identify the most causal factors. Firstly, pod production, cacao tree density and shade tree spatial structure had significant independent effects on disease intensity. In our case study, the amount of susceptible tissue was the most relevant host composition variable for explaining disease intensity by resource dilution. Indeed, cacao tree density probably affected disease intensity more by the creation of self-shading rather than by host dilution. Lastly, only regularly distributed forest trees, and not aggregated or randomly distributed forest trees, reduced disease intensity in comparison to plots with a low forest tree density. A regular spatial structure is probably crucial to the creation of moderate and uniform shade as recommended for frosty pod rot management. As pod production is an important service expected from these agroforests, shade tree spatial structure may be a lever for integrated management of frosty pod rot in cacao agroforests.

Lamb Wave Response of Fatigued Composite Samples

NASA Technical Reports Server (NTRS)

Seale, Michael; Smith, Barry T.; Prosser, William H.; Masters, John E.

1994-01-01

Composite materials are being more widely used today by aerospace, automotive, sports equipment, and a number of other commercial industries because of their advantages over conventional metals. Composites have a high strength-to-weight ratio and can be constructed to meet specific design needs. Composite structures are already in use in secondary parts of the Douglas MD-11 and are planned to be used in the new MD-12X. Plans also exist for their use in primary and secondary structures on the Boeing 777. Douglas proposed MD-XX may also incorporate composite materials into primary structures such as the wings and tail. Use of composites in these structures offers weight savings, corrosion resistance, and improved aerodynamics. Additionally, composites have been used to repair cracks in many B-1Bs where traditional repair techniques were not very effective. Plans have also been made to reinforce all of the remaining B-1s with composite materials. Verification of the structural integrity of composite components is needed to insure safe operation of these aerospace vehicles. One aspect of the use of these composites is their response to fatigue. To track this progression of fatigue in aerospace structures, a convenient method to nondestructively monitor this damage needs to be developed. Traditional NDE techniques used on metals are not easily adaptable to composites due to the inhomogeneous and anisotropic nature of these materials. Finding an effective means of nondestructively monitoring fatigue damage is extremely important to the safety and reliability of such structures. Lamb waves offer one method of evaluating these composite materials. As a material is fatigued, the modulus degrades. Since the Lamb wave velocity can be related to the modulus of the material, an effective tool can be developed to monitor fatigue damage in composites by measuring the velocity of these waves. In this work, preliminary studies have been conducted which monitor fatigue damage in composite samples using strain gage measurements as well as Lamb wave velocity measurements. A description of the test samples is followed by the results of two different measurements of Lamb wave velocity. The first technique is a contact measurement done at a single frequency, while the second involves an immersion study of Lamb waves in which dispersion curves are obtained. The results of the Lamb wave monitoring of fatigue damage is compared to the damage progression measured by strain gages. The final section discusses the results and conclusions.

Structural Health Monitoring of a Composite Panel Based on PZT Sensors and a Transfer Impedance Framework

PubMed Central

Dziendzikowski, Michal; Niedbala, Patryk; Kurnyta, Artur; Kowalczyk, Kamil; Dragan, Krzysztof

2018-01-01

One of the ideas for development of Structural Health Monitoring (SHM) systems is based on excitation of elastic waves by a network of PZT piezoelectric transducers integrated with the structure. In the paper, a variant of the so-called Transfer Impedance (TI) approach to SHM is followed. Signal characteristics, called the Damage Indices (DIs), were proposed for data presentation and analysis. The idea underlying the definition of DIs was to maintain most of the information carried by the voltage induced on PZT sensors by elastic waves. In particular, the DIs proposed in the paper should be sensitive to all types of damage which can influence the amplitude or the phase of the voltage induced on the sensor. Properties of the proposed DIs were investigated experimentally using a GFRP composite panel equipped with PZT networks attached to its surface and embedded into its internal structure. Repeatability and stability of DI indications under controlled conditions were verified in tests. Also, some performance indicators for surface-attached and structure-embedded sensors were obtained. The DIs’ behavior was dependent mostly on the presence of a simulated damage in the structure. Anisotropy of mechanical properties of the specimen, geometrical properties of PZT network as well as, to some extent, the technology of sensor integration with the structure were irrelevant for damage indication. This property enables the method to be used for damage detection and classification. PMID:29751664

Development and Sizing of the JWST Integrated Science Instrument Module (ISIM) Metering Structure

NASA Technical Reports Server (NTRS)

Johnston, John; Kunt, Cengiz; Bartoszyk, Andrew; Hendricks, Steve; Cofie, Emmanuel

2006-01-01

The JWST Integrated Science Instrument Module (ISIM) includes a large metering structure (approx. 2m x 2m x 1.5m) that houses the science instruments and guider. Stringent dimensional stability and repeatability requirements combined with mass limitations led to the selection of a composite bonded frame design comprised of biased laminate tubes. Even with the superb material specific stiffness, achieving the required frequency for the given mass allocations in conjunction with severe spatial limitations imposed by the instrument complement has proven challenging. In response to the challenge, the ISIM structure team considered literally over 100 primary structure topology and kinematic mount configurations, and settled on a concept comprised of over 70 m of tubes, over 50 bonded joint assemblies, and a "split bi-pod" kinematic mount configuration. In this paper, we review the evolution of the ISIM primary structure topology and kinematic mount configuration to the current baseline concept.

Military engine computational structures technology

NASA Technical Reports Server (NTRS)

Thomson, Daniel E.

1992-01-01

Integrated High Performance Turbine Engine Technology Initiative (IHPTET) goals require a strong analytical base. Effective analysis of composite materials is critical to life analysis and structural optimization. Accurate life prediction for all material systems is critical. User friendly systems are also desirable. Post processing of results is very important. The IHPTET goal is to double turbine engine propulsion capability by the year 2003. Fifty percent of the goal will come from advanced materials and structures, the other 50 percent will come from increasing performance. Computer programs are listed.

X-33 LH2 Tank Failure Investigation Findings

NASA Technical Reports Server (NTRS)

Niedermeyer, Melinda

2003-01-01

This viewgraph presentation provides information on the composite sandwich-honeycomb structure of the liquid hydrogen tank of the X-33 reusable launch vehicle, and describes why the the first pressure test to determine the tank's structural integrity failed. The presentation includes images of the tank before and after the failed test, including photomicrographs. It then reaches conclusions on the nature of the microcracks which caused the liquid hydrogen leakage.

The Emergence of Compositional Communication in a Synthetic Ethology Framework

DTIC Science & Technology

2005-08-12

34Integrating Language and Cognition: A Cognitive Robotics Approach", invited contribution to IEEE Computational Intelligence Magazine . The first two...papers address the main topic of investigation of the research proposal. In particular, we have introduced a simple structured meaning-signal mapping...Cavalli-Sforza (1982) to investigate analytically the evolution of structured com- munication codes. Let x 6 [0,1] be the proportion of individuals in a

Thermo-mechanical evaluation of carbon-carbon primary structure for SSTO vehicles

NASA Astrophysics Data System (ADS)

Croop, Harold C.; Lowndes, Holland B.; Hahn, Steven E.; Barthel, Chris A.

1998-01-01

An advanced development program to demonstrate carbon-carbon composite structure for use as primary load carrying structure has entered the experimental validation phase. The component being evaluated is a wing torque box section for a single-stage-to-orbit (SSTO) vehicle. The validation or demonstration component features an advanced carbon-carbon design incorporating 3D woven graphite preforms, integral spars, oxidation inhibited matrix, chemical vapor deposited (CVD) oxidation protection coating, and ceramic matrix composite fasteners. The validation component represents the culmination of a four phase design and fabrication development effort. Extensive developmental testing was performed to verify material properties and integrity of basic design features before committing to fabrication of the full scale box. The wing box component is now being set up for testing in the Air Force Research Laboratory Structural Test Facility at Wright-Patterson Air Force Base, Ohio. One of the important developmental tests performed in support of the design and planned testing of the full scale box was the fabrication and test of a skin/spar trial subcomponent. The trial subcomponent incorporated critical features of the full scale wing box design. This paper discusses the results of the trial subcomponent test which served as a pathfinder for the upcoming full scale box test.

Assessment of Damage Containment Features of a Full-Scale PRSEUS Fuselage Panel Through Test and Teardown

NASA Technical Reports Server (NTRS)

Bergan, Andrew C.; Bakuckas, John G., Jr.; Lovejoy, Andrew E.; Jegley, Dawn C.; Awerbuch, Jonathan; Tan, Tein-Min

2012-01-01

An area that shows promise in enhancing structural integrity of aircraft and aerospace structures is the integrally stitched composite technology. The most recent generation of this technology is the Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) concept developed by Boeing Research and Technology and the National Aeronautics and Space Administration. A joint test program on the assessment of damage containment capabilities of the PRSEUS concept for curved fuselage structures was conducted recently at the Federal Aviation Administration William J. Hughes Technical Center. The panel was subjected to axial tension, internal pressure, and combined axial tension and internal pressure load conditions up to fracture, with a through-the-thickness, two-bay notch severing the central stiffener. For the purpose of future progressive failure analysis development and verification, extensive post failure nondestructive and teardown inspections were conducted. Detailed inspections were performed directly ahead of the notch tip where stable damage progression was observed. These examinations showed: 1) extensive delaminations developed ahead of the notch tip, 2) the extent and location of damage, 3) the typical damage mechanisms observed in composites, and 4) the role of stitching and warp-knitting in the failure mechanisms. The objective of this paper is to provide a summary of results from these posttest inspections.

Experimental Modal Analysis and Dynaic Strain Fiber Bragg Gratings for Structural Health Monitoring of Composite Aerospace Structures

NASA Astrophysics Data System (ADS)

Panopoulou, A.; Fransen, S.; Gomez Molinero, V.; Kostopoulos, V.

2012-07-01

The objective of this work is to develop a new structural health monitoring system for composite aerospace structures based on dynamic response strain measurements and experimental modal analysis techniques. Fibre Bragg Grating (FBG) optical sensors were used for monitoring the dynamic response of the composite structure. The structural dynamic behaviour has been numerically simulated and experimentally verified by means of vibration testing. The hypothesis of all vibration tests was that actual damage in composites reduces their stiffness and produces the same result as mass increase produces. Thus, damage was simulated by slightly varying locally the mass of the structure at different zones. Experimental modal analysis based on the strain responses was conducted and the extracted strain mode shapes were the input for the damage detection expert system. A feed-forward back propagation neural network was the core of the damage detection system. The features-input to the neural network consisted of the strain mode shapes, extracted from the experimental modal analysis. Dedicated training and validation activities were carried out based on the experimental results. The system showed high reliability, confirmed by the ability of the neural network to recognize the size and the position of damage on the structure. The experiments were performed on a real structure i.e. a lightweight antenna sub- reflector, manufactured and tested at EADS CASA ESPACIO. An integrated FBG sensor network, based on the advantage of multiplexing, was mounted on the structure with optimum topology. Numerical simulation of both structures was used as a support tool at all the steps of the work. Potential applications for the proposed system are during ground qualification extensive tests of space structures and during the mission as modal analysis tool on board, being able via the FBG responses to identify a potential failure.

Evaluation of energy absorption of new concepts of aircraft composite subfloor intersections

NASA Technical Reports Server (NTRS)

Jones, Lisa E.; Carden, Huey D.

1989-01-01

Forty-one composite aircraft subfloor intersection specimens were tested to determine the effects of geometry and material on the energy absorbing behavior, failure characteristics, and post-crush structural integrity of the specimens. The intersections were constructed of twelve ply + or - 45 sub 6 laminates of either Kevlar 49/934 or AS-4/934 graphite-epoxy in heights of 4, 8, and 12 inches. The geometry of the specimens varied in the designs of the intersection attachment angle. Four different geometries were tested.

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.

Integrated Analysis Tools for Determination of Structural Integrity and Durability of High temperature Polymer Matrix Composites

DTIC Science & Technology

2008-08-18

fidelity will be used to reduce the massive experimental testing and associated time required for qualification of new materials. Tools and...develping a model of the thermo-oxidative process for polymer systems, that incorporates the effects of reaction rates, Fickian diffusion, time varying...degradation processes. Year: 2005 Month: 12 Not required at this time . AIR FORCE OFFICE OF SCIENTIFIC KESEARCH 04 SEP 2008 Page 2 of 2 DTIC Data

Integrated plumage colour variation in relation to body condition, reproductive investment and laying date in the collared flycatcher

NASA Astrophysics Data System (ADS)

Laczi, Miklós; Hegyi, Gergely; Herényi, Márton; Kiss, Dorottya; Markó, Gábor; Nagy, Gergely; Rosivall, Balázs; Szöllősi, Eszter; Török, János

2013-10-01

The possible integration of different sexual ornaments into a composite system, and especially the information content of such ornament complexes, is poorly investigated. Many bird species display complex plumage coloration, but whether this represents one integrated or several independent sexual traits can be unclear. Collared flycatchers ( Ficedula albicollis) display melanised and depigmented plumage areas, and the spectral features (brightness and UV chroma) of these are correlated with each other across the plumage. In a 5-year dataset of male and female plumage reflectance, we examined some of the potential information content of integrated, plumage-level colour attributes by estimating their relationships to previous and current year body condition, laying date and clutch size. Females were in better condition the year before they became darker pigmented, and males in better current year condition were also darker pigmented. Female pigment-based brightness was positively, while male structurally based brightness was negatively related to current laying date. Finally, the overall UV chroma of white plumage areas in males was positively associated with current clutch size. Our results show that higher degree of pigmentation is related to better condition, while the structural colour component is associated with some aspects of reproductive investment. These results highlight the possibility that correlated aspects of a multiple plumage ornamentation system may reflect together some aspects of individual quality, thereby functioning as a composite signal.

Coupled attenuation and multiscale damage model for composite structures

NASA Astrophysics Data System (ADS)

Moncada, Albert M.; Chattopadhyay, Aditi; Bednarcyk, Brett; Arnold, Steven M.

