| Durability of Composite Materials and Structures |
02-Nov-2009 |
15 pages |
| Authors:
Hassan Mahfuz; Richard D Granata; William Hartt; Leif Carlsson; Lawrence Drzal; Dayakar Penumadu; Clive Clayton; William Scott; FLORIDA ATLANTIC UNIV BOCA RATON
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 | This project focused on marine composites and sandwich structures with specific interests on the effects of moisture, seawater, hydrostatic pressure, and temperature on their durability and life prediction. One task revealed fiber changes that occur with nitric acid treatment promoting better engineering design of composite fiber matrix interface and interphase region. Comparative environmental exposures show that moisture absorption was along the F/M interface (wicking). A fracture mechanical model of single ... |
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| An Experimental Study of Fiberglass Composites Containing Metal Wire Joints |
Sep-2009 |
54 pages |
| Authors:
Joseph E Klopfer; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| The U.S. Navy has been incorporating increasing amounts of composite materials during construction, especially in the areas of submarine sails and surface ship superstructures. The benefit of using composite material with metal wire layers imbedded is that these metal wire layers may be welded to the steel superstructure of a Naval Vessel resulting in maximum joint strength. Joining a composite structure to a metallic structure required the metal-wire layers to ... |
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| The Use of Commercial Non-Hazardous Air Pollutant Monomers to Optimize the Properties of Fatty Acid-Based Resins |
May-2009 |
34 pages |
| Authors:
James M Sands; La; John J Scala; Priya Kamath; Anita Sahu; Giuseppe R Palmese; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| Vinyl ester (VE) resins are used to make polymer matrix composites in military and commercial applications because of their good properties, low weight, and low cost. These resins typically contain high concentrations of reactive diluents, such as styrene, to allow these resins to be molded using resin transfer molding and other inexpensive liquid molding techniques. Because styrene is a hazardous air pollutant (HAP) and a volatile organic compound (VOC), the ... |
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| Defense Acquisitions: DOD Must Balance Its Needs With Available Resources and Follow an Incremental Approach to Acquiring Weapons Systems |
03-Mar-2009 |
26 pages |
| Authors:
Ron Schwenn; Bruce Thomas; Matt Lea; Michael J Sullivan; Dayna Foster; Susan Neill; Charles Shivers; GOVERNMENT ACCOUNTABILITY OFFICE WASHINGTON DC
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| A broad consensus exists that weapon system problems are serious and that their resolution is overdue. With the federal budget under increasing strain from the nation's economic crisis, the time for change is now. DOD is off to a good start with the recent revisions to its acquisition policy, which, if implemented properly, should provide a foundation for establishing sound, knowledge-based business cases before launching into development and for maintaining ... |
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| Effects of Subzero Temperatures and Sea Water Immersion on Damage Initiation and Growth in Sandwich Composites |
02-Feb-2009 |
17 pages |
| Authors:
Barry D Davidson; SYRACUSE UNIV NY DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| Results are discussed for the project Effects of Subzero Temperatures and Sea water Immersion on Damage Initiation and Growth in Sandwich Composites. This research project focused on (1) assessing the effects of environment and impact damage on the flexural response of sandwich laminates, (2) developing an improved test and associated data reduction method for determining the debonding toughness of sandwich structures, and (3) using this new test to assess the ... |
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| Advanced Nanocrystalline Ceramic Matrix Composites with Improved Toughness |
09-Jan-2009 |
29 pages |
| Authors:
Amiya Mukherjee; Katherine Thomson; CALIFORNIA UNIV DAVIS DEPT OF CHEMICAL ENGINEERING AND MATERIALS SCIENCE
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| Alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes were fabricated by advanced powder processing techniques and consolidated by spark plasma sintering. Raman spectroscopy revealed that single-walled carbon nanotubes (SWCNT) begin to break down at sintering temperatures above 1150 deg C. Nuclear magnetic resonance (NMR) showed that, although thermodynamically unlikely, no Al4C3 formed in the CNT-alumina nanocomposites. Thus, the nanocomposite is purely a physical mixture and no chemical bond was formed ... |
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| Effects of Subzero Temperatures and Sea Water Immersion on Damage Initiation and Growth in Sandwich Composites |
