bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance of the Colilert Presence/Absence Test Compared to Membrane Filtration Method for Coliform Analysis of Potable Water Samples
Authors: Beebe JL , Kelley JK , Crooks RL , Cada RL
Published: March 2009

Potable water specimens, usually well water, were analyzed for total and fecal coliforms by a Standard Methods membrane filtration test (MF) and the Colilert Presence/Absence test (CPA), Access Analytical, Inc., Branford, CT. MF sample membrane filters were incubated on M-Endo agar plates at 35°C for 22 to 24 hours. Positive colonies were subcultured to Brilliant Green Bile Broth (BGB) and Lauryl Tryptose Broth (LTB) to confirm total coliforms by gas production and to EC medium (EC) incubated at 44.5°C to verify fecal coliforms. The CPA test consisted of the addition of a dehydrated powder containing salts, 4-methylumbelliferyl-B-D-glucuronide (MUG) and O-nitrophenyl-B-D-galactoside (ONPG) to 100 ml sample followed by incubation at 35°C for 24 hours, visual reading for ONPG hydrolysis (total coliforms) and under long wave UV light for MUG hydrolysis (Escherichia coli). When positive result was obtained from either system, the predominant organism was recovered and identified by the API 20E system (Analytab Products, Inc., Plainview, NY). In this study, the results of the Colilert total coliform test (ONPG hydrolysis) were compared to the total coliform results of the MF test and the E. coli (MUG hydrolysis) result by Colilert were compared to fecal coliform results by the MF test. A total of 271 paired samples were analyzed with 93.7% agreement. Two hundred and twenty samples were negative by both procedures. Thirty three samples were positive by both procedures for total coliforms (28) and fecal coliforms (5). Discordant results were obtained for 18 samples (6.7%). The MF procedure detected total coliforms, not detected by the CPA in 6 samples. CPA detected total coliforms in seven samples not detected by MF. Standard Methods membrane filter test obtained positive results for both total and fecal coliforms in three samples where CPA only detected total coliforms and was positive for one sample each for both total and fecal coliform while CPA was negative for both. CPA was positive for total and fecal coliforms for one sample in which the standard method was positive only for total coliforms.
Evaluation of a Method to Detect Giardia and Cryptosporidium in Water
Authors: LeChevallier MW , Norton WD , Lee RG
Published: March 2009

The current study outlines a technique to simultaneously detect Giardia and Cryptosporidium in raw and tap water samples. The influence of various procedural steps, including filtration, elution, flotation, filter mounting and microscopy, was determined for the method. Overall, the method recovered 48% to 69% of the Giardia and 25% to 42% of the Cryptosporidium in spiked water samples. The method had an averaged detection limit of 1 organism/100 L of tap water. Use of phase-contrast and Nomarski differential interference contrast microscopy could detect false-positive algal cells and determine cysts and oocysts having “non-viable type” morphologies.
A Comparison of Indirect Fluorescence, Modified Reference(Non-Acidified), and Modified Reference(Acidified) Techniques for Giardia Detection in Northeastern Waters
Authors: McFarlane SA , Roberts GB
Published: March 2009

Pennsylvania Gas & Water Company's Water Quality Laboratory has continuously monitored the company's watersheds since an outbreak of giardiasis in December, 1983. Twenty-five reservoirs are sampled monthly; approximately 3100 filters to date. Two techniques are employed; the reference method and an immunofluorescence technique (IFT). The reference method has been modified to obtain higher percent recoveries for routine monitoring. Samples were obtained from watersheds known to be positive and analyzed by IFT, Modified Reference (MR-N), and Modified Reference (MR-A, Final pH <2.0). Variations and drawbacks for each technique will be discussed, as well as statistical analyses. Thirtyone samples were analyzed and the greatest number of cysts were detected with IFT. The MR-A technique yielded the highest percentage of positive samples. Northeastern waters have excessive organic debris present which effects all three methods. However, the MR-A proved to be the method least affected by turbidity. Although recovery when monitoring the environment cannot be measured accurately, the MR-A seems to be the more efficient method for routine monitoring of Giardia cysts in northeastern waters.
Statistical Design and Analysis of Assays for Monitoring Waterborne Viruses
Authors: Wymer LJ
Published: March 2009

An assumption often made in assaying for plaqueforming viruses is that the formation of plaques among several cell culture bottles will follow a Poisson distribution. Examining the results of several virus assays using Fisher's index of dispersion, the assumption of a Poisson distribution was found to be warranted in most cases, but not always. The distribution of plaque counts will affect the statistical evaluation of such data; confidence limits for virus titer based on Poisson statistics will be appropriate in many instances. For purposes of sample design, an approach based on the Poisson assumption is recommended.
Suggested Microbiological Water Quality Tests for Developing Countries and Rural and Isolated North American Communities
Authors: Dutka BJ
Published: March 2009

