bluuebunny/crossref_metadata_2025 huggingface dataset:
Developing Residential Design Statements for the Hearing-Impaired Elderly
Authors: Abend Allen , Chen Alexander
Published: March 2007

Hearing impairments are the third most prevalent chronic condition facing individuals 65 years and older. Sociodemographic trends suggest a further growth in magnitude and incidence of this handicap. Current residential design principles for the hearing-impaired elderly are limited and do not adequately reflect the complex nature of the problem. Researchers have noted that rules or statements that can compensate are not well specified. This article presents a systematic procedure for developing design statements appropriate to the needs of the hearing-impaired elderly. In contrast to traditional approaches, the procedure emphasizes a systematic review of the medical literature on the auditory capabilities of the older individual. Intermediate environmental concepts are developed from this review and provide a basis for a set of performance-based design statements for the hearing-impaired elderly. These statements are compared with standards currently being promulgated by the American National Standards Institute.
Sequential Spatial Choices in the Large-Scale Environment
Authors: Saisa Jouko , Garling Tommy
Published: March 2007

Sequential spatial choices of shopping destinations in the largescale environment, entailed by multistop trip planning, have been modeled as a sequence of choices of closest locations. The validity of such modeling attempts was questioned by the results of a reported study. In a laboratory test, subjects who solved simulated trip-planning problems with one, two, or three choice sets with pairs of familiar locations were found frequently to choose in a way that total distance was minimized even though this meant that the closest location was not chosen each time. The results were similar in a field test in which subjects were taken to a downtown business district, asked to choose locations, and to walk to the chosen locations. Subjects were furthermore found to make few revisions when implementing their choices. The ability to minimize total distance probably relied on the discovery of spatial configurations of locations that appeared to presuppose a simultaneous representation of the locations, as suggested by differences in results in both the laboratory and the field tests depending on whether subjects had access to a street map or not, in the laboratory test depending on whether the locations were downtown or all over the city.
Components of Neighborhood Satisfaction
Authors: Cook Christine C.
Published: March 2007

Recent attention to the increased numbers of poor single-parent families has raised questions about the neighborhood environments in which they and their children are living. This article reports the findings of an investigation on the neighborhood satisfaction among two groups of low-income, single-parent women currently participating in the Section 8 rental subsidy program, those living in urban and those living in suburban neighborhoods. The results suggest that suburban respondents are significantly more satisfied with their neighborhoods than their urban counterparts. Important similarities and differences in the components of satisfaction among the two groups of respondents are indicated. While neighborhood safety for themselves and their children is critical to the neighborhood satisfaction of both groups, housing and location characteristics and residential attachment are more important to suburban than urban respondents. Background characteristics and perceived housing opportunities and anticipated discrimination play a role in the neighborhood satisfaction of urban respondents.
The Psychological Utility of Visual Penetration in near-view Forest Scenic-Beauty Models
Authors: Ruddell Edward J. , Gramann James H. , Rudis Victor A. , Westphal Joanne M.
Published: March 2007

Empirical studies of the perceived scenic beauty of forest settings have followed either the psychophysical or psychological traditions of environmental-perception research. Although psychophysical models of forest scenic beauty have proven useful to resource managers, they tend to lack theoretical content. On the other hand, psychological research often fails to produce results directly applicable to landscape management. This paper reports on an analysis combining the strong points of both the psychophysical and psychological approaches to environmental-preference research. Psychological theories of aesthetic response are used to deduce a variable, visual penetration, which is evaluated in psychophysical models of forest scenic beauty. Visual penetration is shown not only to be a significant positive contributor to explained variance, but also to be more important in accounting for scenic beauty evaluations than measures more typical of psychophysical models.
The Traveller
Authors: Leiser David , Zilbershatz Avishai
Published: March 2007

A detailed computational model for learning spatial networks is presented. Information is kept in a distributed, modular format: "condition-actions pairs." Knowledge of individual routes consists in chaining this piecemeal information. The model, called the Traveller, was fully implemented, and some sample runs are discussed. In learning a new network, the model displays the well-known transition from route level to survey level knowledge. No special mechanisms are needed to achieve the transition, as the Traveller's interactions with the environment gradually structure its emerging cognitive map. The Traveller is compared with some of the main competing computational models, and evidence from empirical research is adduced to support the suggested representational format.
The Role of Expectations in the "Intention to Move" Among Single-Parent Families
Authors: Cook Christine C.
Published: March 2007

The purpose of this investigation was to extend previous research on residential mobility by examining the role of constraints in the "intention to move" among single-parent women. Two indices are introduced to examine claims that expectations-housing market expectations or anticipated discrimination and personal expectations for the future-impact on housing satisfaction and mobility decisions. In this study, race, children's ages, worry about expenses, tenure status, housing market expectations, and residential satisfaction are found to impact on the intention to move of single-parent respondents. However, several traditionally useful variables-respondent's age, education, employment status, and income-are not significant predictors. In addition, length of time at current address, travel time to work, structure type, number of bedrooms, and personal expectations for the future are also insignificant.
Effects of View and Room Size on Window Size Preferences Made in Models
Authors: Butler Darrell L. , Steuerwald Brian L.
Published: March 2007