2011-04-01

Composite materials are widely used in many applications for their high strength, low weight, and tailorability for specific applications. However, the development of robust and reliable methodologies to detect micro level damage in composite structures has been challenging. For composite materials, attenuation of ultrasonic waves propagating through the media can be used to determine damage within the material. Currently available numerical solutions for attenuation induce arbitrary damage, such as fiber-matrix debonding or inclusions, to show variations between healthy and damaged states. This paper addresses this issue by integrating a micromechanics analysis to simulate damage in the form of a fiber-matrix crack and an analytical model for calculating the attenuation of the waves when they pass through the damaged region. The hybrid analysis is validated by comparison with experimental stress-strain curves and piezoelectric sensing results for attenuation measurement. The results showed good agreement between the experimental stress-strain curves and the results from the micromechanics analysis. Wave propagation analysis also showed good correlation between simulation and experiment for the tested frequency range.

MoSi2-Base Structural Composite Passed Engine Test

NASA Technical Reports Server (NTRS)

Nathal, Michael V.; Hebsur, Mohan G.

1999-01-01

The intermetallic compound molybdenum disilicide (MoSi2) is an attractive high-temperature structural material for advanced engine applications. It has excellent oxidation resistance, a high melting point, relatively low density, and high thermal conductivity; and it is easily machined. Past research at the NASA Lewis Research Center has resulted in the development of a hybrid composite consisting of a MoSi2 matrix reinforced with silicon nitride (Si3N4) particulate and silicon carbide (SiC) fibers. This composite has demonstrated attractive strength, toughness, thermal fatigue, and oxidation resistance, including resistance to "pest" oxidation. These properties attracted the interest of the Office of Naval Research and Pratt & Whitney, and a joint NASA/Navy/Pratt & Whitney effort was developed to continue to mature the MoSi2 composite technology. A turbine blade outer air seal, which was part of the Integrated High Performance Turbine Engine Technology (IHPTET) program, was chosen as a first component on which to focus.

Micromechanics-Based Structural Analysis (FEAMAC) and Multiscale Visualization within Abaqus/CAE Environment

NASA Technical Reports Server (NTRS)

Arnold, Steven M.; Bednarcyk, Brett A.; Hussain, Aquila; Katiyar, Vivek

2010-01-01

A unified framework is presented that enables coupled multiscale analysis of composite structures and associated graphical pre- and postprocessing within the Abaqus/CAE environment. The recently developed, free, Finite Element Analysis--Micromechanics Analysis Code (FEAMAC) software couples NASA's Micromechanics Analysis Code with Generalized Method of Cells (MAC/GMC) with Abaqus/Standard and Abaqus/Explicit to perform micromechanics based FEA such that the nonlinear composite material response at each integration point is modeled at each increment by MAC/GMC. The Graphical User Interfaces (FEAMAC-Pre and FEAMAC-Post), developed through collaboration between SIMULIA Erie and the NASA Glenn Research Center, enable users to employ a new FEAMAC module within Abaqus/CAE that provides access to the composite microscale. FEA IAC-Pre is used to define and store constituent material properties, set-up and store composite repeating unit cells, and assign composite materials as sections with all data being stored within the CAE database. Likewise FEAMAC-Post enables multiscale field quantity visualization (contour plots, X-Y plots), with point and click access to the microscale i.e., fiber and matrix fields).

Fatigue methodology III; Proceedings of the AHS National Technical Specialists' Meeting on Advanced Rotorcraft Structures, Scottsdale, AZ, Oct. 3-5, 1989

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

Not Available

1989-01-01

Papers on rotorcraft and fatigue methodology are presented, covering topics such as reliability design for rotorcraft, a comparison between theory and fatigue test data on stress concentration factors, the retirement lives of rolling element bearings, hydrogen embrittlement risk analysis for high hardness steel parts, and rotating system load monitoring with minimum fixed system instrumentation. Additional topics include usage data collection to improve structural integrity of operational helicopters, usage monitory of military helicopters, improvements to the fatigue substantiation of the H-60 composite tail rotor blade, helicopter surviellance programs, and potential application of automotive fatigue technology in rotorcraft design. Also, consideration ismore » given to fatigue evaluation of C/MH-53 E main rotor damper threaded joints, SH-2F airframe fatigue test program, a ply termination concept for improving fracture and fatigue strength of composite laminates, the analysis and testing of composite panels subject to muzzle blast effects, the certification plan for an all-composite main rotor flexbeam, and the effects of stacking sequence on the flexural strength of composite beams.« less

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles.

PubMed

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-11-02

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials.

Interfacial effect on physical properties of composite media: Interfacial volume fraction with non-spherical hard-core-soft-shell-structured particles

PubMed Central

Xu, Wenxiang; Duan, Qinglin; Ma, Huaifa; Chen, Wen; Chen, Huisu

2015-01-01

Interfaces are known to be crucial in a variety of fields and the interfacial volume fraction dramatically affects physical properties of composite media. However, it is an open problem with great significance how to determine the interfacial property in composite media with inclusions of complex geometry. By the stereological theory and the nearest-surface distribution functions, we first propose a theoretical framework to symmetrically present the interfacial volume fraction. In order to verify the interesting generalization, we simulate three-phase composite media by employing hard-core-soft-shell structures composed of hard mono-/polydisperse non-spherical particles, soft interfaces, and matrix. We numerically derive the interfacial volume fraction by a Monte Carlo integration scheme. With the theoretical and numerical results, we find that the interfacial volume fraction is strongly dependent on the so-called geometric size factor and sphericity characterizing the geometric shape in spite of anisotropic particle types. As a significant interfacial property, the present theoretical contribution can be further drawn into predicting the effective transport properties of composite materials. PMID:26522701

Development of multidisciplinary design optimization procedures for smart composite wings and turbomachinery blades

NASA Astrophysics Data System (ADS)

Jha, Ratneshwar

Multidisciplinary design optimization (MDO) procedures have been developed for smart composite wings and turbomachinery blades. The analysis and optimization methods used are computationally efficient and sufficiently rigorous. Therefore, the developed MDO procedures are well suited for actual design applications. The optimization procedure for the conceptual design of composite aircraft wings with surface bonded piezoelectric actuators involves the coupling of structural mechanics, aeroelasticity, aerodynamics and controls. The load carrying member of the wing is represented as a single-celled composite box beam. Each wall of the box beam is analyzed as a composite laminate using a refined higher-order displacement field to account for the variations in transverse shear stresses through the thickness. Therefore, the model is applicable for the analysis of composite wings of arbitrary thickness. Detailed structural modeling issues associated with piezoelectric actuation of composite structures are considered. The governing equations of motion are solved using the finite element method to analyze practical wing geometries. Three-dimensional aerodynamic computations are performed using a panel code based on the constant-pressure lifting surface method to obtain steady and unsteady forces. The Laplace domain method of aeroelastic analysis produces root-loci of the system which gives an insight into the physical phenomena leading to flutter/divergence and can be efficiently integrated within an optimization procedure. The significance of the refined higher-order displacement field on the aeroelastic stability of composite wings has been established. The effect of composite ply orientations on flutter and divergence speeds has been studied. The Kreisselmeier-Steinhauser (K-S) function approach is used to efficiently integrate the objective functions and constraints into a single envelope function. The resulting unconstrained optimization problem is solved using the Broyden-Fletcher-Goldberg-Shanno algorithm. The optimization problem is formulated with the objective of simultaneously minimizing wing weight and maximizing its aerodynamic efficiency. Design variables include composite ply orientations, ply thicknesses, wing sweep, piezoelectric actuator thickness and actuator voltage. Constraints are placed on the flutter/divergence dynamic pressure, wing root stresses and the maximum electric field applied to the actuators. Numerical results are presented showing significant improvements, after optimization, compared to reference designs. The multidisciplinary optimization procedure for the design of turbomachinery blades integrates aerodynamic and heat transfer design objective criteria along with various mechanical and geometric constraints on the blade geometry. The airfoil shape is represented by Bezier-Bernstein polynomials, which results in a relatively small number of design variables for the optimization. Thin shear layer approximation of the Navier-Stokes equation is used for the viscous flow calculations. Grid generation is accomplished by solving Poisson equations. The maximum and average blade temperatures are obtained through a finite element analysis. Total pressure and exit kinetic energy losses are minimized, with constraints on blade temperatures and geometry. The constrained multiobjective optimization problem is solved using the K-S function approach. The results for the numerical example show significant improvements after optimization.

Printable semiconductor structures and related methods of making and assembling

DOEpatents

Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang; , Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao; Ko, Heung Cho; Mack, Shawn

2013-03-12

The present invention provides a high yield pathway for the fabrication, transfer and assembly of high quality printable semiconductor elements having selected physical dimensions, shapes, compositions and spatial orientations. The compositions and methods of the present invention provide high precision registered transfer and integration of arrays of microsized and/or nanosized semiconductor structures onto substrates, including large area substrates and/or flexible substrates. In addition, the present invention provides methods of making printable semiconductor elements from low cost bulk materials, such as bulk silicon wafers, and smart-materials processing strategies that enable a versatile and commercially attractive printing-based fabrication platform for making a broad range of functional semiconductor devices.

Printable semiconductor structures and related methods of making and assembling

DOEpatents

Nuzzo, Ralph G [Champaign, IL; Rogers, John A [Champaign, IL; Menard, Etienne [Durham, NC; Lee, Keon Jae [Tokyo, JP; Khang, Dahl-Young [Urbana, IL; Sun, Yugang [Westmont, IL; Meitl, Matthew [Raleigh, NC; Zhu, Zhengtao [Rapid City, SD; Ko, Heung Cho [Urbana, IL; Mack, Shawn [Goleta, CA

2011-10-18

The present invention provides a high yield pathway for the fabrication, transfer and assembly of high quality printable semiconductor elements having selected physical dimensions, shapes, compositions and spatial orientations. The compositions and methods of the present invention provide high precision registered transfer and integration of arrays of microsized and/or nanosized semiconductor structures onto substrates, including large area substrates and/or flexible substrates. In addition, the present invention provides methods of making printable semiconductor elements from low cost bulk materials, such as bulk silicon wafers, and smart-materials processing strategies that enable a versatile and commercially attractive printing-based fabrication platform for making a broad range of functional semiconductor devices.

Printable semiconductor structures and related methods of making and assembling

DOEpatents

Nuzzo, Ralph G.; Rogers, John A.; Menard, Etienne; Lee, Keon Jae; Khang, Dahl-Young; Sun, Yugang; Meitl, Matthew; Zhu, Zhengtao; Ko, Heung Cho; Mack, Shawn

2010-09-21

The present invention provides a high yield pathway for the fabrication, transfer and assembly of high quality printable semiconductor elements having selected physical dimensions, shapes, compositions and spatial orientations. The compositions and methods of the present invention provide high precision registered transfer and integration of arrays of microsized and/or nanosized semiconductor structures onto substrates, including large area substrates and/or flexible substrates. In addition, the present invention provides methods of making printable semiconductor elements from low cost bulk materials, such as bulk silicon wafers, and smart-materials processing strategies that enable a versatile and commercially attractive printing-based fabrication platform for making a broad range of functional semiconductor devices.

Overview of mechanics of materials branch activities in the computational structures area

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.

1992-01-01

Base programs and system programs are discussed. The base programs include fundamental research of composites and metals for airframes leading to characterization of advanced materials, models of behavior, and methods for predicting damage tolerance. Results from the base programs support the systems programs, which change as NASA's missions change. The National Aerospace Plane (NASP), Advanced Composites Technology (ACT), Airframe Structural Integrity Program (Aging Aircraft), and High Speed Research (HSR) programs are currently being supported. Airframe durability is one of the key issues in each of these system programs. The base program has four major thrusts, which will be reviewed subsequently. Additionally, several technical highlights will be reviewed for each thrust.

High-k 3D-barium titanate foam/phenolphthalein poly(ether sulfone)/cyanate ester composites with frequency-stable dielectric properties and extremely low dielectric loss under reduced concentration of ceramics

NASA Astrophysics Data System (ADS)

Zheng, Longhui; Yuan, Li; Guan, Qingbao; Liang, Guozheng; Gu, Aijuan

2018-01-01

Higher dielectric constant, lower dielectric loss and better frequency stability have been the developing trends for high dielectric constant (high-k) materials. Herein, new composites have been developed through building unique structure by using hyperbranched polysiloxane modified 3D-barium titanate foam (BTF) (BTF@HSi) as the functional fillers and phenolphthalein poly(ether sulfone) (cPES)/cyanate ester (CE) blend as the resin matrix. For BTF@HSi/cPES/CE composite with 34.1 vol% BTF, its dielectric constant at 100 Hz is as high as 162 and dielectric loss is only 0.007; moreover, the dielectric properties of BTF@HSi/cPES/CE composites exhibit excellent frequency stability. To reveal the mechanism behind these attractive performances of BTF@HSi/cPES/CE composites, three kinds of composites (BTF/CE, BTF/cPES/CE, BTF@HSi/CE) were prepared, their structure and integrated performances were intensively investigated and compared with those of BTF@HSi/cPES/CE composites. Results show that the surface modification of BTF is good for preparing composites with improved thermal stability; while introducing flexible cPES to CE is beneficial to fabricate composites with good quality through effectively blocking cracks caused by the stress concentration, and then endowing the composites with good dielectric properties at reduced concentration of ceramics.

Deterministic composite nanophotonic lattices in large area for broadband applications

NASA Astrophysics Data System (ADS)

Xavier, Jolly; Probst, Jürgen; Becker, Christiane

2016-12-01

Exotic manipulation of the flow of photons in nanoengineered materials with an aperiodic distribution of nanostructures plays a key role in efficiency-enhanced broadband photonic and plasmonic technologies for spectrally tailorable integrated biosensing, nanostructured thin film solarcells, white light emitting diodes, novel plasmonic ensembles etc. Through a generic deterministic nanotechnological route here we show subwavelength-scale silicon (Si) nanostructures on nanoimprinted glass substrate in large area (4 cm2) with advanced functional features of aperiodic composite nanophotonic lattices. These nanophotonic aperiodic lattices have easily tailorable supercell tiles with well-defined and discrete lattice basis elements and they show rich Fourier spectra. The presented nanophotonic lattices are designed functionally akin to two-dimensional aperiodic composite lattices with unconventional flexibility- comprising periodic photonic crystals and/or in-plane photonic quasicrystals as pattern design subsystems. The fabricated composite lattice-structured Si nanostructures are comparatively analyzed with a range of nanophotonic structures with conventional lattice geometries of periodic, disordered random as well as in-plane quasicrystalline photonic lattices with comparable lattice parameters. As a proof of concept of compatibility with advanced bottom-up liquid phase crystallized (LPC) Si thin film fabrication, the experimental structural analysis is further extended to double-side-textured deterministic aperiodic lattice-structured 10 μm thick large area LPC Si film on nanoimprinted substrates.