In developing countries and in the rural and northern parts of North America, the delivery of potable water which is safe, adequate and accessible to all is not an easy task. Limited resources must be directed toward achieving an optimum balance between these needs. An important consideration in the development and maintenance of safe water supplies is the use of appropriate monitoring technology for assessing microbiological water quality. Presently used microbiological water quality tests have several disadvantages for routine monitoring programs in developing countries and rural isolated communities in North America. Firstly, they are not easily portable for use in isolated areas. They require trained technicians, sophisticated laboratory equipment and expensive supplies, most of which are not readily available in developing countries.

To overcome these problems, simplified reliable microbiological water quality tests are required. Testing procedures which fulfill the above requirements would make it possible for countries and isolated communities to monitor and classify their raw water supplies, potable waters and recreational waters with a minimum of input in terms of resources and expertise.
Flexibility of the Human Knee as a Result of Varus/Valgus and Axial Moments in Vivo: Apparatus Design and Performance Evaluation
Authors: Mills OS , Hull ML
Published: March 2009

The contributions of this paper are twofold. One is the design and performance evaluation of new equipment to determine the rotational flexibility of the human knee in vivo. Because determining knee flexibility requires the application of external loads and the measurement of knee rotations, the new equipment consists of a load application stand and a triaxial goniometer. The triaxial goniometer noninvasively mounts to the leg and directly measures the relative three-degree-of-freedom rotations of the knee. The goniometer incorporates several unique design features that enhance measurement accuracy. The load stand applies pure varus/valgus and external/internal axial moments either individually or in combination through the use of motors controlled by the test subject. Unique to this design are features that enable the application of moments to the knee to minimize shear forces. Other unique design features permit the stand to control hip and knee flexion angles, muscle contraction, and axial loading. To assess the accuracy with which rotations are measured during experiments, three tests were conducted with the equipment. One test evaluated the inherent accuracy of the goniometer, a second test assessed the potential for goniometer slippage during loading, and a third test explored the effect of goniometer mounting on the repeatability of results. A special verification apparatus facilitated evaluation of goniometer inherent accuracy.

A second contribution of the paper is an investigation of the effect of foot constraints (that is, boundary conditions) on flexibility results. To make this investigation, three subjects were tested with the knee at 15° flexion. Results revealed large differences in flexibility between constraining the foot in both external/internal and varus/valgus rotations and permitting the foot to rotate freely in the direction not being loaded. Further, constraint moments as high as 23 Nm were also recorded. These results emphasize that to obtain accurate flexibility results for isolated loads, the foot must be unconstrained by the loading apparatus.
Design and Performance Evaluation of an Automated System to Determine Knee Flexibility in Vitro
Authors: Berns GS , Hull ML , Patterson HA
Published: March 2009

An automated system was designed to study the complete flexibility functions of the knee in vitro. The system allows five degrees of freedom with flexion angle being fixed, although adjustable from 0 to 45°. Loads corresponding to each of the five motions can be applied independently and in any combination. The effect of weight bearing on knee flexibility can also be studied by including axial force as one of the five loads. The relative motions are accurately measured with linear and rotary variable differential transformers (LVDTs and RVDTs), and the loads are measured with strain gage transducers. The system is digitally controlled with a closed feedback loop, allowing for any combination of programmed loads. A control algorithm on an IBM PC/AT monitors the loads on each axis and continuously adjusts stepping motors to follow programmed loads correctly. The machine coordinate system corresponds to clinically accepted definitions of motion yet retains sequence independence for rotations. Results demonstrate the repeatability of using a functional definition of axis placement to align the leg within the machine and the utility of the full flexibility functions of the knee, notably in the determination of significant load interactions and coupled motions.
Optimal Design of an Uncoupled Six-Degree-of-Freedom Dynamometer
Authors: Quinn TP , Mote CD
Published: March 2009

A design analysis of a class of six-degree-of-freedom strain-gage dynamometers that are virtually uncoupled in each force and moment component is presented. The method of design is detailed, and an optimal design algorithm is implemented. The dynamometer is made of six or more T-sections with thin webs and flanges called shear panel elements (SPE). Complete stress and buckling analyses are carried out for the SPE, and experiments confirm the predictions of the analyses. The optimal design method is illustrated with several case studies. A dynamometer has been built and used in laboratory and field experiments.
Nationwide Registration of Ski Injuries in Sweden
Authors: Sandegård J , Eriksson B , Lundkvist S
Published: March 2009

The founding of a nationwide organization of ski areas in Sweden enabled annual collection of data from first aid services about skiing injuries and medical emergencies. The results show that, during the study period (1981 to 1988), the distribution of injuries changed very little.