Window size preferences were studied in two experiments using a 1/12 scale model. In the first experiment, subjects viewed small-to medium-sized offices. The experiment showed that window preferences are affected by room size. Preferred window size is not a constant proportion of wall size. Rather, a larger proportion is preferred for smaller rooms. Second, the experiment showed that scenes perceived as more beautiful lead to larger preferred windows. Third, office work experience of subjects had no effect on preferences. Experiment 2, which incorporated several changes, confirmed all three of these findings. In addition, this experiment showed that window size preferences are also affected by the type of the room. Subjects viewing the same model preferred smaller windows for a computer work room than for an office.
Subjective Time Estimation in Altered Sensory Environments
Authors: Glicksohn Joseph
Published: March 2007

The influence of prior exposure to an altered sensory environment on subsequent subjective time estimation was the focus of the present study. It was hypothesized that the more varied the sensory environment (i.e., perceptual overload versus perceptual deprivation), the longer the time that is verbally estimated, and the shorter the time estimation obtained by the method of production. This hypothesis was supported for the data gathered by the latter method, but not by the former one, in a 3 x 4 factorial design employing 96 subjects, who were exposed to various combinations of auditory and visual stimulation. The conclusion drawn is that visual and auditory stimulation interact in their production of an altered sensory environment, and that the rate of functioning of the cognitive timer is environment dependent.
The Nature of Symbolic Beliefs and Environmental Behavior in a Rural Setting
Authors: Cary John
Published: March 2007

The correspondence between positively held beliefs about the environment and consistent environmental behavior is often tenuous. Many environmental beliefs have the characteristics of symbolic beliefs. Symbolic beliefs, reflecting what the belief objects represent for individual identity and values, provide social identification or self-expressive value functions for individuals. Symbolic beliefs are more abstract than instrumental beliefs and are less rooted in reality. In a research study of beliefs about environmental behavior related to rural land management, symbolic beliefs and instrumental beliefs were identified. Symbolic environmental beliefs were reflected in property holders claiming environmental benefits for behaviors primarily determined by more tangible, instrumental purposes. Decreasing proximity to the location of an environmental problem increased the instability of perceptions of the problem. It is likely that the more remote the belief object, the more symbolic the belief.
Units of Analysis, Measurement Theory, and Environmental Assessment
Authors: Richards James M.
Published: March 2007

The ecological fallacy is the error of interpreting variation among ecological entities as though it applies to individuals. It also is an error to interpret variation among individuals as though it applies to ecological entitles, and the theoretical and empirical ramifications of the latter error have been explored in a series of articles. A recent article by Levine commented extensively on this series and criticized some of its conclusions. The present article argues that Levine's article is incomplete in its application of measurement theory and that it overemphasizes an example that makes an inappropriate postulation about the distribution of universe scores. However, these disagreements are less important than areas of agreement. A substantial consensus exists about choice of units of analysis, usefulness of generalizability theory, and procedures for estimating the reliability of environmental measures.
The Activation of Environmental Norms
Authors: blamey Russell
Published: March 2007

This article considers how Schwartz's norm-activation model has been applied in the context of individual contributions to public goods, and how it might be extended to better reflect the full gamut of behavioral determinants in such situations. A review of literature in political economy, psychology, and sociology suggests that the translation of Schwartz's model from situations of isolated individual helping to the public goods context requires the role of organizations, policy initiatives, and notions of justice to be more explicitly incorporated within the model. Existing elements of the model also need to be broadened to encompass some of the unique characteristics of public good contributions, such as shared (as opposed to diffused) responsibility, and lower levels of individual decisiveness. A qualitative environmental case study illustrates some of the required extensions.
Type of Commute, Behavioral Aftereffects, and Cardiovascular Activity
Authors: White Steven M. , Rotton James
Published: March 2007

It was hypothesized that commuting would elevate blood pressure and lower frustration tolerance. This hypothesis was tested by assessing postcommute behavior of 168 paid volunteers in a true experiment whose factors were type of commute (drive vs. ride vs. control), direction of commute (North vs. South), gender (male vs. female), and choice (salient vs. nonsalient). Multivariate analyses of variance indicated that subjects who drove 48 km or rode a bus the same distance evidenced less frustration tolerance than noncommuting control subjects. Commuting also raised pulse and systolic blood pressure. Multivariate analyses of covariance were performed in an effort to identify physiological and emotional responses that might mediate relations between commuting and frustration tolerance. It is concluded that variables other than affect and arousal are responsible for behavioral aftereffects.
Preference for Macrojustice Versus Microjustice in Environmental Decisions
Authors: Clayton Susan
Published: March 2007

