Bonded repair of composite aircraft structures: A review of scientific challenges and opportunities

NASA Astrophysics Data System (ADS)

Katnam, K. B.; Da Silva, L. F. M.; Young, T. M.

2013-08-01

Advanced composite materials have gained popularity in high-performance structural designs such as aerospace applications that require lightweight components with superior mechanical properties in order to perform in demanding service conditions as well as provide energy efficiency. However, one of the major challenges that the aerospace industry faces with advanced composites - because of their inherent complex damage behaviour - is structural repair. Composite materials are primarily damaged by mechanical loads and/or environmental conditions. If material damage is not extensive, structural repair is the only feasible solution as replacing the entire component is not cost-effective in many cases. Bonded composite repairs (e.g. scarf patches) are generally preferred as they provide enhanced stress transfer mechanisms, joint efficiencies and aerodynamic performance. With an increased usage of advanced composites in primary and secondary aerospace structural components, it is thus essential to have robust, reliable and repeatable structural bonded repair procedures to restore damaged composite components. But structural bonded repairs, especially with primary structures, pose several scientific challenges with the current existing repair technologies. In this regard, the area of structural bonded repair of composites is broadly reviewed - starting from damage assessment to automation - to identify current scientific challenges and future opportunities.

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.

Composite Bus Structure for the SMEX/WIRE Satellite

NASA Technical Reports Server (NTRS)

Rosanova, Giulio G.

1998-01-01

In an effort to reduce the weight and optimize the structural design of the Small Explorer (SMEX) Wide-Field Infrared Explorer (WIRE) spacecraft, it has become desirable to change the material and construction from mechanically fastened aluminum structure to a fully bonded fiber-reinforced composite (FRC) structure. GSFC has developed the WIRE spacecraft structural bus design concept, including the instrument and launch vehicle requirements. The WIRE Satellite is the fifth of a series of SMEX satellites to be launched once per year. GSFC has chosen Composite Optics Inc. (COI) as the prime contractor for the development and procurement of the WIRE composite structure. The detailed design of the fully bonded FRC structure is based on COI's Short Notice Accelerated Production SATellite ("SNAPSAT") approach. SNAPSAT is a state of the art design and manufacturing technology for advanced composite materials which utilizes flat-stock detail parts bonded together to produce a final structural assembly. The structural design approach adopted for the WIRE structure provides a very viable alternative to both traditional aluminum construction as well as high tech. molded type composite structures. This approach to composite structure design is much less costly than molded or honeycomb sandwich type composite construction, but may cost slightly more than conventional aluminum construction on the subsystem level. However on the overall program level the weight saving achieved is very cost effective, since the primary objective is to allocate more mass for science payloads.

Technologies for Future Precision Strike Missile Systems - Missile Aeromechanics Technology

DTIC Science & Technology

2001-07-01

structure materials, composite structure materials, hypersonic insulation materials, multi-spectral domes, and reduced parts count structure. Introduction...high control effectiveness. An inherent disadvantage of a forward swept surface is increased potential for aeroelastic instability. Composite structure...is synergistic with forward swept surfaces because the higher stiffness of composites mitigates aeroelastic instability. Composite material may also

An overview of computational simulation methods for composite structures failure and life analysis

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1993-01-01

Three parallel computational simulation methods are being developed at the LeRC Structural Mechanics Branch (SMB) for composite structures failure and life analysis: progressive fracture CODSTRAN; hierarchical methods for high-temperature composites; and probabilistic evaluation. Results to date demonstrate that these methods are effective in simulating composite structures failure/life/reliability.

Shock and Impact Response of Naval Composite Structures

DTIC Science & Technology

2010-08-09

elucidating physical mechanisms that control the survivability of composite structures under blast and impact. TECHNICAL APPROACH The Principal...the Proceedings of the 16th International Conference on Composite Structures , Kyoto, Japan, July 8-13, 2007. D. ONR Solid Mechanics Program...ONR Solid Mechanics Program Review, Marine Composites and Sandwich Structures , University of Maryland University College, Adelphi, MD, September 21

Structural Composite Supercapacitors: Electrical and Mechanical Impact of Separators and Processing Conditions

DTIC Science & Technology

2013-09-01

Structural Composite Supercapacitors : Electrical and Mechanical Impact of Separators and Processing Conditions by Edwin B. Gienger, James F...Proving Ground, MD 21005-5066 ARL-TR-6624 September 2013 Structural Composite Supercapacitors : Electrical and Mechanical Impact of...2012 4. TITLE AND SUBTITLE Structural Composite Supercapacitors : Electrical and Mechanical Impact of Separators and Processing Conditions 5a

Composite Dry Structure Cost Improvement Approach

NASA Technical Reports Server (NTRS)

Nettles, Alan; Nettles, Mindy

2015-01-01

This effort demonstrates that by focusing only on properties of relevance, composite interstage and shroud structures can be placed on the Space Launch System vehicle that simultaneously reduces cost, improves reliability, and maximizes performance, thus providing the Advanced Development Group with a new methodology of how to utilize composites to reduce weight for composite structures on launch vehicles. Interstage and shroud structures were chosen since both of these structures are simple in configuration and do not experience extreme environments (such as cryogenic or hot gas temperatures) and should represent a good starting point for flying composites on a 'man-rated' vehicle. They are used as an example only. The project involves using polymer matrix composites for launch vehicle structures, and the logic and rationale behind the proposed new methodology.

Lessons learned for composite structures

NASA Technical Reports Server (NTRS)

Whitehead, R. S.

1991-01-01

Lessons learned for composite structures are presented in three technology areas: materials, manufacturing, and design. In addition, future challenges for composite structures are presented. Composite materials have long gestation periods from the developmental stage to fully matured production status. Many examples exist of unsuccessful attempts to accelerate this gestation period. Experience has shown that technology transition of a new material system to fully matured production status is time consuming, involves risk, is expensive and should not be undertaken lightly. The future challenges for composite materials require an intensification of the science based approach to material development, extension of the vendor/customer interaction process to include all engineering disciplines of the end user, reduced material costs because they are a significant factor in overall part cost, and improved batch-to-batch pre-preg physical property control. Historical manufacturing lessons learned are presented using current in-service production structure as examples. Most producibility problems for these structures can be traced to their sequential engineering design. This caused an excessive emphasis on design-to-weight and schedule at the expense of design-to-cost. This resulted in expensive performance originated designs, which required costly tooling and led to non-producible parts. Historically these problems have been allowed to persist throughout the production run. The current/future approach for the production of affordable composite structures mandates concurrent engineering design where equal emphasis is placed on product and process design. Design for simplified assembly is also emphasized, since assembly costs account for a major portion of total airframe costs. The future challenge for composite manufacturing is, therefore, to utilize concurrent engineering in conjunction with automated manufacturing techniques to build affordable composite structures. Composite design experience has shown that significant weight savings have been achieved, outstanding fatigue and corrosion resistance have been demonstrated, and in-service performance has been very successful. Currently no structural design show stoppers exist for composite structures. A major lesson learned is that the full scale static test is the key test for composites, since it is the primary structural 'hot spot' indicator. The major durability issue is supportability of thin skinned structure. Impact damage has been identified as the most significant issue for the damage tolerance control of composite structures. However, delaminations induced during assembly operations have demonstrated a significant nuisance value. The future challenges for composite structures are threefold. Firstly, composite airframe weight fraction should increase to 60 percent. At the same time, the cost of composite structures must be reduced by 50 percent to attain the goal of affordability. To support these challenges it is essential to develop lower cost materials and processes.

Method of joining metallic and composite components

NASA Technical Reports Server (NTRS)

Semmes, Edmund B. (Inventor)

2010-01-01

A method is provided for joining a metallic member to a structure made of a composite matrix material. One or more surfaces of a portion of the metallic member that is to be joined to the composite matrix structure is provided with a plurality of outwardly projecting studs. The surface including the studs is brought into engagement with a portion of an uncured composite matrix material so that fibers of the composite matrix material intertwine with the studs, and the metallic member and composite structure form an assembly. The assembly is then companion cured so as to join the metallic member to the composite matrix material structure.

Bonded and Stitched Composite Structure

NASA Technical Reports Server (NTRS)

Zalewski, Bart F. (Inventor); Dial, William B. (Inventor)

2014-01-01

A method of forming a composite structure can include providing a plurality of composite panels of material, each composite panel having a plurality of holes extending through the panel. An adhesive layer is applied to each composite panel and a adjoining layer is applied over the adhesive layer. The method also includes stitching the composite panels, adhesive layer, and adjoining layer together by passing a length of a flexible connecting element into the plurality of holes in the composite panels of material. At least the adhesive layer is cured to bond the composite panels together and thereby form the composite structure.

FIBER-TEX 1992: The Sixth Conference on Advanced Engineering Fibers and Textile Structures for Composites

NASA Technical Reports Server (NTRS)

Buckley, John D. (Editor)

1993-01-01

The FIBER-TEX 1992 proceedings contain the papers presented at the conference held on 27-29 Oct. 1992 at Drexel University. The conference was held to create a forum to encourage an interrelationship of the various disciplines involved in the fabrication of materials, the types of equipment, and the processes used in the production of advanced composite structures. Topics discussed were advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, and the latest requirements for the use of textiles in the production of composite materials and structures as related to global activities focused on textile structural composites.

Damage assessment of composite plate structures with material and measurement uncertainty

NASA Astrophysics Data System (ADS)

Chandrashekhar, M.; Ganguli, Ranjan

2016-06-01

Composite materials are very useful in structural engineering particularly in weight sensitive applications. Two different test models of the same structure made from composite materials can display very different dynamic behavior due to large uncertainties associated with composite material properties. Also, composite structures can suffer from pre-existing imperfections like delaminations, voids or cracks during fabrication. In this paper, we show that modeling and material uncertainties in composite structures can cause considerable problem in damage assessment. A recently developed C0 shear deformable locking free refined composite plate element is employed in the numerical simulations to alleviate modeling uncertainty. A qualitative estimate of the impact of modeling uncertainty on the damage detection problem is made. A robust Fuzzy Logic System (FLS) with sliding window defuzzifier is used for delamination damage detection in composite plate type structures. The FLS is designed using variations in modal frequencies due to randomness in material properties. Probabilistic analysis is performed using Monte Carlo Simulation (MCS) on a composite plate finite element model. It is demonstrated that the FLS shows excellent robustness in delamination detection at very high levels of randomness in input data.

Techno-economic requirements for composite aircraft components

NASA Technical Reports Server (NTRS)

Palmer, Ray

1993-01-01

The primary reason for use of composites is to save structural weight. A well designed composite aircraft structure will usually save 25-30 percent of a well designed metal structure. The weight savings then translates into improved performance of the aircraft in measures of greater payload, increased flying range or improved efficiency - less use of fuel. Composite materials offer technical advantages. Key technical advantages that composites offer are high stiffness, tailored strength capability, fatigue resistance, and corrosion resistance. Low thermal expansion properties produce dimensionally stable structures over a wide range of temperature. Specialty resin 'char' forming characteristics in a fire environment offer potential fire barrier application and safer aircraft. The materials and processes of composite fabrication offer the potential for lower cost structures in the near future. The application of composite materials to aircraft are discussed.

77 FR 50576 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures; OMB Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-08-22

... Composite Rotorcraft Structures; OMB Approval of Information Collection AGENCY: Federal Aviation... requirement contained in the FAA's final rule, ``Damage Tolerance and Fatigue Evaluation of Composite... and Fatigue Evaluation of Composite Rotorcraft Structures,'' published in the Federal Register (76 FR...

ACEE composite structures technology

NASA Technical Reports Server (NTRS)

Klotzsche, M. (Compiler)

1984-01-01

The NASA Aircraft Energy Efficiency (ACEE) Composite Primary Aircraft Structures Program has made significant progress in the development of technology for advanced composites in commercial aircraft. Commercial airframe manufacturers have demonstrated technology readiness and cost effectiveness of advanced composites for secondary and medium primary components and have initiated a concerted program to develop the data base required for efficient application to safety-of-flight wing and fuselage structures. Oral presentations were compiled into five papers. Topics addressed include: damage tolerance and failsafe testing of composite vertical stabilizer; optimization of composite multi-row bolted joints; large wing joint demonstation components; and joints and cutouts in fuselage structure.

Structural arrangement trade study. Volume 3: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Addendum

NASA Astrophysics Data System (ADS)

1995-03-01

This volume is the third of a 3 volume set that addresses the structural trade study plan that will identify the most suitable structural configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The most suitable Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Tank System (GCPS) composite materials for intertank, wing and thrust structures are identified. Vehicle resizing charts, selection criteria and back-up charts, parametric costing approach and the finite element method analysis are discussed.

Structural arrangement trade study. Volume 3: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Addendum

NASA Technical Reports Server (NTRS)

1995-01-01

This volume is the third of a 3 volume set that addresses the structural trade study plan that will identify the most suitable structural configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The most suitable Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Tank System (GCPS) composite materials for intertank, wing and thrust structures are identified. Vehicle resizing charts, selection criteria and back-up charts, parametric costing approach and the finite element method analysis are discussed.

FIBER-TEX 1991: The Fifth Conference on Advanced Engineering Fibers and Textile Structures for Composites

NASA Technical Reports Server (NTRS)

Buckley, John D. (Editor)

1992-01-01

This document is a compilation of papers presented at a joint NASA/North Carolina State University/DoD/Clemson University/Drexel University conference on Fibers, Textile Technology, and Composites Structures held at the College of Textiles Building on Centennial Campus of North Carolina State University, Raleigh, North Carolina on October 15-17, 1991. Conference papers presented information on advanced engineering fibers, textile processes and structures, structural fabric production, mechanics and characteristics of woven composites, pultruded composites, and the latest requirements for the use of textiles in the production of composite materials and structures.

Effect of stress concentrations in composite structures

NASA Technical Reports Server (NTRS)

Babcock, C. D.; Waas, A. M.

1985-01-01

Composite structures have found wide use in many engineering fields and a sound understanding of their response under load is important to their utilization. An experimental program is being carried out to gain a fundamental understanding of the failure mechanics of multilayered composite structures at GALCIT. As a part of this continuing study, the performance of laminated composite plates in the presence of a stress gradient and the failure of composite structures at points of thickness discontinuity is assessed. In particular, the questions of initiation of failure and its subsequent growth to complete failure of the structure are addressed.

New Robust Design Guideline forImperfection Sensitive Composite Launcher Structures- The Desicos Project

NASA Astrophysics Data System (ADS)

Degenhardt, Richard

2014-06-01

Space industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite space and aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis. Currently, the potential of composite light weight structures, which are prone to buckling, is not fully exploited as appropriate guidelines in the field of space applications do not exist. This paper deals with the state-of-the-art advances and challenges related to coupled stability analysis of composite structures which show very complex stability behaviour. Improved design guidelines for composites structures are still under development. This paper gives a short state-of-the-art and presents a proposal for a future design guideline.

Mechanical Model Development for Composite Structural Supercapacitors

NASA Technical Reports Server (NTRS)

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

2016-01-01

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

Biomimetic Structural Materials: Inspiration from Design and Assembly.

PubMed

Yaraghi, Nicholas A; Kisailus, David

2018-04-20

Nature assembles weak organic and inorganic constituents into sophisticated hierarchical structures, forming structural composites that demonstrate impressive combinations of strength and toughness. Two such composites are the nacre structure forming the inner layer of many mollusk shells, whose brick-and-mortar architecture has been the gold standard for biomimetic composites, and the cuticle forming the arthropod exoskeleton, whose helicoidal fiber-reinforced architecture has only recently attracted interest for structural biomimetics. In this review, we detail recent biomimetic efforts for the fabrication of strong and tough composite materials possessing the brick-and-mortar and helicoidal architectures. Techniques discussed for the fabrication of nacre- and cuticle-mimetic structures include freeze casting, layer-by-layer deposition, spray deposition, magnetically assisted slip casting, fiber-reinforced composite processing, additive manufacturing, and cholesteric self-assembly. Advantages and limitations to these processes are discussed, as well as the future outlook on the biomimetic landscape for structural composite materials.

Biomimetic Structural Materials: Inspiration from Design and Assembly

NASA Astrophysics Data System (ADS)

Yaraghi, Nicholas A.; Kisailus, David

2018-04-01

Nature assembles weak organic and inorganic constituents into sophisticated hierarchical structures, forming structural composites that demonstrate impressive combinations of strength and toughness. Two such composites are the nacre structure forming the inner layer of many mollusk shells, whose brick-and-mortar architecture has been the gold standard for biomimetic composites, and the cuticle forming the arthropod exoskeleton, whose helicoidal fiber-reinforced architecture has only recently attracted interest for structural biomimetics. In this review, we detail recent biomimetic efforts for the fabrication of strong and tough composite materials possessing the brick-and-mortar and helicoidal architectures. Techniques discussed for the fabrication of nacre- and cuticle-mimetic structures include freeze casting, layer-by-layer deposition, spray deposition, magnetically assisted slip casting, fiber-reinforced composite processing, additive manufacturing, and cholesteric self-assembly. Advantages and limitations to these processes are discussed, as well as the future outlook on the biomimetic landscape for structural composite materials.

Application of Ultrasonic Phased Array Technology to the Detection of Defect in Composite Stiffened-structures

NASA Astrophysics Data System (ADS)

Zhou, Yuan-Qi; Zhan, Li-Hua

2016-05-01

Composite stiffened-structure consists of the skin and stringer has been widely used in aircraft fuselage and wings. The main purpose of the article is to detect the composite material reinforced structure accurately and explore the relationship between defect formation and structural elements or curing process. Based on ultrasonic phased array inspection technology, the regularity of defects in the manufacture of composite materials are obtained, the correlation model between actual defects and nondestructive testing are established. The article find that the forming quality of deltoid area in T-stiffened structure is obviously improved by pre-curing, the defects of hat-stiffened structure are affected by the mandrel. The results show that the ultrasonic phased array inspection technology can be an effectively way for the detection of composite stiffened-structures, which become an important means to control the defects of composite and improve the quality of the product.

Composite structural materials

NASA Technical Reports Server (NTRS)

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

1981-01-01

The composite aircraft program component (CAPCOMP) is a graduate level project conducted in parallel with a composite structures program. The composite aircraft program glider (CAPGLIDE) is an undergraduate demonstration project which has as its objectives the design, fabrication, and testing of a foot launched ultralight glider using composite structures. The objective of the computer aided design (COMPAD) portion of the composites project is to provide computer tools for the analysis and design of composite structures. The major thrust of COMPAD is in the finite element area with effort directed at implementing finite element analysis capabilities and developing interactive graphics preprocessing and postprocessing capabilities. The criteria for selecting research projects to be conducted under the innovative and supporting research (INSURE) program are described.

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

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.

Buckling Analysis of Single and Multi Delamination In Composite Beam Using Finite Element Method

NASA Astrophysics Data System (ADS)

Simanjorang, Hans Charles; Syamsudin, Hendri; Giri Suada, Muhammad

2018-04-01

Delamination is one type of imperfection in structure which found usually in the composite structure. Delamination may exist due to some factors namely in-service condition where the foreign objects hit the composite structure and creates inner defect and poor manufacturing that causes the initial imperfections. Composite structure is susceptible to the compressive loading. Compressive loading leads the instability phenomenon in the composite structure called buckling. The existence of delamination inside of the structure will cause reduction in buckling strength. This paper will explain the effect of delamination location to the buckling strength. The analysis will use the one-dimensional modelling approach using two- dimensional finite element method.

On the vibration properties of composite materials and structures

NASA Astrophysics Data System (ADS)

Lu, Y. P.; Neilson, H. C.; Roscoe, A. J.

1993-01-01

In recent years, there has been a widespread assumption that composite materials and structures offer enhanced vibration and acoustic properties. This assumption has to be evaluated or validated. The objective of this article is to address the subject of vibration characteristics and the related force transmissibility properties of composite structures. For a given composite beam made of Hercules AS4/3501-6 graphite/epoxy with a layered structure sequence of (0,0,30,-30)(sub 6S), resonance frequencies, structural damping, responses, impedances, and force transmissibility properties are determined, discussed, and compared with those of a steel beam. This article proposes a procedure to evaluate the vibration properties of individual composites. The criterion defined for performance comparison between composite materials and conventional materials is also discussed.

Distributed multifunctional sensor network for composite structural state sensing

NASA Astrophysics Data System (ADS)

Qing, Xinlin P.; Wang, Yishou; Gao, Limin; Kumar, Amrita

2012-04-01

Advanced fiber reinforced composite materials are becoming the main structural materials of next generation of aircraft because of their high strength and stiffness to weight ratios, and strong designability. In order to take full advantages of composite materials, there is a need to develop an embeddable multifunctional sensing system to allow a structure to "feel" and "think" its structural state. In this paper, the concept of multifunctional sensor network integrated with a structure, similar to the human nervous system, has been developed. Different types of network sensors are permanently integrated within a composite structure to sense structural strain, temperature, moisture, aerodynamic pressure; monitor external impact on the structure; and detect structural damages. Utilizing this revolutionary concept, future composite structures can be designed and manufactured to provide multiple modes of information, so that the structures have the capabilities for intelligent sensing, environmental adaptation and multi-functionality. The challenges for building such a structural state sensing system and some solutions to address the challenges are also discussed in the paper.

Fuselage structure using advanced technology fiber reinforced composites

NASA Technical Reports Server (NTRS)

Robinson, R. K.; Tomlinson, H. M. (Inventor)

1982-01-01

A fuselage structure is described in which the skin is comprised of layers of a matrix fiber reinforced composite, with the stringers reinforced with the same composite material. The high strength to weight ratio of the composite, particularly at elevated temperatures, and its high modulus of elasticity, makes it desirable for use in airplane structures.

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.

Composite membrane with integral rim

DOEpatents

Routkevitch, Dmitri; Polyakov, Oleg G

2015-01-27

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.

Computational composite mechanics for aerospace propulsion structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1986-01-01

Specialty methods are presented for the computational simulation of specific composite behavior. These methods encompass all aspects of composite mechanics, impact, progressive fracture and component specific simulation. Some of these methods are structured to computationally simulate, in parallel, the composite behavior and history from the initial fabrication through several missions and even to fracture. Select methods and typical results obtained from such simulations are described in detail in order to demonstrate the effectiveness of computationally simulating (1) complex composite structural behavior in general and (2) specific aerospace propulsion structural components in particular.

Computational composite mechanics for aerospace propulsion structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

1987-01-01

Specialty methods are presented for the computational simulation of specific composite behavior. These methods encompass all aspects of composite mechanics, impact, progressive fracture and component specific simulation. Some of these methods are structured to computationally simulate, in parallel, the composite behavior and history from the initial frabrication through several missions and even to fracture. Select methods and typical results obtained from such simulations are described in detail in order to demonstrate the effectiveness of computationally simulating: (1) complex composite structural behavior in general, and (2) specific aerospace propulsion structural components in particular.

14 CFR 29.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Composite Rotorcraft Structures. 29.573 Section 29.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 27.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2012 CFR

2012-01-01

... Composite Rotorcraft Structures. 27.573 Section 27.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 27.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Composite Rotorcraft Structures. 27.573 Section 27.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 29.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2013 CFR

2013-01-01

... Composite Rotorcraft Structures. 29.573 Section 29.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 27.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Composite Rotorcraft Structures. 27.573 Section 27.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

14 CFR 29.573 - Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures.

Code of Federal Regulations, 2014 CFR

2014-01-01

... Composite Rotorcraft Structures. 29.573 Section 29.573 Aeronautics and Space FEDERAL AVIATION ADMINISTRATION... Structures. (a) Each applicant must evaluate the composite rotorcraft structure under the damage tolerance..., types, and sizes of damage, considering fatigue, environmental effects, intrinsic and discrete flaws...

Designing for fiber composite structural durability in hygrothermomechanical environment

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1985-01-01

A methodology is described which can be used to design/analyze fiber composite structures subjected to complex hygrothermomechanical environments. This methodology includes composite mechanics and advanced structural analysis methods (finite element). Select examples are described to illustrate the application of the available methodology. The examples include: (1) composite progressive fracture; (2) composite design for high cycle fatigue combined with hot-wet conditions; and (3) general laminate design.

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

NASA Technical Reports Server (NTRS)

1974-01-01

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

Wood-based composite materials : panel products, glued-laminated timber, structural composite lumber, and wood-nonwood composite materials

Treesearch

Nicole M. Stark; Zhiyong Cai; Charles Carll

2010-01-01

This chapter gives an overview of the general types and composition of wood-based composite products and the materials and processes used to manufacture them. It describes conventional wood-based composite panels and structural composite materials intended for general construction, interior use, or both. This chapter also describes wood–nonwood composites. Mechanical...

Development of stitched/RTM composite primary structures

NASA Technical Reports Server (NTRS)

Kullerd, Susan M.; Dow, Marvin B.

1992-01-01

The goal of the NASA Advanced Composites Technology (ACT) Program is to provide the technology required to gain the full benefit of weight savings and performance offered by composite primary structures. Achieving the goal is dependent on developing composite materials and structures which are damage tolerant and economical to manufacture. Researchers at NASA LaRC and Douglas Aircraft Company are investigating stitching reinforcement combined with resin transfer molding (RTM) to create structures meeting the ACT program goals. The Douglas work is being performed under a NASA contract entitled Innovative Composites Aircraft Primary Structures (ICAPS). The research is aimed at materials, processes and structural concepts for application in both transport wings and fuselages. Empirical guidelines are being established for stitching reinforcement in primary structures. New data are presented in this paper for evaluation tests of thick (90-ply) and thin (16-ply) stitched laminates, and from selection tests of RTM composite resins. Tension strength, compression strength and post-impact compression strength data are reported. Elements of a NASA LaRC program to expand the science base for stitched/RTM composites are discussed.

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.

Optimization of composite wood structural components : processing and design choices

Treesearch

Theodore L. Laufenberg

1985-01-01

Decreasing size and quality of the world's forest resources are responsible for interest in producing composite wood structural components. Process and design optimization methods are offered in this paper. Processing concepts for wood composite structural products are reviewed to illustrate manufacturing boundaries and areas of high potential. Structural...

Transient Dynamic Response and Failure of Composite Structure Under Cyclic Loading with Fluid Structure Interaction

DTIC Science & Technology

2014-09-01

TERMS fluid structure interaction, composite structures shipbuilding, fatigue loading 15. NUMBER OF PAGES 85 16. PRICE CODE 17. SECURITY...under the three point bending test. All the composites exhibit an initial nonlinear and inelastic deformation trend and end with a catastrophic abrupt

Study on voids of epoxy matrix composites sandwich structure parts

NASA Astrophysics Data System (ADS)

He, Simin; Wen, Youyi; Yu, Wenjun; Liu, Hong; Yue, Cheng; Bao, Jing

2017-03-01

Void is the most common tiny defect of composite materials. Porosity is closely related to composite structure property. The voids forming behaviour in the composites sandwich structural parts with the carbon fiber reinforced epoxy resin skins was researched by adjusting the manufacturing process parameters. The composites laminate with different porosities were prepared with the different process parameter. The ultrasonic non-destructive measurement method for the porosity was developed and verified through microscopic examination. The analysis results show that compaction pressure during the manufacturing process had influence on the porosity in the laminate area. Increasing the compaction pressure and compaction time will reduce the porosity of the laminates. The bond-line between honeycomb core and carbon fiber reinforced epoxy resin skins were also analyzed through microscopic examination. The mechanical properties of sandwich structure composites were studied. The optimization process parameters and porosity ultrasonic measurement method for composites sandwich structure have been applied to the production of the composite parts.

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.

In-service health monitoring of composite structures

NASA Technical Reports Server (NTRS)

Pinto, Gino A.; Ventres, C. S.; Ginty, Carol A.; Chamis, Christos C.

1990-01-01

The aerospace industry is witnessing a vast utilization of composites in critical structural applications and anticipates even more use of them in future aircraft. Therefore, a definite need exists for a composite health monitoring expert system to meet today's current needs and tomorrow's future demands. The primary goal for this conceptual health monitoring system is functional reliably for in-service operation in the environments of various composite structures. The underlying philosophy of this system is to utilize proven vibration techniques to assess the structural integrity of a fibrous composite. Statistical methods are used to determine if the variances in the measured data are acceptable for making a reliable decision on the health status of the composite. The flexible system allows for algorithms describing any composite fatigue or damage behavior characteristic to be provided as an input to the system. Alert thresholds and variances can also be provided as an input to this system and may be updated to allow for future changes/refinements in the composite's structural integrity behavior.

Dimensionally stable composite structures and composite mirrors for spaceborne optical instruments

NASA Astrophysics Data System (ADS)

Sippel, Rudolf; Stute, Thomas; Erdl, Günther

2018-04-01

This paper, "Dimensionally stable composite structures and composite mirrors for spaceborne optical instruments," was presented as part of International Conference on Space Optics—ICSO 1997, held in Toulouse, France.

Integrated mechanics for the passive damping of polymer-matrix composites and composite structures

NASA Technical Reports Server (NTRS)

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

1991-01-01

Some recent developments on integrated damping mechanics for unidirectional composites, laminates, and composite structures are reviewed. Simplified damping micromechanics relate the damping of on-axis and off-axis composites to constituent properties, fiber volume ratio, fiber orientation, temperature, and moisture. Laminate and structural damping mechanics for thin composites are summarized. Discrete layer damping mechanics for thick laminates, including the effects of interlaminar shear damping, are developed and semianalytical predictions of modal damping in thick simply supported specialty composite plates are presented. Applications show the advantages of the unified mechanics, and illustrate the effect of fiber volume ratio, fiber orientation, structural geometry, and temperature on the damping. Additional damping properties for composite plates of various laminations, aspect ratios, fiber content, and temperature illustrate the merits and ranges of applicability of each theory (thin or thick laminates).

Isolation of Thermal and Strain Responses in Composites Using Embedded Fiber Bragg Grating Temperature Sensors

DTIC Science & Technology

2013-05-10

13. SUPPLEMENTARY NOTES 14. ABSTRACT In this research, fiber Bragg grating ( FBG ) optical temperature sensors are used for structural health...surface of a composite structure. FBG sensors also respond to axial strain in the optical fiber, thus any structural strain experienced by the composite...features. First, a three-dimensional array of FBG temperature sensors has been embedded in a carbon/epoxy composite structure, consisting of both in

Carbon fiber epoxy composites for both strengthening and health monitoring of structures.

PubMed

Salvado, Rita; Lopes, Catarina; Szojda, Leszek; Araújo, Pedro; Gorski, Marcin; Velez, Fernando José; Castro-Gomes, João; Krzywon, Rafal

2015-05-06

This paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the "wet process", which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring.

Carbon Fiber Epoxy Composites for Both Strengthening and Health Monitoring of Structures

PubMed Central

Salvado, Rita; Lopes, Catarina; Szojda, Leszek; Araújo, Pedro; Gorski, Marcin; Velez, Fernando José; Castro-Gomes, João; Krzywon, Rafal

2015-01-01

This paper presents a study of the electrical and mechanical behavior of several continuous carbon fibers epoxy composites for both strengthening and monitoring of structures. In these composites, the arrangement of fibers was deliberately diversified to test and understand the ability of the composites for self-sensing low strains. Composites with different arrangements of fibers and textile weaves, mainly unidirectional continuous carbon reinforced composites, were tested at the dynamometer. A two-probe method was considered to measure the relative electrical resistance of these composites during loading. The measured relative electrical resistance includes volume and contact electrical resistances. For all tested specimens, it increases with an increase in tensile strain, at low strain values. This is explained by the improved alignment of fibers and resulting reduction of the number of possible contacts between fibers during loading, increasing as a consequence the contact electrical resistance of the composite. Laboratory tests on strengthening of structural elements were also performed, making hand-made composites by the “wet process”, which is commonly used in civil engineering for the strengthening of all types of structures in-situ. Results show that the woven epoxy composite, used for strengthening of concrete elements is also able to sense low deformations, below 1%. Moreover, results clearly show that this textile sensor also improves the mechanical work of the strengthened structural elements, increasing their bearing capacity. Finally, the set of obtained results supports the concept of a textile fabric capable of both structural upgrade and self-monitoring of structures, especially large structures of difficult access and needing constant, sometimes very expensive, health monitoring. PMID:25954955

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.

Composite structural materials

NASA Technical Reports Server (NTRS)

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

1979-01-01

A multifaceted program is described in which aeronautical, mechanical, and materials engineers interact to develop composite aircraft structures. Topics covered include: (1) the design of an advanced composite elevator and a proposed spar and rib assembly; (2) optimizing fiber orientation in the vicinity of heavily loaded joints; (3) failure mechanisms and delamination; (4) the construction of an ultralight sailplane; (5) computer-aided design; finite element analysis programs, preprocessor development, and array preprocessor for SPAR; (6) advanced analysis methods for composite structures; (7) ultrasonic nondestructive testing; (8) physical properties of epoxy resins and composites; (9) fatigue in composite materials, and (10) transverse thermal expansion of carbon/epoxy composites.

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Sonic Fatigue Design Techniques for Advanced Composite Aircraft Structures

DTIC Science & Technology

1980-04-01

AFWAL-TR-80.3019 AD A 090553 SONIC FATIGUE DESIGN TECHNIQUES FOR ADVANCED COMPOSITE AIRCRAFT STRUCTURES FINAL REPORT Ian Holehouse Rohr Industries...5 2. General Sonic Fatigue Theory .... ....... 7 3. Composite Laminate Analysis .. ....... ... 10 4. Preliminary Sonic Fatigue...overall sonic fatigue design guides. These existing desiyn methcds have been developed for metal structures. However, recent advanced composite

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Progressive fracture of polymer matrix composite structures: A new approach

NASA Technical Reports Server (NTRS)

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

1992-01-01

A new approach independent of stress intensity factors and fracture toughness parameters has been developed and is described for the computational simulation of progressive fracture of polymer matrix composite structures. The damage stages are quantified based on physics via composite mechanics while the degradation of the structural behavior is quantified via the finite element method. The approach account for all types of composite behavior, structures, load conditions, and fracture processes starting from damage initiation, to unstable propagation and to global structural collapse. Results of structural fracture in composite beams, panels, plates, and shells are presented to demonstrate the effectiveness and versatility of this new approach. Parameters and guidelines are identified which can be used as criteria for structural fracture, inspection intervals, and retirement for cause. Generalization to structures made of monolithic metallic materials are outlined and lessons learned in undertaking the development of new approaches, in general, are summarized.

Fuzzy Modal Control Applied to Smart Composite Structure

NASA Astrophysics Data System (ADS)

Koroishi, E. H.; Faria, A. W.; Lara-Molina, F. A.; Steffen, V., Jr.

2015-07-01

This paper proposes an active vibration control technique, which is based on Fuzzy Modal Control, as applied to a piezoelectric actuator bonded to a composite structure forming a so-called smart composite structure. Fuzzy Modal Controllers were found to be well adapted for controlling structures with nonlinear behavior, whose characteristics change considerably with respect to time. The smart composite structure was modelled by using a so called mixed theory. This theory uses a single equivalent layer for the discretization of the mechanical displacement field and a layerwise representation of the electrical field. Temperature effects are neglected. Due to numerical reasons it was necessary to reduce the size of the model of the smart composite structure so that the design of the controllers and the estimator could be performed. The role of the Kalman Estimator in the present contribution is to estimate the modal states of the system, which are used by the Fuzzy Modal controllers. Simulation results illustrate the effectiveness of the proposed vibration control methodology for composite structures.

Structural Design of Ares V Interstage Composite Structure

NASA Technical Reports Server (NTRS)

Sleigh, David W.; Sreekantamurthy, Thammaiah; Kosareo, Daniel N.; Martin, Robert A.; Johnson, Theodore F.

2011-01-01

Preliminary and detailed design studies were performed to mature composite structural design concepts for the Ares V Interstage structure as a part of NASA s Advanced Composite Technologies Project. Aluminum honeycomb sandwich and hat-stiffened composite panel structural concepts were considered. The structural design and analysis studies were performed using HyperSizer design sizing software and MSC Nastran finite element analysis software. System-level design trade studies were carried out to predict weight and margins of safety for composite honeycomb-core sandwich and composite hat-stiffened skin design concepts. Details of both preliminary and detailed design studies are presented in the paper. For the range of loads and geometry considered in this work, the hat-stiffened designs were found to be approximately 11-16 percent lighter than the sandwich designs. A down-select process was used to choose the most favorable structural concept based on a set of figures of merit, and the honeycomb sandwich design was selected as the best concept based on advantages in manufacturing cost.

Fluid-Structure Interaction in Composite Structures

DTIC Science & Technology

2014-03-01

polymer composite structures. Some previous experimental observations were confirmed using the results from the computer simulations , which also...computer simulations , which also enhanced understanding the effect of FSI on dynamic responses of composite structures. vi THIS PAGE INTENTIONALLY...forces) are applied. A great amount of research has been made using the FEM to study and simulate the cases when the structures are surrounded by

Energy Finite Element Analysis Developments for Vibration Analysis of Composite Aircraft Structures

NASA Technical Reports Server (NTRS)

Vlahopoulos, Nickolas; Schiller, Noah H.

2011-01-01

The Energy Finite Element Analysis (EFEA) has been utilized successfully for modeling complex structural-acoustic systems with isotropic structural material properties. In this paper, a formulation for modeling structures made out of composite materials is presented. An approach based on spectral finite element analysis is utilized first for developing the equivalent material properties for the composite material. These equivalent properties are employed in the EFEA governing differential equations for representing the composite materials and deriving the element level matrices. The power transmission characteristics at connections between members made out of non-isotropic composite material are considered for deriving suitable power transmission coefficients at junctions of interconnected members. These coefficients are utilized for computing the joint matrix that is needed to assemble the global system of EFEA equations. The global system of EFEA equations is solved numerically and the vibration levels within the entire system can be computed. The new EFEA formulation for modeling composite laminate structures is validated through comparison to test data collected from a representative composite aircraft fuselage that is made out of a composite outer shell and composite frames and stiffeners. NASA Langley constructed the composite cylinder and conducted the test measurements utilized in this work.

Method of fabricating composite structures

NASA Technical Reports Server (NTRS)

Sigur, W. A. (Inventor)

1990-01-01

A method of fabricating structures formed from composite materials by positioning the structure about a high coefficient of thermal expansion material, wrapping a graphite fiber overwrap about the structure, and thereafter heating the assembly to expand the high coefficient of thermal expansion material to forcibly compress the composite structure against the restraint provided by the graphite overwrap. The high coefficient of thermal expansion material is disposed about a mandrel with a release system therebetween, and with a release system between the material having the high coefficient of thermal expansion and the composite material, and between the graphite fibers and the composite structure. The heating may occur by inducing heat into the assembly by a magnetic field created by coils disposed about the assembly through which alternating current flows. The method permits structures to be formed without the use of an autoclave.

Method of fabricating composite structures

NASA Technical Reports Server (NTRS)

Sigur, Wanda A. (Inventor)

1992-01-01

A method of fabricating structures formed from composite materials by positioning the structure about a high coefficient of thermal expansion material, wrapping a graphite fiber overwrap about the structure, and thereafter heating the assembly to expand the high coefficient of thermal expansion material to forcibly compress the composite structure against the restraint provided by the graphite overwrap. The high coefficient of thermal expansion material is disposed about a mandrel with a release system therebetween, and with a release system between the material having the high coefficient of thermal expansion and the composite material, and between the graphite fibers and the composite structure. The heating may occur by inducing heat into the assembly by a magnetic field created by coils disposed about the assembly through which alternating current flows. The method permits structures to be formed without the use of an autoclave.

Composite Payload Fairing Structural Architecture Assessment and Selection

NASA Technical Reports Server (NTRS)

Krivanek, Thomas M.; Yount, Bryan C.

2012-01-01

This paper provides a summary of the structural architecture assessments conducted and a recommendation for an affordable high performance composite structural concept to use on the next generation heavy-lift launch vehicle, the Space Launch System (SLS). The Structural Concepts Element of the Advanced Composites Technology (ACT) project and its follow on the Lightweight Spacecraft Structures and Materials (LSSM) project was tasked with evaluating a number of composite construction technologies for specific Ares V components: the Payload Shroud, the Interstage, and the Core Stage Intertank. Team studies strived to address the structural challenges, risks and needs for each of these vehicle components. Leveraging off of this work, the subsequent Composites for Exploration (CoEx) effort is focused on providing a composite structural concept to support the Payload Fairing for SLS. This paper documents the evaluation and down selection of composite construction technologies and evolution to the SLS Payload Fairing. Development of the evaluation criteria (also referred to as Figures of Merit or FOMs), their relative importance, and association to vehicle requirements are presented. A summary of the evaluation results, and a recommendation of the composite concept to baseline in the Composites for Exploration (CoEx) project is presented. The recommendation for the SLS Fairing is a Honeycomb Sandwich architecture based primarily on affordability and performance with two promising alternatives, Hat stiffened and Fiber Reinforced Foam (FRF) identified for eventual program block upgrade.

Simulation of Impact Phenomena on the Composite Structures Containing Ceramic Plates and High Entropy Alloys

NASA Astrophysics Data System (ADS)

Geantă, V.; Cherecheș, T.; Lixandru, P.; Voiculescu, I.; Ștefănoiu, R.; Dragnea, D.; Zecheru, T.; Matache, L.

2017-06-01

Due to excellent mechanical properties, high entropy alloys from the system AlxCrFeCoNi can be used successfully to create composite structures containing both metallic and ceramic plates, which resists at dynamic load during high speeds impact (like projectiles, explosion). The paper presents four different composite structures made from a combination of metallic materials and ceramics plates: duralumin-ceramics, duralumin-ceramics-HEA, HEA-ceramics-HEA, HEA-ceramics-duralumin. Numerical simulation of impact behavior of the composite structures was performed by virtual methods, taking into account the mechanical properties of both materials. The best results were obtained using composite structures HEA-ceramics-HEA, HEA-ceramics-duralumin.

Probabilistic assessment of smart composite structures

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Shiao, Michael C.

1994-01-01

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

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.

Composite structures for magnetosphere imager spacecraft

NASA Technical Reports Server (NTRS)

Chu, Tsuchin

1994-01-01

Results of a trade study addressing the issues and benefits in using carbon fiber reinforced composites for the Magnetosphere Imager (MI) spacecraft are presented. The MI mission is now part of the Sun/Earth Connection Program. To qualify for this category, new technology and innovative methods to reduce the cost and size have to be considered. Topics addressed cover: (1) what is a composite, including advantages and disadvantages of composites and carbon/graphite fibers; and (2) structural design for MI, including composite design configuration, material selection, and analysis of composite structures.

Analysis of truss, beam, frame, and membrane components. [composite structures

NASA Technical Reports Server (NTRS)

Knoell, A. C.; Robinson, E. Y.

1975-01-01

Truss components are considered, taking into account composite truss structures, truss analysis, column members, and truss joints. Beam components are discussed, giving attention to composite beams, laminated beams, and sandwich beams. Composite frame components and composite membrane components are examined. A description is given of examples of flat membrane components and examples of curved membrane elements. It is pointed out that composite structural design and analysis is a highly interactive, iterative procedure which does not lend itself readily to characterization by design or analysis function only.-

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.

Automated Fabrication Technologies for High Performance Polymer Composites

NASA Technical Reports Server (NTRS)

Shuart , M. J.; Johnston, N. J.; Dexter, H. B.; Marchello, J. M.; Grenoble, R. W.

1998-01-01

New fabrication technologies are being exploited for building high graphite-fiber-reinforced composite structure. Stitched fiber preforms and resin film infusion have been successfully demonstrated for large, composite wing structures. Other automatic processes being developed include automated placement of tacky, drapable epoxy towpreg, automated heated head placement of consolidated ribbon/tape, and vacuum-assisted resin transfer molding. These methods have the potential to yield low cost high performance structures by fabricating composite structures to net shape out-of-autoclave.

Fire resistance of structural composite lumber products

Treesearch

Robert H. White

2006-01-01

Use of structural composite lumber products is increasing. In applications requiring a fire resistance rating, calculation procedures are used to obtain the fire resistance rating of exposed structural wood products. A critical factor in the calculation procedures is char rate for ASTM E 119 fire exposure. In this study, we tested 14 structural composite lumber...