10-Dec-2008 |
34 pages |
| Authors:
Barry D Davidson; SYRACUSE UNIV NY DEPT OF MECHANICAL AND AEROSPACE ENGINEERING
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| Progress during the past six months is described on the project Effects of Subzero Temperatures and Seawater Immersion on Damage Initiation and Growth in Sandwich Composites. Efforts during this period have focused on (1) assessing the effects of environment and impact damage on the flexural response of sandwich laminates, (2) linalizing the improved modified peel test and associated data reduction method for determining the debonding toughness of sandwich structures, and ... |
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| Microstructure and Properties of WC Spheres |
Nov-2008 |
32 pages |
| Authors:
Jeffrey J Swab; Justin Pritchett; Andrew A Wereszczak; Osama M Jadaan; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
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| Tungsten carbide (WC) spheres are used as projectiles to study the ballistic performance of armor materials and systems. In order to properly understand and model the interaction between the projectile and the armor, it is necessary to have properties of both. In this study, the physical and mechanical properties of two commercially available WC spheres (nominally 0.25 inch in diameter) used in some ballistic impact studies were determined. One WC ... |
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| Study of Composite Joint Strength with Carbon Nanotube Reinforcement |
01-Sep-2008 |
70 pages |
| Authors:
Susan D Faulkner; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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| Strengthening of composite joints is a topic of recent research. The benefits of using locally applied carbon nanotubes to reinforce a carbon fiber composite joint were studied. The effect of carbon nanotubes on enhancing the fracture toughness and joint interface strength was investigated by performing Mode I, Mode II, and Mixed Mode I/Mode II fracture with and without carbon nanotubes applied locally at the joint interface. Furthermore, the effects of ... |
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| Oxide Coatings in Aero-Turbine Engines |
28 FEB 2008 |
3 pages |
| Authors:
Anthony G. Evans; John W. Hutchinson; CALIFORNIA UNIV SANTA BARBARA
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| Oxide coatings used for various components in the hot section of aero-turbine engines experience temperature gradients at various stages during their flight cycle. One gradient exists during steady-state, due to the combination of the combustion environment next to the free surface and internal cooling of the underlying superalloy substrate. Other gradients develop during cooling of the surface when engine power is reduced. It is argued that deep delaminations, when observed ... |
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| Manufacturing of a Composite Tailcone for an XM-1002 Training Round |
FEB 2008 |
22 pages |
| Authors:
James M. Sands; Uday Vaidya; George Husman; Juan Serrano; Robert Brannon; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| Recent work on the cost-effective manufacturing of an extrusion-compression molded, long-fiber thermoplastic (LFT) XM-1002 tailcone for training rounds of military ammunition is compiled in this technical report. During the last decade, the engineering community has expanded the use of thermoplastic composites due to their inherent advantages over traditional thermoset composites including: high toughness, inexpensive resin systems, short processing cycle times, recycling potential, excellent environmental resistance, and damage tolerance. Thermoplastic composites ... |
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| Complex Structures for Manned/Unmanned Aerial Vehicles. Delivery Order 0019: Low Temp Composite Processing Mechanical Property Data |
JAN 2008 |
82 pages |
| Authors:
Chris Ridgard; ADVANCED COMPOSITES GROUP INC TULSA OK
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| After several years of effort, a new generation of out of autoclave processable resin systems has been developed which it is believed will replace older oven vacuum bag cure (OVBC) resins such as the Advanced Composites Group, Inc. (ACG) LTM45EL material. The first of these new resins, MTM45 and MTM45-1, have been demonstrated to offer mechanical performance and toughness at a level comparable to that of state-of-the-art toughened resin systems ... |
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| Extracting Stress-Strain and Compressive Yield Stress Information from Spherical Indentation |
SEP 2007 |
24 pages |
| Authors:
Thomas F. Juliano; Mark R. VanLandingham; Tusit Weerasooriya; Paul Moy; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| In recent years, instrumented indentation has become increasingly used to measure mechanical properties such as elastic modulus and fracture toughness at the micrometer scale. In this work, an experimental method is developed to estimate stressstrain behavior using indentation load-displacement and continuous stiffness measurement data. An attempt is made to subtract plastic behavior out of the loading curve to generate stress-strain data from which elastic modulus and yield stress can be ... |
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| The Potential for a Novel Transformation-Toughened Composite |
24 JUL 2007 |
9 pages |
| Authors:
IVAR E. REIMANIS; COLORADO SCHOOL OF MINES GOLDEN
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| Research was conducted to examine the possibility to design a novel transformation-toughened composite utilizing a phase transformation in beta-eucryptite. Specimens comprising zirconium oxide as the matrix and beta-eucryptite as the particulate phase were made with varying amounts of eucryptite particle size. Indentation fracture experiments were conducted and four-point bend notch bars were fabricated. The indentation experiments showed significant crack deflection, suggesting that toughening may occur. However, quantitative results (from the ... |
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| High Performance Fatty Acid-Based Vinyl Ester Resin for Liquid Molding |
JUL 2007 |
16 pages |
| Authors:
Xing Geng; John J. La Scala; James M. Sands; Guiseppe R. Palmese; DREXEL UNIV PHILADELPHIA PA
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| Liquid resins used for molding composite structures are a significant source of volatile organic compounds (VOC) and hazardous air pollutant (HAP) emissions. One effective method of reducing styrene emissions from vinyl ester (VE) resins is to replace some or all of the styrene with fatty acid-based monomers. In our investigation, the styrene was reduced to 20-25 wt% compared to 40-60 wt% associated with commercial products. In addition, fatty acid-based monomers ... |
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| Microstructure Evolution and Mechanical Properties of Severely Plastically Deformed (SPD) Aluminum Alloys |
31 MAY 2007 |
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| Authors:
Surya R. Kalidindi; Roger D. Doherty; Christopher J. Hovanec; Brendon R. Donohue; Ryan J. VanderMeulen; DREXEL UNIV PHILADELPHIA PA DEPT OF MATERIALS SCIENCE AND ENGINEERING
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 | A combined experimental and modeling study has been carried out to characterize the structure and mechanical properties of severely plastically deformed (SPD) aluminum and its alloys as well as the effect of strengthening mechanism on fracture toughness and failure mode. This investigation is focused specifically on Equal Channel Angular Pressing (ECAP) and heavy cold rolling of high solute Al alloys. A particular reason for studying the high strength potentially achievable ... |
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| Nanosilica Modification of Elastomer-Modified VARTM Epoxy Resins for Improved Resin and Composite Toughness |
APR 2007 |
28 pages |
| Authors:
Jason Robinette; Andres Bujanda; Daniel DeSchepper; Jessica Dibelka; Philip Costanzo; Robert Jensen; Steven McKnight; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD
|
| Recent publications have reported a synergy between rubber and silica in modified epoxy resins that results in significantly improved fracture toughness without reductions in other material properties. In this work, we seek to achieve the same type of synergy in commercial vacuum-assisted resin transfer molding (VARTM) epoxy resins, SC15 and SC79, produced by Applied Polymeric, Inc. Nanopox F400 (Hanse Chemie) containing 40 weight-percent epoxy-functional silica in a diglycidyl bisphenol-F (DGEBF) ... |
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| Comparison of Matrix Cracking in High Temperature and Lower Temperature PMCs from Cryogenic Exposure (Preprint) |
MAR 2007 |
11 pages |
| Authors:
Vernon T. Bechel; AIR FORCE RESEARCH LAB WRIGHT-PATTERSON AFB OH STRUCTURAL MATERIALS BRANCH/NONMETALLIC MATERIALS DIV
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| The behavior of a high temperature carbon/polyimide composite, T650/AFR-PE-4, in a cryogenic environment was studied. The results were compared to results from similar testing of a carbon/epoxy and a carbon/bismaleimide composite to begin to scale the difficulties involved with using high temperature polymer matrix composites (PMCs) in cryogen containers on launch vehicles. T650/AFR-PE-4 developed transverse cracks in all plies after fewer cycles than the carbon/bismaleimide (IM7/5250-4) when each was cycled ... |
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| Nanoparticle Control of Void Formation and Expansion in Polymeric and Composite Systems |
FEB 2007 |
9 pages |
| Authors:
James C. Seferis; DELAWARE UNIV NEWARK CENTER FOR COMPOSITE MATERIALS