Chemically Active, Porous 3D-Printed Thermoplastic Composites.

PubMed

Evans, Kent A; Kennedy, Zachary C; Arey, Bruce W; Christ, Josef F; Schaef, Herbert T; Nune, Satish K; Erikson, Rebecca L

2018-05-02

Metal-organic frameworks (MOFs) exhibit exceptional properties and are widely investigated because of their structural and functional versatility relevant to catalysis, separations, and sensing applications. However, their commercial or large-scale application is often limited by their powder forms which make integration into devices challenging. Here, we report the production of MOF-thermoplastic polymer composites in well-defined and customizable forms and with complex internal structural features accessed via a standard three-dimensional (3D) printer. MOFs (zeolitic imidazolate framework; ZIF-8) were incorporated homogeneously into both poly(lactic acid) (PLA) and thermoplastic polyurethane (TPU) matrices at high loadings (up to 50% by mass), extruded into filaments, and utilized for on-demand access to 3D structures by fused deposition modeling. Printed, rigid PLA/MOF composites display a large surface area (SA avg = 531 m 2 g -1 ) and hierarchical pore features, whereas flexible TPU/MOF composites achieve a high surface area (SA avg = 706 m 2 g -1 ) by employing a simple method developed to expose obstructed micropores postprinting. Critically, embedded particles in the plastic matrices retain their ability to participate in chemical interactions characteristic of the parent framework. The fabrication strategies were extended to other MOFs and illustrate the potential of 3D printing to create unique porous and high surface area chemically active structures.

Deterministic composite nanophotonic lattices in large area for broadband applications

PubMed Central

Xavier, Jolly; Probst, Jürgen; Becker, Christiane

2016-01-01

Exotic manipulation of the flow of photons in nanoengineered materials with an aperiodic distribution of nanostructures plays a key role in efficiency-enhanced broadband photonic and plasmonic technologies for spectrally tailorable integrated biosensing, nanostructured thin film solarcells, white light emitting diodes, novel plasmonic ensembles etc. Through a generic deterministic nanotechnological route here we show subwavelength-scale silicon (Si) nanostructures on nanoimprinted glass substrate in large area (4 cm2) with advanced functional features of aperiodic composite nanophotonic lattices. These nanophotonic aperiodic lattices have easily tailorable supercell tiles with well-defined and discrete lattice basis elements and they show rich Fourier spectra. The presented nanophotonic lattices are designed functionally akin to two-dimensional aperiodic composite lattices with unconventional flexibility- comprising periodic photonic crystals and/or in-plane photonic quasicrystals as pattern design subsystems. The fabricated composite lattice-structured Si nanostructures are comparatively analyzed with a range of nanophotonic structures with conventional lattice geometries of periodic, disordered random as well as in-plane quasicrystalline photonic lattices with comparable lattice parameters. As a proof of concept of compatibility with advanced bottom-up liquid phase crystallized (LPC) Si thin film fabrication, the experimental structural analysis is further extended to double-side-textured deterministic aperiodic lattice-structured 10 μm thick large area LPC Si film on nanoimprinted substrates. PMID:27941869

Static aeroelastic behavior of an adaptive laminated piezoelectric composite wing

NASA Technical Reports Server (NTRS)

Weisshaar, T. A.; Ehlers, S. M.

1990-01-01

The effect of using an adaptive material to modify the static aeroelastic behavior of a uniform wing is examined. The wing structure is idealized as a laminated sandwich structure with piezoelectric layers in the upper and lower skins. A feedback system that senses the wing root loads applies a constant electric field to the piezoelectric actuator. Modification of pure torsional deformaton behavior and pure bending deformation are investigated, as is the case of an anisotropic composite swept wing. The use of piezoelectric actuators to create an adaptive structure is found to alter static aeroelastic behavior in that the proper choice of the feedback gain can increase or decrease the aeroelastic divergence speed. This concept also may be used to actively change the lift effectiveness of a wing. The ability to modify static aeroelastic behavior is limited by physical limitations of the piezoelectric material and the manner in which it is integrated into the parent structure.

Experimental study of optical and electrical properties of ZnO nano composites electrodeposited on n-porous silicon substrate for photovoltaic applications

NASA Astrophysics Data System (ADS)

Selmane, Naceur; Cheknane, Ali; Gabouze, Nourddine; Maloufi, Nabila; Aillerie, Michel

2017-11-01

ZnO films deposited on silicon porous substrates (PS) were prepared by electro-deposition anodization on n type (100) silicon wafer. This ZnO/PS structure combines substrates having specific structural and optical properties (IR emission), with nano-composites of ZnO potentially interesting due to their functional properties (UV emission) to be integrated as constitutive elements of devices in various optoelectronic applications mainly in blue light emitters. With this combined structure, the blue shift in the PL peak is possible and easy to obtain (467nm). The vibration modes of PS and ZnO films on PS substrates (ZnO /PS) were investigated by infrared (FTIR) measurements and their behaviors were analyzed and discussed by considering the structural properties characterized by X-ray diffraction (DRX) and scanning electronic microscopy (MEB).

Progressive Fracture of [0/90/ + or - Theta]s Composite Structure Under Uniform Pressure Load

NASA Technical Reports Server (NTRS)

Gotsis, Pascalis K.; Chamis, Christos C.; Gotsis, Christos K.; Mouratidis, Ericos

2007-01-01

S-Glass/epoxy [0/90/plus or minus theta]s for theta =45 deg., 60 deg., and 75 deg. laminated fiber-reinforced composite stiffened plate was simulated to investigated for damage and fracture progression under uniform pressure. An integrated computer code was augmented for the simulation of the damage initiation, growth, accumulation, and propagation to fracture and to structural collapse. Results show in detail the damage progression sequence and structural fracture resistance during different degradation stages. Damage through the thickness of the laminate initiated first at [0/90/plus or minus 45]s at 15.168 MPa (2200 psi), followed by [0/90/plus or minus 60]s at 16.96 MPa (2460 psi) and finally by [0/90/plus or minus 75]s at 19.3 MPa (2800 psi). After damage initiation happened the cracks propagate rapidly to structural fracture.

Stress-corrosion cracking in metals

NASA Technical Reports Server (NTRS)

1971-01-01

Criteria and recommended practices for preventing stress-corrosion cracking from impairing the structural integrity and flightworthiness of space vehicles are presented. The important variables affecting stress-corrosion cracking are considered to be the environment, including time and temperature; metal composition, and structure; and sustained tensile stress. For designing spacecraft structures that are free of stress-corrosion cracking for the service life of the vehicle the following rules apply: (1) identification and control of the environments to which the structure will be exposed during construction, storage, transportation, and use; (2) selection of alloy compositions and tempers which are resistant to stress-corrosion cracking in the identified environment; (3) control of fabrication and other processes which may introduce residual tensile stresses or damage the material; (4) limitation of the combined residual and applied tensile stresses to below the threshold stress level for the onset of cracking throughout the service life of the vehicle; and (5) establishment of a thorough inspection program.

System-on-chip integration of a new electromechanical impedance calculation method for aircraft structure health monitoring.

PubMed

Boukabache, Hamza; Escriba, Christophe; Zedek, Sabeha; Medale, Daniel; Rolet, Sebastien; Fourniols, Jean Yves

2012-10-11

The work reported on this paper describes a new methodology implementation for active structural health monitoring of recent aircraft parts made from carbon-fiber-reinforced polymer. This diagnosis is based on a new embedded method that is capable of measuring the local high frequency impedance spectrum of the structure through the calculation of the electro-mechanical impedance of a piezoelectric patch pasted non-permanently onto its surface. This paper involves both the laboratory based E/M impedance method development, its implementation into a CPU with limited resources as well as a comparison with experimental testing data needed to demonstrate the feasibility of flaw detection on composite materials and answer the question of the method reliability. The different development steps are presented and the integration issues are discussed. Furthermore, we present the unique advantages that the reconfigurable electronics through System-on-Chip (SoC) technology brings to the system scaling and flexibility. At the end of this article, we demonstrate the capability of a basic network of sensors mounted onto a real composite aircraft part specimen to capture its local impedance spectrum signature and to diagnosis different delamination sizes using a comparison with a baseline.

System-on-Chip Integration of a New Electromechanical Impedance Calculation Method for Aircraft Structure Health Monitoring

PubMed Central

Boukabache, Hamza; Escriba, Christophe; Zedek, Sabeha; Medale, Daniel; Rolet, Sebastien; Fourniols, Jean Yves

2012-01-01

The work reported on this paper describes a new methodology implementation for active structural health monitoring of recent aircraft parts made from carbon-fiber-reinforced polymer. This diagnosis is based on a new embedded method that is capable of measuring the local high frequency impedance spectrum of the structure through the calculation of the electro-mechanical impedance of a piezoelectric patch pasted non-permanently onto its surface. This paper involves both the laboratory based E/M impedance method development, its implementation into a CPU with limited resources as well as a comparison with experimental testing data needed to demonstrate the feasibility of flaw detection on composite materials and answer the question of the method reliability. The different development steps are presented and the integration issues are discussed. Furthermore, we present the unique advantages that the reconfigurable electronics through System-on-Chip (SoC) technology brings to the system scaling and flexibility. At the end of this article, we demonstrate the capability of a basic network of sensors mounted onto a real composite aircraft part specimen to capture its local impedance spectrum signature and to diagnosis different delamination sizes using a comparison with a baseline. PMID:23202013

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.

Feasibility on fiber orientation detection on unidirectional CFRP composite laminates using nondestructive evaluation techniques

NASA Astrophysics Data System (ADS)

Yang, In-Young; Kim, Ji-Hoon; Cha, Cheon-Seok; Lee, Kil-Sung; Hsu, David K.; Im, Kwang-Hee

2007-07-01

In particular, CFRP (carbon fiber reinforced plastics) composite materials have found wide applicability because of their inherent design flexibility and improved material properties. CFRP composites were manufactured from uni-direction prepreg sheet in this paper. It is important to assess fiber orientation, material properties and part defect in order to ensure product quality and structural integrity of CFRP because strength and stiffness of composites depend on fiber orientation. It is desirable to perform nondestructive evaluation which is very beneficial. An new method for nondestructively determining the fiber orientation in a composite laminate is presented. A one-sided pitch-catch setup was used in the detection and evaluation of flaws and material anomalies in the unidirectional CFRP composite laminates. Two Rayleigh wave transducers were joined head-to-head and used in the pitch-catch mode on the surface of the composites. The pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composite. Especially, ultrasonic waves were extensively characterized in the CFRP composite laminates both normal to fiber and along to fiber with using a one-sided direction of Rayleigh wave transducers. Also, one-sided ultrasonic measurement was made with using a Rayleigh wave transducers and a conventional scanner was used in an immersion tank for extracting fiber orientation information from the ultrasonic reflection in the unidirectional laminate. Therefore, it is thought that the proposed method is useful to evaluate integrity of CFRP laminates.

Finite Element Modeling of the Thermographic Inspection for Composite Materials

NASA Technical Reports Server (NTRS)

Bucinell, Ronald B.

1996-01-01

The performance of composite materials is dependent on the constituent materials selected, material structural geometry, and the fabrication process. Flaws can form in composite materials as a result of the fabrication process, handling in the manufacturing environment, and exposure in the service environment to anomalous activity. Often these flaws show no indication on the surface of the material while having the potential of substantially degrading the integrity of the composite structure. For this reason it is important to have available inspection techniques that can reliably detect sub-surface defects such as inter-ply disbonds, inter-ply cracks, porosity, and density changes caused by variations in fiber volume content. Many non-destructive evaluation techniques (NDE) are capable of detecting sub-surface flaws in composite materials. These include shearography, video image correlation, ultrasonic, acoustic emissions, and X-ray. The difficulty with most of these techniques is that they are time consuming and often difficult to apply to full scale structures. An NDE technique that appears to have the capability to quickly and easily detect flaws in composite structure is thermography. This technique uses heat to detect flaws. Heat is applied to the surface of a structure with the use of a heat lamp or heat gun. A thermographic camera is then pointed at the surface and records the surface temperature as the composite structure cools. Flaws in the material will cause the thermal-mechanical material response to change. Thus, the surface over an area where a flaw is present will cool differently than regions where flaws do not exist. This paper discusses the effort made to thermo-mechanically model the thermography process. First the material properties and physical parameters used in the model will be explained. This will be followed by a detailed discussion of the finite element model used. Finally, the result of the model will be summarized along with recommendations for future work.

Design and analysis of multifunctional structures for embedded electronics in unmanned aerial vehicles

NASA Astrophysics Data System (ADS)

Kothari, Rushabh M.

Multifunctional structures are a new trend in the aerospace industry for the next generation structural design. Many future structures are expected to be something in addition to a load bearing structure. The design and analysis of multifunctional structures combining structural, electrical and thermal functionalities are presented here. The sandwich beam is considered as a starting point for the load bearing structure and then it is modified with a cavity to embed avionics and thermal controls. The embedded avionics inside the load bearing structure would allow weight reduction of the aerospace vehicle due to elimination of separate electronics housing, interconnects, cables etc. The cavity reduces strength of the structure so various reinforcements methods are evaluated. The result of various reinforcements and their effectiveness are presented. The current generation of electronics produce massive amount of heat. In the case of embedded electronics, the excessive heat presents a major challenge to the structural and heat transfer engineers. The embedded nature of electronics prevents the use of the classical heat dissipative methods such as fans and high velocity air flows, etc. The integrated thermal control of the electronics has been designed using passive heat transfer device and highly optimized particulate composite thermal interface material (TIM). The TIMs are used to fill the air gaps and reduce contact resistance between two surfaces, such as electronics and heat dissipators. The efficiency of TIM directly affects the overall heat transfer ability of the integrated thermal control system. The effect of the particles at micron and nano scales are studied for the particulate composite TIM. The thermal boundary resistance study for the particulate composite TIM with nano silica particles is presented in this thesis. The FEA analysis is used to model thermal boundary resistance and compared with the theoretical micromechanics model. The heat pipes are chosen as a part of passive heat transfer device due to their durability and excellent thermal conductivities. The multifunctional system consisting of all above components is modeled for unmanned aerial vehicle (UAV) at subsonic air speeds to demonstrate the validity of the design.