Both attitudes and behavior toward the environment are affected by the perceived justice of an environmental position. However, both sides in an environmental conflict will usually claim that justice favors their position. Preference for one outcome over another may thus depend on the type of justice that each outcome represents. The author argues that macrojustice principles, such as equality and responsibility, lend themselves more easily to an environmentalist position, whereas microjustice principles, such as equity and procedural justice, are more congenial to an antienvironmentalist position. In the present study, participants were presented with three scenarios in which conflicts had been resolved in either an antienvironmentalist or a proenvironmentalist way. The positions were presented either as promoting individual concerns or based on the concerns of the wider society. Overall, macrojustice arguments were more successful for proenvironmentalist decisions and microjustice arguments were more successful for antienvironmentalist decisions.
Knowledge Gap in AIDS Communication
Authors: Goswami Divakar , Melkote Srinivas `Raj'
Published: March 2007

The primary objective of this study was to investigate the relationship between socio-economic status (SES) and knowledge about AIDS among young adults in India. In the event that a knowledge gap existed, the study also sought to explore whether involvement variables such as cognitive involvement and information-seeking behaviour of respondents (relating to AIDS information) were able to bridge the knowledge gap between people of high and low socioeconomic status.
Public Service Radio Programming for Minority Language Audience(s) in a Competitive Market
Authors: Moring Tom , Salmi Jussi
Published: March 2007

With the arrival of commercial radio, attracting a younger audience, it becomes a challenge for minority radio stations to keep their audiences. The size of the minority, its location with respect to state borders, its dispersion into the majority population and the strength of the commercial and public service broadcasters in the area shape the possibilities for commercially based radio services. The focus of this study is on the recent development in radio services for the Swedish-speaking minority in Finland. The article concludes that if competitive programming is available in their own language, even bilingual speakers who form local minorities in regions with a highly competitive radio market will seek to strengthen their cultural identification by using radio services in their mother tongue.
New and Old Media Access and Ownership in the Arab World
Authors: Gher Leo A. , Amin Hussein Y.
Published: March 2007

Traditional broadcast networks can no longer dominate the electronic media infrastructure of the world. Because of cyberspace technologies now being introduced globally, the international telecommunication community is in a state of reinventing itself, and the impact of these changes may indelibly alter the way humanity interacts and communicates in the future. At the forefront of the communications revolution is the Information Superhighway, which has one compelling characteristic not found in previous distribution systems - it crosses borders. This unique trait allows for a world where transnational exchange is not merely possible, but is unavoidable. Major questions arise from these developments, and must become the subject of research. In the 21st century, what effects will these developments have on emerging universal issues such as multinational diversity, cultural integrity, the demand for global programming, production and distribution and media access and ownership. This article examines the impact of the Information Superhighway on one strategic, international region, the Arab World. Using traditional, historical analysis and field study methodology, this article explores: (1) the current status of media access and ownership in the Arab World; (2) the perspectives for developing cyberspace infrastructures and technologies that support the Information Superhighway in the region; and (3) the economic and cultural ramifications of the Information Superhighway on Arabic societies in the coming millennium.
Teaching Old Dogs New Tricks
Authors: Tan Tay Keong , Heracleous Loizos
Published: March 2007

The authors employed a longitudinal in-depth action research method to explore the implementation of organizational learning in an Asian national police force. They aimed to get an interpretive, in-depth understanding of the related processes of transformational change, as well as the barriers to change, in a machine bureaucracy with entrenched structure and culture not ordinarily conducive to learning and adaptation. Second, they aimed to explore the applicability of universalist change management prescriptions in this context. The authors found several structural and cultural barriers to transformational change that were nevertheless being successfully contested through a bottom-up participative change process, the existence of change champions, experiences that challenged the prevailing culture, and change actions that were congruent with the organization’s authorizing environment. Second, they found that universalist change management prescriptions may not always be relevant because the nature, task, and culture of an organization influence what approaches are appropriate and applicable.
Toward Common Ground and Action on Repetitive Strain Injuries
Authors: Polanyi Michael
Published: March 2007

Numerous participatory approaches to action on complex issues have emerged in recent years. One approach, the Future Search conference, is said to build a shared vision and rapid action by diverse stakeholders. This article reports on a detailed qualitative analysis of a Future Search conference on repetitive strain injuries, an ambiguous, conflictridden, and systemic problem. The Future Search encouraged the expression of diverse perspectives and mapped a certain domain of common ground. It stimulated various kinds of action, enhanced stakeholder involvement and awareness, and increased commitment to multistakeholder dialogue and action. Several weaknesses of the Future Search model are identified. Specifically, this study suggests the need for more participant clarity about what is expected, a more solid framework to support follow-up action, greater explicitness about what constitutes common ground, and more time for common-ground building and action planning.
Letting “The System” Do the Work
Authors: Haines David W.
Published: March 2007