Wearing a helmet has become more popular. The percentage of head injuries among those injured skiers wearing a helmet is half the percentage of head injuries among those skiing without a helmet. This may be because a helmet has a true head-protecting function, although other factors such as changing the way of falling or skiing should be considered.

Lack of background statistics makes the comparison of relative figures for various injuries presented in our investigation difficult.
Dynamic Displacement and Pressure Distribution in Alpine Ski Boots
Authors: Hall BL , Schaff PS , Nelson RC
Published: March 2009

The motion of the lower leg and the pressure at the interface between boot and lower leg were analyzed in both skiers and nonskiers to better understand current requirements of alpine ski boots for varying levels of skiing experience. Sixteen subjects, eight skiers and eight nonskiers, were tested. Five boots, including traditional, rear entry, and mid-entry designs, were studied. In each of the pairs of boots, subjects performed a series of rapid downward movements (“unweighting”) on skis that were rigidly attached to a platform. Pressure data were collected using a capacitance measuring mat with six measuring points located 4 through 17 cm above the ankle along the anterior surface of the right lower leg; displacement of the leg and boot was determined from two-dimensional video analysis. Results indicate that the pressure generated on the lower leg by experienced skiers was larger than pressure generated by nonskiers. The range of motion (flexion) of the boots was also greater for the skiers. The ratio of pressure to angular displacement was consistent across groups within each boot, indicating that flexion characteristics are governed by material properties of the individual boots. This pressure-to-displacement ratio did vary among boot designs. With this in mind, it is recommended that, to achieve the range of motion necessary for proper performance of an alpine ski boot, beginning skiers should use a boot with a greater angular deflection for a given applied pressure. Information of this nature could be included in commercial specifications.
Designing Effective Health Education for Downhill Skiers: Results of a Randomized Intervention Study
Authors: Damoiseaux VMG , de Jongh AML , Bouter LM , Hospers HJ
Published: March 2009

This article presents the results of a randomized intervention study among Dutch downhill skiers of 18 years and older. The objective of the study was to find an effective method to convince skiers that they have to adjust their ski bindings adequately. Literature study revealed that adequate adjustment of bindings (that is, by an expert and by means of a test device) is the most important behavior that can be manipulated to decrease the occurrence of ski injuries.

Three conditions were varied: when (the “moment”) information materials were sent to skiers (one week versus three weeks before departure on a ski vacation), the medium (cassette versus leaflet), and the approach (fear-arousing versus neutral information). In this way, eight experimental groups were composed. In addition, a control group was formed that did not receive any information. The effects of the three conditions on the following factors were measured: attention, comprehension, intention, and behavior.

The cassette received a higher degree of attention than the leaflet, irrespective of time or degree of fear. The level of comprehension was higher in all experimental groups than in the control group. The information sent long before departure and with a high degree of fear produced the most effect on the level of comprehension. As for the factors intention and behavior, no differences were found between the experimental groups and the control group. Differences in intention and behavior did appear among the distinctive experimental groups. The information sent shortly before departure as well as the information with a low degree of fear proved to have the least effect on intention. Behavior was most affected by information with a high degree of fear, irrespective of time and medium.
Planning Health Education for Downhill Skiers
Authors: Bouter LM , Kok GJ
Published: March 2009

The planning of health education to prevent ski injuries is often incomplete and not stated explicitly, while the evaluation of health education is executed only partially or not at all. This article presents a theoretical framework for planning and evaluating health education for downhill skiers. Systematic planning consists of an analysis of the magnitude of the problem, an analysis of the behavioral risk factors, a study of the determinants of the behavior at issue, the design of an optimal intervention, and the implementation of this intervention. The evaluation phase deals with the effects of the planning on these five levels (implementation, intervention, determinants, behavior, and injury risk). Some common pitfalls are mentioned, and special attention is given to the study of determinants of behavior and to the design of the intervention. Furthermore, the importance of pretesting health education material is underlined. There seems to be a strong need for further research on the etiology of ski injury and its determinants of behavior before prevention can be realized.
Tribological Models for Solid/Solid Contact: Missing Links
Authors: Rice SL , Moslehy FA
Published: March 2009

This paper presents a brief overview of the tribological information which mechanical designers need, such as equations to predict frictional forces and wear rates. This is contrasted with the forms of result that typify wear testing in research, for example, comparative rates which are meaningful only for the apparatus used. And while the “systems nature” of tribology is well known by researchers, there is a natural tendency to overlook at least some complexities as attempts are made to isolate particular contact phenomena. Thus, both designers and researchers seek simplicity in problems which are inherently complex.