Study on the fabrication of composite photonic crystals with high structural stability by co-sedimentation self-assembly on fabric substrates

NASA Astrophysics Data System (ADS)

Li, Yichen; Zhou, Lan; Liu, Guojin; Chai, Liqin; Fan, Qinguo; Shao, Jianzhong

2018-06-01

The Silica/Poly(methylmethacrylate-butylacrylate)[SiO2/P(MMA-BA)] photonic crystals(PCs) with brilliant structural colors were fabricated on fabric substrates by co-sedimentation self-assembly, in which the relatively smaller P(MMA-BA) copolymer particles filled in the interstices among the larger SiO2 microspheres. The fabricated composite PCs were mechanically robust and strongly bonded to the substrate because of the cementing effect caused by the soft P(MMA-BA) copolymer particles filling in the interstices of the SiO2 microspheres like cement filling in the gap and tightly holding stones in a sturdy cement wall. The volume fraction and the size ratios of the two components significantly influenced the structural colors of the composite PCs, and the larger volume fraction could improve the structural stability of the composite PCs, while the smaller size ratios could enhance the brightness of the structural colors of the composite PCs. The composite PCs with both high structural stability and brilliant structural colors have great application prospect for structural coloration of textiles.

Topology Optimization of Lightweight Lattice Structural Composites Inspired by Cuttlefish Bone

NASA Astrophysics Data System (ADS)

Hu, Zhong; Gadipudi, Varun Kumar; Salem, David R.

2018-03-01

Lattice structural composites are of great interest to various industries where lightweight multifunctionality is important, especially aerospace. However, strong coupling among the composition, microstructure, porous topology, and fabrication of such materials impedes conventional trial-and-error experimental development. In this work, a discontinuous carbon fiber reinforced polymer matrix composite was adopted for structural design. A reliable and robust design approach for developing lightweight multifunctional lattice structural composites was proposed, inspired by biomimetics and based on topology optimization. Three-dimensional periodic lattice blocks were initially designed, inspired by the cuttlefish bone microstructure. The topologies of the three-dimensional periodic blocks were further optimized by computer modeling, and the mechanical properties of the topology optimized lightweight lattice structures were characterized by computer modeling. The lattice structures with optimal performance were identified.

Developing polymer composite materials: carbon nanotubes or graphene?

PubMed

Sun, Xuemei; Sun, Hao; Li, Houpu; Peng, Huisheng

2013-10-04

The formation of composite materials represents an efficient route to improve the performances of polymers and expand their application scopes. Due to the unique structure and remarkable mechanical, electrical, thermal, optical and catalytic properties, carbon nanotube and graphene have been mostly studied as a second phase to produce high performance polymer composites. Although carbon nanotube and graphene share some advantages in both structure and property, they are also different in many aspects including synthesis of composite material, control in composite structure and interaction with polymer molecule. The resulting composite materials are distinguished in property to meet different applications. This review article mainly describes the preparation, structure, property and application of the two families of composite materials with an emphasis on the difference between them. Some general and effective strategies are summarized for the development of polymer composite materials based on carbon nanotube and graphene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrated analysis of engine structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1981-01-01

The need for light, durable, fuel efficient, cost effective aircraft requires the development of engine structures which are flexible, made from advaced materials (including composites), resist higher temperatures, maintain tighter clearances and have lower maintenance costs. The formal quantification of any or several of these requires integrated computer programs (multilevel and/or interdisciplinary analysis programs interconnected) for engine structural analysis/design. Several integrated analysis computer prorams are under development at Lewis Reseach Center. These programs include: (1) COBSTRAN-Composite Blade Structural Analysis, (2) CODSTRAN-Composite Durability Structural Analysis, (3) CISTRAN-Composite Impact Structural Analysis, (4) STAEBL-StruTailoring of Engine Blades, and (5) ESMOSS-Engine Structures Modeling Software System. Three other related programs, developed under Lewis sponsorship, are described.

Fluid-Structure Interaction in a Fluid-Filled Composite Structure Subjected to Low Velocity Impact

DTIC Science & Technology

2016-06-01

for creating an E-glass composite cubic structure and a pendulum was designed and built to provide a repeatable low velocity impact. The behavior of...structure and a pendulum was designed and built to provide a repeatable low velocity impact. The behavior of the composite structure was studied at various...SET-UP .......................................................31  1.  Impact Pendulum

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

Degenhardt, R.; PFH, Private University of Applied Sciences Goettingen, Composite Engineering Campus Stade; Araujo, F. C. de

European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. Formore » unstiffened cylindrical composite shells a proposal for a new design method is presented.« less

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.

Ultrasonic nonlinear guided wave inspection of microscopic damage in a composite structure

NASA Astrophysics Data System (ADS)

Zhang, Li; Borigo, Cody; Owens, Steven; Lissenden, Clifford; Rose, Joseph; Hakoda, Chris

2017-02-01

Sudden structural failure is a severe safety threat to many types of military and industrial composite structures. Because sudden structural failure may occur in a composite structure shortly after macroscale damage initiates, reliable early diagnosis of microdamage formation in the composite structure is critical to ensure safe operation and to reduce maintenance costs. Ultrasonic guided waves have been widely used for long-range defect detection in various structures. When guided waves are generated under certain excitation conditions, in addition to the traditional linear wave mode (known as the fundamental harmonic wave mode), a number of nonlinear higher-order harmonic wave modes are also be generated. Research shows that the nonlinear parameters of a higher-order harmonic wave mode could have excellent sensitivity to microstructural changes in a material. In this work, we successfully employed a nonlinear guided wave structural health monitoring (SHM) method to detect microscopic impact damage in a 32-layer carbon/epoxy fiber-reinforced composite plate. Our effort has demonstrated that, utilizing appropriate transducer design, equipment, excitation signals, and signal processing techniques, nonlinear guided wave parameter measurements can be reliably used to monitor microdamage initiation and growth in composite structures.

Stiffness analysis of glued connection of the timber-concrete structure

NASA Astrophysics Data System (ADS)

Daňková, Jana; Mec, Pavel; Majstríková, Tereza

2016-01-01

This paper presents results of experimental and mathematical analysis of stiffness characteristics of a composite timber-concrete structure. The composite timberconcrete structure presented herein is non-typical compared to similar types of building structures. The interaction between the timber and concrete part of the composite cross-section is not based on metal connecting elements, but it is ensured by a glued-in perforated mesh made of plywood. The paper presents results of experimental and mathematical analysis for material alternatives of the solution of the glued joint. The slip modulus values were determined experimentally. Data obtained from the experiment evaluated by means of regression analysis. Test results were also used as input data for the compilation of a 3D model of a composite structure by means of the 3D finite element model. On the basis of result evaluation, it can be stated that the stress-deformation behaviour at shear loading of this specific timber-concrete composite structure can be affected by the type of glue used. Parameters of the 3D model of both alternative of the structure represent well the behaviour of the composite structure and the model can be used for predicting design parameters of a building structure.

Nanotechnologies for Composite Structures- From Nanocomposites to Multifunctional Nano-Enabled Fibre Reinforced Composites for Spacecrafts

NASA Astrophysics Data System (ADS)

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

2014-06-01

The past decade, extensive efforts have been invested in understanding the nano-scale and revealing the capabilities offered by nanotechnology products to structural materials. 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. In this work, we present the experience obtained from the latest nanotechnology research activities supported by ESA. The paper focuses on prepreg composite manufacturing technology and addresses:- Approaches for nano-enabling of composites- Up-scaling strategies towards final structures- Latest results on performance of nano-enabledfiber reinforced compositesSeveral approaches for the utilization of nanotechnology products in structural composite structures have been proposed and are reviewed, in short along with respective achieved results. A variety of nano-fillers has been proposed and employed, individually or in combination in hybrid forms, to approach the desired performance. A major part of the work deals with the up-scaling routes of these technologies to reach final products and industrial scales and processes while meeting end-user performance.

Effect of Sn-Ag-Cu on the Improvement of Electromigration Behavior in Sn-58Bi Solder Joint

NASA Astrophysics Data System (ADS)

Wang, Fengjiang; Zhou, Lili; Zhang, Zhijie; Wang, Jiheng; Wang, Xiaojing; Wu, Mingfang

2017-10-01

Reliability issues caused by the formation of a Bi-rich layer at the anode interface usually occurs in the Sn-58Bi eutectic solder joint during electromigration (EM). To improve the EM performance of a Sn-58Bi solder joint, Sn-3.0Ag-0.5Cu solder was introduced into it to produce SnBi-SnAgCu structural or compositional composite joints, and their EM behaviors were investigated with the current density of 1.0 × 104 A/cm2 for different stressing times. The structure of the compositional composite solder joint was obtained by the occurrence of partial or full mixing between Sn-Bi and Sn-Ag-Cu solder with a suitable soldering temperature. In the structural composite joint, melted Sn-Bi was partially mixed with Sn-Ag-Cu solder to produce a Cu/Sn-Bi/Sn-Ag-Cu/Sn-Bi/Cu structure. In the compositional composite joint, full melting and mixing between these two solders occurred to produce a Cu/Sn-Ag-Cu-Bi/Cu structure, in which the solder matrix was a homogeneous structure including Sn, Bi phases, Cu6Sn5 and Ag3Sn IMCs. After current stressing, the EM performance of Sn-Bi solder was obviously improved with the structural or the compositional composite joint. In Sn-58Bi joints, a thick Bi-rich layer was easily produced at the anode interface, and obviously increased with stressing time. However, after current stressing on the structural composite joints, the existence of s Sn-3.0Ag-0.5Cu interlayer between the two Sn-58Bi solders effectively acted as a diffusion barrier and significantly slowed the formation of the Bi-rich layer at the anode side and the IMC thicknesses at the interfaces.

Characterization and manufacture of braided composites for large commercial aircraft structures

NASA Technical Reports Server (NTRS)

Fedro, Mark J.; Willden, Kurtis

1992-01-01

Braided composite materials has been recognized as a potential cost effective material form for fuselage structural elements. Consequently, there is a strong need for more knowledge in the design, manufacture, test, and analysis of textile structural composites. Advance braided composite technology is advanced towards applications to a large commercial transport fuselage. The mechanics are summarized of materials and manufacturing demonstration results which were obtained in order to acquire an understanding of how braided composites can be applied to a commercial fuselage. Textile composites consisting of 2-D, 2-D triaxial, and 3-D braid patterns with thermoplastic and two resin transfer molding resin systems were studied. The structural performance of braided composites was evaluated through an extensive mechanical test program. Analytical methods were also developed and applied to predict the following: internal fiber architecture; stiffness; fiber stresses; failure mechanisms; notch effects; and the history of failure of the braided composite specimens. The applicability of braided composites to a commercial transport fuselage was further assessed through a manufacturing demonstration.

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.

Multi-field coupled sensing network for health monitoring of composite bolted joint

NASA Astrophysics Data System (ADS)

Wang, Yishou; Qing, Xinlin; Dong, Liang; Banerjee, Sourav

2016-04-01

Advanced fiber reinforced composite materials are becoming the main structural materials of next generation of aircraft because of their high strength and stiffness to weight ratios, and excellent designability. As key components of large composite structures, joints play important roles to ensure the integrity of the composite structures. However, it is very difficult to analyze the strength and failure modes of composite joints due to their complex nonlinear coupling factors. Therefore, there is a need to monitor, diagnose, evaluate and predict the structure state of composite joints. This paper proposes a multi-field coupled sensing network for health monitoring of composite bolted joints. Major work of this paper includes: 1) The concept of multifunctional sensor layer integrated with eddy current sensors, Rogowski coil and arrayed piezoelectric sensors; 2) Development of the process for integrating the eddy current sensor foil, Rogowski coil and piezoelectric sensor array in multifunctional sensor layer; 3) A new concept of smart composite joint with multifunctional sensing capability. The challenges for building such a structural state sensing system and some solutions to address the challenges are also discussed in the study.

Study on utilization of advanced composites in fuselage structures of large transports

NASA Technical Reports Server (NTRS)

Johnson, R. W.; Thomson, L. W.; Wilson, R. D.

1985-01-01

The potential for utilizing advanced composites in fuselage structures of large transports was assessed. Six fuselage design concepts were selected and evaluated in terms of structural performance, weight, and manufacturing development and costs. Two concepts were selected that merit further consideration for composite fuselage application. These concepts are: (1) a full depth honeycomb design with no stringers, and (2) an I section stringer stiffened laminate skin design. Weight reductions due to applying composites to the fuselages of commercial and military transports were calculated. The benefits of applying composites to a fleet of military transports were determined. Significant technology issues pertinent to composite fuselage structures were identified and evaluated. Program plans for resolving the technology issues were developed.

Effect of Interface Structure on Mechanical Properties of Advanced Composite Materials

PubMed Central

Gan, Yong X.

2009-01-01

This paper deals with the effect of interface structures on the mechanical properties of fiber reinforced composite materials. First, the background of research, development and applications on hybrid composite materials is introduced. Second, metal/polymer composite bonded structures are discussed. Then, the rationale is given for nanostructuring the interface in composite materials and structures by introducing nanoscale features such as nanopores and nanofibers. The effects of modifying matrices and nano-architecturing interfaces on the mechanical properties of nanocomposite materials are examined. A nonlinear damage model for characterizing the deformation behavior of polymeric nanocomposites is presented and the application of this model to carbon nanotube-reinforced and reactive graphite nanotube-reinforced epoxy composite materials is shown. PMID:20054466

Durability of commercial aircraft and helicopter composite structures

NASA Technical Reports Server (NTRS)

Dexter, H. B.

1982-01-01

The development of advanced composite technology during the past decade is discussed. Both secondary and primary components fabricated with boron, graphite, and Kevlar composites are evaluated. Included are spoilers, rudders, and fairings on commercial transports, boron/epoxy reinforced wing structure on C-130 military transports, and doors, fairings, tail rotors, vertical fins, and horizontal stabilizers on commercial helicopters. The development of composite structures resulted in advances in design and manufacturing technology for secondary and primary composite structures for commercial transports. Design concepts and inspection and maintenance results for the components in service are reported. The flight, outdoor ground, and controlled laboratory environmental effects on composites were also determined. Effects of moisture absorption, ultraviolet radiation, aircraft fuels and fluids, and sustained tensile stress are included. Critical parameters affecting the long term durability of composite materials are identified.

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

NASA Technical Reports Server (NTRS)

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

1993-01-01

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

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.

Making Large Composite Vessels Without Autoclaves

NASA Technical Reports Server (NTRS)

Sigur, W. A.

1989-01-01

Method for making fiber-reinforced composite structure relies on heating and differential thermal expansion to provide temperature and pressure necessary to develop full strength, without having to place structure in large, expensive autoclave. Layers of differentially expanding material squeeze fiber-reinforce composite between them when heated. Method suitable for such cylindrical structures as pressure vessels and tanks. Used for both resin-matrix and metal-matrix composites.

Improving aircraft composite inspections using optimized reference standards

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

Roach, D.; Dorrell, L.; Kollgaard, J.

1998-10-01

The rapidly increasing use of composites on commercial airplanes coupled with the potential for economic savings associated with their use in aircraft structures means that the demand for composite materials technology will continue to increase. Inspecting these composite structures is a critical element in assuring this continued airworthiness. The FAA`s Airworthiness Assurance NDI Validation Center, in conjunction with the Commercial Aircraft Composite Repair committee, is developing a set of composite reference standards to be used in NDT equipment calibration for accomplishment of damage assessment and post-repair inspection of all commercial aircraft composites. In this program, a series of NDI testsmore » on a matrix of composite aircraft structures and prototype reference standards were completed in order to minimize the number of standards needed to carry out composite inspections on aircraft. Two tasks, related to composite laminates and non-metallic composite honeycomb configurations, were addressed.« less

Design and Manufacturing of Composite Tower Structure for Wind Turbine Equipment

NASA Astrophysics Data System (ADS)

Park, Hyunbum

2018-02-01

This study proposes the composite tower design process for large wind turbine equipment. In this work, structural design of tower and analysis using finite element method was performed. After structural design, prototype blade manufacturing and test was performed. The used material is a glass fiber and epoxy resin composite. And also, sand was used in the middle part. The optimized structural design and analysis was performed. The parameter for optimized structural design is weight reduction and safety of structure. Finally, structure of tower will be confirmed by structural test.

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.

Composite structural materials

NASA Technical Reports Server (NTRS)

Loewy, Robert G.; Wiberley, Stephen E.

1987-01-01

The development and application of composite materials to aerospace vehicle structures which began in the mid 1960's has now progressed to the point where what can be considered entire airframes are being designed and built using composites. Issues related to the fabrication of non-resin matrix composites and the micro, mezzo and macromechanics of thermoplastic and metal matrix composites are emphasized. Several research efforts are presented. They are entitled: (1) The effects of chemical vapor deposition and thermal treatments on the properties of pitch-based carbon fiber; (2) Inelastic deformation of metal matrix laminates; (3) Analysis of fatigue damage in fibrous MMC laminates; (4) Delamination fracture toughness in thermoplastic matrix composites; (5) Numerical investigation of the microhardness of composite fracture; and (6) General beam theory for composite structures.

Quantification of Energy Release in Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

2003-01-01

Energy release rate is usually suggested as a quantifier for assessing structural damage tolerance. Computational prediction of energy release rate is based on composite mechanics with micro-stress level damage assessment, finite element structural analysis and damage progression tracking modules. This report examines several issues associated with energy release rates in composite structures as follows: Chapter I demonstrates computational simulation of an adhesively bonded composite joint and validates the computed energy release rates by comparison with acoustic emission signals in the overall sense. Chapter II investigates the effect of crack plane orientation with respect to fiber direction on the energy release rates. Chapter III quantifies the effects of contiguous constraint plies on the residual stiffness of a 90 ply subjected to transverse tensile fractures. Chapter IV compares ICAN and ICAN/JAVA solutions of composites. Chapter V examines the effects of composite structural geometry and boundary conditions on damage progression characteristics.

Quantification of Energy Release in Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon; Chamis, Christos C. (Technical Monitor)

2003-01-01

Energy release rate is usually suggested as a quantifier for assessing structural damage tolerance. Computational prediction of energy release rate is based on composite mechanics with micro-stress level damage assessment, finite element structural analysis and damage progression tracking modules. This report examines several issues associated with energy release rates in composite structures as follows: Chapter I demonstrates computational simulation of an adhesively bonded composite joint and validates the computed energy release rates by comparison with acoustic emission signals in the overall sense. Chapter II investigates the effect of crack plane orientation with respect to fiber direction on the energy release rates. Chapter III quantifies the effects of contiguous constraint plies on the residual stiffness of a 90 deg ply subjected to transverse tensile fractures. Chapter IV compares ICAN and ICAN/JAVA solutions of composites. Chapter V examines the effects of composite structural geometry and boundary conditions on damage progression characteristics.

Natural cork agglomerate employed as an environmentally friendly solution for quiet sandwich composites.

PubMed

Sargianis, James; Kim, Hyung-ick; Suhr, Jonghwan

2012-01-01

Carbon fiber-synthetic foam core sandwich composites are widely used for many structural applications due to their superior mechanical performance and low weight. Unfortunately these structures typically have very poor acoustic performance. There is increasingly growing demand in mitigating this noise issue in sandwich composite structures. This study shows that marrying carbon fiber composites with natural cork in a sandwich structure provides a synergistic effect yielding a noise-free sandwich composite structure without the sacrifice of mechanical performance or weight. Moreover the cork-core sandwich composites boast a 250% improvement in damping performance, providing increased durability and lifetime operation. Additionally as the world seeks environmentally friendly materials, the harvesting of cork is a natural, renewable process which reduces subsequent carbon footprints. Such a transition from synthetic foam cores to natural cork cores could provide unprecedented improvements in acoustic and vibrational performance in applications such as aircraft cabins or wind turbine blades.

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

NASA Technical Reports Server (NTRS)

Tenney, Darrel R.

2008-01-01

AS&M performed a broad assessment survey and study to establish the potential composite materials and structures applications and benefits to the Constellation Program Elements. Trade studies were performed on selected elements to determine the potential weight or performance payoff from use of composites. Weight predictions were made for liquid hydrogen and oxygen tanks, interstage cylindrical shell, lunar surface access module, ascent module liquid methane tank, and lunar surface manipulator. A key part of this study was the evaluation of 88 different composite technologies to establish their criticality to applications for the Constellation Program. The overall outcome of this study shows that composites are viable structural materials which offer from 20% to 40% weight savings for many of the structural components that make up the Major Elements of the Constellation Program. NASA investment in advancing composite technologies for space structural applications is an investment in America's Space Exploration Program.

Some Lower Valence Vanadium Fluorides: Their Crystal Distortions, Domain Structures, Modulated Structures, Ferrimagnetism, and Composition Dependence.

ERIC Educational Resources Information Center

Hong, Y. S.; And Others

1980-01-01

Describes some contemporary concepts unique to the structure of advanced solids, i.e., their crystal distortions, domain structures, modulated structures, ferrimagnetism, and composition dependence. (Author/CS)

A novel method for a multi-level hierarchical composite with brick-and-mortar structure

PubMed Central

Brandt, Kristina; Wolff, Michael F. H.; Salikov, Vitalij; Heinrich, Stefan; Schneider, Gerold A.

2013-01-01

The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic particles as building blocks for the first level, followed by spouted bed spray granulation for a second level, and finally directional hot pressing to anisotropically consolidate the composite. The microstructure achieved reveals a brick-and-mortar hierarchical structure with distinct, however not yet optimized mechanical properties on each level. It opens up a completely new processing route for the synthesis of multi-level hierarchically structured composites, giving prospects to multi-functional structure-properties relationships. PMID:23900554

A novel method for a multi-level hierarchical composite with brick-and-mortar structure.

PubMed

Brandt, Kristina; Wolff, Michael F H; Salikov, Vitalij; Heinrich, Stefan; Schneider, Gerold A

2013-01-01

The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic particles as building blocks for the first level, followed by spouted bed spray granulation for a second level, and finally directional hot pressing to anisotropically consolidate the composite. The microstructure achieved reveals a brick-and-mortar hierarchical structure with distinct, however not yet optimized mechanical properties on each level. It opens up a completely new processing route for the synthesis of multi-level hierarchically structured composites, giving prospects to multi-functional structure-properties relationships.

A novel method for a multi-level hierarchical composite with brick-and-mortar structure

NASA Astrophysics Data System (ADS)

Brandt, Kristina; Wolff, Michael F. H.; Salikov, Vitalij; Heinrich, Stefan; Schneider, Gerold A.

2013-07-01

The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic particles as building blocks for the first level, followed by spouted bed spray granulation for a second level, and finally directional hot pressing to anisotropically consolidate the composite. The microstructure achieved reveals a brick-and-mortar hierarchical structure with distinct, however not yet optimized mechanical properties on each level. It opens up a completely new processing route for the synthesis of multi-level hierarchically structured composites, giving prospects to multi-functional structure-properties relationships.

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.

76 FR 68366 - Airworthiness Directives; The Boeing Company Model 777-200 and -300 Series Airplanes

Federal Register 2010, 2011, 2012, 2013, 2014

2011-11-04

...-induced currents and subsequent damage to composite structures, hydraulic tubes, and actuator control... and could subsequently damage composite structures, hydraulic tubes, and actuator control electronics... subsequent damage to composite structures, hydraulic tubes, and actuator control electronics. In the event of...

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.

Next generation control system for reflexive aerostructures

NASA Astrophysics Data System (ADS)

Maddux, Michael R.; Meents, Elizabeth P.; Barnell, Thomas J.; Cable, Kristin M.; Hemmelgarn, Christopher; Margraf, Thomas W.; Havens, Ernie

2010-04-01

Cornerstone Research Group Inc. (CRG) has developed and demonstrated a composite structural solution called reflexive composites for aerospace applications featuring CRG's healable shape memory polymer (SMP) matrix. In reflexive composites, an integrated structural health monitoring (SHM) system autonomously monitors the structural health of composite aerospace structures, while integrated intelligent controls monitor data from the SHM system to characterize damage and initiate healing when damage is detected. Development of next generation intelligent controls for reflexive composites were initiated for the purpose of integrating prognostic health monitoring capabilities into the reflexive composite structural solution. Initial efforts involved data generation through physical inspections and mechanical testing. Compression after impact (CAI) testing was conducted on composite-reinforced shape memory polymer samples to induce damage and investigate the effectiveness of matrix healing on mechanical performance. Non-destructive evaluation (NDE) techniques were employed to observe and characterize material damage. Restoration of mechanical performance was demonstrated through healing, while NDE data showed location and size of damage and verified mitigation of damage post-healing. Data generated was used in the development of next generation reflexive controls software. Data output from the intelligent controls could serve as input to Integrated Vehicle Health Management (IVHM) systems and Integrated Resilient Aircraft Controls (IRAC). Reflexive composite technology has the ability to reduce maintenance required on composite structures through healing, offering potential to significantly extend service life of aerospace vehicles and reduce operating and lifecycle costs.

Advanced Composite Structures At NASA Langley Research Center

NASA Technical Reports Server (NTRS)

Eldred, Lloyd B.

2015-01-01

Dr. Eldred's presentation will discuss several NASA efforts to improve and expand the use of composite structures within aerospace vehicles. Topics will include an overview of NASA's Advanced Composites Project (ACP), Space Launch System (SLS) applications, and Langley's ISAAC robotic composites research tool.

Review of Aircraft Crash Structural Response Research.

DTIC Science & Technology

1982-08-01

structures consisting of conventional built-up metallic construction and those consisting of advanced composite materials were of interest. The latter...increasing importance. Some recent theoretical and experimental studies of the behavior of composite - material structures subjected to severe static...dynamic, and/or impact conditions are noted. Such topics as crashworthiness testing ot composite fuselage structures, the impact resistance of graphite and

A Review of the NASA Textile Composites Research

NASA Technical Reports Server (NTRS)

Poe, C. C., Jr.; Dexter, H. B.; Raju, I. S.

1997-01-01

During the past 15 years NASA has taken the lead role in exploiting the benefits of textile reinforced composite materials for application to aircraft structures. The NASA Advanced Composites Technology (ACT) program was started in 1989 to develop composite primary structures for commercial transport airplanes with costs that are competitive with metal structures. As part of this program, several contractors investigated the cost, weight, and performance attributes of textile reinforced composites. Textile composites made using resin transfer molding type processes were evaluated for numerous applications. Methods were also developed to predict resin infiltration and flow in textile preforms and to predict and measure mechanical properties of the textile composites. This paper describes the salient results of that program.

Design considerations for fiber composite structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.

1972-01-01

An overview of the design methodology for designing structural components from fiber composites is presented. In particular, the need for new conceptual structural designs for the future is discussed and the evolution of conceptual design is illustrated. Sources of design data, analysis and design procedures, and the basic components of structural fiber composites are cited and described. Examples of tradeoff studies and optimum designs are discussed and a simple structure is described in some detail.

NASA-UVa light aerospace alloy and structures technology program

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Haviland, John K.; Herakovich, Carl T.; Pilkey, Walter D.; Pindera, Marek-Jerzy; Scully, John R.; Stoner, Glenn E.; Swanson, Robert E.; Thornton, Earl A.; Wawner, Franklin E., Jr.

1991-01-01

The general objective of the NASA-UVa Light Aerospace Alloy and Structures Technology Program was to conduct research on the performance of next generation, light weight aerospace alloys, composites, and associated thermal gradient structures. The following research areas were actively investigated: (1) mechanical and environmental degradation mechanisms in advanced light metals and composites; (2) aerospace materials science; (3) mechanics of materials and composites for aerospace structures; and (4) thermal gradient structures.

A guide to structural factors for advanced composites used on spacecraft

NASA Technical Reports Server (NTRS)

Vanwagenen, Robert

1989-01-01

The use of composite materials in spacecraft systems is constantly increasing. Although the areas of composite design and fabrication are maturing, they remain distinct from the same activities performed using conventional materials and processes. This has led to some confusion regarding the precise meaning of the term 'factor of safety' as it applies to these structures. In addition, composite engineering introduces terms such as 'knock-down factors' to further modify material properties for design purposes. This guide is intended to clarify these terms as well as their use in the design of composite structures for spacecraft. It is particularly intended to be used by the engineering community not involved in the day-to-day composites design process. An attempt is also made to explain the wide range of factors of safety encountered in composite designs as well as their relationship to the 1.4 factor of safety conventionally applied to metallic structures.

Diamagnetic composite material structure for reducing undesired electromagnetic interference and eddy currents in dielectric wall accelerators and other devices

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

Caporaso, George J.; Poole, Brian R.; Hawkins, Steven A.

2015-06-30

The devices, systems and techniques disclosed here can be used to reduce undesired effects by magnetic field induced eddy currents based on a diamagnetic composite material structure including diamagnetic composite sheets that are separated from one another to provide a high impedance composite material structure. In some implementations, each diamagnetic composite sheet includes patterned conductor layers are separated by a dielectric material and each patterned conductor layer includes voids and conductor areas. The voids in the patterned conductor layers of each diamagnetic composite sheet are arranged to be displaced in position from one patterned conductor layer to an adjacent patternedmore » conductor layer while conductor areas of the patterned conductor layers collectively form a contiguous conductor structure in each diamagnetic composite sheet to prevent penetration by a magnetic field.« less

Strain-Detecting Composite Materials

NASA Technical Reports Server (NTRS)

Wallace, Terryl A. (Inventor); Smith, Stephen W. (Inventor); Piascik, Robert S. (Inventor); Horne, Michael R. (Inventor); Messick, Peter L. (Inventor); Alexa, Joel A. (Inventor); Glaessgen, Edward H. (Inventor); Hailer, Benjamin T. (Inventor)

2016-01-01

A composite material includes a structural material and a shape-memory alloy embedded in the structural material. The shape-memory alloy changes crystallographic phase from austenite to martensite in response to a predefined critical macroscopic average strain of the composite material. In a second embodiment, the composite material includes a plurality of particles of a ferromagnetic shape-memory alloy embedded in the structural material. The ferromagnetic shape-memory alloy changes crystallographic phase from austenite to martensite and changes magnetic phase in response to the predefined critical macroscopic average strain of the composite material. A method of forming a composite material for sensing the predefined critical macroscopic average strain includes providing the shape-memory alloy having an austenite crystallographic phase, changing a size and shape of the shape-memory alloy to thereby form a plurality of particles, and combining the structural material and the particles at a temperature of from about 100-700.degree. C. to form the composite material.

Transport composite fuselage technology: Impact dynamics and acoustic transmission

NASA Technical Reports Server (NTRS)

Jackson, A. C.; Balena, F. J.; Labarge, W. L.; Pei, G.; Pitman, W. A.; Wittlin, G.

1986-01-01

A program was performed to develop and demonstrate the impact dynamics and acoustic transmission technology for a composite fuselage which meets the design requirements of a 1990 large transport aircraft without substantial weight and cost penalties. The program developed the analytical methodology for the prediction of acoustic transmission behavior of advanced composite stiffened shell structures. The methodology predicted that the interior noise level in a composite fuselage due to turbulent boundary layer will be less than in a comparable aluminum fuselage. The verification of these analyses will be performed by NASA Langley Research Center using a composite fuselage shell fabricated by filament winding. The program also developed analytical methodology for the prediction of the impact dynamics behavior of lower fuselage structure constructed with composite materials. Development tests were performed to demonstrate that the composite structure designed to the same operating load requirement can have at least the same energy absorption capability as aluminum structure.

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…

77 FR 42547 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-19

... and Fatigue Evaluation of Composite Rotorcraft Structures AGENCY: Federal Aviation Administration (FAA... Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures. Form Numbers: There are no FAA forms... ``Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft Structures'' final rule (76 FR 74655...

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.

Effects of floor location on response of composite fuselage frames

NASA Technical Reports Server (NTRS)

Carden, Huey D.; Jones, Lisa E.; Fasanella, Edwin L.

1992-01-01

Experimental and analytical results are presented which show the effect of floor placement on the structural response and strength of circular fuselage frames constructed of graphite-epoxy composite material. The research was conducted to study the behavior of conventionally designed advanced composite aircraft components. To achieve desired new designs which incorporate improved energy absorption capabilities requires an understanding of how these conventional designs behave under crash type loadings. Data are presented on the static behavior of the composite structure through photographs of the frame specimen, experimental strain distributions, and through analytical data from composite structural models. An understanding of this behavior can aid the dynamist in predicting the crash behavior of these structures and may assist the designer in achieving improved designs for energy absorption and crash behavior of future structures.

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

NASA Astrophysics Data System (ADS)

Werner, Brian Thomas

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

Study of the structure of 3-D composites based on carbon nanotubes in bovine serum albumin matrix by X-ray microtomography

NASA Astrophysics Data System (ADS)

Ignatov, D.; Zhurbina, N.; Gerasimenko, A.

2017-01-01

3-D composites are widely used in tissue engineering. A comprehensive analysis by X-ray microtomography was conducted to study the structure of the 3-D composites. Comprehensive analysis of the structure of the 3-D composites consisted of scanning, image reconstruction of shadow projections, two-dimensional and three-dimensional visualization of the reconstructed images and quantitative analysis of the samples. Experimental samples of composites were formed by laser vaporization of the aqueous dispersion BSA and single-walled (SWCNTs) and multi-layer (MWCNTs) carbon nanotubes. The samples have a homogeneous structure over the entire volume, the percentage of porosity of 3-D composites based on SWCNTs and MWCNTs - 16.44%, 28.31%, respectively. An average pore diameter of 3-D composites based on SWCNTs and MWCNTs - 45 μm 93 μm. 3-D composites based on carbon nanotubes in bovine serum albumin matrix can be used in tissue engineering of bone and cartilage, providing cell proliferation and blood vessel sprouting.

Method of making a continuous ceramic fiber composite hot gas filter

DOEpatents

Hill, Charles A.; Wagner, Richard A.; Komoroski, Ronald G.; Gunter, Greg A.; Barringer, Eric A.; Goettler, Richard W.

1999-01-01

A ceramic fiber composite structure particularly suitable for use as a hot gas cleanup ceramic fiber composite filter and method of making same from ceramic composite material has a structure which provides for increased strength and toughness in high temperature environments. The ceramic fiber composite structure or filter is made by a process in which a continuous ceramic fiber is intimately surrounded by discontinuous chopped ceramic fibers during manufacture to produce a ceramic fiber composite preform which is then bonded using various ceramic binders. The ceramic fiber composite preform is then fired to create a bond phase at the fiber contact points. Parameters such as fiber tension, spacing, and the relative proportions of the continuous ceramic fiber and chopped ceramic fibers can be varied as the continuous ceramic fiber and chopped ceramic fiber are simultaneously formed on the porous vacuum mandrel to obtain a desired distribution of the continuous ceramic fiber and the chopped ceramic fiber in the ceramic fiber composite structure or filter.

Thermally Stable and Electrically Conductive, Vertically Aligned Carbon Nanotube/Silicon Infiltrated Composite Structures for High-Temperature Electrodes.

PubMed

Zou, Qi Ming; Deng, Lei Min; Li, Da Wei; Zhou, Yun Shen; Golgir, Hossein Rabiee; Keramatnejad, Kamran; Fan, Li Sha; Jiang, Lan; Silvain, Jean-Francois; Lu, Yong Feng

2017-10-25

Traditional ceramic-based, high-temperature electrode materials (e.g., lanthanum chromate) are severely limited due to their conditional electrical conductivity and poor stability under harsh circumstances. Advanced composite structures based on vertically aligned carbon nanotubes (VACNTs) and high-temperature ceramics are expected to address this grand challenge, in which ceramic serves as a shielding layer protecting the VACNTs from the oxidation and erosive environment, while the VACNTs work as a conductor. However, it is still a great challenge to fabricate VACNT/ceramic composite structures due to the limited diffusion of ceramics inside the VACNT arrays. In this work, we report on the controllable fabrication of infiltrated (and noninfiltrated) VACNT/silicon composite structures via thermal chemical vapor deposition (CVD) [and laser-assisted CVD]. In laser-assisted CVD, low-crystalline silicon (Si) was quickly deposited at the VACNT subsurfaces/surfaces followed by the formation of high-crystalline Si layers, thus resulting in noninfiltrated composite structures. Unlike laser-assisted CVD, thermal CVD activated the precursors inside and outside the VACNTs simultaneously, which realized uniform infiltrated VACNT/Si composite structures. The growth mechanisms for infiltrated and noninfiltrated VACNT/ceramic composites, which we attributed to the different temperature distributions and gas diffusion mechanism in VACNTs, were investigated. More importantly, the as-farbicated composite structures exhibited excellent multifunctional properties, such as excellent antioxidative ability (up to 1100 °C), high thermal stability (up to 1400 °C), good high velocity hot gas erosion resistance, and good electrical conductivity (∼8.95 Sm -1 at 823 K). The work presented here brings a simple, new approach to the fabrication of advanced composite structures for hot electrode applications.

High renewable content sandwich structures based on flax-basalt hybrids and biobased epoxy polymers

NASA Astrophysics Data System (ADS)

Colomina, S.; Boronat, T.; Fenollar, O.; Sánchez-Nacher, L.; Balart, R.

2014-05-01

In the last years, a growing interest in the development of high environmental efficiency materials has been detected and this situation is more accentuated in the field of polymers and polymer composites. In this work, green composite sandwich structures with high renewable content have been developed with core cork materials. The base resin for composites was a biobased epoxy resin derived from epoxidized vegetable oils. Hybrid basalt-flax fabrics have been used as reinforcements for composites and the influence of the stacking sequence has been evaluated in order to optimize the appropriate laminate structure for the sandwich bases. Core cork materials with different thickness have been used to evaluate performance of sandwich structures thus leading to high renewable content composite sandwich structures. Results show that position of basalt fabrics plays a key role in flexural fracture of sandwich structures due to differences in stiffness between flax and basalt fibers.

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.

Flight service environmental effects on composite materials and structures

NASA Technical Reports Server (NTRS)

Dexter, H. Benson; Baker, Donald J.

1992-01-01

NASA Langley and the U.S. Army have jointly sponsored programs to assess the effects of realistic flight environments and ground-based exposure on advanced composite materials and structures. Composite secondary structural components were initially installed on commercial transport aircraft in 1973; secondary and primary structural components were installed on commercial helicopters in 1979; and primary structural components were installed on commercial aircraft in the mid-to-late 1980's. Service performance, maintenance characteristics, and residual strength of numerous components are reported. In addition to data on flight components, 10 year ground exposure test results on material coupons are reported. Comparison between ground and flight environmental effects for several composite material systems are also presented. Test results indicate excellent in-service performance with the composite components during the 15 year period. Good correlation between ground-based material performance and operational structural performance has been achieved.

Glass-mica composite: a new structural thermal-insulating material for building applications

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

Low, N.M.P.

1981-12-01

Homogeneous, rigid glass-mica composites have been synthesized from mixtures of Canadian natural mica flakes of the phlogopite type and ground glass powders prepared from recycled soda-lime waste glasses by a simple sintering process. By means of selection of compositions and processing techniques, composites can be fabricated into products that exhibit a celular structure, a highly densified structure, and multilayer and sandwich structures. The cellular structure composite has a thermal conductivity in the range of 0.165 to 0.230 W/m /sup 0/C when measured over the temperature range 25 to 180/sup 0/C, and a compressive strength of about 0.874 MPa; the highlymore » densified composite, on the other hand, has a thermal conductivity in the range of 0.155 to 0.330 W/m /sup 0/C, a compressive strength in excess of 40 MPa, and an instantaneous coefficient of thermal expansion of 5.8 X 10/sup -6///sup 0/C at 100/sup 0/C. These glass-mica composites exhibit qualities such as insulating efficiency, safety, mechanical strength, and durability that are suitable for engineering applications in building structures or other systems.« less

Brillouin Optical Correlation Domain Analysis in Composite Material Beams

PubMed Central

Stern, Yonatan; London, Yosef; Preter, Eyal; Antman, Yair; Diamandi, Hilel Hagai; Silbiger, Maayan; Adler, Gadi; Shalev, Doron; Zadok, Avi

2017-01-01

Structural health monitoring is a critical requirement in many composites. Numerous monitoring strategies rely on measurements of temperature or strain (or both), however these are often restricted to point-sensing or to the coverage of small areas. Spatially-continuous data can be obtained with optical fiber sensors. In this work, we report high-resolution distributed Brillouin sensing over standard fibers that are embedded in composite structures. A phase-coded, Brillouin optical correlation domain analysis (B-OCDA) protocol was employed, with spatial resolution of 2 cm and sensitivity of 1 °K or 20 micro-strain. A portable measurement setup was designed and assembled on the premises of a composite structures manufacturer. The setup was successfully utilized in several structural health monitoring scenarios: (a) monitoring the production and curing of a composite beam over 60 h; (b) estimating the stiffness and Young’s modulus of a composite beam; and (c) distributed strain measurements across the surfaces of a model wing of an unmanned aerial vehicle. The measurements are supported by the predictions of structural analysis calculations. The results illustrate the potential added values of high-resolution, distributed Brillouin sensing in the structural health monitoring of composites. PMID:28974041

Brillouin Optical Correlation Domain Analysis in Composite Material Beams.

PubMed

Stern, Yonatan; London, Yosef; Preter, Eyal; Antman, Yair; Diamandi, Hilel Hagai; Silbiger, Maayan; Adler, Gadi; Levenberg, Eyal; Shalev, Doron; Zadok, Avi

2017-10-02

Structural health monitoring is a critical requirement in many composites. Numerous monitoring strategies rely on measurements of temperature or strain (or both), however these are often restricted to point-sensing or to the coverage of small areas. Spatially-continuous data can be obtained with optical fiber sensors. In this work, we report high-resolution distributed Brillouin sensing over standard fibers that are embedded in composite structures. A phase-coded, Brillouin optical correlation domain analysis (B-OCDA) protocol was employed, with spatial resolution of 2 cm and sensitivity of 1 °K or 20 micro-strain. A portable measurement setup was designed and assembled on the premises of a composite structures manufacturer. The setup was successfully utilized in several structural health monitoring scenarios: (a) monitoring the production and curing of a composite beam over 60 h; (b) estimating the stiffness and Young's modulus of a composite beam; and (c) distributed strain measurements across the surfaces of a model wing of an unmanned aerial vehicle. The measurements are supported by the predictions of structural analysis calculations. The results illustrate the potential added values of high-resolution, distributed Brillouin sensing in the structural health monitoring of composites.

Structural Arrangement Trade Study. Volume 1: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Executive summary

NASA Astrophysics Data System (ADS)

1995-03-01

This volume is the first of a three volume set that discusses the structural arrangement trade study plan that will identify the most suitable configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Primary Structures most suitable for intertank, wing and thrust structures are identified. This executive summary presents the trade study process, the selection process, requirements used, analysis performed and data generated. Conclusions and recommendations are also presented.

Analysis of passive damping in thick composite structures

NASA Technical Reports Server (NTRS)

Saravanos, D. A.

1993-01-01

Computational mechanics for the prediction of damping and other dynamic characteristics in composite structures of general thicknesses and laminations are presented. Discrete layer damping mechanics that account for the representation of interlaminar shear effects in the material are summarized. Finite element based structural mechanics for the analysis of damping are described, and a specialty finite element is developed. Applications illustrate the quality of the discrete layer damping mechanics in predicting the damped dynamic characteristics of composite structures with thicker sections and/or laminate configurations that induce interlaminar shear. The results also illustrate and quantify the significance of interlaminar shear damping in such composite structures.

Structural Arrangement Trade Study. Volume 1: Reusable Hydrogen Composite Tank System (RHCTS) and Graphite Composite Primary Structures (GCPS). Executive summary

NASA Technical Reports Server (NTRS)

1995-01-01

This volume is the first of a three volume set that discusses the structural arrangement trade study plan that will identify the most suitable configuration for an SSTO winged vehicle capable of delivering 25,000 lbs to a 220 nm circular orbit at 51.6 deg inclination. The Reusable Hydrogen Composite Tank System (RHCTS), and Graphite Composite Primary Structures most suitable for intertank, wing and thrust structures are identified. This executive summary presents the trade study process, the selection process, requirements used, analysis performed and data generated. Conclusions and recommendations are also presented.