Review of a multiyear computerization project at a government agency reveals the ways in which technological changes both empower and vitiate the people and processes they are designed to improve. Although the transformation of this agency’s data-processing operations resulted in increased knowledge, productivity, and staff skills, the implementation of the changes affected different kinds of staff in distinct ways, particularly those who controlled the technology, those who used the technology to construct database tracking systems, and those who “consumed” the information provided in those data-bases. In particular, the technological changes engendered a greater visibility of work processes, thus sharply challenging the existing organizational hierarchy, which, in turn, undermined much of the potential of the changes.
Representation of Stress Concentration Factors for a Composite in Plane Strain*
Authors: Gerstner R.W. , Dundurs J.
Published: March 2007

When a composite body consisting of two isotropic and elastic phases is in a state of plane strain, the stresses induced by applied tractions show a reduced dependence on the elastic constants. Con sequently, the stress concentration factors can conveniently be rep resented and studied in the plane of the appropriate composite parameters.
The Influence of Stacking Sequence on Laminate Strength
Authors: Pagano N.J. , Pipes R. Byron
Published: March 2007

Based upon considerations relating to the nature of the inter laminar stresses in composite laminates, an approach is presented to predict the detailed stacking sequence of specific layer orientations which leads to optimum protection against delamination under uniaxial static and fatigue loadings. In particular, it is argued that the interlaminar normal stress, as well as the interlaminar shear stress, is instrumental in precipitating delamination and subsequent strength degradation. Correlation with existing experimental evidence of the stacking sequence phenomenon is presented.
Fracture Mechanics and the Time Dependent Strength of Adhesive Joints
Authors: Knauss W.G.
Published: March 2007

The strength of technical joints formed with (soft) polymeric ad hesives is discussed from the detailed viewpoint of fracture mechanics. A new approach to the analysis of technical joints has been attempted by considering the variety of complex modes by which fracture can progress in such joints. Particular attention has been given to separat ing the geometric and loading factors of a joint from strength charac teristics attributable entirely to the properties of the materials in volved. By drawing on the creep or relaxation behavior of the polymer and on the fracture energy of the bond interface, or of the adhesive, the time-dependence of the process is discussed in the absence of a corrosive atmosphere. Finally, analytic reasons and a criterion are given for the possible rate dependence of the failure path location along different interfaces of adherends and the adhesive.
Dynamic Mechanical Properties of Graphite-Epoxy and Carbon-Epoxy Composites
Authors: Hirai T. , Kline D.E.
Published: March 2007

Dynamic elastic moduli and damping of carbon- and graphite-filled epoxy composites have been measured over the temperature range of 85 to 300° K. The epoxy resin matrix was cured with diethylenetriamine. Dynamic elastic moduli increase with filler content in both cases; however, graphite powder is more effective than carbon powder in increasing the modulus. For the graphite composite, experimental data agree with Wu's equation for disk-shaped filler particles with a modulus of 56 × 1010 dyne/cm2. For the carbon composite, experimental data cannot be effec tively compared to any theoretical model, probably because the carbon powder is composed of agglomerated particles. The effect of voids on the dynamic modulus of a particulate composite is also discussed. The β damping peak (∼ 250° K) does not change in its intensity with filler con tent, while the intensity of the γ peak (∼ 150°K) is decreased as the amount of filler is increased. The relation between the filler content and the intensity of the β peak suggests that damping in the composites in cludes a component due to friction at the interface between the filler and matrix. The decrease in the y peak with filler content may be explained by interaction between the filler surface and unreacted epoxides
Nonlinear Behavior of Laminated Composites
Authors: Hahn H.T.
Published: March 2007

This paper extends the nonlinear behavior of unidirectional laminae of Reference [1] to that of laminated composites. A comparison between the theory and experimental results is shown through the analysis of uniaxial tension behavior of various laminates. The effect on buckling stress owing to nonlinearity is illustrated for a ±45° angle-ply laminate with simply- supported edges.
Optimal Design of Anisotropic (Fiber-Reinforced) Flywheels
Authors: Christensen Richard M. , Wu Edward M.
Published: March 2007

An analysis is given of the kinetic energy storage capacity of anisotropic flywheels. Using a uniform strain failure criteria, the optimal shapes of flywheels are determined as a function of the degree of anisotropy. Within this spectrum of shapes, practical design considerations are shown to favor the case where there is equal reinforcement in the radial and circumferen tial directions. Comparisons are made between the present solid-wheel-type design and the ring design.
Mechanical Properties of Chromium Carbide Coated Graphite Fibers
Authors: Miyase A. , Piekarski K.
Published: March 2007