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| This research focused on a nanoscale modification of traditional polymeric matrix morphology through particle introduction and subsequent void formation. The main areas of research have been a study of interlayer modification and analyses of continued carbon fiber reinforced polymeric matrix composites at the nanoscale. The results showed improvements in toughness up to a critical threshold, after which, an increase in the concentration and size of nanoparticulate matter and corresponding foams ... |
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| SR-1447 Fracture Mechanics Characterization of Aluminum Alloys for Marine Structural Applications |
JAN 2007 |
258 pages |
| Authors:
J. K. Donald; FRACTURE TECHNOLOGY ASSOCIATES PLEASANT VALLEY PA
|
| The Ship Structure Committee (SSC) identified a lack of information required for structural integrity and damage tolerance analyses of aluminum marine structures. The development of such data is vital in light of the increased use of aluminum alloys in marine construction. Under SSC project SR-1447, Fracture Technology Associates was contracted to characterize, through experimental fracture mechanics, the fatigue crack growth (FCG) resistance and fracture toughness of three aluminum alloys (5083, ... |
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| Coatings and Biodegradable and Bioasorbable Films |
28 DEC 2006 |
59 pages |
| Authors:
Shelby F. Thames; James W. Rawlins; UNIVERSITY OF SOUTHERN MISSISSIPPI HATTIESBURG
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| Research and development activities focused on environmentally friendly monomer, polymer and composite materials for Navy coating and packaging needs. Specifically focusing on the plasticizing effects of vegetable oil macromonomers as incorporated into emulsion polymers for efficient almost zero VOC film formation and the additional benefit of auto-oxidative polymerization after application. The resulting formulated coatings met or exceeded each of the specified Military specifications and are currently being evaluated for larger ... |
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| Directionally Solidified Multifunctional Ceramics |
DEC 2006 |
17 pages |
| Authors:
Ali Sayir; CASE WESTERN RESERVE UNIV CLEVELAND OH
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| In order to achieve a significant increase in toughening and to retain the toughness at elevated temperatures a new multifunctional approach is proposed. The multifunctionality were achieved through directional solidification of polyphase materials comprising the load-bearing and functional phases. The functional phases include shape recovery and health monitoring. In parallel, new ideas about the load bearing phases were investigated to achieve tougher materials. |
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| Numerical Simulation and Experiments of Fatigue Crack Growth in Multi-Layer Structures of MEMS and Microelectronic Devices |
DEC 2006 |
282 pages |
| Authors:
Thomas H. Siegmund; PURDUE UNIV LAFAYETTE IN
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| Numerical simulation and experiments on the toughness and fatigue crack growth resistance of MEMS relevant thin film structures are reported. Structures consisting of metal films (aluminum, 0.1 to 2.0 micrometers thickness) confined between elastic substrates (semiconductor wafers) are considered. The study is concerned with the influence of the thickness of the metal film on the fatigue failure response. Numerical simulations of fatigue crack growth are conducted by use of cohesive ... |
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| Modeling Fracture in Z-Pinned Composite Co-Cured Laminates Using Smeared Properties and Cohesive Elements in DYNA3D |
SEP 2006 |
105 pages |
| Authors:
Jason K. Freels; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| The purpose of the present research was three-fold: 1) gain a more sophisticated understanding of the response of co-cured composite joints with and without through-thickness reinforcement (TTR), 2) compare the behavior of specimens reinforced with various sizes and densities of reinforcement, and 3) use experimental data to verify the existing DYNA3D smeared property model. Double cantilever beam, end-notch flexure and T-section specimens reinforced with 0.011" diameter z-pins at 2% and ... |
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| High Strength and Impact Damage Tolerant Syntactic Foam for High Performance Sandwich Structures |
25 JUL 2006 |
31 pages |
| Authors:
Guoqiang Li; SOUTHERN UNIV AND A AND M COLL BATON ROUGE LA DEPT OF MECHANICAL ENGINEERING
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| This study explored a novel higher strength and higher impact tolerant syntactic foam for composite sandwich structures. A unique microstructure was designed and realized through a unique manufacturing technology. The foam was fabricated by dispersing rubber latex coated microballoons into a nanoclay and milled microfiber reinforced epoxy matrix. Each component was designed to contribute to a desired property of the foam. The nanoparticle and microfiber served to increase the strength ... |