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.

Comparison of Requirements for Composite Structures for Aircraft and Space Applications

NASA Technical Reports Server (NTRS)

Raju, Ivatury S.; Elliott, Kenny B.; Hampton, Roy W.; Knight, Norman F., Jr.; Aggarwal, Pravin; Engelstad, Stephen P.; Chang, James B.

2010-01-01

In this paper, the aircraft and space vehicle requirements for composite structures are compared. It is a valuable exercise to study composite structural design approaches used in the airframe industry, and to adopt methodology that is applicable for space vehicles. The missions, environments, analysis methods, analysis validation approaches, testing programs, build quantities, inspection, and maintenance procedures used by the airframe industry, in general, are not transferable to spaceflight hardware. Therefore, while the application of composite design approaches from other industries is appealing, many aspects cannot be directly utilized. Nevertheless, experiences and research for composite aircraft structures may be of use in unexpected arenas as space exploration technology develops, and so continued technology exchanges are encouraged.

Manufacturing development of pultruded composite panels

NASA Technical Reports Server (NTRS)

Meade, L. E.

1989-01-01

The weight savings potential, of graphite-epoxy composites for secondary and medium primary aircraft structures, was demonstrated. One of the greatest challenges facing the aircraft industry is to reduce the acquisition costs for composite structures to a level below that of metal structures. The pultrusion process, wherein reinforcing fibers, after being passed through a resin bath are drawn through a die to form and cure the desired cross-section, is an automated low cost manufacturing process for composite structures. The Lockheed Aeronautical Systems Company (LASC) Composites Development Center designed, characterizated materials for, fabricated and tested a stiffened cover concept compatible with the continuous pultrusion process. The procedures used and the results obtained are presented.

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

NASTRAN as an analytical research tool for composite mechanics and composite structures

NASA Technical Reports Server (NTRS)

Chamis, C. C.; Sinclair, J. H.; Sullivan, T. L.

1976-01-01

Selected examples are described in which NASTRAN is used as an analysis research tool for composite mechanics and for composite structural components. The examples were selected to illustrate the importance of using NASTRAN as an analysis tool in this rapidly advancing field.

Impact analysis of composite aircraft structures

NASA Technical Reports Server (NTRS)

Pifko, Allan B.; Kushner, Alan S.

1993-01-01

The impact analysis of composite aircraft structures is discussed. Topics discussed include: background remarks on aircraft crashworthiness; comments on modeling strategies for crashworthiness simulation; initial study of simulation of progressive failure of an aircraft component constructed of composite material; and research direction in composite characterization for impact analysis.

GaN-based LEDs with a high light extraction composite surface structure fabricated by a modified YAG laser lift-off technology and the patterned sapphire substrates

NASA Astrophysics Data System (ADS)

Sun, Yongjian; Trieu, Simeon; Yu, Tongjun; Chen, Zhizhong; Qi, Shengli; Tian, Pengfei; Deng, Junjing; Jin, Xiaoming; Zhang, Guoyi

2011-08-01

Vertical structure LEDs have been fabricated with a novel light extraction composite surface structure composed of a micron grating and nano-structure. The composite surface structure was generated by using a modified YAG laser lift-off technique, separating the wafers from cone-shaped patterned sapphire substrates. LEDs thus fabricated showed the light output power increase about 1.7-2.5 times when compared with conventional vertical structure LEDs grown on plane sapphire substrates. A three-dimensional finite difference time domain method was used to simulate this new kind of LED device. It was determined that nano-structures in composite surface patterns play a key role in the improvement of light extraction efficiency of LEDs.

Design Optimization of Composite Structures under Uncertainty

NASA Technical Reports Server (NTRS)

Haftka, Raphael T.

2003-01-01

Design optimization under uncertainty is computationally expensive and is also challenging in terms of alternative formulation. The work under the grant focused on developing methods for design against uncertainty that are applicable to composite structural design with emphasis on response surface techniques. Applications included design of stiffened composite plates for improved damage tolerance, the use of response surfaces for fitting weights obtained by structural optimization, and simultaneous design of structure and inspection periods for fail-safe structures.

Nano-composite materials

DOEpatents

Lee, Se-Hee; Tracy, C. Edwin; Pitts, J. Roland

2010-05-25

Nano-composite materials are disclosed. An exemplary method of producing a nano-composite material may comprise co-sputtering a transition metal and a refractory metal in a reactive atmosphere. The method may also comprise co-depositing a transition metal and a refractory metal composite structure on a substrate. The method may further comprise thermally annealing the deposited transition metal and refractory metal composite structure in a reactive atmosphere.

Evaluation of low-cost aluminum composites for aircraft engine structural applications

NASA Technical Reports Server (NTRS)

Mcdanels, D. L.; Signorelli, R. A.

1983-01-01

Panels of discontinuous SiC composites, with several aluminum matrices, were fabricated and evaluated. Modulus, yield strength and tensile strength results indicated that the properties of composites containing SiC whisker, nodule or particulate reinforcements were similar. The modulus of the composites was controlled by the volume percentage of the SiC reinforcement content, while the strength and ductility were controlled by both the reinforcement content and the matrix alloy. The feasibility of fabricating structural shapes by both wire performs and direct casting was demonstrated for Al2O3/Al composites. The feasibility of fabricating high performance composites into structural shapes by low pressure hot molding was demonstrated for B4C-coated B/Al composites.

Quantification of uncertainties in the performance of smart composite structures

NASA Technical Reports Server (NTRS)

Shiao, Michael C.; Chamis, Christos C.

1993-01-01

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

Proof test methodology for composites

NASA Technical Reports Server (NTRS)

Wu, Edward M.; Bell, David K.

1992-01-01

The special requirements for proof test of composites are identified based on the underlying failure process of composites. Two proof test methods are developed to eliminate the inevitable weak fiber sites without also causing flaw clustering which weakens the post-proof-test composite. Significant reliability enhancement by these proof test methods has been experimentally demonstrated for composite strength and composite life in tension. This basic proof test methodology is relevant to the certification and acceptance of critical composite structures. It can also be applied to the manufacturing process development to achieve zero-reject for very large composite structures.

International SAMPE Symposium and Exhibition, 35th, Anaheim, CA, Apr. 2-5, 1990, Proceedings. Books 1 2

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

Janicki, G.; Bailey, V.; Schjelderup, H.

The present conference discusses topics in the fields of ultralightweight structures, producibility of thermoplastic composites, innovation in sandwich structures, composite failure processes, toughened materials, metal-matrix composites, advanced materials for future naval systems, thermoplastic polymers, automated composites manufacturers, advanced adhesives, emerging processes for aerospace component fabrication, and modified resin systems. Also discussed are matrix behavior for damage tolerance, composite materials repair, testing for damage tolerance, composite strength analyses, materials workplace health and safety, cost-conscious composites, bismaleimide systems, and issues facing advanced composite materials suppliers.

Experimental Tensile Strength Analysis of Woven-Glass/Epoxy Composite Plates with Central Circular Hole

NASA Astrophysics Data System (ADS)

Hadi, Bambang K.; Rofa, Bima K.

2018-04-01

The use of composite materials in aerospace engineering, as well as in maritime structure has increased significantly during the recent years. The extensive use of composite materials in industrial applications should make composite structural engineers and scientists more aware of the advantage and disadvantage of this material and provide them with necessary data and certification process. One of the problems in composite structures is the existence of hole. Hole can not be avoided in actual structures, since it may be the necessity of providing access for maintenance or due to impact damage. The presence of hole will weaken the structures. Therefore, in this paper, the effect of hole on the strength of glass-woven/epoxy composite will be discussed. Extensive tests have been carried out to study the effect of hole-diameter on the tensile strengths of these specimens. The results showed that the bigger the hole-diameter compared to the width of the specimens has weakened the structures further, as expected. Further study should be carried in the future to model it with the finite element and theoretical analysis precisely.

Chemical compositions, methods of making the chemical compositions, and structures made from the chemical compositions

DOEpatents

Yang, Lei; Cheng, Zhe; Liu, Ze; Liu, Meilin

2015-01-13

Embodiments of the present disclosure include chemical compositions, structures, anodes, cathodes, electrolytes for solid oxide fuel cells, solid oxide fuel cells, fuel cells, fuel cell membranes, separation membranes, catalytic membranes, sensors, coatings for electrolytes, electrodes, membranes, and catalysts, and the like, are disclosed.

Structural Health Monitoring of Composite Materials Using Distributed Fiber Bragg Sensors

NASA Technical Reports Server (NTRS)

Grant, Joseph; Kual, Raj; Taylor, Scott; Jackson, Kurt V.; Myers, George; Wang, Y.; Sharma, A.; Burdine, Robert (Technical Monitor)

2002-01-01

Health monitoring of polymer matrix composite materials using fiber optic Bragg grating (FBG) sensors is accomplished using a tunable IR (infrared) laser via transmission mode. Results are presented from experiments of composite structures with FBG's embedded at various orientations, and surface measurements of various cryogenic composite vessels.

Study of mould design and forming process on advanced polymer-matrix composite complex structure

NASA Astrophysics Data System (ADS)

Li, S. J.; Zhan, L. H.; Bai, H. M.; Chen, X. P.; Zhou, Y. Q.

2015-07-01

Advanced carbon fibre-reinforced polymer-matrix composites are widely applied to aviation manufacturing field due to their outstanding performance. In this paper, the mould design and forming process of the complex composite structure were discussed in detail using the hat stiffened structure as an example. The key issues of the moulddesign were analyzed, and the corresponding solutions were also presented. The crucial control points of the forming process such as the determination of materials and stacking sequence, the temperature and pressure route of the co-curing process were introduced. In order to guarantee the forming quality of the composite hat stiffened structure, a mathematical model about the aperture of rubber mandrel was introduced. The study presented in this paper may provide some actual references for the design and manufacture of the important complex composite structures.

Self-assembled hierarchically structured organic-inorganic composite systems.

PubMed

Tritschler, Ulrich; Cölfen, Helmut

2016-05-13

Designing bio-inspired, multifunctional organic-inorganic composite materials is one of the most popular current research objectives. Due to the high complexity of biocomposite structures found in nacre and bone, for example, a one-pot scalable and versatile synthesis approach addressing structural key features of biominerals and affording bio-inspired, multifunctional organic-inorganic composites with advanced physical properties is highly challenging. This article reviews recent progress in synthesizing organic-inorganic composite materials via various self-assembly techniques and in this context highlights a recently developed bio-inspired synthesis concept for the fabrication of hierarchically structured, organic-inorganic composite materials. This one-step self-organization concept based on simultaneous liquid crystal formation of anisotropic inorganic nanoparticles and a functional liquid crystalline polymer turned out to be simple, fast, scalable and versatile, leading to various (multi-)functional composite materials, which exhibit hierarchical structuring over several length scales. Consequently, this synthesis approach is relevant for further progress and scientific breakthrough in the research field of bio-inspired and biomimetic materials.

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.

Coupled multi-disciplinary simulation of composite engine structures in propulsion environment

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Singhal, Surendra N.

1992-01-01

A computational simulation procedure is described for the coupled response of multi-layered multi-material composite engine structural components which are subjected to simultaneous multi-disciplinary thermal, structural, vibration, and acoustic loadings including the effect of hostile environments. The simulation is based on a three dimensional finite element analysis technique in conjunction with structural mechanics codes and with acoustic analysis methods. The composite material behavior is assessed at the various composite scales, i.e., the laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization model. Sample cases exhibiting nonlinear geometrical, material, loading, and environmental behavior of aircraft engine fan blades, are presented. Results for deformed shape, vibration frequency, mode shapes, and acoustic noise emitted from the fan blade, are discussed for their coupled effect in hot and humid environments. Results such as acoustic noise for coupled composite-mechanics/heat transfer/structural/vibration/acoustic analyses demonstrate the effectiveness of coupled multi-disciplinary computational simulation and the various advantages of composite materials compared to metals.

Design considerations for composite fuselage structure of commercial transport aircraft

NASA Technical Reports Server (NTRS)

Davis, G. W.; Sakata, I. F.

1981-01-01

The structural, manufacturing, and service and environmental considerations that could impact the design of composite fuselage structure for commercial transport aircraft application were explored. The severity of these considerations was assessed and the principal design drivers delineated. Technical issues and potential problem areas which must be resolved before sufficient confidence is established to commit to composite materials were defined. The key issues considered are: definition of composite fuselage design specifications, damage tolerance, and crashworthiness.

Advanced Residual Strength Degradation Rate Modeling for Advanced Composite Structures. Volume II. Tasks II and III.

DTIC Science & Technology

1981-07-01

ADVANCED COMPOSITE STRUCTURES VOLUME II - TASKS Ix AND III K. N. Lauraitis Tl J. T. Ryder ?l4 D. E. Pettit ~ Lockheed-California Company S Burbank...Strength Degradation Rate Final Report Modeling for Advanced Composite Structures 1 July 1979 to 29 May 1981 Vol II - Task II and III S. PERFORMIN ONG...identify by block namber) composites , graphite/epoxy, impact damage, damaged holes, fatigue, damage propagation, residual strength, NDI 20. ABSTRACT

Flight-vehicle materials, structures, and dynamics - Assessment and future directions. Vol. 3 - Ceramics and ceramic-matrix composites

NASA Technical Reports Server (NTRS)

Levine, Stanley R. (Editor)

1992-01-01

The present volume discusses ceramics and ceramic-matrix composites in prospective aerospace systems, monolithic ceramics, transformation-toughened and whisker-reinforced ceramic composites, glass-ceramic matrix composites, reaction-bonded Si3N4 and SiC composites, and chemical vapor-infiltrated composites. Also discussed are the sol-gel-processing of ceramic composites, the fabrication and properties of fiber-reinforced ceramic composites with directed metal oxidation, the fracture behavior of ceramic-matrix composites (CMCs), the fatigue of fiber-reinforced CMCs, creep and rupture of CMCs, structural design methodologies for ceramic-based materials systems, the joining of ceramics and CMCs, and carbon-carbon composites.

Layerwise Mechanics and Finite Elements for Smart Composite Structures with Piezoelectric Actuators and Sensors

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Heyliger, Paul R.; Hopkins, Dale A.

1996-01-01

Recent developments on layerwise mechanics for the analysis of composite laminates and structures with piezoelectric actuators and sensors are reviewed. The mechanics implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite structures. The corresponding finite-element implementations for the static and dynamic analysis of smart piezoelectric composite structures are also summarized. Select application illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local dynamic response of thin and/or thick laminated piezoelectric plates.

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.

Hybrid Aluminum and Natural Fiber Composite Structure for Crash Safety Improvement

NASA Astrophysics Data System (ADS)

Helaili, S.; Chafra, M.; Chevalier, Y.

There is a growing interest on pedestrian's protection in automotive safety standards. Pedestrians head impact is one of the most important tests. In this paper, a hybrid composite structure made from natural fiber and aluminum, which improve the head protection when impact is taken place, is presented. The structure is made from a honeycomb composite made from unidirectional and woven composites and a thin aluminum layer. A head impact model is developed. The number of hexagonal layers is fixed and the thickness of the aluminum layer of the honeycomb structure is varied. The specific absorption energy is then calculated.

Third Conference on Fibrous Composites in Flight Vehicle Design, part 1

NASA Technical Reports Server (NTRS)

1976-01-01

The use of fibrous composite materials in the design of aircraft and space vehicle structures and their impact on future vehicle systems are discussed. The topics covered include: flight test work on composite components, design concepts and hardware, specialized applications, operational experience, certification and design criteria. Contributions to the design technology base include data concerning material properties, design procedures, environmental exposure effects, manufacturing procedures, and flight service reliability. By including composites as baseline design materials, significant payoffs are expected in terms of reduced structural weight fractions, longer structural life, reduced fuel consumption, reduced structural complexity, and reduced manufacturing cost.

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.

Load Diffusion in Composite Structures

NASA Technical Reports Server (NTRS)

Horgan, Cornelius O.; Simmonds, J. G.

2000-01-01

This research has been concerned with load diffusion in composite structures. Fundamental solid mechanics studies were carried out to provide a basis for assessing the complicated modeling necessary for large scale structures used by NASA. An understanding of the fundamental mechanisms of load diffusion in composite subcomponents is essential in developing primary composite structures. Analytical models of load diffusion behavior are extremely valuable in building an intuitive base for developing refined modeling strategies and assessing results from finite element analyses. The decay behavior of stresses and other field quantities provides a significant aid towards this process. The results are also amendable to parameter study with a large parameter space and should be useful in structural tailoring studies.

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.

Organized energetic composites based on micro and nanostructures and methods thereof

DOEpatents

Gash, Alexander E.; Han, Thomas Yong-Jin; Sirbuly, Donald J.

2012-09-04

An ordered energetic composite structure according to one embodiment includes an ordered array of metal fuel portions; and an oxidizer in gaps located between the metal fuel portions. An ordered energetic composite structure according to another embodiment includes at least one metal fuel portion having an ordered array of nanopores; and an oxidizer in the nanopores. A method for forming an ordered energetic composite structure according to one embodiment includes forming an ordered array of metal fuel portions; and depositing an oxidizer in gaps located between the metal fuel portions. A method for forming an ordered energetic composite structure according to another embodiment includes forming an ordered array of nanopores in at least one metal fuel portion; and depositing an oxidizer in the nanopores.

Comparison of Requirements for Composite Structures for Aircraft and Space Applications

NASA Technical Reports Server (NTRS)

Raju, Ivatury S.; Elliot, Kenny B.; Hampton, Roy W.; Knight, Norman F., Jr.; Aggarwal, Pravin; Engelstad, Stephen P.; Chang, James B.

2010-01-01

In this report, the aircraft and space vehicle requirements for composite structures are compared. It is a valuable exercise to study composite structural design approaches used in the airframe industry and to adopt methodology that is applicable for space vehicles. The missions, environments, analysis methods, analysis validation approaches, testing programs, build quantities, inspection, and maintenance procedures used by the airframe industry, in general, are not transferable to spaceflight hardware. Therefore, while the application of composite design approaches from aircraft and other industries is appealing, many aspects cannot be directly utilized. Nevertheless, experiences and research for composite aircraft structures may be of use in unexpected arenas as space exploration technology develops, and so continued technology exchanges are encouraged.

Large Composite Structures Processing Technologies for Reusable Launch Vehicles

NASA Technical Reports Server (NTRS)

Clinton, R. G., Jr.; Vickers, J. H.; McMahon, W. M.; Hulcher, A. B.; Johnston, N. J.; Cano, R. J.; Belvin, H. L.; McIver, K.; Franklin, W.; Sidwell, D.

2001-01-01

Significant efforts have been devoted to establishing the technology foundation to enable the progression to large scale composite structures fabrication. We are not capable today of fabricating many of the composite structures envisioned for the second generation reusable launch vehicle (RLV). Conventional 'aerospace' manufacturing and processing methodologies (fiber placement, autoclave, tooling) will require substantial investment and lead time to scale-up. Out-of-autoclave process techniques will require aggressive efforts to mature the selected technologies and to scale up. Focused composite processing technology development and demonstration programs utilizing the building block approach are required to enable envisioned second generation RLV large composite structures applications. Government/industry partnerships have demonstrated success in this area and represent best combination of skills and capabilities to achieve this goal.

Probabilistic assessment of uncertain adaptive hybrid composites

NASA Technical Reports Server (NTRS)

Shiao, Michael C.; Singhal, Surendra N.; Chamis, Christos C.

1994-01-01

Adaptive composite structures using actuation materials, such as piezoelectric fibers, were assessed probabilistically utilizing intraply hybrid composite mechanics in conjunction with probabilistic composite structural analysis. Uncertainties associated with the actuation material as well as the uncertainties in the regular (traditional) composite material properties were quantified and considered in the assessment. Static and buckling analyses were performed for rectangular panels with various boundary conditions and different control arrangements. The probability density functions of the structural behavior, such as maximum displacement and critical buckling load, were computationally simulated. The results of the assessment indicate that improved design and reliability can be achieved with actuation material.

Polyimide composites: Application histories

NASA Technical Reports Server (NTRS)

Poveromo, L. M.

1985-01-01

Advanced composite hardware exposed to thermal environments above 127 C (260 F) must be fabricated from materials having resin matrices whose thermal/moisture resistance is superior to that of conventional epoxy-matrix systems. A family of polyimide resins has evolved in the last 10 years that exhibits the thermal-oxidative stability required for high-temperature technology applications. The weight and structural benefits for organic-matrix composites can now be extended by designers and materials engineers to include structures exposed to 316 F (600 F). Polyimide composite materials are now commercially available that can replace metallic or epoxy composite structures in a wide range of aerospace applications.

Progressive damage, fracture predictions and post mortem correlations for fiber composites

NASA Technical Reports Server (NTRS)

1985-01-01

Lewis Research Center is involved in the development of computational mechanics methods for predicting the structural behavior and response of composite structures. In conjunction with the analytical methods development, experimental programs including post failure examination are conducted to study various factors affecting composite fracture such as laminate thickness effects, ply configuration, and notch sensitivity. Results indicate that the analytical capabilities incorporated in the CODSTRAN computer code are effective in predicting the progressive damage and fracture of composite structures. In addition, the results being generated are establishing a data base which will aid in the characterization of composite fracture.

Coupled multi-disciplinary composites behavior simulation

NASA Technical Reports Server (NTRS)

Singhal, Surendra N.; Murthy, Pappu L. N.; Chamis, Christos C.

1993-01-01

The capabilities of the computer code CSTEM (Coupled Structural/Thermal/Electro-Magnetic Analysis) are discussed and demonstrated. CSTEM computationally simulates the coupled response of layered multi-material composite structures subjected to simultaneous thermal, structural, vibration, acoustic, and electromagnetic loads and includes the effect of aggressive environments. The composite material behavior and structural response is determined at its various inherent scales: constituents (fiber/matrix), ply, laminate, and structural component. The thermal and mechanical properties of the constituents are considered to be nonlinearly dependent on various parameters such as temperature and moisture. The acoustic and electromagnetic properties also include dependence on vibration and electromagnetic wave frequencies, respectively. The simulation is based on a three dimensional finite element analysis in conjunction with composite mechanics and with structural tailoring codes, and with acoustic and electromagnetic analysis methods. An aircraft engine composite fan blade is selected as a typical structural component to demonstrate the CSTEM capabilities. Results of various coupled multi-disciplinary heat transfer, structural, vibration, acoustic, and electromagnetic analyses for temperature distribution, stress and displacement response, deformed shape, vibration frequencies, mode shapes, acoustic noise, and electromagnetic reflection from the fan blade are discussed for their coupled effects in hot and humid environments. Collectively, these results demonstrate the effectiveness of the CSTEM code in capturing the coupled effects on the various responses of composite structures subjected to simultaneous multiple real-life loads.

Design of a sensor network for structural health monitoring of a full-scale composite horizontal tail

NASA Astrophysics Data System (ADS)

Gao, Dongyue; Wang, Yishou; Wu, Zhanjun; Rahim, Gorgin; Bai, Shengbao

2014-05-01

The detection capability of a given structural health monitoring (SHM) system strongly depends on its sensor network placement. In order to minimize the number of sensors while maximizing the detection capability, optimal design of the PZT sensor network placement is necessary for structural health monitoring (SHM) of a full-scale composite horizontal tail. In this study, the sensor network optimization was simplified as a problem of determining the sensor array placement between stiffeners to achieve the desired the coverage rate. First, an analysis of the structural layout and load distribution of a composite horizontal tail was performed. The constraint conditions of the optimal design were presented. Then, the SHM algorithm of the composite horizontal tail under static load was proposed. Based on the given SHM algorithm, a sensor network was designed for the full-scale composite horizontal tail structure. Effective profiles of cross-stiffener paths (CRPs) and uncross-stiffener paths (URPs) were estimated by a Lamb wave propagation experiment in a multi-stiffener composite specimen. Based on the coverage rate and the redundancy requirements, a seven-sensor array-network was chosen as the optimal sensor network for each airfoil. Finally, a preliminary SHM experiment was performed on a typical composite aircraft structure component. The reliability of the SHM result for a composite horizontal tail structure under static load was validated. In the result, the red zone represented the delamination damage. The detection capability of the optimized sensor network was verified by SHM of a full-scale composite horizontal tail; all the diagnosis results were obtained in two minutes. The result showed that all the damage in the monitoring region was covered by the sensor network.

Self-Supporting Nanoclay as Internal Scaffold Material for Direct Printing of Soft Hydrogel Composite Structures in Air.

PubMed

Jin, Yifei; Liu, Chengcheng; Chai, Wenxuan; Compaan, Ashley; Huang, Yong

2017-05-24

Three dimensional (3D) bioprinting technology enables the freeform fabrication of complex constructs from various hydrogels and is receiving increasing attention in tissue engineering. The objective of this study is to develop a novel self-supporting direct hydrogel printing approach to extrude complex 3D hydrogel composite structures in air without the help of a support bath. Laponite, a member of the smectite mineral family, is investigated to serve as an internal scaffold material for the direct printing of hydrogel composite structures in air. In the proposed printing approach, due to its yield-stress property, Laponite nanoclay can be easily extruded through a nozzle as a liquid and self-supported after extrusion as a solid. Its unique crystal structure with positive and negative charges enables it to be mixed with many chemically and physically cross-linked hydrogels, which makes it an ideal internal scaffold material for the fabrication of various hydrogel structures. By mixing Laponite nanoclay with various hydrogel precursors, the hydrogel composites retain their self-supporting capacity and can be printed into 3D structures directly in air and retain their shapes before cross-linking. Then, the whole structures are solidified in situ by applying suitable cross-linking stimuli. The addition of Laponite nanoclay can effectively improve the mechanical and biological properties of hydrogel composites. Specifically, the addition of Laponite nanoclay results in a significant increase in the Young's modulus of each hydrogel-Laponite composite: 1.9-fold increase for the poly(ethylene glycol) diacrylate (PEGDA)-Laponite composite, 7.4-fold increase for the alginate-Laponite composite, and 3.3-fold increase for the gelatin-Laponite composite.

Durability of Structural Adhesively Bonded System.

DTIC Science & Technology

1981-06-01

Composites , Finite Element Method. II DURABILITY OF STRUCTURAL ADHESIVELY BONDED SYSTEMS TABLE OF CONTENTS 1. Introduction...That investigation was mainly devoted to the temperature effects in time on the mechanical behavior of fiber-reinforced plastic (FRP) composites and...ervironmental-loading history on the mechanical performance of similar FRP composites (which may serve as adherends in structural bcnded systems). That

Preliminary Analysis of the Aluminiumtimber Composite Beams

NASA Astrophysics Data System (ADS)

Szumigała, Maciej; Chybiński, Marcin; Polus, Łukasz

2017-12-01

This paper presents a new type of composite structures - aluminium-timber beams. These structures have an advantage over other existing composite structures, because they are lighter. However, their application may be limited due to the high price of aluminium alloys. The authors of this article made an attempt to calculate the load-bearing capacity of an aluminium-timber beam.

Chapter 4. Monitoring vegetation composition and structure as habitat attributes

Treesearch

Thomas E. DeMeo; Mary M. Manning; Mary M. Rowland; Christina D. Vojta; Kevin S. McKelvey; C. Kenneth Brewer; Rebecca S.H. Kennedy; Paul A. Maus; Bethany Schulz; James A. Westfall; Timothy J. Mersmann

2013-01-01

Vegetation composition and structure are key components of wildlife habitat (Mc- Comb et al. 2010, Morrison et al. 2006) and are, therefore, essential components of all wildlife habitat monitoring. The objectives of this chapter are to describe common habitat attributes derived from vegetation composition and structure and to provide guidance for obtaining and using...

Nano-fabricated superconducting radio-frequency composites, method for producing nano-fabricated superconducting rf composites

DOEpatents

Norem, James H.; Pellin, Michael J.

2013-06-11

Superconducting rf is limited by a wide range of failure mechanisms inherent in the typical manufacture methods. This invention provides a method for fabricating superconducting rf structures comprising coating the structures with single atomic-layer thick films of alternating chemical composition. Also provided is a cavity defining the invented laminate structure.

Biomimetic and bioactive nanofibrous scaffolds from electrospun composite nanofibers

PubMed Central

Zhang, YZ; Su, B; Venugopal, J; Ramakrishna, S; Lim, CT

2007-01-01

Electrospinning is an enabling technology that can architecturally (in terms of geometry, morphology or topography) and biochemically fabricate engineered cellular scaffolds that mimic the native extracellular matrix (ECM). This is especially important and forms one of the essential paradigms in the area of tissue engineering. While biomimesis of the physical dimensions of native ECM’s major constituents (eg, collagen) is no longer a fabrication-related challenge in tissue engineering research, conveying bioactivity to electrospun nanofibrous structures will determine the efficiency of utilizing electrospun nanofibers for regenerating biologically functional tissues. This can certainly be achieved through developing composite nanofibers. This article gives a brief overview on the current development and application status of employing electrospun composite nanofibers for constructing biomimetic and bioactive tissue scaffolds. Considering that composites consist of at least two material components and phases, this review details three different configurations of nanofibrous composite structures by using hybridizing basic binary material systems as example. These are components blended composite nanofiber, core-shell structured composite nanofiber, and nanofibrous mingled structure. PMID:18203429

Composite materials for rail transit systems

NASA Technical Reports Server (NTRS)

Griffin, O. Hayden, Jr.; Guerdal, Zafer; Herakovich, Carl T.

1987-01-01

The potential is explored for using composite materials in urban mass transit systems. The emphasis was to identify specific advantages of composite materials in order to determine their actual and potential usage for carbody and guideway structure applications. The literature was reviewed, contacts were made with major domestic system operators, designers, and builders, and an analysis was made of potential composite application to railcar construction. Composites were found to be in use throughout the transit industry, usually in secondary or auxiliary applications such as car interior and nonstructural exterior panels. More recently, considerable activity has been initiated in the area of using composites in the load bearing elements of civil engineering structures such as highway bridges. It is believed that new and improved manufacturing refinements in pultrusion and filament winding will permit the production of beam sections which can be used in guideway structures. The inherent corrosion resistance and low maintenance characteristics of composites should result in lowered maintenance costs over a prolonged life of the structure.

An effect of humid climate on micro structure and chemical component of natural composite (Boehmeria nivea-Albizia falcata) based wind turbine blade

NASA Astrophysics Data System (ADS)

Sudarsono, S.; Purwanto; Sudarsono, Johny W.

2018-02-01

In this work, wind turbine blade NACA 4415 is fabricated from natural composite of Boehmeria nivea and Albizia falcate. The composite fabrication method used is hand lay up method. The aim of the work is to investigate an effect of humid climate of coastal area on micro structure and chemical composition of composite material of the blade. The wind turbine is tested at Pantai Baru, Bantul, Yogyakarta for 5.5 months. The micro structure scanning is performed with Scanning Electron Microscope (SEM) and material component is measured with Energy Dispersive X-ray spectrometer (EDS). The samples are tested before and after the use within 5.5 month at the location. The results show that composite material inexperienced interface degradation and insignificant change of micro structure. From EDS test, it is observed that Na filtration reduces C and increases O in composite material after 5.5 months.

Worldwide flight and ground-based exposure of composite materials

NASA Technical Reports Server (NTRS)

Dexter, H. B.; Baker, D. J.

1984-01-01

The long-term durability of those advanced composite materials which are applicable to aircraft structures was discussed. The composite components of various military and commercial aircraft and helicopters were reviewed. Both ground exposure and flight service were assessed in terms of their impact upon composite structure durability. The ACEE Program is mentioned briefly.

Quantitative NDE of Composite Structures at NASA

NASA Technical Reports Server (NTRS)

Cramer, K. Elliott; Leckey, Cara A. C.; Howell, Patricia A.; Johnston, Patrick H.; Burke, Eric R.; Zalameda, Joseph N.; Winfree, William P.; Seebo, Jeffery P.

2015-01-01

The use of composite materials continues to increase in the aerospace community due to the potential benefits of reduced weight, increased strength, and manufacturability. Ongoing work at NASA involves the use of the large-scale composite structures for spacecraft (payload shrouds, cryotanks, crew modules, etc). NASA is also working to enable the use and certification of composites in aircraft structures through the Advanced Composites Project (ACP). The rapid, in situ characterization of a wide range of the composite materials and structures has become a critical concern for the industry. In many applications it is necessary to monitor changes in these materials over a long time. The quantitative characterization of composite defects such as fiber waviness, reduced bond strength, delamination damage, and microcracking are of particular interest. The research approaches of NASA's Nondestructive Evaluation Sciences Branch include investigation of conventional, guided wave, and phase sensitive ultrasonic methods, infrared thermography and x-ray computed tomography techniques. The use of simulation tools for optimizing and developing these methods is also an active area of research. This paper will focus on current research activities related to large area NDE for rapidly characterizing aerospace composites.

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.

Fatigue testing of wood-concrete composite beams.

DOT National Transportation Integrated Search

2013-05-01

Currently, wood-concrete composite structural members are usually applied in building structures. There are a relatively small number (in the low 100s) of known bridge applications involving wood-concrete composites. A problem with using these novel ...

Design, Fabrication and Test of Composite Curved Frames for Helicopter Fuselage Structure

NASA Technical Reports Server (NTRS)

Lowry, D. W.; Krebs, N. E.; Dobyns, A. L.

1984-01-01

Aspects of curved beam effects and their importance in designing composite frame structures are discussed. The curved beam effect induces radial flange loadings which in turn causes flange curling. This curling increases the axial flange stresses and induces transverse bending. These effects are more important in composite structures due to their general inability to redistribute stresses by general yielding, such as in metal structures. A detailed finite element analysis was conducted and used in the design of composite curved frame specimens. Five specimens were statically tested and compared with predicted and test strains. The curved frame effects must be accurately accounted for to avoid premature fracture; finite element methods can accurately predict most of the stresses and no elastic relief from curved beam effects occurred in the composite frames tested. Finite element studies are presented for comparative curved beam effects on composite and metal frames.

Tutorial for Collecting and Processing Images of Composite Structures to Determine the Fiber Volume Fraction

NASA Technical Reports Server (NTRS)

Conklin, Lindsey

2017-01-01

Fiber-reinforced composite structures have become more common in aerospace components due to their light weight and structural efficiency. In general, the strength and stiffness of a composite structure are directly related to the fiber volume fraction, which is defined as the fraction of fiber volume to total volume of the composite. The most common method to measure the fiber volume fraction is acid digestion, which is a useful method when the total weight of the composite, the fiber weight, and the total weight can easily be obtained. However, acid digestion is a destructive test, so the material will no longer be available for additional characterization. Acid digestion can also be difficult to machine out specific components of a composite structure with complex geometries. These disadvantages of acid digestion led the author to develop a method to calculate the fiber volume fraction. The developed method uses optical microscopy to calculate the fiber area fraction based on images of the cross section of the composite. The fiber area fraction and fiber volume fraction are understood to be the same, based on the assumption that the shape and size of the fibers are consistent in the depth of the composite. This tutorial explains the developed method for optically determining fiber area fraction performed at NASA Langley Research Center.

Fabrication, polarization, and characterization of PVDF matrix composites for integrated structural load sensing

NASA Astrophysics Data System (ADS)

Haghiashtiani, Ghazaleh; Greminger, Michael A.

2015-04-01

The focus of this work is to evaluate a new carbon fiber reinforced composite structure with integrated sensing capabilities. In this composite structure, the typical matrix material used for carbon fiber reinforced composites is replaced with the thermoplastic polyvinylidene difluoride (PVDF). Since PVDF has piezoelectric properties, it enables the structure to be used for integrated load sensing. In addition, the electrical conductivity property of the carbon fabric is harnessed to form the electrodes of the integrated sensor. In order to prevent the carbon fiber electrodes from shorting to each other, a thin Kevlar fabric layer is placed between the two carbon fiber electrode layers as a dielectric. The optimal polarization parameters were determined using a design of experiments approach. Once polarized, the samples were then used in compression and tensile tests to determine the effective d33 and d31 piezoelectric coefficients. The degree of polarization of the PVDF material was determined by relating the effective d33 coefficient of the composite to the achieved d33 of the PVDF component of the composite using a closed form expression. Using this approach, it was shown that optimal polarization of the composite material results in a PVDF component d33 of 3.2 pC N-1. Moreover, the Young’s modulus of the composite structure has been characterized.

Probabilistic sizing of laminates with uncertainties

NASA Technical Reports Server (NTRS)

Shah, A. R.; Liaw, D. G.; Chamis, C. C.

1993-01-01

A reliability based design methodology for laminate sizing and configuration for a special case of composite structures is described. The methodology combines probabilistic composite mechanics with probabilistic structural analysis. The uncertainties of constituent materials (fiber and matrix) to predict macroscopic behavior are simulated using probabilistic theory. Uncertainties in the degradation of composite material properties are included in this design methodology. A multi-factor interaction equation is used to evaluate load and environment dependent degradation of the composite material properties at the micromechanics level. The methodology is integrated into a computer code IPACS (Integrated Probabilistic Assessment of Composite Structures). Versatility of this design approach is demonstrated by performing a multi-level probabilistic analysis to size the laminates for design structural reliability of random type structures. The results show that laminate configurations can be selected to improve the structural reliability from three failures in 1000, to no failures in one million. Results also show that the laminates with the highest reliability are the least sensitive to the loading conditions.

High-efficiency AlxGa1-xAs/GaAs cathode for photon-enhanced thermionic emission solar energy converters

NASA Astrophysics Data System (ADS)

Feng, Cheng; Zhang, Yijun; Qian, Yunsheng; Wang, Ziheng; Liu, Jian; Chang, Benkang; Shi, Feng; Jiao, Gangcheng

2018-04-01

A theoretical emission model for AlxGa1-xAs/GaAs cathode with complex structure based on photon-enhanced thermionic emission is developed by utilizing one-dimensional steady-state continuity equations. The cathode structure comprises a graded-composition AlxGa1-xAs window layer and an exponential-doping GaAs absorber layer. In the deduced model, the physical properties changing with the Al composition are taken into consideration. Simulated current-voltage characteristics are presented and some important factors affecting the conversion efficiency are also illustrated. Compared with the graded-composition and uniform-doping cathode structure, and the uniform-composition and uniform-doping cathode structure, the graded-composition and exponential-doping cathode structure can effectively improve the conversion efficiency, which is ascribed to the twofold built-in electric fields. More strikingly, this graded bandgap structure is especially suitable for photon-enhanced thermionic emission devices since a higher conversion efficiency can be achieved at a lower temperature.

Band Structure Characteristics of Nacreous Composite Materials with Various Defects

NASA Astrophysics Data System (ADS)

Yin, J.; Zhang, S.; Zhang, H. W.; Chen, B. S.

2016-06-01

Nacreous composite materials have excellent mechanical properties, such as high strength, high toughness, and wide phononic band gap. In order to research band structure characteristics of nacreous composite materials with various defects, supercell models with the Brick-and-Mortar microstructure are considered. An efficient multi-level substructure algorithm is employed to discuss the band structure. Furthermore, two common systems with point and line defects and varied material parameters are discussed. In addition, band structures concerning straight and deflected crack defects are calculated by changing the shear modulus of the mortar. Finally, the sensitivity of band structures to the random material distribution is presented by considering different volume ratios of the brick. The results reveal that the first band gap of a nacreous composite material is insensitive to defects under certain conditions. It will be of great value to the design and synthesis of new nacreous composite materials for better dynamic properties.

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

Ionic liquid-functionalized mesoporous sorbents and their use in the capture of polluting gases

DOEpatents

Lee, Jong Suk; Koros, William J.; Bhuwania, Nitesh; Hillesheim, Patrick C.; Dai, Sheng

2016-01-12

A composite structure for capturing a gaseous electrophilic species, the composite structure comprising mesoporous refractory sorbent particles on which an ionic liquid is covalently attached, wherein said ionic liquid includes an accessible functional group that is capable of binding to said gaseous electrophilic species. In particular embodiments, the mesoporous sorbent particles are contained within refractory hollow fibers. Also described is a method for capturing a gaseous electrophilic species by use of the above-described composite structure, wherein the gaseous electrophilic species is contacted with the composite structure. In particular embodiments thereof, cooling water is passed through the refractory hollow fibers containing the IL-functionalized sorbent particles in order to facilitate capture of the gaseous electrophilic species, and then steam is passed through the refractory hollow fibers to facilitate release of the gaseous electrophilic species such that the composite structure can be re-used to capture additional gas.

Characterization and manufacture of braided composites for large commercial aircraft structures

NASA Technical Reports Server (NTRS)

Fedro, Mark J.; Willden, Kurtis

1992-01-01

Braided composite materials, one of the advanced material forms which is under investigation in Boeing's ATCAS program, have been recognized as a potential cost-effective material form for fuselage structural elements. Consequently, there is a strong need for more knowledge in the design, manufacture, test, and analysis of textile structural composites. The overall objective of this work is to advance braided composite technology towards applications to a large commercial transport fuselage. This paper summarizes the mechanics of materials and manufacturing demonstration results which have been obtained in order to acquire an understanding of how braided composites can be applied to a commercial fuselage. Textile composites consisting of 1D, 2D triaxial, and 3D braid patterns with thermoplastic and two RTM resin systems were investigated. The structural performance of braided composites was evaluated through an extensive mechanical test program. Analytical methods were also developed and applied to predict the following: internal fiber architectures, stiffnesses, fiber stresses, failure mechanisms, notch effects, and the entire history of failure of the braided composites specimens. The applicability of braided composites to a commercial transport fuselage was further assessed through a manufacturing demonstration. Three foot fuselage circumferential hoop frames were manufactured to demonstrate the feasibility of consistently producing high quality braided/RTM composite primary structures. The manufacturing issues (tooling requirements, processing requirements, and process/quality control) addressed during the demonstration are summarized. The manufacturing demonstration in conjunction with the mechanical test results and developed analytical methods increased the confidence in the ATCAS approach to the design, manufacture, test, and analysis of braided composites.

Composite sandwich lattice structure

NASA Technical Reports Server (NTRS)

Rhodes, M. D. (Inventor); Mikulas, M. M., Jr.

1977-01-01

A lattice type structural panel is described. The panel utilizes the unidirectional character of filamentary epoxy impregnated composites. The panels are stiff lightweight structures for use in constructing space satellites and the like.

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.

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

Structural characteristics of biochar-graphene nanosheet composites and their adsorption performance for phthalic acid esters

NASA Astrophysics Data System (ADS)

Ghaffar, Abdul; Zhu, Xiaoying; Chen, Baoliang

2017-04-01

The nonuniform and unhomogenous structure of biochar including defects could affect the adsorption performance of biochars. Biochar and graphene nanosheet (GNS) composites (BG) were prepared by simple dip coating method following thermal route of bamboo wood biomass at three different temperatures (300, 500, 700°C), in addition to biochars. The morphology and structural composition of biochars and BG composites were examined by scanning electron microscopy, transmission electron microscopy, Brunauer-Emmet-Teller surface area with N2 and CO2, Raman spectroscopy, Fourier Transformed Infrared spectroscopy, X-ray Photoelectron spectroscopy, Thermogravimetric analysis and CHN elemental analysis. It was found that GNS ( 1µm, 0.1% mass) provided higher thermal stability, porous structure, and relatively higher surface area (N2 and CO2), to BG composites. BG composites portrayed the existence of GNS bearing cavities and evidently increased the graphitic structure. The adsorption capabilities of biochars and BG composites towards dimethyl phthalate (DMP), diethyl phthalate (DEP), and dibutyl phthalate (DBP) as model phthalic acid esters (PAEs) were examined by batch sorption technique. The BG composites exhibited the increased adsorption capacity comparatively to biochars. The aromatic sheets of biochars and GNS on biochars dominated the π-π EDA (electron donor-acceptor) interaction for ring structure of DMP molecule in addition to pore-diffusion mechanism, whereas adsorption of DBP was attributed to hydrophobicity. Our results suggest that surface composition and morphology of biochars can be regulated with GNS and may enhance their adsorption capacity, thus could be considered for effective environmental remediation of various organic contaminants.