Graphite fibers (Fortafil 6T) have been coated with chromium carbides by diffusing chromium to fibers through a solid layer of copper. Tensile strength and the elastic modulus of coated fibers were measured as a func tion of the thickness of the coating. It was found that mechanical proper ties deteriorate with increased thickness of chromium carbides. It is be lieved to be related to the pre-existing Griffith cracks and possible forma tion of new cracks in the coating during tensile tests of individual fibers.
The Effect of Temperature and Moisture Content on the Flexural Response of Kevlar/Epoxy Laminates: Part I. [0/90] Filament Orientation*
Authors: Allred Ronald E.
Published: March 2007

This study examines the effects of moisture and temperature on the flexural response of [0/90] Kevlar 49 fabric-reinforced epoxy laminates. Two high temperature (190°C) cure commercially available epoxies, Narmco 5208 and Ferro CE-9000, were used as matrix materials. Results indicate that the mechanical properties of Kevlar 49/epoxy laminates are temperature dependent over the range -55°C to 150°C. The addition of moisture magnifies temperature sensitivity. At 150°C and near saturation moisture content (5 weight percent), a strength loss of 60-70 percent and an effective stiffness loss of 40 percent from dry, room temperature values are measured. At 21°C, saturated specimens are found to be 35-40 per cent weaker than dry material. At low temperature (-55°C), strengths increase with the addition of moisture. Over the range of conditions tested, failure was not catastrophic, but was characterized by a loss in load carry ing capacity. Microscopic examination of failure modes indicates that flexural strength is determined by the ease with which filaments compres sively buckle. These results indicate that care must be taken when design ing with Kevlar-reinforced composites for use at elevated temperatures after exposure to moist environments. An accurate prediction of the ex pected composite moisture content and service temperature is important to the design process.
Stresses around Rectangular Holes in Orthotropic Plates
Authors: de Jong Theo
Published: March 2007

This paper deals with stresses around rectangular and square openings with rounded corners in orthotropic plates. A variant on an approximative solution indicated by Lekhnitskii was used. Numerical results are presented for three different holes in seven different laminates of carbon fiber reinforced plastic.
Detection of Moisture in Graphite/Epoxy Laminates by X-Ray Diffraction
Authors: Predecki Paul , Barrett Charles S.
Published: March 2007

The objective of this study was to determine if X-ray diffraction could be utilized to detect moisture non-destructively in graphite/epoxy laminates. CuKα1 X-rays were diffracted from 333 + 511 planes of Al particles em bedded between the first and second plies of [0 ± 60] s lamiantes during layup. Diffracted peak positions were quite sensitive to environmental moisture, decreasing 0.624 ° ± .015 °2θ on going from a completely dry to a completely wet state at 50°C. The changes were reversible. Correlations be tween in-plane, residual particle strains and both average and local moisture content of the laminate were obtained. Annealing effects were investigated.
Central Ductile Crack in an Orthotropic Strip of Finite Width
Authors: Tsai Y.M.
Published: March 2007

The effects of the material anisotropy on the size of the crack tip inelastic zone and the crack shape are investiaged for a Dugdale crack in an or thotropic strip with finite width. Using the techniques of Fourier transforms, the solutions are obtained and largely written in terms of the sum and dif ference of the characteristic roots, so that the results can easily be seen as real value functions for both real and complex roots.
Surface Damage of Sheet Molding Compound Panels Subject to a Point Impact Loading
Authors: Khetan Raghunath P. , Chang David C.
Published: March 2007

The point impact damage characteristics of panels made of chopped-glass-fiber- reinforced sheet molding compounds are evaluated qualitatively and quantitatively. In stead of the traditionally used dent depth, the surface damage area is identified as the primary parameter to characterize the impact damage of the SMC panels. Three techniques—radiographic, ultrasonic and crack enhancement—are used to measure the damage areas. The relative merits of the three methods are discussed.
Three-Dimensional Curing Stresses in Symmetric Cross-Ply Laminates with Temperature-Dependent Properties
Authors: Griffin O. Hayden
Published: March 2007

A fully three-dimensional finite element analysis of curing stresses in cross-ply boron/epoxy composite laminates is presented. Comparisons are made between constant and temperature- dependent material properties and a constitutive model which includes the coupling between stress and temperature dependence of material properties. Also examined is the error introduced by the common assumption of equality of all shear moduli (G12, G13, G23) and certain Poisson's ratios (ν 12, ν13, ν23). Interlaminar stresses near the laminate midplane and 0/90 interface are presented, including effects which occur near the free corner of the laminate. Differences in the three thermal expansion models are found to be significant for the boron/epoxy system in some stress terms and negligible in others. The errors introduced by the coefficient equality assump tions are found to be small. Omission of the stress-thermal expansion interaction term is found to result in substantial underestimates of curing stresses. This is in agreement with the results of previous investigators which included the coupling term in a lamination theory model.
Failure of Composite Laminates Containing Pin Loaded Holes—Method of Solution
Authors: Chang Fu-Kuo , Scott Richard A. , Springer George S.
Published: March 2007