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| Stress and Moisture Effects on Thin Film Buckling Delamination |
25 JUL 2006 |
8 pages |
| Authors:
P. Waters; A. A. Volinsky; UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF MECHANICAL ENGINEERING
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| Deposition processes control the properties of thin films; they can also introduce high residual stresses. which can be relieved by delamination and fracture. Tungsten films with high 1-2 GPa compressive residual stresses were sputter deposited on top of thin (below 100 nm) copper and diamond-like carbon (DLC) films. Highly stressed films store large amounts of strain energy. When the strain energy release rate exceeds the films interfacial toughness, delamination occurs. ... |
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| Controlling Hydrogen Embrittlement in Ultra-High Strength Steels |
JUN 2006 |
21 pages |
| Authors:
John R. Scully; Hakan Dogan; Daoming Li; Richard Gangloff; VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| A Fe-13Co-11Ni-3Cr- 1Mo-0.2C steel alloy, processed for ultra-high strength and fracture toughness, exhibits three distinct hydrogen trap states in a complex precipitation hardened martensitic microstructure and is susceptible to severe hydrogen embrittlement (HE) at threshold stress intensity levels as low as 20 MPa square root of m. The causes of HE susceptibility include very high crack-tip tensile stresses and a reservoir of diffusible hydrogen that is trapped reversibly with a ... |
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| Battlemind Training: Building Soldier Resiliency |
APR 2006 |
7 pages |
| Authors:
Carl A. Castro; Charles W. Hoge; Anthony L. Cox; WALTER REED ARMY INST OF RESEARCH SILVER SPRING MD DEPT OF MILITARY PSYCHIATRY
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| Battlemind is a Soldier's inner strength to face fear and adversity in combat with courage. The predeployment Battlemind training program is designed to build Soldier resiliency by developing his/her self-confidence and mental toughness. The training focuses on Soldier strengths, identifying specific actions that Soldiers and leaders can engage in to meet the challenges of combat. The pre-deployment training consists of unique modules for Soldiers, leaders, reservists, and families. The post-deployment ... |
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| Modification of Bisphenol-A Based Bismaleimide Resin (BPA-BMI) with an Allyl-Terminated Hyperbranched Polyimide (AT-PAEKI) |
MAR 2006 |
12 pages |
| Authors:
Haihu Qin; Patrick T. Mather; Jong-Beom Baek; Loon-Seng Tan; CONNECTICUT UNIV STORRS INST OF MATERIALS SCIENCE
|
| As a continuation of previous work involving synthesis of an allyl-functionalized hyperbranched polyimide, AT-PAEKI, we have studied the use of this reactive polymer as a modifier of bisphenol-A based bismaleimide resin (BPA-BMI). This was pursued in anticipation of improvements in processability as well as physical properties including glass transition temperature, elastic modulus, and fracture toughness. Apparent miscibility, indicated by optical clarity with a single Tg, was observed for compositions containing ... |
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| Dynamic Consolidation of TaC and Nano-YSZ Powders (PREPRINT) |
07 FEB 2006 |
10 pages |
| Authors:
Lei Xu; Darrell Marchant; Lawrence Matson; B. S. Majumdar; NEW MEXICO INST OF MINING AND TECHNOLOGY SOCORRO DEPT OF METALLURGICAL AND MATERIALS ENGINEERING
|
| The high melting point of TaC (3880 deg C), second amongst all known materials, along with good corrosion resistance makes TaC a potential candidate for Air Force applications. However, traditional methods of manufacturing, such as hot pressing or HIP-ing, give rise to rapid grain growth and low fracture toughness. In this work, we have utilized dynamic consolidation technique to overcome the grain growth problem, and thereby obtain stronger and more ... |
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| Ab-Initio Calculations of Structure and Properties of Nanolaminated MAX Phases |
27 JAN 2006 |
4 pages |
| Authors:
Jochen M. Schneider; RWTH AACHEN UNIV (GERMANY)
|
| This report results from a contract tasking RWTH Aachen as follows: A new class of machinable ceramic materials had recently received attention due a unique combination of hardness, toughness, machinability, and oxidation stability. These materials are called MAX phases, where M designates a transition metal, A is mostly a IIIA or IVA element of periodic table, and X stands for C or/and N. MAX phases have a unique nanolaminated atom ... |
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| Computational Design of UHTC Materials for Hypersonic Applications (Preprint) |
JAN 2006 |