A self-diagnostic adhesive for monitoring bonded joints in aerospace structures

NASA Astrophysics Data System (ADS)

Zhuang, Yitao; Li, Yu-hung; Kopsaftopoulos, Fotis; Chang, Fu-Kuo

2016-04-01

Bondline integrity is still one of the most critical concerns in the design of aircraft structures up to date. Due to the lack of confidence on the integrity of the bondline both during fabrication and service, the industry standards and regulations still require assembling the composite using conventional fasteners. Furthermore, current state-of-the-art non-destructive evaluation (NDE) and structural health monitoring (SHM) techniques are incapable of offering mature solutions on the issue of bondline integrity monitoring. Therefore, the objective of this work is the development of an intelligent adhesive film with integrated micro-sensors for monitoring the integrity of the bondline interface. The proposed method makes use of an electromechanical-impedance (EMI) based method, which is a rapidly evolving approach within the SHM family. Furthermore, an innovative screen-printing technique to fabricate piezoelectric ceramic sensors with minimal thickness has been developed at Stanford. The approach presented in this study is based on the use of (i) micro screen-printed piezoelectric sensors integrated into adhesive leaving a minimal footprint on the material, (ii) numerical and analytical modeling of the EMI spectrum of the adhesive bondline, (iii) novel diagnostic algorithms for monitoring the bondline integrity based on advanced signal processing techniques, and (iv) the experimental assessment via prototype adhesively bonded structures in static (varying loads) and dynamic (fatigue) environments. The proposed method will provide a huge confidence on the use of bonded joints for aerospace structures and lead to a paradigm change in their design by enabling enormous weight savings while maximizing the economic and performance efficiency.

Application of low-coherence interferometry for in situ nondestructive evaluation of thin and thick multilayered transparent composites

NASA Astrophysics Data System (ADS)

Khomenko, Anton; Cloud, Gary Lee; Haq, Mahmoodul

2015-12-01

Multilayered transparent composites having laminates with polymer interlayers and backing sheets are commonly used in a wide range of applications where visibility, transparency, impact resistance, and safety are essential. Manufacturing flaws or damage during operation can seriously compromise both safety and performance. Most fabrication defects are not discernible until after the entire multilayered transparent composite assembly has been completed, and in-the-field inspection for damage is a problem not yet solved. A robust and reliable nondestructive evaluation (NDE) technique is needed to evaluate structural integrity and identify defects that result from manufacturing issues as well as in-service damage arising from extreme environmental conditions in addition to normal mechanical and thermal loads. Current optical techniques have limited applicability for NDE of such structures. This work presents a technique that employs a modified interferometer utilizing a laser diode or femtosecond fiber laser source to acquire in situ defect depth location inside a thin or thick multilayered transparent composite, respectively. The technique successfully located various defects inside examined composites. The results show great potential of the technique for defect detection, location, and identification in multilayered transparent composites.

Integrated inventory and monitoring

Treesearch

George Lightner; Hans T. Schreuder; Barry Bollenbacher; Kerry McMenus

2001-01-01

Understanding and inventorying our ecological systems is key to addressing how issues, questions, and management actions will affect the composition, structure, and function of these systems. Taking an ecological systems approach to the inventory and monitoring framework, is one which we feel will allow answers to currently identified management questions and new ones...

A Composite Model for Employees' Performance Appraisal and Improvement

ERIC Educational Resources Information Center

Manoharan, T. R.; Muralidharan, C.; Deshmukh, S. G.

2012-01-01

Purpose: The purpose of this paper is to develop an innovative method of performance appraisal that will be useful for designing a structured training programme. Design/methodology/approach: Employees' performance appraisals are conducted using new approaches, namely data envelopment analysis and an integrated fuzzy model. Interpretive structural…

Estimating Creativity with a Multiple-Measurement Approach within Scientific and Artistic Domains

ERIC Educational Resources Information Center

Agnoli, Sergio; Corazza, Giovanni E.; Runco, Mark A.

2016-01-01

This article presents the structure and the composition of a newly developed multifaceted test battery for the measurement of creativity within scientific and artistic domains. By integrating existing procedures for the evaluation of creativity, the new battery promises to become a comprehensive assessment of creativity, encompassing both…

Integrated reclamation: Approaching ecological function?

Treesearch

Ann L. Hild; Nancy L. Shaw; Ginger B. Paige

2009-01-01

Attempts to reclaim arid and semiarid lands have traditionally targeted plant species composition. Much research attention has been directed to seeding rates, species mixes and timing of seeding. However, in order to attain functioning systems, attention to structure and process must compliment existing efforts. We ask how to use a systems approach to enhance...

Self-healing polymers and composites based on thermal activation

NASA Astrophysics Data System (ADS)

Wang, Ying; Bolanos, Ed; Wudl, Fred; Hahn, Thomas; Kwok, Nathan

2007-04-01

Structural polymer composites are susceptible to premature failure in the form of microcracks in the matrix. Although benign initially when they form, these matrix cracks tend to coalesce and lead in service to critical damage modes such as ply delamination. The matrix cracks are difficult to detect and almost impossible to repair because they form inside the composite laminate. Therefore, polymers with self-healing capability would provide a promising potential to minimize maintenance costs while extending the service lifetime of composite structures. In this paper we report on a group of polymers and their composites which exhibit mendable property upon heating. The failure and healing mechanisms of the polymers involve Diels-Alder (DA) and retro-Diels-Alder (RDA) reactions on the polymer back-bone chain, which are thermally reversible reactions requiring no catalyst. The polymers exhibited good healing property in bulk form. Composite panels were prepared by sandwiching the monomers between carbon fiber fabric layers and cured in autoclave. Microcracks were induced on the resin-rich surface of composite with Instron machine at room temperature by holding at 1% strain for 1 min. The healing ability of the composite was also demonstrated by the disappearance of microcracks after heating. In addition to the self-healing ability, the polymers and composites also exhibited shape memory property. These unique properties may provide the material multi-functional applications. Resistance heating of traditional composites and its applicability in self-healing composites is also studied to lay groundwork for a fully integrated self-healing composite.

MEMS- and NEMS-based smart devices and systems

NASA Astrophysics Data System (ADS)

Varadan, Vijay K.

2001-11-01

The microelectronics industry has seen explosive growth during the last thirty years. Extremely large markets for logic and memory devices have driven the development of new materials, and technologies for the fabrication of even more complex devices with features sized now don at the sub micron and nanometer level. Recent interest has arisen in employing these materials, tools and technologies for the fabrication of miniature sensors and actuators and their integration with electronic circuits to produce smart devices and systems. This effort offers the promise of: 1) increasing the performance and manufacturability of both sensors and actuators by exploiting new batch fabrication processes developed including micro stereo lithographic an micro molding techniques; 2) developing novel classes of materials and mechanical structures not possible previously, such as diamond like carbon, silicon carbide and carbon nanotubes, micro-turbines and micro-engines; 3) development of technologies for the system level and wafer level integration of micro components at the nanometer precision, such as self-assembly techniques and robotic manipulation; 4) development of control and communication systems for MEMS devices, such as optical and RF wireless, and power delivery systems, etc. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross-linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composite provide a new avenue for future smart systems. The integration of NEMS (NanoElectroMechanical Systems), MEMS, IDTs (Interdigital Transducers) and required microelectronics and conformal antenna in the multifunctional smart materials and composites results in a smart system suitable for sensing and control of a variety functions in automobile, aerospace, marine and civil structures and food and medical industries. This unique combination of technologies also results in novel conformal sensors that can be remotely sensed by an antenna system with the advantage of no power requirements at the sensor site. This paper provides a brief review of MEMS and NEMS based smart systems for various applications mentioned above. Carbon Nano Tubes (CNT) with their unique structure, have already proven to be valuable in their application as tips for scanning probe microscopy, field emission devices, nanoelectronics, H2-storage, electromagnetic absorbers, ESD, EMI films and coatings and structural composites. For many of these applications, highly purified and functionalized CNT which are compatible with many host polymers are needed. A novel microwave CVD processing technique to meet these requirements has been developed at Penn State Center for the engineering of Electronic and Acoustic Materials and Devices (CEEAMD). This method enables the production of highly purified carbon nano tubes with variable size (from 5-40 nm) at low cost (per gram) and high yield. Whereas, carbon nano tubes synthesized using the laser ablation or arc discharge evaporation method always include impurity due to catalyst or catalyst support. The Penn State research is based on the use of zeolites over other metal/metal oxides in the microwave field for a high production and uniformity of the product. An extended conventional purification method has been employed to purify our products in order to remove left over impurity. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross- linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composites will be presented.

Dynamic Stability of Uncertain Laminated Beams Under Subtangential Loads

NASA Technical Reports Server (NTRS)

Goyal, Vijay K.; Kapania, Rakesh K.; Adelman, Howard (Technical Monitor); Horta, Lucas (Technical Monitor)

2002-01-01

Because of the inherent complexity of fiber-reinforced laminated composites, it can be challenging to manufacture composite structures according to their exact design specifications, resulting in unwanted material and geometric uncertainties. In this research, we focus on the deterministic and probabilistic stability analysis of laminated structures subject to subtangential loading, a combination of conservative and nonconservative tangential loads, using the dynamic criterion. Thus a shear-deformable laminated beam element, including warping effects, is derived to study the deterministic and probabilistic response of laminated beams. This twenty-one degrees of freedom element can be used for solving both static and dynamic problems. In the first-order shear deformable model used here we have employed a more accurate method to obtain the transverse shear correction factor. The dynamic version of the principle of virtual work for laminated composites is expressed in its nondimensional form and the element tangent stiffness and mass matrices are obtained using analytical integration The stability is studied by giving the structure a small disturbance about an equilibrium configuration, and observing if the resulting response remains small. In order to study the dynamic behavior by including uncertainties into the problem, three models were developed: Exact Monte Carlo Simulation, Sensitivity Based Monte Carlo Simulation, and Probabilistic FEA. These methods were integrated into the developed finite element analysis. Also, perturbation and sensitivity analysis have been used to study nonconservative problems, as well as to study the stability analysis, using the dynamic criterion.

A Mixed-Mode (I-II) Fracture Criterion for AS4/8552 Carbon/Epoxy Composite Laminate

NASA Astrophysics Data System (ADS)

Karnati, Sidharth Reddy

A majority of aerospace structures are subjected to bending and stretching loads that introduce peel and shear stresses between the plies of a composite laminate. These two stress components cause a combination of mode I and II fracture modes in the matrix layer of the composite laminate. The most common failure mode in laminated composites is delamination that affects the structural integrity of composite structures. Damage tolerant designs of structures require two types of materials data: mixed-mode (I-II) delamination fracture toughness that predicts failure and delamination growth rate that predicts the life of the structural component. This research focuses determining mixed-mode (I-II) fracture toughness under a combination of mode I and mode II stress states and then a fracture criterion for AS4/8552 composite laminate, which is widely used in general aviation. The AS4/8552 prepreg was supplied by Hexcel Corporation and autoclave fabricated into a 20-ply unidirectional laminate with an artificial delamination by a Fluorinated Ethylene Propylene (FEP) film at the mid-plane. Standard split beam specimens were prepared and tested in double cantilever beam (DCB) and end notched flexure modes to determine mode I (GIC) and II (GIIC) fracture toughnesses, respectively. The DCB specimens were also tested in a modified mixed-mode bending apparatus at GIIm /GT ratios of 0.18, 0.37, 0.57 and 0.78, where GT is total and GIIm is the mode II component of energy release rates. The measured fracture toughness, GC, was found to follow the locus a power law equation. The equation was validated for the present and literature experimental data.

Investigation of Interrelation between Deformation, Composition and Structural Characteristics of Magnesium Oxychloride Cements

NASA Astrophysics Data System (ADS)

Averina, G. F.; Chernykh, T. N.; Kramar, L. Ya

2017-11-01

The paper studies the process of volume deformation changes in magnesium cement at its hardening in accordance with its composition and structural peculiarities, which result from the roasting parameters of the raw materials. The study has been carried out with the aim of broadening raw materials sources for production of magnesia cements and construction materials through the use waste products of ore-dressing and processing enterprises. The mineralogical and phase composition of magnesium cements, obtained on the basis of magnesite with high content of impurity minerals from the mine dumps, has been studied by the X-ray phase analysis and derivatography. The roasting of the initial raw materials was carried out at various temperature conditions in order to get cements of different activities. The typical content of hydrated phases has been found for the hardened magnesian stone obtained from cements with different activity degrees. The characteristics of volume deformations developed in the magnesian stone have been described in relation to its phase composition. The influence of low- and high-activity crystals and calcium oxide crystals on the soundness and the structural integrity of magnesian stone has been covered.

Monitoring in situ in real time of resin infusion for thermoset composite structures

NASA Astrophysics Data System (ADS)

Faci, A.; Wang, P.; Cochrane, C.; Koncar, V.

2017-10-01

The presented work investigates changes in electrical resistance of embedded sensory yarns as a method to monitor the resin flow front position and curing degree of resin during manufacturing of composite structures by vacuum infusion technology. The sensor concept is based on Piezo-resistive sensors integrated to the flax fabric, having almost identical propriety and dimensions as the flax threads used for the production of reinforcements. In the first time sensors have been characterized and first measures of the resin infusion have been realized in order to demonstrate the feasibility of the proposed approach. Then, the measures in real time were realized with fibrous sensors added to the flax fabric (green composites) to monitor the flow front of resin. A large amount of data recorded, filtered, examined, analysed and processed in order to understand and to optimize the infusion and polymerization process.

Composite vascular scaffold combining electrospun fibers and physically-crosslinked hydrogel with copper wire-induced grooves structure.

PubMed

Liu, Yuanyuan; Jiang, Chen; Li, Shuai; Hu, Qingxi

2016-08-01

While the field of tissue engineered vascular grafts has greatly advanced, many inadequacies still exist. Successfully developed scaffolds require mechanical and structural properties that match native vessels and optimal microenvironments that foster cell integration, adhesion and growth. We have developed a small diameter, three-layered composite vascular scaffold which consists of electrospun fibers and physically-crosslinked hydrogel with copper wire-induced grooves by combining the electrospinning and dip-coating methods. Scaffold morphology and mechanics were assessed, quantified and compared to native vessels. Scaffolds were seeded with Human Umbilical Vein Endothelial Cells (HUVECs), cultured in vitro for 3 days and were evaluated for cell viability and morphology. The results showed that composite scaffolds had adjustable mechanical strength and favorable biocompatibility, which is important in the future clinical application of Tissue-engineered vascular grafts (TEVGs). Copyright © 2016 Elsevier Ltd. All rights reserved.