A method is presented for predicting the failure strength and the failure mode of fiber reinforced composite laminates containing one or two pin loaded holes. The method involves two steps. First, the stress distribution in the laminate is calculated by the use of a finite element method. Second, the failure load and failure mode are predicted by means of a proposed failure hypothesis together with the Yamada-Sun failure criterion. A computer code was developed which can be used to calculate the maximum load and the mode of failure of laminates with different ply orientations, different material properties, and different geometries. Tests were also conducted measuring the failure strengths and failure modes of Fiberite T300/1034-C laminates containing a pin-loaded hole or two pin-loaded holes in parallel or in series. Com parisons were made between the data and the results of the model. Good agreement was found between the analytical and the experimental results.
The Strength Distribution of 90° Plies in 0/90/0 Graphite-Epoxy Laminates
Authors: Peters P.W.M.
Published: March 2007

Graphite epoxy cross ply laminates show multiple cracking in the 90 ° ply before final rupture occurs. By the aid of a piezo-electric load cell crack formation was measured as a function of the applied load in (02/902)s, (02/903)s and (02/906) s laminates. With these experimental results and a shear lag analysis, to account for the non-homogeneous stress distribution in cracked 90° plies, it was possible to estimate the Weibull strength distribution of the respective 90° ply. it was found that at decreasing 90° ply thickness the shape factor increases. This can be attributed to a suppression of defect growth close to the 90°/0° interface. Because of the changing shape parameter at decreasing ply thickness a description of the thickness effect by a Weibull shape parameter is im possible.
Composites Analysis by Fractional Moiré Fringe System
Authors: Voloshin Arkady S. , Burger Christian P. , Rowlands Robert E.
Published: March 2007

There is a need for a high resolution method for the full field measurement of sur face displacements and strain on FRM components. This paper describes a technique for utilizing low density moiré gratings to obtain high resolution fringe data through the use of digital image analysis procedures. The technique is illustrated by determining displacement and strain data in the neighborhood of a central hole in a composite ten sile plate.
Notched Strength Prediction and Design of Laminated Composites Under In-Plane Loadings
Authors: Tan S.C.
Published: March 2007

Two models based on the first-ply-failure stresses of notched and unnotched laminates are developed for the strength prediction of composite laminates containing an opening under in-plane loadings. Comparisons show that these models provide good agreement with experimental data for quasi-isotropic and orthotropic laminates containing a circular hole or a center crack. In conjunction with these models, a ranking method is applied for the laminate designs that is found reliable and very useful.
The Tensile Behavior of Intraply Hybrid Composites II: Micromechanical Model
Authors: Fariborz S.J. , Harlow D.G.
Published: March 2007

The standard shear-lag model is modified to allow for the determination of the stress concentration factors for any unidirectional intraply hybrid composite with random as well as deterministic arrangements of the filaments. Utilizing this micromechanical model in conjunction with the chain-of-bundles probability model, hybrids with different volume ratios of the constituents are analyzed. The method of analysis is the numerical Monte Carlo simulation technique. The well known "hybrid effect" for strains is confirmed. The Weibull distribution function is observed to be a good representation of the hybrid break ing strain. The estimated ultimate breaking strains show a significant improvement over previously cited results, and they appear to be more characteristic of experimental obser vations.
An Investigation of the Mechanical Properties of Improved Carbon Fibre Composite Materials
Authors: Curtis P.T.
Published: March 2007

A wide range of mechanical properties, involving tension, compression, shear, notch and impact tests, have been performed on twelve carbon fibre composite materials. The materials tested ranged from standard carbon fibre reinforced epoxy systems to high strain and intermediate modulus carbon fibres with toughened epoxy, bismaleimide and thermo plastic matrices.

The actual improvement in mechanical properties of composites attainable through the use of these improved materials depended on both the type of fibre and resin and their compatibility in the composite, as well as the interface between them. Thus improved materials should be selected on their overall system performance rather than individual fibre and resin behaviour.

None of the improved materials had increased compressive strength, particularly in the critical hot/wet and notched case, although most proved to be tougher than the standard materials.

The thermoplastic based system had the greatest resistance to impact, but the properties of the ±45 laminates appeared to show some sensitivity to the rate of cooling after mould ing.

Advice on the selection of materials is given and recommendations are made of how further improvements in composite performance might be achieved.
The Effect of Resin Formulation on the Surface Appearance of Glass Fiber Reinforced Polymers
Authors: Kia Hamid G.
Published: March 2007