28 pages |
| Authors:
Triplicane A. Parthasarathy; R. J. Kerans; S. Chellapilla; A. Roy; UES INC DAYTON OH
|
| Ultra-High Temperature Ceramics (UHTC) are attractive candidates for use as leading edge components. This work explores the possibility of using computational methods to design a structure of higher strength and toughness within the constraint of 2D isotropy. The use of low-aspect ratio bone-shaped short fibers (BSSF) to improve fracture toughness and the use of composition tailoring to increase fiber strength were analyzed. Computational models show that significant improvements in fracture ... |
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| Nano-Composites: Relationships Between Nano-Structure and Mechanical Properties: Phase II |
Jan-2006 |
18 pages |
| Authors:
A J Kinloch; A C Taylor; IMPERIAL COLL LONDON (UNITED KINGDOM)
|
| This work aims to understand and model the structure/property relationships of polymer nanocomposites, based upon thermosetting epoxy polymers that are widely used as adhesives and matrices for fibre-reinforced composites. The work concentrates on investigating the mechanical and fracture properties of multiphase materials (both bulk materials and reinforced fibre-composites), and on modelling the structure/property relationships of nanocomposites. The present work shows that a substantial increase in toughness may be achieved when ... |
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| Hydrogen Environment Assisted Cracking of Ultra-High Strength AetMet(Trademark) 100 Steel |
2006 |
42 pages |
| Authors:
Yongwon Lee; Richard P. Gangloff; VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| Precipitation hardened martensitic AetMet(tradeMark) 100 is a high purity ultra-high strength steel with exceptional plain strain fractare toughness (K(sub IC) 130 MPa square root to m) and high yield strength (sigma YS 1725 MPa). The hydrogen envfronment assisted cracking (FlEAC) behavior of this modem steel is not w#1 understood, and was characterized in neutral 3.5% NaCl solution at various applied potentials (E(sub App)) relevant to coated applications in marine environments. ... |
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| Strategies for Mitigation of Hydrogen Environment Assisted Cracking of High Strength Steels |
2006 |
|
| Authors:
John R. Scully; Beth A. Kehler; Yongwon Lee; Richard P. Gangloff; NATIONAL ASSOCIATION OF CORROSION ENGINEERS HOUSTON TX
|
| Modem ultra high strength alloy steels (UHSS) have been developed with outstanding combinations of strength and fracture toughness. Such steels are characterized by high purity and nanoscale strengthening clusters/coherent precipitates in a complex precipitation hardened, martensitic microstructure. However, the performance of such steels is degraded dramatically by internal hydrogen embrittlement (IHE) and hydrogen environment embrittlement (HEE). Thus, the development of an UHSS that is immune to hydrogen embrittlement is of ... |
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| Electrochemical Mitigation of hydrogen Environment Embrittlement of Ultra-High Strength AerMet(Trademark) 100 |
2006 |
29 pages |
| Authors:
Samil Al-Ghamdi; John R. Scully; VIRGINIA UNIV CHARLOTTESVILLE OFFICE OF SPONSORED PROGRAMS
|
| The goal of this research is to extend the potential region of high toughness in an ultra-high strength steel (UHSS) to anodic and cathodic potentials where hydrogen environment embrittlement (HEE) is normally observed due to hydrogen uptake in the absence of inhibitors. This is being explored through the investigation of several selected chemical inhibitors (anodic inhibitors and cathodic blocking agents). The research is conducted in three stages. The effect of ... |
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| Microstructural Mitigation of Hydrogen Environment Embrittlement of Ultra-High Strength AerMet(Trademark) 100 |
2006 |
33 pages |
| Authors:
Yongwon Lee; Richard P. Gangloff; VIRGINIA UNIV CHARLOTTESVILLE DEPT OF MATERIALS SCIENCE AND ENGINEERING
|
| AerMet(exp TradeMark) 100, a secondary precipitation hardened martensitic steel, has excellent strength ((Sigmays = 1725 MPa) and toughness (K(sub IC) = 130 MP square root of am) when optimally tempered at 482C. However, it is susceptible to severe hydrogen environment assisted cracking (HEAC) in near-neutral 3.5% NaCl at very low threshold stress intensities (K(sub TH)) and with rapid Stage II plateau rates for subcritical crack propagation (da/dt(sub II). Interaction between ... |
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| Novel Deformation Processing of Amorphous MEMS |
26 OCT 2005 |
5 pages |
| Authors:
John J. Lewandowski; CASE WESTERN RESERVE UNIV CLEVELAND OH
|
| Novel Deformation processing of amorphous metals has been conducted on a variety of metallic glasses. Both large scale (e.g. 10's mm size) and small scale (e.g. sub-micrometer size) deformation processing has been conducted using some of the unique properties exhibited by metallic glasses. In all cases, the intermediate temperature properties of metallic glasses (e.g. Zr-, Cu-, Fe-, Al-, Hf-based) have been determined using a NIKON-QM2 Hot Microhardness Machine. Once the ... |