Development of self-powered strain sensor using mechano-luminescent ZnS:Cu and mechano-optoelectronic P3HT

NASA Astrophysics Data System (ADS)

Pulliam, Elias; Hoover, George; Tiparti, Dhruv; Ryu, Donghyeon

2017-04-01

Aerospace structural systems are prone to structural damage during their use by vibration, impact, material degradation, and other factors. Due to the harsh environments in which aerospace structures operate, aerospace structures are susceptible to various types of damage and often their structural integrity is jeopardized unless damage onset is detected in timely manner. Yet, current state-of-the-art sensor technologies are still limited for structural health monitoring (SHM) of aerospace structures due to their high power consumption, need for large form factor design, and manageable integration into aerospace structures. This study proposes a design of multilayered self-powered strain sensor by coupling mechano-luminescent (ML) property of copper-doped zinc sulfide (ZnS:Cu) and mechano-optoelectronic (MO) property of poly(3-hexylthiophene) (P3HT). One functional layer of the self-powered strain sensor is ZnS:Cu-based elastomeric composites that emit light in response to mechanical deformation. Another functional layer is P3HT-based thin films that generate direct current (DC) under light illumination and DC magnitude changes with applied strain. First, ML light emission characteristics of ZnS:Cu-based composites are studied under cyclic tensile strain with two various maximum strain up to 10% and 15% at various loading frequencies from 5 Hz to 20 Hz. Second, piezo-optical properties of P3HT-based thin films are investigated by acquiring light absorption of the thin films at various strains from 0% to 2% tensile strain. Last, micro-mechanical properties of the P3HT-based thin films are characterized using nanoindentation.

Evaluation of the potential application of three different biomaterials combined with bone morphological proteins for enhancing tendon-bone integration.

PubMed

Pan, Weimin; Cao, Zheng; Li, Dan; Zhang, Mingjun

2013-04-01

Secure tendon-bone integration is crucial for successful anterior cruciate ligament (ACL) reconstruction. Previous studies have applied different types of biomaterial or biomaterial combined with bone-growth factors to enhance tendon-bone integration. However, which approach is better remains controversial. This comparison evaluation could help identify a suitable composite biomaterial for osteointegration of grafted tendon. Three different composite biomaterials mixed with bone morphological proteins (BMPs) were fabricated. The in vitro study investigates cell metabolism, osteogenic gene expression and the growth behaviour of bone marrow stromal cells (BMSCs) on fibrin glue-BMPs (FGB), calcium phosphate cement-BMPs (CPCB) and recombined bone xenograft (RBX), which are commercially, clinically available biomaterials. Meanwhile, the changes in the physical, morphological and mechanical properties between the three composites and the original biomaterials were also observed. The in vivo study mainly examined the osteogenic ability of the three composites through rat ectopic testing. The porosity structure of three biomaterials was improved after being combined with BMPs powder for SEM observation, and the setting times of the injectable composites were not significantly delayed. More importantly, there were no significant decreases in compressive strength between the three composite biomaterials and the original biomaterials. The highest proliferation rate of BMSCs was found in the RBX group, followed by the CPCB and FGB groups. BMSCs seeded onto an RBX showed the highest alkaline phosphatase (ALPase) activity and gene expression of collagen I (P < 0.05). Histological examination showed endochondral new bone formation in the specimens of all groups, but the ALPase activity of newly formed tissue in the RBX group showed the highest level (P < 0.01). Our results indicate that RBX seems to be a very good choice for accelerating tendon-bone integration, and CPCB also has a large potential ability to be used. However, these two composites still need to be modified, and we postulate that a combination of them would be more favourable for tendon osteointegration after ACL reconstruction than either composite used alone. Copyright © 2012 Elsevier Ltd. All rights reserved.

The Magmatic Structure of Mid-ocean Ridges: Integrating Geophysical and Petrological Observations

NASA Astrophysics Data System (ADS)

Maclennan, J.; Singh, S.

Geophysical surveys, petrological observations and numerical models have all played an important role in the study of magmatic processes at mid-ocean ridges. However, few studies have attempted to integrate the constraints from both geophysical and geochemical observations in order to develop models of mid-ocean ridges. Composi- tional variation within the oceanic crust must be considered when geophysical models are interpreted in terms of variation in temperature or fluid fraction. Modellers com- monly assume that the crust is compositionally homogeneous and that the relationship between temperature and melt fraction does not vary within the crust. However, the compositions of oceanic crustal rocks collected from the Oman ophiolite vary widely and their predicted solidus temperatures vary from 990­1240C and their liquidus temperatures from 1250­1700C. Compositional variation within the solid part of the oceanic crust causes variation in seismic velocities. At fixed temperature and pressure the compositional variation present in crustal rocks can give P-wave velocity variation of 1 km s-1 or more. This has the same effect as a temperature variation of 1500C in the solid or of a variation of 20% in the melt fraction. The importance of this petrolog- ical framework for the interpretation of the seismic structure of mid-ocean ridges and for the development of thermal models of oceanic crustal accretion is demonstrated using an example from the East Pacific Rise near 9N.

SemMat: Federated Semantic Services Platform for Open materials Science and Engineering

DTIC Science & Technology

2017-01-01

identified the following two important tasks to remedy the data heterogeneity challenge to promote data integration: (1) creating the semantic...sourced from the structural and bio -materials domains. For structural materials data, we reviewed and used MIL-HDBK-5J [11] and MIL-HDBK-17. Furthermore...documents about composite materials provided by our domain expert. Based on the suggestions given by domain experts in bio -materials, the following

Impact of oxLDL on Cholesterol-Rich Membrane Rafts

PubMed Central

Levitan, Irena; Shentu, Tzu-Pin

2011-01-01

Numerous studies have demonstrated that cholesterol-rich membrane rafts play critical roles in multiple cellular functions. However, the impact of the lipoproteins on the structure, integrity and cholesterol composition of these domains is not well understood. This paper focuses on oxidized low-density lipoproteins (oxLDLs) that are strongly implicated in the development of the cardiovascular disease and whose impact on membrane cholesterol and on membrane rafts has been highly controversial. More specifically, we discuss three major criteria for the impact of oxLDL on membrane rafts: distribution of different membrane raft markers, changes in membrane cholesterol composition, and changes in lipid packing of different membrane domains. We also propose a model to reconcile the controversy regarding the relationship between oxLDL, membrane cholesterol, and the integrity of cholesterol-rich membrane domains. PMID:21490811

Operando characterization of catalysts through use of a portable microreactor

DOE PAGES

Zhao, Shen; Li, Yuanyuan; Stavitski, Eli; ...

2015-10-09

To provide new understandings of the mechanisms of catalytic reactions, improved methods are needed than can monitor changes in the electronic, structural and chemical properties of catalysts, doing so in the operando conditions in which catalysts work. We describe here a microreactor-based approach that integrates the capabilities of advanced x-ray, electron, optical and gas-phase compositional analysis techniques in operando conditions. For several exemplary catalytic systems, we demonstrate how this approach enables characterization of three major factors contributing to structure-property correlations evidenced in heterogeneously catalyzed reactions, namely: the atomic structure and elemental compositions of nanocatalysts; the physiochemical properties of the supportmore » and catalyst-support interfaces; and the gas and surface-phase chemistry occurring under operando conditions. We highlight the generality of the approach as well as outline opportunities for future developments.« less

Nanocomposites for bone tissue regeneration.

PubMed

Sahoo, Nanda Gopal; Pan, Yong Zheng; Li, Lin; He, Chao Bin

2013-04-01

Natural bone tissue possesses a nanocomposite structure that provides appropriate physical and biological properties. For bone tissue regeneration, it is crucial for the biomaterial to mimic living bone tissue. Since no single type of material is able to mimic the composition, structure and properties of native bone, nanocomposites are the best choice for bone tissue regeneration as they can provide the appropriate matrix environment, integrate desirable biological properties, and provide controlled, sequential delivery of multiple growth factors for the different stages of bone tissue regeneration. This article reviews the composition, structure and properties of advanced nanocomposites for bone tissue regeneration. It covers aspects of interest such as the biomimetic synthesis of bone-like nanocomposites, guided bone regeneration from inert biomaterials and bioactive nanocomposites, and nanocomposite scaffolds for bone tissue regeneration. The design, fabrication, and in vitro and in vivo characterization of such nanocomposites are reviewed.

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.

A database perspective of the transition from single-use (ancillary-based) systems to integrated models supporting clinical care and research in a MUMPS-based system.

PubMed

Siegel, J; Kirkland, D

1991-01-01

The Composite Health Care System (CHCS), a MUMPS-based hospital information system (HIS), has evolved from the Decentralized Hospital Computer Program (DHCP) installed within VA Hospitals. The authors explore the evolution of an ancillary-based system toward an integrated model with a look at its current state and possible future. The history and relationships between orders of different types tie specific patient-related data into a logical and temporal model. Diagrams demonstrate how the database structure has evolved to support clinical needs for integration. It is suggested that a fully integrated model is capable of meeting traditional HIS needs.

Structural tests and development of a laminar flow control wing surface composite chordwise joint

NASA Technical Reports Server (NTRS)

Lineberger, L. B.

1984-01-01

The dramatic increases in fuel costs and the potential for periods of limited fuel availability provided the impetus to explore technologies to reduce transport aircraft fuel consumption. NASA sponsored the Aircraft Energy Efficiency (ACEE) program beginning in 1976 to develop technologies to improve fuel efficiency. The Lockheed-Georgia Company accomplished under NAS1-16235 Laminar-Flow-Control (LFC) Wing Panel Structural Design and Development (WSSD); design, manufacturing, and testing activities. An in-depth preliminary design of the baseline 1993 LFC wing was accomplished. A surface panel using the Lockheed graphite/epoxy integrated LFC wing box structural concept was designed. The concept was shown by analysis to be structurally efficient and cost effective. Critical details of the surface and surface joint was demonstrated by fabricating and testing complex, concept selection specimens. The Lockheed-Georgia Company accomplishments, Development of LFC Wind Surface Composite Structures (WSCS), are documented. Tests were conducted on two CV2 panels to verify the static tension and fatigue strength of LFC wing surface chordwise joints.

ICAN: Integrated composites analyzer

NASA Technical Reports Server (NTRS)

Murthy, P. L. N.; Chamis, C. C.

1984-01-01

The ICAN computer program performs all the essential aspects of mechanics/analysis/design of multilayered fiber composites. Modular, open-ended and user friendly, the program can handle a variety of composite systems having one type of fiber and one matrix as constituents as well as intraply and interply hybrid composite systems. It can also simulate isotropic layers by considering a primary composite system with negligible fiber volume content. This feature is specifically useful in modeling thin interply matrix layers. Hygrothermal conditions and various combinations of in-plane and bending loads can also be considered. Usage of this code is illustrated with a sample input and the generated output. Some key features of output are stress concentration factors around a circular hole, locations of probable delamination, a summary of the laminate failure stress analysis, free edge stresses, microstresses and ply stress/strain influence coefficients. These features make ICAN a powerful, cost-effective tool to analyze/design fiber composite structures and components.

Multi-Scaled Modeling the Mechanical Properties of Tubular Composites Reinforced with Innovated 3D Weft Knitted Spacer Fabrics

NASA Astrophysics Data System (ADS)

Omrani, Elahe; Hasani, Hossein; Dibajian, Sayed Houssain

2018-02-01

Textile composites of 3D integrated spacer configurations have been recently focused by several researchers all over the world. In the present study, newly-designed tubular composites reinforced with 3D spacer weft knitted fabrics were considered and the effects of their structural parameters on some applicable mechanical properties were investigated. For this purpose, two different samples of 3D spacer weft knitted textile types in tubular form were produced on an electronic flat knitting machine, using glass/nylon hybrid yarns. Thermoset tubular-shaped composite parts were manufactured via vacuum infusion molding process using epoxy resin. The mechanical properties of the produced knitted composites in term of external static and internal hydrostatic pressures were evaluated. Resistance of the produced composites against the external static and internal hydrostatic pressures was numerically simulated using multi-scale modeling method. The finding revealed that there is acceptable correlation between experimental and theoretical results.

Integration of Component Knowledge in Penalized-Likelihood Reconstruction with Morphological and Spectral Uncertainties.

PubMed

Stayman, J Webster; Tilley, Steven; Siewerdsen, Jeffrey H

2014-01-01

Previous investigations [1-3] have demonstrated that integrating specific knowledge of the structure and composition of components like surgical implants, devices, and tools into a model-based reconstruction framework can improve image quality and allow for potential exposure reductions in CT. Using device knowledge in practice is complicated by uncertainties in the exact shape of components and their particular material composition. Such unknowns in the morphology and attenuation properties lead to errors in the forward model that limit the utility of component integration. In this work, a methodology is presented to accommodate both uncertainties in shape as well as unknown energy-dependent attenuation properties of the surgical devices. This work leverages the so-called known-component reconstruction (KCR) framework [1] with a generalized deformable registration operator and modifications to accommodate a spectral transfer function in the component model. Moreover, since this framework decomposes the object into separate background anatomy and "known" component factors, a mixed fidelity forward model can be adopted so that measurements associated with projections through the surgical devices can be modeled with much greater accuracy. A deformable KCR (dKCR) approach using the mixed fidelity model is introduced and applied to a flexible wire component with unknown structure and composition. Image quality advantages of dKCR over traditional reconstruction methods are illustrated in cone-beam CT (CBCT) data acquired on a testbench emulating a 3D-guided needle biopsy procedure - i.e., a deformable component (needle) with strong energy-dependent attenuation characteristics (steel) within a complex soft-tissue background.

In Vitro Maturation and In Vivo Integration and Function of an Engineered Cell-Seeded Disc-like Angle Ply Structure (DAPS) for Total Disc Arthroplasty.