Advanced composite structural concepts and material technologies for primary aircraft structures

NASA Technical Reports Server (NTRS)

Jackson, Anthony

1991-01-01

Structural weight savings using advanced composites have been demonstrated for many years. Most military aircraft today use these materials extensively and Europe has taken the lead in their use in commercial aircraft primary structures. A major inhibiter to the use of advanced composites in the United States is cost. Material costs are high and will remain high relative to aluminum. The key therefore lies in the significant reduction in fabrication and assembly costs. The largest cost in most structures today is assembly. As part of the NASA Advanced Composite Technology Program, Lockheed Aeronautical Systems Company has a contract to explore and develop advanced structural and manufacturing concepts using advanced composites for transport aircraft. Wing and fuselage concepts and related trade studies are discussed. These concepts are intended to lower cost and weight through the use of innovative material forms, processes, structural configurations and minimization of parts. The approach to the trade studies and the downselect to the primary wing and fuselage concepts is detailed. The expectations for the development of these concepts is reviewed.

Tunable multi-band absorption in metasurface of graphene ribbons based on composite structure

NASA Astrophysics Data System (ADS)

Ning, Renxia; Jiao, Zheng; Bao, Jie

2017-05-01

A tunable multiband absorption based on a graphene metasurface of composite structure at mid-infrared frequency was investigated by the finite difference time domain method. The composite structure were composed of graphene ribbons and a gold-MgF2 layer which was sandwiched in between two dielectric slabs. The permittivity of graphene is discussed with different chemical potential to obtain tunable absorption. And the absorption of the composite structure can be tuned by the chemical potential of graphene at certain frequencies. The impedance matching was used to study the perfect absorption of the structure in our paper. The results show that multi-band absorption can be obtained and some absorption peaks of the composite structure can be tuned through the changing not only of the width of graphene ribbons and gaps, but also the dielectric and the chemical potential of graphene. However, another peak was hardly changed by parameters due to a different resonant mechanism in proposed structure. This flexibily tunable multiband absorption may be applied to optical communications such as optical absorbers, mid infrared stealth devices and filters.

Spirally Structured Conductive Composites for Highly Stretchable, Robust Conductors and Sensors.

PubMed

Wu, Xiaodong; Han, Yangyang; Zhang, Xinxing; Lu, Canhui

2017-07-12

Flexible and stretchable electronics are highly desirable for next generation devices. However, stretchability and conductivity are fundamentally difficult to combine for conventional conductive composites, which restricts their widespread applications especially as stretchable electronics. Here, we innovatively develop a new class of highly stretchable and robust conductive composites via a simple and scalable structural approach. Briefly, carbon nanotubes are spray-coated onto a self-adhesive rubber film, followed by rolling up the film completely to create a spirally layered structure within the composites. This unique spirally layered structure breaks the typical trade-off between stretchability and conductivity of traditional conductive composites and, more importantly, restrains the generation and propagation of mechanical microcracks in the conductive layer under strain. Benefiting from such structure-induced advantages, the spirally layered composites exhibit high stretchability and flexibility, good conductive stability, and excellent robustness, enabling the composites to serve as highly stretchable conductors (up to 300% strain), versatile sensors for monitoring both subtle and large human activities, and functional threads for wearable electronics. This novel and efficient methodology provides a new design philosophy for manufacturing not only stretchable conductors and sensors but also other stretchable electronics, such as transistors, generators, artificial muscles, etc.

In-situ poling and structurization of piezoelectric particulate composites.

PubMed

Khanbareh, H; van der Zwaag, S; Groen, W A

2017-11-01

Composites of lead zirconate titanate particles in an epoxy matrix are prepared in the form of 0-3 and quasi 1-3 with different ceramic volume contents from 10% to 50%. Two different processing routes are tested. Firstly a conventional dielectrophoretic structuring is used to induce a chain-like particle configuration, followed by curing the matrix and poling at a high temperature and under a high voltage. Secondly a simultaneous combination of dielectrophoresis and poling is applied at room temperature while the polymer is in the liquid state followed by subsequent curing. This new processing route is practiced in an uncured thermoset system while the polymer matrix still possess a relatively high electrical conductivity. Composites with different degrees of alignment are produced by altering the magnitude of the applied electric field. A significant improvement in piezoelectric properties of quasi 1-3 composites can be achieved by a combination of dielectrophoretic alignment of the ceramic particles and poling process. It has been observed that the degree of structuring as well as the functional properties of the in-situ structured and poled composites enhance significantly compared to those of the conventionally manufactured structured composites. Improving the alignment quality enhances the piezoelectric properties of the particulate composites.

Buckling Design and Imperfection Sensitivity of Sandwich Composite Launch-Vehicle Shell Structures

NASA Technical Reports Server (NTRS)

Schultz, Marc R.; Sleight, David W.; Myers, David E.; Waters, W. Allen, Jr.; Chunchu, Prasad B.; Lovejoy, Andrew W.; Hilburger, Mark W.

2016-01-01

Composite materials are increasingly being considered and used for launch-vehicle structures. For shell structures, such as interstages, skirts, and shrouds, honeycomb-core sandwich composites are often selected for their structural efficiency. Therefore, it is becoming increasingly important to understand the structural response, including buckling, of sandwich composite shell structures. Additionally, small geometric imperfections can significantly influence the buckling response, including considerably reducing the buckling load, of shell structures. Thus, both the response of the theoretically perfect structure and the buckling imperfection sensitivity must be considered during the design of such structures. To address the latter, empirically derived design factors, called buckling knockdown factors (KDFs), were developed by NASA in the 1960s to account for this buckling imperfection sensitivity during design. However, most of the test-article designs used in the development of these recommendations are not relevant to modern launch-vehicle constructions and material systems, and in particular, no composite test articles were considered. Herein, a two-part study on composite sandwich shells to (1) examine the relationship between the buckling knockdown factor and the areal mass of optimized designs, and (2) to interrogate the imperfection sensitivity of those optimized designs is presented. Four structures from recent NASA launch-vehicle development activities are considered. First, designs optimized for both strength and stability were generated for each of these structures using design optimization software and a range of buckling knockdown factors; it was found that the designed areal masses varied by between 6.1% and 19.6% over knockdown factors ranging from 0.6 to 0.9. Next, the buckling imperfection sensitivity of the optimized designs is explored using nonlinear finite-element analysis and the as-measured shape of a large-scale composite cylindrical shell. When compared with the current buckling design recommendations, the results suggest that the current recommendations are overly conservative and that the development of new recommendations could reduce the acreage areal mass of many composite sandwich shell designs by between 4% and 19%, depending on the structure.

Progressive Fracture of Composite Structures

NASA Technical Reports Server (NTRS)

Minnetyan, Levon

2001-01-01

This report includes the results of a research in which the COmposite Durability STRuctural ANalysis (CODSTRAN) computational simulation capabilities were augmented and applied to various structures for demonstration of the new features and verification. The first chapter of this report provides an introduction to the computational simulation or virtual laboratory approach for the assessment of damage and fracture progression characteristics in composite structures. The second chapter outlines the details of the overall methodology used, including the failure criteria and the incremental/iterative loading procedure with the definitions of damage, fracture, and equilibrium states. The subsequent chapters each contain an augmented feature of the code and/or demonstration examples. All but one of the presented examples contains laminated composite structures with various fiber/matrix constituents. For each structure simulated, damage initiation and progression mechanisms are identified and the structural damage tolerance is quantified at various degradation stages. Many chapters contain the simulation of defective and defect free structures to evaluate the effects of existing defects on structural durability.

Dispersion of Lamb waves in a honeycomb composite sandwich panel.

PubMed

Baid, Harsh; Schaal, Christoph; Samajder, Himadri; Mal, Ajit

2015-02-01

Composite materials are increasingly being used in advanced aircraft and aerospace structures. Despite their many advantages, composites are often susceptible to hidden damages that may occur during manufacturing and/or service of the structure. Therefore, safe operation of composite structures requires careful monitoring of the initiation and growth of such defects. Ultrasonic methods using guided waves offer a reliable and cost effective method for defects monitoring in advanced structures due to their long propagation range and their sensitivity to defects in their propagation path. In this paper, some of the useful properties of guided Lamb type waves are investigated, using analytical, numerical and experimental methods, in an effort to provide the knowledge base required for the development of viable structural health monitoring systems for composite structures. The laboratory experiments involve a pitch-catch method in which a pair of movable transducers is placed on the outside surface of the structure for generating and recording the wave signals. The specific cases considered include an aluminum plate, a woven composite laminate and an aluminum honeycomb sandwich panel. The agreement between experimental, numerical and theoretical results are shown to be excellent in certain frequency ranges, providing a guidance for the design of effective inspection systems. Copyright © 2014 Elsevier B.V. All rights reserved.

Study Acoustic Emissions from Composites

NASA Technical Reports Server (NTRS)

Walker, James; Workman,Gary

1998-01-01

The purpose of this work will be to develop techniques for monitoring the acoustic emissions from carbon epoxy composite structures at cryogenic temperatures. Performance of transducers at temperatures ranging from ambient to cryogenic and the characteristics of acoustic emission from composite structures will be studied and documented. This entire effort is directed towards characterization of structures used in NASA propulsion programs such as the X-33.

An Assessment of the State-of-the-Art in the Design and Manufacturing of Large Composite Structures for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Harris, Charles E.; Shuart, Mark J.

2001-01-01

An assessment of the State-of-the-Art in the design and manufacturing of large composite structures has been conducted. The focus of the assessment is large structural components in commercial and military aircraft. Applications of composites are reviewed for commercial transport aircraft, general aviation aircraft, rotorcraft, and military aircraft.

Innovative Composite Structure Design for Blast Protection

DTIC Science & Technology

2007-01-01

2007-01-0483 Innovative Composite Structure Design for Blast Protection Dongying Jiang, Yuanyuan Liu MKP Structural Design Associates, Inc...protect vehicle and occupants against various explosives. The multi-level and multi-scenario blast simulation and design system integrates three major...numerical simulation of a BTR composite under a blast event. The developed blast simulation and design system will enable the prediction, design, and

Eighth DOD/NASA/FAA Conference on Fibrous Composites in Structural Design, Part 2

NASA Technical Reports Server (NTRS)

Starnes, James H., Jr. (Compiler); Bohon, Herman L. (Compiler); Garzon, Sherry B. (Compiler)

1990-01-01

Papers presented at the conference are compiled. The conference provided a forum for the scientific community to exchange composite structures design information and an opportunity to observe recent progress in composite structures design and technology. Part 2 contains papers related to the following subject areas: the application in design; methodology in design; and reliability in design.

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.

Fabrication of submicron structures in nanoparticle/polymer composite by holographic lithography and reactive ion etching

NASA Astrophysics Data System (ADS)

Zhang, A. Ping; He, Sailing; Kim, Kyoung Tae; Yoon, Yong-Kyu; Burzynski, Ryszard; Samoc, Marek; Prasad, Paras N.

2008-11-01

We report on the fabrication of nanoparticle/polymer submicron structures by combining holographic lithography and reactive ion etching. Silica nanoparticles are uniformly dispersed in a (SU8) polymer matrix at a high concentration, and in situ polymerization (cross-linking) is used to form a nanoparticle/polymer composite. Another photosensitive SU8 layer cast upon the nanoparticle/SU8 composite layer is structured through holographic lithography, whose pattern is finally transferred to the nanoparticle/SU8 layer by the reactive ion etching process. Honeycomb structures in a submicron scale are experimentally realized in the nanoparticle/SU8 composite.

Thermography Inspection for Early Detection of Composite Damage in Structures During Fatigue Loading

NASA Technical Reports Server (NTRS)

Zalameda, Joseph N.; Burke, Eric R.; Parker, F. Raymond; Seebo, Jeffrey P.; Wright, Christopher W.; Bly, James B.

2012-01-01

Advanced composite structures are commonly tested under controlled loading. Understanding the initiation and progression of composite damage under load is critical for validating design concepts and structural analysis tools. Thermal nondestructive evaluation (NDE) is used to detect and characterize damage in composite structures during fatigue loading. A difference image processing algorithm is demonstrated to enhance damage detection and characterization by removing thermal variations not associated with defects. In addition, a one-dimensional multilayered thermal model is used to characterize damage. Lastly, the thermography results are compared to other inspections such as non-immersion ultrasonic inspections and computed tomography X-ray.

Enhanced dielectric standoff and mechanical failure in field-structured composites

NASA Astrophysics Data System (ADS)

Martin, James E.; Tigges, Chris P.; Anderson, Robert A.; Odinek, Judy

1999-09-01

We report dielectric breakdown experiments on electric-field-structured composites of high-dielectric-constant BaTiO3 particles in an epoxy resin. These experiments show a significant increase in the dielectric standoff strength perpendicular to the field structuring direction, relative to control samples consisting of randomly dispersed particles. To understand the relation of this observation to microstructure, we apply a simple resistor-short breakdown model to three-dimensional composite structures generated from a dynamical simulation. In this breakdown model the composite material is assumed to conduct primarily through particle contacts, so the simulated structures are mapped onto a resistor network where the center of mass of each particle is a node that is connected to neighboring nodes by resistors of fixed resistance that irreversibly short to perfect conductors when the current reaches a threshold value. This model gives relative breakdown voltages that are in good agreement with experimental results. Finally, we consider a primitive model of the mechanical strength of a field-structured composite material, which is a current-driven, conductor-insulator fuse model. This model leads to a macroscopic fusing behavior and can be related to mechanical failure of the composite.

Temperature and composition dependence of Mg-based amorphous-alloy structure factors

NASA Astrophysics Data System (ADS)

From, M.; Muir, W. B.

1992-01-01

Measurements of the x-ray total structure factors for amorphous Mg70Zn30, Ca70Mg30, and Mg85.5Cu14.5 at 9, 150, and 300 K have been made. The composition dependence of the room-temperature structure factors of MgxZn1-x have also been measured for values of x=0.65, 0.70, and 0.75. These compositional changes can be accounted for by the increase in average atomic size as the fraction of the larger Mg atoms increases with x. Also the Perkus-Yevick hard-sphere model is sufficient to calculate the change in structure factor with composition if an experimental structure factor is available from which the sphere diameters and packing fraction can be extracted. The temperature dependence of the structure factors is consistent with the observed thermal expansion and a Debye phonon model with Meisel and Cote's approximation for the multiphonon contribution to the structure factor.

Structural and compositional features of high-rise buildings: experimental design in Yekaterinburg

NASA Astrophysics Data System (ADS)

Yankovskaya, Yulia; Lobanov, Yuriy; Temnov, Vladimir

2018-03-01

The study looks at the specifics of high-rise development in Yekaterinburg. High-rise buildings are considered in the context of their historical development, structural features, compositional and imaginative design techniques. Experience of Yekaterinburg architects in experimental design is considered and analyzed. Main issues and prospects of high-rise development within the Yekaterinburg structure are studied. The most interesting and significant conceptual approaches to the structural and compositional arrangement of high-rise buildings are discussed.

Structural behavior of composites with progressive fracture

NASA Technical Reports Server (NTRS)

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

1989-01-01

The objective of the study is to unify several computational tools developed for the prediction of progressive damage and fracture with efforts for the prediction of the overall response of damaged composite structures. In particular, a computational finite element model for the damaged structure is developed using a computer program as a byproduct of the analysis of progressive damage and fracture. Thus, a single computational investigation can predict progressive fracture and the resulting variation in structural properties of angleplied composites.

Progress in composite structure and space construction systems technology

NASA Technical Reports Server (NTRS)

Bodle, J. B.; Jenkins, L. M.

1981-01-01

The development of deployable and fabricated composite trusses for large space structures by NASA and private industry is reviewed. Composite materials technology is discussed with a view toward fabrication processes and the characteristics of finished truss beams. Advances in roll-forming open section caps from graphite-composite strip material and new ultrasonic welding techniques are outlined. Vacuum- and gravity-effect test results show that the ultrasonic welding of graphite-thermoplastic materials in space is feasible. The structural characteristics of a prototype truss segment are presented. A new deployable graphite-composite truss with high packaging density for broad application to large space platforms is described.

Structural considerations in design of lightweight glass-fiber composite pressure vessels

NASA Technical Reports Server (NTRS)

Faddoul, J. R.

1973-01-01

The development of structurally efficient, metal-lined, glass-fiber composite pressure vessels. Both the current state-of-the-art and current problems are discussed along with fracture mechanics considerations for the metal liner. The design concepts used for metal-lined, glass-fiber, composite pressure vessels are described and the structural characteristics of the composite designs are compared with each other and with homogeneous metal pressure vessels. Specific design techniques and available design data are identified. Results of a current program to evaluate flaw growth and fracture characteristics of the metal liners are reviewed and the impact of these results on composite pressure vessel designs is discussed.

Free vibration of composite re-bars in reinforced structures

NASA Astrophysics Data System (ADS)

Kadioglu, Fethi

2005-11-01

The effect of composite rebar's shape in reinforced concrete beam-type structures on the natural frequencies and modes shapes is investigated through finite element analysis in this paper. Steel rebars are being replaced with composite rebars due to their better ability to resist corrosion in reinforced concrete structures for many infrastructure applications. A variety of composite rebar shapes can be obtained through the pultrusion process. It will be interesting to investigate their shape on free vibration characteristics. The results of natural frequencies and mode shapes are presented and compared for the different composite rebar shapes. The effects of various boundary conditions for different rebar shapes are also investigated.

Activated carbon fiber composite material and method of making

DOEpatents

Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

2000-01-01

An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

Activated carbon fiber composite material and method of making

DOEpatents

Burchell, Timothy D.; Weaver, Charles E.; Chilcoat, Bill R.; Derbyshire, Frank; Jagtoyen, Marit

2001-01-01

An activated carbon fiber composite for separation and purification, or catalytic processing of fluids is described. The activated composite comprises carbon fibers rigidly bonded to form an open, permeable, rigid monolith capable of being formed to near-net-shape. Separation and purification of gases are effected by means of a controlled pore structure that is developed in the carbon fibers contained in the composite. The open, permeable structure allows the free flow of gases through the monolith accompanied by high rates of adsorption. By modification of the pore structure and bulk density the composite can be rendered suitable for applications such as gas storage, catalysis, and liquid phase processing.

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

Li, Lidong; Zhou, Lu; Ould-Chikh, Samy

Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanningmore » transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. As a result, these catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.« less

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

Li, Lidong; Zhou, Lu; Ould-Chikh, Samy

The surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. Moreover, the evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annularmore » dark-field scanning transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. The catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.« less

Preparation of Desirable Porous Cell Structure Polylactide/Wood Flour Composite Foams Assisted by Chain Extender

PubMed Central

Wang, Youyong; Song, Yongming; Du, Jun; Xi, Zhenhao; Wang, Qingwen

2017-01-01

Polylactide (PLA)/wood flour composite foam were prepared through a batch foaming process. The effect of the chain extender on the crystallization behavior and dynamic rheological properties of the PLA/wood flour composites were investigated as well as the crystal structure and cell morphology of the composite foams. The incorporation of the chain extender enhanced the complex viscosity and storage modulus of PLA/wood flour composites, indicating the improved melt elasticity. The chain extender also led to a decreased crystallization rate and final crystallinity of PLA/wood flour composites. With an increasing chain extender content, a finer and more uniform cell structure was formed, and the expansion ratio of PLA/wood flour composite foams was much higher than without the chain extender. Compared to the unfoamed composites, the crystallinity of the foamed PLA/wood flour composites was improved and the crystal was loosely packed. However, the new crystalline form was not evident. PMID:28846604

A new biodegradable sisal fiber-starch packing composite with nest structure.

PubMed

Xie, Qi; Li, Fangyi; Li, Jianfeng; Wang, Liming; Li, Yanle; Zhang, Chuanwei; Xu, Jie; Chen, Shuai

2018-06-01

A new completely biodegradable sisal fiber-starch packing composite was proposed. The effects of fiber content and alkaline treatment on the cushioning property of the composites were studied from energy absorption efficiency, cellular microstructure and compatibility between fiber and starch. With increasing fiber content, the nest structure of composites becomes dense first and then loosens, resulting in initial enhancement and subsequent weakening of the cushioning property of the composites. The composite with 4:13 mass ratio of fiber and thermoplastic starch (TPS) exhibit the optimal cushioning property. Alkaline treatment increases the compatibility between sisal fiber and TPS, promotes the formation of dense nest structure, thereby enhances the cushioning property of the composites. After biodegradability tests for 28 days, the weight loss of the composites was 62.36%. It's found that the composites are a promising replacement for expandable polystyrene (EPS) as packing material, especially under large compression load (0.7-6 MPa). Copyright © 2018 Elsevier Ltd. All rights reserved.

Effects of oxygen plasma treatment power on Aramid fiber III/BMI composite humidity resistance properties

NASA Astrophysics Data System (ADS)

Wang, Jing; Shi, Chen; Feng, Jiayue; Long, Xi; Meng, Lingzhi; Ren, Hang

2018-01-01

The effects of oxygen plasma treatment power on Aramid Fiber III chemical structure and its reinforced bismaleimides (BMI) composite humidity resistance properties were investigated in this work. The aramid fiber III chemical structure under different plasma treatment power were measured by FTIR. The composite bending strength and interlinear shear strength with different plasma treatment power before and after absorption water were tested respectively. The composite rupture morphology was observed by SEM. The FTIR results showed that oxygen plasma treatment do not change the fiber bulk chemical structure. The composite humidity resistance of bending strength and interlinear shear strength are similar for untreated and plasma treated samples. The retention rate of composite bending strength and interlinear shear strength are about 75% and 94%, respectively. The composite rupture mode turns to be the fiber failure after water absorption.

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.

Lightweight composites for modular panelized construction

NASA Astrophysics Data System (ADS)

Vaidya, Amol S.

Rapid advances in construction materials technology have enabled civil engineers to achieve impressive gains in the safety, economy, and functionality of structures built to serve the common needs of society. Modular building systems is a fast-growing modern, form of construction gaining recognition for its increased efficiency and ability to apply modern technology to the needs of the market place. In the modular construction technique, a single structural panel can perform a number of functions such as providing thermal insulation, vibration damping, and structural strength. These multifunctional panels can be prefabricated in a manufacturing facility and then transferred to the construction site. A system that uses prefabricated panels for construction is called a "panelized construction system". This study focuses on the development of pre-cast, lightweight, multifunctional sandwich composite panels to be used for panelized construction. Two thermoplastic composite panels are proposed in this study, namely Composite Structural Insulated Panels (CSIPs) for exterior walls, floors and roofs, and Open Core Sandwich composite for multifunctional interior walls of a structure. Special manufacturing techniques are developed for manufacturing these panels. The structural behavior of these panels is analyzed based on various building design codes. Detailed descriptions of the design, cost analysis, manufacturing, finite element modeling and structural testing of these proposed panels are included in this study in the of form five peer-reviewed journal articles. The structural testing of the proposed panels involved in this study included flexural testing, axial compression testing, and low and high velocity impact testing. Based on the current study, the proposed CSIP wall and floor panels were found satisfactory, based on building design codes ASCE-7-05 and ACI-318-05. Joining techniques are proposed in this study for connecting the precast panels on the construction site. Keywords: Modular panelized construction, sandwich composites, composite structural insulated panels (CSIPs).

Fabrication of a smart air intake structure using shape memory alloy wire embedded composite

NASA Astrophysics Data System (ADS)

Jung, Beom-Seok; Kim, Min-Saeng; Kim, Ji-Soo; Kim, Yun-Mi; Lee, Woo-Yong; Ahn, Sung-Hoon

2010-05-01

Shape memory alloys (SMAs) have been actively studied in many fields utilizing their high energy density. Applying SMA wire-embedded composite to aerospace structures, such as air intake of jet engines and guided missiles, is attracting significant attention because it could generate a comparatively large actuating force. In this research, a scaled structure of SMA wire-embedded composite was fabricated for the air intake of aircraft. The structure was composed of several prestrained Nitinol (Ni-Ti) SMA wires embedded in ∩-shape glass fabric reinforced plastic (GFRP), and it was cured at room temperature for 72 h. The SMA wire-embedded GFRP could be actuated by applying electric current through the embedded SMA wires. The activation angle generated from the composite structure was large enough to make a smart air intake structure.

A Study of the Utilization of Advanced Composites in Fuselage Structures of Commercial Aircraft

NASA Technical Reports Server (NTRS)

Watts, D. J.; Sumida, P. T.; Bunin, B. L.; Janicki, G. S.; Walker, J. V.; Fox, B. R.

1985-01-01

A study was conducted to define the technology and data needed to support the introduction of advanced composites in the future production of fuselage structure in large transport aircraft. Fuselage structures of six candidate airplanes were evaluated for the baseline component. The MD-100 was selected on the basis of its representation of 1990s fuselage structure, an available data base, its impact on the schedule and cost of the development program, and its availability and suitability for flight service evaluation. Acceptance criteria were defined, technology issues were identified, and a composite fuselage technology development plan, including full-scale tests, was identified. The plan was based on composite materials to be available in the mid to late 1980s. Program resources required to develop composite fuselage technology are estimated at a rough order of magnitude to be 877 man-years exclusive of the bird strike and impact dynamic test components. A conceptual composite fuselage was designed, retaining the basic MD-100 structural arrangement for doors, windows, wing, wheel wells, cockpit enclosure, major bulkheads, etc., resulting in a 32 percent weight savings.

Coaxial-cable structure composite cathode material with high sulfur loading for high performance lithium-sulfur batteries

NASA Astrophysics Data System (ADS)

Li, Qiang; Zhang, Zhian; Guo, Zaiping; Zhang, Kai; Lai, Yanqing; Li, Jie

2015-01-01

Hollow carbon nanofiber@nitrogen-doped porous carbon (HCNF@NPC) coaxial-cable structure composite, which is carbonized from HCNF@polydopamine, is prepared as an improved high conductive carbon matrix for encapsulating sulfur as a composite cathode material for lithium-sulfur batteries. The prepared HCNF@NPC-S composite with high sulfur content of approximately 80 wt% shows an obvious coaxial-cable structure with an NPC layer coating on the surface of the linear HCNFs along the length and sulfur homogeneously distributes in the coating layer. This material exhibits much better electrochemical performance than the HCNF-S composite, delivers initial discharge capacity of 982 mAh g-1 and maintains a high capacity retention rate of 63% after 200 cycles at a high current density of 837.5 mA g-1. The significantly enhanced electrochemical performance of the HCNF@NPC-S composite is attributed to the unique coaxial-cable structure, in which the linear HCNF core provides electronic conduction pathways and works as mechanical support, and the NPC shell with nitrogen-doped and porous structure can trap sulfur/polysulfides and provide Li+ conductive pathways.

The pressure-induced structural response of rare earth hafnate and stannate pyrochlore from 0.1-50 GPa

NASA Astrophysics Data System (ADS)

Turner, K. M.; Rittman, D.; Heymach, R.; Turner, M.; Tracy, C.; Mao, W. L.; Ewing, R. C.

2017-12-01

Complex oxides with the pyrochlore (A2B2O7) and defect-fluorite ((A,B)4O7) structure-types undergo structural transformations under high-pressure. These compounds are under consideration for applications including as a proposed waste-form for actinides generated in the nuclear fuel cycle. High-pressure transformations in rare earth hafnates (A2Hf2O7, A=Sm, Eu, Gd, Dy, Y, Yb) and stannates (A2Sn2O7, A=Nd, Gd, Er) were investigated to 50 GPa by in situ Raman spectroscopy and synchrotron x-ray diffraction (XRD). Rare-earth hafnates form the pyrochlore structure for A=La-Tb and the defect-fluorite structure for A=Dy-Lu. Lanthanide stannates form the pyrochlore structure. Raman spectra revealed that at ambient pressure all compositions have pyrochlore-type short-range order. Stannate compositions show a larger degree of pyrochlore-type short-range ordering relative to hafnates. In situ high-pressure synchrotron XRD showed that rare earth hafnates and stannates underwent a pressure-induced phase transition to a cotunnite-like (Pnma) structure that begins between 18-25 GPa in hafnates and between 30-33 GPa in stannates. The phase transition is not complete at 50 GPa, and upon decompression, XRD indicates that all compositions transform to defect-fluorite with an amorphous component. In situ Raman spectroscopy showed that disordering in stannates and hafnates occurs gradually upon compression. Pyrochlore-structured hafnates retain short-range order to a higher pressure (30 GPa vs. <10 GPa) than defect-fluorite-structured hafnates. Hafnates and stannates decompressed from 50 GPa show Raman spectra consistent with weberite-type structures, also reported in irradiated stannates. The second-order Birch-Murnaghan equation of state fit gives a bulk modulus of 250 GPa for hafnate compositions with the pyrochlore structure, and 400 GPa for hafnate compositions with the defect-fluorite structure. Stannates have a lower bulk modulus relative to hafnates (between 80-150 GPa). Stannate and hafnate pyrochlore compositions taken to high pressure show structural transformations consistent with irradiated pyrochlore, and compositionally disordered pyrochlore: a long-range structure best described by defect-fluorite, and a short-range structure best described by weberite.

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.

Advanced composites technology program

NASA Technical Reports Server (NTRS)

Davis, John G., Jr.

1993-01-01

This paper provides a brief overview of the NASA Advanced Composites Technology (ACT) Program. Critical technology issues that must be addressed and solved to develop composite primary structures for transport aircraft are delineated. The program schedule and milestones are included. Work completed in the first 3 years of the program indicates the potential for achieving composite structures that weigh less and are cost effective relative to conventional aluminum structure. Selected technical accomplishments are noted. Readers who are seeking more in-depth technical information should study the other papers included in these proceedings.

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

NASA Technical Reports Server (NTRS)

Grant, J.; Kaul, R.; Taylor, S.; Jackson, K.; Sharma, A.; Burdine, Robert V. (Technical Monitor)

2002-01-01

Fiber Bragg-gratings are embedded in carbon-epoxy laminates as well as bonded on the surface of cylindrical structures fabricated out of such composites. Structural properties of such composites is investigated. The measurements include stress-strain relation in laminates and Poisson's ratio in several specimens with varying orientation of the optical fiber Bragg-sensor with respect to the carbon fiber in an epoxy matrix. Additionally, Bragg gratings are bonded on the surface of cylinders fabricated out of carbon-epoxy composites and longitudinal and hoop strain on the surface is measured.

Structural investigation of a new composite process

NASA Astrophysics Data System (ADS)

Mayer, Philippe; Becker, Eric; Bigot, Régis; Kaïci, Bruno

2017-10-01

This work presents a study done on a new patented forming process, created to produce massive composite parts used for structural applications in automotive and aeronautics industries. The study presented in this paper deals with an experimental setup, used to characterize thick composite cylinders. The author presents the characterization of these cylinders and a new analysis method, in order to understand the consolidation steps of the composite in this forming process. The structural health of the part is illustrated by the analysis of the intra-bundle and inter-bundle porosities, by micrographs characterizations.

Protection of Advanced Electrical Power Systems from Atmospheric Electromagnetic Hazards.

DTIC Science & Technology

1981-12-01

WORDS (Continue on reverse aide if neceeary and Identify by block number) Aircraft Induced Voltages Filters Composite Structures Lightning Transients...transients on the electrical systems of aircraft with metal or composite structures. These transients will be higher than the equipment inherent hardness... composite material in skin and structure. In addition, the advanced electrical power systems used in these aircraft will contain solid state components

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.

Fracture modes in notched angleplied composite laminates

NASA Technical Reports Server (NTRS)

Irvine, T. B.; Ginty, C. A.

1984-01-01

The Composite Durability Structural Analysis (CODSTRAN) computer code is used to determine composite fracture. Fracture modes in solid and notched, unidirectional and angleplied graphite/epoxy composites were determined by using CODSTRAN. Experimental verification included both nondestructive (ultrasonic C-Scanning) and destructive (scanning electron microscopy) techniques. The fracture modes were found to be a function of ply orientations and whether the composite is notched or unnotched. Delaminations caused by stress concentrations around notch tips were also determined. Results indicate that the composite mechanics, structural analysis, laminate analysis, and fracture criteria modules embedded in CODSTRAN are valid for determining composite fracture modes.

The Packaging Technology Study on Smart Composite Structure Based on The Embedded FBG Sensor

NASA Astrophysics Data System (ADS)

Zhang, Youhong; Chang, Xinlong; Zhang, Xiaojun; He, Xiangyong

2018-03-01

It is convenient to carry out the health monitoring of the solid rocket engine composite shell based on the embedded FBG sensor. In this paper, the packaging technology using one-way fiber layer of prepreg fiberglass/epoxy resin was proposed. The proposed packaging process is simple, and the packaged sensor structure size is flexible and convenient to use, at the mean time, the packaged structure has little effect on the pristine composite material structure.

Examining the Relationship Between Ballistic and Structural Properties of Lightweight Thermoplastic Unidirectional Composite Laminates

DTIC Science & Technology

2011-08-01

Kevlar KM2® Style 705 PVB phenolic woven aramid composite was included. A developmental unidirectional thermoplastic aramid fiber, Honeywell...Examining the Relationship Between Ballistic and Structural Properties of Lightweight Thermoplastic Unidirectional Composite Laminates by...Unidirectional Composite Laminates Lionel R. Vargas-Gonzalez, Shawn M. Walsh, and James C. Gurganus Weapons and Materials Research Directorate, ARL

The effect of carbon black loading and structure on tensile property of natural rubber composite

NASA Astrophysics Data System (ADS)

Savetlana, S.; Zulhendri; Sukmana, I.; Saputra, F. A.

2017-07-01

Natural rubber composite has been continuously developed due to its advantages such as a good combination of strength and damping property. Most of carbon black (CB)/Natural Rubber (NR) composite were used as material in tyre industry. The addition of CB in natural rubber is very important to enhance the strength of natural rubber. The particle loading and different structure of CB can affect the composite strength. The effects of CB particle loading of 20, 25 and 30 wt% and the effects of CB structures of N220, N330, N550 and N660 series on tensile property of composite were investigated. The result shows that the tensile strength and elastic modulus of natural rubber/CB composite was higher than pure natural rubber. From SEM observation the agglomeration of CB aggregate increases with particle loading. It leads to decrease of tensile strength of composite as more particle was added. High structure of CB particle i.e. N220 resulted in highest tensile stress. In fact, composite reinforced by N660 CB particle shown a comparable tensile strength and elastic modulus with N220 CB particle. SEM observation shows that agglomeration of CB aggregates of N330 and N550 results in lower stress of associate NR/CB composite.

Aligned macroporous TiO2/chitosan/reduced graphene oxide (rGO) composites for photocatalytic applications

NASA Astrophysics Data System (ADS)

Chen, Chao; Zhang, Yan; Zeng, Jing; Zhang, Fuqiang; Zhou, Kechao; Bowen, Chris R.; Zhang, Dou

2017-12-01

In this article ice templating is used to fabricate novel TiO2/chitosan/reduced graphene oxide (rGO) composites with a highly aligned macroporous structure for photocatalytic applications. The structure of the composites was readily tailored using the composite composition, for example the lamellar pore width decreased from 50-45 to 5-10 μm, while the lamellar thickness increased from 2-3 to 20-25 μm, with an increase of the TiO2 content from 45 to 77 vol%. Lamellar pore channels between the layers exhibited a more uniform distribution when the rGO content was 1.0 wt%. The increase in viscosity of the composites with high TiO2 contents led to the formation of smaller ice crystals and smaller lamellar pore sizes to enable the production of composite structures with improved mechanical strength. The TiO2/chitosan/rGO composites exhibited excellent photocatalytic degradation of methyl orange and the photocatalytic efficiency was optimized by control of the active material content and microstructure. The hybrid composites with 1.0 wt% rGO showed a degradation percentage of 97%, which makes these novel TiO2/chitosan/rGO freeze cast structures attractive materials as high performance and high strength substrates for photocatalytic degradation applications.

Composite Development and Applications for RLV Tankage

NASA Technical Reports Server (NTRS)

Wright, Richard J.; Achary, David C.; McBain, Michael C.

2003-01-01

The development of polymer composite cryogenic tanks is a critical step in creating the next generation of launch vehicles. Future launch vehicles need to minimize the gross liftoff weight (GLOW), which is possible due to the 28%-41% reduction in weight that composite materials can provide over current aluminum technology. The development of composite cryogenic tanks, feedlines, and unpressurized structures are key enabling technologies for performance and cost enhancements for Reusable Launch Vehicles (RLVs). The technology development of composite tanks has provided direct and applicable data for feedlines, unpressurized structures, material compatibility, and cryogenic fluid containment for highly loaded complex structures and interfaces. All three types of structure have similar material systems, processing parameters, scaling issues, analysis methodologies, NDE development, damage tolerance, and repair scenarios. Composite cryogenic tankage is the most complex of the 3 areas and provides the largest breakthrough in technology. A building block approach has been employed to bring this family of difficult technologies to maturity. This approach has built up composite materials, processes, design, analysis and test methods technology through a series of composite test programs beginning with the NASP program to meet aggressive performance goals for reusable launch vehicles. In this paper, the development and application of advanced composites for RLV use is described.

Structural, dielectric and ferroelectric studies of BZT doped Mg0.2Cu0.3Zn0.5Fe2O4 magnetoelectric composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Parveez, Asiya; Giridharan, N. V.; Sankarappa, T.

2018-05-01

The composites of ferrite-ferroelectric system (x) Mg0.2Cu0.3Zn0.5Fe2O4+ (1-x) Ba0.8Zr0.2TiO3 (x=15%, 30%, 45%) were synthesized by sintering mixtures of ferroelectric Ba0.8Zr0.2TiO3 (BZT) and ferrite component Mg0.2Cu0.3Zn0.5Fe2O4 (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The ferroelectric properties of synthesized composites were analyzed using a Precision ferroelectric tester. It is observed that the composites exhibited ferroelectric hysteresis with wide loops indicating lossy nature of composites.

Potential of Organic Matrix Composites for Liquid Oxygen Tank

NASA Technical Reports Server (NTRS)

Davis, Samuel E.; Herald, Stephen D.; Stolzfus, Joel M.; Engel, Carl D.; Bohlen, James W.; Palm, Tod; Robinson, Michael J.

2005-01-01

Composite materials are being considered for the tankage of cryogenic propellants in access to space because of potentially lower structural weights. A major hurdle for composites is an inherent concern about the safety of using flammable structural materials in contact with liquid and gaseous oxygen. A hazards analysis approach addresses a series of specific concerns that must be addressed based upon test data. Under the 2nd Generation Reusable Launch Vehicle contracts, testing was begun for a variety of organic matrix composite materials both to aid in the selection of materials and to provide needed test data to support hazards analyses. The work has continued at NASA MSFC and the NASA WSTF to provide information on the potential for using composite materials in oxygen systems. Appropriate methods for oxygen compatibility testing of structural materials and data for a range of composite materials from impact, friction, flammability and electrostatic discharge testing are presented. Remaining concerns and conclusions about composite tank structures, and recommendations for additional testing are discussed. Requirements for system specific hazards analysis are identified.

Nacre biomimetic design--a possible approach to prepare low infrared emissivity composite coatings.

PubMed

Zhang, Weigang; Xu, Guoyue; Ding, Ruya; Duan, Kaige; Qiao, Jialiang

2013-01-01

Mimicking the highly organized brick-and-mortar structure of nacre, a kind of nacre-like organic-inorganic composite material of polyurethane (PU)/flaky bronze composite coatings with low infrared emissivity was successfully designed and prepared by using PU and flaky bronze powders as adhesives and pigments, respectively. The infrared emissivity and microstructure of the coatings were systematically investigated by infrared emissometer and scanning electron microscopy, respectively, and the cause of low infrared emissivity of the coatings was discussed by using the theories of one-dimensional photonic structure. The results show that the infrared emissivity of the nacre-like PU/flaky bronze composite coatings can be as low as 0.206 at the bronze content of 60 wt. %, and it is significantly lower than the value of PU/sphere bronze composite coatings. Microstructure observation illustrated that the nacre-like PU/flaky bronze composite coatings have similar one-dimensional photonic structural characteristics. The low infrared emissivity of PU/flaky bronze composite coatings is derived from the similar one-dimensional photonic structure in the coatings. Copyright © 2012 Elsevier B.V. All rights reserved.

Failure Analysis in Platelet Molded Composite Systems

NASA Astrophysics Data System (ADS)

Kravchenko, Sergii G.

Long-fiber discontinuous composite systems in the form of chopped prepreg tapes provide an advanced, structural grade, molding compound allowing for fabrication of complex three-dimensional components. Understanding of process-structure-property relationship is essential for application of prerpeg platelet molded components, especially because of their possible irregular disordered heterogeneous morphology. Herein, a structure-property relationship was analyzed in the composite systems of many platelets. Regular and irregular morphologies were considered. Platelet-based systems with more ordered morphology possess superior mechanical performance. While regular morphologies allow for a careful inspection of failure mechanisms derived from the morphological characteristics, irregular morphologies are representative of the composite architectures resulting from uncontrolled deposition and molding with chopped prerpegs. Progressive failure analysis (PFA) was used to study the damaged deformation up to ultimate failure in a platelet-based composite system. Computational damage mechanics approaches were utilized to conduct the PFA. The developed computational models granted understanding of how the composite structure details, meaning the platelet geometry and system morphology (geometrical arrangement and orientation distribution of platelets), define the effective mechanical properties of a platelet-molded composite system, its stiffness, strength and variability in properties.

Composite laminate failure parameter optimization through four-point flexure experimentation and analysis

DOE PAGES

Nelson, Stacy; English, Shawn; Briggs, Timothy

2016-05-06

Fiber-reinforced composite materials offer light-weight solutions to many structural challenges. In the development of high-performance composite structures, a thorough understanding is required of the composite materials themselves as well as methods for the analysis and failure prediction of the relevant composite structures. However, the mechanical properties required for the complete constitutive definition of a composite material can be difficult to determine through experimentation. Therefore, efficient methods are necessary that can be used to determine which properties are relevant to the analysis of a specific structure and to establish a structure's response to a material parameter that can only be definedmore » through estimation. The objectives of this paper deal with demonstrating the potential value of sensitivity and uncertainty quantification techniques during the failure analysis of loaded composite structures; and the proposed methods are applied to the simulation of the four-point flexural characterization of a carbon fiber composite material. Utilizing a recently implemented, phenomenological orthotropic material model that is capable of predicting progressive composite damage and failure, a sensitivity analysis is completed to establish which material parameters are truly relevant to a simulation's outcome. Then, a parameter study is completed to determine the effect of the relevant material properties' expected variations on the simulated four-point flexural behavior as well as to determine the value of an unknown material property. This process demonstrates the ability to formulate accurate predictions in the absence of a rigorous material characterization effort. Finally, the presented results indicate that a sensitivity analysis and parameter study can be used to streamline the material definition process as the described flexural characterization was used for model validation.« less

Giant magnetoelectric effect in negative magnetostrictive/piezoelectric/positive magnetostrictive semiring structure

NASA Astrophysics Data System (ADS)

Zeng, Lingyu; Zhou, Minhong; Bi, Ke; Lei, Ming

2016-01-01

Magnetoelectric (ME) Ni/PZT/TbFe2 and TbFe2/PZT composites with two semiring structures are prepared. The dependence between ME coupling and magnetostrictive property of the composite is discussed. Because Ni possesses negative magnetostrictive property and TbFe2 shows positive magnetostrictive property, the ME voltage coefficient of Ni/PZT/TbFe2 semiring structure is much larger than that of TbFe2/PZT. In these composites, the ME voltage coefficient increases and the resonance frequency gradually decreases with the increase of the semiring radius, showing that structural parameters are key factors to the composite properties. Due to the strong ME coupling effect, a giant ME voltage coefficient αE = 44.8 V cm-1 Oe-1 is obtained. This approach opens a way for the design of ME composites with giant ME voltage coefficient.

Test method development for structural characterization of fiber composites at high temperatures

NASA Technical Reports Server (NTRS)

Mandell, J. F.; Grande, D. H.; Edwards, B.