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| Real-Time In-situ Characterization of Electron-Beam-Induced Bulk Polymerizations |
30 SEP 2005 |
33 pages |
| Authors:
Giuseppe R. Palmese; DREXEL UNIV PHILADELPHIA PA
|
| The objective of this work was to develop a fundamental understanding of EB induced bulk polymerization of networK forming systems and to apply this understanding for the rational development of improved EB cured materials. In order to obtain a fundamental understanding of the chemical and physical processes associated with EB curing and to develop a rational means for designing improved EB material systems, our research team focused on two major ... |
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| Designed Ceramics for Aerospace Applications |
28 SEP 2005 |
7 pages |
| Authors:
I-Wei Chen; PENNSYLVANIA UNIV PHILADELPHIA DEPT OFMATERIALS SCIENCE AND ENGINEERING
|
| During this project we have optimized the performance of alpha-SiAlON with respect to the following properties: hardness, fracture toughness, room temperature strength, high temperature strength, oxidation resistance, and machinability. Strong correlations between some of these properties have been found. For example, a positive correlation between fracture toughness and room temperature strength, a positive correlation between high temperature strength and oxidation resistance, a negative correlation between hardness and machinability, and a ... |
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| The Effect of Friction Stir Processing on the Microstructure and Mechanical Properties of AF/C458 Aluminum Lithium Alloy |
SEP 2005 |
87 pages |
| Authors:
Tanya L. Giles; NAVAL POSTGRADUATE SCHOOL MONTEREY CA
|
| Aluminum-lithium alloys have been under development for lightweight-high strength aerospace structures but implementation has been slowed significantly because of poor short transverse fracture toughness and brittle intergranular delamination cracking. The alloy AF/C458 (now designated AA 2099) has been designed to exhibit decreased mechanical anisotropy and improved fracture toughness while maintaining ductility and strength levels. This thesis examines the application of Friction Stir Processing (FSP) of AF/C458 as an approach to ... |
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| Fatigue Response of Mo-Si-B Alloys |
SEP 2005 |
77 pages |
| Authors:
K. S. Kumar; BROWN UNIV PROVIDENCE RI DIV OF ENGINEERING
|
| The high-temperature compression response as well as the monotonic and cyclic crack growth behavior of a two-phase Mo-Si-B alloy compared to a TZM alloy. The compression studies confirmed that deformation in the temperature-strain rate space evaluated is matrix-dominated. In all instances evaluated, the Mo-Si-B alloys is superior to TZM. Fracture toughness of the Mo-Si-B alloy increases from ^8MPa x m at room temperature to ^25 MPa x m at l400C, ... |
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| Synthesis, Sintering and Microstructural Characterization of Nanocrystalline Hydroxyapatite Composites |
13 JUL 2005 |
|
| Authors:
B. Viswanath; N. Ravishankar; Suprabha Nayar; Arvind Sinha; INDIAN INST OF SCIENCE BANGALORE
|
| Nanocrystalline hydroxyapatite (HAp) exhibits better bioactivity and biocompatibility with enhanced mechanical properties compared to the microcrystalline counterpart. In the present work, nanocrystalline hydroxyapatite was synthesized by wet chemical method. Sintering was carried out with nanocrystalline alumina as additive, the content of alumina being varied from 10 to 30 wt% in the composite. For 20 and 30 wt % Al2O3, hydroxyapatite decomposed into tricalcium phosphate (TCP) above the sintering temperature of ... |
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| High Strength Steel Welding Research |
27 MAY 2005 |
470 pages |
| Authors:
Stephen Liu; Glen Edwards; COLORADO SCHOOL OF MINES GOLDEN CENTERFOR WELDING JOINING AND COATINGS RESEARCH
|
| The application of high strength low alloy (HSLA) steels has been limited by the availability of suitable filler metals. Specifically, as the weld metal strength increases, the susceptibility to hydrogen-assisted cracking increases. To take full advantage of the developments in HSLA steel base metals, weld filler metals which minimize the effects of diffusible hydrogen and develop tough microstructures must be designed. The benefit of yttrium-containing inclusions to provide effective hydrogen ... |
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| A Study on the Role of Grain-Boundary Engineering in Promoting High-Cycle Fatigue Resistance and Improving Reliability in Metallic Alloys for Propulsion Systems |
30 APR 2005 |
33 pages |
| Authors:
Robert O. Ritchie; Mukul Kumar; CALIFORNIA UNIV BERKELEY DEPT OF MATERIALS SCIENCE AND ENGINEERING