PubMed

Martin, J T; Gullbrand, S E; Kim, D H; Ikuta, K; Pfeifer, C G; Ashinsky, B G; Smith, L J; Elliott, D M; Smith, H E; Mauck, R L

2017-11-17

Total disc replacement with an engineered substitute is a promising avenue for treating advanced intervertebral disc disease. Toward this goal, we developed cell-seeded disc-like angle ply structures (DAPS) and showed through in vitro studies that these constructs mature to match native disc composition, structure, and function with long-term culture. We then evaluated DAPS performance in an in vivo rat model of total disc replacement; over 5 weeks in vivo, DAPS maintained their structure, prevented intervertebral bony fusion, and matched native disc mechanical function at physiologic loads in situ. However, DAPS rapidly lost proteoglycan post-implantation and did not integrate into adjacent vertebrae. To address this, we modified the design to include polymer endplates to interface the DAPS with adjacent vertebrae, and showed that this modification mitigated in vivo proteoglycan loss while maintaining mechanical function and promoting integration. Together, these data demonstrate that cell-seeded engineered discs can replicate many characteristics of the native disc and are a viable option for total disc arthroplasty.

A data-driven approach of load monitoring on laminated composite plates using support vector machine

NASA Astrophysics Data System (ADS)

Gwon, Y. S.; Fekrmandi, H.

2018-03-01

In this study, the surface response to excitation method (SuRE) is investigated using a data-driven method for load monitoring on a laminated composite plate structure. The SuRE method is an emerging approach in ultrasonic wavebased structural health monitoring (SHM) field. In this method, a range of high-frequency, surface-guided waves are excited on the structure using piezoceramic elements. The waves propagate on the structure and interact with internal or surface damages. Initially, a baseline data of the intact structure is created by measuring the frequency transfer function between the excitation and sensing point. The integrity of structure is evaluated by monitoring changes in the frequency spectrums. The SuRE method has effectively been used for a variety of SHM applications including the detection of loose bolts, delamination in composite structures, internal corrosion in pipelines, and load and impact monitoring. Data obtained using the SuRE method was used for identifying the location of the applied load on a laminated composite plate using Support Vector Machine (SVM). A set of two piezoelectric elements were attached on the surface of the plate. A sweep excitation (150-250 kHz) generated surface-guided waves, and the transmitted waves were monitored at the sensory positions. The reference data set was measured simultaneously from the sensors. The plate was subjected to static loads while health monitoring data was being captured using the SuRE method. The confusion matrix indicated that the model classified correctly with up to 99.8% accuracy.

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

Multifunctional structural energy storage composite supercapacitors.

PubMed

Shirshova, Natasha; Qian, Hui; Houllé, Matthieu; Steinke, Joachim H G; Kucernak, Anthony R J; Fontana, Quentin P V; Greenhalgh, Emile S; Bismarck, Alexander; Shaffer, Milo S P

2014-01-01

This paper addresses the challenge of producing multifunctional composites that can simultaneously carry mechanical loads whilst storing (and delivering) electrical energy. The embodiment is a structural supercapacitor built around laminated structural carbon fibre (CF) fabrics. Each cell consists of two modified structural CF fabric electrodes, separated by a structural glass fibre fabric or polymer membrane, infused with a multifunctional polymeric electrolyte. Rather than using conventional activated carbon fibres, structural carbon fibres were treated to produce a mechanically robust, high surface area material, using a variety of methods, including direct etching, carbon nanotube sizing, and carbon nanotube in situ growth. One of the most promising approaches is to integrate a porous bicontinuous monolithic carbon aerogel (CAG) throughout the matrix. This nanostructured matrix both provides a dramatic increase in active surface area of the electrodes, and has the potential to address mechanical issues associated with matrix-dominated failures. The effect of the initial reaction mixture composition is assessed for both the CAG modified carbon fibre electrodes and resulting devices. A low temperature CAG modification of carbon fibres was evaluated using poly(3,4-ethylenedioxythiophene) (PEDOT) to enhance the electrochemical performance. For the multifunctional structural electrolyte, simple crosslinked gels have been replaced with bicontinuous structural epoxy-ionic liquid hybrids that offer a much better balance between the conflicting demands of rigidity and molecular motion. The formation of both aerogel precursors and the multifunctional electrolyte are described, including the influence of key components, and the defining characteristics of the products. Working structural supercapacitor composite prototypes have been produced and characterised electrochemically. The effect of introducing the necessary multifunctional resin on the mechanical properties has also been assessed. Larger scale demonstrators have been produced including a full size car boot/trunk lid.

Physiological and Transcriptional Responses of Saccharomyces cerevisiae to d-Limonene Show Changes to the Cell Wall but Not to the Plasma Membrane

PubMed Central

Brennan, Timothy C. R.; Nielsen, Lars K.

2013-01-01

Monoterpenes can, upon hydrogenation, be used as light-fraction components of sustainable aviation fuels. Fermentative production of monoterpenes in engineered microorganisms, such as Saccharomyces cerevisiae, has gained attention as a potential route to deliver these next-generation fuels from renewable biomass. However, end product toxicity presents a formidable problem for microbial synthesis. Due to their hydrophobicity, monoterpene inhibition has long been attributed to membrane interference, but the molecular mechanism remains largely unsolved. In order to gain a better understanding of the mode of action, we analyzed the composition and structural integrity of the cell envelope as well as the transcriptional response of yeast cells treated with an inhibitory amount of d-limonene (107 mg/liter). We found no alterations in membrane fluidity, structural membrane integrity, or fatty acid composition after the solvent challenge. A 4-fold increase in the mean fluorescence intensity per cell (using calcofluor white stain) and increased sensitivity to cell wall-degrading enzymes demonstrated that limonene disrupts cell wall properties. Global transcript measurements confirmed the membrane integrity observations by showing no upregulation of ergosterol or fatty acid biosynthesis pathways, which are commonly overexpressed in yeast to reinforce membrane rigidity during ethanol exposure. Limonene shock did cause a compensatory response to cell wall damage through overexpression of several genes (ROM1, RLM1, PIR3, CTT1, YGP1, MLP1, PST1, and CWP1) involved with the cell wall integrity signaling pathway. This is the first report demonstrating that cell wall, rather than plasma membrane, deterioration is the main source of monoterpene inhibition. We show that limonene can alter the structure and function of the cell wall, which has a clear effect on cytokinesis. PMID:23542628

Hemocompatible polyethersulfone/polyurethane composite membrane for high-performance antifouling and antithrombotic dialyzer.

PubMed

Yin, Zehua; Cheng, Chong; Qin, Hui; Nie, Chuanxiong; He, Chao; Zhao, Changsheng

2015-01-01

Researches on blood purification membranes are fuelled by diverse clinical needs, such as hemodialysis, hemodiafiltration, hemofiltration, plasmapheresis, and plasma collection. To approach high-performance dialyzer, the integrated antifouling and antithrombotic properties are highly necessary for the design/modification of advanced artificial membranes. In this study, we propose and demonstrate that the physical blend of triblock polyurethane (PU) and polyethersulfone (PES) may advance the performance of hemodialysis membranes with greatly enhanced blood compatibility. It was found that the triblock PU could be blended with PES at high ratio owing to their excellent miscibility. The surfaces of the PES/PU composite membranes were characterized using attenuated total reflectance-Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, water contact angle measurement, and surface ζ-potentials. The results indicated that the membrane surfaces were assembled with hydrophilic segregation layer owing to the migration of amphiphilic PU segments during membrane preparation, which might confer the composite membranes with superior hemocompatibility. The cross-section scanning electron microscopy images of the composite membranes exhibited structure transformation from finger-like structure to sponge-like structure, which indicated that the composite membrane had tunable porosity and permeability. The further ultrafiltration experiments indicated that the composite membranes showed increased permeability and excellent antifouling ability. The blood compatibility observation indicated that PES/PU composite membranes owned decreased protein adsorption, suppressed platelet adhesion, and prolonged plasma recalcification time. These results indicated that the PES/PU composite membranes exhibited enhanced antifouling and antithrombotic properties than the pristine PES membrane. The strategy may forward the fabrication of blood compatible composite membranes for clinical blood dialysis by using the various functional miscible polymers. © 2014 Wiley Periodicals, Inc.

Nanostructured carbon-metal oxide composite electrodes for supercapacitors: a review

NASA Astrophysics Data System (ADS)

Zhi, Mingjia; Xiang, Chengcheng; Li, Jiangtian; Li, Ming; Wu, Nianqiang

2012-12-01

This paper presents a review of the research progress in the carbon-metal oxide composites for supercapacitor electrodes. In the past decade, various carbon-metal oxide composite electrodes have been developed by integrating metal oxides into different carbon nanostructures including zero-dimensional carbon nanoparticles, one-dimensional nanostructures (carbon nanotubes and carbon nanofibers), two-dimensional nanosheets (graphene and reduced graphene oxides) as well as three-dimensional porous carbon nano-architectures. This paper has described the constituent, the structure and the properties of the carbon-metal oxide composites. An emphasis is placed on the synergistic effects of the composite on the performance of supercapacitors in terms of specific capacitance, energy density, power density, rate capability and cyclic stability. This paper has also discussed the physico-chemical processes such as charge transport, ion diffusion and redox reactions involved in supercapacitors.

Nanostructured carbon-metal oxide composite electrodes for supercapacitors: a review.

PubMed

Zhi, Mingjia; Xiang, Chengcheng; Li, Jiangtian; Li, Ming; Wu, Nianqiang

2013-01-07

This paper presents a review of the research progress in the carbon-metal oxide composites for supercapacitor electrodes. In the past decade, various carbon-metal oxide composite electrodes have been developed by integrating metal oxides into different carbon nanostructures including zero-dimensional carbon nanoparticles, one-dimensional nanostructures (carbon nanotubes and carbon nanofibers), two-dimensional nanosheets (graphene and reduced graphene oxides) as well as three-dimensional porous carbon nano-architectures. This paper has described the constituent, the structure and the properties of the carbon-metal oxide composites. An emphasis is placed on the synergistic effects of the composite on the performance of supercapacitors in terms of specific capacitance, energy density, power density, rate capability and cyclic stability. This paper has also discussed the physico-chemical processes such as charge transport, ion diffusion and redox reactions involved in supercapacitors.

A study on flexural and water absorption of surface modified rice husk flour/E-glass/polypropylene hybrid composite

NASA Astrophysics Data System (ADS)

Rassiah, K.; Sin, T. W.; Ismail, M. Z.

2016-10-01

This work is to study the effects of rice husk (RH)/E-Glass (EG)/polypropylene (PP) hybrid composites in terms of flexural and water absorption properties. The tests conducted are the flexural test and also the water absorption test using two types of water: distilled and sea water. The hybrid composites are prepared with various ratios of fibre weight fractions and the rice husk is treated using 2% Sodium Hydroxide (NaOH) to improve interaction and adhesion between the non-polar matrix and the polar lignocellulosic fibres. It was found that the content of rice husk/E-Glass fillers affected the structural integrity and flexural properties of hybrid composites. In addition, a higher ratio of rice husk contributes to higher water absorption in the hybrid composites.

Acoustic-sensor-based detection of damage in composite aircraft structures

NASA Astrophysics Data System (ADS)

Foote, Peter; Martin, Tony; Read, Ian

2004-03-01

Acoustic emission detection is a well-established method of locating and monitoring crack development in metal structures. The technique has been adapted to test facilities for non-destructive testing applications. Deployment as an operational or on-line automated damage detection technology in vehicles is posing greater challenges. A clear requirement of potential end-users of such systems is a level of automation capable of delivering low-level diagnosis information. The output from the system is in the form of "go", "no-go" indications of structural integrity or immediate maintenance actions. This level of automation requires significant data reduction and processing. This paper describes recent trials of acoustic emission detection technology for the diagnosis of damage in composite aerospace structures. The technology comprises low profile detection sensors using piezo electric wafers encapsulated in polymer film ad optical sensors. Sensors are bonded to the structure"s surface and enable acoustic events from the loaded structure to be located by triangulation. Instrumentation has been enveloped to capture and parameterise the sensor data in a form suitable for low-bandwidth storage and transmission.

Structures Containing Polyphosphate in Micrococcus lysodeikticus1

PubMed Central

Friedberg, Ilan; Avigad, Gad

1968-01-01

Granular structures containing inorganic polyphosphate were found in Micrococcus lysodeikticus. These structures were isolated by fractionation of the bacterial extract obtained by lysing the organisms with lysozyme. The composition of the fraction which was enriched with these structures was found to be: protein, 24%; lipids, 30%; and polyphosphate, 27%. This fraction also contained small amounts of ribonucleic acids, carbohydrate, and polyvalent cations. The effect of different reagents and enzymes on the integrity of the granules was examined. It was noticed that they accumulate in the bacteria during the logarithmic phase of growth but disappear gradually during the stationary phase. Images PMID:5674060

Computer modeling of the mechanical behavior of composites -- Interfacial cracks in fiber-reinforced materials

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

Schmauder, S.; Haake, S.; Mueller, W.H.

Computer modeling of materials and especially modeling the mechanical behavior of composites became increasingly popular in the past few years. Among them are examples of micromechanical modeling of real structures as well as idealized model structures of linear elastic and elasto-plastic material response. In this paper, Erdogan`s Integral Equation Method (IEM) is chosen as an example for a powerful method providing principle insight into elastic fracture mechanical situations. IEM or, alternatively, complex function techniques sometimes even allow for deriving analytical solutions such as in the case of a circumferential crack along a fiber/matrix interface. The analytical formulae of this interfacemore » crack will be analyzed numerically and typical results will be presented graphically.« less

The Ecology of Seamounts: Structure, Function, and Human Impacts

NASA Astrophysics Data System (ADS)

Clark, Malcolm R.; Rowden, Ashley A.; Schlacher, Thomas; Williams, Alan; Consalvey, Mireille; Stocks, Karen I.; Rogers, Alex D.; O'Hara, Timothy D.; White, Martin; Shank, Timothy M.; Hall-Spencer, Jason M.

2010-01-01

In this review of seamount ecology, we address a number of key scientific issues concerning the structure and function of benthic communities, human impacts, and seamount management and conservation. We consider whether community composition and diversity differ between seamounts and continental slopes, how important dispersal capabilities are in seamount connectivity, what environmental factors drive species composition and diversity, whether seamounts are centers of enhanced biological productivity, and whether they have unique trophic architecture. We discuss how vulnerable seamount communities are to fishing and mining, and how we can balance exploitation of resources and conservation of habitat. Despite considerable advances in recent years, there remain many questions about seamount ecosystems that need closer integration of molecular, oceanographic, and ecological research.