This complexity is manageable, provided one is willing to deal with complete specification of the system. This paper addresses that issue, and suggests a representation for a tribosystem which incorporates features that require attention from both mechanical modelers and materials scientists. Specifically, there is a need for characterization of the dynamic behavior of tribosystems — including both specimen and counterface “sides,” of the apparatus — together with solution of the tribological problem set. That is, once time varying dynamic loads and motions are known, then the study of actual contact areas and force transmission to and through asperities can begin. Additionally, when the associated heat transfer problem is solved, it becomes possible to study the material response of specimen and counterface in terms of fundamental processes such as diffusion, adhesion, bond formation and rupture, and plastic strain accumulation in the substrate.

A general tribosystem representation is suggested to underscore a sequence of mechanical problems which must be addressed in parallel with fundamental materials-related problems. Only when both sets are treated can the resulting systems' behavior be modeled from first principles. Thus, the new representation serves to highlight what is missing in tribological models for solid/solid contact.
Cultural Impediments to Practical Modeling of Wear Rates
Authors: Ludema KC
Published: March 2009

A perspective is given on some of the difficulties in developing of practical equations for use by designers in predicting the wear life of mechanical components. Several reasons are given, beginning with the presence of authors and researchers in the field who are from very different educational backgrounds from each other. Secondly, authors write from very different perspectives ranging from the strictly empirical to the scientific. Thirdly, there has not been a very broad effort to determine which of the material properties usually found in wear equations are intrinsic, relevent or unique. The best approach to wear modeling is to develop an organized way to accumulate empirical results from tests that simulate practical systems and build models from these data.
Development and Coordination of Materials Data Banks in France
Authors: Marx B
Published: March 2009

A survey was done in 1988 by CODATA FRANCE and the Ministry of Education on Materials Data Banks Production in France. Forty data banks were analyzed in relation to producers, subject coverage, type of data, mode of access, and method of use.

Given the major effort required to build a data bank, a large number of these data banks are the result of national or international cooperation. An analysis of the fields covered shows the importance of metals, polymers, and building materials. The properties covered are mechanical properties and a description of the materials. This information is expressed in terms of textual-numerical data and inventories.

Calculation software provides an important plus for the use of numerical data. Two thirds of data banks are accessible from a distance, and access by videotex is common. The various types of materials data banks belong to two main categories: 1. Scientific data produced by higher education covering fundamental properties expressed in the form of numerical data, associated with calculation programs, and accessible locally or at a distance in ASCII mode. 2. Technological data produced by other public sector bodies, nonprofit making organizations, and industrial companies. These data describe the characteristics of the materials and their mechanical properties in the form of textual-numerical data and inventories. They are often accessed at a distance and by minitel.

The results of this study are being analyzed by different ministries involved in Materials Data Banks production, for example, Education nationale, Recherche et Technologie, Industrie. Proposals are being discussed for an easier access and search method adapted to end users in different activity sectors.
Cooperation—A Good Chance for Industry in Setting Up Materials Data Banks
Authors: Brandstätter A
Published: March 2009

The situation in the field of materials data banks in the Federal Republic of Germany is described in this paper.

An analysis of early data banks resulted in the following conclusions: (1) it is not helpful to build an overall materials data bank with a lot of data gaps, (2) there was no information on the quality and reliability of the data, (3) the results of searching the data were often less effective than thumbing through the pages of a book, (4) there was no user friendliness within the retrieval systems, and (5) the data banks were very different from each other and the users had to learn several systems.

On the basis of these results, new concepts of materials data banks were developed that included two groups of activities: 1. building a framework with (a) setting up an overall conceptual scheme, (b) user friendly access, (c) programs for data calculation and interpretation, and (d) building up expert systems; and 2. collecting, validating, and evaluating data on the basis of the framework and special agreed rules for (a) collecting and validating data in an agreed structured format, (b) collecting data with high quality and complete information, (c) measuring of missing data, (d) working out algorithms for calculating and extrapolating data, and (e) building data banks out of data produced by several institutions.

Carrying out all of these activities is a tremendous job that can be done only with the cooperation of all the data producers.
Increasing Data System Responsiveness to End-User Expectations
Authors: Kaufman JG
Published: March 2009

Responsiveness to user expectations on ease of use, content, and style of presentation are paramount in gaining engineers' and materials scientists' acceptance and utilization of computerized numeric/factual databases and information networks. In this paper, the factors that influence both users' comfort and efficiency with such electronic data sources, whether single databases, clusters of databases, or networks of data from a variety of sources will be discussed.