This paper is concerned with the effect of resin formulation on the magnitude of fiber readout for polymers reinforced with continuous glass fiber mats. The observed fiber readout is the deformation of the surface with a pattern similar to the underlying fibers. In our previous studies, it was established that one of the main factors responsible for fiber readout is the coefficient of linear thermal expansion (CLTE) of the resin in the direction normal to the cosmetic surface. In the current study, the differential thermal contraction (Δ∈) between the resin and the glass fibers, a factor directly relatable to the magnitude of fiber readout, has been investigated. This direct relationship was examined by comparing the computed values for the Δ∈ with the measured magnitude of fiber readout for rein forced polyurethanes (filled with milled glass or hollow glass spheres) and polyesters (filled with calcium carbonate). For all experiments, the predicted values for (Δ∈) were found to be consistent with the experimental measurements for fiber readout.
A 36 DOF Symmetrically Laminated Triangular Element with Shear Deformation and Rotatory Inertia
Authors: Chen Alex T. , Yang T.Y.
Published: March 2007

An approach is presented in the formulation of a 36 d.o.f. symmetrically laminated composite triangular plate element including the enect of shear deformation for free vibra tion analysis. The strain energy of plates can be expressed as the sum of the flexural and shear strain energies. The total displacement is expressed as the sum of the displacement due to bending and that due to shear deformation. Thus only the displacement due to bend ing appear in the flexural strain energy and the displacement due to shear deformation ap pear in the shear strain energy. Numerical results for natural frequencies for a range of dif ferent isotropic, orthotropic and anisotropic plates with various thickness-to-length ratios are obtained and compared with various alternative solutions available in the literature to demonstrate the valid range of applicability of this approach for the free vibration of plates with the effect of shear deformation.
Composite Materials: Theory vs. Experiment
Authors: Laws N.
Published: March 2007

Some experimental data by Richard [1] has been used by previous authors to validate models for the prediction of effective moduli of composites. It is shown that this data lies outside the range specified by the Hashin-Shtrikman bounds.
Detection of Damage in Composite Materials by Thermo-Acoustic Emission Measurement
Authors: Sato Norio , Kurauchi Toshio , Kamigaito Osami
Published: March 2007

Characteristic acoustic emission behavior was observed when a composite was subject to a thermal cycle (thermo-acoustic emission). A lot of emission was observed in the ther mal cycle for a composite which had damage induced by mechanical loading. On the other hand, the emission was hardly observed for a sound composite in the thermal cycle. The occurrence of the emission was restricted only to the composite with damage. Further more, the emission activity depended on the degree of the damage. The emission is con sidered to be generated due to the friction of the crack faces by the thermal loading. The thermo-acoustic emission measurement is considered to be anticipated as nondestructive evaluation for composite materials.
Photoelastic Study of Epoxy Resin/Graphite Fiber Load Transfer*
Authors: Ashbee K.H.G. , Ashbee Elizabeth
Published: March 2007

The physical techniques of polarising microscopy, including the measurement of small (<0.1λ) optical retardations, have been used to investigate elastic fields adjacent to short (1-3 mm length) graphite fibers in epoxy resin composites. In as-cured specimens, i.e., in specimens self-stressed on account of resin cure shrinkage, the elastic field in the neighbourhood of fiber ends is, for surface treated fibers, characteristically different from that for untreated fibers and reflects the more efficient load transfer expected of the former. The regions of highest shear stress, defining the limits along the fiber length between which load transfer is effective, are seen to move inwards, towards each other, during hot (80°C) water uptake. This is interpreted as the propagation of "end cracks" and the con stant rate at which it occurs is shown to be dimensionally compatable with a diffusion con trolled mechanism. Also during water uptake, isolated pockets of interfacial pressure develop and these are attributed to water of crystallization at sodium carbonate impurity inclusions in the fiber surface. The magnitude of this pressure has been estimated from its temperature coefficient to be of the order of 200 bar (20 MPa) at ambient tem peratures.
A Mechanical/Thermal Analysis of Prestressed Composite Laminates
Authors: Tuttle M.E.
Published: March 2007

The effects of fiber preloads on the ply stresses induced within continuous-fiber compos ite laminates are considered. A micromechanics analysis based primarily upon the rule-of- mixtures is used to predict the fiber and matrix stresses within a single prestressed ply. These results are integrated with classical lamination theory, allowing calculation of the ply stresses for prestressed composite laminates. The analysis indicates that prestressing will dramatically influence the ply stresses induced within composite laminates.
Contour-Plot Simulation of Vibrational and Buckling Mode Shapes of Composite Plates
Authors: Pao Y.C. , Peterson Kurt A.
Published: March 2007

In this paper, the use of contour plotting to display the mode shapes of free vibration and buckling of laminate plates is reported. Contour plotting is shown to be superior to three- dimensional hidden-line plots. In addition to easy distinction of the nodal and peak-valley lines and isometric contours of equal elevations of the deformed mid-plane of the plate, contour plotting exhibits the fiber direction in the dominating layers of the laminate plate. Although only square laminate plates symmetric about their respective mid-planes and fully clamped are discussed, application of the contour plotting method can be extended for other types of laminate plates and boundary conditions.
Inference for Strength Distributions of Brittle Fibers under Increasing Failure Rate
Authors: Durham S.D. , Lynch J.D. , Padgett W.J.
Published: March 2007