1985-01-01

Test methods used for structural characterization of polymer matrix composites can be applied to glass and ceramic matrix composites only at low temperatures. New test methods are required for tensile, compressive, and shear properties of fiber composites at high temperatures. A tensile test which should be useful to at least 1000 C has been developed and used to characterize the properties of a Nicalon/glass composite up to the matrix limiting temperature of 600 C. Longitudinal and transverse unidirectional composite data are presented and discussed.

Navy composite maintenance and repair experience

NASA Technical Reports Server (NTRS)

Donnellan, T. M.; Cochran, R. C.; Rosenzweig, E. L.; Trabocco, R. E.

1992-01-01

The Navy has been a strong proponent of composites for aircraft structure. Fleet use of composites started with the F-14 in the early 1970's and has steadily increased. This experience base provides sufficient information to allow an evaluation of the maintenance performance of polymer composites in service. A summary is presented of the Navy's experience with maintenance of composite structure. The general types of damage experienced in the fleet as well as specific examples of composite damage to aircraft is described. The impact of future designs on supportability is also discussed.

Composite armored vehicle advanced technology demonstator

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

Ostberg, D.T.; Dunfee, R.S.; Thomas, G.E.

1996-12-31

Composite structures are a key technology needed to develop future lightweight combat vehicles that are both deployable and survivable. The Composite Armored Vehicle Advanced Technology Demonstrator Program that started in fiscal year 1994 will continue through 1998 to verily that composite structures are a viable solution for ground combat vehicles. Testing thus far includes material characterization, structural component tests and full scale quarter section tests. Material and manufacturing considerations, tests, results and changes, and the status of the program will be described. The structural component tests have been completed successfully, and quarter section testing is in progress. Upon completion ofmore » the critical design review, the vehicle demonstrator will be Fabricated and undergo government testing.« less

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.

Probabilistic Methods for Structural Reliability and Risk

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

2010-01-01

A probabilistic method is used to evaluate the structural reliability and risk of select metallic and composite structures. The method is a multiscale, multifunctional and it is based on the most elemental level. A multifactor interaction model is used to describe the material properties which are subsequently evaluated probabilistically. The metallic structure is a two rotor aircraft engine, while the composite structures consist of laminated plies (multiscale) and the properties of each ply are the multifunctional representation. The structural component is modeled by finite element. The solution method for structural responses is obtained by an updated simulation scheme. The results show that the risk for the two rotor engine is about 0.0001 and the composite built-up structure is also 0.0001.

Probabilistic Methods for Structural Reliability and Risk

NASA Technical Reports Server (NTRS)

Chamis, Christos C.

2008-01-01

A probabilistic method is used to evaluate the structural reliability and risk of select metallic and composite structures. The method is a multiscale, multifunctional and it is based on the most elemental level. A multi-factor interaction model is used to describe the material properties which are subsequently evaluated probabilistically. The metallic structure is a two rotor aircraft engine, while the composite structures consist of laminated plies (multiscale) and the properties of each ply are the multifunctional representation. The structural component is modeled by finite element. The solution method for structural responses is obtained by an updated simulation scheme. The results show that the risk for the two rotor engine is about 0.0001 and the composite built-up structure is also 0.0001.

Advanced organic composite materials for aircraft structures: Future program

NASA Technical Reports Server (NTRS)

1987-01-01

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

Study of chloride ion transport of composite by using cement and starch as a binder

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

Armynah, Bidayatul; Halide, Halmar; Zahrawani,

This study presents the chemical bonding and the structural properties of composites from accelerator chloride test migration (ACTM). The volume fractions between binder (cement and starch) and charcoal in composites are 20:80 and 60:40. The effect of the binder to the chemical composition, chemical bonding, and structural properties before and after chloride ion passing through the composites was determined by X-ray fluorescence (XRF), by Fourier transform infra-red (FTIR), and x-ray diffraction (XRD), respectively. From the XRD data, XRF data, and the FTIR data shows the amount of chemical composition, the type of binding, and the structure of composites are dependingmore » on the type of binder. The amount of chloride migration using starch as binder is higher than that of cement as a binder due to the density effects.« less

Facile fabrication and characterization of poly(tetrafluoroethylene)@polypyrrole/nano-silver composite membranes with conducting and antibacterial property

NASA Astrophysics Data System (ADS)

Shi, Zhiquan; Zhou, Hui; Qing, Xutang; Dai, Tingyang; Lu, Yun

2012-06-01

Porous poly(tetrafluoroethylene) (PTFE) membranes play an important role in air purification and separation engineering. To achieve the bi-functionality of conducting and antibacterial property, two kinds of poly(tetrafluoroethylene)@ polypyrrole/nano-silver composite membranes have been prepared. One involves hydrophobic polypyrrole/nano-silver composite with hollow capsule nanostructures immobilized on the surface of the PTFE membranes. The other is a type of composite membranes with polypyrrole/nano-silver composite wholly packed on the fibrils of the expand PTFE membrane to form core/shell coaxial cable structures. The structure and morphology of the two kinds of composite membranes have been characterized by FTIR, UV-vis, XRD, TGA and SEM measurements. Possible formation mechanisms of the hollow capsules and the core/shell nanocable structures have been discussed in detail. The antibacterial effects of composite membranes are also briefly investigated.

Polymeric dental composites based on remineralizing amorphous calcium phosphate fillers

PubMed Central

Skrtic, Drago; Antonucci, Joseph M.

2017-01-01

For over two decades we have systematically explored structure-composition-property relationships of amorphous calcium phosphate (ACP)-based polymeric dental composites. The appeal of these bioactive materials stems from their intrinsic ability to prevent demineralization and/or restore defective tooth structures via sustained release of remineralizing calcium and phosphate ions. Due to the compositional similarity of the ACP to biological tooth mineral, ACP-based composites should exhibit excellent biocompatibility. Research described in this article has already yielded remineralizing sealants and orthodontic adhesives as well as a prototype root canal sealer. Our work has also contributed to a better understanding on how polymer matrix structure and filler/matrix interactions affect the critical properties of these polymeric composites and their overall performance. The addition of antimicrobial compounds to the formulation of ACP composites could increase their medical and dental regenerative treatment applications, thereby benefiting an even greater number of patients. PMID:29599572

Synergetic Effect of Yolk-Shell Structure and Uniform Mixing of SnS-MoS₂ Nanocrystals for Improved Na-Ion Storage Capabilities.

PubMed

Choi, Seung Ho; Kang, Yun Chan

2015-11-11

Mixed metal sulfide composite microspheres with a yolk-shell structure for sodium-ion batteries are studied. Tin-molybdenum oxide yolk-shell microspheres prepared by a one-pot spray pyrolysis process transform into yolk-shell SnS-MoS2 composite microspheres. The discharge capacities of the yolk-shell and dense-structured SnS-MoS2 composite microspheres for the 100th cycle are 396 and 207 mA h g(-1), and their capacity retentions measured from the second cycle are 89 and 47%, respectively. The yolk-shell SnS-MoS2 composite microspheres with high structural stability during repeated sodium insertion and desertion processes have low charge-transfer resistance even after long-term cycling. The synergetic effect of the yolk-shell structure and uniform mixing of the SnS and MoS2 nanocrystals result in the excellent sodium-ion storage properties of the yolk-shell SnS-MoS2 composite microspheres by improving their structural stability during cycling.

Three-Axis Distributed Fiber Optic Strain Measurement in 3D Woven Composite Structures

NASA Technical Reports Server (NTRS)

Castellucci, Matt; Klute, Sandra; Lally, Evan M.; Froggatt, Mark E.; Lowry, David

2013-01-01

Recent advancements in composite materials technologies have broken further from traditional designs and require advanced instrumentation and analysis capabilities. Success or failure is highly dependent on design analysis and manufacturing processes. By monitoring smart structures throughout manufacturing and service life, residual and operational stresses can be assessed and structural integrity maintained. Composite smart structures can be manufactured by integrating fiber optic sensors into existing composite materials processes such as ply layup, filament winding and three-dimensional weaving. In this work optical fiber was integrated into 3D woven composite parts at a commercial woven products manufacturing facility. The fiber was then used to monitor the structures during a VARTM manufacturing process, and subsequent static and dynamic testing. Low cost telecommunications-grade optical fiber acts as the sensor using a high resolution commercial Optical Frequency Domain Reflectometer (OFDR) system providing distributed strain measurement at spatial resolutions as low as 2mm. Strain measurements using the optical fiber sensors are correlated to resistive strain gage measurements during static structural loading. Keywords: fiber optic, distributed strain sensing, Rayleigh scatter, optical frequency domain reflectometry

Structural Acoustic Physics Based Modeling of Curved Composite Shells

DTIC Science & Technology

2017-09-19

Results show that the finite element computational models accurately match analytical calculations, and that the composite material studied in this...products. 15. SUBJECT TERMS Finite Element Analysis, Structural Acoustics, Fiber-Reinforced Composites, Physics-Based Modeling 16. SECURITY...2 4 FINITE ELEMENT MODEL DESCRIPTION

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.

Thermal design of composite materials high temperature attachments

NASA Technical Reports Server (NTRS)

1972-01-01

The thermal aspects of using filamentary composite materials as primary airframe structures on advanced atmospheric entry spacecraft such as the space shuttle vehicle were investigated to identify and evaluate potential design approaches for maintaining composite structures within allowable temperature limits at thermal protection system (TPS) attachments and/or penetrations. The investigation included: (1) definition of thermophysical data for composite material structures; (2) parametric characterization and identification of the influence of the aerodynamic heating and attachment design parameters on composite material temperatures; (3) conceptual design, evaluation, and detailed thermal analyses of temperature limiting design concepts; and (4) the development of experimental data for assessment of the thermal design methodologies and data used for evaluation of the temperature-limiting design concepts. Temperature suppression attachment concepts were examined for relative merit. The simple isolator was identified as the most weight-effective concept and was selected for detail design, thermal analysis, and testing. Tests were performed on TPS standoff attachments to boron/aluminum, boron/polyimide and graphite/epoxy composite structures.

Cadmium sulfide rod-bundle structures decorated with nanoparticles from an inorganic/organic composite

NASA Astrophysics Data System (ADS)

Pan, Jun; Xi, Baojuan; Li, Jingfa; Yan, Yan; Li, Qianwen; Qian, Yitai

2011-08-01

We report a new morphology of wurzite cadmium sulfide with nanoparticles decorated on rod-bundle structures, which were synthesized via calcinations of an inorganic/organic composite at 400 °C in air. The composite was hydrothermally synthesized at 180 °C using thioglycolic acid (TGA) and cadmium acetate as starting materials. The structure, composition, and morphology of the prepared material were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscope, FT-IR spectrometry, photoluminescence spectrometry, and UV-visible spectrometry. Results indicated that the composite could be defined as CdS 0.65/Cd-TGA0.35. X-ray diffraction revealed that the annealed product is CdS with wurtizite phase. The diameter of the rod is about 150-400 nm and the length from the top to the bottom of the decorated nanoparticle is about 100 nm. The composite showed high intensity of photoluminescence with similar peak position, compared to that of wurtzite CdS, because of the structure defects.

Reverse Aging of Composite Materials for Aeronautical Applications

NASA Astrophysics Data System (ADS)

lannone, Michele

2008-08-01

Hygro-thermal ageing of polymer matrix composite materials is a major issue for all the aeronautical structures. For carbon-epoxy composites generally used in aeronautical applications the major effect of ageing is the humidity absorption, which induces a plasticization effect, generally decreasing Tg and elastic moduli, and finally design allowables. A thermodynamical and kinetic study has been performed, aimed to establish a program of periodic heating of the composite part, able to reversing the ageing effect by inducing water desorption. The study was founded on a simple model based on Fick's law, coupled with a concept of "relative saturation coefficient" depending on the different temperature of the composite part and the environment. The behaviour of some structures exposed to humidity and "reverse aged" by heating has been virtually tested. The conclusion of the study allowed to issue a specific patent application for aeronautical structures to be designed on the basis of a "humidity free" concept which allows the use of higher design allowables; having as final results lighter composite structures with a simplified certification process.

Structural Framework for Flight: NASA's Role in Development of Advanced Composite Materials for Aircraft and Space Structures

NASA Technical Reports Server (NTRS)

Tenney, Darrel R.; Davis, John G., Jr.; Johnston, Norman J.; Pipes, R. Byron; McGuire, Jack F.

2011-01-01

This serves as a source of collated information on Composite Research over the past four decades at NASA Langley Research Center, and is a key reference for readers wishing to grasp the underlying principles and challenges associated with developing and applying advanced composite materials to new aerospace vehicle concepts. Second, it identifies the major obstacles encountered in developing and applying composites on advanced flight vehicles, as well as lessons learned in overcoming these obstacles. Third, it points out current barriers and challenges to further application of composites on future vehicles. This is extremely valuable for steering research in the future, when new breakthroughs in materials or processing science may eliminate/minimize some of the barriers that have traditionally blocked the expanded application of composite to new structural or revolutionary vehicle concepts. Finally, a review of past work and identification of future challenges will hopefully inspire new research opportunities and development of revolutionary materials and structural concepts to revolutionize future flight vehicles.

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.

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.

Defining the loop structures in proteins based on composite β-turn mimics.

PubMed

Dhar, Jesmita; Chakrabarti, Pinak

2015-06-01

Asx- and ω-turns are β-turn mimics, which replace the conventional main-chain hydrogen bonds seen in the latter by those involving the side chains, and both involve three residues. In this paper we analyzed the cases where these turns occur together--side by side, with or without any gap, overlapping and in any order. These composite turns (of length 3-15 residues), occurring at ∼1 per 100 residues, may constitute the full length of many loops, and when the residues in the two component turns overlap or are adjacent to each other, the composite may take well-defined shape. It is thus possible for non-regular regions in protein structure to form local structural motifs, akin to the regular geometrical features exhibited by secondary structures. Composites having the order ω-turns followed by Asx-turns can constitute N-terminal helix capping motif. Ternary composite turns (made up of ω-, Asx- and ST-turns), some with characteristic shape, have also been identified. Delineation of composite turns would help in characterizing loops in protein structures, which often have functional roles. Some sequence patterns seen in composites can be used for their incorporation in protein design. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Evaluation by Rocket Combustor of C/C Composite Cooled Structure Using Metallic Cooling Tubes

NASA Astrophysics Data System (ADS)

Takegoshi, Masao; Ono, Fumiei; Ueda, Shuichi; Saito, Toshihito; Hayasaka, Osamu

In this study, the cooling performance of a C/C composite material structure with metallic cooling tubes fixed by elastic force without chemical bonding was evaluated experimentally using combustion gas in a rocket combustor. The C/C composite chamber was covered by a stainless steel outer shell to maintain its airtightness. Gaseous hydrogen as a fuel and gaseous oxygen as an oxidizer were used for the heating test. The surface of these C/C composites was maintained below 1500 K when the combustion gas temperature was about 2800 K and the heat flux to the combustion chamber wall was about 9 MW/m2. No thermal damage was observed on the stainless steel tubes that were in contact with the C/C composite materials. The results of the heating test showed that such a metallic tube-cooled C/C composite structure is able to control the surface temperature as a cooling structure (also as a heat exchanger) as well as indicated the possibility of reducing the amount of coolant even if the thermal load to the engine is high. Thus, application of this metallic tube-cooled C/C composite structure to reusable engines such as a rocket-ramjet combined-cycle engine is expected.

Methods for Detecting Defects in Composite Rehabilitated Concrete Structures : Final Report

DOT National Transportation Integrated Search

2005-04-01

Fiber reinforced polymer (FRP) composites are increasingly being used to rehabilitate under-strength or deteriorating concrete structural elements and to prolong useful service-life of bridge structures. The rehabilitation is conducted through the ex...

Infrared Spectroscopic Study on Structural Change and Interfacial Interaction in Rubber Composites Filled with Silica-Kaolin Hybrid Fillers

NASA Astrophysics Data System (ADS)

Chen, Y.; Guan, J.; Hu, H.; Gao, H.; Zhang, L.

2016-07-01

A series of natural rubber/styrene butadiene rubber/polybutadiene rubber composites was prepared with nanometer silica and micron kaolin by a dry modification process, mechanical compounding, and mold vulcanization. Fourier transform infrared spectroscopy and a scanning electron microscope were used to investigate the structural changes and interfacial interactions in composites. The results showed that the "seesaw" structure was formed particularly with the incorporation of silica particles in the preparation process, which would be beneficial to the dispersibility of fillers in the rubber matrix. The kaolinite platelets were generally arranged in directional alignment. Kaolinite with smaller particle size and low-defect structure was more stable in preparation, but kaolinite with larger particle size and high defect structure tended to change the crystal structure. The composite prepared in this research exhibited excellent mechanical and thermal properties.

Structural modeling for multicell composite rotor blades

NASA Technical Reports Server (NTRS)

Rehfield, Lawrence W.; Atilgan, Ali R.

1987-01-01

Composite material systems are currently good candidates for aerospace structures, primarily for the design flexibility they offer, i.e., it is possible to tailor the material and manufacturing approach to the application. A working definition of elastic or structural tailoring is the use of structural concept, fiber orientation, ply stacking sequence, and a blend of materials to achieve specific performance goals. In the design process, choices of materials and dimensions are made which produce specific response characteristics, and which permit the selected goals to be achieved. Common choices for tailoring goals are preventing instabilities or vibration resonances or enhancing damage tolerance. An essential, enabling factor in the design of tailored composite structures is structural modeling that accurately, but simply, characterizes response. The objective of this paper is to present a new multicell beam model for composite rotor blades and to validate predictions based on the new model by comparison with a finite element simulation in three benchmark static load cases.

Investigation of Mechanism of Action of Modifying Admixtures Based on Products of Petrochemical Synthesis on Concrete Structure

NASA Astrophysics Data System (ADS)

Tukhareli, V. D.; Tukhareli, A. V.; Cherednichenko, T. F.

2017-11-01

The creation of composite materials for generating structural elements with the desired properties has always been and still remains relevant. The basis of a modern concrete technology is the creation of a high-quality artificial stone characterized by low defectiveness and structure stability. Improving the quality of concrete compositions can be achieved by using chemical admixtures from local raw materials which is a very promising task of modern materials’ science for creation of a new generation of concretes. The new generation concretes are high-tech, high-quality, multicomponent concrete mixes and compositions with admixtures that preserve the required properties in service under all operating conditions. The growing complexity of concrete caused by systemic effects that allow you to control the structure formation at all stages of the technology ensures the obtaining of composites with "directional" quality, compositions, structure and properties. The possibility to use the organic fraction of oil refining as a multifunctional hydrophobic-plasticizing admixture in the effective cement concrete is examined.

Identification of damage in composite structures using Gaussian mixture model-processed Lamb waves

NASA Astrophysics Data System (ADS)

Wang, Qiang; Ma, Shuxian; Yue, Dong

2018-04-01

Composite materials have comprehensively better properties than traditional materials, and therefore have been more and more widely used, especially because of its higher strength-weight ratio. However, the damage of composite structures is usually varied and complicated. In order to ensure the security of these structures, it is necessary to monitor and distinguish the structural damage in a timely manner. Lamb wave-based structural health monitoring (SHM) has been proved to be effective in online structural damage detection and evaluation; furthermore, the characteristic parameters of the multi-mode Lamb wave varies in response to different types of damage in the composite material. This paper studies the damage identification approach for composite structures using the Lamb wave and the Gaussian mixture model (GMM). The algorithm and principle of the GMM, and the parameter estimation, is introduced. Multi-statistical characteristic parameters of the excited Lamb waves are extracted, and the parameter space with reduced dimensions is adopted by principal component analysis (PCA). The damage identification system using the GMM is then established through training. Experiments on a glass fiber-reinforced epoxy composite laminate plate are conducted to verify the feasibility of the proposed approach in terms of damage classification. The experimental results show that different types of damage can be identified according to the value of the likelihood function of the GMM.

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

Nelson, Stacy; English, Shawn; Briggs, Timothy

Fiber-reinforced composite materials offer light-weight solutions to many structural challenges. In the development of high-performance composite structures, a thorough understanding is required of the composite materials themselves as well as methods for the analysis and failure prediction of the relevant composite structures. However, the mechanical properties required for the complete constitutive definition of a composite material can be difficult to determine through experimentation. Therefore, efficient methods are necessary that can be used to determine which properties are relevant to the analysis of a specific structure and to establish a structure's response to a material parameter that can only be definedmore » through estimation. The objectives of this paper deal with demonstrating the potential value of sensitivity and uncertainty quantification techniques during the failure analysis of loaded composite structures; and the proposed methods are applied to the simulation of the four-point flexural characterization of a carbon fiber composite material. Utilizing a recently implemented, phenomenological orthotropic material model that is capable of predicting progressive composite damage and failure, a sensitivity analysis is completed to establish which material parameters are truly relevant to a simulation's outcome. Then, a parameter study is completed to determine the effect of the relevant material properties' expected variations on the simulated four-point flexural behavior as well as to determine the value of an unknown material property. This process demonstrates the ability to formulate accurate predictions in the absence of a rigorous material characterization effort. Finally, the presented results indicate that a sensitivity analysis and parameter study can be used to streamline the material definition process as the described flexural characterization was used for model validation.« less

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.

A single frequency component-based re-estimated MUSIC algorithm for impact localization on complex composite structures

NASA Astrophysics Data System (ADS)

Yuan, Shenfang; Bao, Qiao; Qiu, Lei; Zhong, Yongteng

2015-10-01

The growing use of composite materials on aircraft structures has attracted much attention for impact monitoring as a kind of structural health monitoring (SHM) method. Multiple signal classification (MUSIC)-based monitoring technology is a promising method because of its directional scanning ability and easy arrangement of the sensor array. However, for applications on real complex structures, some challenges still exist. The impact-induced elastic waves usually exhibit a wide-band performance, giving rise to the difficulty in obtaining the phase velocity directly. In addition, composite structures usually have obvious anisotropy, and the complex structural style of real aircrafts further enhances this performance, which greatly reduces the localization precision of the MUSIC-based method. To improve the MUSIC-based impact monitoring method, this paper first analyzes and demonstrates the influence of measurement precision of the phase velocity on the localization results of the MUSIC impact localization method. In order to improve the accuracy of the phase velocity measurement, a single frequency component extraction method is presented. Additionally, a single frequency component-based re-estimated MUSIC (SFCBR-MUSIC) algorithm is proposed to reduce the localization error caused by the anisotropy of the complex composite structure. The proposed method is verified on a real composite aircraft wing box, which has T-stiffeners and screw holes. Three typical categories of 41 impacts are monitored. Experimental results show that the SFCBR-MUSIC algorithm can localize impact on complex composite structures with an obviously improved accuracy.

Development of Carbon/Carbon Composites with Through-Thickness Carbon Nanotubes for Thermal and Structural Applications

DTIC Science & Technology

2008-12-01

AFRL-RX-WP-TR-2009-4013 DEVELOPMENT OF CARBON / CARBON COMPOSITES WITH THROUGH-THICKNESS CARBON NANOTUBES FOR THERMAL AND STRUCTURAL...31 August 2008 4. TITLE AND SUBTITLE DEVELOPMENT OF CARBON / CARBON COMPOSITES WITH THROUGH- THICKNESS CARBON NANOTUBES FOR THERMAL AND STRUCTURAL...13. SUPPLEMENTARY NOTES PAO Case Number: 88ABW-2009-1253; Clearance Date: 31 Mar 2009. Report contains color. 14. ABSTRACT Carbon / carbon

Optimal Sensor Fusion for Structural Health Monitoring of Aircraft Composite Components

DTIC Science & Technology

2011-09-01

sensor networks combine or fuse different types of sensors. Fiber Bragg Grating ( FBG ) sensors can be inserted in layers of composite structures to...consideration. This paper describes an example of optimal sensor fusion, which combines FBG sensors and PZT sensors. Optimal sensor fusion tries to find...Fiber Bragg Grating ( FBG ) sensors can be inserted in layers of composite structures to provide local damage detection, while surface mounted

Precision Composite Space Structures

DTIC Science & Technology

2007-10-15

large structures. 15. SUBJECT TERMS Composite materials, dimensional stability, microcracking, thermal expansion , space structures, degradation...Figure 32. Variation of normalized coefficients of thermal expansion α11(n), α22(n), and α33(n) with normalized crack density of an AS4/3501-6...coefficients of thermal expansion α11(n), α22(n), and α33(n) with normalized crack density of an AS4/3501-6 composite lamina with a fiber volume

Tuning Material and Component Properties to Reduce Weight and Increase Blastworthiness of a Notional V-Hull Structure

DTIC Science & Technology

2015-04-24

for designing blast-resistant structures [16]. The failure mechanisms in unidirectional fiber -reinforced composites of delamination, fiber -matrix...Batra, R.C., and Hassan, N.M., “Blast resistance of unidirectional fiber reinforced composites ,” Composites Part B: Engineering, 2008 18. Liu, X...feature a lighter weight structure, because this enables faster transport, higher mobility, greater fuel conservation, higher payload capacity, and

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.

Composite structural materials

NASA Technical Reports Server (NTRS)

Loewy, Robert G.; Wiberley, Stephen E.

1988-01-01

A decade long program to develop critical advanced composite technology in the areas of physical properties, structural concept and analysis, manufacturing, reliability, and life predictions is reviewed. Specific goals are discussed. The status of the chemical vapor deposition effects on carbon fiber properties; inelastic deformation of metal matrix laminates; fatigue damage in fibrous MMC laminates; delamination fracture toughness in thermoplastic matrix composites; and numerical analysis of composite micromechanical behavior are presented.

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.

Composite structural materials. [aircraft applications

NASA Technical Reports Server (NTRS)

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

1981-01-01

The development of composite materials for aircraft applications is addressed with specific consideration of physical properties, structural concepts and analysis, manufacturing, reliability, and life prediction. The design and flight testing of composite ultralight gliders is documented. Advances in computer aided design and methods for nondestructive testing are also discussed.

An engineering approach for the application of textile composites to a structural component

NASA Technical Reports Server (NTRS)

Baldwin, Jack W.; Gracias, Brian K.; Clark, Steven R.

1993-01-01

An engineering approach for the application of textile composites to a structural component is addressed. The main objective is to improve impact resistance of composite blades by using some form of 3-D reinforcement. Project goals, results, and conclusions are discussed.

77 FR 60167 - Agency Information Collection Activities: Requests for Comments; Clearance of Renewed Approval of...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-10-02

... and Fatigue Evaluation of Composite Rotorcraft Structures AGENCY: Federal Aviation Administration (FAA... Control Number: 2120-0753. Title: Damage Tolerance and Fatigue Evaluation of Composite Rotorcraft... technology for composite rotorcraft structures. In order to show compliance and obtain type certification...

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.;

Controlled surface segregation leads to efficient coke-resistant nickel/platinum bimetallic catalysts for the dry reforming of methane

DOE PAGES

Li, Lidong; Zhou, Lu; Ould-Chikh, Samy; ...

2015-02-03

Surface composition and structure are of vital importance for heterogeneous catalysts, especially for bimetallic catalysts, which often vary as a function of reaction conditions (known as surface segregation). The preparation of bimetallic catalysts with controlled metal surface composition and structure is very challenging. In this study, we synthesize a series of Ni/Pt bimetallic catalysts with controlled metal surface composition and structure using a method derived from surface organometallic chemistry. The evolution of the surface composition and structure of the obtained bimetallic catalysts under simulated reaction conditions is investigated by various techniques, which include CO-probe IR spectroscopy, high-angle annular dark-field scanningmore » transmission electron microscopy, energy-dispersive X-ray spectroscopy, extended X-ray absorption fine structure analysis, X-ray absorption near-edge structure analysis, XRD, and X-ray photoelectron spectroscopy. It is demonstrated that the structure of the bimetallic catalyst is evolved from Pt monolayer island-modified Ni nanoparticles to core–shell bimetallic nanoparticles composed of a Ni-rich core and a Ni/Pt alloy shell upon thermal treatment. As a result, these catalysts are active for the dry reforming of methane, and their catalytic activities, stabilities, and carbon formation vary with their surface composition and structure.« less

Investigations of plastic composite materials for highway safety structures

DOT National Transportation Integrated Search

1998-08-01

This report presents a basic overview and assessment of different concepts and technologies of using polymer composites in structures generally used for highway safety. The structural systems included a highway barrier guardrail with its posts and bl...

Effect of composition on the structure of lithium- and manganese-rich transition metal oxides

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

Shukla, Alpesh Khushalchand; Ramasse, Quentin M.; Ophus, Colin

In this work, we establish a definitive structural model for lithium- and manganese-rich transition metal oxides and demonstrate the effect of composition on their bulk as well as the surface structure.

Effect of composition on the structure of lithium- and manganese-rich transition metal oxides

DOE PAGES

Shukla, Alpesh Khushalchand; Ramasse, Quentin M.; Ophus, Colin; ...

2018-01-01

In this work, we establish a definitive structural model for lithium- and manganese-rich transition metal oxides and demonstrate the effect of composition on their bulk as well as the surface structure.

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.

Novel characterization of landscape-level variability in historical vegetation structure.

PubMed

Collins, Brandon M; Lydersen, Jamie M; Everett, Richard G; Fry, Danny L; Stephens, Scott L

2015-07-01

We analyzed historical timber inventory data collected systematically across a large mixed-conifer-dominated landscape to gain insight into the interaction between disturbances and vegetation structure and composition prior to 20th century land management practices. Using records from over 20 000 trees, we quantified historical vegetation structure and composition for nine distinct vegetation groups. Our findings highlight some key aspects of forest structure under an intact disturbance regime: (1) forests were low density, with mean live basal area and tree density ranging from 8-30 m2 /ha and 25-79 trees/ha, respectively; (2) understory and overstory structure and composition varied considerably across the landscape; and (3) elevational gradients largely explained variability in forest structure over the landscape. Furthermore, the presence of large trees across most of the surveyed area suggests that extensive stand-replacing disturbances were rare in these forests. The vegetation structure and composition characteristics we quantified, along with evidence of largely elevational control on these characteristics, can provide guidance for restoration efforts in similar forests.

Composite intersection reinforcement

NASA Technical Reports Server (NTRS)

Misciagna, David T. (Inventor); Fuhrer, Jessica J. (Inventor); Funk, Robert S. (Inventor); Tolotta, William S. (Inventor)

2010-01-01

An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.

Composite Intersection Reinforcement

NASA Technical Reports Server (NTRS)

Misciagna, David T. (Inventor); Fuhrer, Jessica J. (Inventor); Funk, Robert S. (Inventor); Tolotta, William S. (Inventor)

2013-01-01

An assembly and method for manufacturing a composite reinforcement for unitizing a structure are provided. According to one embodiment, the assembly includes a base having a plurality of pins extending outwardly therefrom to define a structure about which a composite fiber is wound to define a composite reinforcement preform. The assembly also includes a plurality of mandrels positioned adjacent to the base and at least a portion of the composite reinforcement preform, and a cap that is positioned over at least a portion of the plurality of mandrels. The cap is configured to engage each of the mandrels to support the mandrels and the composite reinforcement preform during a curing process to form the composite reinforcement.

Bioresponsive Materials for Drug Delivery Based on Carboxymethyl Chitosan/Poly(γ-Glutamic Acid) Composite Microparticles

PubMed Central

Yan, Xiaoting; Tong, Zongrui; Chen, Yu; Mo, Yanghe; Feng, Huaiyu; Li, Peng; Qu, Xiaosai; Jin, Shaohua

2017-01-01

Carboxymethyl chitosan (CMCS) microparticles are a potential candidate for hemostatic wound dressing. However, its low swelling property limits its hemostatic performance. Poly(γ-glutamic acid) (PGA) is a natural polymer with excellent hydrophilicity. In the current study, a novel CMCS/PGA composite microparticles with a dual-network structure was prepared by the emulsification/internal gelation method. The structure and thermal stability of the composite were determined by Fourier transform infrared spectroscopy (FTIR), X-ray powder diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), and thermogravimetric analysis (TGA). The effects of preparation conditions on the swelling behavior of the composite were investigated. The results indicate that the swelling property of CMCS/PGA composite microparticles is pH sensitive. Levofloxacin (LFX) was immobilized in the composite microparticles as a model drug to evaluate the drug delivery performance of the composite. The release kinetics of LFX from the composite microparticles with different structures was determined. The results suggest that the CMCS/PGA composite microparticles are an excellent candidate carrier for drug delivery. PMID:28452963

On the monitoring and implications of growing damages caused by manufacturing defects in composite structures

NASA Astrophysics Data System (ADS)

Schagerl, M.; Viechtbauer, C.; Hörrmann, S.

2015-07-01

Damage tolerance is a classical safety concept for the design of aircraft structures. Basically, this approach considers possible damages in the structure, predicts the damage growth under applied loading conditions and predicts the following decrease of the structural strength. As a fundamental result the damage tolerance approach yields the maximum inspection interval, which is the time a damage grows from a detectable to a critical level. The above formulation of the damage tolerance safety concept targets on metallic structures where the damage is typically a simple fatigue crack. Fiber-reinforced polymers show a much more complex damage behavior, such as delaminationsin laminated composites. Moreover, progressive damage in composites is often initiated by manufacturing defects. The complex manufacturing processes for composite structures almost certainly yield parts with defects, e.g. pores in the matrix or undulations of fibers. From such defects growing damages may start after a certain time of operation. The demand to simplify or even avoid the inspection of composite structures has therefore led to a comeback of the traditional safe-life safety concept. The aim of the so-called safe-life flaw tolerance concept is a structure that is capable of carrying the static loads during operation, despite significant damages and after a representative fatigue load spectrum. A structure with this property does not need to be inspected, respectively monitored at all during its service life. However, its load carrying capability is thereby not fully utilized. This article presents the possible refinement of the state-of-the-art safe-life flaw tolerance concept for composite structures towards a damage tolerance approach considering also the influence of manufacturing defects on damage initiation and growth. Based on fundamental physical relations and experimental observations the challenges when developing damage growth and residual strength curves are discussed.

Design development of graphite primary structures enables SSTO success

NASA Astrophysics Data System (ADS)

Biagiotti, V. A.; Yahiro, J. S.; Suh, Daniel E.; Hodges, Eric R.; Prior, Donald J.

1997-01-01

This paper describes the development of a graphite composite wing and a graphite composite intertank primary structure for application toward Single-Stage to Orbit space vehicles such as those under development in NASA's X-33/Reusable Launch Vehicle (RLV) Program. The trade study and designs are based on a Rockwell vertical take-off and horizontal landing (VTHL) wing-body RLV vehicle. Northrop Grumman's approach using a building block development technique is described. Composite Graphite/Bismaleimide (Gr/BMI) material characterization test results are presented. Unique intertank and wing composite subcomponent test article designs are described and test results to date are presented. Wing and intertank Full Scale Section Test Article (FSTA) objectives and designs are outlined. Trade studies, supporting building block testing, and FSTA demonstrations combine to develop graphite primary structure composite technology that enables developing X-33/RLV design programs to meet critical SSTO structural weight and operations performance criteria.

An Assessment of the State-of-the-Art in the Design and Manufacturing of Large Composite Structures for Aerospace Vehicles

NASA Technical Reports Server (NTRS)

Harris, Charles E.; Starnes, James H., Jr.; Shuart, Mark J.

2001-01-01

The results of an assessment of the state-of-the-art in the design and manufacturing of large composite structures are described. The focus of the assessment is on the use of polymeric matrix composite materials for large airframe structural components. such as those in commercial and military aircraft and space transportation vehicles. Applications of composite materials for large commercial transport aircraft, general aviation aircraft, rotorcraft, military aircraft. and unmanned rocket launch vehicles are reviewed. The results of the assessment of the state-of-the-art include a summary of lessons learned, examples of current practice, and an assessment of advanced technologies under development. The results of the assessment conclude with an evaluation of the future technology challenges associated with applications of composite materials to the primary structures of commercial transport aircraft and advanced space transportation vehicles.

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

NASA Astrophysics Data System (ADS)

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

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

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.

Fiber grating systems used to measure strain in cylindrical structures

NASA Astrophysics Data System (ADS)

Udd, Eric; Corona-Bittick, Kelli; Slattery, Kerry T.; Dorr, Donald J.; Crowe, C. Robert; Vandiver, Terry L.; Evans, Robert N.

1997-07-01

Fiber optic grating systems are described that have been used to measure strain in cylindrical structures. The applications of these systems to a composite utility pole and to a composite missile body are described. Composite utility poles have significant advantages with respect to wooden utility poles that include superior strength and uniformity; light weight for ease of deployment; the ability to be recycled, reducing hazardous waste associated with chemically treated wooden poles; and compatibility with embedded fiber optic sensors, allowing structural loads to be monitored. Tests conducted of fiber optic grating sensors in combination with an overcoupled coupler demodulation system to support structural testing of a 22-ft composite pole are reported. Monitoring strain in composite missile bodies has the potential to improve the quality of manufactured parts, support performance testing, and enhance safety during long periods of storage. Strain measurements made with fiber optic grating and electrical strain gauges are described.

Research Developments in Nondestructive Evaluation and Structural Health Monitoring for the Sustainment of Composite Aerospace Structures at NASA

NASA Technical Reports Server (NTRS)

Cramer, K. Elliott

2016-01-01

The use of composite materials continues to increase in the aerospace community due to the potential benefits of reduced weight, increased strength, and manufacturability. Ongoing work at NASA involves the use of the large-scale composite structures for spacecraft (payload shrouds, cryotanks, crew modules, etc). NASA is also working to enable both the use and sustainment of composites in commercial aircraft structures. One key to the sustainment of these large composite structures is the rapid, in-situ characterization of a wide range of potential defects that may occur during the vehicle's life. Additionally, in many applications it is necessary to monitor changes in these materials over their lifetime. Quantitative characterization through Nondestructive Evaluation (NDE) of defects such as reduced bond strength, microcracking, and delamination damage due to impact, are of particular interest. This paper will present an overview of NASA's applications of NDE technologies being developed for the characterization and sustainment of advanced aerospace composites. The approaches presented include investigation of conventional, guided wave, and phase sensitive ultrasonic methods and infrared thermography techniques for NDE. Finally, the use of simulation tools for optimizing and validating these techniques will also be discussed.

Fabrication and characterization of iron oxide dextran composite layers

NASA Astrophysics Data System (ADS)

Iconaru, S. L.; Predoi, S. A.; Beuran, M.; Ciobanu, C. S.; Trusca, R.; Ghita, R.; Negoi, I.; Teleanu, G.; Turculet, S. C.; Matei, M.; Badea, Monica; Prodan, A. M.

2018-02-01

Super paramagnetic iron oxide nanoparticles such as maghemite have been shown to exhibit antimicrobial properties [1-5]. Moreover, the iron oxide nanoparticles have been proposed as a potential magnetically controllable antimicrobial agent which could be directed to a specific infection [3-5]. The present research has focused on studies of the surface and structure of iron oxide dextran (D-IO) composite layers surface and structure. These composite layers were deposited on Si substrates. The structure of iron oxide dextran composite layers was investigated by X-Ray Diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR) while the surface morphology was evaluated by Scanning Electron Microscopy (SEM). The structural characterizations of the iron oxide dextran composite layers revealed the basic constituents of both iron and dextran structure. Furthermore, the in vitro evaluation of the antifungal effect of the complex layers, which have been shown revealed to be active against C. albicans cells at distinct intervals of time, is exhibited. Our research came to confirm the fungicidal effect of iron oxide dextran composite layers. Also, our results suggest that iron oxide dextran surface may be used for medical treatment of biofilm associated Candida infections.

Analysis of the Shear Behavior of Stubby Y-Type Perfobond Rib Shear Connectors for a Composite Frame Structure.

PubMed

Kim, Sang-Hyo; Kim, Kun-Soo; Lee, Do-Hoon; Park, Jun-Seung; Han, Oneil

2017-11-22

Shear connectors are used in steel beam-concrete slabs of composite frame and bridge structures to transfer shear force according to design loads. The existing Y-type perfobond rib shear connectors are designed for girder slabs of composite bridges. Therefore, the rib and transverse rebars of the conventional Y-type perfobond rib shear connectors are extremely large for the composite frames of building structures. Thus, this paper proposes stubby Y-type perfobond rib shear connectors, redefining the existing connectors, for composite frames of building structures; these were used to perform push-out tests. These shear connectors have relatively small ribs compared to the conventional Y-type perfobond rib shear connectors. To confirm the shear resistance of these stubby shear connectors, we performed an experiment by using transverse rebars D13 and D16. The results indicate that these shear connectors have suitable shear strength and ductility for application in composite frame structures. The shear strengths obtained using D13 and D16 were not significantly different. However, the ductility of the shear connectors with D16 was 45.1% higher than that of the shear connectors with D13.

Composite Structural Motifs of Binding Sites for Delineating Biological Functions of Proteins

PubMed Central

Kinjo, Akira R.; Nakamura, Haruki

2012-01-01

Most biological processes are described as a series of interactions between proteins and other molecules, and interactions are in turn described in terms of atomic structures. To annotate protein functions as sets of interaction states at atomic resolution, and thereby to better understand the relation between protein interactions and biological functions, we conducted exhaustive all-against-all atomic structure comparisons of all known binding sites for ligands including small molecules, proteins and nucleic acids, and identified recurring elementary motifs. By integrating the elementary motifs associated with each subunit, we defined composite motifs that represent context-dependent combinations of elementary motifs. It is demonstrated that function similarity can be better inferred from composite motif similarity compared to the similarity of protein sequences or of individual binding sites. By integrating the composite motifs associated with each protein function, we define meta-composite motifs each of which is regarded as a time-independent diagrammatic representation of a biological process. It is shown that meta-composite motifs provide richer annotations of biological processes than sequence clusters. The present results serve as a basis for bridging atomic structures to higher-order biological phenomena by classification and integration of binding site structures. PMID:22347478

Resin infusion of layered metal/composite hybrid and resulting metal/composite hybrid laminate

NASA Technical Reports Server (NTRS)

Cano, Roberto J. (Inventor); Grimsley, Brian W. (Inventor); Weiser, Erik S. (Inventor); Jensen, Brian J. (Inventor)

2009-01-01

A method of fabricating a metal/composite hybrid laminate is provided. One or more layered arrangements are stacked on a solid base to form a layered structure. Each layered arrangement is defined by a fibrous material and a perforated metal sheet. A resin in its liquid state is introduced along a portion of the layered structure while a differential pressure is applied across the laminate structure until the resin permeates the fibrous material of each layered arrangement and fills perforations in each perforated metal sheet. The resin is cured thereby yielding a metal/composite hybrid laminate.

Evaluation of Composite Structures Technologies for Application to NASA's Vision for Space Exploration (CoSTS)

NASA Technical Reports Server (NTRS)

Deo, Ravi; Wang, Donny; Bohlen, Jim; Fukuda, Cliff

2008-01-01

A trade study was conducted to determine the suitability of composite structures for weight and life cycle cost savings in primary and secondary structural systems for crew exploration vehicles, crew and cargo launch vehicles, landers, rovers, and habitats. The results of the trade study were used to identify and rank order composite material technologies that can have a near-term impact on a broad range of exploration mission applications. This report recommends technologies that should be developed to enable usage of composites on Vision for Space Exploration vehicles towards mass and life-cycle cost savings.

Design and analysis of aerospace structures at elevated temperatures. [aircraft, missiles, and space platforms

NASA Technical Reports Server (NTRS)

Chang, C. I.

1989-01-01

An account is given of approaches that have emerged as useful in the incorporation of thermal loading considerations into advanced composite materials-based aerospace structural design practices. Sources of structural heating encompass not only propulsion system heat and aerodynamic surface heating at supersonic speeds, but the growing possibility of intense thermal fluxes from directed-energy weapons. The composite materials in question range from intrinsically nonheat-resistant polymer matrix systems to metal-matrix composites, and increasingly to such ceramic-matrix composites as carbon/carbon, which are explicitly intended for elevated temperature operation.