A computerized symbolic integration technique for development of triangular and quadrilateral composite shallow-shell finite elements

NASA Technical Reports Server (NTRS)

Anderson, C. M.; Noor, A. K.

1975-01-01

Computerized symbolic integration was used in conjunction with group-theoretic techniques to obtain analytic expressions for the stiffness, geometric stiffness, consistent mass, and consistent load matrices of composite shallow shell structural elements. The elements are shear flexible and have variable curvature. A stiffness (displacement) formulation was used with the fundamental unknowns consisting of both the displacement and rotation components of the reference surface of the shell. The triangular elements have six and ten nodes; the quadrilateral elements have four and eight nodes and can have internal degrees of freedom associated with displacement modes which vanish along the edges of the element (bubble modes). The stiffness, geometric stiffness, consistent mass, and consistent load coefficients are expressed as linear combinations of integrals (over the element domain) whose integrands are products of shape functions and their derivatives. The evaluation of the elemental matrices is divided into two separate problems - determination of the coefficients in the linear combination and evaluation of the integrals. The integrals are performed symbolically by using the symbolic-and-algebraic-manipulation language MACSYMA. The efficiency of using symbolic integration in the element development is demonstrated by comparing the number of floating-point arithmetic operations required in this approach with those required by a commonly used numerical quadrature technique.

Structural characterisation of medically relevant protein assemblies by integrating mass spectrometry with computational modelling.

PubMed

Politis, Argyris; Schmidt, Carla

2018-03-20

Structural mass spectrometry with its various techniques is a powerful tool for the structural elucidation of medically relevant protein assemblies. It delivers information on the composition, stoichiometries, interactions and topologies of these assemblies. Most importantly it can deal with heterogeneous mixtures and assemblies which makes it universal among the conventional structural techniques. In this review we summarise recent advances and challenges in structural mass spectrometric techniques. We describe how the combination of the different mass spectrometry-based methods with computational strategies enable structural models at molecular levels of resolution. These models hold significant potential for helping us in characterizing the function of protein assemblies related to human health and disease. In this review we summarise the techniques of structural mass spectrometry often applied when studying protein-ligand complexes. We exemplify these techniques through recent examples from literature that helped in the understanding of medically relevant protein assemblies. We further provide a detailed introduction into various computational approaches that can be integrated with these mass spectrometric techniques. Last but not least we discuss case studies that integrated mass spectrometry and computational modelling approaches and yielded models of medically important protein assembly states such as fibrils and amyloids. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

On Line Service Composition in the Integrated Clinical Environment for eHealth and Medical Systems

PubMed Central

García-Valls, Marisol; Touahria, Imad Eddine

2017-01-01

Medical and eHealth systems are progressively realized in the context of standardized architectures that support safety and ease the integration of the heterogeneous (and often proprietary) medical devices and sensors. The Integrated Clinical Environment (ICE) architecture appeared recently with the goal of becoming a common framework for defining the structure of the medical applications as concerns the safe integration of medical devices and sensors. ICE is simply a high level architecture that defines the functional blocks that should be part of a medical system to support interoperability. As a result, the underlying communication backbone is broadly undefined as concerns the enabling software technology (including the middleware) and associated algorithms that meet the ICE requirements of the flexible integration of medical devices and services. Supporting the on line composition of services in a medical system is also not part of ICE; however, supporting this behavior would enable flexible orchestration of functions (e.g., addition and/or removal of services and medical equipment) on the fly. iLandis one of the few software technologies that supports on line service composition and reconfiguration, ensuring time-bounded transitions across different service orchestrations; it supports the design, deployment and on line reconfiguration of applications, which this paper applies to service-based eHealth domains. This paper designs the integration between ICE architecture and iLand middleware to enhance the capabilities of ICE with on line service composition and the time-bounded reconfiguration of medical systems based on distributed services. A prototype implementation of a service-based eHealth system for the remote monitoring of patients is described; it validates the enhanced capacity of ICE to support dynamic reconfiguration of the application services. Results show that the temporal cost of the on line reconfiguration of the eHealth application is bounded, achieving a low overhead resulting from the addition of ICE compliance. PMID:28594371

On Line Service Composition in the Integrated Clinical Environment for eHealth and Medical Systems.

PubMed

García-Valls, Marisol; Touahria, Imad Eddine

2017-06-08

Medical and eHealth systems are progressively realized in the context of standardized architectures that support safety and ease the integration of the heterogeneous (and often proprietary) medical devices and sensors. The Integrated Clinical Environment (ICE) architecture appeared recently with the goal of becoming a common framework for defining the structure of the medical applications as concerns the safe integration of medical devices and sensors. ICE is simply a high level architecture that defines the functional blocks that should be part of a medical system to support interoperability. As a result, the underlying communication backbone is broadly undefined as concerns the enabling software technology (including the middleware) and associated algorithms that meet the ICE requirements of the flexible integration of medical devices and services. Supporting the on line composition of services in a medical system is also not part of ICE; however, supporting this behavior would enable flexible orchestration of functions (e.g., addition and/or removal of services and medical equipment) on the fly. iLandis one of the few software technologies that supports on line service composition and reconfiguration, ensuring time-bounded transitions across different service orchestrations; it supports the design, deployment and on line reconfiguration of applications, which this paper applies to service-based eHealth domains. This paper designs the integration between ICE architecture and iLand middleware to enhance the capabilities of ICE with on line service composition and the time-bounded reconfiguration of medical systems based on distributed services. A prototype implementation of a service-based eHealth system for the remote monitoring of patients is described; it validates the enhanced capacity of ICE to support dynamic reconfiguration of the application services. Results show that the temporal cost of the on line reconfiguration of the eHealth application is bounded, achieving a low overhead resulting from the addition of ICE compliance.

Crash-Energy Absorbing Composite Structure and Method of Fabrication

NASA Technical Reports Server (NTRS)

Kellas, Sotiris (Inventor); Carden, Huey D. (Inventor)

1998-01-01

A stand-alone, crash-energy absorbing structure and fabrication method are provided. A plurality of adjoining rigid cells are each constructed of resin-cured fiber reinforcement and are arranged in a geometric configuration. The geometric configuration of cells is integrated by means of continuous fibers wrapped thereabout in order to maintain the cells in the geometric configuration. The cured part results in a net shape, stable structure that can function on its own with no additional reinforcement and can withstand combined loading while crushing in a desired direction.

Computer design of porous active materials at different dimensional scales

NASA Astrophysics Data System (ADS)

Nasedkin, Andrey

2017-12-01

The paper presents a mathematical and computer modeling of effective properties of porous piezoelectric materials of three types: with ordinary porosity, with metallized pore surfaces, and with nanoscale porosity structure. The described integrated approach includes the effective moduli method of composite mechanics, simulation of representative volumes, and finite element method.

Chondriotin sulfate disaccharides as a bioactive compound modified the murine gut microbiome under healthy and stressed conditions

USDA-ARS?s Scientific Manuscript database

Chondriotin sulfate (CS) has been widely used for medical and nutraceutical purposes due to its roles in maintaining tissue structural integrity. We investigated if CS disaccharides may act as a bioactive compound and modulate gut microbial composition in mice. Our data show that CS disaccharides su...

Chapter 1: Fire and nonnative invasive plants-introduction

Treesearch

Jane Kapler Smith; Kristin Zouhar; Steve Sutherland; Matthew L. Brooks

2008-01-01

Fire is a process integral to the functioning of most temperate wildland ecosystems. Lightning-caused and anthropogenic fires have influenced the vegetation of North America profoundly for millennia (Brown and Smith 2000; Pyne 1982b). In some cases, fire has been used to manipulate the species composition and structure of ecosystems to meet management objectives,...

Models, Databases, and Simulation Tools Needed for the Realization of Integrated Computational Materials Engineering. Proceedings of the Symposium Held at Materials Science and Technology 2010

NASA Technical Reports Server (NTRS)

Arnold, Steven M. (Editor); Wong, Terry T. (Editor)

2011-01-01

Topics covered include: An Annotative Review of Multiscale Modeling and its Application to Scales Inherent in the Field of ICME; and A Multiscale, Nonlinear, Modeling Framework Enabling the Design and Analysis of Composite Materials and Structures.

Light weight polymer matrix composite material

NASA Technical Reports Server (NTRS)

Bowles, Kenneth J. (Inventor); Lowell, Carl E. (Inventor)

1991-01-01

A graphite fiber reinforced polymer matrix is layed up, cured, and thermally aged at about 750.degree. F. in the presence of an inert gas. The heat treatment improves the structural integrity and alters the electrical conductivity of the materials. In the preferred embodiment PMR-15 polyimides and Celion-6000 graphite fibers are used.

Effect of Prior Aging on Fatigue Behavior of IM7/BMI 5250-4 Composite at 191 C

DTIC Science & Technology

2007-06-01

6 Figure 4. Three stages of fatigue life cycle for general material ....................................... 9 Figure 5...calibration ........ 24 vii Figure 17. Omega thermocouple reader setup .................................................................. 26 Figure...cost and fleet readiness. To assure long- term durability and structural integrity of HTPMC components, reliable experimentally- based life -prediction

Energy-dissipating and self-repairing SMA-ECC composite material system

NASA Astrophysics Data System (ADS)

Li, Xiaopeng; Li, Mo; Song, Gangbing

2015-02-01

Structural component ductility and energy dissipation capacity are crucial factors for achieving reinforced concrete structures more resistant to dynamic loading such as earthquakes. Furthermore, limiting post-event residual damage and deformation allows for immediate re-operation or minimal repairs. These desirable characteristics for structural ‘resilience’, however, present significant challenges due to the brittle nature of concrete, its deformation incompatibility with ductile steel, and the plastic yielding of steel reinforcement. Here, we developed a new composite material system that integrates the unique ductile feature of engineered cementitious composites (ECC) with superelastic shape memory alloy (SMA). In contrast to steel reinforced concrete (RC) and SMA reinforced concrete (SMA-RC), the SMA-ECC beams studied in this research exhibited extraordinary energy dissipation capacity, minimal residual deformation, and full self-recovery of damage under cyclic flexural loading. We found that the tensile strain capacity of ECC, tailored up to 5.5% in this study, allows it to work compatibly with superelastic SMA. Furthermore, the distributed microcracking damage mechanism in ECC is critical for sufficient and reliable recovery of damage upon unloading. This research demonstrates the potential of SMA-ECC for improving resilience of concrete structures under extreme hazard events.

Damage Detection in Composite Structures with Wavenumber Array Data Processing

NASA Technical Reports Server (NTRS)

Tian, Zhenhua; Leckey, Cara; Yu, Lingyu

2013-01-01

Guided ultrasonic waves (GUW) have the potential to be an efficient and cost-effective method for rapid damage detection and quantification of large structures. Attractive features include sensitivity to a variety of damage types and the capability of traveling relatively long distances. They have proven to be an efficient approach for crack detection and localization in isotropic materials. However, techniques must be pushed beyond isotropic materials in order to be valid for composite aircraft components. This paper presents our study on GUW propagation and interaction with delamination damage in composite structures using wavenumber array data processing, together with advanced wave propagation simulations. Parallel elastodynamic finite integration technique (EFIT) is used for the example simulations. Multi-dimensional Fourier transform is used to convert time-space wavefield data into frequency-wavenumber domain. Wave propagation in the wavenumber-frequency domain shows clear distinction among the guided wave modes that are present. This allows for extracting a guided wave mode through filtering and reconstruction techniques. Presence of delamination causes spectral change accordingly. Results from 3D CFRP guided wave simulations with delamination damage in flat-plate specimens are used for wave interaction with structural defect study.

Performance characterization of active fiber-composite actuators for helicopter rotor blade applications

NASA Astrophysics Data System (ADS)

Wickramasinghe, Viresh K.; Hagood, Nesbitt W.

2002-07-01

The primary objective of this work was to characterize the performance of the Active Fiber Composite (AFC) actuator material system for the Boeing Active Material Rotor (AMR) blade application. The AFCs were a new structural actuator system consisting of piezoceramic fibers embedded in an epoxy matrix and sandwiched between interdigitated electrodes to orient the driving electric field in the fiber direction to use the primary piezoelectric effect. These actuators were integrated directly into the blade spar laminate as active plies within the composite structure to perform structural actuation for vibration control in helicopters. Therefore, it was necessary to conduct extensive electromechanical material characterization to evaluate AFCs both as actuators and as structural components of the rotor blade. The characterization tests designed to extract important electromechanical properties under simulated blade operating conditions included stress-strain tests, free strain tests and actuation under tensile load tests. This paper presents the test results as well as the comprehensive testing process developed to evaluate the relevant AFC material properties. The results from this comprehensive performance characterization of the AFC material system supported the design and operation of the Boeing AMR blade scheduled for hover and forward flight wind tunnel tests.

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

Nanotechnology: MEMS and NEMS and their applications to smart systems and devices

NASA Astrophysics Data System (ADS)

Varadan, Vijay K.