Among the key subjects that will be covered are: 1. User-oriented interface. 2. Interactive thesaurus. 3. Options in search strategies. 4. Logical displays of data.

In addition, for online networks in particular, there are additional requirements that will be also discussed: 1. Compatibility with personal computer, compact disk, and other mainframe applications. 2. Diversity of database management systems. 3. Graphics; interactions with numeric databases.

In addressing these issues, the experience gained in building both the Pilot National Materials Property Data (MPD) Network, operating online from Stanford University, and in developing the production version of the MPD Network on STN International is called upon in this paper. Through the iterative process of gaining user feedback from trials of the developmental system, much has been learned and, to the degree practical, used in establishing the MPD Network system.

As the capability and ease of use of commercially available computerized materials data sources increase, we can expect to see a substantial increase in the utilization of such sources by the end users of the information for which searches are being carried out.
Data Sources of Mechanical and Physical Properties of Engineering Materials
Authors: Wawrousek H , Westbrook JH , Grattidge W
Published: March 2009

An indexed catalog of sources of compiled data on 23 classes of properties of 50 classes of materials has been prepared: (1) as a guide to a source of particular data needed in current technical work; (2) for identification of needs and opportunities for new and updated data compilations; (3) as a review and comparison of data sources of similar scope; and (4) as auxiliary files for user guidance on networks of computerized databases. Over 1200 citations are listed and indexed in the following categories: Computer-Readable Databases; Data Centers and Projects; General Handbooks; Nonnumeric Sources (graphs and images); Printed Articles and Compilations; and Subset Volumes within a Handbook Series. Each citation has been coded for the material(s) and properties covered within the entry. Several opportunities are outlined for extending the coverage of the compilation, enhancing the entry descriptors, and providing alternative delivery modes.
Computerization of Composite Materials Data and Metadata
Authors: Stanton EL , Meyer KJ , Kipp TE
Published: March 2009

The ASTM identifies three material classes; metals, ceramics, and polymers, and the three associated composite material classes for purposes of computerizing materials information. The present paper is focused on polymer-matrix composites and in particular those using graphite, aramid, and glass fibers in both thermoset and thermoplastic matrix materials. A first generation advanced materials database system (AMDBS) was recently completed for the collection and exchange of composite material properties data. Information is separated into test, design, and analysis categories with all data types stored as relational databases. A data structure similar to the four level data file structure for high temperature materials described by Kröckel and Westbrook was used for metadata. This provides traceability and factual information about the specimens and test conditions used to obtain a particular property. Property relations in AMDBS can be either tables or graphs. The principal operational difference between AMDBS and a system of stored optical image lies in its ability to answer structured questions about the materials in the database with specific properties under specific conditions. The user can then compose an engineering graphic from the results of a query or from graphical relations in the database. To allow finite element analysts electronic access to properties from MIL-HDBK databases, properties can be exported to PATRAN and IGES files. This provides a paperless transfer of properties information from archive sources like MIL-HDBK 17 and from evaluated composite test laboratory reports to finite element analysis applications codes. The utility of existing technical data exchange standards like MIL-STD 1840A is discussed based on experiences from the AMDBS project.
A Numeric Database for Tribology: Format and Application Issues
Authors: Ruff AW , Rumble J , Jahanmir S
Published: March 2009

A computerized tribology information system designed for use with personal computers and including a numeric database is presently under development. The status of this system (named ACTIS) is summarized. Two important issues associated with the numeric database component were the data format and the organization of numeric data for user applications. Based on information developed at a National Institute of Standards and Technology (NIST) workshop on tribology information, a set of data fields has been identified for use in a database on friction and wear of materials, and on material properties. Evaluated data in these categories have been assembled and loaded into that format using commercial database management software. Over 360 records are presently contained in the database covering a broad range of materials of tribological significance. The data are organized for direct application by the user in material selection, wear model calculations, tribological component design, and with other software codes such as stress and temperature calculations.
HIGHTEMP—A Database for Mechanical Properties at Elevated Temperatures
Authors: Sandström R , Ivarsson B , Lindblom J
Published: March 2009

A database for elevated-temperature tensile and creep properties for steels called HIGHTEMP has been developed. Materials that are included in the database are unalloyed, low alloyed, 12% chromium, and austenitic stainless steels, mainly of pressure vessel type. The data have been collected previously from Swedish industry and laboratories. Full metallurgical background information can be found in the system. This includes metallurgical casting and working processes, as well as product form, specimen geometry, heat treatment, room temperature tensile properties, microstructure, and testing methods.