Composite foam structures

NASA Technical Reports Server (NTRS)

Williams, Brian E. (Inventor); Brockmeyer, Jerry (Inventor); Tuffias, Robert H. (Inventor)

2005-01-01

A composite rigid foam structure that has a skin or coating on at least one of its surfaces. The skin is formed in situ by thermal spray techniques. The skin is bonded substantially throughout the surface of the porous substrate to the peripheries of the pores. The skin on the average does not penetrate the surface of the substrate by more than the depth of about 2 to 5 pores. Thus, thermal spraying the skin onto the rigid foam produces a composite that is tightly and uniformly bonded together without unduly increasing the weight of the composite structure. Both thermal conductivity and bonding are excellent.

Service evaluation of aircraft composite structural components

NASA Technical Reports Server (NTRS)

Brooks, W. A., Jr.; Dow, M. B.

1973-01-01

The advantages of the use of composite materials in structural applications have been identified in numerous engineering studies. Technology development programs are underway to correct known deficiencies and to provide needed improvements. However, in the final analysis, flight service programs are necessary to develop broader acceptance of, and confidence in, any new class of materials such as composites. Such flight programs, initiated by NASA Langley Research Center, are reviewed. These programs which include the selectively reinforced metal and the all-composite concepts applied to both secondary and primary aircraft structural components, are described and current status is indicated.

On the Mechanical Behavior of Advanced Composite Material Structures

NASA Astrophysics Data System (ADS)

Vinson, Jack

During the period between 1993 and 2004, the author, as well as some colleagues and graduate students, had the honor to be supported by the Office of Naval Research to conduct research in several aspects of the behavior of structures composed of composite materials. The topics involved in this research program were numerous, but all contributed to increasing the understanding of how various structures that are useful for marine applications behaved. More specifically, the research topics focused on the reaction of structures that were made of fiber reinforced polymer matrix composites when subjected to various loads and environmental conditions. This included the behavior of beam, plate/panel and shell structures. It involved studies that are applicable to fiberglass, graphite/carbon and Kevlar fibers imbedded in epoxy, polyester and other polymeric matrices. Unidirectional, cross-ply, angle ply, and woven composites were involved, both in laminated, monocoque as well as in sandwich constructions. Mid-plane symmetric as well as asymmetric laminates were studied, the latter involving bending-stretching coupling and other couplings that only can be achieved with advanced composite materials. The composite structures studied involved static loads, dynamic loading, shock loading as well as thermal and hygrothermal environments. One major consideration was determining the mechanical properties of composite materials subjected to high strain rates because the mechanical properties vary so significantly as the strain rate increases. A considerable number of references are cited for further reading and study for those interested.

New Textile Sensors for In Situ Structural Health Monitoring of Textile Reinforced Thermoplastic Composites Based on the Conductive Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) Polymer Complex.

PubMed

Jerkovic, Ivona; Koncar, Vladan; Grancaric, Ana Marija

2017-10-10

Many metallic structural and non-structural parts used in the transportation industry can be replaced by textile-reinforced composites. Composites made from a polymeric matrix and fibrous reinforcement have been increasingly studied during the last decade. On the other hand, the fast development of smart textile structures seems to be a very promising solution for in situ structural health monitoring of composite parts. In order to optimize composites' quality and their lifetime all the production steps have to be monitored in real time. Textile sensors embedded in the composite reinforcement and having the same mechanical properties as the yarns used to make the reinforcement exhibit actuating and sensing capabilities. This paper presents a new generation of textile fibrous sensors based on the conductive polymer complex poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) developed by an original roll to roll coating method. Conductive coating for yarn treatment was defined according to the preliminary study of percolation threshold of this polymer complex. The percolation threshold determination was based on conductive dry films' electrical properties analysis, in order to develop highly sensitive sensors. A novel laboratory equipment was designed and produced for yarn coating to ensure effective and equally distributed coating of electroconductive polymer without distortion of textile properties. The electromechanical properties of the textile fibrous sensors confirmed their suitability for in situ structural damages detection of textile reinforced thermoplastic composites in real time.

NASA-UVA light aerospace alloy and structures technology program (LA(sup 2)ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Haviland, John K.; Herakovich, Carl T.; Pilkey, Walter D.; Pindera, Marek-Jerzy; Scully, John R.; Starke, Edgar A., Jr.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.

1992-01-01

The general objective of the Light Aerospace Alloy and Structures Technology (LA(sup 2)ST) Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites, and thermal gradient structures in collaboration with Langley researchers. Specific technical objectives are established for each research project. We aim to produce relevant data and basic understanding of material behavior and microstructure, new monolithic and composite alloys, advanced processing methods, new solid and fluid mechanics analyses, measurement advances, and critically, a pool of educated graduate students for aerospace technologies. Four research areas are being actively investigated, including: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals and Composites; (2) Aerospace Materials Science; (3) Mechanics of Materials and Composites for Aerospace Structures; and (4) Thermal Gradient Structures.

Study of the structure and chemical composition of the protective coating of a fist stage gas turbine blade after regenerative heat treatment

NASA Astrophysics Data System (ADS)

Davidov, D. I.; Kazantseva, N. V.; Vinogradova, N. I.; Ezhov, I. V.

2017-12-01

Investigation of the structure and chemical composition of the protective coating of the first stage IN738 gas turbine blade after standard regenerative heat treatment was done. It was found the degradation of microstructure and chemical composition of both the blade feather and its protective coating. Redistribution of the chemical elements decreasing the corrosion resistance was observed inside the protective coating. Cracks on the boundary between the blade feather and the protective coating were found by scanning electron microscopy. The carbide transformation and sigma phase were found in the structure of the blade feather. Based upon the structural and chemical composition studies, it is concluded that the standard regenerative heat treatment of the IN738 operative gas turbine blade does not provide full structure regeneration.

An overview of the NASA textile composites program

NASA Technical Reports Server (NTRS)

Dexter, H. Benson

1993-01-01

The NASA Langley Research Center is conducting and sponsoring research to explore the benefits of textile reinforced composites for civil transport aircraft primary structures. The objective of this program is to develop and demonstrate the potential of affordable textile reinforced composite materials to meet design properties and damage tolerance requirements of advanced aircraft structures. In addition to in-house research, the program includes major participation by the aircraft industry and aerospace textile companies. The major program elements include development of textile preforms, processing science, mechanics of materials, experimental characterization of materials, and development and evaluation of textile reinforced composite structural elements and subcomponents. The NASA Langley in-house research is focused on science-based understanding of resin transfer molding (RTM), development of powder-coated towpreg processes, analysis methodology, and development of a performance database on textile reinforced composites. The focus of the textile industry participation is on development of multidirectional, damage-tolerant preforms, and the aircraft industry participation is in the areas of innovative design concepts, cost-effective fabrication, and testing of textile reinforced composite structural elements and subcomponents. Textile processes such as 3-D weaving, 2-D and 3-D braiding, and knitting/stitching are being compared with conventional laminated tape processes for improved damage tolerance. Through-the-thickness reinforcements offer significant damage tolerance improvements. However, these gains must be weighed against potential loss in in-plane properties such as strength and stiffness. Analytical trade studies are underway to establish design guidelines for the application of textile material forms to meet specific loading requirements. Fabrication and testing of large structural components are required to establish the full potential of textile reinforced composite materials. The goals of the NASA Langley-sponsored research program are to demonstrate technology readiness with subscale composite components by 1995 and to verify the performance of full-scale composite primary aircraft structural components by 1997. The status of textile reinforced composite structural elements under development by Boeing, Douglas, Lockheed, and Grumman are presented. Included are braided frames and woven/stitched wing and fuselage panels.

Energy absorption of composite material and structure

NASA Technical Reports Server (NTRS)

Farley, Gary L.

1987-01-01

Results are presented from a joint research program on helicopter crashworthiness conducted by the U.S. Army Aerostructures Directorate and NASA Langley. Through the ongoing research program an in-depth understanding has been developed on the cause/effect relationships between material and architectural variables and the energy-absorption capability of composite material and structure. Composite materials were found to be efficient energy absorbers. Graphite/epoxy subfloor structures were more efficient energy absorbers than comparable structures fabricated from Kevlar or aluminum. An accurate method of predicting the energy-absorption capability of beams was developed.

Structural biological composites: An overview

NASA Astrophysics Data System (ADS)

Meyers, Marc A.; Lin, Albert Y. M.; Seki, Yasuaki; Chen, Po-Yu; Kad, Bimal K.; Bodde, Sara

2006-07-01

Biological materials are complex composites that are hierarchically structured and multifunctional. Their mechanical properties are often outstanding, considering the weak constituents from which they are assembled. They are for the most part composed of brittle (often, mineral) and ductile (organic) components. These complex structures, which have risen from millions of years of evolution, are inspiring materials scientists in the design of novel materials. This paper discusses the overall design principles in biological structural composites and illustrates them for five examples; sea spicules, the abalone shell, the conch shell, the toucan and hornbill beaks, and the sheep crab exoskeleton.

High-Speed, Three Dimensional Object Composition Mapping Technology

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

Ishikawa, M Y

2001-02-14

This document overviews an entirely new approach to determining the composition--the chemical-elemental, isotopic and molecular make-up--of complex, highly structured objects, moreover with microscopic spatial resolution in all 3 dimensions. The front cover depicts the new type of pulsed laser system at the heart of this novel technology under adjustment by Alexis Wynne, and schematically indicates two of its early uses: swiftly analyzing the 3-D composition governed structure of a transistor circuit with both optical and mass-spectrometric detectors, and of fossilized dinosaur and turtle bones high-speed probed by optical detection means. Studying the composition-cued 3-D micro-structures of advanced composite materials andmore » the microscopic scale composition-texture of biological tissues are two near-term examples of the rich spectrum of novel applications enabled by this field-opening analytic tool-set.« less

Composite structural materials

NASA Technical Reports Server (NTRS)

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

1978-01-01

The purpose of the RPI composites program is to develop advanced technology in the areas of physical properties, structural concepts and analysis, manufacturing, reliability and life prediction. Concommitant goals are to educate engineers to design and use composite materials as normal or conventional materials. A multifaceted program was instituted to achieve these objectives.

Structure and composition of vegetation along an elevational gradient in Puerto Rico.

Treesearch

W.A. Gould; G. Gonzalez; G. Carrero Rivera

2006-01-01

Question: What are the composition, conservation status, and structural and environmental characteristics of eight mature tropical forest plant communities that occur along an elevational gradient. Location: Northeastern Puerto Rico. Methods: We quantified the species composition, diversity, conservation status, and ecological attributes of eight mature tropical forest...

Lightweight blast shield

DOEpatents

Mixon, Larry C.; Snyder, George W.; Hill, Scott D.; Johnson, Gregory L.; Wlodarski, J. Frank; von Spakovsky, Alexis P.; Emerson, John D.; Cole, James M.; Tipton, John P.

1991-01-01

A tandem warhead missile arrangement that has a composite material housing structure with a first warhead mounted at one end and a second warhead mounted near another end of the composite structure with a dome shaped composite material blast shield mounted between the warheads to protect the second warhead from the blast of the first warhead.

Study on utilization of advanced composites in commercial aircraft wing structures, volume 2

NASA Technical Reports Server (NTRS)

Sakata, I. F.; Ostrom, R. B.

1978-01-01

A plan is defined for a composite wing development effort which will assist commercial transport manufacturers in reaching a level of technology readiness where the utilization of composite wing structure is a cost competitive option for a new aircraft production plan. The recommended development effort consists of two programs: a joint government/industry material development program and a wing structure development program. Both programs are described in detail.

Optical study on the dependence of breast tissue composition and structure on subject anamnesis

NASA Astrophysics Data System (ADS)

Taroni, Paola; Quarto, Giovanna; Pifferi, Antonio; Abbate, Francesca; Balestreri, Nicola; Menna, Simona; Cassano, Enrico; Cubeddu, Rinaldo

2015-07-01

Time domain multi-wavelength (635 to 1060 nm) optical mammography was performed on 200 subjects to estimate their average breast tissue composition in terms of oxy- and deoxy-hemoglobin, water, lipid and collagen, and structural information, as provided by scattering parameters (amplitude and power). Significant (and often marked) dependence of tissue composition and structure on age, menopausal status, body mass index, and use of oral contraceptives was demonstrated.

Habitat structural effect on squamata fauna of the restinga ecosystem in northeastern Brazil.

PubMed

Dias, Eduardo J R; Rocha, Carlos F D

2014-03-01

In this work, we surveyed data on richness and composition of squamatan reptiles and habitat structural effect in nine areas of restinga ecosystem in the State of Bahia, northeastern Brazil. The "restinga" ecosystems are coastal sand dune habitats on the coast of Brazil. Our main hypothesis is that the Squamata fauna composition along these restinga areas would be modulated by habitat structural. After 90 days of field sampling we recorded approximately 5% of reptile species known in Brazil. The composition of Squamata assemblages varied mainly based on the presence or absence of lizards of the genera Ameivula and Tropidurus. Our data showed that habitat structure consistently affected the composition of local Squamata fauna, especially lizards.

Composite theory applied to elastomers

NASA Technical Reports Server (NTRS)

Clark, S. K.

1986-01-01

Reinforced elastomers form the basis for most of the structural or load carrying applications of rubber products. Computer based structural analysis in the form of finite element codes was highly successful in refining structural design in both isotropic materials and rigid composites. This has lead the rubber industry to attempt to make use of such techniques in the design of structural cord-rubber composites. While such efforts appear promising, they were not easy to achieve for several reasons. Among these is a distinct lack of a clearly defined set of material property descriptors suitable for computer analysis. There are substantial differences between conventional steel, aluminum, or even rigid composites such as graphite-epoxy, and textile-cord reinforced rubber. These differences which are both conceptual and practical are discussed.

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.

Mechanical Characterization of Baslat Based Natural Hybrid Composites for Aerospace Applications

NASA Astrophysics Data System (ADS)

Alexander, J.; Elphej Churchill, S. J.

2017-05-01

Advanced composites have attracted aircraft designers due to its high strength to weight ratio, high stiffness to weight ratio, tailoring properties, hybridization of opposites etc. Moreover the cost reduction is also another important requirement of structural components. Basalt fibers are new entry in structural field which has excellent properties more or less equivalent to GFRP composites. Using these basalt fibres, new hybrid composites were developed by combining basalt fibres with natural fibres. The mechanical and thermal properties were determined and compared with BFRP and GFRP composites. Results proved that hybrid composites have some good qualities.

Non-Conventional Carbon Nanotube Skeleton Reinforced Composites for Space Applications

NASA Astrophysics Data System (ADS)

Hepp, Felicitas; Pfeiffer, E. K.; Pereira, C.; Martins, M.; Liedtke, V.; Macho, C.; Aschenbrenner, O.; Forero, S.; Linke, S.; Masouras, A.; Vavouliotis, A.; Kostopoulos, V.; Wulz, H.-G.; Pambaguian, L.

2014-06-01

Carbon Nanotubes (CNT) embedded in composite materials like CFRP, polymers or ceramics, can improve specific performance characteristics such as e.g. electrical conductivity, mechanical fatigue and crack propagation, mechanical properties, alpha/epsilon values, PIM-reduction, EMC shielding, etc.CNT skeletons, also called Bucky papers and Bucky discs, are macroscopic aggregates of Carbon Nanotubes. These skeletons are used in composites with different matrices, namely metal, ceramic or polymer or directly used in CFRP composites.The aim is to increase the performance of composite space structures by increasing the material characteristics or provide composites with additional sensing abilities like structural health monitoring.

Advanced Single-Polymer Nanofiber-Reinforced Composite - Towards Next Generation Ultralight Superstrong/Tough Structural Material

DTIC Science & Technology

2015-04-29

AFRL-OSR-VA-TR-2015-0144 ADVANCED SINGLE-POLYMER NANOFIBER-REINFORCED COMPOSITE YURIS DZENIS UNIVERSITY OF NEBRSKA Final Report 04/29/2015... COMPOSITE - TOWARDS NEXT GENERATION ULTRALIGHT SUPERSTRONG/TOUGH STRUCTURAL MATERIAL 5a. CONTRACT NUMBER 5b. GRANT NUMBER FA9550-11-1-0204 5c. PROGRAM...characterize their mechanical behavior and properties; and (3) fabricate and characterize polyimide nanofiber-reinforced composites . Continuous

Structure and properties of hybrid composite materials

NASA Astrophysics Data System (ADS)

Chernyshova, T. A.; Kobeleva, L. I.; Bolotova, L. K.; Katin, I. V.

2013-03-01

The structure and interfacial interaction are studied in the hybrid aluminum-matrix composite materials fabricated by reactive casting combined with mechanical mixing of fillers with a metallic melt. The following types of hardening are considered: hardening by ceramic particles and by the phases formed as isolated inclusions or coatings on ceramic particles during in situ reactions. The hardness and tribological properties of the composite materials as functions of their compositions are discussed.

Low Temperature Processing of Boron Carbide Cement Composite for Tough, Wear Resistant Structures

DTIC Science & Technology

1997-12-15

TITLE AND SUBTITLE Low Temperature Processing of Boron Carbide Cement Composite for Tough, Wear Resistant Structures 6. AUTHOR(S) Kristen J. Law...project has developed a low temperature polymer ceramic composite consisting of boron carbide layers bonded by cement, laminated with polymer...composite have been shown to compare favorably to those of partially sintered boron carbide. Applications for this material have been identified in

Hydrodynamic Response of a Composite Structure in an Arctic Environment

DTIC Science & Technology

2015-06-01

the navy’s first ship constructed entirely of composite materials. The 24-meter long ship is built from carbon fiber reinforced epoxy. The ship is...allowed for repeatable experimentation. Strain gauges were attached to critical locations of the composite plate towed through the tank . Both plate...SUBJECT TERMS Tow Tank , Fluid Structure Interaction, FSI, Composite Material, E-Glass, ANSYS, Hull Shape, CFX, Arctic. 15. NUMBER OF PAGES 131

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

NASA Technical Reports Server (NTRS)

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

2017-01-01

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

Method for Selective Cleaning of Mold Release from Composite Honeycomb Surfaces

NASA Technical Reports Server (NTRS)

Pugel, Diane

2011-01-01

Honeycomb structures are commonly employed as load- and force-bearing structures as they are structurally strong and lightweight. Manufacturing processes for heat-molded composite honeycomb structures commence with the placement of pre-impregnated composite layups over metal mandrels. To prevent permanent bonding between the composite layup and the metal mandrels, an agent, known as a mold release agent, is used. Mold release agents allow the molded composite material to be removed from mandrels after a heat-forming process. Without a specific removal process, mold release agents may continue to adhere to the surface of the composite material, thereby affecting the bonding of other materials that may come into contact with the composite surface in later stages of processing A constituent common to commercially available household cleaning agents is employed for the removal of mold release agents common to the manufacturing of heat-formed composite materials. The reliability of the solvent has been proven by the longevity and reliability of commercial household cleaners. At the time of this reporting, no one has attempted using constituent for this purpose. The material to be cleaned is immersed in the solution, vertically removed so that the solution is allowed to drain along cell walls and into a solvent bath, and then placed on a compressed airflow table for drying.

Structural, dielectric and magnetic studies of (x) Ni0.7Co0.1Cu0.2Fe2O4 + (1-x) BaTiO3 magnetoelectric composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Parveez, Asiya; Giridharan, N. V.; Sankarappa, T.

2016-05-01

The Magneto-electric composites (x) Ni0.7Co0.1Cu0.2Fe2O4 + (1-x) BaTiO3 (x=10%, 20% and 30%) were synthesized by sintering mixtures of highly ferroelectric BaTiO3 (BT) and highly magneto-strictive component Ni0.7Co0.1Cu0.2Fe2O4 (NCCF). The presences of constituent phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for NCCF ferrite phase and tetragonal perovskite structure for BT and, both spinel and pervoskite structures for synthesized ME composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency and composition dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at room temperature using Hioki LCR Hi-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The hysteresis behavior was studied to understand the magnetic ordering in the synthesized composites using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.

On stress-state optimization in steel-concrete composite structures

NASA Astrophysics Data System (ADS)

Brauns, J.; Skadins, U.

2017-10-01

The plastic resistance of a concrete-filled column commonly is given as a sum of the components and taking into account the effect of confinement. The stress state in a composite column is determined by taking into account the non-linear relationship of modulus of elasticity and Poisson’s ratio on the stress level in the concrete core. The effect of confinement occurs at a high stress level when structural steel acts in tension and concrete in lateral compression. The stress state of a composite beam is determined taking into account non-linear dependence on the position of neutral axis. In order to improve the stress state of a composite element and increase the safety of the construction the appropriate strength of steel and concrete has to be applied. The safety of high-stressed composite structures can be achieved by using high-performance concrete (HPC). In this study stress analysis of the composite column and beam is performed with the purpose of obtaining the maximum load-bearing capacity and enhance the safety of the structure by using components with the appropriate strength and by taking into account the composite action. The effect of HPC on the stress state and load carrying capacity of composite elements is analysed.

Structural, dielectric and magnetic properties of ZnFe2O4-Na0.5Bi0.5TiO3 multiferroic composites

NASA Astrophysics Data System (ADS)

Bhasin, Tanvi; Agarwal, Ashish; Sanghi, Sujata; Yadav, Manisha; Tuteja, Muskaan; Singh, Jogender; Rani, Sonia

2018-04-01

Multiferroic xNa0.5Bi0.5TiO3-(1-x)ZnFe2O4 (x=0.10, 0.20) composites were prepared by conventional solid state reaction method. Rietveld analysis of XRD data shows that samples exhibit both cubic (Fd-3m) and rhombohedral (R3c) crystal structure. Structural parameters and unit cell volume of samples vary with composition. The dielectric constant and dielectric loss (tanδ) display dispersion at low frequency due to space charge polarization and inhomogeneity in the composites. Magnetic analysis depicts the antiferromagnetic behavior of composites and magnetization is enhanced with the introduction of ferrite (ZnFe2O4) phase.

Piezoresistive effect of the carbon nanotube yarn embedded axially into the 3D braided composite

NASA Astrophysics Data System (ADS)

Ma, Xin; Cao, Xiaona

2018-06-01

A new method for monitoring 3D braided composite structure health in real time by embedding the carbon nanotube yarn, based on its piezoresistivity, in the composite axially has been designed. The experimental system for piezoresistive effect detection of the carbon nanotube yarn in the 3D braided composite was built, and the sensing characteristics has been analyzed for further research. Compared with other structural health monitoring methods, the monitoring technique with carbon nanotubes yarns is more suitable for internal damage detection immediately, in addition the strength of the composite can be increased by embedding carbon nanotubes yarns. This method can also be used for strain sensing, the development of intelligent materials and structure systems.

Versatile hydrothermal synthesis of one-dimensional composite structures

NASA Astrophysics Data System (ADS)

Luo, Yonglan

2008-12-01

In this paper we report on a versatile hydrothermal approach developed to fabricate one-dimensional (1D) composite structures. Sulfur and selenium formed liquid and adsorbed onto microrods as droplets and subsequently reacted with metallic ion in solution to produce nanoparticles-decorated composite microrods. 1D composites including ZnO/CdS, ZnO/MnS, ZnO/CuS, ZnO/CdSe, and FeOOH/CdS were successfully made using this hydrothermal strategy and the growth mechanism was also discussed. This hydrothermal strategy is simple and green, and can be extended to the synthesis of various 1D composite structures. Moreover, the interaction between the shell nanoparticles and the one-dimensional nanomaterials were confirmed by photoluminescence investigation of ZnO/CdS.

Evaluation of flawed composite structural components under static and cyclic loading. [fatigue life of graphite-epoxy composite materials

NASA Technical Reports Server (NTRS)

Porter, T. R.

1979-01-01

The effects of initial defects on the fatigue and fracture response of graphite-epoxy composite laminates are presented. The structural laminates investigated were a typical angle ply laminate, a polar/hoop wound pressure vessel laminate, and a typical engine fan blade laminate. Defects investigated were full and half penetration circular holes, full and half penetration slits, and countersink holes. The effects of the defect size and type on the static fracture strength, fatigue performance, and residual static strength are shown as well as the results of loadings on damage propagation in composite laminates. The data obtained were used to define proof test levels as a qualification procedure in composite structure subjected to cyclic loading.

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.

Infrared thermographic evaluation of marine composite structures

NASA Astrophysics Data System (ADS)

Jones, Thomas S.

1995-06-01

Glass fiber composite materials have been used for many years in the construction of pleasure, cruising, and racing marine vessels. These vessels have demonstrated excellent performance characteristics and have been reliable in service. Even so, as with all material systems, they are subject to damage from accident, neglect, and abuse. Traditional nondestructive inspection approaches are not always fully effective for examining composite marine structures. Infrared imaging offers a particularly attractive approach for the inspection of composite material structures. Glass fiber composites frequently possess a combination of thermal properties that make them good candidates for infrared thermographic evaluation while other nondestructive evaluation approaches provide limited success. Infrared thermography combines the advantages of being nondestructive with the capability of rapidly inspecting wide surface areas.

Layerwise mechanics and finite element for the dynamic analysis of piezoelectric composite plates

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.; Heyliger, Paul R.; Hopkins, Dale A.

1996-01-01

Laminate and structural mechanics for the analysis of laminated composite plate structures with piezoelectric actuators and sensors are presented. The theories implement layerwise representations of displacements and electric potential, and can model both the global and local electromechanical response of smart composite laminates. Finite-element formulations are developed for the quasi-static and dynamic analysis of smart composite structures containing piezoelectric layers. Comparisons with an exact solution illustrate the accuracy, robustness and capability of the developed mechanics to capture the global and local response of thin and/or thick laminated piezoelectric plates. Additional correlations and numerical applications demonstrate the unique capabilities of the mechanics in analyzing the static and free-vibration response of composite plates with distributed piezoelectric actuators and sensors.

Computational simulation of composite structures with and without damage. M.S. Thesis Final Report

NASA Technical Reports Server (NTRS)

Wilt, Thomas F.

1994-01-01

A methodology is described which uses finite element analysis of various laminates to computationally simulate the effects of delamination damage initiation and growth on the structural behavior of laminated composite structures. The delamination area is expanded according to a set pattern. As the delamination area increases, how the structural response of the laminate changes with respect to buckling and strain energy release rate are investigated. Rules are presented for laminates of different configurations, materials and thickness. These results demonstrate that computational simulation methods can provide alternate methods to investigate the complex delamination damage mechanisms found in composite structures.

A Comparison of Metallic, Composite and Nanocomposite Optimal Transonic Transport Wings

NASA Technical Reports Server (NTRS)

Kennedy, Graeme J.; Kenway, Gaetan K. W.; Martins, Joaquim R. R.

2014-01-01

Current and future composite material technologies have the potential to greatly improve the performance of large transport aircraft. However, the coupling between aerodynamics and structures makes it challenging to design optimal flexible wings, and the transonic flight regime requires high fidelity computational models. We address these challenges by solving a series of high-fidelity aerostructural optimization problems that explore the design space for the wing of a large transport aircraft. We consider three different materials: aluminum, carbon-fiber reinforced composites and an hypothetical composite based on carbon nanotubes. The design variables consist of both aerodynamic shape (including span), structural sizing, and ply angle fractions in the case of composites. Pareto fronts with respect to structural weight and fuel burn are generated. The wing performance in each case is optimized subject to stress and buckling constraints. We found that composite wings consistently resulted in lower fuel burn and lower structural weight, and that the carbon nanotube composite did not yield the increase in performance one would expect from a material with such outstanding properties. This indicates that there might be diminishing returns when it comes to the application of advanced materials to wing design, requiring further investigation.

Solidification of Magnesium (AM50A) / vol%. SiCp composite

NASA Astrophysics Data System (ADS)

Zhang, X.; Hu, H.

2012-01-01

Magnesium matrix composite is one of the advanced lightweight materials with high potential to be used in automotive and aircraft industries due to its low density and high specific mechanical properties. The magnesium composites can be fabricated by adding the reinforcements of fibers or/and particles. In the previous literature, extensive studies have been performed on the development of matrix grain structure of aluminum-based metal matrix composites. However, there is limited information available on the development of grain structure during the solidification of particulate-reinforced magnesium. In this work, a 5 vol.% SiCp particulate-reinforced magnesium (AM50A) matrix composite (AM50A/SiCp) was prepared by stir casting. The solidification behavior of the cast AM50A/SiCp composite was investigated by computer-based thermal analysis. Optical and scanning electron microscopies (SEM) were employed to examine the occurrence of nucleation and grain refinement involved. The results indicate that the addition of SiCp particulates leads to a finer grain structure in the composite compared with the matrix alloy. The refinement of grain structure should be attributed to both the heterogeneous nucleation and the restricted primary crystal growth.

Studying impact damage on carbon-fiber reinforced aircraft composite panels with sonicir

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

Han Xiaoyan; Zhang Ding; He Qi

2011-06-23

Composites are becoming more important materials in commercial aircraft structures such as the fuselage and wings with the new B787 Dreamliner from Boeing which has the target to utilize 50% by weight of composite materials. Carbon-fiber reinforced composites are the material of choice in aircraft structures. This is due to their light weight and high strength (high strength-to-weight ratio), high specific stiffness, tailorability of properties, design flexibility etc. Especially, by reducing the aircraft's body weight by using such lighter structures, the cost of fuel can be greatly reduced with the high jet fuel price for commercial airlines. However, these compositesmore » are prone to impact damage and the damage may occur without any observable sign on the surface, yet resulting in delaminations and disbonds that may occur well within the layers. We are studying the impact problem with carbon-fiber reinforced composite panels and developing SonicIR for this application as a fast and wide-area NDE technology. In this paper, we present our results in studying composite structures including carbon-fiber reinforced composite materials, and preliminary quantitative studies on delamination type defect depth identification in the panels.« less

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.

Intimate contacted two-dimensional/zero-dimensional composite of bismuth titanate nanosheets supported ultrafine bismuth oxychloride nanoparticles for enhanced antibiotic residue degradation.

PubMed

Liu, Wenwen; Dai, Zhiqiang; Liu, Yi; Zhu, Anquan; Zhong, Donglin; Wang, Juan; Pan, Jun

2018-05-31

Constructing a two-dimensional/zero-dimensional (2D/0D) composite with matched crystal structure, suitable energy band structure as well as intimate contact interface is an effective way to improve carriers separation for achieving highly photocatalytic performance. In this work, a novel bismuth titanate/bismuth oxychloride (Bi 4 Ti 3 O 12 /BiOCl) composite consisting of 2D Bi 4 Ti 3 O 12 nanosheets and 0D BiOCl nanoparticles was constructed for the first time. Germinating ultrafine BiOCl nanoparticles on Bi 4 Ti 3 O 12 nanosheets can provide abundant contact interface and shorten migration distance of photoinduced carriers via two-step synthesis contained molten salt process and facile chemical transformation process. The obtained Bi 4 Ti 3 O 12 /BiOCl 2D/0D composites exhibited enhanced photocatalytic performance for antibiotic tetracycline hydrochloride degradation. The rate constant of optimal Bi 4 Ti 3 O 12 /BiOCl composite was about 4.4 times higher than that of bare Bi 4 Ti 3 O 12 although Bi 4 Ti 3 O 12 /BiOCl composite appeared lesser photoabsorption. The enhanced photocatalytic performance can be mainly ascribed to matched crystal structure, suitable energy band structure and intimate contact interface between Bi 4 Ti 3 O 12 nanosheets and ultrafine BiOCl nanoparticles as well as unique 2D/0D composite structure. Besides, a probable degradation mechanism on the basis of active species trapping experiments, electrochemical impedance spectroscopy, photocurrent responses and energy band structures was proposed. This work may be stretched to other 2D/0D composite photocatalysts construction, which is inspiring for antibiotic residue treatment. Copyright © 2018 Elsevier Inc. All rights reserved.

Processing composite materials

NASA Technical Reports Server (NTRS)

Baucom, R. M.

1982-01-01

The fabrication of several composite structural articles including DC-10 upper aft rudders, L-1011 vertical fins and composite biomedical appliances are discussed. Innovative composite processing methods are included.

Synthesis of P(AM-co-MAA)/AEM composite microspheres with lichi-like surface structure using porous microgel as template.

PubMed

Yang, Juxiang; Hu, Daodao; Xue, Min; Yang, Xing

2014-03-15

The P(AM-co-MAA)/AEM composite microspheres with lichi-like structure were synthesized by the hydrolysis and condensation of 3-(trimethoxysilyl)-propyldimethyloctadecyl-ammonium chloride (AEM) located within porous poly(acrylamide-co-methylacrylic acid) (P(AM-co-MAA)) microgels in an ammonia water atmosphere. The morphology and composition of the composite microspheres were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), Fourier transform infrared spectrometer (FI-IR), and X-ray photoelectron spectroscopy (XPS), respectively. The results indicated that the composite microspheres with lichi-like surface structure could be obtained by controlling the loaded amount of AEM, the hydrolysis-condensation time of AEM, and the cross-linking degree of the porous P(AM-co-MAA) microgels. On the basis of the results, the mechanism on the formation of the microspheres with lichi-like surface structure was proposed. The multiple factors play a role in the formation of the specific surface morphology. The pores of the porous microgels make AEM behavior localized; the migration of AEM along with solvent evaporation leads to the structural change; the hydrolysis-condensation of AEM brings the temporarily structural solidification; the surface tension of hydrophobic AEM in hydrophilic atmosphere induces AEM liquid membrane constriction. Although the mechanism is complicated, the method is very simple. Based on the analogous principle, other composite materials with lichi-like structure could be constructed by altering precursor and porous template. Copyright © 2013 Elsevier Inc. All rights reserved.

Cycle oxidation behavior and anti-oxidation mechanism of hot-dipped aluminum coating on TiBw/Ti6Al4V composites with network microstructure.

PubMed

Li, X T; Huang, L J; Wei, S L; An, Q; Cui, X P; Geng, L

2018-04-10

Controlled and compacted TiAl 3 coating was successfully fabricated on the network structured TiBw/Ti6Al4V composites by hot-dipping aluminum and subsequent interdiffusion treatment. The network structure of the composites was inherited to the TiAl 3 coating, which effectively reduces the thermal stress and avoids the cracks appeared in the coating. Moreover, TiB reinforcements could pin the TiAl 3 coating which can effectively improve the bonding strength between the coating and composite substrate. The cycle oxidation behavior of the network structured coating on 873 K, 973 K and 1073 K for 100 h were investigated. The results showed the coating can remarkably improve the high temperature oxidation resistance of the TiBw/Ti6Al4V composites. The network structure was also inherited to the Al 2 O 3 oxide scale, which effectively decreases the tendency of cracking even spalling about the oxide scale. Certainly, no crack was observed in the coating after long-term oxidation due to the division effect of network structured coating and pinning effect of TiB reinforcements. Interfacial reaction between the coating and the composite substrate occurred and a bilayer structure of TiAl/TiAl 2 formed next to the substrate after oxidation at 973 K and 1073 K. The anti-oxidation mechanism of the network structured coating was also discussed.

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

NASA Technical Reports Server (NTRS)

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

2001-01-01

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

Damping Analysis of Cylindrical Composite Structures with Enhanced Viscoelastic Properties

NASA Astrophysics Data System (ADS)

Kliem, Mathias; Høgsberg, Jan; Vanwalleghem, Joachim; Filippatos, Angelos; Hoschützky, Stefan; Fotsing, Edith-Roland; Berggreen, Christian

2018-04-01

Constrained layer damping treatments are widely used in mechanical structures to damp acoustic noise and mechanical vibrations. A viscoelastic layer is thereby applied to a structure and covered by a stiff constraining layer. When the structure vibrates in a bending mode, the viscoelastic layer is forced to deform in shear mode. Thus, the vibration energy is dissipated as low grade frictional heat. This paper documents the efficiency of passive constrained layer damping treatments for low frequency vibrations of cylindrical composite specimens made of glass fibre-reinforced plastics. Different cross section geometries with shear webs have been investigated in order to study a beneficial effect on the damping characteristics of the cylinder. The viscoelastic damping layers are placed at different locations within the composite cylinder e.g. circumferential and along the neutral plane to evaluate the location-dependent efficiency of constrained layer damping treatments. The results of the study provide a thorough understanding of constrained layer damping treatments and an improved damping design of the cylindrical composite structure. The highest damping is achieved when placing the damping layer in the neutral plane perpendicular to the bending load. The results are based on free decay tests of the composite structure.

Li-Ion Localization and Energetics as a Function of Anode Structure.

PubMed

McNutt, Nicholas W; McDonnell, Marshall; Rios, Orlando; Keffer, David J

2017-03-01

In this work, we study the effect of carbon composite anode structure on the localization and energetics of Li-ions. A computational molecular dynamics study is combined with experimental results from neutron scattering experiments to understand the effect of composite density, crystallite size, volume fraction of crystalline carbon, and ion loading on the nature of ion storage in novel, lignin-derived composite materials. In a recent work, we demonstrated that these carbon composites display a fundamentally different mechanism for Li-ion storage than traditional graphitic anodes. The edges of the crystalline and amorphous fragments of aromatic carbon that exist in these composites are terminated by hydrogen atoms, which play a crucial role in adsorption. In this work, we demonstrate how differences in composite structure due to changes in the processing conditions alter the type and extent of the interface between the amorphous and crystalline domains, thus impacting the nature of Li-ion storage. The effects of structural properties are evaluated using a suite of pair distribution functions as well as an original technique to extract archetypal structures, in the form of three-dimensional atomic density distributions, from highly disordered systems. The energetics of Li-ion binding are understood by relating changes in the energy and charge distributions to changes in structural properties. The distribution of Li-ion energies reveals that some structures lead to greater chemisorption, while others have greater physisorption. Carbon composites with a high volume fraction of small crystallites demonstrate the highest ion storage capacity because of the high interfacial area between the crystalline and amorphous domains. At these interfaces, stable H atoms, terminating the graphitic crystallites, provide favorable sites for reversible Li adsorption.

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.

Genetic variability and ontogeny predict microbiome structure in a disease-challenged montane amphibian.

PubMed

Griffiths, Sarah M; Harrison, Xavier A; Weldon, Ché; Wood, Michael D; Pretorius, Abigail; Hopkins, Kevin; Fox, Graeme; Preziosi, Richard F; Antwis, Rachael E

2018-06-25

Amphibian populations worldwide are at risk of extinction from infectious diseases, including chytridiomycosis caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). Amphibian cutaneous microbiomes interact with Bd and can confer protective benefits to the host. The composition of the microbiome itself is influenced by many environment- and host-related factors. However, little is known about the interacting effects of host population structure, genetic variation and developmental stage on microbiome composition and Bd prevalence across multiple sites. Here we explore these questions in Amietia hymenopus, a disease-affected frog in southern Africa. We use microsatellite genotyping and 16S amplicon sequencing to show that the microbiome associated with tadpole mouthparts is structured spatially, and is influenced by host genotype and developmental stage. We observed strong genetic structure in host populations based on rivers and geographic distances, but this did not correspond to spatial patterns in microbiome composition. These results indicate that demographic and host genetic factors affect microbiome composition within sites, but different factors are responsible for host population structure and microbiome structure at the between-site level. Our results help to elucidate complex within- and among- population drivers of microbiome structure in amphibian populations. That there is a genetic basis to microbiome composition in amphibians could help to inform amphibian conservation efforts against infectious diseases.

Structural tailoring of engine blades (STAEBL)

NASA Technical Reports Server (NTRS)

Platt, C. E.; Pratt, T. K.; Brown, K. W.

1982-01-01

A mathematical optimization procedure was developed for the structural tailoring of engine blades and was used to structurally tailor two engine fan blades constructed of composite materials without midspan shrouds. The first was a solid blade made from superhybrid composites, and the second was a hollow blade with metal matrix composite inlays. Three major computerized functions were needed to complete the procedure: approximate analysis with the established input variables, optimization of an objective function, and refined analysis for design verification.

Structural Composites With Tuned EM Chirality

DTIC Science & Technology

2014-12-23

photonic   crystals .   Tammuz  Dubnov  (7/14  –  9/14)  –  Laboratory  Assistant  -­‐  assisted in the testing...AFRL-OSR-VA-TR-2015-0018 STRUCTURAL COMPOSITES WITH TUNED EM CHIRALITY Siavouche Nemat Nasser UNIVERSITY OF CALIFORNIA SAN DIEGO Final Report 12/23...REPORT Grant/Contract  Title:        STRUCTURAL  COMPOSITES  WITH  TUNED  EM   CHIRALITY     Grant  No.:

Multifunctional fiber reinforced polymer composites using carbon and boron nitride nanotubes

NASA Astrophysics Data System (ADS)

Ashrafi, Behnam; Jakubinek, Michael B.; Martinez-Rubi, Yadienka; Rahmat, Meysam; Djokic, Drazen; Laqua, Kurtis; Park, Daesun; Kim, Keun-Su; Simard, Benoit; Yousefpour, Ali

2017-12-01

Recent progress in nanotechnology has made several nano-based materials available with the potential to address limitations of conventional fiber reinforced polymer composites, particularly in reference to multifunctional structures. Carbon nanotubes (CNTs) are the most prevalent case and offer amazing properties at the individual nanotube level. There are already a few high-profile examples of the use of CNTs in space structures to provide added electrical conductivity for static dissipation and electromagnetic shielding. Boron nitride nanotubes (BNNTs), which are structurally analogous to CNTs, also present a range of attractive properties. Like the more widely explored CNTs, individual BNNTs display remarkable mechanical properties and high thermal conductivity but with contrasting functional attributes including substantially higher thermal stability, high electrical insulation, polarizability, high neutron absorption and transparency to visible light. This presents the potential of employing either or both BNNTs and CNTs to achieve a range of lightweight, functional composites for space structures. Here we present the case for application of BNNTs, in addition to CNTs, in space structures and describe recent advances in BNNT production at the National Research Council Canada (NRC) that have, for the first time, provided sufficiently large quantities to enable commercialization of high-quality BNNTs and accelerate development of chemistry, composites and applications based on BNNTs. Early demonstrations showing the fabrication and limited structural testing of polymer matrix composites, including glass fiber-reinforced composite panels containing BNNTs will be discussed.

Composite structural materials

NASA Technical Reports Server (NTRS)

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

1982-01-01

Research in the basic composition, characteristics, and processng 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 problems. Detailed descriptions of the progress achieved in the various component parts of his program are presented.

Seamless metal-clad fiber-reinforced organic matrix composite structures and process for their manufacture

NASA Technical Reports Server (NTRS)

Bluck, Raymond M. (Inventor); Bush, Harold G. (Inventor); Johnson, Robert R. (Inventor)

1990-01-01

A metallic outer sleeve is provided which is capable of enveloping a hollow metallic inner member having continuous reinforcing fibers attached to the distal end thereof. The inner member is then introduced into outer sleeve until inner member is completely enveloped by outer sleeve. A liquid matrix member is then injected into space between inner member and outer sleeve. A pressurized heat transfer medium is flowed through the inside of inner member, thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. thereby forming a fiber reinforced matrix composite material. The wall thicknesses of both inner member and outer sleeve are then reduced to the appropriate size by chemical etching, to adjust the thermal expansion coefficient of the metal-clad composite structure to the desired value. The novelty of this invention resides in the development of a efficient method of producing seamless metal clad fiber reinforced organic matrix composite structures.

Grassland vegetation and bird communities in the southern Great Plains of North America

USGS Publications Warehouse

Chapman, R.N.; Engle, David M.; Masters, R.E.; Leslie, David M.

2004-01-01

Structure and composition of vegetation and abundance of breeding birds in grasslands seeded to Old World bluestem (Bothriochloa ischmaeum) were compared to native mixed prairie in the southern Great Plains of North America. Abundance of birds was determined using fixed-radius point counts. Detrended correspondence analysis was used to compare plant community composition and canonical correspondence analysis was used to examine the relationships between plant species composition and vegetation structure with the bird community. Plant species composition differed distinctly between seeded grassland and native mixed prairie, but the differences were not reflected in habitat structure, bird community composition, or abundance of bird species. Seeded grassland was inferior to native mixed prairie in terms of diversity of plant species, but that difference did not translate into meaningful differences in structure that drove habitat selection by breeding birds. Conservation programs that promote establishment of seeded grassland and do not allow for suitable disturbance regimes will selectively benefit a narrow suite of birds regardless of plant species composition. ?? 2004 Elsevier B.V. All rights reserved.

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.