A different approach to the problem of estimating the strength distribution of brittle fibers is proposed. The procedure assumes a Poisson flaw model, but rather than presum ing a particular functional form, it is assumed that the probability distribution of strength has an increasing failure rate (IFR). The maximum likelihood estimate of the fiber strength distribution is obtained within the class of all distributions with the IFR property, yielding a continuous distribution estimate which is a good fit to fiber tensile strength data, typically fitting much better than the usual Weibull model. The method is illustrated with carbon fiber data.
Simplified Design Techniques for Laminated Cylindrical Pressure Vessels under Stiffness and Strength Constraints
Authors: Fukunaga Hisao , Chou Tsu-Wei
Published: March 2007

This paper treats the optimum design of graphite/epoxy laminated composite cylindrical pressure vessels under stiffness and strength constraints based upon the membrane theory. Stiffness constraints are specified as strain conditions both in the axial and circumferential directions. Tsai-Wu failure criterion is used for determining a first-ply-failure strength. The stiffness and strength characteristics of the laminate are discussed based upon the concept of lamination parameters. For small values of allowable axial and circumferential strains, the strain (or stiffness) condition is critical, while for large values of allowable strains the strength condition is critical. The optimal laminate configurations are determined for the various kinds of strain and strength constraints.
Fracture Resistance of a TiB2 Particle/SiC Matrix Composite at Elevated Temperature
Authors: Jenkins Michael G. , Salem Jonathan A. , Seshadri Srinivasa G.
Published: March 2007

The fracture resistance of a commercial TiB2 particle/SiC matrix composite was evalu ated at temperatures ranging from 20 to 1400°C. A laser interferometric strain gage (LISG) was used to continuously monitor the crack mouth opening displacement (CMOD) of the chevron-notched and straight-notched, three-point bend specimens used. Crack growth resistance curves (R-curves) were determined from the load versus displacement curves and displacement calibrations. Fracture toughness, work-of-fracture, and R-curve levels were found to decrease with increasing temperature. Microstructure, fracture sur face, and oxidation coat were examined to explain the fracture behavior.
Plate Wave Propagation in Transversely Isotropic Materials
Authors: Kline R.A. , Doroudian M.M. , Hsiao C.P.
Published: March 2007

In this work, the modes of plate wave propagation in a fiber reinforced com posite (assumed to be transversely isotropic) were investigated. The waves were modeled as harmonic plane waves propagating in the plane of an infinite plate whose bounding sur faces were assumed to be stress free. A numerical analysis procedure was developed to calculate the dispersion relationships for plate waves propagating in arbitrary directions in the plate. Particle displacements and stress distributions were calculated for several im portant propagation modes. Possible applications to nondestructive testing of composites are discussed.
Generic Buckling and Bending Behavior of Initially Stressed Antisymmetric Cross-Ply Thick Laminates
Authors: Yang I.- Horng
Published: March 2007

Equations of motion for antisymmetric cross-ply laminates in a general state of nonuniform initial stress, where the effects of transverse shear and rotary inertia are included, are derived by the virtual work theorem. The equations are adjusted to a generic form by using appropriate transformations. With the help of using the transforma tions, introducing generalized parameters, and employing a similarity parameter, compre hensive solutions are found to this problem; hence, the curves presented in the text are generic rather than specific. The thick plate equations are solved for simply-supported rec tangular antisymmetric cross-ply laminated plates in a state of uniform compressive stress plus a uniform bending stress with both acting in the same direction. The results of the reduced set of equations agree with those obtained by previous investigators.
A Model for the Prediction of Compressive Strength Reduction of Composite Laminates with Molded-In Holes
Authors: Nejhad M.N. Ghasemi , Chou Tsu-Wei
Published: March 2007

An Equivalent Radius Model (ERM) for the prediction of compressive strength reduction in laminates with molded-in holes is presented. This model replaces a molded-in hole panel by an equivalent drilled hole panel with the same notched strength. As a result, the ERM relies on an accurate stress failure criterion for drilled hole panels. The experimental results obtained from woven carbon fiber/epoxy laminates with molded- in and drilled holes indicate that the proposed model satisfactorily simulates the observed strength behavior. It is believed that the simplicity of the present model coupled with its accuracy and generality makes it of practical value to the design engineers.
Tensile Impact Tests of AS4/3501-6 and S2/3501-6 Unidirectional Composites and the 3501-6 Epoxy Matrix
Authors: Adams Donald F. , Adams Larry G.
Published: March 2007

Tensile impact testing was performed on both AS4 carbon/3501-6 epoxy and S2 glass/3501-6 epoxy unidirectional composites, and the neat (unreinforced) Hercules 3501-6 epoxy. Static tensile tests were also performed. The impact testing was conducted using an apparatus designed and fabricated specifically for composite materials. Impact test results indicated relatively little influence of varying the impact velocity from static to 5 m/s, a range of practical interest in design.