To illustrate the use of the database, the correlation between room-temperature tensile properties and creep properties have been studied for a few stainless steels. For 15Cr-15Ni-1Mo and 17Cr-12Ni-2Mo-0.15N, the creep rupture strength increases significantly with increasing room-temperature strength at testing temperatures below 750°C. In the same way, the creep ductility was reduced when the room-temperature strength was high. For 15Cr-15Ni-lMo, the variation in the room temperature tensile strength was related to a variation in the grain size.
A Computerized Database on Coatings and High Temperature Corrosion
Authors: Streiff R
Published: March 2009

A survey of currently available high temperature coatings clearly demonstrates that selection of the appropriate coating for a specific application is becoming a challenging task, and that it is necessary to have easy access to detailed information on the various types, the various deposition methods, the protection characteristics, and the applicability of the coatings. The COATINGS & HIGH TEMPERATURE CORROSION DATA BANK will collect in computerized forms, background information on available coatings and high temperature corrosion resistance of coatings, and on industry experience with coatings and coating technology for high temperature applications. The objective of the data bank is to provide data/information to coating users by an online access through an international data network.
Diagnosing Window and Curtain Wall Leaks
Authors: Kudder RJ , Lies KM
Published: March 2009

Determining the cause or causes of leaks, isolating the problem components and details, and verifying the efficacy of remedial measures, requires systematic diagnostic procedures. Documentation of the damage, evaluation of project documents, determination of as-built conditions, and testing, are necessary steps in a comprehensive program. Discussed are the evaluation and testing procedures, masking techniques, disassembly and inspection procedures, etc., which have proven useful as part of solving leakage problems. Particular emphasis is placed on testing procedures which are adaptable to use on-site.
The Practical Use and Potential Limitations of Exterior Insulation and Finish System Materials as an Exterior Building Envelope
Authors: French WR
Published: March 2009

The increased utilization of Exterior Insulation and Finish Systems (EIFS) as the primary component of exterior building envelopes for projects ranging in size from small commercial buildings to major high-rise structures has continued unabated for several years now. As new market regions within the United States and the installation work force in these areas are introduced to the use of this building material, there is a natural “learning curve” pertaining to its proper use, limitations, and potential disadvantages. Architects, designers, project supervisors, and local craftsmen are required to acquire a fundamental knowledge of the correct use of EIFS in order to avoid potential problems. This paper presents some of the practical problems being experienced today in regard to this new technology. Although it does not present a specific case study, this paper draws from the experiences of investigation and analysis on dozens of different projects nation wide, some of which were experiencing severe problems related to moisture infiltration. It discusses common mistakes and typical abuses observed in a large percentage of the projects reviewed. In addition, an attempt is made to address correct usage of this increasingly important material by applying well established principles of basic building technology. This paper is intended to assist in achieving the best performance and service life available from this particular building material by disseminating knowledge gleaned from experience with past problems in existing buildings.
Methods for Identifying Sources of Moisture in Walls
Authors: Trechsel HR
Published: March 2009

The first issue in investigating moisture problems is the source of the moisture. Sometimes, visual inspection can determine whether liquid water or vapor is involved, active mechanisms, and season when problem occurs. Frequently, however, the issue is not so clear, and diagnostic tools must be used to establish the source and transportation mechanisms. This paper identifies some diagnostic tools and techniques which have been used successfully to determine moisture sources and transport mechanisms. It also discusses the locations, frequency, and duration of tests required. Examples of the application of the techniques are provided to demonstrate the application of the tools. Opportunities for innovative diagnostic technologies will be discussed, as well as the need for standard protocols for evaluating moisture problems for comparing results and to allow the establishment of a data bank as a basis for developing future guidelines for preventing moisture problems in buildings.
Establishing Appropriate Field Test Pressures for Investigation of Leakage Through the Building Envelope
Authors: Cole GG , Schwartz TA
Published: March 2009

Most performance standards for building envelope components, such as those for certified windows, have been developed for evaluating new products or for helping assure the quality of mass produced products. There are, however, few standard procedures for evaluating performance problems with installed wall systems. Many investigators have attempted to apply performance standards for new assemblies to problematic buildings; and this often leads to the wrong conclusion regarding the cause of building leakage.