Inspecting Composites with Airborne Ultrasound: Through Thick and Thin

NASA Astrophysics Data System (ADS)

Hsu, David K.; Barnard, Daniel J.

2006-03-01

The inspection of composite materials and structures with air-coupled ultrasound has the obvious advantage that it is non-contact, non-contaminating, and free from couplants. However, the transmission efficiency from air to solid is extremely low due to the enormous difference in acoustic impedance. The development of more efficient airborne ultrasonic transducers over the years has made it possible, and even practical, to inspect composites with airborne ultrasound. It is now possible to drive newer, more efficient transducers with a portable ultrasonic flaw detector to inspect 2-inch thick solid CFRP in air. In this paper we describe our experience in applying air-coupled ultrasound to the inspection of a variety of composite structures, from honeycomb with thin composite facesheet to very thick solid laminates. General considerations for making airborne ultrasonic measurement in composite are given, and mechanism of transmission through honeycomb core, and resonance effects in transmitting through thick laminates will be described. NDE results of defects and damage in various composite structures will be presented.

Thermo-viscoelastic analysis of composite materials, volume 1

NASA Technical Reports Server (NTRS)

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

1988-01-01

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

Progressive Failure Analysis Methodology for Laminated Composite Structures

NASA Technical Reports Server (NTRS)

Sleight, David W.

1999-01-01

A progressive failure analysis method has been developed for predicting the failure of laminated composite structures under geometrically nonlinear deformations. The progressive failure analysis uses C(exp 1) shell elements based on classical lamination theory to calculate the in-plane stresses. Several failure criteria, including the maximum strain criterion, Hashin's criterion, and Christensen's criterion, are used to predict the failure mechanisms and several options are available to degrade the material properties after failures. The progressive failure analysis method is implemented in the COMET finite element analysis code and can predict the damage and response of laminated composite structures from initial loading to final failure. The different failure criteria and material degradation methods are compared and assessed by performing analyses of several laminated composite structures. Results from the progressive failure method indicate good correlation with the existing test data except in structural applications where interlaminar stresses are important which may cause failure mechanisms such as debonding or delaminations.

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.

Ink composition for making a conductive silver structure

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

Walker, Steven B.; Lewis, Jennifer A.

An ink composition for making a conductive silver structure comprises a silver salt and a complex of (a) a complexing agent and a short chain carboxylic acid or (b) a complexing agent and a salt of a short chain carboxylic acid, according to one embodiment. A method for making a silver structure entails combining a silver salt and a complexing agent, and then adding a short chain carboxylic acid or a salt of the short chain carboxylic acid to the combined silver salt and a complexing agent to form an ink composition. A concentration of the complexing agent in themore » ink composition is reduced to form a concentrated formulation, and the silver salt is reduced to form a conductive silver structure, where the concentrated formulation and the conductive silver structure are formed at a temperature of about 120.degree. C. or less.« less

Phase-Separated Polyaniline/Graphene Composite Electrodes for High-Rate Electrochemical Supercapacitors.

PubMed

Wu, Jifeng; Zhang, Qin'e; Zhou, An'an; Huang, Zhifeng; Bai, Hua; Li, Lei

2016-12-01

Polyaniline/graphene hydrogel composites with a macroscopically phase-separated structure are prepared. The composites show high specific capacitance and excellent rate performance. Further investigation demonstrates that polyaniline inside the graphene hydrogel has low rate performance, thus a phase-separated structure, in which polyaniline is mainly outside the graphene hydrogel matrix, can enhance the rate performance of the composites. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nano-structured polymer composites and process for preparing same

DOEpatents

Hillmyer, Marc; Chen, Liang

2013-04-16

A process for preparing a polymer composite that includes reacting (a) a multi-functional monomer and (b) a block copolymer comprising (i) a first block and (ii) a second block that includes a functional group capable of reacting with the multi-functional monomer, to form a crosslinked, nano-structured, bi-continuous composite. The composite includes a continuous matrix phase and a second continuous phase comprising the first block of the block copolymer.

Processing and Characterization of Basalt Fiber Reinforced Ceramic Composites for High Temperature Applications Using Polymer Precursors

NASA Technical Reports Server (NTRS)

Cox, Sarah B.; Lui, Donovan; Gou, Jihua

2014-01-01

The development of high temperature structural composite materials has been very limited due to the high cost of the materials and the processing needed. Polymer Derived Ceramics (PDCs) begin as a polymer matrix, which allows a shape to be formed prior to the cure, and is then pyrolized in order to obtain a ceramic with the associated thermal and mechanical properties. The two PDCs used in this development are polysiloxane and polycarbosilane. Basalt fibers are used for the reinforcement in the composite system. The use of basalt in structural and high temperature applications has been under development for over 50 years, yet there has been little published research on the incorporation of basalt fibers as a reinforcement in composites. Continuous basalt fiber reinforced PDCs have been fabricated and tested for the applicability of this composite system as a high temperature structural composite material.

Development of Stitched, Braided and Woven Composite Structures in the ACT Program and at Langley Research Center

NASA Technical Reports Server (NTRS)

Dow, Marvin B.; Dexter, H. Benson

1997-01-01

Summary results are presented from the research conducted on woven, braided, knitted and stitched (textile) composites at the Langley Research Center and under the NASA Advanced Composites Technology (ACT) Program in the period from 1985 to 1997. The report also includes an annotated bibliography of 270 U.S. publications on textile composites (with their abstracts). Two major research areas are discussed: (1) the general research in textile composites performed throughout the period under the direction of the Langley Research Center and (2) the development of textile composite aircraft structures by industry under the NASA ACT Program. The annotated bibliography is organized in three subsections: (1) general textiles R&D under the auspices of Langley, (2) ACT Program development of textile structural components, and (3) textiles research by individuals and organizations not associated with the ACT Program. An author index is provided for the reports and documents.

Graphene/vanadium oxide nanotubes composite as electrode material for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Fu, Meimei; Ge, Chongyong; Hou, Zhaohui; Cao, Jianguo; He, Binhong; Zeng, Fanyan; Kuang, Yafei

2013-07-01

Graphene/vanadium oxide nanotubes (VOx-NTs) composite was successfully synthesized through the hydrothermal process in which acetone as solvent and 1-hexadecylamine (HDA) as structure-directing template were used. Morphology, structure and composition of the as-obtained composite were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, nitrogen isothermal adsorption/desorption and thermo gravimetric analysis (TGA). The composite with the VOx-NTs amount of 69.0 wt% can deliver a specific capacitance of 210 F/g at a current density of 1 A/g in 1 M Na2SO4 aqueous solution, which is nearly twice as that of pristine graphene (128 F/g) or VOx-NTs (127 F/g), and exhibit a good performance rate. Compared with pure VOx-NTs, the cycle stability of the composite was also greatly improved due to the enhanced conductivity of the electrode and the structure buffer role of graphene.

Highly birefringent polymer microstructured optical fibers embedded in composite materials

NASA Astrophysics Data System (ADS)

Lesiak, P.; SzelÄ g, M.; Kuczkowski, M.; Domański, A. W.; Woliński, T. R.

2013-05-01

Composite structures are made from two or more constituent materials with significantly different physical or chemical properties and they remain separate and distinct in a macroscopic level within the finished structure. This feature allows for introducing highly birefringent polymer microstructured optical fibers into the composite material. These new fibers can consist of only two polymer materials (PMMA and PC) with similar value of the Young modulus as the composite material so any stresses induced in the composite material can be easily measured by the proposed embedded fiber optic sensors.

Influence of Tree Species Composition and Community Structure on Carbon Density in a Subtropical Forest

PubMed Central

Hu, Yanqiu; Su, Zhiyao; Li, Wenbin; Li, Jingpeng; Ke, Xiandong

2015-01-01

We assessed the impact of species composition and stand structure on the spatial variation of forest carbon density using data collected from a 4-ha plot in a subtropical forest in southern China. We found that 1) forest biomass carbon density significantly differed among communities, reflecting a significant effect of community structure and species composition on carbon accumulation; 2) soil organic carbon density increased whereas stand biomass carbon density decreased across communities, indicating that different mechanisms might account for the accumulation of stand biomass carbon and soil organic carbon in the subtropical forest; and 3) a small number of tree individuals of the medium- and large-diameter class contributed predominantly to biomass carbon accumulation in the community, whereas a large number of seedlings and saplings were responsible for a small proportion of the total forest carbon stock. These findings demonstrate that both biomass carbon and soil carbon density in the subtropical forest are sensitive to species composition and community structure, and that heterogeneity in species composition and stand structure should be taken into account to ensure accurate forest carbon accounting. PMID:26317523

Stimulation of processes of self-propagating high temperature synthesis in system Ti + Al at low temperatures by influence of γ-quanta

NASA Astrophysics Data System (ADS)

Sobachkin, A. V.; Loginova, M. V.; Sitnikov, A. A.; Yakovlev, V. I.; Filimonov, V. Yu; Gradoboev, A. V.

2018-03-01

In the present work, the influence of the irradiation with gamma-quanta 60Co upon the structural and phase state of the components of the mechanically activated powder composition of Ti+Al is investigated. The phase composition, structural parameters, and crystallinity are examined by means of X-ray diffractometry. It is found out that the irradiation with gamma-quanta changes the structure of the mechanically activated powder composition. The higher irradiation dose, the higher the structure crystallinity of both components with no change in phase state. At the same time, the parameters of Ti and Al crystal lattices approach to the initial parameters observed before the mechanical activation. The irradiation with gammaquanta leads to decrease of internal stresses in the mechanically activated powder composition while nanocrystallinity of the structure remains unchanged. Using of powder compositions exposed to the irradiation with gamma-quanta for the SH-synthesis helps to increase speed of the reaction, decrease the peak firing temperature and improve homogeneity, as well as the main phase of the produced material is TiAl.

A novel method for preparing pomegranate-structured FePO{sub 4}/C composite materials as cathode for lithium-ion batteries

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

Hao, Guan-nan; State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029; Zhang, Hao, E-mail: dr.h.zhang@hotmail.com

2012-12-15

Graphical abstract: Display Omitted Highlights: ► We designed and synthesized a pomegranate-structured FePO{sub 4}/C composite. ► We used a combination of electrospinning and solid-state reaction for preparation. ► We showed how the performance of pomegranate-structured FePO{sub 4} is highly enhanced. -- Abstract: A pomegranate-structured FePO{sub 4}/C composite was synthesized via a combination of electrospinning and high temperature reaction using micron-level FePO{sub 4} and polyacrylonitrile (PAN). Systematic studies on synthesis, modification, and characterization of FePO{sub 4}/C composites were conducted. The FePO{sub 4}/C composites delivered a specific discharge capacity of 109 mAh g{sup −1} at 0.2 C and 39 mAh g{sup −1}more » at 10 C, which were comparable with the reported nanometer-level FePO{sub 4}. We demonstrated that the three-dimensional net-like structure covered by porous carbon layers could highly enhance the electrochemical performance of FePO{sub 4}.« less

Influence of Tree Species Composition and Community Structure on Carbon Density in a Subtropical Forest.

PubMed

Hu, Yanqiu; Su, Zhiyao; Li, Wenbin; Li, Jingpeng; Ke, Xiandong

2015-01-01

We assessed the impact of species composition and stand structure on the spatial variation of forest carbon density using data collected from a 4-ha plot in a subtropical forest in southern China. We found that 1) forest biomass carbon density significantly differed among communities, reflecting a significant effect of community structure and species composition on carbon accumulation; 2) soil organic carbon density increased whereas stand biomass carbon density decreased across communities, indicating that different mechanisms might account for the accumulation of stand biomass carbon and soil organic carbon in the subtropical forest; and 3) a small number of tree individuals of the medium- and large-diameter class contributed predominantly to biomass carbon accumulation in the community, whereas a large number of seedlings and saplings were responsible for a small proportion of the total forest carbon stock. These findings demonstrate that both biomass carbon and soil carbon density in the subtropical forest are sensitive to species composition and community structure, and that heterogeneity in species composition and stand structure should be taken into account to ensure accurate forest carbon accounting.

AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics, and Materials Conference, 34th and AIAA/ASME Adaptive Structures Forum, La Jolla, CA, Apr. 19-22, 1993, Technical Papers. Pts. 1-6

NASA Astrophysics Data System (ADS)

Topics addressed include the prediction of helicopter component loads using neural networks, spacecraft on-orbit coupled loads analysis, hypersonic flutter of a curved shallow panel with aerodynamic heating, thermal-acoustic fatigue of ceramic matrix composite materials, transition elements based on transfinite interpolation, damage progression in stiffened composite panels, a direct treatment of min-max dynamic response optimization problems, and sources of helicopter rotor hub inplane shears. Also discussed are dynamics of a layered elastic system, confidence bounds on structural reliability, mixed triangular space-time finite elements, advanced transparency development for USAF aircraft, a low-velocity impact on a graphite/PEEK, an automated mode-tracking strategy, transonic flutter suppression by a passive flap, a nonlinear response of composite panels to random excitation, an optimal placement of elastic supports on a simply supported plate, a probabilistic assessment of composite structures, a model for mode I failure of laminated composites, a residual flexibility approach to multibody dynamics,and multilayer piezoelectric actuators.

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.

Application of Pi Preform Composite Joints in Fabrication of NASA Composite Crew Module Demonstration Structure

NASA Technical Reports Server (NTRS)

Higgins, John E.; Pelham, Larry

2008-01-01

This paper will describe unique and extensive use of pre-woven and impregnated pi cross-sections in fabrication of a carbon composite demonstration structure for the Composite Crew Module (CCM) Program. The program is managed by the NASA Safety and Engineering Center with participants from ten NASA Centers and AFRL. Multiple aerospace contractors are participating in the design development, tooling and fabrication effort as well. The goal of the program is to develop an agency wide design team for composite habitable spacecraft. The specific goals for this development project are: a) To gain hands on experience in design, building and testing a composite crew module. b) To validate key assumptions by resolving composite spacecraft design details through fabrication and testing of hardware. This paper will focus on the design and fabrication issues supporting selection of the Lockheed Martin patented Pi pre-form to provide sound composite joints a numerous locations in the structure. This abstract is based on Preliminary Design data. The final design will continue to evolve through the fall of 2007 with fabrication mostly completed by conference date.

A study on the utilization of advanced composites in commercial aircraft wing structure

NASA Technical Reports Server (NTRS)

Watts, D. J.

1978-01-01

A study was conducted to define the technology and data needed to support the introduction of advanced composite materials in the wing structure of future production aircraft. The study accomplished the following: (1) definition of acceptance factors, (2) identification of technology issues, (3) evaluation of six candidate wing structures, (4) evaluation of five program options, (5) definition of a composite wing technology development plan, (6) identification of full-scale tests, (7) estimation of program costs for the total development plan, (8) forecast of future utilization of composites in commercial transport aircraft and (9) identification of critical technologies for timely program planning.

A continuum deformation theory for metal-matrix composites at high temperature

NASA Technical Reports Server (NTRS)

Robinson, D. N.

1987-01-01

A continuum theory is presented for representing the high temperature, time dependent, hereditary deformation behavior of metallic composites that can be idealized as pseudohomogeneous continua with locally definable directional characteristics. Homogenization of textured materials (molecular, granular, fibrous) and applicability of continuum mechanics in structural applications depends on characteristic body dimensions, the severity of gradients (stress, temperature, etc.) in the structure and the relative size of the internal structure (cell size) of the material. The point of view taken here is that the composite is a material in its own right, with its own properties that can be measured and specified for the composite as a whole.

An experimental investigation on the three-point bending behavior of composite laminate

NASA Astrophysics Data System (ADS)

A, Azzam; W, Li

2014-08-01

The response of composite laminate structure to three-point bending load was investigated by subjecting two types of stacking sequences of composite laminate structure by using electronic universal tester (Type: WDW-20) machine. Optical microscope was selected in order to characterize bending damage, delamination, and damage shapes in composite laminate structures. The results showed that the [0/90/-45/45]2s exhibits a brittle behavior, while other laminates exhibit a progressive failure mode consisting of fiber failure, debonding (splitting), and delamination. The [45/45/90/0]2s laminate has a highly nonlinear load- displacement curve due to compressive yielding.

Stiff, Strong Splice For A Composite Sandwich Structure

NASA Technical Reports Server (NTRS)

Schmaling, D.

1991-01-01

New type of splice for composite sandwich structure reduces peak shear stress in structure. Layers of alternating fiber orientation interposed between thin ears in adhesive joint. Developed for structural joint in spar of helicopter rotor blade, increases precision of control over thickness of adhesive at joint. Joint easy to make, requires no additional pieces, and adds little weight.

Composite Structure Optimization with Genetic Algorithm

NASA Astrophysics Data System (ADS)

Deslandes, Olivier

2014-06-01

In the frame of optimization studies in CNES launcher directorate structure, thermic and material department, the need of an optimization tool based on metaheuristic and finite element models for composite structural dimensioning was underlined.Indeed, composite structures need complex optimization methodologies in order to be really compared to metallic structures with regard to mass, static strength and stiffness constraints (metallic structures using optimization methods better known).After some bibliography research, the use of a genetic algorithm coupled with design of experiment to generate the initial population was chosen. Academic functions were used to validate the optimization process and then it was applied to an industrial study aiming to optimize an interstage skirt with regard to its mass, stiffness and stability (global buckling).

Application study of filamentary composites in a commercial jet aircraft fuselage

NASA Technical Reports Server (NTRS)

Johnson, R. W.; June, R. R.

1972-01-01

A study of applications of filamentary composite materials to aircraft fuselage structure was performed. General design criteria were established and material studies conducted using the 727-200 forebody as the primary structural component. Three design approaches to the use of composites were investigated: uniaxial reinforcement of metal structure, uniaxial and biaxial reinforcement of metal structure, and an all-composite design. Materials application studies for all three concepts were conducted on fuselage shell panels, keel beam, floor beams, floor panels, body frames, fail-safe straps, and window frames. Cost benefit studies were conducted and developmental program costs estimated. On the basis of weight savings, cost effectiveness, developmental program costs, and potential for early application on commercial aircraft, the unaxial design is recommended for a 5-year flight service evaluation program.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

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

1998-01-01

Structural durability, damage tolerance, and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

Damage Progression in Bolted Composites

NASA Technical Reports Server (NTRS)

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

1998-01-01

Structural durability,damage tolerance,and progressive fracture characteristics of bolted graphite/epoxy composite laminates are evaluated via computational simulation. Constituent material properties and stress and strain limits are scaled up to the structure level to evaluate the overall damage and fracture propagation for bolted composites. Single and double bolted composite specimens with various widths and bolt spacings are evaluated. The effect of bolt spacing is investigated with regard to the structural durability of a bolted joint. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulations. Results show the damage progression sequence and structural fracture resistance during different degradation stages. A procedure is outlined for the use of computational simulation data in the assessment of damage tolerance, determination of sensitive parameters affecting fracture, and interpretation of experimental results with insight for design decisions.

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

NASA Technical Reports Server (NTRS)

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

1986-01-01

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

Meso-Mechanics and Meso-Structures: A Matter of Scale

NASA Technical Reports Server (NTRS)

Chamis, Christos C.; Gotsis, P. K.; Mital, S. K.

1998-01-01

Meso-mechanics and meso-structures are described in terms of the scales at which they are observed and formulated. Select composite examples are presented to illustrate that meso-mechanics and/or meso-structures are meaningful only when they refer to a specific scale in a hierarchical scale observation/simulation. These examples include different types of composite unit cells, woven fabric unit cells, and progressive fracture as a composite enhanced infrastructure made from reinforced concrete. The results from the select examples indicate that meso-mechanics and meso-structures are elusive terms and depend mainly on the investigators' knowledge and available information.

Assessment of state-of-the-art of in-service inspection methods for graphite epoxy composite structures on commercial transport aircraft

NASA Technical Reports Server (NTRS)

Phelps, M. L.

1979-01-01

A survey was conducted to determine current in-service inspection practices for all types of aircraft structure and particularly for advanced composite structures. The survey consisted of written questionnaires to commercial airlines, visits to airlines, aircraft manufacturers, and government agencies, and a literature search. Details of the survey including visits, questions asked, a bibliography of reviewed literature and details of the results are reported. From the results, a current in-service inspection baseline and a preliminary inspection program for advanced composite structures is documented as appendices to the report.

Structural failure; International Symposium on Structural Crashworthiness, 2nd, Massachusetts Institute of Technology, Cambridge, June 6-8, 1988, Invited Lectures

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

Wierzbicki, T.; Jones, N.

1989-01-01

The book discusses the fragmentation of solids under dynamic loading, the debris-impact protection of space structures, the controlled fracturing of structures by shock-wave interaction and focusing, the tearing of thin metal sheets, and the dynamic inelastic failure of beams, and dynamic rupture of shells. Consideration is also given to investigations of the failure of brittle and composite materials by numerical methods, the energy absorption of polymer matrix composite structures (frictional effects), the mechanics of deep plastic collapse of thin-walled structures, the denting and bending of tubular beams under local loads, the dynamic bending collapse of strain-softening cantilever beams, and themore » failure of bar structures under repeated loading. Other topics discussed are on the behavior of composite and metallic superstructures under blast loading, the catastrophic failure modes of marine structures, and industrial experience with structural failure.« less

Coupled mixed-field laminate theory and finite element for smart piezoelectric composite shell structures

NASA Technical Reports Server (NTRS)

Saravanos, Dimitris A.

1996-01-01

Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors.

Advances in joining newer structural materials; Proceedings of the International Conference, Montreal, Canada, July 23-25, 1990

NASA Astrophysics Data System (ADS)

The present conference on advances in joining novel structural materials encompasses such material types as ceramics, plastics and composites, and new metallic materials. Specific issues addressed include the use of conductor electric explosion to join ceramics, the effects of brazing temperature on joint properties of SiC-fiber-reinforced Al-alloy-matrix composites, the in situ structure control of composite materials, and the weldability of polymeric materials that are heterogeneous as to chemical nature from the standpoint of morphology. Also addressed are the joining of the Al-Li alloy 8090, diffusion bonding of a creep-resistant Fe-ODS alloy, the adhesive bonding of zinc-coated steel sheets, welds in thermoplastic composite materials, and hot-melt joints for carbon-fiber-reinforced composites.

Adhesion characterization and defect sizing of sandwich honeycomb composites.

PubMed

Ndiaye, Elhadji Barra; Maréchal, Pierre; Duflo, Hugues

2015-09-01

Defects may appear in composite structures during their life cycle. A 10MHz 128 elements phased array transducer was investigated to characterize join bonds and defects in sandwich honeycomb composite structures. An adequate focal law throughout the composite skin gives the ultrasonic dispersive properties of the composite skin and glue layer behind. The resulting B-scan cartographies allow characterizing locally the honeycomb adhesion. Experimental measurements are compared in good agreement with the Debye Series Method (DSM). In the processed C-scan image, flaws are detectable and measurable, localized both in the scanning plane and in the thickness of the composite skin. Copyright © 2015 Elsevier B.V. All rights reserved.

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

Ahn, Cheol Hyoun; Hee Kim, So; Gu Yun, Myeong

In this study, we proposed the artificially designed channel structure in oxide thin-film transistors (TFTs) called a “step-composition gradient channel.” We demonstrated Al step-composition gradient Al-Zn-O (AZO) channel structures consisting of three AZO layers with different Al contents. The effects of stacking sequence in the step-composition gradient channel on performance and electrical stability of bottom-gate TFT devices were investigated with two channels of inverse stacking order (ascending/descending step-composition). The TFT with ascending step-composition channel structure (5 → 10 → 14 at. % Al composition) showed relatively negative threshold voltage (−3.7 V) and good instability characteristics with a reduced threshold voltage shift (Δmore » 1.4 V), which was related to the alignment of the conduction band off-set within the channel layer depending on the Al contents. Finally, the reduced Al composition in the initial layer of ascending step-composition channel resulted in the best field effect mobility of 4.5 cm{sup 2}/V s. We presented a unique active layer of the “step-composition gradient channel” in the oxide TFTs and explained the mechanism of adequate channel design.« less

Strength and fatigue life evaluation of composite laminate with embedded sensors

NASA Astrophysics Data System (ADS)

Rathod, Vivek T.; Hiremath, S. R.; Roy Mahapatra, D.

2014-04-01

Prognosis regarding durability of composite structures using various Structural Health Monitoring (SHM) techniques is an important and challenging topic of research. Ultrasonic SHM systems with embedded transducers have potential application here due to their instant monitoring capability, compact packaging potential toward unobtrusiveness and noninvasiveness as compared to non-contact ultrasonic and eddy current techniques which require disassembly of the structure. However, embedded sensors pose a risk to the structure by acting as a flaw thereby reducing life. The present paper focuses on the determination of strength and fatigue life of the composite laminate with embedded film sensors like CNT nanocomposite, PVDF thin films and piezoceramic films. First, the techniques of embedding these sensors in composite laminates is described followed by the determination of static strength and fatigue life at coupon level testing in Universal Testing Machine (UTM). Failure mechanisms of the composite laminate with embedded sensors are studied for static and dynamic loading cases. The coupons are monitored for loading and failure using the embedded sensors. A comparison of the performance of these three types of embedded sensors is made to study their suitability in various applications. These three types of embedded sensors cover a wide variety of applications, and prove to be viable in embedded sensor based SHM of composite structures.

Application of Composite Structures in Bridge Engineering. Problems of Construction Process and Strength Analysis

NASA Astrophysics Data System (ADS)

Flaga, Kazimierz; Furtak, Kazimierz

2015-03-01

Steel-concrete composite structures have been used in bridge engineering from decades. This is due to rational utilisation of the strength properties of the two materials. At the same time, the reinforced concrete (or prestressed) deck slab is more favourable than the orthotropic steel plate used in steel bridges (higher mass, better vibration damping, longer life). The most commonly found in practice are composite girder bridges, particularly in highway bridges of small and medium spans, but the spans may reach over 200 m. In larger spans steel truss girders are applied. Bridge composite structures are also employed in cable-stayed bridge decks of the main girder spans of the order of 600, 800 m. The aim of the article is to present the cionstruction process and strength analysis problems concerning of this type of structures. Much attention is paid to the design and calculation of the shear connectors characteristic for the discussed objects. The authors focused mainly on the issues of single composite structures. The effect of assembly states on the stresses and strains in composite members are highlighted. A separate part of problems is devoted to the influence of rheological factors, i.e. concrete shrinkage and creep, as well as thermal factors on the stresses and strains and redistribution of internal forces.

ACEE composite structures technology

NASA Technical Reports Server (NTRS)

James, A. M.

1984-01-01

Topics addressed include: strength and hygrothermal response of L-1011 fin components; wing fuel containment and damage tolerance development; impact dynamics; acoustic transmission; fuselage structure; composite transport wing technology development; spar/assembly concepts.

Development of Textile Reinforced Composites for Aircraft Structures

NASA Technical Reports Server (NTRS)

Dexter, H. Benson

1998-01-01

NASA has been a leader in development of composite materials for aircraft applications during the past 25 years. In the early 1980's NASA and others conducted research to improve damage tolerance of composite structures through the use of toughened resins but these resins were not cost-effective. The aircraft industry wanted affordable, robust structures that could withstand the rigors of flight service with minimal damage. The cost and damage tolerance barriers of conventional laminated composites led NASA to focus on new concepts in composites which would incorporate the automated manufacturing methods of the textiles industry and which would incorporate through-the-thickness reinforcements. The NASA Advanced Composites Technology (ACT) Program provided the resources to extensively investigate the application of textile processes to next generation aircraft wing and fuselage structures. This paper discusses advanced textile material forms that have been developed, innovative machine concepts and key technology advancements required for future application of textile reinforced composites in commercial transport aircraft. Multiaxial warp knitting, triaxial braiding and through-the-thickness stitching are the three textile processes that have surfaced as the most promising for further development. Textile reinforced composite structural elements that have been developed in the NASA ACT Program are discussed. Included are braided fuselage frames and window-belt reinforcements, woven/stitched lower fuselage side panels, stitched multiaxial warp knit wing skins, and braided wing stiffeners. In addition, low-cost processing concepts such as resin transfer molding (RTM), resin film infusion (RFI), and vacuum-assisted resin transfer molding (VARTM) are discussed. Process modeling concepts to predict resin flow and cure in textile preforms are also discussed.

Investigating accidents involving aircraft manufactured from polymer composite materials

NASA Astrophysics Data System (ADS)

Dunn, Leigh

This study looks into the examination of polymer composite wreckage from the perspective of the aircraft accident investigator. It develops an understanding of the process of wreckage examination as well as identifying the potential for visual and macroscopic interpretation of polymer composite aircraft wreckage. The in-field examination of aircraft wreckage, and subsequent interpretations of material failures, can be a significant part of an aircraft accident investigation. As the use of composite materials in aircraft construction increases, the understanding of how macroscopic failure characteristics of composite materials may aid the field investigator is becoming of increasing importance.. The first phase of this research project was to explore how investigation practitioners conduct wreckage examinations. Four accident investigation case studies were examined. The analysis of the case studies provided a framework of the wreckage examination process. Subsequently, a literature survey was conducted to establish the current level of knowledge on the visual and macroscopic interpretation of polymer composite failures. Relevant literature was identified and a compendium of visual and macroscopic characteristics was created. Two full-scale polymer composite wing structures were loaded statically, in an upward bending direction, until each wing structure fractured and separated. The wing structures were subsequently examined for the existence of failure characteristics. The examination revealed that whilst characteristics were present, the fragmentation of the structure destroyed valuable evidence. A hypothetical accident scenario utilising the fractured wing structures was developed, which UK government accident investigators subsequently investigated. This provided refinement to the investigative framework and suggested further guidance on the interpretation of polymer composite failures by accident investigators..

Workshop on Smart Structures (1st) Held at The University of Texas at Arlington on September 22-24 1993. Collection of Extended Abstracts

DTIC Science & Technology

1994-06-01

and Optimization of Composite and Sandwich Panels Using Piezoelectric Stiffeners-Actuators" Z. Chaudhry, T. Ganino and Craig A. Rogers, Virginia...Mitigation’ Abu S. Islam and Kevin C. Craig, Rensselaer Polytechnic Institute * ’Damage Detection in Composite Structures Using Piezoelectric Materials" H...Singh, L. Y. Lo and J. S. Sirkis, University of Maryland "Meaningful Damage Evolution Tracking In Composites Using Structurally Embedded Optical Fiber

Failure mechanisms in energy-absorbing composite structures

NASA Astrophysics Data System (ADS)

Johnson, Alastair F.; David, Matthew

2010-11-01

Quasi-static tests are described for determination of the energy-absorption properties of composite crash energy-absorbing segment elements under axial loads. Detailed computer tomography scans of failed specimens were used to identify local compression crush failure mechanisms at the crush front. These mechanisms are important for selecting composite materials for energy-absorbing structures, such as helicopter and aircraft sub-floors. Finite element models of the failure processes are described that could be the basis for materials selection and future design procedures for crashworthy structures.

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.

On the structure of nonlinear constitutive equations for fiber reinforced composites

NASA Technical Reports Server (NTRS)

Jansson, Stefan

1992-01-01

The structure of constitutive equations for nonlinear multiaxial behavior of transversely isotropic fiber reinforced metal matrix composites subject to proportional loading was investigated. Results from an experimental program were combined with numerical simulations of the composite behavior for complex stress to reveal the full structure of the equations. It was found that the nonlinear response can be described by a quadratic flow-potential, based on the polynomial stress invariants, together with a hardening rule that is dominated by two different hardening mechanisms.

Analytical and experimental investigation of aircraft metal structures reinforced with filamentary composites. Phase 3: Major component development

NASA Technical Reports Server (NTRS)

Bryson, L. L.; Mccarty, J. E.

1973-01-01

Analytical and experimental investigations, performed to establish the feasibility of reinforcing metal aircraft structures with advanced filamentary composites, are reported. Aluminum-boron-epoxy and titanium-boron-epoxy were used in the design and manufacture of three major structural components. The components were representative of subsonic aircraft fuselage and window belt panels and supersonic aircraft compression panels. Both unidirectional and multidirectional reinforcement concepts were employed. Blade penetration, axial compression, and inplane shear tests were conducted. Composite reinforced structural components designed to realistic airframe structural criteria demonstrated the potential for significant weight savings while maintaining strength, stability, and damage containment properties of all metal components designed to meet the same criteria.

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

Xu, Wu; Canfield, Nathan L.; Zhang, Ji-Guang

Methods for making composite anodes, such as macroporous composite anodes, are disclosed. Embodiments of the methods may include forming a tape from a slurry including a substrate metal precursor, an anode active material, a pore-forming agent, a binder, and a solvent. A laminated structure may be prepared from the tape and sintered to produce a porous structure, such as a macroporous structure. The macroporous structure may be heated to reduce a substrate metal precursor and/or anode active material. Macroporous composite anodes formed by some embodiments of the disclosed methods comprise a porous metal and an anode active material, wherein themore » anode active material is both externally and internally incorporated throughout and on the surface of the macroporous structure.« less

Joining of porous silicon carbide bodies

DOEpatents

Bates, Carl H.; Couhig, John T.; Pelletier, Paul J.

1990-05-01

A method of joining two porous bodies of silicon carbide is disclosed. It entails utilizing an aqueous slip of a similar silicon carbide as was used to form the porous bodies, including the sintering aids, and a binder to initially join the porous bodies together. Then the composite structure is subjected to cold isostatic pressing to form a joint having good handling strength. Then the composite structure is subjected to pressureless sintering to form the final strong bond. Optionally, after the sintering the structure is subjected to hot isostatic pressing to further improve the joint and densify the structure. The result is a composite structure in which the joint is almost indistinguishable from the silicon carbide pieces which it joins.

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

NASA Technical Reports Server (NTRS)

Kemp, D. E.

1977-01-01

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

Computer-aided design of polymers and composites

NASA Technical Reports Server (NTRS)

Kaelble, D. H.

1985-01-01

This book on computer-aided design of polymers and composites introduces and discusses the subject from the viewpoint of atomic and molecular models. Thus, the origins of stiffness, strength, extensibility, and fracture toughness in composite materials can be analyzed directly in terms of chemical composition and molecular structure. Aspects of polymer composite reliability are considered along with characterization techniques for composite reliability, relations between atomic and molecular properties, computer aided design and manufacture, polymer CAD/CAM models, and composite CAD/CAM models. Attention is given to multiphase structural adhesives, fibrous composite reliability, metal joint reliability, polymer physical states and transitions, chemical quality assurance, processability testing, cure monitoring and management, nondestructive evaluation (NDE), surface NDE, elementary properties, ionic-covalent bonding, molecular analysis, acid-base interactions, the manufacturing science, and peel mechanics.

Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures

DTIC Science & Technology

1988-03-01

Safety Factors for Use When Designing bolted Joints In GRP," Composites , April 1979, pp. M376. 93. Dastln, S., "Joining and Machining Techniques... MACHINE SPACER LOCKmm STEEL PLATE FASTENER 203 mm OR DOWEL FiN EXTENSOMETER EXTENSOMETER TGAUGE LENGTH ATTACHMENT COMPOSITE - PLATE 31 mm p NOTE: NOT TO...No.427 Behaviour and Analysis of Mechanically Fastened Joints in Composite Structures DTIC CXVTflUTION STATEME~r £ELECTE Approved fm Vubhc sIlam l JUL

Coaxial Electrospinning and Characterization of Core-Shell Structured Cellulose Nanocrystal Reinforced PMMA/PAN Composite Fibers

PubMed Central

Li, Chao; Li, Qingde; Ni, Xiaohui; Liu, Guoxiang; Cheng, Wanli; Han, Guangping

2017-01-01

A modified coaxial electrospinning process was used to prepare composite nanofibrous mats from a poly(methyl methacrylate) (PMMA) solution with the addition of different cellulose nanocrystals (CNCs) as the sheath fluid and polyacrylonitrile (PAN) solution as the core fluid. This study investigated the conductivity of the as-spun solutions that increased significantly with increasing CNCs addition, which favors forming uniform fibers. This study discussed the effect of different CNCs addition on the morphology, thermal behavior, and the multilevel structure of the coaxial electrospun PMMA + CNCs/PAN composite nanofibers. A morphology analysis of the nanofibrous mats clearly demonstrated that the CNCs facilitated the production of the composite nanofibers with a core-shell structure. The diameter of the composite nanofibers decreased and the uniformity increased with increasing CNCs concentrations in the shell fluid. The composite nanofibrous mats had the maximum thermal decomposition temperature that was substantially higher than electrospun pure PMMA, PAN, as well as the core-shell PMMA/PAN nanocomposite. The BET (Brunauer, Emmett and Teller) formula results showed that the specific surface area of the CNCs reinforced core-shell composite significantly increased with increasing CNCs content. The specific surface area of the composite with 20% CNCs loading rose to 9.62 m2/g from 3.76 m2/g for the control. A dense porous structure was formed on the surface of the electrospun core-shell fibers. PMID:28772933

Hierarchical porous structured zeolite composite for removal of ionic contaminants from waste streams and effective encapsulation of hazardous waste.

PubMed

Al-Jubouri, Sama M; Curry, Nicholas A; Holmes, Stuart M

2016-12-15

A hierarchical structured composite made from clinoptilolite supported on date stones carbon is synthesized using two techniques. The composites are manufactured by fixing a natural zeolite (clinoptilolite) to the porous surface of date stones carbon or by direct hydrothermal synthesis on to the surface to provide a supported high surface area ion-exchange material for metal ion removal from aqueous streams. The fixing of the clinoptilolite is achieved using sucrose and citric acid as a binder. The composites and pure clinoptilolite were compared to test the efficacy for the removal of Sr 2+ ions from an aqueous phase. The encapsulation of the Sr 2+ using either vitrification or a geo-polymer addition was tested to ensure that the hazardous waste can be made safe for disposal. The hierarchical structured composites were shown to achieve a higher ion exchange capacity per gram of zeolite than the pure clinoptilolite (65mg/g for the pure natural clinoptilolite and 72mg/g for the pure synthesized clinoptilolite) with the synthesized composite (160mg/g) having higher capacity than the natural clinoptilolite composite (95mg/g). The rate at which the equilibria were established followed the same trend showing the composite structure facilitates diffusion to the ion-exchange sites in the zeolite. Copyright © 2016 Elsevier B.V. All rights reserved.

Introduction to session on materials and structures

NASA Technical Reports Server (NTRS)

Vosteen, L. F.

1978-01-01

A review was given of the development of composites for aircraft. Supporting base technology and the Aircraft Energy Efficiency Composites Program are included. Specific topics discussed include: (1) environmental effects on materials; (2) material quality and chemical characterization; (3) design and analysis methods; (4) structural durability; (5) impact sensitivity; (6) carbon fiber electrical effects; and (7) composite components.

Numerical Study of Effects of Fluid-Structure Interaction on Dynamic Responses of Composite Plates

DTIC Science & Technology

2009-09-01

FORCE LOAD AND CLAMPED BOUNDARY.................73 APPENDIX F: ADDITIONAL FIGURES FOR COMPOSITE DE NSITY EFFECTS WITH CONCE NTRATED FORCE LOAD AND...Structure Strain and Kine tic Energy Comparison for Elastic Modulus Variations with Concentrated Force and Clamped Boundary .........................31...48 Figure 49. Experiment Strain Gage La yout on Underside of Composite Plate

New Approach to Synthesis of Powder and Composite Materials by Electron Beam. Part 1. Technological Features of the Process

NASA Astrophysics Data System (ADS)

Rudskoy, A. I.; Kondrat'ev, S. Yu.; Sokolov, Yu. A.

2016-05-01

Possibilities of electron beam synthesis of structural and tool composite materials are considered. It is shown that a novel process involving mathematical modeling of each individual operation makes it possible to create materials with programmable structure and predictable properties from granules of various specified chemical compositions and sizes.

Effect of fabric structure and polymer matrix on flexural strength, interlaminar shear stress, and energy dissipation of glass fiber-reinforced polymer composites

USDA-ARS?s Scientific Manuscript database

We report the effect of glass fiber structure and the epoxy polymer system on the flexural strength, interlaminar shear stress (ILSS), and energy absorption properties of glass fiber-reinforced polymer (GFRP) composites. Four different GFRP composites were fabricated from two glass fiber textiles of...

Evaluation of Long Composite Struts

NASA Technical Reports Server (NTRS)

Jegley, Dawn C.; Wu, K. Chauncey; Phelps, James E.; McKenney, Martin J.; Oremont, Leonard; Barnard, Ansley

2011-01-01

Carbon-epoxy tapered struts are structurally efficient and offer opportunities for weight savings on aircraft and spacecraft structures. Seven composite struts were designed, fabricated and experimentally evaluated through uniaxial loading. The design requirements, analytical predictions and experimental results are presented. Struts with a tapered composite body and corrugated titanium end fittings successfully supported their design ultimate loads with no evidence of failure.

Effects of defects in composite structures

NASA Technical Reports Server (NTRS)

Sendeckyj, G. P.

1983-01-01

The effect of defects in composite structures is addressed. Defects in laminates such as wrinkles, foreign particles, scratches and breaks are discussed. Effects of plygap plywaviness and machining defects are also studied.

Graphene-copper composite with micro-layered grains and ultrahigh strength

PubMed Central

Wang, Lidong; Yang, Ziyue; Cui, Ye; Wei, Bing; Xu, Shichong; Sheng, Jie; Wang, Miao; Zhu, Yunpeng; Fei, Weidong

2017-01-01

Graphene with ultrahigh intrinsic strength and excellent thermal physical properties has the potential to be used as the reinforcement of many kinds of composites. Here, we show that very high tensile strength can be obtained in the copper matrix composite reinforced by reduced graphene oxide (RGO) when micro-layered structure is achieved. RGO-Cu powder with micro-layered structure is fabricated from the reduction of the micro-layered graphene oxide (GO) and Cu(OH)2 composite sheets, and RGO-Cu composites are sintered by spark plasma sintering process. The tensile strength of the 5 vol.% RGO-Cu composite is as high as 608 MPa, which is more than three times higher than that of the Cu matrix. The apparent strengthening efficiency of RGO in the 2.5 vol.% RGO-Cu composite is as high as 110, even higher than that of carbon nanotube, multilayer graphene, carbon nano fiber and RGO in the copper matrix composites produced by conventional MLM method. The excellent tensile and compressive strengths, high hardness and good electrical conductivity are obtained simultaneously in the RGO-Cu composites. The results shown in the present study provide an effective method to design graphene based composites with layered structure and high performance. PMID:28169306

Critical joints in large composite primary aircraft structures. Volume 2: Technology demonstration test report

NASA Technical Reports Server (NTRS)

Bunin, Bruce L.

1985-01-01

A program was conducted to develop the technology for critical structural joints in composite wing structure that meets all the design requirements of a 1990 commercial transport aircraft. The results of four large composite multirow bolted joint tests are presented. The tests were conducted to demonstrate the technology for critical joints in highly loaded composite structure and to verify the analytical methods that were developed throughout the program. The test consisted of a wing skin-stringer transition specimen representing a stringer runout and skin splice on the wing lower surface at the side of the fuselage attachment. All tests were static tension tests. The composite material was Toray T-300 fiber with Ciba-Geigy 914 resin in 10 mil tape form. The splice members were metallic, using combinations of aluminum and titanium. Discussions are given of the test article, instrumentation, test setup, test procedures, and test results for each of the four specimens. Some of the analytical predictions are also included.

Recent progress in NASA Langley Research Center textile reinforced composites program

NASA Technical Reports Server (NTRS)

Dexter, H. Benson; Harris, Charles E.; Johnston, Norman J.

1992-01-01

Research was conducted to explore the benefits of textile reinforced composites for transport aircraft primary structures. The objective is to develop and demonstrate the potential of affordable textile reinforced composite materials to meet design properties and damage tolerance requirements of advanced aircraft structural concepts. Some program elements include development of textile preforms, processing science, mechanics of materials, experimental characterization of materials, and development and evaluation of textile reinforced composite structural elements and subcomponents. Textile 3-D weaving, 3-D braiding, and knitting and/or stitching are being compared with conventional laminated tape processes for improved damage tolerance. Through-the-thickness reinforcements offer significant damage tolerance improvements. However, these gains must be weighted against potential loss in in-plane properties such as strength and stiffness. Analytical trade studies are underway to establish design guidelines for the application of textile material forms to meet specific loading requirements. Fabrication and testing of large structural parts are required to establish the potential of textile reinforced composite materials.