2003-10-01

The microelectronics industry has seen explosive growth during the last thirty years. Extremely large markets for logic and memory devices have driven the development of new materials, and technologies for the fabrication of even more complex devices with features sizes now down at the sub micron and nanometer level. Recent interest has arisen in employing these materials, tools and technologies for the fabrication of miniature sensors and actuators and their integration with electronic circuits to produce smart devices and systems. This effort offers the promise of: (1) increasing the performance and manufacturability of both sensors and actuators by exploiting new batch fabrication processes developed including micro stereo lithographic and micro molding techniques; (2) developing novel classes of materials and mechanical structures not possible previously, such as diamond like carbon, silicon carbide and carbon nanotubes, micro-turbines and micro-engines; (3) development of technologies for the system level and wafer level integration of micro components at the nanometer precision, such as self-assembly techniques and robotic manipulation; (4) development of control and communication systems for MEMS devices, such as optical and RF wireless, and power delivery systems, etc. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross-linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composite provide a new avenue for future smart systems. The integration of NEMS (NanoElectroMechanical Systems), MEMS, IDTs (Interdigital Transducers) and required microelectronics and conformal antenna in the multifunctional smart materials and composites results in a smart system suitable for sending and control of a variety functions in automobile, aerospace, marine and civil strutures and food and medical industries. This unique combination of technologies also results in novel conformal sensors that can be remotely sensed by an antenna system with the advantage of no power requirements at the sensor site. This paper provides a brief review of MEMS and NEMS based smart systems for various applications mentioned above. Carbon Nano Tubes (CNT) with their unique structure, have already proven to be valuable in their application as tips for scanning probe microscopy, field emission devices, nanoelectronics, H2-storage, electromagnetic absorbers, ESD, EMI films and coatings and structural composites. For many of these applications, highly purified and functionalized CNT which are compatible with many host polymers are needed. A novel microwave CVD processing technique to meet these requirements has been developed at Penn State Center for the Engineering of Electronic and Acoustic Materials and Devices (CEEAMD). This method enables the production of highly purified carbon nano tubes with variable size (from 5 - 40 nm) at low cost (per gram) and high yield. Whereas, carbon nano tubes synthesized using the laser ablation or arc discharge evaporation method always include impurity due to catalyst or catalyst support. The Penn State research is based on the use of zeolites over other metal/metal oxides in the microwave field for a high production and uniformity of the product. An extended coventional purification method has been employed to purify our products in order to remove left over impurity. A novel composite structure can be tailored by functionalizing carbon nano tubes and chemically bonding them with the polymer matrix e.g. block or graft copolymer, or even cross-linked copolymer, to impart exceptional structural, electronic and surface properties. Bio- and Mechanical-MEMS devices derived from this hybrid composites will be presented.

[Mechanical properties of polylactic acid/beta-tricalcium phosphate composite scaffold with double channels based on three-dimensional printing technique].

PubMed

Lian, Qin; Zhuang, Pei; Li, Changhai; Jin, Zhongmin; Li, Dichen

2014-03-01

To improve the poor mechanical strength of porous ceramic scaffold, an integrated method based on three-dimensional (3-D) printing technique is developed to incorporate the controlled double-channel porous structure into the polylactic acid/beta-tricalcium phosphate (PLA/beta-TCP) reinforced composite scaffolds (double-channel composite scaffold) to improve their tissue regeneration capability and the mechanical properties. The designed double-channel structure inside the ceramic scaffold consisted of both primary and secondary micropipes, which parallel but un-connected. The set of primary channels was used for cell ingrowth, while the set of secondary channels was used for the PLA perfusion. Integration technology of 3-D printing technique and gel-casting was firstly used to fabricate the double-channel ceramic scaffolds. PLA/beta-TCP composite scaffolds were obtained by the polymer gravity perfusion process to pour PLA solution into the double-channel ceramic scaffolds through the secondary channel set. Microscope, porosity, and mechanical experiments for the standard samples were used to evaluate the composite properties. The ceramic scaffold with only the primary channel (single-channel scaffold) was also prepared as a control. Morphology observation results showed that there was no PLA inside the primary channels of the double-channel composite scaffolds but a dense interface layer between PLA and beta-TCP obviously formed on the inner wall of the secondary channels by the PLA penetration during the perfusion process. Finite element simulation found that the compressive strength of the double-channel composite scaffold was less than that of the single-channel scaffold; however, mechanical tests found that the maximum compressive strength of the double-channel composite scaffold [(21.25 +/- 1.15) MPa] was higher than that of the single-channel scaffold[ (9.76 +/- 0.64) MPa]. The double-channel composite scaffolds fabricated by 3-D printing technique have controlled complex micropipes and can significantly enhance mechanical properties, which is a promising strategy to solve the contradiction of strength and high-porosity of the ceramic scaffolds for the bone tissue engineering application.

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.

Planarised optical fiber composite using flame hydrolysis deposition demonstrating an integrated FBG anemometer.

PubMed

Holmes, Christopher; Gates, James C; Smith, Peter G R

2014-12-29

This paper reports for the first time a planarised optical fiber composite formed using Flame Hydrolysis Deposition (FHD). As a way of format demonstration a Micro-Opto-Electro-Mechanical (MOEMS) hot wire anemometer is formed using micro-fabrication processing. The planarised device is rigidly secured to a silicon wafer using optical quality doped silica that has been deposited using flame hydrolysis and consolidated at high temperature. The resulting structure can withstand temperatures exceeding 580K and is sensitive enough to resolve free and forced convection interactions at low fluid velocity.

Computational Infrastructure for Engine Structural Performance Simulation

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1997-01-01

Select computer codes developed over the years to simulate specific aspects of engine structures are described. These codes include blade impact integrated multidisciplinary analysis and optimization, progressive structural fracture, quantification of uncertainties for structural reliability and risk, benefits estimation of new technology insertion and hierarchical simulation of engine structures made from metal matrix and ceramic matrix composites. Collectively these codes constitute a unique infrastructure readiness to credibly evaluate new and future engine structural concepts throughout the development cycle from initial concept, to design and fabrication, to service performance and maintenance and repairs, and to retirement for cause and even to possible recycling. Stated differently, they provide 'virtual' concurrent engineering for engine structures total-life-cycle-cost.

BMI Sandwich Wing Box Analysis and Test

NASA Technical Reports Server (NTRS)

Palm, Tod; Mahler, Mary; Shah, Chandu; Rouse, Marshall; Bush, Harold; Wu, Chauncey; Small, William J.

2000-01-01

A composite sandwich single bay wing box test article was developed by Northrop Grumman and tested recently at NASA Langley Research Center. The objectives for the wing box development effort were to provide a demonstration article for manufacturing scale up of structural concepts related to a high speed transport wing, and to validate the structural performance of the design. The box concept consisted of highly loaded composite sandwich wing skins, with moderately loaded composite sandwich spars. The dimensions of the box were chosen to represent a single bay of the main wing box, with a spar spacing of 30 inches, height of 20 inches constant depth, and length of 64 inches. The bismaleimide facesheet laminates and titanium honeycomb core chosen for this task are high temperature materials able to sustain a 300F service temperature. The completed test article is shown in Figure 1. The tests at NASA Langley demonstrated the structures ability to sustain axial tension and compression loads in excess of 20,000 lb/in, and to maintain integrity in the thermal environment. Test procedures, analysis failure predictions, and test results are presented.

Techniques and Applications of in vivo Diffusion Imaging of Articular Cartilage

PubMed Central

Raya, José G.

2014-01-01

Early in the process of osteoarthritis (OA) the composition (water, proteoglycan [PG], and collagen) and structure of articular cartilage is altered leading to changes in its mechanical properties. A technique that can assess the composition and structure of the cartilage in vivo can provide insight in the mechanical integrity of articular cartilage and become a powerful tool for the early diagnosis of OA. Diffusion tensor imaging (DTI) has been proposed as a biomarker for cartilage composition and structure. DTI is sensitive to the PG content through the mean diffusivity (MD) and to the collagen architecture through the fractional anisotropy (FA). However, the acquisition of DTI of articular cartilage in vivo is challenging due to the short T2 of articular cartilage (~40 ms at 3 T) and the high resolution needed (0.5–0.7 mm in plane) to depict the cartilage anatomy. We describe the pulse sequences used for in vivo DTI of articular cartilage and discus general strategies for protocol optimization. We provide a comprehensive review of measurements of DTI of articular cartilage from ex vivo validation experiments to its recent clinical applications. PMID:25865215

Accurate atomistic potentials and training sets for boron-nitride nanostructures

NASA Astrophysics Data System (ADS)

Tamblyn, Isaac

Boron nitride nanotubes exhibit exceptional structural, mechanical, and thermal properties. They are optically transparent and have high thermal stability, suggesting a wide range of opportunities for structural reinforcement of materials. Modeling can play an important role in determining the optimal approach to integrating nanotubes into a supporting matrix. Developing accurate, atomistic scale models of such nanoscale interfaces embedded within composites is challenging, however, due to the mismatch of length scales involved. Typical nanotube diameters range from 5-50 nm, with a length as large as a micron (i.e. a relevant length-scale for structural reinforcement). Unlike their carbon-based counterparts, well tested and transferable interatomic force fields are not common for BNNT. In light of this, we have developed an extensive training database of BN rich materials, under conditions relevant for BNNT synthesis and composites based on extensive first principles molecular dynamics simulations. Using this data, we have produced an artificial neural network potential capable of reproducing the accuracy of first principles data at significantly reduced computational cost, allowing for accurate simulation at the much larger length scales needed for composite design.

HIGH EFFICIENCY STRUCTURAL FLOWTHROUGH ROTOR WITH ACTIVE FLAP CONTROL: VOLUME THREE: MARKET & TEAM

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

Zuteck, Michael D.; Jackson, Kevin L.; Santos, Richard A.

The Zimitar one-piece rotor primary structure is integrated, so balanced thrust and gravity loads flow through the hub region without transferring out of its composite material. Large inner rotor geometry is used since there is no need to neck down to a blade root region and pitch bearing. Rotor control is provided by a highly redundant, five flap system on each blade, sized so that easily handled standard electric linear actuators are sufficient.

Active damage interrogation system for structural health monitoring

NASA Astrophysics Data System (ADS)

Lichtenwalner, Peter F.; Dunne, James P.; Becker, Ronald S.; Baumann, Erwin W.

1997-05-01

An integrated and automated smart structures approach for in situ damage assessment has been implemented and evaluated in a laboratory environment for health monitoring of a realistic aerospace structural component. This approach, called Active Damage Interrogation (ADI), utilizes an array of piezoelectric transducers attached to or embedded within the structure for both actuation and sensing. The ADI system, which is model independent, actively interrogates the structure through broadband excitation of multiple actuators across the desired frequency range. Statistical analysis of the changes in transfer functions between actuator/sensor pairs is used to detect, localize, and assess the severity of damage in the structure. This paper presents the overall concept of the ADI system and provides experimental results of damage assessment studies conducted for a composite structural component of the MD-900 Explorer helicopter rotor system. The potential advantages of this approach include simplicity (no need for a model), sensitivity, and low cost implementation. The results obtained thus far indicate considerably promise for integrated structural health monitoring of aerospace vehicles, leading to the practice of condition-based maintenance and consequent reduction in life cycle costs.

Capacitance-based damage detection sensing for aerospace structural composites

NASA Astrophysics Data System (ADS)

Bahrami, P.; Yamamoto, N.; Chen, Y.; Manohara, H.

2014-04-01

Damage detection technology needs improvement for aerospace engineering application because detection within complex composite structures is difficult yet critical to avoid catastrophic failure. Damage detection is challenging in aerospace structures because not all the damage detection technology can cover the various defect types (delamination, fiber fracture, matrix crack etc.), or conditions (visibility, crack length size, etc.). These defect states are expected to become even more complex with future introduction of novel composites including nano-/microparticle reinforcement. Currently, non-destructive evaluation (NDE) methods with X-ray, ultrasound, or eddy current have good resolutions (< 0.1 mm), but their detection capabilities is limited by defect locations and orientations and require massive inspection devices. System health monitoring (SHM) methods are often paired with NDE technologies to signal out sensed damage, but their data collection and analysis currently requires excessive wiring and complex signal analysis. Here, we present a capacitance sensor-based, structural defect detection technology with improved sensing capability. Thin dielectric polymer layer is integrated as part of the structure; the defect in the structure directly alters the sensing layer's capacitance, allowing full-coverage sensing capability independent of defect size, orientation or location. In this work, capacitance-based sensing capability was experimentally demonstrated with a 2D sensing layer consisting of a dielectric layer sandwiched by electrodes. These sensing layers were applied on substrate surfaces. Surface indentation damage (~1mm diameter) and its location were detected through measured capacitance changes: 1 to 250 % depending on the substrates. The damage detection sensors are light weight, and they can be conformably coated and can be part of the composite structure. Therefore it is suitable for aerospace structures such as cryogenic tanks and rocket fairings for example. The sensors can also be operating in space and harsh environment such as high temperature and vacuum.

A novel durable double-conductive core-shell structure applying to the synthesis of silicon anode for lithium ion batteries

NASA Astrophysics Data System (ADS)

Xing, Yan; Shen, Tong; Guo, Ting; Wang, Xiuli; Xia, Xinhui; Gu, Changdong; Tu, Jiangping

2018-04-01

Si/C composites are currently the most commercially viable next-generation lithium-ion battery anode materials due to their high specific capacity. However, there are still many obstacles need to be overcome such as short cycle life and poor conductivity. In this work, we design and successfully synthesis an excellent durable double-conductive core-shell structure p-Si-Ag/C composites. Interestingly, this well-designed structure offers remarkable conductivity (both internal and external) due to the introduction of silver particles and carbon layer. The carbon layer acts as a protective layer to maintain the integrity of the structure as well as avoids the direct contact of silicon with electrolyte. As a result, the durable double-conductive core-shell structure p-Si-Ag/C composites exhibit outstanding cycling stability of roughly 1000 mAh g-1 after 200 cycles at a current density of 0.2 A g-1 and retain 765 mAh g-1 even at a high current density of 2 A g-1, indicating a great improvement in electrochemical performance compared with traditional silicon electrode. Our research results provide a novel pathway for production of high-performance Si-based anodes to extending the cycle life and specific capacity of commercial lithium ion batteries.

Extending Structural Analyses of the Rosenberg Self-Esteem Scale to Consider Criterion-Related Validity: Can Composite Self-Esteem Scores Be Good Enough?

PubMed

Donnellan, M Brent; Ackerman, Robert A; Brecheen, Courtney

2016-01-01

Although the Rosenberg Self-Esteem Scale (RSES) is the most widely used measure of global self-esteem in the literature, there are ongoing disagreements about its factor structure. This methodological debate informs how the measure should be used in substantive research. Using a sample of 1,127 college students, we test the overall fit of previously specified models for the RSES, including a newly proposed bifactor solution (McKay, Boduszek, & Harvey, 2014 ). We extend previous work by evaluating how various latent factors from these structural models are related to a set of criterion variables frequently studied in the self-esteem literature. A strict unidimensional model poorly fit the data, whereas models that accounted for correlations between negatively and positively keyed items tended to fit better. However, global factors from viable structural models had similar levels of association with criterion variables and with the pattern of results obtained with a composite global self-esteem variable calculated from observed scores. Thus, we did not find compelling evidence that different structural models had substantive implications, thereby reducing (but not eliminating) concerns about the integrity of the self-esteem literature based on overall composite scores for the RSES.