This research explores the appropriate use of water test procedures for field investigation of leakage through building walls. We explore both the type of testing and appropriate criteria for judging the contribution to leakage from various components of the exterior envelope. We also discuss a methodology for developing test parameters based on actual weather records and surrounding topography. These exposure conditions can be used to formulate test pressures that can be applied to elements of the building envelope during water testing to more closely simulate the past exposure conditions that these wall components experienced during leakage events.
Tracing Roof and Wall Leaks Using Alternating Electric Fields and Vapor Detection
Authors: May JC , Vassiliades JM
Published: March 2009

Exterior water can penetrate a building and move in either continuous or discontinuous flow. In the case of continuous flow, from point of entry to point of observation, surfaces of construction materials are wetted and may provide a path of adequate conductivity to produce a detectable alternating electric field when a voltage is applied. Where this is the case, a suitable a-c ource and detector can be used to determine the source of water entry.

For cases where water flow is discontinuous, detection of vapor from water mixed with organic solvent can assist in tracing water movement and source of origin. Commercial equipment is available to measure, non-destructively, moisture behind and within non-conducting substrates such as wood and exterior foam panels. Using these methods one can often unambiguously locate the source of a water leak.
Cooling Rate Effects in Carbon Fiber/PEEK Composites
Authors: Davies P , Cantwell WJ , Jar P-Y , Richard H , Neville DJ , Kausch H-H
Published: March 2009

This paper examines the influence of cooling rate after molding on short- and long-term properties of continuous carbon fiber reinforced polyetheretherketone (PEEK). First, changes to matrix structure and internal stress levels resulting from cooling panels at different rates are described for composites of PEEK with AS4 and IM6 fibers. The effects of these changes on short-term properties are illustrated by tension, compression, delamination resistance, and drop weight impact tests and results are compared with published data. Long-term properties are then discussed and results from creep loading, tension-tension fatigue, and Mode I delamination fatigue are presented. Both short- and long-term results indicate that the internal stresses induced during fast cooling are more detrimental to the performance of IM6 carbon fiber/PEEK composites than the changes in matrix structure observed at slow cooling rates.
Effects of Moisture Absorption on Edge Delamination, Part II: An Experimental Study of Jet Fuel Absorption on Graphite-Epoxy
Authors: Hooper SJ , Subramanian R , Toubia RF
Published: March 2009

An experimental study was conducted to investigate the environmental effects of jet fuel absorption on the mixed-mode fracture toughness Gc of AS4/3501-6 graphite-epoxy. Edge delamination tension tests of saturated and partially saturated (30/-302/30/90n)s (n = 1, n = 2), (35/-35/0/90)s and (35/0/-35/90)s layups were conducted. Three types of jet fuels were considered including JP-4 military jet fuel, Jet-A commercial jet fuel, and Type VII rubber swelling test fluid. Additional tests were conducted at the room temperature dry (RTD) and water soaked conditions. The water soaked specimens were also tested in the saturated and partially saturated conditions.

The total and the mixed-mode strain energy release rates were evaluated using a modified quasi-three-dimensional finite element (Q3DG) analysis. Edge delamination data of partially saturated and saturated specimens was used to quantify the relative influence of typical aircraft fluids on interlaminar fracture for composite materials. The effects of hygroscopic strain gradients on the interlaminar fracture toughness was investigated for the fluids considered.
Effect of Porosity on Flange-Web Corner Strength
Authors: Kan H-P , Bhatia NM , Mahler MA
Published: March 2009

A strength of materials based model was developed to determine the interlaminar tensile stress at the corner radii of curved composite structures. The model assumes that the stress state in the local area near the corner is under pure bending. The force in each layer (ply) of the laminate is determined by classical lamination theory and the curved beam analysis method. The interlaminar tensile stress is then obtained by enforcing the force and moment equilibrium in each layer.

To verify the accuracy of this analytical model, a series of corner specimens were fabricated and tested. These specimens were fabricated under controlled conditions and no porosity was detected in the specimens. The corner specimens were tested by pulling apart the sides of the corner to introduce bending moment at the corner. The maximum interlaminar tensile stress computed using the analysis model was compared to the flatwise tensile strength of the material in order to predict the failure moment of the test specimen. Excellent correlations between the measured and predicted failure moment were achieved.

A series of tests were conducted on flange-web corner elements obtained from graphite composite frames that had porosity in their corners. The objectives of these tests were to determine: (1) level of porosity in the corners by using ultrasonic inspections and photomicrographic examinations, and (2) the effect of porosity in the corner on the bending strength and the interlaminar tensile strength. Ultrasonic inspections revealed the locations along the corners where porosity was present. Photomicrographic examinations showed that the porosity occurred in clusters between plies and appeared similar to delaminations. Qualitative levels of porosity, based on photomicrographic observations, were established; these were (1) no porosity, (2) low porosity, and (3) high porosity. Attempts to use acid digestion methods to establish quantitative measures of porosity were not successful because the porosity was localized between only a few plies.