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| High-cycle fatigue, involving the premature initiation and/or rapid propagation of small cracks to failure due to high-frequency (vibratory) loading, remains the principal cause of failures in military gas-turbine propulsion systems. The objective of this study is to examine whether the resistance to high-cycle fatigue failures can be enhanced by grain-boundary engineering, i.e., through the modification of the spatial distribution and topology of the grain boundaries in the microstructure. While grain-boundary ... |
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| Effect of Temperature and Steam Environment on Fatigue Behavior of an Oxide-Oxide Continuous Fiber Ceramic Composite |
MAR 2005 |
107 pages |
| Authors:
Chalene A. Eber; AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING AND MANAGEMENT
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| There is an ever-increasing need for materials that maintain high strength and fracture toughness at elevated temperatures and in complex environments. Advanced aerospace applications are motivating the development of composite materials that can meet demanding requirements. This research effort investigates mechanical behavior of an oxide-oxide continuous fiber ceramic composite (CFCC) consisting of a porous alumina matrix reinforced with mullite/ alumina Nextel 720 fibers developed specifically for advanced aerospace applications. Tension-tension ... |
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| Mechanical and Thermal Properties of Advanced Ceramics for Gun Barrel Applications |
FEB 2005 |
92 pages |
| Authors:
Jeffrey J. Swab; Andrew A. Wereszczak; Jason Tice; Russ Caspe; Reuben H. Kraft; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE
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| Eight commercially available ceramic materials were procured and evaluated for potential application as gun barrel liners. These materials included an alumina, zirconia, and SiAlON, as well as three silicon carbides and two silicon nitrides. Preliminary evaluation determined the strengths, fracture toughness, Vickers hardness, thermal conductivity, specific heat, and linear coefficient of thermal expansion. An uncensored Weibull analysis was performed on all of the strength data. These databases were developed for ... |
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| Sub-Critical Telephone Cord Delamination Propagation and Adhesion Measurements |
2005 |
6 pages |
| Authors:
Alex A. Volinsky; Patrick Waters; James D. Kiely; Earl C. Johns; UNIVERSITY OF SOUTH FLORIDA TAMPA DEPT OF MECHANICAL ENGINEERING
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| Thin film delamination can occur when the stored elastic energy per unit area in the film due to the residual stress exceeds the interfacial toughness. Telephone cord morphology is commonly observed in delaminating thin films under compressive stresses. Here, the biaxial film stress is partially relieved by film buckling in the direction perpendicular to the telephone cord propagation, and by "secondary" blister buckling in the direction of telephone cord propagation, ... |
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| Multifunctional Carbon Nanotube Fiber Composites |
26 DEC 2004 |
148 pages |
| Authors:
Ray H. Baughman; Steve Collins; Gordon G. Wallace; Joseph N. Barisci; Mikhail Kozlov; Yuri Gartstein; Alan G. Rinzler; Anvar A. Zakhidov; Rishi Raj; Miklos Kertesz; Alan B. Dalton; Chee Too; TEXAS UNIV AT DALLAS RICHARDSON
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| The project provides a spinning process that results in continuous nanotube composite fibers that are about an order of magnitude tougher than any fibers made by mankind or nature. We make two hundred-meter long reels of continuous nanotube-polymer composite fiber at 70X the prior-art rate and achieve fiber strengths higher than 1.8 GPa. Our drawn nanotube fibers match the energy absorption capability of spider silk up to the breaking strain ... |
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| Effects of Porosity Distribution on the Dynamic Behavior of Two Varieties of SiC |
DEC 2004 |
52 pages |
| Authors:
Samuel R. Martin; ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS TECHNOLOGY DIRECTORATE
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| In order to understand the microstructural reasons behind variations in ballistic material properties, plate-impact tests were conducted on two sintered silicon carbides with slightly different microstructures. Regular Hexoloy (RH) and Enhanced Hexoloy (EH) were obtained from Saint-Gobain. It was determined that the porosity distribution in EH had fewer large pores leading to an 18% increase in flexural strength over that for RH. Plate-impact experiments were conducted utilizing a VISAR to ... |
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Reports by Keyword(s)
TOUGHNESS