Evaluation of Electromagnetic Near-Field Measurement Technique as Non-Destructive Testing for Composite Structures

NASA Astrophysics Data System (ADS)

Raad Hussein, Alaa; Badri Albarody, Thar M.; Megat Yusoff, Puteri Sri Melor Bt

2018-05-01

Nowadays there is no viable non-destructive method that could detect flaws in complex composite products. Such a method could provide unique tools to allow engineers to minimize time consumption and cost during the evaluation of various product parameters without disturbing production. The latest research and development on propagation waves introduce micro, radio and millimetre waves as new potential non-destructive test methods for evaluation of mechanical flaws and prediction of failure in a product during production. This paper focuses on recent developments, usage, classification of electromagnetic waves under the range of radio frequency, millimetre and micro-waves. In addition, this paper reviews the application of propagation wave and proposed a new health monitoring technique based on Doppler Effect for vibration measurement in complex composite structures. Doppler Effect is influenced by dynamic behaviour of the composite structures and both are effect by flaws occurred inside the structure. Composite manufacturers, especially Aerospace industry are demanding these methods comprehensively inspect and evaluate the damages and defects in their products.

Electrochemical Synthesis of Core-Shell-Structured NbC-Fe Composite Powder for Enforcement in Low-Carbon Steel.

PubMed

Li, Hongmei; Song, Qiushi; Xu, Qian; Chen, Ying; Xu, Liang; Man, Tiannan

2017-11-01

An NbC-Fe composite powder was synthesized from an Nb₂O₅/Fe/C mixture by electrochemical reduction and subsequent carbonization in molten CaCl₂-NaCl. The composite has a core-shell structure, in which NbC acts as the cores distributing in the Fe matrix. A strong bonding between NbC and Fe is benefit from the core-shell structure. The sintering and electrochemical reduction processes were investigated to probe the mechanism for the reactions. The results show that NbC particles about several nanometers were embraced by the Fe shell to form a composite about 100 nm in size. This featured structure can feasibly improve the wettability and sinterability of NbC as well as the uniform distribution of the carbide in the cast steel. By adding the composite into steel in the casting process, the grain size of the casted steel was markedly deceased from 1 mm to 500 μm on average, favoring the hardening of the casted steel.

High temperature resin matrix composites for aerospace structures

NASA Technical Reports Server (NTRS)

Davis, J. G., Jr.

1980-01-01

Accomplishments and the outlook for graphite-polyimide composite structures are briefly outlined. Laminates, skin-stiffened and honeycomb sandwich panels, chopped fiber moldings, and structural components were fabricated with Celion/LARC-160 and Celion/PMR-15 composite materials. Interlaminar shear and flexure strength data obtained on as-fabricated specimens and specimens that were exposed for 125 hours at 589 K indicate that epoxy sized and polyimide sized Celion graphite fibers exhibit essentially the same behavior in a PMR-15 matrix composite. Analyses and tests of graphite-polyimide compression and shear panels indicate that utilization in moderately loaded applications offers the potential for achieving a 30 to 50 percent reduction in structural mass compared to conventional aluminum panels. Data on effects of moisture, temperature, thermal cycling, and shuttle fluids on mechanical properties indicate that both LARC-160 and PMR-15 are suitable matrix materials for a graphite-polyimide aft body flap. No technical road blocks to building a graphite-polyimide composite aft body flap are identified.

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.

Design development of graphite primary structures enables SSTO success

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

Biagiotti, V.A.; Yahiro, J.S.; Suh, D.E.

1997-01-01

This paper describes the development of a graphite composite wing and a graphite composite intertank primary structure for application toward Single-Stage to Orbit space vehicles such as those under development in NASA{close_quote}s X-33/Reusable Launch Vehicle (RLV) Program. The trade study and designs are based on a Rockwell vertical take-off and horizontal landing (VTHL) wing-body RLV vehicle. Northrop Grumman{close_quote}s approach using a building block development technique is described. Composite Graphite/Bismaleimide (Gr/BMI) material characterization test results are presented. Unique intertank and wing composite subcomponent test article designs are described and test results to date are presented. Wing and intertank Full Scale Sectionmore » Test Article (FSTA) objectives and designs are outlined. Trade studies, supporting building block testing, and FSTA demonstrations combine to develop graphite primary structure composite technology that enables developing X-33/RLV design programs to meet critical SSTO structural weight and operations performance criteria. {copyright} {ital 1997 American Institute of Physics.}« less

Synthesis, Structure and Antimicrobial Property of Green Composites from Cellulose, Wool, Hair and Chicken Feather

PubMed Central

Tran, Chieu D.; Prosenc, Franja; Franko, Mladen; Benzi, Gerald

2016-01-01

Novel composites between cellulose (CEL) and keratin (KER) from three different sources (wool, hair and chicken feather) were successfully synthesized in a simple one-step process in which butylmethylimidazolium chloride (BMIm+Cl−), an ionic liquid, was used as the sole solvent. The method is green and recyclable because [BMIm+Cl−] used was recovered for reuse. Spectroscopy (FTIR, XRD) and imaging (SEM) results confirm that CEL and KER remain chemically intact and homogeneously distributed in the composites. KER retains some of its secondary structure in the composites. Interestingly, the minor differences in the structure of KER in wool, hair and feather produced pronounced differences in the conformation of their corresponding composites with wool has the highest α-helix content and feather has the lowest content. These results correlate well with mechanical and antimicrobial properties of the composites. Specifically, adding CEL into KER substantially improves mechanical strength of [CEL+KER] composites made from all three different sources, wool, hair and chicken feathers (i.e., [CEL+wool], [CEL+hair] and [CEL+feather]. Since mechanical strength is due to CEL, and CEL has only random structure, [CEL+feather] has, expectedly, the strongest mechanical property because feather has the lowest content of α-helix. Conversely, [CEL+wool] composite has the weakest mechanical strength because wool has the highest α-helix content. All three composites exhibit antibacterial activity against methicillin resistant S. aureus (MRSA). The antibacterial property is due not to CEL but to the protein and strongly depends on the type of the keratin, namely, the bactericidal effect is strongest for feather and weakest for wool. These results together with our previous finding that [CEL+KER] composites can control release of drug such as ciprofloxacin clearly indicate that these composites can potentially be used as wound dressing PMID:27474680

EDITORIAL Smart materials, multifunctional composites, and morphing structures: selected papers from the 20th International Conference on Adaptive Structures and Technologies (ICAST 2009) Smart materials, multifunctional composites, and morphing structures: selected papers from the 20th International Conference on Adaptive Structures and Technologies (ICAST 2009)

NASA Astrophysics Data System (ADS)

Liao, Wei-Hsin

2010-12-01

The 20th International Conference on Adaptive Structures and Technologies (ICAST) was held on 20-22 October 2009 in Hong Kong. This special section of Smart Materials and Structures is derived from the research papers presented at the conference. Of the 106 papers presented at the conference, 11 papers were reviewed and accepted for this special section, following the regular review procedures of the journal. This special section is focused on smart materials, multifunctional composites, and applications on morphing structures. Smart materials. Smart materials are the foundation of adaptive structures and intelligent systems. The development of new materials will lead to significant improvement in various applications. Three articles are focused on the fabrication of new materials and investigation of their behaviors: Barium strontium zirconate titanate ((Ba1-xSrx)(ZrxTi1-x)O3; BSZT, x = 0.25 and 0.75) ceramics with a highly crystalline structure were fabricated using the combustion technique. The microstructure of BSZT powders exhibited an almost-spherical morphology and had a porous agglomerated form. Polyaniline (PANI)/clay nanoparticles with unique core-shell structure were synthesized via Pickering emulsion polymerization. By dispersing PANI/clay nanoparticles in silicone oil, the ER fluid was made. Magnetic field effects were investigated on the deposition rate and surface morphology of chromium nitride coatings deposited by magnetron sputtering for superior hardness, excellent wear and oxidation resistance. The surface morphology of chromium nitride films was also examined by a scanning electron microscope (SEM). Multifunctional composites. Composites are made from two or more constituent materials so they can combine the best properties of different materials. Five papers deal with fabrication, testing, and modeling of various multifunctional composites: A new active structural fiber (ASF) was fabricated by coating a single carbon fiber with a concentric PZT (PbZr0.52Ti0.48O3) shell using electrolytic deposition. This new ASF is expected to have broader applications due to the higher piezoelectric coupling effect with the use of carbon fiber and PZT. The sol-gel technique was employed to deposit lead zirconium titanium (PZT) and silica composite film onto a copper (Cu)/polyimide (PI) flexible structure. The fabricated PZT-silica composite films were then used for flexible actuator and sensor applications. Interfacial properties and hydrophobicity of multifunctional Ni-nanopowder/epoxy composites were evaluated for self-sensing and actuation. The effects of water content on the actuation performance of ionic polymer-metal composites (IPMCs) were investigated experimentally. Multiscale modelling of a composite electroactive polymer structure was developed, in particular for tubular actuators. The models were validated with experimental data. Morphing structures. Three papers relate to morphing skins and structures. Several issues including stiffness and energy consumption were explored: Composite corrugated structures were used as morphing skin panels (MSPs) in the trailing edge region of a scaled morphing aerofoil section. Wind tunnel testing was carried out to demonstrate the MSP concept. Optimization of a variable-stiffness skin was performed for morphing high-lift devices. The objective is to design the structure to have high enough stiffness to withstand aerodynamic loading and yet low enough stiffness to enable morphing. The aerodynamic and actuation loads were taken into consideration during the optimization. Two adaptive and morphing structures were proposed for low-energy consumption or even energy-harvesting green buildings with the use of an optimization process. Searching for optimal solutions was done by means of an evolutionary technique while the compatibility of the resulting configurations of the adaptive envelope was ensured by the virtual force density method. We would like to thank all of the authors for their significant contributions to this special section for Smart Materials and Structures. We are also grateful to all of the reviewers and associate editors who handled the reviews for their time and effort. I would like to express my sincere appreciation to Professor E Garcia, Editor-in-Chief, for his encouragement by providing the opportunity to make this special section. I am indebted to IOP Publishing for their strong support and the staff, in particular publisher Natasha Leeper, for their special attention and excellent service.

Coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures

NASA Technical Reports Server (NTRS)

Mcknight, R. L.; Chen, P. C.; Dame, L. T.; Huang, H.

1992-01-01

Accomplishments are described for the first year effort of a 5-year program to develop a methodology for coupled structural/thermal/electromagnetic analysis/tailoring of graded composite structures. These accomplishments include: (1) the results of the selective literature survey; (2) 8-, 16-, and 20-noded isoparametric plate and shell elements; (3) large deformation structural analysis; (4) eigenanalysis; (5) anisotropic heat transfer analysis; and (6) anisotropic electromagnetic analysis.

Impact of membrane lipid composition on the structure and stability of the transmembrane domain of amyloid precursor protein

PubMed Central

Dominguez, Laura; Foster, Leigh; Straub, John E.; Thirumalai, D.

2016-01-01

Cleavage of the amyloid precursor protein (APP) by γ-secretase is a crucial first step in the evolution of Alzheimer’s disease. To discover the cleavage mechanism, it is urgent to predict the structures of APP monomers and dimers in varying membrane environments. We determined the structures of the C9923−55 monomer and homodimer as a function of membrane lipid composition using a multiscale simulation approach that blends atomistic and coarse-grained models. We demonstrate that the C9923−55 homodimer structures form a heterogeneous ensemble with multiple conformational states, each stabilized by characteristic interpeptide interactions. The relative probabilities of each conformational state are sensitive to the membrane environment, leading to substantial variation in homodimer peptide structure as a function of membrane lipid composition or the presence of an anionic lipid environment. In contrast, the helicity of the transmembrane domain of monomeric C991−55 is relatively insensitive to the membrane lipid composition, in agreement with experimental observations. The dimer structures of human EphA2 receptor depend on the lipid environment, which we show is linked to the location of the structural motifs in the dimer interface, thereby establishing that both sequence and membrane composition modulate the complete energy landscape of membrane-bound proteins. As a by-product of our work, we explain the discrepancy in structures predicted for C99 congener homodimers in membrane and micelle environments. Our study provides insight into the observed dependence of C99 protein cleavage by γ-secretase, critical to the formation of amyloid-β protein, on membrane thickness and lipid composition. PMID:27559086

Autonomous System for Monitoring the Integrity of Composite Fan Housings

NASA Technical Reports Server (NTRS)

Qing, Xinlin P.; Aquino, Christopher; Kumar, Amrita

2010-01-01

A low-cost and reliable system assesses the integrity of composite fan-containment structures. The system utilizes a network of miniature sensors integrated with the structure to scan the entire structural area for any impact events and resulting structural damage, and to monitor degradation due to usage. This system can be used to monitor all types of composite structures on aircraft and spacecraft, as well as automatically monitor in real time the location and extent of damage in the containment structures. This diagnostic information is passed to prognostic modeling that is being developed to utilize the information and provide input on the residual strength of the structure, and maintain a history of structural degradation during usage. The structural health-monitoring system would consist of three major components: (1) sensors and a sensor network, which is permanently bonded onto the structure being monitored; (2) integrated hardware; and (3) software to monitor in-situ the health condition of in-service structures.

Optical feedback structures and methods of making

DOEpatents

None

2014-11-18

An optical resonator can include an optical feedback structure disposed on a substrate, and a composite including a matrix including a chromophore. The composite disposed on the substrate and in optical communication with the optical feedback structure. The chromophore can be a semiconductor nanocrystal. The resonator can provide laser emission when excited.

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

NASA Astrophysics Data System (ADS)

Feng, Yefeng; Zhang, Jianxiong; Hu, Jianbing; Li, Shichun; Peng, Cheng

2018-03-01

Interface induced polarization has a prominent influence on dielectric properties of 0-3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz ( 3.3 times of polymer), loss of 0.07@100 Hz ( 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm ( 10 times of polymer) and discharged energy efficiency of 54%@249 kV/cm ( 5 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

Size-confined fixed-composition and composition-dependent engineered band gap alloying induces different internal structures in L-cysteine-capped alloyed quaternary CdZnTeS quantum dots

NASA Astrophysics Data System (ADS)

Adegoke, Oluwasesan; Park, Enoch Y.

2016-06-01

The development of alloyed quantum dot (QD) nanocrystals with attractive optical properties for a wide array of chemical and biological applications is a growing research field. In this work, size-tunable engineered band gap composition-dependent alloying and fixed-composition alloying were employed to fabricate new L-cysteine-capped alloyed quaternary CdZnTeS QDs exhibiting different internal structures. Lattice parameters simulated based on powder X-ray diffraction (PXRD) revealed the internal structure of the composition-dependent alloyed CdxZnyTeS QDs to have a gradient nature, whereas the fixed-composition alloyed QDs exhibited a homogenous internal structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis confirmed the size-confined nature and monodispersity of the alloyed nanocrystals. The zeta potential values were within the accepted range of colloidal stability. Circular dichroism (CD) analysis showed that the surface-capped L-cysteine ligand induced electronic and conformational chiroptical changes in the alloyed nanocrystals. The photoluminescence (PL) quantum yield (QY) values of the gradient alloyed QDs were 27-61%, whereas for the homogenous alloyed QDs, the PL QY values were spectacularly high (72-93%). Our work demonstrates that engineered fixed alloying produces homogenous QD nanocrystals with higher PL QY than composition-dependent alloying.

Evaluation of composite adhesive bonds using digital image correlation

NASA Astrophysics Data System (ADS)

Shrestha, Shashi Shekhar

Advanced composite materials are widely used for many structural applications in the aerospace/aircraft industries today. Joining of composite structures using adhesive bonding offers several advantages over traditional fastening methods. However, this technique is not yet employed for fastening the primary structures of aircrafts or space vehicles. There are several reasons for this: There are not any reliable non-destructive evaluation (NDE) methods that can quantify the strength of the bonds, and there are no certifications of quality assurance for inspecting the bond quality. Therefore, there is a significant need for an effective, reliable, easy to use NDE method for the analysis of composite adhesive joints. This research aimed to investigate an adhesively bonded composite-aluminum joints of variable bond strength using digital image correlation (DIC). There are many future possibilities in continuing this research work. As the application of composite materials and adhesive bond are increasing rapidly, the reliability of the composite structures using adhesive bond should quantified. Hence a lot of similar research using various adhesive bonds and materials can be conducted for characterizing the behavior of adhesive bond. The results obtained from this research will set the foundation for the development of ultrasonic DIC as a nondestructive approach for the evaluation of adhesive bond line.

Structural, dielectric and magnetic studies of (x) Mg0.2Cu0.3Zn0.5Fe2O4 + (1-x) Ba0.8Zr0.2TiO3 magnetoelectric composites

NASA Astrophysics Data System (ADS)

Khader, S. Abdul; Giridharan, N. V.; Chaudhuri, Arka; Sankarappa, T.

2016-05-01

The Magneto-electric composites (x) Mg0.2Cu0.3Zn0.5Fe2O4 + (1-x) Ba0.8Zr0.2TiO3 (x=15%,30%,45%) were synthesized by sintering mixtures of highly ferroelectric Ba0.8Zr0.2TiO3 (BZT) and highly magneto-strictive component Mg0.2Cu0.3Zn0.5Fe2O4 (MCZF). The presences of two phases in magneto-electric composites were probed by X-ray diffraction (XRD) studies. The peaks observed in the XRD spectrum indicated spinel cubic structure for MCZF ferrite and tetragonal perovskite structure for BZT and, both spinel and pervoskite structures for synthesized composites. Surface morphology of the samples has been investigated using Field Emission Scanning Electron Microscope (FESEM). Frequency dependent dielectric properties of synthesized composites were measured from 100 Hz to 1 MHz at RT using HIOKI LCR HI-TESTER. The dielectric dispersion is observed at lower frequencies for the synthesized ME composites. The magnetic properties of synthesized composites were analyzed using a Vibrating Sample Magnetometer (VSM). It is observed that the values of saturation magnetization increases along with the ferrite content.

Acoustic emission source location in composite structure by Voronoi construction using geodesic curve evolution.

PubMed

Gangadharan, R; Prasanna, G; Bhat, M R; Murthy, C R L; Gopalakrishnan, S

2009-11-01

Conventional analytical/numerical methods employing triangulation technique are suitable for locating acoustic emission (AE) source in a planar structure without structural discontinuities. But these methods cannot be extended to structures with complicated geometry, and, also, the problem gets compounded if the material of the structure is anisotropic warranting complex analytical velocity models. A geodesic approach using Voronoi construction is proposed in this work to locate the AE source in a composite structure. The approach is based on the fact that the wave takes minimum energy path to travel from the source to any other point in the connected domain. The geodesics are computed on the meshed surface of the structure using graph theory based on Dijkstra's algorithm. By propagating the waves in reverse virtually from these sensors along the geodesic path and by locating the first intersection point of these waves, one can get the AE source location. In this work, the geodesic approach is shown more suitable for a practicable source location solution in a composite structure with arbitrary surface containing finite discontinuities. Experiments have been conducted on composite plate specimens of simple and complex geometry to validate this method.

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.

K-shuff: A Novel Algorithm for Characterizing Structural and Compositional Diversity in Gene Libraries.

PubMed

Jangid, Kamlesh; Kao, Ming-Hung; Lahamge, Aishwarya; Williams, Mark A; Rathbun, Stephen L; Whitman, William B

2016-01-01

K-shuff is a new algorithm for comparing the similarity of gene sequence libraries, providing measures of the structural and compositional diversity as well as the significance of the differences between these measures. Inspired by Ripley's K-function for spatial point pattern analysis, the Intra K-function or IKF measures the structural diversity, including both the richness and overall similarity of the sequences, within a library. The Cross K-function or CKF measures the compositional diversity between gene libraries, reflecting both the number of OTUs shared as well as the overall similarity in OTUs. A Monte Carlo testing procedure then enables statistical evaluation of both the structural and compositional diversity between gene libraries. For 16S rRNA gene libraries from complex bacterial communities such as those found in seawater, salt marsh sediments, and soils, K-shuff yields reproducible estimates of structural and compositional diversity with libraries greater than 50 sequences. Similarly, for pyrosequencing libraries generated from a glacial retreat chronosequence and Illumina® libraries generated from US homes, K-shuff required >300 and 100 sequences per sample, respectively. Power analyses demonstrated that K-shuff is sensitive to small differences in Sanger or Illumina® libraries. This extra sensitivity of K-shuff enabled examination of compositional differences at much deeper taxonomic levels, such as within abundant OTUs. This is especially useful when comparing communities that are compositionally very similar but functionally different. K-shuff will therefore prove beneficial for conventional microbiome analysis as well as specific hypothesis testing.

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.

Low density bismaleimide-carbon microballoon composites. [aircraft and submarine compartment safety

NASA Technical Reports Server (NTRS)

Kourtides, D. A.; Parker, J. A. (Inventor)

1978-01-01

A process is described for constructing for a composite laminate structure which exhibits a high resistance to heat and flame provides safer interior structures for aircraft and submarine compartments. Composite laminate structures are prepared by the bismaleimide resin preimpregnation of a fiberglass cloth to form a face sheet which is bonded with a bismaleimide hot melt adhesive to a porous core structure selected from the group consisting of polyamide paper and bismaleimide-glass fabric which is filled with carbon microballoons. The carbon microballoons are prepared by pyrolyzing phenolic micro-balloons in the presence of nitrogen. A slurry of the carbon microballoons is prepared to fill the porous core structure. The porous core structure and face sheet are bonded to provide panel structures exhibiting increased mechanical capacities and lower oxygen limit values and smoke density values.

Bi-Metallic Composite Structures With Designed Internal Residual Stress Field

NASA Technical Reports Server (NTRS)

Brice, Craig A.

2014-01-01

Shape memory alloys (SMA) have a unique ability to recover small amounts of plastic strain through a temperature induced phase change. For these materials, mechanical displacement can be accomplished by heating the structure to induce a phase change, through which some of the plastic strain previously introduced to the structure can be reversed. This paper introduces a concept whereby an SMA phase is incorporated into a conventional alloy matrix in a co-continuous reticulated arrangement forming a bi-metallic composite structure. Through memory activation of the mechanically constrained SMA phase, a controlled residual stress field is developed in the interior of the structure. The presented experimental data show that the memory activation of the SMA composite component significantly changes the residual stress distribution in the overall structure. Designing the structural arrangement of the two phases to produce a controlled residual stress field could be used to create structures that have much improved durability and damage tolerance properties.

Nonlinear Thermoelastic Model for SMAs and SMA Hybrid Composites

NASA Technical Reports Server (NTRS)

Turner, Travis L.

2004-01-01

A constitutive mathematical model has been developed that predicts the nonlinear thermomechanical behaviors of shape-memory-alloys (SMAs) and of shape-memory-alloy hybrid composite (SMAHC) structures, which are composite-material structures that contain embedded SMA actuators. SMAHC structures have been investigated for their potential utility in a variety of applications in which there are requirements for static or dynamic control of the shapes of structures, control of the thermoelastic responses of structures, or control of noise and vibrations. The present model overcomes deficiencies of prior, overly simplistic or qualitative models that have proven ineffective or intractable for engineering of SMAHC structures. The model is sophisticated enough to capture the essential features of the mechanics of SMAHC structures yet simple enough to accommodate input from fundamental engineering measurements and is in a form that is amenable to implementation in general-purpose structural analysis environments.

Experimental Characterization of Aluminum-Based Hybrid Composites Obtained Through Powder Metallurgy

NASA Astrophysics Data System (ADS)

Marcu, D. F.; Buzatu, M.; Ghica, V. G.; Petrescu, M. I.; Popescu, G.; Niculescu, F.; Iacob, G.

2018-06-01

The paper presents some experimental results concerning fabrication through powder metallurgy (P/M) of aluminum-based hybrid composites - Al/Al2O3/Gr. In order to understand the mechanisms that occur during the P/M processes of obtaining Al/Al2O3/Gr composite, we correlated the physical characteristics with their micro-structural characteristics. The characterization was performed using analysis techniques specific for P/M process, SEM-EDS and XRD analyses. Micro-structural characterization of the composites has revealed fairly uniform distribution this resulting in good properties of the final composite material.

Quantitative diagnostics of multilayered composite structures with ultrasonic guided waves

NASA Astrophysics Data System (ADS)

Bunget, Gheorghe; Friedersdorf, Fritz; Na, Jeong K.

2015-03-01

The main objective of the current work is to develop a practical nondestructive inspection methodology for a highly sound absorbing composite structural system consisting of polymeric and metallic materials. Due to constraints in geometrical shapes and thicknesses of the composite system used in this work, ultrasonic guided wave approach has been chosen. Since the polymer coatings have high damping properties, less energy is dissipated into the adjacent media in the presence of interface delaminations. Experimental measurements performed on a targeted composite system, whether it has an aluminum, carbon-fiber-composite, or steel outer casing, show promising results.

Carbon Nanotube Coatings as Used in Strain Sensors for Composite Tanks

NASA Technical Reports Server (NTRS)

Trigwell, Steve; Snyder, Sarah; Hatfield, Walt; Dervishi, Enkeleda; Biris, Alexandru S.

2011-01-01

The next generation of cryogenic fuel tanks, crew habitats and other components for future spacecraft will focus on the usc of lightweight carbon fiber composite materials. A critical issue in the design and optimization of such tanks and structures will bc in structural health monitoring, however, current strain sensors have limitations. In this study, a novel carbon nanotube thin film was applied to carbon fiber composites for structural monitoring. Applying a load using a 3-point bend test to simulate bowing of a tank wall, induced significant increases in the film's electrical resistance at small deflections. Upon release of the load, the resistance returned to its approximate start value and was reproducible over multiple tests. The results show that a carbon nanotube thin film has great potential for the health monitoring of composite structures.

Analyzing The Effect of Skin Postbuckling on General Stresses, Strains and Stability of Composite Structures

NASA Technical Reports Server (NTRS)

Zamula, G. N.; Ierusalimsky, K. M.; Kalmykova, G. S.; Fomin, V. P.

1998-01-01

The present paper is a final technical report within the NCCW-1-233 research program (dated June 1, 1997) accomplished as a part of co-operation between United States' NASA and Russia's Goskomoboronprom in aeronautics, and continues similar NCCW-73 and NCC-1-233 programs accomplished in 1996 and 1997, respectively. The report concludes studies in two domains, "Analyzing the effect of skin postbuckling on general stresses and strains in a composite structure" and "Evaluating the effect of skin postbuckling behavior on general stability of a composite structure"; the work was fulfilled in compliance with NCC-1-233 requirements (as of June 1, 1997). Also, the present studies may be regarded as a partial generalization of efforts in [1, 2] conducted within the above programs in what concerns postbuckling behavior of composite structures.

Composite nonlinear structure within the magnetosonic soliton interactions in a spin-1/2 degenerate quantum plasma

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

Han, Jiu-Ning, E-mail: hanjiuning@126.com; Luo, Jun-Hua; Li, Jun-Xiu

2015-06-15

We study the basic physical properties of composite nonlinear structure induced by the head-on collision of magnetosonic solitons. Solitary waves are assumed to propagate in a quantum electron-ion magnetoplasma with spin-1/2 degenerate electrons. The main interest of the present work is to investigate the time evolution of the merged composite structure during a specific time interval of the wave interaction process. We consider three cases of colliding-situation, namely, compressive-rarefactive solitons interaction, compressive-compressive solitons interaction, and rarefactive-rarefactive solitons interaction, respectively. Compared with the last two colliding cases, the changing process of the composite structure is more complex for the first situation.more » Moreover, it is found that they are obviously different for the last two colliding cases.« less

New Textile Sensors for In Situ Structural Health Monitoring of Textile Reinforced Thermoplastic Composites Based on the Conductive Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) Polymer Complex

PubMed Central

Jerkovic, Ivona; Koncar, Vladan; Grancaric, Ana Marija

2017-01-01

Many metallic structural and non-structural parts used in the transportation industry can be replaced by textile-reinforced composites. Composites made from a polymeric matrix and fibrous reinforcement have been increasingly studied during the last decade. On the other hand, the fast development of smart textile structures seems to be a very promising solution for in situ structural health monitoring of composite parts. In order to optimize composites’ quality and their lifetime all the production steps have to be monitored in real time. Textile sensors embedded in the composite reinforcement and having the same mechanical properties as the yarns used to make the reinforcement exhibit actuating and sensing capabilities. This paper presents a new generation of textile fibrous sensors based on the conductive polymer complex poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) developed by an original roll to roll coating method. Conductive coating for yarn treatment was defined according to the preliminary study of percolation threshold of this polymer complex. The percolation threshold determination was based on conductive dry films’ electrical properties analysis, in order to develop highly sensitive sensors. A novel laboratory equipment was designed and produced for yarn coating to ensure effective and equally distributed coating of electroconductive polymer without distortion of textile properties. The electromechanical properties of the textile fibrous sensors confirmed their suitability for in situ structural damages detection of textile reinforced thermoplastic composites in real time. PMID:28994733

Effect of hybrid layer on stress distribution in a premolar tooth restored with composite or ceramic inlay: an FEM study.

PubMed

Belli, Sema; Eskitaşcioglu, Gürcan; Eraslan, Oguz; Senawongse, Pisol; Tagami, Junji

2005-08-01

The aim of this finite elemental stress analysis study was to evaluate the effect of hybrid layer on distribution and amount of stress formed under occlusal loading in a premolar tooth restored with composite or ceramic inlay. The mandibular premolar tooth was selected as the model based on the anatomical measurements suggested by Wheeler. The analysis is performed by using a Pentium II IBM compatible computer with the SAP 2000 structural analysis program. Four different mathematical models including the following structures were evaluated: 1) composite inlay, adhesive resin, and tooth structure; 2) composite inlay, adhesive resin, hybrid layer, and tooth structure; 3) ceramic inlay, adhesive resin, and tooth structure; 4) ceramic inlay, adhesive resin, hybrid layer, and tooth structure. Loading was applied from the occlusal surface of the restoration, and shear stresses under loading were evaluated. The findings were drawn by the Saplot program, and the results were analyzed by graphical comparison method. The output indicated that the hybrid layer acts as a stress absorber in models 2 and 4. The hybrid layer has also changed mathematical values of stress on cavity floors in both restoration types. Ceramic inlay collected the stress inside the body of the material, but the composite inlay directly transferred the stress through dental tissues. As a result, it was concluded that the hybrid layer has an effect on stress distribution under loading in a premolar tooth model restored with composite or ceramic inlay. Copyright 2005 Wiley Periodicals, Inc.

AST Composite Wing Program: Executive Summary

NASA Technical Reports Server (NTRS)

Karal, Michael

2001-01-01

The Boeing Company demonstrated the application of stitched/resin infused (S/RFI) composite materials on commercial transport aircraft primary wing structures under the Advanced Subsonic technology (AST) Composite Wing contract. This report describes a weight trade study utilizing a wing torque box design applicable to a 220-passenger commercial aircraft and was used to verify the weight savings a S/RFI structure would offer compared to an identical aluminum wing box design. This trade study was performed in the AST Composite Wing program, and the overall weight savings are reported. Previous program work involved the design of a S/RFI-base-line wing box structural test component and its associated testing hardware. This detail structural design effort which is known as the "semi-span" in this report, was completed under a previous NASA contract. The full-scale wing design was based on a configuration for a MD-90-40X airplane, and the objective of this structural test component was to demonstrate the maturity of the S/RFI technology through the evaluation of a full-scale wing box/fuselage section structural test. However, scope reductions of the AST Composite Wing Program pre-vented the fabrication and evaluation of this wing box structure. Results obtained from the weight trade study, the full-scale test component design effort, fabrication, design development testing, and full-scale testing of the semi-span wing box are reported.

Capturing the Energy Absorbing Mechanisms of Composite Structures under Crash Loading

NASA Astrophysics Data System (ADS)

Wade, Bonnie

As fiber reinforced composite material systems become increasingly utilized in primary aircraft and automotive structures, the need to understand their contribution to the crashworthiness of the structure is of great interest to meet safety certification requirements. The energy absorbing behavior of a composite structure, however, is not easily predicted due to the great complexity of the failure mechanisms that occur within the material. Challenges arise both in the experimental characterization and in the numerical modeling of the material/structure combination. At present, there is no standardized test method to characterize the energy absorbing capability of composite materials to aide crashworthy structural design. In addition, although many commercial finite element analysis codes exist and offer a means to simulate composite failure initiation and propagation, these models are still under development and refinement. As more metallic structures are replaced by composite structures, the need for both experimental guidelines to characterize the energy absorbing capability of a composite structure, as well as guidelines for using numerical tools to simulate composite materials in crash conditions has become a critical matter. This body of research addresses both the experimental characterization of the energy absorption mechanisms occurring in composite materials during crushing, as well as the numerical simulation of composite materials undergoing crushing. In the experimental investigation, the specific energy absorption (SEA) of a composite material system is measured using a variety of test element geometries, such as corrugated plates and tubes. Results from several crush experiments reveal that SEA is not a constant material property for laminated composites, and varies significantly with the geometry of the test specimen used. The variation of SEA measured for a single material system requires that crush test data must be generated for a range of different test geometries in order to define the range of its energy absorption capability. Further investigation from the crush tests has led to the development of a direct link between geometric features of the crush specimen and its resulting SEA. Through micrographic analysis, distinct failure modes are shown to be guided by the geometry of the specimen, and subsequently are shown to directly influence energy absorption. A new relationship between geometry, failure mode, and SEA has been developed. This relationship has allowed for the reduction of the element-level crush testing requirement to characterize the composite material energy absorption capability. In the numerical investigation, the LS-DYNA composite material model MAT54 is selected for its suitability to model composite materials beyond failure determination, as required by crush simulation, and its capability to remain within the scope of ultimately using this model for large-scale crash simulation. As a result of this research, this model has been thoroughly investigated in depth for its capacity to simulate composite materials in crush, and results from several simulations of the element-level crush experiments are presented. A modeling strategy has been developed to use MAT54 for crush simulation which involves using the experimental data collected from the coupon- and element-level crush tests to directly calibrate the crush damage parameter in MAT54 such that it may be used in higher-level simulations. In addition, the source code of the material model is modified to improve upon its capability. The modifications include improving the elastic definition such that the elastic response to multi-axial load cases can be accurately portrayed simultaneously in each element, which is a capability not present in other composite material models. Modifications made to the failure determination and post-failure model have newly emphasized the post-failure stress degradation scheme rather than the failure criterion which is traditionally considered the most important composite material model definition for crush simulation. The modification efforts have also validated the use of the MAT54 failure criterion and post-failure model for crash modeling when its capabilities and limitations are well understood, and for this reason guidelines for using MAT54 for composite crush simulation are presented. This research has effectively (a) developed and demonstrated a procedure that defines a set of experimental crush results that characterize the energy absorption capability of a composite material system, (b) used the experimental results in the development and refinement of a composite material model for crush simulation, (c) explored modifying the material model to improve its use in crush modeling, and (d) provided experimental and modeling guidelines for composite structures under crush at the element-level in the scope of the Building Block Approach.

Composite of coated magnetic alloy particle

DOEpatents

Moorhead, Arthur J.; Kim, Hyoun-Ee

2000-01-01

A composite structure and method for manufacturing same, the composite structure being comprised of metal particles and an inorganic bonding media. The method comprises the steps of coating particles of a metal powder with a thin layer of an inorganic bonding media selected from the group of powders consisting of a ceramic, glass, and glass-ceramic. The particles are assembled in a cavity and heat, with or without the addition of pressure, is thereafter applied to the particles until the layer of inorganic bonding media forms a strong bond with the particles and with the layer of inorganic bonding media on adjacent particles. The resulting composite structure is strong and remains cohesive at high temperatures.

Composite of ceramic-coated magnetic alloy particles

DOEpatents

Moorhead, Arthur J.; Kim, Hyoun-Ee

2000-01-01

A composite structure and method for manufacturing same, the composite structure being comprised of metal particles and an inorganic bonding media. The method comprises the steps of coating particles of a metal powder with a thin layer of an inorganic bonding media selected from the group of powders consisting of a ceramic, glass, and glass-ceramic. The particles are assembled in a cavity and heat, with or without the addition of pressure, is thereafter applied to the particles until the layer of inorganic bonding media forms a strong bond with the particles and with the layer of inorganic bonding media on adjacent particles. The resulting composite structure is strong and remains cohesive at high temperatures.

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

Selective generation of laser-induced periodic surface structures on Al2O3-ZrO2-Nb composites

NASA Astrophysics Data System (ADS)

Kunz, Clemens; Bartolomé, José F.; Gnecco, Enrico; Müller, Frank A.; Gräf, Stephan

2018-03-01

Laser-induced periodic surface structures (LIPSS) were selectively fabricated on the metal phase of Al2O3-nZrO2-Nb (78.3-1.7-20 vol.%) ceramic matrix composites. For this purpose, sample surfaces were irradiated with fs-laser pulses (τ = 300 fs, λ = 1025 nm) of different laser peak fluences ranging from 0.23 to 0.40 J/cm2. The structured surfaces were characterised by scanning electron microscopy (SEM), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and by measuring the water contact angle. Well-pronounced LIPSS with a period of Λ ≈ 750 nm and a height of h ≈ 263 nm were found solely on the metal phase of the composite when applying the highest fluence whereas no structural and chemical modifications were found on the surface of the ceramic matrix. This can be explained by the different light absorption behaviour of both phases, which results in different ablation thresholds. The water contact angle of composite surfaces was successfully reduced from 68.4° for untreated samples to 40.9° for structured samples. Selectively structured composites with adjustable wettability are of particular interest for biomedical and tribological applications.

Soil resources and topography shape local tree community structure in tropical forests

PubMed Central

Baldeck, Claire A.; Harms, Kyle E.; Yavitt, Joseph B.; John, Robert; Turner, Benjamin L.; Valencia, Renato; Navarrete, Hugo; Davies, Stuart J.; Chuyong, George B.; Kenfack, David; Thomas, Duncan W.; Madawala, Sumedha; Gunatilleke, Nimal; Gunatilleke, Savitri; Bunyavejchewin, Sarayudh; Kiratiprayoon, Somboon; Yaacob, Adzmi; Supardi, Mohd N. Nur; Dalling, James W.

2013-01-01

Both habitat filtering and dispersal limitation influence the compositional structure of forest communities, but previous studies examining the relative contributions of these processes with variation partitioning have primarily used topography to represent the influence of the environment. Here, we bring together data on both topography and soil resource variation within eight large (24–50 ha) tropical forest plots, and use variation partitioning to decompose community compositional variation into fractions explained by spatial, soil resource and topographic variables. Both soil resources and topography account for significant and approximately equal variation in tree community composition (9–34% and 5–29%, respectively), and all environmental variables together explain 13–39% of compositional variation within a plot. A large fraction of variation (19–37%) was spatially structured, yet unexplained by the environment, suggesting an important role for dispersal processes and unmeasured environmental variables. For the majority of sites, adding soil resource variables to topography nearly doubled the inferred role of habitat filtering, accounting for variation in compositional structure that would previously have been attributable to dispersal. Our results, illustrated using a new graphical depiction of community structure within these plots, demonstrate the importance of small-scale environmental variation in shaping local community structure in diverse tropical forests around the globe. PMID:23256196

Structural Health Monitoring of Composite Plates Under Ambient and Cryogenic Conditions

NASA Technical Reports Server (NTRS)

Engberg, Robert C.

2005-01-01

Methods for structural health monitoring are now being assessed, especially in high-performance, extreme environment, safety-critical applications. One such application is for composite cryogenic fuel tanks. The work presented here attempts to characterize and investigate the feasibility of using imbedded piezoelectric sensors to detect cracks and delaminations under cryogenic and ambient conditions. Different types of excitation and response signals and different sensors are employed in composite plate samples to aid in determining an optimal algorithm, sensor placement strategy, and type of imbedded sensor to use. Variations of frequency and high frequency chirps of the sensors are employed and compared. Statistical and analytic techniques are then used to determine which method is most desirable for a specific type of damage and operating environment. These results are furthermore compared with previous work using externally mounted sensors. More work is needed to accurately account for changes in temperature seen in these environments and be statistically significant. Sensor development and placement strategy are other areas of further work to make structural health monitoring more robust. Results from this and other work might then be incorporated into a larger composite structure to validate and assess its structural health. This could prove to be important in the development and qualification of any 2nd generation reusable launch vehicle using composites as a structural element.

Damage Simulation in Composite Materials: Why It Matters and What Is Happening Currently at NASA in This Area

NASA Technical Reports Server (NTRS)

McElroy, Mack; de Carvalho, Nelson; Estes, Ashley; Lin, Shih-yung

2017-01-01

Use of lightweight composite materials in space and aircraft structure designs is often challenging due to high costs associated with structural certification. Of primary concern in the use of composite structures is durability and damage tolerance. This concern is due to the inherent susceptibility of composite materials to both fabrication and service induced flaws. Due to a lack of general industry accepted analysis tools applicable to composites damage simulation, a certification procedure relies almost entirely on testing. It is this reliance on testing, especially compared to structures comprised of legacy metallic materials where damage simulation tools are available, that can drive costs for using composite materials in aerospace structures. The observation that use of composites can be expensive due to testing requirements is not new and as such, research on analysis tools for simulating damage in composite structures has been occurring for several decades. A convenient approach many researchers/model-developers in this area have taken is to select a specific problem relevant to aerospace structural certification and develop a model that is accurate within that scope. Some examples are open hole tension tests, compression after impact tests, low-velocity impact, damage tolerance of an embedded flaw, and fatigue crack growth to name a few. Based on the premise that running analyses is cheaper than running tests, one motivation that many researchers in this area have is that if generally applicable and reliable damage simulation tools were available the dependence on certification testing could be lessened thereby reducing overall design cost. It is generally accepted that simulation tools if applied in this manner would still need to be thoroughly validated and that composite testing will never be completely replaced by analysis. Research and development is currently occurring at NASA to create numerical damage simulation tools applicable to damage in composites. The Advanced Composites Project (ACP) at NASA Langley has supported the development of composites damage simulation tools in a consortium of aerospace companies with a goal of reducing the certification time of a commercial aircraft by 30%. And while the scope of ACP does not include spacecraft, much of the methodology and simulation capabilities can apply to spacecraft certification in the Space Launch System and Orion programs as well. Some specific applications of composite damage simulation models in a certification program are (1) evaluation of damage during service when maintenance may be difficult or impossible, (2) a tool for early design iterations, (3) gaining insight into a particular damage process and applying this insight towards a test coupon or structural design, and (4) analysis of damage scenarios that are difficult or impossible to recreate in a test. As analysis capabilities improve, these applications and more will become realized resulting in a reduction in cost for use of composites in aerospace vehicles. NASA is engaged in this process from both research and application perspectives. In addition to the background information discussed previously, this presentation covers a look at recent research at NASA in this area and some current/potential applications in the Orion program.

Explosive scabbling of structural materials

DOEpatents

Bickes, Jr., Robert W.; Bonzon, Lloyd L.

2002-01-01

A new approach to scabbling of surfaces of structural materials is disclosed. A layer of mildly energetic explosive composition is applied to the surface to be scabbled. The explosive composition is then detonated, rubbleizing the surface. Explosive compositions used must sustain a detonation front along the surface to which it is applied and conform closely to the surface being scabbled. Suitable explosive compositions exist which are stable under handling, easy to apply, easy to transport, have limited toxicity, and can be reliably detonated using conventional techniques.

Composite Structural Materials

NASA Technical Reports Server (NTRS)

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

1984-01-01

The development and application of filamentary composite materials, is considered. Such interest is based on the possibility of using relatively brittle materials with high modulus, high strength, but low density in composites with good durability and high tolerance to damage. Fiber reinforced composite materials of this kind offer substantially improved performance and potentially lower costs for aerospace hardware. Much progress has been made since the initial developments in the mid 1960's. There were only limited applied to the primary structure of operational vehicles, mainly as aircrafts.