A relationship was established between ultrasonic signal attenuation loss due to porosity and interlaminar tensile strength of porous structures. Strength testing was conducted on the flange-web corner specimens. Post-failure examination of the test specimens showed that interlaminar tension dominated the failure with little evidence of shearing effects. The failure strength data were used with the analytical model to calculate the interlaminar tensile failure stress for each specimen.
Fracture Analysis of Transverse Crack-Tip and Free-Edge Delamination in Laminated Composites
Authors: Armanios EA , Sriram P , Badir AM
Published: March 2009

Delamination is a predominant failure mode in continuous fiber-reinforced laminated composite structures. Based on the location and direction of growth, there are two distinct types of delamination, namely, free edge delamination and local or transverse crack tip delamination. In many cases, both types occur concurrently with varying levels of interaction. In this paper, a shear deformation model including hygrothermal effects is developed for the analysis of local delaminations originating from transverse cracks in 90° plies located in and around the laminate midplane. A sublaminate approach is used and the model is applied to (±25/90n)s T300/934 graphite/epoxy laminates for n values between 0.5 and 8, along with previously developed edge delamination shear deformation models. Critical loads and delamination modes are identified and compared with experimental results. Hygrothermal effects are included in all the models to make the comparisons realistic.
Fatigue Delamination Onset Prediction in Unidirectional Tapered Laminates
Authors: Murri GB , Salpekar SA , O'Brien TK
Published: March 2009

Tapered [0°] laminates of S2/CE9000 and S2/SP250 glass/epoxies, and two different specimen types of IM6/1827I, a graphite/epoxy with a toughened interleaf, were tested. Specimens were subjected to cyclic tension in a hydraulic load frame. The specimens usually showed some initial stable delaminations in the tapered region, but these did not affect the stiffness of the specimens, and loading was continued until the specimens either delaminated unstably, or reached 106 to 2 × 107 cycles with no unstable delamination. The final unstable delamination originated at the junction of the thin and tapered regions, and extended into both the tapered and thin regions.

A finite element (FE) model was developed for the tapered laminate, both for the laminate with no initial delamination, and for the tapered laminate with the initial stable delaminations observed in the tests. The analysis showed that for both cases the most likely place for an opening (Mode I) delamination to originate is at the junction of the tapered and thin regions. For each material type, the models were used to calculate the strain energy release rate, G, associated with delaminations originating at that junction and growing either into the thin region between the belt and core plies, or into the tapered region, between the belt and dropped plies. For delamination growth in either direction, calculated values of G reached a peak at a delamination length equal to few ply thicknesses, and then decreased. The highest values of G were calculated for the laminate with an initial stable delamination in the tapered region and an opening mode delamination growing from the junction into the tapered region.

For the materials tested, cyclic GImax values from double cantilever beam (DCB) tests were used with the maximum G values calculated from the FE analysis for delamination growth in the tapered and thin regions, to predict the onset of unstable delamination at the junction as a function of fatigue cycles. The predictions were compared to experimental values of maximum cyclic load as a function of cycles to unstable delamination from fatigue tests in tapered laminates. The predictions, assuming delamination initiated in the tapered region, agreed reasonably well with the test data, although the correlation was slightly conservative for all except the S2/SP250 material. The measured and calculated results, assuming delamination initiated in the thin region, showed good agreement, although the predictions were slightly unconservative for the S2/SP250 laminates
Effects of Stacking Sequence on Impact Damage Resistance and Residual Strength for Quasi-Isotropic Laminates
Authors: Dost EF , Ilcewicz LB , Avery WB , Coxon BR
Published: March 2009

Residual strength of an impacted composite laminate is dependent on details of the damage state. Stacking sequence was varied to judge its effect on damage caused by low-velocity impact. This was done for quasi-isotropic layups of a toughened composite material. Experimental observations on changes in the impact damage state and post-impact compressive performance were presented for seven different laminate stacking sequences. The applicability and limitations of analysis compared to experimental results were also discussed.

Post-impact compressive behavior was found to be a strong function of the laminate stacking sequence. This relationship was found to depend on thickness, stacking sequence, size, and location of sublaminates that comprise the impact damage state. The post-impact strength for specimens with a relatively symmetric distribution of damage through the laminate thickness was accurately predicted by models that accounted for sublaminate stability and in-plane stress redistribution. An asymmetric distribution of damage in some laminate stacking sequences tended to alter specimen stability. Geometrically nonlinear finite element analysis was used to predict this behavior.